Statistical Model for the Nucleon Structure Functions
Bhalerao, R. S.
1996-01-01
A phenomenological model for the nucleon structure functions is presented. Visualising the nucleon as a cavity filled with parton gas in equilibrium and parametrizing the effects due to the finiteness of the nucleon volume, we obtain a good fit to the data on the structure function $F_2^p$. The model then successfully predicts other unpolarized structure function data.
Polarized structure functions of nucleons and nuclei
Bentz, W.; Clot, I. C.; Ito, T.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia); Yazaki, K
2007-01-01
We determine the quark distributions and structure functions for both unpolarized and polarized DIS of leptons on nucleons and nuclei. The scalar and vector mean fields in the nucleus modify the motion of the quarks inside the nucleons. By taking into account this medium modification, we are able to reproduce the experimental data on the unpolarized EMC effect, and to make predictions for the polarized EMC effect. We discuss examples of nuclei where the polarized EMC effect ...
Experimental results on polarized nucleon structure functions
Energy Technology Data Exchange (ETDEWEB)
Ketel, T.J. [Department of Physics and Astronomy, Free University Amsterdam (Netherlands); Spin Muon Collaboration at CERN
1998-05-01
Experimental results of deep inelastic scattering of polarized leptons from polarized target nucleons are reviewed. Accurate values of the spin dependent structure function g{sub 1} (x) were obtained in experiments covering a large kinematic range. The combination of all experimental results confirms the validity of the Bjorken sum rule. (author) 14 refs, 7 figs, 2 tabs
Phenomenological study of the nucleon structure functions
International Nuclear Information System (INIS)
This thesis is devoted to the study of the deep inelastic scattering. Its purpose is the development of phenomenological models describing experimental results on unpolarized (F2) and polarized (g1) nucleon structure functions in the wide range of the kinematical domain. Special attention is paid to the small-x behaviour of F2 and to the link between deep inelastic scattering and photoproduction process. The investigation of the Pomeron in deep inelastic scattering shows that one single Pomeron compatible with the Froissard-Martin limit can account for all the present HERA data. A phenomenological model of the proton structure function is developed, based on a two-component structure including various features expected from both perturbative quantum chromodynamics and non perturbative Regge theory. A link with the photoproduction process is provided. A detailed analysis of the perturbative components, based on the Gribov-Lipatov-Altarelli-Parisi evolution equations is presented. Taking into account the different parton distribution, this approach allows to describe data on proton and neutron structure functions, on deep inelastic neutrino scattering, and to reproduce the gluons distribution extracted by the ZEUS collaboration. The model is applied to the polarized deep inelastic scattering and the axial anomaly effect appearing both in the description of results on the spin dependent structure functions gp,n,d and in the interpretation of the nucleon spin structure is discussed. (J.S.). 260 refs., 34 figs., 8 tabs., 6 appends
Nucleon Structure Functions within a Chiral Soliton Model
Gamberg, L P; Weigel, H
1997-01-01
We study nucleon structure functions within the bosonized Nambu--Jona--Lasinio model where the nucleon emerges as a chiral soliton. We discuss the model predictions on the Gottfried sum rule for electron--nucleon scattering. A comparison with a low--scale parametrization shows that the model reproduces the gross features of the empirical structure functions. We also compute the leading twist contributions of the polarized structure functions $g_{1}(x)$ and $g_{2}(x)$ in this model. We compare the model predictions on these structure functions with data from the E143 experiment by GLAP evolving them appropriately.
Nucleon structure functions with domain wall fermions
Orginos, K; Ohta, S; Orginos, Kostas; Blum, Thomas; Ohta, Shigemi
2006-01-01
We present a quenched lattice QCD calculation of the first few moments of the polarized and un-polarized structure functions of the nucleon. Our calculations are done using domain wall fermions and the DBW2 gauge action with inverse lattice spacing ~1.3GeV, physical volume approximatelly (2.4 fm)^3, and light quark masses down to about 1/4 the strange quark mass. Values of the individual moments are found to be significantly larger than experiment, as in past lattice calculations, but interestingly the chiral symmetry of domain wall fermions allows for a precise determination of the ratio of the flavor non-singlet momentum fraction to the helicity distribution, which is in very good agreement with experiment. We discuss the implications of this result. Next, we show that the chiral symmetry of domain wall fermions is useful in eliminating mixing of power divergent lower dimensional operators with twist-3 operators. Finally, we find the isovector tensor charge at renormalization scale 2 GeV in the MS bar schem...
Nucleon structure functions at small $x$ via holographic Pomeron exchange
Watanabe, Akira
2015-01-01
The analysis on nucleon structure functions at small Bjorken $x$ in the framework of holographic QCD is presented. In the model setup, the complicated nonperturbative interaction between the virtual photon and the target nucleon is described via the Pomeron exchange, which corresponds to the reggeized graviton exchange in the AdS space. We show that our calculations for both $F_2$ and $F_L$ structure functions are in agreement with the experimental data measured at HERA.
Spin Dependent Structure Functions of Nucleons and Nuclei
Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
1994-01-01
We review recent progress in the understanding of the spin structure of the nucleon. For the free nucleon the issues addressed include the status of the Bjorken and Ellis-Jaffe sum-rules and the role of the axial anomaly. We outline recent work connecting the quark models familiar from hadron spectroscopy to the spin and flavour dependence of the parton distributions. Finally we review the current understanding of nuclear spin structure functions and particularly the extract...
Nucleon axial charge and structure functions with domain wall fermions
Ohta, S; Ohta, Shigemi; Orginos, Kostas
2003-01-01
We report the current status of RBCK calculations on nucleon structure with both quenched and unquenched lattice QCD. The combination of domain wall fermions and DBW2 gauge action works well for isovector vector and axial charges, and moments of structure functions _q, d_1, and _{\\delta q}.
Energy Technology Data Exchange (ETDEWEB)
Bertini, M.
1995-05-12
This thesis is devoted to the study of the deep inelastic scattering. Its purpose is the development of phenomenological models describing experimental results on unpolarized (F{sub 2}) and polarized (g{sub 1}) nucleon structure functions in the wide range of the kinematical domain. Special attention is paid to the small-x behaviour of F{sub 2} and to the link between deep inelastic scattering and photoproduction process. The investigation of the Pomeron in deep inelastic scattering shows that one single Pomeron compatible with the Froissard-Martin limit can account for all the present HERA data. A phenomenological model of the proton structure function is developed, based on a two-component structure including various features expected from both perturbative quantum chromodynamics and non perturbative Regge theory. A link with the photoproduction process is provided. A detailed analysis of the perturbative components, based on the Gribov-Lipatov-Altarelli-Parisi evolution equations is presented. Taking into account the different parton distribution, this approach allows to describe data on proton and neutron structure functions, on deep inelastic neutrino scattering, and to reproduce the gluons distribution extracted by the ZEUS collaboration. The model is applied to the polarized deep inelastic scattering and the axial anomaly effect appearing both in the description of results on the spin dependent structure functions g{sup p,n,d} and in the interpretation of the nucleon spin structure is discussed. (J.S.). 260 refs., 34 figs., 8 tabs., 6 appends.
Truncated Moment Analysis of Nucleon Structure Functions
Energy Technology Data Exchange (ETDEWEB)
A. Psaker; W. Melnitchouk; M. E. Christy; C. E. Keppel
2007-11-16
We employ a novel new approach using "truncated" moments, or integrals of structure functions over restricted regions of x, to study local quark-hadron duality, and the degree to which individual resonance regions are dominated by leading twists. Because truncated moments obey the same Q^2 evolution equations as the leading twist parton distributions, this approach makes possible for the first time a description of resonance region data and the phenomenon of quark-hadron duality directly from QCD.
International Nuclear Information System (INIS)
In the nuclear medium, there are the non-nucleonic components. The leak-out partons, which form some colour-singlet parton clusters, are the origin of the non-nucleonic components. Meanwhile, the small x partons become co-used by several nucleons because the partons' longitudinal size extends over more than one nucleon. The nucleon effective mass can be successfully used as the only free parameter to adjust the structure function ratios recently measured by NMC
Relation between nuclear and nucleon structure functions and their moments
International Nuclear Information System (INIS)
Calculations of nuclear structure functions (SFs) Fk=1,2A(x,Q2) routinely exploit a generalized convolution, involving the SFs for nucleons FkN and the linking SF fPN,A of a fictitious nucleus, composed of point particles, with the latter usually expressed in terms of hadronic degrees of freedom. For finite Q2 the approach seemed to be lacking a solid justification and the same is the case for recently proposed, effective nuclear parton distribution functions, which exactly reproduce the above-mentioned hadronically computed FkA. Many years ago Jaffe and West proved the above convolution in the plane-wave impulse approximation for the nuclear components in the convolution. We extend the above proof to include classes of nuclear final-state interactions. One and the same function appears to relate parton distribution functions in nuclei and nucleons and SFs for nuclear targets and for nucleons. That relation is the previously conjectured one, with an entirely different interpretation of fPN,A. We conclude with an extensive analysis of moments of nuclear SFs based on the generalized convolution. Characteristics of those moments are shown to be quite similar to those for a nucleon. We conclude that the above is evidence of asymptotic freedom of a nucleon in a medium and not the same for a composite nucleus
Nuclear effects in F_3 structure function of nucleon
Athar, M Sajjad; Vacas, M J Vicente
2007-01-01
We study nuclear effects in the $F^A_3(x)$ structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio $R(x,Q^2)=\\frac{F^A_3(x,Q^2)}{AF^N_3(x, Q^2)}$ and the Gross-Llewellyn Smith(GLS) integral $G(x,Q^2)=\\int_x^1 dx F^A_3(x,Q^2)$ in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data.
Nuclear effects in F3 structure function of nucleon
International Nuclear Information System (INIS)
We study nuclear effects in the F3A(x) structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio R(x,Q2)=(F3A(x,Q2))/(AF3N(x,Q2)) and the Gross-Llewellyn Smith (GLS) integral G(x,Q2)=?x1dxF3A(x,Q2) in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data
Collinear Structure Functions of the Nucleon: Status and Future
International Nuclear Information System (INIS)
While our ultimate goal is a complete three-dimensional picture of the nucleon in terms of its fundamental constituents, there are still important lessons to be learned about its ''one-dimensional'' collinear parton distribution functions (PDFs) like f1(x) and g1(x). There are rigorous proofs for factorization and universality (process independence) which make these PDFs fundamental. They also appear as limits of Generalized Parton Distributions (GPD) and as integrals of transverse momentum-dependent (TMD) parton distribution functions. Experimentally, the unpolarized structure functions F1(x,Q2), F2(x,Q2) have been studied over a huge kinematic range in both variables. Information on the polarized structure functions g1(x,Q2), g2(x,Q2) is somewhat more limited, both in kinematics and in statistical precision. In both cases, much less is known about the neutron than the proton, due to the absence of a free neutron target. Accessing these structure functions at large x (where valence quarks dominate) has been challenging due to the high luminosity and the high resolution required. Finally, much information can be extracted from studying higher twist contributions to these structure functions and the connection between the DIS limit and the region where nucleon resonance excitation dominates. In my talk, I will present an overview of recent experimental results (with special emphasis on the valence region and the transition from quark to hadronic degrees of freedom). I will also give an outlook on the next round of experiments coming online with the energy-upgraded Jefferson Lab electron beam, and future projects like the Electron Ion Collider
Polarized Structure Function of Nucleon and Orbital Angular Momentum
Arash, Firooz; Taghavi-Shahri, Fatemeh
2007-06-01
We have utilized the concept of valon model to calculate the spin structure function of a constituent quark. This structure is universal and arises from perturbative dressing of a valence quark in QCD. With a convolution method the polarized structure functions of proton, neutron, and deuteron are obtained. Our results agree rather well with all available experimental data. It suggests that the sea quark contribution to the spin of nucleon is consistent with zero, in agreement with HERMES data. It also reveals that while the total quark contribution to the spin of a constituent quark, or valon, is almost constant and equal to one, the gluon contribution grows with the increase of Q2, and hence, requiring a sizable negative angular momentum contribution. This component, as well as singlet and non-singlet parts are calculated in the Next-to-Leading order in QCD. We speculate that the gluon contribution to the spin of proton is in the order of 50%. Furthermore, we have determined the polarized valon distribution in a nucleon.
Convolution model for the structure functions of the nucleon
Keppler, J
1994-01-01
We start from an MIT-bag model calculation which provides information about the constituent quark distributions in the nucleon. The constituent quarks, however, are themselves considered as complex objects whose partonic substructure is resolved in deep inelastic scattering. This gives rise to structure functions of the constituent quarks which, in the unpolarized case, are fitted to data at a fixed scale employing three model parameters. Using Q^{2}--evolution equations the data are also well described at other scales. For the spin\\-dependent struc\\-ture func\\-tions g_{1}^{p,n} we additionally have to introduce polar\\-izat\\-ion functions for valence and sea quarks which are determined by exploiting the x--dependence of the available proton data only. A negatively polarized sea in the range x\\geq 0.01 is suggested. We are then capable of predicting the shape of the neutron structure function g_{1}^{n} which turns out to be in good agreement with experiment. Finally we present an estimate for the trans\\-versel...
Detailed Measurements of Structure Functions from Nucleons and Nuclei
2002-01-01
The experiment will study deep inelastic muon nucleon scattering in a wide range of Q|2~(1-200 (GeV/c)|2) and x~(0.005-0.75). The main aims of the experiment are: \\item a)~~~~Detailed measurements of the nuclear dependence of the structure function F^2|A, of R~=~@s^L/@s^T and of the cross-section for J/@y production. They will provide a basis for the understanding of the EMC effect: the modification of quark and gluon distributions due to the nuclear environment. \\item b)~~~~A simultaneous high luminosity measurement of the structure function F^2 on hydrogen and deuterium. This will provide substantially improved accuracy in the knowledge of the neutron structure function F^2|n, of F^2|p-F^2|n and F^2|n/F^2|p and their Q|2 dependence. Furthermore, the data will allow a determination of the strong coupling constant @a^s(Q|2) with reduced experimental and theoretical uncertainties as well as of the ratio of the down to up quark distributions in the valence region. Due to the large x range covered by the experim...
Neutrinos and nucleon structure
International Nuclear Information System (INIS)
The study of neutrino interactions in matter is yielding a wealth of information on the form factors and structure functions of the nucleon. These data allow tests of models of nucleon structure and of dynamical theories of quarks and gluons. We attempt a critical appraisal of recent facts and their impact on our theoretical understanding. (orig.)
Measurement of the nucleon structure function using high energy muons
International Nuclear Information System (INIS)
We have measured the inclusive deep inelastic scattering of muons on nucleons in iron using beams of 93 and 215 GeV muons. To perform this measurement, we have built and operated the Multimuon Spectrometer (MMS) in the muon beam at Fermilab. The MMS is a magnetized iron target/spectrometer/calorimeter which provides 5.61 kg/cm2 of target, 9% momentum resolution on scattered muons, and a direct measure of total hadronic energy with resolution sigma/sub nu/ = 1.4?nu(GeV). In the distributed target, the average beam energies at the interaction are 88.0 and 209 GeV. Using the known form of the radiatively-corrected electromagnetic cross section, we extract the structure function F2(x,Q2) with a typical precision of 2% over the range 5 2 2/c2. We compare our measurements to the predictions of lowest order quantum chromodynamics (QCD) and find a best fit value of the QCD scale parameter ?/sub LO/ = 230 +- 40/sup stat/ +- 80/sup syst/ MeV/c, assuming R = 0 and without applying Fermi motion corrections. Comparing the cross sections at the two beam energies, we measure R = -0.06 +- 0.06/sup stat/ +- 0.11/sup syst/. Our measurements show qualitative agreement with QCD, but quantitative comparison is hampered by phenomenological uncertainties. The experimental situation is quite good, with substantial agreement between our measurements and those of others. 86 references
Measurement of the nucleon structure function using high energy muons
Energy Technology Data Exchange (ETDEWEB)
Meyers, P.D.
1983-12-01
We have measured the inclusive deep inelastic scattering of muons on nucleons in iron using beams of 93 and 215 GeV muons. To perform this measurement, we have built and operated the Multimuon Spectrometer (MMS) in the muon beam at Fermilab. The MMS is a magnetized iron target/spectrometer/calorimeter which provides 5.61 kg/cm/sup 2/ of target, 9% momentum resolution on scattered muons, and a direct measure of total hadronic energy with resolution sigma/sub nu/ = 1.4..sqrt..nu(GeV). In the distributed target, the average beam energies at the interaction are 88.0 and 209 GeV. Using the known form of the radiatively-corrected electromagnetic cross section, we extract the structure function F/sub 2/(x,Q/sup 2/) with a typical precision of 2% over the range 5 < Q/sup 2/ < 200 GeV/sup 2//c/sup 2/. We compare our measurements to the predictions of lowest order quantum chromodynamics (QCD) and find a best fit value of the QCD scale parameter ..lambda../sub LO/ = 230 +- 40/sup stat/ +- 80/sup syst/ MeV/c, assuming R = 0 and without applying Fermi motion corrections. Comparing the cross sections at the two beam energies, we measure R = -0.06 +- 0.06/sup stat/ +- 0.11/sup syst/. Our measurements show qualitative agreement with QCD, but quantitative comparison is hampered by phenomenological uncertainties. The experimental situation is quite good, with substantial agreement between our measurements and those of others. 86 references.
Preliminary Results on the Experimental Investigation of the Structure Functions of Bound Nucleons
Bodek, A
2015-01-01
We present preliminary results on an experimental study of the nuclear modification of the longitudinal ($\\sigma_L$) and transverse ($\\sigma_T$) structure functions of nucleons bound in nuclear targets. The origin of these modifications (commonly referred as as the EMC effect) is not fully understood. Our measurements of R= $\\sigma_L / \\sigma_T$ for nuclei ($R_A$) and for deuterium ($R_D$) indicate that nuclear modifications of the structure functions of bound nucleons are different for the longitudinal and transverse structure functions, and that contrary to expectation from several theoretical models, $R_A< R_D$.
Scaling properties of the structure functions of nucleon as a quark-diquark bound state
International Nuclear Information System (INIS)
Expressions for the nucleon structure functions through the simultaneous wave functions are represented in the form that is convenient for analysis of scaling properties and comparison with experimental data. It is shown that at any wave functions of the quark-diquark system these formulae contain scaling parts depending on the Nachtmann variable, and power corrections. The behaviour of the structure functions is determined near the elastic threshold
Connection between In Medium Nucleon Form Factors and Deep Inelastic Structure Functions
Liuti, Simonetta(University of Virginia Physics Department, 382 McCormick Rd., Charlottesville, VA 22904, USA)
2006-01-01
We present a connection between the modifications induced by the nuclear medium of the nucleon form factors and of the deep inelastic structure functions, obtained using the concept of generalized parton distributions. Generalized parton distributions allow us to access elements of the partonic structure that are common to both the hard inclusive and exclusive scattering processes in nuclei.
Target Mass Correction for the Polarized Nucleon Structure Function
International Nuclear Information System (INIS)
We use the phenomenological valon model to extract polarized parton densities and polarized proton structure function. Since the analytical result at large values of x and low values of Q2 is not in good agreement with available experimental data, we employ target mass correction to increase the reliability of the calculations. New comparison confirms a better agreement with the experimental data. (author)
Target Mass Correction for the Polarized Nucleon Structure Function
Mirjalili, A.; Khorramian, A. N.; Tehrani, S. A.; Saffar, H. M.
2009-11-01
We use the phenomenological valon model to extract polarized parton densities and polarized proton structure function. Since the analytical result at large values of x and low values of Q2 is not in good agreement with available experimental data, we employ target mass correction to increase the reliability of the calculations. New comparison confirms a better agreement with the experimental data.
Nucleon spin structure function from the instanton vacuum
International Nuclear Information System (INIS)
We discuss the evaluation of the nucleon isoscalar axial coupling, gA(0), in the instanton vacuum using the 1/NC expansion. This approach allows a fully consistent treatment of the U(1)A anomaly. We compute the nucleon matrix element of the topological charge, , and show that it reduces to the matrix element of the isoscalar axial quark current. Our arguments show that the usual evaluation of gA(0) in the chiral quark soliton model is consistent with the U(1)A anomaly in leading order of 1/NC. Such calculations give gA(0) = 0.36, which is in agreement with the recent estimate by Ellis and Karliner. (author)
Nucleon spin structure function from the instanton vacuum
Energy Technology Data Exchange (ETDEWEB)
Weiss, C. [Inst. fuer Theoretishe Physik 2, Ruhr Univ. Bochum, Bochum (Germany)
1996-06-01
We discuss the evaluation of the nucleon isoscalar axial coupling, g{sub A}{sup (0)}, in the instanton vacuum using the 1/N{sub C} expansion. This approach allows a fully consistent treatment of the U(1){sub A} anomaly. We compute the nucleon matrix element of the topological charge,
Nucleon Structure Functions from a Chiral Soliton in the Infinite Momentum Frame
Gamberg, L P; Weigel, H
1998-01-01
The leading twist contributions to the nucleon structure functions are dominated by light like correlations. For models which describe the nucleon as a (static) localized object these correlations are accessible upon transformation to the infinite momentum frame (IMF). As a consequence of the Lorentz contraction associated with boosting the quark fields to the IMF the structure functions computed from this configuration are different from zero only when the Bjorken scaling variable is less than unity. This is a consequence of the Lorentz contraction associated with this boost resulting in proper support for model structure functions. As an example we show that for structure functions calculated in the valence quark approximation to the Nambu-Jona-Lasinio chiral soliton model the Lorentz contraction also has significant effects for moderate values of the Bjorken variable.
Test of determination of nucleon structure functions in the hypothesis of scalar di-quark existence
International Nuclear Information System (INIS)
The authors present the nucleon structure functions that have been obtained in the hypothesis of existence of a scalar di-quark, progressively broken by increasing energy of electromagnetic probe (Stockolm model). Comparisons with other models and experimental results are presented. 20 figs
Spin structure functions of the nucleon measured at SALC
International Nuclear Information System (INIS)
We have measured the spin structure functions g2p and g2d over the kinematic range 0.02?x?0.8 and 0.6?Q2?20 (GeV/c)2 by scattering 29.1 and 32.3 GeV longitudinally polarized electrons fro transversely polarized NH3 and 6LiD targets. The statistical errors are approximately three times smaller than previous measurements. Very preliminary results for xg2 are compared with the twist-2 Wandzura-Wilczek calculation at the three electron scattering angles used in this experiment. Using a fit to world data, values for the twist-3 matrix element d2 are extracted and compared to various models. Results for the asymmetry Aperpendicular for inclusive single hadron photoproduction are also presented. These are significantly different from zero for the proton target at small angles. (author)
Quantum chromodynamics and the nucleon longitudinal structure function
International Nuclear Information System (INIS)
The phenomenon of asymptotic freedom together with the theoretical tools of the operator product expansion and renormalisation group allow a systematic and reliable application of perturbative quantum chromodynamics (Q.C.D.) to deep inelastic lepton-hadron scattering. Leading order Q.C.D. predictions for the ratio of the longitudinal to transverse cross-section, R are concluded not to give a satisfactory description of the current data at large X > 0.3. Here this perturbative analysis is extended to include the next to leading order, Q.C.D. contributions. This involves calculating the fourth order contribution to the flavour non-singlet longitudinal coefficient function that appears in the light cone expansion. A technique that regulates the spurious mass-singularities encountered in a consistent manner is discussed, and its use justified through examples utilising the optical theorem. The Q.C.D. expression for the moments of the flavour non-singlet longitudinal structure function is then inverted using a simple technique, allowing a plot of the next to leading order Q.C.D. corrections to the ratio R. Such corrections are found to be small (approximately 12% for X>0.5) and it is concluded that to this order of perturbation theory a discrepancy between theory and experiment still exists. (author)
Polarized deeply inelastic scattering (DIS) structure functions for nucleons and nuclei
International Nuclear Information System (INIS)
We extract parton distribution functions (PDFs) and structure functions from recent experimental data of polarized lepton-deeply inelastic scattering (DIS) on nucleons at next-to-leading order (NLO) quantum chromodynamics. We apply the Jacobi polynomial method to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution as this is numerically efficient. Having determined the polarized proton and neutron spin structure, we extend this analysis to describe 3He and 3H polarized structure functions, as well as various sum rules. We compare our results with other analyses from the literature.
Structure function measurements in the deep inelastic muon-nucleon scattering
International Nuclear Information System (INIS)
Measurements of deep inelastic scattering events on a combined copper and deuterium target were performed by the European Muon Collaboration (EMC) using a muon beam at CERN's SPS with energies at 100 GeV and 280 GeV. The data are analysed and compared with a detailed Monte-Carlo simulation and allow the determination of structure functions from both targets. In the light of the present discrepancy between EMC's and BCDMS's structure functions, stringend cuts were applied to the data. The results confirm the EMC structure function measurements on unbound nucleons. The comparison between the copper structure function from this experiment and the NA2 iron structure function shows a trend to lower values at low xBj. (orig.)
Nucleon structure functions from nu(anti-nu) interactions in bubble chambers
International Nuclear Information System (INIS)
The nucleon structure functions F2 and xF3 have been extracted as functions of the scaling variable x and Q2 - over a wide range of Q2(.1 to 100 GeV2/c2) - using nu(anti-nu) interactions in Ne-H2 filled bubble chambers from low energy wide band experiments at Brookhaven National Laboratory and high energy narrow band experiments at Fermi National Accelerator Laboratory. The extracted values of the structure functions were used to test specific predictions of quark-parton model and scaling violations predicted by QCD. Global fits to the structure functions using Buras-Gaemers parameterization yield a value for the scale parameter ? of 245 +/- 840 MeV/c. A moment analysis of the non-singlet structure function yields ? = 500 +/- 480 MeV/c and the slopes of Log-Log moments are consistent with QCD predictions
Next-to-Leading Order Description of Nucleon Structure Function In Valon Model
Arash, Firooz; Khorramia, Ali Naghi
1999-01-01
We have improved and examined the applicability of the valon model where the structure of any hadron is determined by the structure of its constituent quarks. Nucleon structure functions are calculated within this model in the Next-to-Leading order. The results compare well with the experimental data. The model handles the bound state problem and the calculations show a flat or almost flat behavior for $F_{2}$ which sets in at some region of $x\\leq 10^{-5}$at fixed $Q^{2}$. ...
A two component model describing nucleon structure functions in the low-x region
Energy Technology Data Exchange (ETDEWEB)
Bugaev, E.V. [Institute for Nuclear Research of the Russian Academy of Sciences, 7a, 60th October Anniversary prospect, Moscow 117312 (Russian Federation); Mangazeev, B.V. [Irkutsk State University, 1, Karl Marx Street, Irkutsk 664003 (Russian Federation)
2009-12-15
A two component model describing the electromagnetic nucleon structure functions in the low-x region, based on generalized vector dominance and color dipole approaches is briefly described. The model operates with the mesons of rho-family having the mass spectrum of the form m{sub n}{sup 2}=m{sub r}ho{sup 2}(1+2n) and takes into account the nondiagonal transitions in meson-nucleon scattering. The special cut-off factors are introduced in the model, to exclude the gamma-qq-bar-V transitions in the case of narrow qq-bar-pairs. For the color dipole part of the model the well known FKS-parameterization is used.
International Nuclear Information System (INIS)
The x dependence of the longitudinal structure function Fsub(L) was determined with the CHARM neutrino detector exposed to neutrino and antineutrino wide-band beams of the CERN 400 GeV SPS. The results show a clear deviation from the Callan-Gross relation. The amount and the x dependence of this deviation are in agreement with the contribution coming from a finite transverse momentum of the partons in the nucleon if both the intrinsic and perturbative QCD terms are taken into account. (orig.)
Target mass corrections to QCD Bjorken sum rule for nucleon spin structure functions
International Nuclear Information System (INIS)
We discuss the possible target mass corrections in the QCD analysis of nucleon's spin-dependent structure functions measured in the polarized deep-inelastic leptoproduction. The target mass correction for the QCD Bjorken sum rule is obtained from the Nachtmann moment and its magnitude is estimated employing positivity bound as well as the experimental data for the asymmetry parameters. We also study the uncertainty due to target mass effects in determining the QCD effective coupling constant ?s(Q2) from the Bjorken sum rule. The target mass effect for the Ellis-Jaffe sum rule is also briefly discussed. (author)
Nucleon size and nucleon structure
International Nuclear Information System (INIS)
Hidden-color basis states of multiquark systems are expressed in terms of states involving color-singlet hadrons. The size of various nucleon form factors is used to separate the interior perturbative region of quarks from the exterior nonperturbative region of hadrons. The distinction between the baryon interior and its exterior appears to be relevant in baryon spectroscopy and in nuclear forces. 26 refs.; 1 figure
Next-to-Leading Order Description of Nucleon Structure Function In Valon Model
Arash, F; Arash, Firooz; Khorramia, Ali Naghi
1999-01-01
We have improved and examined the applicability of the valon model where the structure of any hadron is determined by the structure of its constituent quarks. Nucleon structure functions are calculated within this model in the Next-to-Leading order. The results compare well with the experimental data. The model handles the bound state problem and the calculations show a flat or almost flat behavior for $F_{2}$ which sets in at some region of $x\\leq 10^{-5}$at fixed $Q^{2}$. The emergence of this behavior is a consequence of the model and was not put in a priori as a theoretical guess. It seems that such a flatness can be inferred from HERA data, although, not completely confirmed yet. A set of parton distributions are given and their evolutions are tested. Some qualitative implications of the model for the spin structure of the proton is discussed.
Nucleon structure functions from dynamical (2+1)-flavor domain wall fermions
Ohta, Shigemi
2008-01-01
We report isovector form factors and low moments of isovector structure functions of nucleon from the coarse RIKEN-BNL-Columbia (RBC) and UKQCD joint dynamical (2+1)-flavor domain-wall fermions (DWF) ensembles. The lattice cut off is estimated at (a^{-1}=1.7) GeV. The lattice volume is as large as 2.7 fm across. We carefully optimize the nucleon source/sink separation in time to about 1.4 fm. Unexpectedly large finite-size effect in the axial charge is found. The effect scales with a single variable, the product (m_\\pi L) of the pion mass (m_\\pi) and lattice spatial linear extent (L), and sets in at around (m_\\pi L = 5). We also discuss momentum-transfer dependence of the vector, induced tensor, axial-vector and induced pesudo-scalar form factors. From structure functions, fully non-perturbatively renormalized iso-vector quark momentum fraction, (_{u-d}), helicity fraction, (_{\\Delta u - \\Delta d}), and transversity, (_{\\delta u - \\delta d}), are reported, as well as an unrenormalized twist-3 coefficient, (d_...
Nuclear effects in F{sub 3} structure function of nucleon
Energy Technology Data Exchange (ETDEWEB)
Athar, M. Sajjad [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India)], E-mail: sajathar@rediffmail.com; Singh, S.K. [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India); Vacas, M.J. Vicente [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, 46100 Burjassot (Valencia) (Spain)
2008-10-02
We study nuclear effects in the F{sub 3}{sup A}(x) structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio R(x,Q{sup 2})=(F{sub 3}{sup A}(x,Q{sup 2}))/(AF{sub 3}{sup N}(x,Q{sup 2})) and the Gross-Llewellyn Smith (GLS) integral G(x,Q{sup 2})={integral}{sub x}{sup 1}dxF{sub 3}{sup A}(x,Q{sup 2}) in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data.
A detailed study of nucleon structure function in nuclei in the valence quark region
Energy Technology Data Exchange (ETDEWEB)
Bianchi, N. [INFN-Laboratori, Nazionali di Frascati (Italy)
1994-04-01
The so called {open_quotes}EMC effect{close_quotes} discovered during the 1980`s, has caused a big controversy in the community of nuclear and high energy physicists; during the last ten years, five experiments have been performed in different laboratories and several hundreds of papers about the possible interpretation of the modification of the nucleon structure function inside nuclei have been published. However, from the experimental point of view, the main goal of four experiments (EMC, BCDMS, NMC, FNAL) has been to emphasize the region of low x{sub b}, where shadowing effects appear. In the region of valence quarks and nuclear effects (x{sub b} > 0.1 - 0.2) the most reliable data presently available are from the SLAC E139 experiment performed in 1983 with only 80 hours of beam time. New precise data in the valence quark region are necessary to measure separate structure functions F{sub 2}(x{sub b}, Q{sup 2}) and R{sup lt}(x{sub b},Q{sup 2}) = {sigma}{sub l}/{sigma}{sub t}, and to investigate the real A-dependence of the ratio between bound and free-nucleon structure functions which is not completely defined by the SLAC data. Moreover, from the nuclear physics point of view, a measurement on some unexplored nuclei, like {sup 3}He and {sup 48}Ca, would be of great interest. The intermediate scaling region (0.1 < x{sub b} < 0.7) would be accessible at CEBAF if the machine energy will reach 6-8 GeV, as suggested by all the tests performed on the RF cavities. This physics program has been already presented in two letter of intents.
International Nuclear Information System (INIS)
Data are presented on the spin-dependent structure function of the proton, gp1, measured in inclusive polarized muon scattering. The first moment of gp1(x) is compared with that of earlier experiments and with the Ellis-Jaffe prediction. Also semi-inclusive data are shown, where charged hadrons provide information on spin-flavor correlations. In the context of the quark-parton model the data indicate that quark spins contribute a small fraction to the nucleon spin. All published data of g1 in combination confirm the Bjorken sum rule at the 10 percent accuracy level. In a QCD analysis of Fp2 and Fd2, measured with high precision down to small x by NMC, the gluon distribution is determined. The Fn2/Fp2 data are reanalyzed and the Gottfried sum ?10[Fp2(x)-Fn2(x)]/x dx is evaluated. The earlier reported flavor asymmetry in the nucleon is confirmed. copyright 1995 American Institute of Physics
Nucleon isovector structure functions in (2+1)-flavor QCD with domain wall fermions
Aoki, Yasumichi; Lin, Huey-Wen; Ohta, Shigemi; Sasaki, Shoichi; Tweedie, Robert; Yamazaki, Takeshi; Zanotti, James
2010-01-01
We report on numerical lattice QCD calculations of some of the low moments of the nucleon structure functions. The calculations are carried out with gauge configurations generated by the RBC and UKQCD collaborations with (2+1)-flavors of dynamical domain wall fermions and the Iwasaki gauge action ($\\beta = 2.13$). The inverse lattice spacing is $a^{-1} = 1.73$ GeV, and two spatial volumes of ((2.7{\\rm fm})^3) and ((1.8 {\\rm fm})^3) are used. The up and down quark masses are varied so the pion mass lies between 0.33 and 0.67 GeV while the strange mass is about 12 % heavier than the physical one. The structure function moments we present include fully non-perturbatively renormalized iso-vector quark momentum fraction, (_{u-d}), helicity fraction, (_{\\Delta u - \\Delta d}), and transversity, (_{\\delta u - \\delta d}), as well as an unrenormalized twist-3 coefficient, (d_1). The ratio of the momentum to helicity fractions, (_{u-d}/_{\\Delta u - \\Delta d}), does not show dependence on the light quark mass and agrees ...
Nucleon structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Dinter, Simon
2012-11-13
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.
Nucleon structure from lattice QCD
International Nuclear Information System (INIS)
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a2) discretization effects.
Nucleon structure using lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, C.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Constantinou, M.; Hatziyiannakou, K. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Drach, V. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Jansen, K. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Koutsou, G.; Vaquero, A. [The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Leontiou, T. [Frederick Univ, Nicosia (Cyprus). General Dept.
2013-03-15
A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.
Nucleon structure functions from dynamical (2+1)-flavor domain wall fermions
Ohta, Shigemi
2009-01-01
We report lattice-volume independence of low moments of nucleon structure functions from the coarse RIKEN-BNL-Columbia (RBC) and UKQCD joint dynamical (2+1)-flavor domain-wall fermions (DWF) ensembles at the lattice cut off of (a^{-1}\\sim1.7) GeV. The isovector quark momentum fraction, (_{u-d}), and helicity fraction, (_{\\Delta u - \\Delta d}), both fully non-perturbatively renormalized are studied on two spatial volumes of ((\\sim {\\rm 2.7 fm})^3) and ((\\sim {\\rm 1.8 fm})^3). Their naturally renormalized ratio, (_{u-d}/_{\\Delta u - \\Delta d}), is not affected by any finite-size effect. It does not depend strongly on light quark mass and does agree well with the experiment. The respective absolute values, fully non-perturbatively renormalized, do not show any finite-size effect either. They show trending toward the respective experimental values at the lightest up- and down-quark mass. This trending down to the experimental values appears to be a real physical effect driven by lighter quarks. The observations a...
Polarized structure function sigma_lt' for kaon electroproduction in the nucleon resonance region
Energy Technology Data Exchange (ETDEWEB)
Rakhsha Nasseripour; B. Raue; Daniel Carman; Pawel Ambrozewicz
2008-02-19
The first measurements of the polarized structure function $\\sigma_{LT'}$ for the reaction $p(\\vec e,e'K^+)\\Lambda$ in the nucleon resonance region are reported. Measurements are included from threshold up to $W$=2.05~GeV for central values of $Q^2$ of 0.65 and 1.00~GeV$^2$, and nearly the entire kaon center-of-mass angular range. $\\sigma_{LT'}$ is the imaginary part of the longitudinal-transverse response and is expected to be sensitive to interferences between competing intermediate $s$-channel resonances, as well as resonant and non-resonant processes. The results for $\\sigma_{LT'}$ are comparable in magnitude to previously reported results from CLAS for $\\sigma_{LT}$, the real part of the same response. An intriguing sign change in $\\sigma_{LT'}$ is observed in the high $Q^2$ data at $W\\approx 1.9$~GeV. Comparisons to several existing model predictions are shown.
Watanabe, Akira; Suzuki, Katsuhiko
2014-06-01
We present analyses on nucleon structure functions at small Bjorken x in the framework of holographic QCD. In this study, we improve the description of the target nucleon in the current setup of the holographic model by introducing a soft-wall AdS/QCD model, in which the anti-de Sitter geometry is smoothly cut off at the infrared boundary. Combining the improved Pomeron-nucleon coupling and the wave function of the five-dimensional U(1) vector field with the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel, we obtain the structure functions. Here we focus on the nonperturbative kinematical region, where 10-6?x?10-2 and Q2? a few (GeV2), and show that our calculations for F2p and FLp are consistent with experimental data of the deep inelastic scattering at HERA. Furthermore, we find that the resulting longitudinal-to-transverse ratio of the structure functions, FLp/FTp, depends on both x and Q2.
Nucleon structure functions at small $x$ via the Pomeron exchange in AdS space with a soft IR wall
Watanabe, Akira
2013-01-01
We present analyses on nucleon structure functions at the small Bjorken-$x$ in the framework of holographic QCD. In this study, we improve the description of the target nucleon in the current setup of the holographic model by introducing a soft-wall AdS/QCD model, in which the AdS geometry is smoothly cut off at IR. Combining the improved Pomeron-nucleon coupling and the wave function of the 5D U(1) vector field with the BPST Pomeron exchange kernel, then we obtain the structure functions. Here we focus on the nonperturbative kinematical region, where $10^{-6} \\leq x \\leq 10^{-2}$ and $0.1 \\leq Q^2 \\leq 10$ [GeV$^2$], and show that our calculations for $F_2^p$ and $F_L^p$ are consistent with experimental data of the deep inelastic scattering at HERA. Furthermore, we find that the resulting longitudinal-to-transverse ratio of the structure functions, $F_L^p/F_T^p$, depends on both of $x$ and $Q^2$.
Nucleon parton distributions and nuclear structure
International Nuclear Information System (INIS)
The current experimental status of measurements of nucleon structure functions in deep inelastic lepton scattering is presented. Recent BCDMS and SLAC results provide a consistent data set for charged lepton scattering. New probes of parton distributions: direct photons, Drell Yan di-muon production, W, Z and heavy quark production are providing information on the gluon an antiquark distributions. The implications of these data on our understanding of the structure of the nucleon, and the structure of the nucleon in the nucleus are discussed. 26 refs., 9 figs
International Nuclear Information System (INIS)
Inclusive neutrino and antineutrino charged current interactions were studied in the CHARM detector exposed to neutrino and antineutrino Wide Band Beams of the CERN 400 GeV SPS. The x and Q2 dependence of the structure functions F2 and xF3 and of the antiquark momentum distribution q were determined. The data have been interpreted in terms of QCD theory using the Furmanski-Petronzio method. In this way we have determined #betta#sub(LO)=[190+70sub(-40)(stat)+-70 (syst.)] MeV and the structure functions of quarks and gluons without specific assumptions on their analytic dependence. The results agree with previous experiments which relied on model assumptions in the analysis. We conclude that the model independent simultaneous analysis of the xF3, F2, anti q structure functions gives a more reliable determination of the gluon distribution in the nucleon. (orig.)
Probing nuclear structure with nucleons
International Nuclear Information System (INIS)
The goal of this lecture is to show how nucleon scattering can be used to probe the structure of target nuclei, and how nucleon scattering observables can be interpreted in terms of nuclear structure using microscopic optical potentials. After a brief overview of the specificities of nucleon-nucleus scattering, and a quick reminder on scattering theory, the main part of this lecture is devoted to the construction of optical potentials in which the target nuclei structure information is folded with an effective interaction. Several examples of such microscopic optical model potentials are given. (author)
Khorramian, Ali N; Monfared, S Taheri; Arbabifar, F; Olness, F I
2010-01-01
We extract parton distribution functions (PDFs) and structure functions from recent experimental data of polarized lepton-DIS on nuclei at next-to-leading order (NLO) Quantum Chromodynamics. We apply the Jacobi polynomial method to the DGLAP evolution as this is numerically efficient. Having determined the polarized proton and neutron spin structure, we extend this analysis to describe 3He and 3H polarized structure functions, as well as various sum rules. We compare our results with other analyses from the literature.
International Nuclear Information System (INIS)
We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 2 2. The data have been used to accurately perform over 170 Rosenbluth-type longitudinal/transverse separations. The precision R ?L/?T data are presented here, along with the first separate values of the inelastic structure functions F1 and FL in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q2 = 1 GeV2 in the separated structure functions independently
International Nuclear Information System (INIS)
Higher twist effects in the deeply inelastic scattering are studied. We start with a short review of the theoretical results on higher twists in QCD. Within the saturation model we perform a twist analysis of the nucleon structure functions FT and FL at small value of the Bjorken variable x. The parameters of the model are fitted to the HERA F2 data, and we derive a prediction for the longitudinal structure function FL. We conclude that for FL the higher twist corrections are sizable whereas for F2=FT+FL there is a nearly complete cancellation of twist-4 corrections in FT and FL. We discuss a few consequences for future LHC measurements. (orig.)
From Nuclear Structure to Nucleon Structure
Liu, Keh-Fei
2014-01-01
Similarities between nuclear structure study with many-body theory approach and nucleon structure calculations with lattice QCD are pointed out. We will give an example of how to obtain the connected sea partons from a combination of the experimental data, a global fit of parton distribution functions and a lattice calculation. We also present a complete calculation of the quark and glue decomposition of the proton momentum and angular momentum in the quenched approximation. It is found that the quark orbital angular momentum constitutes about 50% of the proton spin.
Directory of Open Access Journals (Sweden)
E.R. Nocera
2015-03-01
Full Text Available I investigate the behavior of spin-dependent parton distribution functions in the regions of small and large momentum fractions x. I present a systematic comparison between predictions for relevant observables obtained with various models of nucleon spin structure and a recent global analysis of spin-dependent distributions, NNPDFpol1.1. Together with its unpolarized counterpart, NNPDF2.3, they form a mutually consistent set of parton distributions. Because they include most of the available experimental information, and are determined with a minimally biased methodology, these are especially suited for such a study. I show how NNPDFpol1.1 can discriminate between different theoretical models, even though NNPDF uncertainties remain large near the endpoints x?0 and x?1, due to the lack of experimental information. I discuss how our knowledge of nucleon spin structure may be improved at small x by future measurements at an ElectronIon Collider, and at large x by recent measurements at Jefferson Lab, also in view of its 12 GeV upgrade.
Valon picture and anomalous behavior of nucleon structure in nuclei
Zhu, W.; Shen, J. G.
1989-03-01
It is shown that the anomalous behavior of the nucleon structure function in nuclei may be explained by the valon picture of the constituent quark model. This anomalous behavior can be ascribed to the weakening of the string tension or nucleon swelling in the nuclear medium and to the Fermi motion of nucleons in a nucleus. We discuss how changes in nucleon size might influence the EMC effect.
Valon picture and anomalous behavior of nucleon structure in nuclei
International Nuclear Information System (INIS)
It is shown that the anomalous behavior of the nucleon structure function in nuclei may be explained by the valon picture of the constituent quark model. This anomalous behavior can be ascribed to the weakening of the string tension or nucleon swelling in the nuclear medium and to the Fermi motion of nucleons in a nucleus. We discuss how changes in nucleon size might influence the EMC effect. (orig.)
Nucleon Spin Structure And Electromagnetic Excitation Of Nucleon Resonances
Mathur, N
2000-01-01
Quantum Chromodynamics (QCD) is the theoretical key to study the structure of the nucleon. However, it is difficult to use, particularly in the non-perturbative domain. This work uses electromagnetic interactions to gain new theoretical insights into the non-perturbative chromodynamic structure of the nucleon. This is done in two ways. The first method adopted is the Lattice Gauge Theory to study the spin structure of the nucleon and try to answer the question, Where does the nucleon spin come from ? To date, theoretically, we do not have a comprehensive understanding about the nucleon spin structure. Experimental findings reveal that quark spin contributes only a small fraction to the proton spin. However, there are no data which can conclusively tell us about the contribution of gluons and the orbital angular momentum of quarks. Through lattice calculations, we have studied the total angular momentum contributions from quarks, thereby deducing the quark orbital angular momentum, and th...
International Nuclear Information System (INIS)
570 000 neutrino-iron and 370 000 antineutrino-iron charged-current events were obtained from the Wide Band Beam exposure of the CDHS detector at CERN in 1983, at energies ranging from 20 to 400 GeV. These large statistics allowed a precise measurement of the charged-current differential cross-sections and a detailed study of systematic effects. The nucleon structure functions have been determined in the framework of the quark-parton model, in the kinematic range: 0.01522/c2. The longitudinal structure function FL(x) is in good agreement with the QCD predicted shape. Deviations from scale invariance are clearly seen from the functions F2 and xF3. The Q2 evolution of the valence quark distribution has been compared with the QCD prediction in order to measure the scale parameter ?. A good agreement is obtained only if the low Q2 points are removed from the comparison. Our experiment favours a value of ? between 50 and 250 MeV
International Nuclear Information System (INIS)
We have studied the nuclear effects on high energy antineutrino charged current interactions by comparing the data which were taken in the Bubble Chamber BEBC filled with Neon and Deuterium. On the one hand, the study of nuclear reinteractions gave us the possibility to estimate the formation time of hadrons. On the other hand, the comparison of structure functions does not show any significant difference between Neon and Deuterium. Though this result does not contradict the effects observed with charged leptons by the EMC and SLAC experiments, it is strongly incompatible with certain theoretical interpretations which implied a stronger effect in antineutrino interactions
Measurement of the nucleon structure function F2 in the nuclear medium and evaluation of its moments
International Nuclear Information System (INIS)
We report on the measurement of inclusive electron scattering off a carbon target performed with CLAS at Jefferson Laboratory. A combination of three different beam energies 1.161, 2.261 and 4.461 GeV allowed us to reach an invariant mass of the final-state hadronic system W?2.4 GeV with four-momentum transfers Q2 ranging from 0.2 to 5(GeV/c)2. These data, together with previous measurements of the inclusive electron scattering off proton and deuteron, which cover a similar continuous two-dimensional region of Q2 and Bjorken variable x, permit the study of nuclear modifications of the nucleon structure. By using these, as well as other world data, we evaluated the F2 structure function and its moments. Using an OPE-based twist expansion, we studied the Q2-evolution of the moments, obtaining a separation of the leading-twist and the total higher-twist terms. The carbon-to-deuteron ratio of the leading-twist contributions to the F2 moments exhibits the well-known EMC effect, compatible with that discovered previously in x-space. The total higher-twist term in the carbon nucleus appears, although with large systematic uncertainties, to be smaller with respect to the deuteron case for n<7, suggesting partial parton deconfinement in nuclear matter. We speculate that the spatial extension of the nucleon is changed when it is immersed in the nuclear medium.
International Nuclear Information System (INIS)
The moments of nucleon structure functions are found by the formula expressing them through the pion moments. For the calculation of the latter the solutions of the covariant single-- time two-particle equation are used, corresponding to the interaction kernel chosen in the form of the one-gluon exchange amplitude
New relations in lepton-nucleon scattering independent of the nucleon structure
International Nuclear Information System (INIS)
New relations in deep inelastic and (quasi-)elastic scattering of polarized electrons and positrons (?-mesons) on non-polarized nucleons have been obtained. They connect cross sections with standard model parameters and are independent of the structure functions and form factors of the nucleon. A well known example is the Paschos-Wolfenstein relation in (?-bar)N-scattering. 6 refs
Measurement of the Nucleon Structure Function F2 in the Nuclear Medium and Evaluation of its Moments
Osipenko, M
2010-01-01
We report on the measurement of inclusive electron scattering off a carbon target performed with CLAS at Jefferson Laboratory. A combination of three different beam energies 1.161, 2.261 and 4.461 GeV allowed us to reach an invariant mass of the final-state hadronic system W~2.4 GeV with four-momentum transfers Q2 ranging from 0.2 to 5 GeV2. These data, together with previous measurements of the inclusive electron scattering off proton and deuteron, which cover a similar continuous two-dimensional region of Q2 and Bjorken variable x, permit the study of nuclear modifications of the nucleon structure. By using these, as well as other world data, we evaluated the F2 structure function and its moments. Using an OPE-based twist expansion, we studied the Q2-evolution of the moments, obtaining a separation of the leading-twist and the total higher-twist terms. The carbon-to-deuteron ratio of the leading-twist contributions to the F2 moments exhibits the well known EMC effect, compatible with that discovered previou...
Nucleon structure from stochastic estimators
Bali, Gunnar S; Glle, Benjamin; Gckeler, Meinulf; Najjar, Johannes; Rdl, Rudolf; Schfer, Andreas; Sternbeck, Andr; Sldner, Wolfgang
2013-01-01
Using stochastic estimators for connected meson and baryon three-point functions has successfully been tried in the past years. Compared to the standard sequential source method we trade the freedom to compute the current-to-sink propagator independently of the hadron sink for additional stochastic noise in our observables. In the case of the nucleon we can use this freedom to compute many different sink-momentum/polarization combinations, which grants access to more virtualities. We will present preliminary results on the scalar, electro-magnetic and axial form factors of the nucleon in $N_f=2+1$ lattice QCD and contrast the performance of the stochastic method to the sequential source method. We find the stochastic method to be competitive in terms of errors at fixed cost.
Nucleon form factors and structure functions with N_f=2+1 dynamical domain wall fermions
Yamazaki, T
2007-01-01
We report isovector form factors and low moments of structure functions of nucleon in numerical lattice quantum chromodynamics (QCD) from the on-going calculations by the RIKEN-BNL-Columbia (RBC) and UKQCD Collaborations with (2+1) dynamical flavors of domain-wall fermion (DWF) quarks. We calculate the matrix elements with four light quark masses, corresponding to pion mass values of m_\\pi = 330-670 MeV, while the dynamical strange mass is fixed at a value close to physical, on (2.7 fm)^3 spatial volume. We found that our axial charge, g_A, at the lightest mass exhibits a large deviation from the heavier mass results. This deviation seems to be a finite-size effect as the g_A value scales with a single parameter, m_\\pi L, the product of pion mass and linear spatial lattice size. The scaling is also seen in earlier 2-flavor dynamical DWF and Wilson quark calculations. Without this lightest point, the three heavier mass results show only very mild mass dependence and linearly extrapolate to g_A=1.16(6). We dete...
International Nuclear Information System (INIS)
Using the CERN bubble chamber data on ?, anti-? interactions on nucleons in the energy range 22, 2xF1 and xF3 are determined as a function of x and Q2. The Callan-Gross ratio is measured to be A=2xF1/F2=0.89+-0.12 in the range 322. The Gross-Llewellyn-Smith sum rule is tested: we measure > 2.5+-0.5 valence quark per nucleon. Deviations from Bjorken scaling are observed in F2 and xF3 and their Nachtmann moments are quantitatively consistent with predictions of QCD. The value of the strong interaction parameter is ?=0.74+-0.05 GeV. The moments of the gluon distribution indicate an x distribution of gluon comparable to that of the valence quarks. (author)
International Nuclear Information System (INIS)
The authors present the analytic leading-twist three-loop pertur-bative QCD correction to the moment ?01dxFLp-n(x,Q2) of the non-singlet longitudinal structure function FL of the deep inelastic electron-nucleon scattering. It provides quantitative information on uncertainties of pQCD predictions for D(x,Q2) ?l/?/T. (author). 24 refs.; 2 figs
New Results on Nucleon Spin Structure
Energy Technology Data Exchange (ETDEWEB)
Jian-Ping Chen
2005-09-10
Recent precision spin structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure in the valence quark (high-x) region and improved our understanding of higher-twist effects, spin sum rules and quark-hadron duality. First, results of a precision measurement of the neutron spin asymmetry, A{sub 1}{sup n}, in the high-x region are discussed. The new data shows clearly, for the first time, that A{sub 1}{sup n} becomes positive at high x. They provide crucial input for the global fits to world data to extract polarized parton distribution functions. Preliminary results on A{sub 1}{sup p} and A{sub 1}{sup d} in the high-x region have also become available. The up and down quark spin distributions in the nucleon were extracted. The results for {Delta}d/d disagree with the leading-order pQCD prediction assuming hadron helicity conservation. Then, results of a precision measurement of the g{sub 2}{sup n} structure function to study higher-twist effects are presented. The data show a clear deviation from the lead-twist contribution, indicating a significant higher-twist (twist-3 or higher) effect. The second moment of the spin structure functions and the twist-3 matrix element d{sub 2}{sup n} results were extracted at a high Q{sup 2} of 5 GeV{sup 2} from the measured A{sub 2}{sup n} in the high-x region in combination with existing world data and compared with a Lattice QCD calculation. Results for d{sub 2}{sup n} at low-to-intermediate Q{sup 2} from 0.1 to 0.9 GeV{sup 2} were also extracted from the JLab data. In the same Q{sup 2} range, the Q{sup 2} dependence of the moments of the nucleon spin structure functions was measured, providing a unique bridge linking the quark-gluon picture of the nucleon and the coherent hadronic picture. Sum rules and generalized forward spin polarizabilities were extracted and compared with Chiral Perturbation Theory calculations and phenomenological models. Finally, preliminary results on the resonance spin structure functions in the Q{sup 2} range from 1 to 4 GeV{sup 2} were presented, which, in combination with DIS data, will enable a detailed study of the quark-hadron duality in spin structure functions.
International Nuclear Information System (INIS)
From the nucleon structure functions measured by the CHARM Collaboration in inclusive neutrino and antineutrino CC interactions we determined the QCD parameter ?sub(MS) = 310 +- 140 (stat.) +- 70 (syst.) MeV using the Furmanski-Petronzio method. With the same method we extrapolated the behaviour of the quark (q + q) and the gluon x-distributions up to Q2 = 10000 GeV2 using perturbative QCD. The extrapolated structure functions are compared with recent results coming from the two-jet differential cross section in proton-antiproton interactions at ?s = 540 GeV and Q2 = 2000 GeV2. (orig.)
Nucleon spin structure functions
International Nuclear Information System (INIS)
There has been recent excitement arising from the claim by the EMC collaboration that none of the proton's spin is carried by quarks. There are many textbooks, including those written by some members of this audience which assert that the proton's spin is carried by quarks. I will review the history of deep inelastic scattering of polarized leptons from polarized protons, culminating in this most recent dramatic claim. I will show that, for the last decade, data have appeared consistent with predictions of the quark model and highlight what the new and potentially exciting data are. I will conclude with suggestions for the future, and discuss the polarization dependence of inclusive hadron production. 35 refs
International Nuclear Information System (INIS)
In this thesis the nucleon structure function xF3 is determined from the inclusive measurement of the deep inelastic neutrino nucleon charged current interaction. The data were taken in the CERN wide band neutrino beam using the detector of the CERN-Dortmund-Heidelberg-Saclay collaboration. This detector serves at the same time as target, as hadron energy calorimeter and as muon spectrometer. One major aspect of this work was to study the possibility of using high statistics wide band beam data for structure function analysis. The systematic errors specific to this kind of beam are investigated. To obtain the differential cross sections about 100000 neutrino and 75000 antineutrino events in the energy range 20-200 GeV are analysed. The differential cross sections are normalized to the total cross sections, as measured in the narrow band beam by the same collaboration. The calculated structure function xF3 shows significant deviations from scaling. These scaling violations are compared quantitatively with the predictions of quantum chromodynamics. (orig.)
Short-range correlations of partons & 3D nucleon structure
Directory of Open Access Journals (Sweden)
Schweitzer P.
2014-03-01
Full Text Available Dynamical breaking of chiral symmetry in QCD is caused by non-perturbative interactions on a scale ? ? 0.3 fm much smaller than the hadronic size R ? 1 fm. This has important consequences for the nucleon structure such as the prediction that the transverse momentum distribution of sea quarks is significantly broader than the pT -distribution of valence quarks due to short-range correlations between sea quarks in the nucleons light-cone wave function.
The spin structure of the nucleon
International Nuclear Information System (INIS)
The present understanding of the spin structure of the nucleon is described. The world's data on spin-dependent deep inelastic scattering is summarized with particular emphasis on the new data from the last year. Next-to-leading order (NLO) QCD analysis of existing data provides another successful test of QCD. However, the uncertainty arising from the low x extrapolation provides a serious impediment to extracting information on the spin structure of the nucleon using sum rules formed from inclusive data. The NLO analyses suggest that the gluon contribution to the nucleon spin is sizable. Possible initiatives to directly probe the gluon spin are described. Semi-inclusive measurements at present underway will study new aspects of the nucleon spin structure
The nucleon wave function at the origin
Gruber, Michael
2010-01-01
We calculate the next-to-leading order perturbative corrections to the SVZ sum rules for the coupling f_N, the nucleon leading twist wave function at the origin. The results are compared to the established Ioffe sum rules and also to lattice QCD simulations.
The nucleon wave function at the origin
International Nuclear Information System (INIS)
We calculate the next-to-leading order perturbative corrections to the SVZ sum rules for the coupling fN, the nucleon leading twist wave function at the origin. The results are compared to the established Ioffe sum rules and also to lattice QCD simulations.
Energy Technology Data Exchange (ETDEWEB)
Bartels, Jochen [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Golec-Biernat, Krzysztof [Rzeszow Univ. (Poland). Inst. of Physics; Polish Academy of Sciences, Krakow (Poland). Inst. of Nuclear Physics; Motkyka, Leszek [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Uniwersytet Jagiellonski, Krakow (Poland). Inst. Fizyki
2009-11-15
Higher twist effects in the deeply inelastic scattering are studied. We start with a short review of the theoretical results on higher twists in QCD. Within the saturation model we perform a twist analysis of the nucleon structure functions F{sub T} and F{sub L} at small value of the Bjorken variable x. The parameters of the model are fitted to the HERA F{sub 2} data, and we derive a prediction for the longitudinal structure function F{sub L}. We conclude that for F{sub L} the higher twist corrections are sizable whereas for F{sub 2}=F{sub T}+F{sub L} there is a nearly complete cancellation of twist-4 corrections in F{sub T} and F{sub L}. We discuss a few consequences for future LHC measurements. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Yongguang Liang; Michael Christy; Abdellah Ahmidouch; Christopher Armstrong; John Arrington; Arshak Asaturyan; Steven Avery; O. Baker; Douglas Beck; Henk Blok; C.W. Bochna; Werner Boeglin; Peter Bosted; Maurice Bouwhuis; Herbert Breuer; Daniel Brown; Antje Bruell; Roger Carlini; Jinseok Cha; Nicholas Chant; Anthony Cochran; Leon Cole; Samuel Danagoulian; Donal Day; James Dunne; Dipangkar Dutta; Rolf Ent; Howard Fenker; B. Fox; Liping Gan; Haiyan Gao; Kenneth Garrow; David Gaskell; Ashot Gasparian; Don Geesaman; Ronald Gilman; Paul Gueye; Mark Harvey; Roy Holt; Xiaodong Jiang; Mark Jones; Cynthia Keppel; Edward Kinney; Wolfgang Lorenzon; Allison Lung; David Mack; Pete Markowitz; J.W. Martin; Kevin McIlhany; Daniella Mckee; David Meekins; M.A. Miller; Richard Milner; Joseph Mitchell; Hamlet Mkrtchyan; Robert Mueller; Alan Nathan; Gabriel Niculescu; Maria-Ioana Niculescu; Thomas O' neill; Vassilios Papavassiliou; Stephen Pate; Rodney Piercey; David Potterveld; Ronald Ransome; Joerg Reinhold; E. Rollinde; Oscar Rondon-Aramayo; Philip Roos; Adam Sarty; Reyad Sawafta; Elaine Schulte; Edwin Segbefia; C. Smith; Samuel Stepanyan; Steffen Strauch; Vardan Tadevosyan; Liguang Tang; Raphael Tieulent; Vladas Tvaskis; Alicia Uzzle; William Vulcan; Stephen Wood; Feng Xiong; Lulin Yuan; Markus Zeier; Benedikt Zihlmann; Vitaliy Ziskin
2004-10-01
We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 < Q{sup 2} < 5.5 GeV{sup 2}. The data have been used to accurately perform over 170 Rosenbluth-type longitudinal/transverse separations. The precision R = {sigma}{sub L}/{sigma}{sub T} data are presented here, along with the first separate values of the inelastic structure functions F{sub 1} and F{sub L} in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q{sup 2} = 1 GeV{sup 2} in the separated structure functions independently.
Chiral symmetry and nucleon structure
International Nuclear Information System (INIS)
Recently it has been realized that significant tests of the validity of QCD are available in low energy experiments (E < 500 MeV) by exploiting the property of (broken) chiral symmetry. This technique has been highly developed in The Goldstone boson sector by the work of Gasser and Leutwyler. Application to the nucleon system is much more difficult and is now being carefully developed
Chiral symmetry and nucleon structure
Energy Technology Data Exchange (ETDEWEB)
Holstein, B.R. (Massachusetts Univ., Amherst, MA (United States). Dept. of Physics and Astromony Washington Univ., Seattle, WA (United States). Inst. for Nuclear Theory)
1992-01-01
Recently it has been realized that significant tests of the validity of QCD are available in low energy experiments (E < 500 MeV) by exploiting the property of (broken) chiral symmetry. This technique has been highly developed in The Goldstone boson sector by the work of Gasser and Leutwyler. Application to the nucleon system is much more difficult and is now being carefully developed.
New insights into the spin structure of the nucleon
Bernard, V; Krebs, H; Meiner, U -G
2012-01-01
We analyze the low-energy spin structure of the nucleon in a covariant effective field theory with explicit spin-3/2 degrees of freedom to third order in the small scale expansion. Using the available data on the strong and electromagnetic width of the Delta-resonance, we give parameter-free predictions for various spin-polarizabilities and moments of spin structure functions. We find an improved description of the nucleon spin structure at finite photon virtualities for some observables and point out the necessity of a fourth order calculation.
The spin structure of the nucleon
International Nuclear Information System (INIS)
This document describes the recent experimental results on the spin structure of the nucleon obtained with the electron accelerator Thomas Jefferson National Facility (Jefferson Lab), Virginia. We first discuss the goal of studying the nucleon spin structure and give the basis and phenomenology of high energy lepton scattering. Then, we discuss with some details a few sum rules concerning the spin structure of the nucleon. Those are important tools for studying the nucleon spin structure at Jefferson Lab. We then describe the present experimental situation and analyze the results. We have been able to determine an effective coupling constant for the strong interaction for any regime of quantum chromodynamics which proves that QCD is an approximately conformal theory. We conclude on the perspectives for this field of research, in particular with the 12 GeV energy upgrade of Jefferson Lab. The top priority will be the measurement of generalised parton distributions. The only issue that will stay misunderstood is the role of the very low x domain on the spin structure of the nucleon
Meson-cloud effects in the electromagnetic nucleon structure
Kupelwieser, Daniel
2013-01-01
We study how the electromagnetic structure of the nucleon is influenced by a pion cloud. To this aim we make use of a constituent-quark model with instantaneous confinement and a pion that couples directly to the quarks. To derive the invariant 1- photon-exchange electron-nucleon scattering amplitude we employ a Poincar\\'e- invariant coupled-channel formulation which is based on the point-form of relativistic quantum mechanics. We argue that the electromagnetic nucleon current extracted from this amplitude can be reexpressed in terms of pure hadronic degrees of freedom with the quark substructure of the pion and the nucleon being encoded in electromagnetic and strong vertex form factors. These are form factors of bare particles, i.e. eigenstates of the pure confinement problem. First numerical results for (bare) photon-nucleon and pion-nucleon form factors, which are the basic ingredients of the further calculation, are given for a simple 3-quark wave function of the nucleon.
A covariant model for the nucleon spin structure
Ramalho, G
2015-01-01
We present the results of the covariant spectator quark model applied to the nucleon structure function $f(x)$ measured in unpolarized deep inelastic scattering, and the structure functions $g_1(x)$ and $g_2(x)$ measured in deep inelastic scattering using polarized beams and targets ($x$ is the Bjorken scaling variable). The nucleon is modeled by a valence quark-diquark structure with $S,P$ and $D$ components. The shape of the wave functions and the relative strength of each component are fixed by making fits to the deep inelastic scattering data for the structure functions $f(x)$ and $g_1(x)$. The model is then used to make predictions on the function $g_2(x)$ for the proton and neutron.
Spin Structure of the Nucleon - Status and Recent Results
Kuhn, S E; Leader, E
2008-01-01
After the initial discovery of the so-called "spin crisis in the parton model" in the 1980s, a large set of polarization data in deep inelastic lepton-nucleon scattering was collected at labs like SLAC, DESY and CERN. More recently, new high precision data at large x and in the resonance region have come from experiments at Jefferson Lab. These data, in combination with the earlier ones, allow us to study in detail the polarized parton densities, the Q^2 dependence of various moments of spin structure functions, the duality between deep inelastic and resonance data, and the nucleon structure in the valence quark region. Together with complementary data from HERMES, RHIC and COMPASS, we can put new limits on the flavor decomposition and the gluon contribution to the nucleon spin. In this report, we provide an overview of our present knowledge of the nucleon spin structure and give an outlook on future experiments. We focus in particular on the spin structure functions g_1 and g_2 of the nucleon and their momen...
Probing nuclear structure with nucleons; Sonder la structure nucleaire avec des nucleons
Energy Technology Data Exchange (ETDEWEB)
Bauge, E. [CEA Bruyeres-le-Chatel, Service de Physique Nucl aire, 91 (France)
2007-07-01
The goal of this lecture is to show how nucleon scattering can be used to probe the structure of target nuclei, and how nucleon scattering observables can be interpreted in terms of nuclear structure using microscopic optical potentials. After a brief overview of the specificities of nucleon-nucleus scattering, and a quick reminder on scattering theory, the main part of this lecture is devoted to the construction of optical potentials in which the target nuclei structure information is folded with an effective interaction. Several examples of such microscopic optical model potentials are given. (author)
Nucleon spin structure studies at COMPASS
Marchand, Claude
2006-01-01
One of the main goal of the COMPASS experiment at CERN is the study of the spin structure of the nucleon in DIS, by scattering 160 GeV polarized muon beam on a longitudinally (or transversely) polarized $^{6}$LiD target. Besides the scattered muon, the particles produced in the deep inelastic scattering are detected by a two stage magnetic spectrometer equipped with state of the art tracking and particle ID detectors. The emphasis of COMPASS muon program is the direct determination of the gluon polarization $\\Delta G/G$, accessed via asymmetries involving photon-gluon fusion mechanism (PGF). Both open charm production (detecting $D^{0}$s), as well as production of hight $p_{T}$ hadron pairs are used to tag PGF. Preliminary results for $\\Delta G/G$ based on the analysis of 2002 and 2003 data are shown. In addition, improved measurement of the deuteron structure function $g^{d}_{1}$ at small $x$, as well as studies of transverse distribution functions in the deuteron by measuring Collins and Sivers azimuthal...
Nucleon Spin Structure: Longitudinal and Transverse
Energy Technology Data Exchange (ETDEWEB)
Jian-Ping Chen
2011-02-01
Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction. The transverse spin structure and the TMDs are the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has played a major role in the worldwide effort to study both the longitudinal and transverse spin structure. Highlights of recent results will be presented. With 12-GeV energy upgrade, JLab will provide the most precise measurements in the valence quark region to close a chapter in longitudinal spin study. JLab will also perform a multi-dimensional mapping of the transverse spin structure and TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space and extracting the u and d quark tensor charges of the nucleon. The precision mapping of TMDs will also allow a detailed study of the quark orbital motion and its dynamics.
Nucleon structure and the chiral filter
International Nuclear Information System (INIS)
I discuss the issues of quenched gA in nuclei, pionic enhancement of nuclear electromagnetic form factors, manifestation of the anomalous Wess-Zumino term in nuclear medium, all on the same footing, in terms of the nucleon structure as 'derived' from a low-energy effective theory of QCD
International Nuclear Information System (INIS)
We summarize recent developments in the understanding of nucleon structure. New data on F2, R and Fcantic2, over a wide range of Q2 (from 104GeV2 down to 0.1 GeV2) and x (down to 10-6), are described. Conventional leading twist NLO perturbative QCD gives an excellent description of all the new data with Q2 above a GeV, leaving very little room for either higher twists or higher logarithms. We summarize the current status of NLO fits, and the determination of the gluon distribution and the strong coupling constant from structure function data. Finally we consider some of the theoretical issues raised by the new data. (orig.)
Physicis of Q2-dependence in the nucleon's G1(x,Q2) structure function sum rule
International Nuclear Information System (INIS)
I discuss in this talk the physics of the Q2 dependence of the Gl(x,Q2) structure function sum rule. For Q2 > 3 GeV2, the Q2 variation is controlled by pure QCD radiative corrections. For 0.5 2 2, the twist-four contribution becomes significant, but stays perturbative. For Q2 below ? 0.05, the sum rule is determined by low-energy theorems. The rapid change of the sum rule between 0.05 and 0.5 GeV2 signals the transition between parton and hadron degrees of freedom
Nucleon structure and the high energy interactions
Selyugin, O. V.
2015-06-01
On the basis of the representation of the generalized structure of nucleons a new model of the hadron interaction at high energies is presented. A new t dependence of the generalized parton distributions is obtained from the comparative analysis of different sets of the parton distribution functions, based on the description of the entire set of experimental data for the electromagnetic form factors of the proton and neutron. Taking into account the different moments of the generalized parton distributions of the hadron, quantitative descriptions of all existing experimental data of the proton-proton and proton-antiproton elastic scatterings from ?{s }=9.8 GeV to 8 TeV, including the Coulomb range and large momentum transfers up to -t =15 GeV2 , are obtained with a few free high-energy fitting parameters. The real part of the hadronic elastic scattering amplitude is determined only through the complex s that satisfies the dispersion relations. The negligible contributions of the hard Pomeron and the presence of the non-small contributions of the maximal Odderon are obtained. The non-dying form of the spin-flip amplitude is examined as well. The structures of the Born term and unitarized scattering amplitude are analyzed. It is shown that the black disk limit for the elastic scattering amplitude is not reached at LHC energies. Predictions for LHC energies are made.
Relativistic Deuteron Structure Function
Melnitchouk, W; Schreiber, A. W.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
1994-01-01
We calculate the unpolarised deep inelastic structure function of a relativistic deuteron within a covariant framework. An exact treatment of nucleon off-shell effects is shown to give corrections to the widely-used convolution model, even in impulse approximation. Neglecting off-shell effects in the extraction of the neutron structure function from deuterium data introduces errors of order $1-2\\%$.
Nucleon structure and high energy interactions
Selyugin, O V
2015-01-01
On the basis of the representation of the generalized structure of nucleons a new model of the hadron interaction at high energies is presented. The new t-dependence of the generalized parton distributions (GPDs) is obtained from the comparative analysis of different sets of the parton distribution functions (PDFs), based on the description of the whole sets of experimental data of electromagnetic form factors of the proton and neutron. Taking into account the different moments of GPDs of the hadron the quantitative descriptions of all existing experimental data of the proton-proton and proton-antiproton elastic scattering from $\\sqrt{s} = 9.8$ GeV to $8$ TeV, including the Coulomb range and large momentum transfers up to $-t=15$ GeV$^2$, are obtained with a few free fitting high energy parameters. The real part of the hadronic elastic scattering amplitude is determined only through complex $s$ satisfying the dispersion relations. The negligible contributions of the hard Pomeron and the presence of the non-sm...
Structure and Spin of the Nucleon
Energy Technology Data Exchange (ETDEWEB)
Avakian, Harut A. [JLAB
2014-03-01
Parton distribution functions, describing longitudinal momentum, helicity and transversity distributions of quarks and gluons, have been recently generalized to account also for transverse degrees of freedom. Two new sets of more general distributions, Transverse Momentum Distributions and Generalized Parton Distributions, were introduced to describe transverse momentum and space distributions of partons. Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs) in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL). TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC), FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.
Nucleon spin structure at very high-x
Roberts, Craig D; Schmidt, Sebastian M
2013-01-01
Dyson-Schwinger equation treatments of the strong interaction show that the presence and importance of nonpointlike diquark correlations within the nucleon are a natural consequence of dynamical chiral symmetry breaking. Using this foundation, we deduce a collection of simple formulae, expressed in terms of diquark appearance and mixing probabilities, from which one may compute ratios of longitudinal-spin-dependent u- and d-quark parton distribution functions on the domain x =1. A comparison with predictions from other approaches plus a consideration of extant and planned experiments shows that the measurement of nucleon longitudinal spin asymmetries on x =1 can add considerably to our capacity for discriminating between contemporary pictures of nucleon structure.
Nucleon nonequilibrium distribution functions in relativistic heavy-ion collisions
International Nuclear Information System (INIS)
We investigate the evolution of the nucleon system created in relativistic nucleus-nucleus collision, but we parameterize this development by the number of collisions of every particle during evolution rather than by the time variable. It is assumed that the group of nucleons which leave the system after the same number of collisions can be joined in a particular statistical ensemble. The nucleon nonequilibrium distribution function which depends on a certain number of collisions of a nucleon before freeze-out is derived. The collision smearing of the nucleon momenta about their initial values during nucleus-nucleus collisions is investigated
The nucleon spin structure in a simple quark model
Ma, B Q; Yang Jian Jun; Ma, Bo-Qiang; Schmidt, Ivan; Yang, Jian-Jun
2000-01-01
We investigate the spin structure of the nucleon in an extended Jaffe-Lipkin quark model. In addition to the conventional $3q$ structure, different $(3q)(Q\\bar{Q})$ admixtures in the nucleon wavefunction are also taken into account. The contributions to the nucleon spin from various components of the nucleon wavefunction are discussed. The effect due to the Melosh-Wigner rotation is also studied.
Energy Technology Data Exchange (ETDEWEB)
Nasseripour, Rakhsha; Raue, Brian; Ambrozewicz, Pawel; Carman, Daniel; Amaryan, Moscov; Amaryan, Moskov; Anciant, Eric; Anghinolfi, Marco; Asavapibhop, Burin; Asryan, Gegham; Audit, Gerard; Auger, Thierry; Avagyan, Harutyun; Baghdasaryan, Hovhannes; Baillie, Nathan; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Baltzell, Nathan; Barrow, Steve; Battaglieri, Marco; Beard, Kevin; Bedlinskiy, Ivan; Bektasoglu, Mehmet; Bellis, Matthew; Benmouna, Nawal; Berman, Barry; Biselli, Angela; Blaszczyk, Lukasz; Bonner, Billy; Bouchigny, Sylvain; Boyarinov, Sergey; Bradford, Robert; Branford, Derek; Briscoe, William; Brooks, William; Burkert, Volker; Butuceanu, Cornel; Calarco, John; Careccia, Sharon; Casey, Liam; Cetina, Catalina; Chen, Shifeng; Cheng, Lu; Cole, Philip; Collins, Patrick; Coltharp, Philip; Cords, Dieter; Corvisiero, Pietro; Crabb, Donald; Crede, Volker; Dale, Daniel; Dashyan, Natalya; De Masi, Rita; De Vita, Raffaella; De Sanctis, Enzo; Degtiarenko, Pavel; Dennis, Lawrence; Deur, Alexandre; Dhuga, Kalvir; Dickson, Richard; Djalali, Chaden; Dodge, Gail; Doughty, David; Dragovitsch, Peter; Dugger, Michael; Dytman, Steven; Dzyubak, Oleksandr; Egiyan, Hovanes; Egiyan, Kim; Elfassi, Lamiaa; Elouadrhiri, Latifa; Eugenio, Paul; Fatemi, Renee; Fedotov, Gleb; Feldman, Gerald; Feuerbach, Robert; Forest, Tony; Fradi, Ahmed; Funsten, Herbert; Garcon, Michel; Gavalian, Gagik; Gevorgyan, Nerses; Gilfoyle, Gerard; Giovanetti, Kevin; Girard, Pascal; Girod, Francois-Xavier; Goetz, John; Gothe, Ralf; Gothe, Ralf; Griffioen, Keith; Guidal, Michel; Guillo, Matthieu; Guler, Nevzat; Guo, Lei; Gyurjyan, Vardan; Hafidi, Kawtar; Hakobyan, Hayk; Hanretty, Charles; Hardie, John; Heddle, David; Hersman, F.; Hicks, Kenneth; Hleiqawi, Ishaq; Holtrop, Maurik; Hu, Jicun; Hyde, Charles; Ilieva, Yordanka; Ireland, David; Ishkhanov, Boris; Isupov, Evgeny; Ito, Mark; Jenkins, David; Jo, Hyon-Suk; Johnstone, John; Joo, Kyungseon; Juengst, Henry; Kalantarians, Narbe; Kellie, James; Khandaker, Mahbubul; Kim, Kui; Kim, Kyungmo; Kim, Wooyoung; Klein, Andreas; Klein, Franz; Kossov, Mikhail; Krahn, Zebulun; Kramer, Laird; Kubarovsky, Valery; Kuhn, Joachim; Kuhn, Sebastian; Kuleshov, Sergey; Kuznetsov, Viacheslav; Lachniet, Jeff; Laget, Jean; Langheinrich, Jorn; Lawrence, David; Livingston, Kenneth; Lu, Haiyun; Lukashin, Konstantin; MacCormick, Marion; Manak, Joseph; Markov, Nikolai; Mattione, Paul; McAleer, Simeon; McKinnon, Bryan; McNabb, John; Mecking, Bernhard; Mestayer, Mac; Meyer, Curtis; Mibe, Tsutomu; Mikhaylov, Konstantin; Minehart, Ralph; Mirazita, Marco; Miskimen, Rory; Mokeev, Viktor; Moreno, Brahim; Moriya, Kei; Morrow, Steven; Moteabbed, Maryam; Mueller, James; Munevar Espitia, Edwin; Mutchler, Gordon; Nadel-Turonski, Pawel; Niccolai, Silvia; Niculescu, Gabriel; Niculescu, Maria-Ioana; Niczyporuk, Bogdan; Niroula, Megh; Niyazov, Rustam; Nozar, Mina; Osipenko, Mikhail; Ostrovidov, Alexander; Park, Kijun; Pasyuk, Evgueni; Paterson, Craig; Pereira, Sergio; Peterson, Gerald; Philips, Sasha; Pierce, Joshua; Pivnyuk, Nikolay; Pocanic, Dinko; Pogorelko, Oleg; Pozdnyakov, Sergey; Preedom, Barry; Price, John; Procureur, Sebastien; Prok, Yelena; Protopopescu, Dan; Qin, Liming; Riccardi, Gregory; Ricco, Giovanni; Ripani, Marco; Ritchie, Barry; Rosner, Guenther; Rossi, Patrizia; Rubin, Philip; Sabatie, Franck; Salamanca, Julian; Salgado, Carlos; Santoro, Joseph; Sapunenko, Vladimir; Sayre, Donald; Schumacher, Reinhard; Serov, Vladimir; Shafi, Aziz; Sharabian, Youri; Sharov, Dmitri; Shvedunov, Nikolay; Simionatto, Sebastio; Skabelin, Alexander; Smith, Elton; Smith, Lee; Sober, Daniel; Sokhan, Daria; Stavinsky, Aleksey; Stepanyan, Samuel; Stepanyan, Stepan; Stokes, Burnham; Stoler, Paul; Strakovski, Igor; Strauch, Steffen; Taiuti, Mauro; Taylor, Shawn; Tedeschi, David; Thoma, Ulrike; Thompson, Richard; Tkabladze, Avtandil; Tkachenko, Svyatoslav; Ungaro, Maurizio; Vineyard, Michael; Vlassov, Alexander; Wang,
2008-06-01
The first measurements of the polarized structure function $\\sigma_{LT'}$ for the reaction $p(\\vec e,e'K^+)\\Lambda$ in the nucleon resonance region are reported. Measurements are included from threshold up to $W$=2.05 GeV for central values of $Q^2$ of 0.65 and 1.00 GeV$^2$, and nearly the entire kaon center-of-mass angular range. $\\sigma_{LT'}$ is the imaginary part of the longitudinal-transverse response and is expected to be sensitive to interferences between competing intermediate s-channel resonances, as well as resonant and non-resonant processes. The results for $\\sigma_{LT'}$ are comparable in magnitude to previously reported results from CLAS for $\\sigma_{LT}$, the real part of the same response. An intriguing sign change in $\\sigma_{LT'}$ is observed in the high $Q^2$ data at $W\\approx 1.9$ GeV. Comparisons to several existing model predictions are shown.
Electromagnetic studies of nucleon and nuclear structure
International Nuclear Information System (INIS)
Important objectives of the group are the study of subatomic structure through experimental measurements and the interpretation of the data through modeling. The common theme that unifies the studies of strong interactions and hadronic systems is the effort to determine the electromagnetic response as completely as possible. The general approach is coincidence detection of exclusive final states and determination of the dependence on the spin variables using polarized beams and targets and outgoing nucleon polarimetry. Direct reaction and giant resonance studies of electron quasi-elastic scattering on 12C and 16O are reported, as well as work on nuclear structure models and instrumentation development
Exploring the nucleon structure from first principles of QCD
International Nuclear Information System (INIS)
Quantum Chromodynamics (QCD) is generally assumed to be the fundamental theory underlying nuclear physics. In recent years there is progress towards investigating the nucleon structure from first principles of QCD. Although this structure is best revealed in Deep Inelastic Scattering, a consistent analysis has to be performed in a fully non-perturbative scheme. The only known method for this purpose are lattice simulations. We first sketch the ideas of Monte Carlo simulations in lattice gauge theory. Then we comment in particular on the issues of chiral symmetry and operator mixing. Finally we present our results for the Bjorken variable of a single quark, and for the second Nachtmann moment of the nucleon structure functions. (orig.)
Internal Spin Structure of the Nucleon in Polarized Deep Inelastic Muon-Nucleon Scattering
International Nuclear Information System (INIS)
We present the study of the internal spin structure of the nucleon in spin-dependent deep inelastic scattering of muons on nucleons. The data were taken by the NA47 experiment of the Spin Muon Collaboration (SMC) on the high energy muon beam at CERN. The experiment used the polarized proton and deuteron targets. The structure function g1p(x) and g1d(x) were determined from the asymmetries of the spin-dependent event rates in the range of 0.0032>=10 GeV2. Using the first moments of these structure functions an agreement with the Bjorken sum rule prediction was found within one standard deviation. The first moments of g1(x), for both proton and deuteron, are smaller than the Ellis-Jaffe sum rule prediction. This disagreement can be interpreted in terms of negative polarization of the strange sea in the nucleon. The singlet part of the axial current matrix element can be interpreted as an overall spin carried by quarks in the nucleon. Its value is significantly smaller than nucleon spin. Semi-inclusive asymmetries of yields of positive and negative hadrons produced on both targets were also measured and analysed in term of quark-parton model, together with inclusive asymmetries. From this analysis the quark spin distributions were determined, separately for valence u and d quarks and for non-strange sea quarks. Valence u quarks are positively polarized and their polarization increases with x. Valence d quarks are negatively polarized and their polarization does not exhibit any x-dependence. The non-strange sea is unpolarized in the whole measured range of x. The first moments of the valance quark spin distributions were found consistent with the values obtained from weak decay constants F and D and their second moments are consistent with lattice QCD calculations. In the QCD analysis of the world data the first moment of the gluon spin distribution was found with a large error. Also, a search for a non-perturbative anomaly at high x was done on the world data and the result was consistent with null. An extensive discussion of the SMC results and a comparison with results of SLAC experiment is presented. The new experiment of the COMPASS Collaboration, approved and being currently in preparation at CERN, was presented. The main physics issues of the muon part of this experiment, which are the gluon polarization and a continuation of the physics program of the SMC, were discussed. (author)
Future exploration of the nucleon structure at COMPASS
International Nuclear Information System (INIS)
Up to now, COMPASS experiment essentially focussed, in it's program with muon beams, on studying aspects of the longitudinal momentum structure of the nucleon in the collinear approximation, like ?q(x) and ?G/G(x). However, quarks can also have intrinsic transverse momentum in the nucleon, which give rise to a new class of Transverse Momentum Distribution (TMD) Parton Distribution Functions. As an example, Sievers function has been measured by both COMPASS and HERMES to be non zero on the proton, paving thus the way for more precise investigations. It is precisely the goal of the new COMPASS phase II proposal to investigate in more detail new transverse description of the nucleon structure. Deeply Virtual Compton Scattering (DVCS) will allow studies in the transverse space via Generalized Parton Distributions (GPDs). Transverse Mometum Dependent PDFs will essentially be studied in Drell-Yan (DY) reaction and SIDIS, and some universality arguments in QCD imply different signs for Sievers and Boer-Mulders functions in DY and SIDIS.
Flavor and Spin Dependent Structure of the Nucleon and Meson
Mirjalili, Abolfazl; Keshavarzian, Kianoosh; Yazdanpanah, Mohammad Mehdi
We employ the polarized chiral constituent quarks to extract the polarized structure function of the nucleon. The polarized valon model is used to calculate the spin dependence of parton distribution functions of meson. The connection between the polarized structure of the proton and the Goldstone bosons, using the chiral quark model (?QM) is analyzed and the spin dependence of the parton distribution functions for pion and kaon, is obtained thoroughly. These functions are evolved to high Q2 values, using the singlet, nonsinglet and quark-gluon moments (?MS, ?MNS, ?Mgq) which are convoluted with the polarized valon distributions. The polarized valon distributions for meson are computed, based on a phenomenological method and a comparison between polarized and unpolarized parton distribution functions for pion and kaon are performed. As a consequence of the ?QM, the SU(3)f symmetry breaking for the spin dependent of the nucleon sea distributions is achieved. The required polarized parton distributions of the proton will be obtained from the parton distribution functions of the polarized meson via the related convolution integral which are existed in the ?QM. Following that the analytical result for the proton's spin structure function, xgp1(x), is obtained and compared with experimental data. Finally, the parton orbital angular momentum of meson are introduced and the total spin of the meson, based on this quantity and the first moment of distributions for gluon and singlet sectors, are obtained.
Nucleon wave function from lattice QCD
International Nuclear Information System (INIS)
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Nucleon wave function from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Warkentin, Nikolaus
2008-04-15
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Nucleon-nucleon scattering in the functional quantum theory of the nonlinear spinor field
International Nuclear Information System (INIS)
The author calculates the S matrix for the elastic nucleon-nucleon scattering in the lowest approximation using the quantum theory of nonlinear spinor fields with special emphasis to the ghost configuration of this theory. Introducing a general scalar product a new functional channel calculus is considered. From the results the R and T matrix elements and the differential and integral cross sections are derived. (HSI)
Scaling Function, Spectral Function and Nucleon Momentum Distribution in Nuclei
Antonov, A N; Caballero, J A; Barbaro, M B; Udias, J M; de Guerra, E Moya; Donnelly, T W
2011-01-01
The link between the scaling function extracted from the analysis of (e,e') cross sections and the spectral function/momentum distribution in nuclei is revisited. Several descriptions of the spectral function based on the independent particle model are employed, together with the inclusion of nucleon correlations, and effects of the energy dependence arising from the width of the hole states are investigated. Although some of these approaches provide rough overall agreement with data, they are not found to be capable of reproducing one of the distinctive features of the experimental scaling function, namely its asymmetry. However, the addition of final-state interactions, incorporated in the present study using either relativistic mean field theory or via a complex optical potential, does lead to asymmetric scaling functions in accordance with data. The present analysis seems to indicate that final-state interactions constitute an essential ingredient and are required to provide a proper description of the ex...
Nucleon structure function at small ?
International Nuclear Information System (INIS)
This is a status report on the behaviour of deeply inelastic scattering in the low x region, where a new physics to be expected. It is bound to be theoretical review, since there is no data available at truely small values of x, say x -3. New data from HERA are anticipated and I am viewing on this talk as summary of the theoretical situation in the region of small x, as is just before this new area of physics will be studied experimentally. This is an extended version of the talk which was presented at EP-HEP 91 Conference. (orig.)
Structure and spin of the nucleon
Directory of Open Access Journals (Sweden)
Avakian H.
2014-03-01
Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL. TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC, FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.
International Nuclear Information System (INIS)
This review focuses on the discussion of three key results of nucleon structure calculations on the lattice. These three results are the quark contribution to the nucleon spin, Jq, the nucleon-? transition form factors, and the nucleon axial coupling, gA. The importance for phenomenology and experiment is discussed and the requirements for future simulations are pointed out. (orig.)
Nucleon structure in the search for new physics
Young, Ross D
2011-01-01
We report on recent results on nucleon structure that are helping guide the search for new physics at the precision frontier. Results discussed include the electroweak elastic form factors, charge symmetry breaking in parton distributions and the strangeness content of the nucleon.
Nuclear energy density functional from chiral two-nucleon aaand three-nucleon interactions
Holt, J. W.; Kaiser, N.; Weise, W.
2011-10-01
An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading-order chiral three-nucleon interaction with its parameters c E , c D and c 1,3,4 fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions F ?( ?) and F so ( ?) of the surface and spin-orbit terms compare in the relevant density range reasonably with the results of phenomenological Skyrme forces. However, an improved description requires (at least) the treatment of the two-body interaction to second order. This observation is in line with the deficiencies in the nuclear matter equations of state bar E(? ) that remain in the Hartree-Fock approximation with low-momentum two- and three-nucleon interactions.
Nuclear energy density functional from chiral two-nucleon and three-nucleon interactions
Energy Technology Data Exchange (ETDEWEB)
Holt, J.W.; Kaiser, N.; Weise, W. [Technische Universitaet Muenchen, Physik Department, Garching (Germany)
2011-10-15
An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading-order chiral three-nucleon interaction with its parameters c{sub E}, c{sub D} and c{sub 1,3,4} fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions F{sub {nabla}}({rho}) and F{sub so} ({rho}) of the surface and spin-orbit terms compare in the relevant density range reasonably with the results of phenomenological Skyrme forces. However, an improved description requires (at least) the treatment of the two-body interaction to second order. This observation is in line with the deficiencies in the nuclear matter equations of state anti E({rho}) that remain in the Hartree-Fock approximation with low-momentum two- and three-nucleon interactions. (orig.)
Quark Distributions and Nucleon Spin Structure
Khorramian, Ali N.; Mirjalili, A.; Tehrani, S. Atashbar
In this paper we calculate spin dependence of parton distributions and proton structure function. The polarized valon distributions in a proton and the polarized parton distributions inside the valon are necessary to obtain the polarized parton distributions in a proton. The results of our calculations for the proton structure function, xg1p are in good agreement with the available experimental data. We obtain the spin contribution and angular momentum of the valons to the proton.
Nuclear interaction and quark structure of nucleons
International Nuclear Information System (INIS)
We discuss a procedure to construct the nucleon image of a quark operator in a non-relativistic approach. The procedure is based on the concept of mapping and establishes a correspondence between a space of three-quark clusters and a space of elementary nucleons. As an example, we search for the nucleon image of a quark hamiltonian proposed by Oka and Yazaki. The nucleon hamiltonian is hermitian, non-local and N-body (if N is the number of clusters under consideration). We construct the two-body term of this hamiltonian and search for a local effective-interaction equivalent in a harmonic-oscillator basis to the quark-derived hamiltonian. (orig.)
Boson-exchange nucleon-nucleon potential and nuclear structure
International Nuclear Information System (INIS)
A fully momentum-dependent one-boson-exchange potential is derived which takes into account the mesons, ?, eta, sigma, rho, ? and phi. Scattering bound states and nuclear matter properties are studied in momentum space. The use of such potential is shown to be as easy as the use of more simple phenomenological interactions. In nuclear matter the formalism of Bethe-Goldstone is chosen to compute the binding energy versus density in the approximation of two-body and three-body correlations. The three-body correlated wave function obtained is then used
Spin- and flavor-structure of nucleons and nuclei
International Nuclear Information System (INIS)
Lepton scattering on nuclear targets is used to study the spin and flavor structure of nucleons. Nuclear physics effects, which either enhance or limit one's ability to view the distribution of quarks and gluons inside nucleons are pointed out. Semi-leptonic scattering is studied with a brief discussion of Drell-Yan processes. A discussion of nucleon strangeness is given. Polarized deep inelastic scattering and the Gottfried sum are discussed. A review of past, present, and future experimental efforts aimed at probing spin- and flavor-structure is also presented. (K.A.). 89 refs., 11 figs., 2 tabs
Relativistic spectral function of nucleons in hot nuclear matter
International Nuclear Information System (INIS)
We present a simple calculation of the nucleon self-energy in nuclear matter at finite temperature in a relativistic framework, using the real-time thermal field theory. The imaginary parts of one-loop graphs are identified with discontinuities across the unitary and the Landau cuts. We find that in general both the cuts contribute significantly to the spectral function in the region of (virtual) nucleon mass usually considered, even though the unitary cut is ignored in the literature. Furthermore, our relativistic spectral function differs from the one in nonrelativistic approximation, used in some earlier calculations.
International Nuclear Information System (INIS)
We measured the production of massive muon pairs on a platinum target by pions of 200 and 280 GeV/c. The following number of dimuon events have been collected for M > 4 GeV/c2. (a) ?- of 200 GeV/c: approx. 5900 events; (b) ?+ of 200 GeV/c: approx. 2200 events; (c) ?- of 280 GeV/c: approx. 5700 events. These data were analysed in terms of the Drell-Yan model in order to obtain the pion and nucleon structure functions, which are parametrised with expressions of the form xsup(?)(1 - x)sup(?). Our results are compared to the structure functions obtained in other experiments. (orig.)
Study of excited nucleons and their structure
Energy Technology Data Exchange (ETDEWEB)
Burkert, Volker D. [JLAB, Newport News, VA (United States)
2014-01-01
Recent advances in the study of excited nucleons are discussed. Much of the progress has been achieved due to the availability of high precision meson production data in the photoproduction and electroproduction sectors, the development of multi-channel partial wave analysis techniques, and advances in Lattice QCD with predictions of the full excitation spectrum.
Nucleon spin structure and its connections to various sum rules
Soffer, J.
2004-01-01
Our knowledge on the nucleon spin structure has greatly improved over the last twenty years or so, but still many fundamental questions remain unsolved. I will try to review some of the puzzling aspects of the origin of the nucleon spin. I will emphasize the connection with several sum rules and, when using this tool, the relevance of some kinematic regions for testing them in the QCD dynamics framework.
Energy Technology Data Exchange (ETDEWEB)
Schroers, W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-01-15
This review focuses on the discussion of three key results of nucleon structure calculations on the lattice. These three results are the quark contribution to the nucleon spin, J{sub q}, the nucleon-{delta} transition form factors, and the nucleon axial coupling, g{sub A}. The importance for phenomenology and experiment is discussed and the requirements for future simulations are pointed out. (orig.)
Nuclear energy density functional from chiral pion-nucleon dynamics
International Nuclear Information System (INIS)
We calculate the nuclear energy density functional relevant for N=Z even-even nuclei in the framework of chiral perturbation theory. The calculation includes the one-pion exchange Fock diagram and the iterated one-pion exchange Hartree and Fock diagrams. From these few leading order contributions in the small momentum expansion one obtains already a good equation of state of isospin symmetric nuclear matter. We find that in the region below the nuclear matter saturation density the effective nucleon mass M-bar*(?) deviates by at most 15% from its free space value M, with 0.89M-3 and M-bar*(?)>M for higher densities. The parameterfree strength of the (???)2-term, F?(kf), is at saturation density comparable to that of phenomenological Skyrme forces. The magnitude of FJ(kf) accompanying the squared spin-orbit density J? 2 comes out considerably larger. The strength of the nuclear spin-orbit interaction, Fso(kf), as given by iterated one-pion exchange is about half as large as the corresponding empirical value, however, with the wrong negative sign. The novel density dependencies of M-bar*(?) and F?,so,J(kf) as predicted by our parameterfree (leading order) calculation should be examined in nuclear structure calculations (introducing at least an additional short range spin-orbit contribution constant in density)ution constant in density)
Experimental study of the nucleon spin structure
International Nuclear Information System (INIS)
After introducing the theoretical framework, which includes DIS, the Quark Parton Model (QPM) and QCD, we describe the implementation of the experiment. The SMC uses a beam of 190 GeV naturally polarized muons, scattering off nucleons in a large cryogenic target containing protons or deuterons that are polarized through Dynamic Nuclear Polarization (DNP). The target material is located in two cells in a row, with opposite polarizations. Every 5 hours the polarizations of both cells are reversed. The target polarization is measured by an NMR system. The polarization of the beam is measured in a polarimeter, located downstream of the main experimental setup. (orig.)
Experimental study of the nucleon spin structure
Energy Technology Data Exchange (ETDEWEB)
Litmaath, M.F.
1996-05-07
After introducing the theoretical framework, which includes DIS, the Quark Parton Model (QPM) and QCD, we describe the implementation of the experiment. The SMC uses a beam of 190 GeV naturally polarized muons, scattering off nucleons in a large cryogenic target containing protons or deuterons that are polarized through Dynamic Nuclear Polarization (DNP). The target material is located in two cells in a row, with opposite polarizations. Every 5 hours the polarizations of both cells are reversed. The target polarization is measured by an NMR system. The polarization of the beam is measured in a polarimeter, located downstream of the main experimental setup. (orig.).
Structure of nucleons at small distances
International Nuclear Information System (INIS)
We report here the observation of surprisingly simple behaviors in the massive-hadron-pair (m>2 GeV) production from proton-nucleon collisions. With a 28.6-GeV incident proton beam and a pair spectrometer to detect the hadrons, the measured cross section decreases like d2sigma/dxdmproportionale-5/subm/ and can be grouped into three groups: ?-+p; ?++?-, p+p, K-+p; and K-+?+, ?++p. Within a given group the yield is the same to plus-or-minus20%; different groups are separated by a factor of approx.10 from each other
Wakamatsu, Masashi
2014-01-01
It is now widely recognized that a key to unravel the nonperturbative chiral-dynamics of QCD hidden in the deep-inelastic-scattering observables is the flavor structure of sea-quark distributions in the nucleon. We analyze the flavor structure of the nucleon sea in both of the unpolarized and longitudinally polarized parton distribution functions (PDFs) within a single theoretical framework of the flavor SU(3) chiral quark soliton model (CQSM), which contains only one adjustable parameter $\\Delta m_s$, the effective mass difference between the strange and nonstrange quarks. A particular attention is paid to a nontrivial correlation between the flavor asymmetry of the unpolarized and longitudinally polarized sea-quark distributions and also to a possible particle-antiparticle asymmetry of the strange quark distributions in the nucleon. We also investigate the charge-symmetry-violation (CSV) effects in the parton distribution functions exactly within the same theretical framework, which is expected to provide u...
The spin structure of the nucleon
International Nuclear Information System (INIS)
The nucleon is a spin 1/2 particle. This spin can be decomposed into the contributions of its constituents: 1/2 equals 1/2*?? + ?g + Lq + Lg where the first term is the contribution from the spin of the quarks, the second term is the contribution from the spin of the gluons and Lq and Lg are the orbital momentum of the quark and the gluon respectively. The ?? contribution of the spin of quarks can be studied through polarized deep inelastic scattering (DIS). We introduce DIS and the so-called parton model and then turn to the case of polarized DIS in the inclusive and semi-inclusive cases. We also discuss how a third parton distribution, called transversity, appears together with the unpolarized and the longitudinally polarized (or helicity) ones. We show how the longitudinally polarized gluon distribution can be measured. Then we focus on the SMC and COMPASS experiments performed at CERN. SMC confirmed a previous result by showing that the contribution of the spin of the quark to the spin of the nucleon was small. SMC also performed a measurement on the deuterium in order to test, for the first time, the Bjorker sum rules, which is a fundamental prediction of quantum chromodynamics. The COMPASS experiment started collecting data in 2002. Its main objectives are the gluon polarization ?g/g and the so-called transversity. (A.C.)
The spin structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Le Goff, J.M
2005-02-15
The nucleon is a spin 1/2 particle. This spin can be decomposed into the contributions of its constituents: 1/2 equals 1/2*{delta}{sigma} + {delta}g + L{sub q} + L{sub g} where the first term is the contribution from the spin of the quarks, the second term is the contribution from the spin of the gluons and L{sub q} and L{sub g} are the orbital momentum of the quark and the gluon respectively. The {delta}{sigma} contribution of the spin of quarks can be studied through polarized deep inelastic scattering (DIS). We introduce DIS and the so-called parton model and then turn to the case of polarized DIS in the inclusive and semi-inclusive cases. We also discuss how a third parton distribution, called transversity, appears together with the unpolarized and the longitudinally polarized (or helicity) ones. We show how the longitudinally polarized gluon distribution can be measured. Then we focus on the SMC and COMPASS experiments performed at CERN. SMC confirmed a previous result by showing that the contribution of the spin of the quark to the spin of the nucleon was small. SMC also performed a measurement on the deuterium in order to test, for the first time, the Bjorker sum rules, which is a fundamental prediction of quantum chromodynamics. The COMPASS experiment started collecting data in 2002. Its main objectives are the gluon polarization {delta}g/g and the so-called transversity. (A.C.)
Delineating the polarized and unpolarized partonic structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Jimenez-Delgado, Pedro [JLAB
2015-03-01
Our latest results on the extraction of parton distribution functions of the nucleon are reported. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are given, including a careful treatment of hadronic and nuclear corrections, as well as results on the impact of present and future data in our understanding of the spin of the nucleon.
Electromagnetic structure of the nucleons in the Skyrme model
International Nuclear Information System (INIS)
The isoscalar electromagnetic structure of the nucleons is studied within the Skyrme model. The form factors are consistent with the assumption of rotating rigid charge distributions. The use of deuteron data to obtain the isoscalar form factor is discussed; available calculations indicate that the isoscalar charge distribution is consistent with the well-known dipole fit. 8 refs.; 3 figs
International Nuclear Information System (INIS)
Understanding the nucleon structure is currently one of the main challenges encountered in nuclear physics. The present work represents a contribution to the study of the nucleon structure and deals, in particular, with the study of the role of strange quarks in the nucleon. The latter can be investigated by determining the strange quark distribution in the nucleon as well as the contribution of the spins of strange quarks to the nucleon spin. This work first presents a measurement of the nucleon spin performed via Deeply Inelastic Scattering (DIS) of a muon beam off polarized proton and deuterium targets. The result is found to be strongly dependent on the quark fragmentation functions into hadrons (FFs), which define the probability that a quark of a given flavour fragments into a final state hadron. The FFs are poorly known, in particular, the FF of strange quark into kaons, which play an important role in the determination of the nucleon spin. In deep inelastic scattering process, the access to the FFs is provided by the hadron multiplicities which, in turn, define the average number of hadrons produced per DIS event. Pion and kaon multiplicities have been extracted versus different kinematic variables, using DIS data collected by deeply inelastic scattering of a 160 GeV/c muons off a deuterium target. A first Leading Order (LO) extraction of the fragmentation functions has then been performed using the measured pion and kaon multiplicities. (author)
Fundamental nucleon-nucleon interaction: probing exotic nuclear structure using GEANIE at LANCE/WNR
International Nuclear Information System (INIS)
The initial goal of this project was to study the in-medium nucleon-nucleon interaction by testing the fundamental theory of nuclear structure, the shell model, for nuclei between 8Zr and 100Sn. The shell model predicts that nuclei with ''magic'' (2,8,20,28,40,50, and 82) numbers of protons or neutrons form closed shells in the same fashion as noble gas atoms [may49]. A ''doubly magic'' nucleus with a closed shell of both protons and neutrons has an extremely simple structure and is therefore ideal for studying the nucleon-nucleon interaction. The shell model predicts that doubly magic nuclei will be spherical and that they will have large first-excited-state energies (? 1 to 3 MeV). Although the first four doubly-magic nuclei exhibit this behavior, the N = Z = 40 nucleus, 80Zr, has a very low first-excited-state energy (290 keV) and appears to be highly deformed. This breakdown is attributed to the small size of the shell gap at N = Z = 40. If this description is accurate, then the N = Z = 50 doubly magic nucleus, 100Sn, will exhibit ''normal'' closed-shell behavior. The unique insight provided by doubly-magic nuclei from 80Zr to 100Sn has made them the focus of tremendous interest in the nuclear structure community. However, doubly-magic nuclei heavier than 56Ni become increasingly difficult to form due to the coulomb repulsion between the protons which favors the formation of neutron-rich nuclei. The coulomb repulsion creates a ''proton drip-line'' beyond which the addition of any additional bound protons is energetically impossible. The drip line renders the traditional experimental technique used in their formation, the heavy-ion reaction, less than ideal as a method of forming doubly-magic nuclei beyond 80Zr. The result has been a lack of an new spectroscopic information on doubly magic nuclei in more than a decade [lis87]. Furthermore, uncertainties in reaction dynamics modeling made it difficult for the nuclear science community to predict the cross section or forming these highly-neutron deficient nuclei. Therefore, we decided to try a new approach to forming highly-neutron deficient nuclei with the hope of both gaining spectroscopic information for nuclei near 100Sn, and also gaining insight into reaction dynamics at high (Ex > 200 MeV) incident nucleon energy
Chiral Symmetry and the Intrinsic Structure of the Nucleon
Leinweber, D. B.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia); Young, R.D.(ARC Centre of Excellence for Particle Physics at the Terascale, CSSM, School of Chemistry and Physics, University of Adelaide, Adelaide, SA, 5005, Australia)
2001-01-01
Understanding hadron structure within the framework of QCD is an extremely challenging problem. In order to solve it, it is vital that our thinking should be guided by the best available insight. Our purpose here is to explain the model independent consequences of the approximate chiral symmetry of QCD for two famous results concerning the structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of the proton to...
International Nuclear Information System (INIS)
Using the structure functions F2 measured in E.M.C., we have extracted the following values for the QCD scale parameter ?, at next to leading order: hydrogen target: ?sub(MS) = 139(+170-100)MeV; iron target: ?sub(MS) = 170(+160-100)MeV we have performed a study of the 1/Q2 effects on the Q2 domain covered by SLAC and E.M.C. We have extracted the ratio R = sigma sub(L)/sigma sub(T) for various chi bins and compared it with other experimental values and theoretical predictions. The mean value = 0+-.15 was found and is compatible with zero
Sum Rules for Nucleon GPDs and Border Function Formulation
Radyushkin, A V
2013-01-01
The newy developed approach to model nucleon generalized parton distributions (GPDs) H and E$ is based on two types of their representation in terms of double distributions. Within this approach, we re-consider the derivation of GPD sum rules that allow to use border functions H(x,x) and E(x,x) instead of full GPDs H(x,\\xi) and E(x,\\xi) in the integrals producing Compton form factors of deeply virtual Compton scattering. Using factorized DD Ansatz to model GPDs, we discuss the relation between the border functions and underlying parton densities. We find that a substantial contribution to H(x,x) border function comes from the extra term required by new DD representations and related to E(x,\\xi) GPD.
Nucleon structure in a light-front quark model consistent with quark counting rules and data
Gutsche, Thomas; Schmidt, Ivan; Vega, Alfredo
2014-01-01
Using global fits of valence u and d quark parton distributions and data on quark and nucleon form factors in the Euclidean region, we derive a light-front quark model for the nucleon structure consistent with quark counting rules.
Transverse spin structure of the nucleon from lattice QCD simulations
International Nuclear Information System (INIS)
We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72 (2005) 094020], we predict that the Boer-Mulders-function h1perpendicularto, describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks. (orig.)
Feasibility studies for nucleon structure measurements with PANDA
Directory of Open Access Journals (Sweden)
Atomssa Ermias
2014-01-01
Full Text Available The study of nucleon structure is one of the main physics goals of PANDA to be built at the FAIR accelerator complex. The excellent particle identification performance of the PANDA detector will enable measurements of exclusive channels p? p ? e+e? and p? p ? ?0 J/? ? ?0e+e? to extract the electromagnetic form factors of protons and ?-nucleon Transition Distribution Amplitudes (?-N TDAs. After a brief description of the PANDA apparatus and a method to handle momentum resolution degradation due to Bremsstrahlung, the physics of ?-N TDAs is discussed. An estimate for the expected signal to background ratio for p? p ? ?0 J/? ? ?0e+e? that takes into account the main background source is given.
Covariant nucleon wave function with S, D, and P-state components
Gross, Franz; Pena, M T
2012-01-01
Expressions for the nucleon wave functions in the covariant spectator theory (CST) are derived. The nucleon is described as a system with a off-mass-shell constituent quark, free to interact with an external probe, and two spectator constituent quarks on their mass shell. Integrating over the internal momentum of the on-mass-shell quark pair allows us to derive an effective nucleon wave function that can be written only in terms of the quark and diquark (quark-pair) variables. The derived nucleon wave function includes contributions from S, P and D-waves.
Covariant nucleon wave function with S, D, and P-state components
Energy Technology Data Exchange (ETDEWEB)
Franz Gross, G. Ramalho, M. T. Pena
2012-05-01
Expressions for the nucleon wave functions in the covariant spectator theory (CST) are derived. The nucleon is described as a system with a off-mass-shell constituent quark, free to interact with an external probe, and two spectator constituent quarks on their mass shell. Integrating over the internal momentum of the on-mass-shell quark pair allows us to derive an effective nucleon wave function that can be written only in terms of the quark and diquark (quark-pair) variables. The derived nucleon wave function includes contributions from S, P and D-waves.
Nuclear Parton Densities and Structure Functions
Tehrani, S. Atashbar; Khorramian, Ali N.; Mirjalili, A.
2004-01-01
We calculate nuclear parton distribution functions (PDFs), using the constituent quark model. We find the bounded valon distributions in a nuclear to be related to free valon distributions in a nucleon. By using improved bounded valon distributions for a nuclear with atomic number $A$ and the partonic structure functions inside the valon, we can calculate the nuclear structure function in $x$ space. The results for nuclear structure-function ratio $F_2^A/F_2^D$ at some value...
Gauge invariance, canonical quantization and Poincare covariance in nucleon structure
International Nuclear Information System (INIS)
There are different quark and gluon momentum, spin and orbital angular momentum operators used in the study of nucleon structure. We analyze the physical contents of these operators and propose a new set of operators based on gauge invariance principle, canonical quantization rule and Poincare covariance. Atomic structure is a simpler testing ground of these operators and has been analyzed together. These new operators are the gauge invariant version of the gauge non-invariant canonical version used in physics since the establishment of quantum mechanics and reduce to the familiar canonical ones in Coulomb gauge. (author)
Nuclear energy density functional from chiral pion-nucleon dynamics
Kaiser, N; Weise, W
2003-01-01
We calculate the nuclear energy density functional relevant for N=Z even-even nuclei in the systematic framework of chiral perturbation theory. The calculation includes the one-pion exchange Fock diagram and the iterated one-pion exchange Hartree and Fock diagrams. From these few leading order contributions in the small momentum expansion one obtains already a very good equation of state of isospin symmetric nuclear matter. We find that in the region below nuclear matter saturation density the effective nucleon mass $\\widetilde M^*(\\rho)$ deviates by at most 15% from its free space value $M$, with $0.89MM$ for higher densities. The parameterfree strength of the $(\\vec\
Nuclear energy density functional from chiral pion-nucleon dynamics
Energy Technology Data Exchange (ETDEWEB)
Kaiser, Norbert; Weise, Wolfram [Physik-Department, Technische Universitaet Muenchen, Garching (Germany)
2010-07-01
We use a recently improved density-matrix expansion (B. Gebremariam, T. Duguet, S.K. Bogner, nucl-th:0910.4979) to calculate the nuclear energy density functional in chiral perturbation theory. Our calculation treats systematically the effects from 1{pi}-exchange, iterated 1{pi}-exchange, and irreducible 2{pi}-exchange with intermediate {delta}-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass M{sup *}({rho}) is identical to the one of Fermi-liquid theory. The strength F{sub {nabla}}({rho}) of the (vector {nabla}{rho}){sup 2} surface-term as provided by the pion-exchange dynamics is in good agreement with that of phenomenological Skyrme forces in the density region {rho}{sub 0}/2 <{rho}< {rho}{sub 0}. The spin-orbit coupling strength F{sub so}({rho}) receives contributions from iterated 1{pi}-exchange (of the ''wrong sign'') and from three-nucleon interactions mediated by 2{pi}-exchange with virtual {delta}-excitation (of the ''correct sign''). In the region around {rho}{sub 0}/2 {approx_equal}0.08 fm{sup -3} where the spin-orbit interaction in nuclei gains most of its weight these two components tend to cancel, thus leaving all room for the short-range spin-orbit interaction. The strength function F{sub J}({rho}) multiplying the squared spin-orbit density vector J{sup 2} is also studied.
From Constituent Quark to Hadron Structure in the Next-to-Leading Order Nucleon and Pion
Arash, F; Arash, Firooz; Khorramian, Ali Naghi
2000-01-01
We calculate the partonic structure of constituent quark in the Next-to-Leading Order for the first time. The structure of any hadron can be obtained thereafter using a convolution method. Such a procedure is used to generate the structure function of proton and pion in NLO. It is shown that while the constituent quark structure is generated purely perturbatively and accounts to most part of the hadronic structure, there is a few percent contributions coming from the nonperturbative sector in the hadronic structure. This contribution plays the key role in explaining the SU(2) symmetry breaking of the nucleon sea and the observed violation of Gottfried sum rule. These effects are calculated. Excellent agreement with data in a wide range of $x=[10^{-6}, 1]$ and $Q^{2}=[0.5, 5000]$ $GeV^{2}$ is reached for proton structure function. We have also calculated Pion structure and compared it with the existing data. Again nice agreement is achieved.
International Nuclear Information System (INIS)
The soft-rotator model is applied for self-consistent analyses of the nuclear level structure and nucleon interaction data of 56Fe. The model succeeded in describing the experimental collective levels of 56Fe, which exhibited neither the typical rotational nor harmonic vibrational structure, up to an excitation energy of 5.5 MeV. The available nucleon interaction experimental data were described up to 160 MeV with reasonable accuracy in a coupled-channels optical model approach with coupling built using nuclear wave functions of the non-axial soft-rotator Hamiltonian model consistent with the nuclear structure of 56Fe
Polarized lepton-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
Hughes, E.
1994-02-01
Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions.
Polarized lepton-nucleon scattering
International Nuclear Information System (INIS)
Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions
Advances on statistical/thermodynamical models for unpolarized structure functions
Trevisan, Luis A.; Mirez, Carlos; Tomio, Lauro
2013-03-01
During the eights and nineties many statistical/thermodynamical models were proposed to describe the nucleons' structure functions and distribution of the quarks in the hadrons. Most of these models describe the compound quarks and gluons inside the nucleon as a Fermi / Bose gas respectively, confined in a MIT bag[1] with continuous energy levels. Another models considers discrete spectrum. Some interesting features of the nucleons are obtained by these models, like the sea asymmetries d/u and d-u.
Chiral Symmetry and the Intrinsic Structure of the Nucleon
Leinweber, D B; Young, R D
2001-01-01
Understanding hadron structure within the framework of QCD is an extremely challenging problem. In order to solve it, it is vital that our thinking should be guided by the best available insight. Our purpose here is to explain the model independent consequences of the approximate chiral symmetry of QCD for two famous results concerning the structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of the proton to neutron magnetic moments and the apparent success of the Foldy term in reproducing the observed charge radius of the neutron are coincidental. That is, a relatively small change of the current quark mass would spoil both results.
Nonsinglet spin-dependent structure functions
Energy Technology Data Exchange (ETDEWEB)
Khorramian, Ali N., E-mail: Khorramiana@theory.ipm.ac.i [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of); School of Particles and Accelerators, IPM (Institute for Studies in Theoretical Physics and Mathematics), P.O.Box 19395-5531, Tehran (Iran, Islamic Republic of); Atashbar Tehrani, S. [School of Particles and Accelerators, IPM (Institute for Studies in Theoretical Physics and Mathematics), P.O.Box 19395-5531, Tehran (Iran, Islamic Republic of); Olness, F. [Department of Physics, Southern Methodist University, Dallas, TX 75275-0175 (United States); Taheri Monfared, S. [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of); School of Particles and Accelerators, IPM (Institute for Studies in Theoretical Physics and Mathematics), P.O.Box 19395-5531, Tehran (Iran, Islamic Republic of); Arbabifar, F. [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of)
2010-10-15
We investigate the nonsinglet spin-dependent structure function for polarized deep inelastic scattering (DIS) of leptons on nucleons in the next-to-leading-order (NLO) approximation. We perform a fit to extract the polarized parton distribution functions (PPDFs) and the nonsinglet spin structure function using the most recent proton and neutron DIS data. We demonstrate that our results yield good agreement with available observables.
Nonsinglet spin-dependent structure functions
International Nuclear Information System (INIS)
We investigate the nonsinglet spin-dependent structure function for polarized deep inelastic scattering (DIS) of leptons on nucleons in the next-to-leading-order (NLO) approximation. We perform a fit to extract the polarized parton distribution functions (PPDFs) and the nonsinglet spin structure function using the most recent proton and neutron DIS data. We demonstrate that our results yield good agreement with available observables.
Shell-structure influence on the multinucleon transfer in nucleon transfer matrix elements
International Nuclear Information System (INIS)
Full text: An analysis of the experimental data on the charge (mass) distributions of products in nuclear reactions with heavy ions [1], dependence of yield of fragments on their isotope numbers and ones of projectile- and target nuclei [2], and cross sections of the formation of evaporation residues at synthesis of new superheavy elements [3] shows that the individual peculiarities (shell structure, N/Z-ratio) of interacting nuclei play decisive role at formation and evolution of dinuclear system. Therefore, the appropriate microscopic model should be used for the theoretical analysis of the above mentioned effects. The main quantities which must be included into model are the realistic scheme of single-particle states, nucleon separation energy, single-particle matrix elements of nucleon transitions in nuclei and nucleon exchange between them caused by influence of the mean-field of partner-nucleus. In this work the nucleon transfer matrix elements were calculated for the Wood-Saxon potential for spherical nucleus. The eigenvalues and wave functions of single-particle states were obtained by numerical solving Schroedinger's equation. The integral estimation of the matrix elements is found by comparing the calculated width of the charge distributions of the reaction products with the experimental data. In the early paper [4], the same matrix elements were calculated analytically using an approximation for wave functions: authors have used wave functions of the spherical potential well. The numerical values of squares of proton transfer matrix elements found in this work are nearly in coincidence with that presented in [4]. There is a difference between curves of dependencies of the matrix elements under discussion on the relative distance between centres of nuclei when this distance is smaller than sum of nuclei radii
Nucleon electromagnetic structure studies in the spacelike and timelike regions
Energy Technology Data Exchange (ETDEWEB)
Guttmann, Julia
2013-07-23
The thesis investigates the nucleon structure probed by the electromagnetic interaction. One of the most basic observables, reflecting the electromagnetic structure of the nucleon, are the form factors, which have been studied by means of elastic electron-proton scattering with ever increasing precision for several decades. In the timelike region, corresponding with the proton-antiproton annihilation into a electron-positron pair, the present experimental information is much less accurate. However, in the near future high-precision form factor measurements are planned. About 50 years after the first pioneering measurements of the electromagnetic form factors, polarization experiments stirred up the field since the results were found to be in striking contradiction to the findings of previous form factor investigations from unpolarized measurements. Triggered by the conflicting results, a whole new field studying the influence of two-photon exchange corrections to elastic electron-proton scattering emerged, which appeared as the most likely explanation of the discrepancy. The main part of this thesis deals with theoretical studies of two-photon exchange, which is investigated particularly with regard to form factor measurements in the spacelike as well as in the timelike region. An extraction of the two-photon amplitudes in the spacelike region through a combined analysis using the results of unpolarized cross section measurements and polarization experiments is presented. Furthermore, predictions of the two-photon exchange effects on the e{sup +}p/e{sup -}p cross section ratio are given for several new experiments, which are currently ongoing. The two-photon exchange corrections are also investigated in the timelike region in the process p anti p ? e{sup +}e{sup -} by means of two factorization approaches. These corrections are found to be smaller than those obtained for the spacelike scattering process. The influence of the two-photon exchange corrections on cross section measurements as well as asymmetries, which allow a direct access of the two-photon exchange contribution, is discussed. Furthermore, one of the factorization approaches is applied for investigating the two-boson exchange effects in parity-violating electron-proton scattering. In the last part of the underlying work, the process p anti p??{sup 0}e{sup +}e{sup -} is analyzed with the aim of determining the form factors in the so-called unphysical, timelike region below the two-nucleon production threshold. For this purpose, a phenomenological model is used, which provides a good description of the available data of the real photoproduction process p anti p?>?{sup 0}?.
Relationship between Feshbach's and Green's function theories of the nucleon-nucleus mean field
International Nuclear Information System (INIS)
We clarify the relationship and difference between theories of the optical-model potential which had previously been developed in the framework of Feshbach's projection operator approach to nuclear reactions and of Green's function theory, respectively. For definiteness, we consider the nucleon-nucleus system but all results can readily be adapted to the atomic case. The effects of antisymmetrization are properly taken into account. It is shown that one can develop along closely parallel lines the theories of open-quotes holeclose quotes and open-quotes particleclose quotes mean fields. The open-quotes holeclose quotes one-body Hamiltonians describe the single-particle properties of the system formed when one nucleon is taken away from the target ground state, for instance in knockout of pickup processes. The particle one-body Hamiltonians are associated with the system formed when one nucleon is elastically scattered from the ground state, or is added to it by means of stripping reactions. An infinite number of particle, as well as of hole, Hamiltonians are constructed which all yield exactly the same single-particle wave functions. Many open-quotes equivalentclose quotes one-body Hamiltonians can coexist because these operators have a complicated structure: they are nonlocal, complex, and energy-dependent. They do not have the same analytic properties in the complex energy plane. Their real and imaginary parts fulfill dispersion relations which may be different. It is shown that hole and particle Hamiltonians can also be constructed by decomposing any vector of the Hilbert space into two parts which are not orthogonal to one another, in contrast to Feshbach's original theory; one interest of this procedure is that the construction and properties of the corresponding hole Hamiltonian can be justified in a mathematically rigorous way. We exhibit the relationship between the hole and particle Hamiltonians and the open-quotes mass operator.close quotes
Nuclear Parton Densities and Structure Functions
Tehrani, S. Atashbar; Khorramian, Ali N.; Mirjalili, A.
We calculate nuclear parton distribution functions (PDFs), using the constituent quark model. We find the bounded valon distributions in a nuclear to be related to free valon distributions in a nucleon. By using improved bounded valon distributions for a nuclear with atomic number A and the partonic structure functions inside the valon, we can calculate the nuclear structure function in x space. The results for nuclear structure-function ratio F2A/F_2^D at some values of A, are in good agreement with the experimental data.
Nuclear Parton Densities and Structure Functions
Tehrani, S A; Mirjalili, A; Khorramian, Ali N.
2004-01-01
We calculate nuclear parton distribution functions (PDFs), using the constituent quark model. We find the bounded valon distributions in a nuclear to be related to free valon distributions in a nucleon. By using improved bounded valon distributions for a nuclear with atomic number $A$ and the partonic structure functions inside the valon, we can calculate the nuclear structure function in $x$ space. The results for nuclear structure-function ratio $F_2^A/F_2^D$ at some values of $A$ are in good agreement with the experimental data.
The role of nucleon structure in finite nuclei
Guichon, P.A.M.; Saito, K; Rodionov, E.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
1995-01-01
The quark-meson coupling model, based on a mean field description of non-overlapping nucleon bags bound by the self-consistent exchange of $\\sigma$, $\\omega$ and $\\rho$ mesons, is extended to investigate the properties of finite nuclei. Using the Born-Oppenheimer approximation to describe the interacting quark-meson system, we derive the effective equation of motion for the nucleon, as well as the self-consistent equations for the meson mean fields. The model is first applie...
Unpolarized structure functions at Jefferson Lab
Christy, M. E.; Melnitchouk, W
2011-01-01
Over the past decade measurements of unpolarized structure functions at Jefferson Lab with unprecedented precision have significantly advanced our knowledge of nucleon structure. These have for the first time allowed quantitative tests of the phenomenon of quark-hadron duality, and provided a deeper understanding of the transition from hadron to quark degrees of freedom in inclusive scattering. Dedicated Rosenbluth-separation experiments have yielded high-precision transvers...
A microscopic understanding of the structure functions of finite nuclei
International Nuclear Information System (INIS)
A number of relatively successful quark model descriptions of nuclear matter have recently been developed, based on a mean-field description of non-overlapping nucleon bags bound by the self-consistent exchange of scalar (?) and vector (?) mesons. The meson fields modify the internal quark motion in the nucleon bag in medium and this induces a saturation mechanism for nuclear matter. The model gives a nuclear compressibility around 220 MeV and provides a rather satisfactory interpretation of nuclear matter properties. Furthermore, it has recently been shown that the twist-2 valence quark distributions of the free nucleon calculated in the MIT bag model are in reasonable agreement with world data. By using a local density approximation we combine these developments to microscopically investigate the structure functions of finite nuclei. The effect of nuclear shadowing and antishadowing is taken into account phenomenologically. The model can quantitatively reproduce the existing experimental data - the so-called European Muon Collaboration (EMC) effect. We show that the quark degrees of freedom in nuclei and the final state interaction between the debris of the struck nucleon and the residual nucleus both play important roles in the nuclear structure functions. Thus the conventional treatment based on nucleon binding within the impulse approximation is quantitatively unreliable. We also study the effects of the self-coupling terms of the ? field and nucleon-nucleon correlations on some nuclear matter properties and the nuclear structure functions. ((orig.))
Polarized Structure Functions with Neutrino Beams
Forte, Stefano
2005-01-01
We review the potential impact of neutrino data on the determination of the spin structure of the nucleon. We show that a flavour decomposition of the parton structure of the nucleon as required by present-day precision phenomenology could only be achieved at a neutrino factory. We discuss how neutrino scattering data would allow a full resolution of the nucleon spin problem.
Nuclear energy density functional from chiral two- and three-nucleon interactions
Holt, J W; Weise, W
2011-01-01
An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading order chiral three-nucleon interaction with its parameters $c_E, c_D$ and $c_{1,3,4}$ fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions $F_\
Structure of dipole nucleon collective movement in atomic nuclei
International Nuclear Information System (INIS)
Atomic nuclei have different forms of dipole collective movement of nucleons. Here is a very known example - giant (isovector) dipole resonance that were predicted more than 40 years. Another form of dipole collective mode appears from valence nucleons. In Bose particle theory such a collective mode is described by means of s, p, d Bose particles. These Bose particles can be considered duplex nucleons images in the condition j?=0'+, 1-, 2+. If conditions with j?=0+ and j?=2+, are generated by means of identical nucleon coupling then conditions with j?=1- can occur by neutron/proton coupling. In the field of heavy nuclei valence neutrons and protons are at close by different parity energies conditions and strong neutron-proton interaction of these nucleon pairs in excited state generates collective movement of dipole nature. The fact that there is p-Bose particle freedom in atomic nuclei is confirmed by the following. In 210Bi (where there is one proton and neutron over 208Pb magic shell) 1- condition is basic and assigned
Spin structure of the nucleon and axial anomaly
International Nuclear Information System (INIS)
The gluon spin distribution function is shown to contribute to the spin structure of a proton via the axial anomaly. It modifies the original Ellis-Jaffe sum rule and can help in resolving the ''Spin Crisis''. The axial anomaly renormalization, the evolution equations and the connection of the quark content of the proton spin with the ?'-meson coupling constants are also considered. (orig.)
Structure functions extracted from muon pair production at the SPS
International Nuclear Information System (INIS)
Dimuon data provided by ?N interactions were analysed in the framework of the Drell-Yan quark fusion model in order to extract the pion and nucleon structure functions. Our results are compared to the structure functions obtained in other experiments
Nucleon Structure Including High Fock States in AdS/QCD Models
Vega, Alfredo; Schmidt, Ivan; Gutsche, Thomas; Lyubovitskij, Valery E.
2015-09-01
We discuss a holographic soft-wall model that consider several Fock states in nucleon description. In our approach nucleon structure is a superposition of a three-valence quark state with high Fock states including an adjustable number of partons (quarks, antiquarks and gluons). With a minimal number of free parameters (dilaton scale parameter, mixing parameters of partial contributions of Fock states, coupling constants in the effective Lagrangian) we achieve a reasonable agreement with data.
Hadronic Structure Functions from the Universal and the Basic Structures
Arash, F.
2005-04-01
It is shown that there is a basic structure common to all hadrons, which is generated perturbatively in QCD. Basically, it is a valence quark with its own cloud of quarks and gluons, a quasi-particle that we will call it a valon. In the valon representation, structure functions of nucleon and pion are calculated and is shown that there is an excellent agreement between the data and the model results in a wide range of kinematics. Calculation of the polarized structure functions also shows that there is a sizeable orbital angular momentum contribution to the spin of a valon coming from the partonic cloud.
Calculation of the pion-nucleon double spectral functions and applications
International Nuclear Information System (INIS)
In the present thesis the latest results from pion-pion and pion-nucleon phase analyses are applied in order to calculate the pion-nucleon double spectral functions which belong to the elastic unitarity in the t-channel. The equivalence of the partial wave projection of these spectral functions in the s-channel with the elastic t-channel unitarity is extensively discussed. After we summarize the aspects of the pion-nucleon system seeming in this connection interesting we discuss the Mandelstam method for the calculation of the spectral functions by means of the elastic t-channel unitarity as well as the applied input and present the results. Thereafter we use these results in order to calculate by means of a fixed t-channel dispersion relation the real parts of the t-channel cuts. Partial wave projections into the t-channel are proved as equivalent to the elastic t-channel unitarity. We study the compatibility of the asymptotic behaviour of the spectral functions relative to the energy with current Regge pole models. Finally we use our results in order to calculate the pion-nucleon partial waves by means of their Froissart-Gribov representations which follow from their analyticity at fixed energy. (orig./HSI)
Polarized Structure of Nucleon in the Valon Representation
Arash, Firooz; Taghavi-Shahri, Fatemeh
2007-01-01
We have utilized the concept of valon model to calculate the spin structure functions of proton, neutron and deuteron. The valon structure itself is universal and arises from the perturbative dressing of the valence quark in QCD. Our results agree rather well with all the relevant experimental data on $g_{1}^{p, n, d}$ and $g_{A}/g_{v}$, and suggests that the sea quark contribution to the spin of proton is consistent with zero. It also reveals that while the total quark cont...
Nuclear energy density functional from chiral two- and three-nucleon interactions
Holt, J. W.; Kaiser, N.; Weise, W.
2011-01-01
An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading order chiral three-nucleon interaction with its parameters $c_E, c_D$ and $c_{1,3,4}$ fixed in calculations of nuclear few-body systems. With ...
Recent results on the nucleon resonance spectrum and structure from the CLAS detector
Mokeev, Victor; Burkert, Volker; Gothe, Ralf
2015-01-01
The CLAS detector at Jefferson Lab has provided the dominant part of all available worldwide data on exclusive meson electroproduction off protons in the resonance region. New results on the $\\gamma_{v}pN^*$ transition amplitudes (electrocouplings) are available from analyses of the CLAS data and will be presented. Their impact on understanding of hadron structure will be discussed emphasizing the credible access to the dressed quark mass function that has been achieved for the first time by a combined analysis of the experimental results on the electromagnetic nucleon elastic and $N \\rightarrow N^*$ transition form factors. We will also discuss further convincing evidences for a new baryon state $N^{\\, '}(1720)3/2^+$ found in a combined analysis of charged double pion photo- and electroproduction cross sections off the protons.
Fixed Poles, Polarized Glue and Nucleon Spin Structure
International Nuclear Information System (INIS)
We review the theory and present status of the proton spin problem with emphasis on possible gluonic and sea contributions. We discuss the possibility of a J = 1 fixed pole correction to the Ellis - Jaffe sum rule for polarized deep inelastic scattering. Fixed poles in the real part of the forward Compton scattering amplitude have the potential to induce subtraction constant corrections to sum rules for photon-nucleon scattering. (author)
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
Kaiser, N.
2012-01-01
A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin-asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pio...
Searching for structure in nucleon-antinucleon interactions near threshold
International Nuclear Information System (INIS)
The purpose of this paper is to help make the case for a new machine being an antiproton factory as well as a kaon factory. The energy of such a high-intensity accelerator should be near 30 GeV, rather than the 15 GeV which would be adequate for the production of kaons as the most massive particle. Primarily, we wish to point out that there are regions of nucleon-antinucleon interactions which have not been carefully explored and which may contain interesting phenomena despite existing negative experiments
Impact of the recent Jefferson lab data on the structure of the nucleon
Scientific Electronic Library Online (English)
W.R.B. de, Arajo; T., Frederico; M., Beyer; H.J., Weber.
2004-03-01
Full Text Available The simultaneous fit of proton ratio m pG Ep/G Mp, qF2p/F1p to the recent experimental data and static properties of the nucleon is studied within a light-front model with different spin coupling schemes and wave functions. The position of the zero of proton electric form factor is sensitive to the [...] presence of a hard constituent quark component in the nucleon wave function. The fitting of the new data for the ratios is achieved with a hard momentum scale about 4-5 GeV.
Impact of the recent Jefferson lab data on the structure of the nucleon
International Nuclear Information System (INIS)
The simultaneous fit of proton ratio ?pGEp/GMp, qF2p/F1p to the recent experimental data and static properties of the nucleon is studied within a light-front model with different spin coupling schemes and wave functions. The position of the zero of proton electric form factor is sensitive to the presence of a hard constituent quark component in the nucleon wave function. The fitting of the new data for the ratios is achieved with a hard momentum scale about 4-5 GeV. (author)
Compton Scattering and the Spin Structure of the Nucleon at Low Energies
Hemmert, Thomas R.; Holstein, Barry R.; Kambor, Joachim; Knoechlein, Germar
1997-01-01
We analyze polarized Compton scattering which provides information on the spin-structure of the nucleon. For scattering processes with photon energies up to 100 MeV the spin-structure dependence can be encoded into four independent parameters-the so-called spin-polarizabilities $\\gamma_i, i=1...4$ of the nucleon, which we calculate within the framework of the "small scale expansion" in SU(2) baryon chiral perturbation theory. Specific application is made to "forward" and "ba...
Compton Scattering and the Spin Structure of the Nucleon at Low Energies
Hemmert, T R; Kambor, J; Knchlein, G; Hemmert, Thomas R.; Holstein, Barry R.; Kambor, Joachim; Knoechlein, Germar
1998-01-01
We analyze polarized Compton scattering which provides information on the spin-structure of the nucleon. For scattering processes with photon energies up to 100 MeV the spin-structure dependence can be encoded into four independent parameters-the so-called spin-polarizabilities gamma_i, i=1...4 of the nucleon, which we calculate within the framework of the "small scale expansion" in baryon chiral perturbation theory. Specific application is made to "forward" and "backward" spin-polarizabilities.
International Nuclear Information System (INIS)
The sigma term represents the quark contribution to the nucleon mass. It is useful for understanding the structure of the nucleon and is also a key parameter for precision experiments in particle physics and cosmology, which use nucleons as the target. However, the sigma term, in particular the strange quark contribution, has been only poorly determined by the standard analysis of the pion-nucleon scattering using the chiral perturbation theory. Therefore, the theoretical determination of the sigma term from the first principles of QCD has been awaited. Recently, owing to the development of lattice QCD with exact chiral symmetry by the JLQCD collaboration, a reliable determination of the sigma term is becoming possible for the first time. In this article, we introduce our study of the sigma term from the first principle based on our lattice QCD calculation. We also mention about the possible impact of our study to the dark matter direct detection experiment and flavor physics. (author)
Arrington, J.; Coester, F.; Holt, R J; Lee, T. -S. H.
2008-01-01
Neutron structure functions can be extracted from proton and deuteron data and a representation of the deuteron structure. This procedure does not require DIS approximations or quark structure assumptions. We find that the results depend critically on properly accounting for the Q^2 dependence of proton and deuteron data. We interpolate the data to fixed Q^2, and extract the ratio of neutron to proton structure functions. The extracted ratio decreases with increasing x, up t...
Study of two-nucleon wave functions in 3He
International Nuclear Information System (INIS)
The 3He(p,2p)pn reaction has been studied in a quasi-free scattering arrangement characterized by (anti) p(recoil) = 0 and various excitation or total energies E(recoil) of the unobserved p-n pair. Data were obtained at 250 and 400 MeV at symmetric and asymmetric pairs of angles. The 3He spectral function deduced in the framework of the plane wave impulse approximation is compared to the predictions of Faddeev and variational calculations. Comparisons are also made with p-n relative motion momentum distributions as the overlap between plane waves for the p-n pair and Irving, Irving-Gunn and Khanna wave functions for 3He
Gebremariam, B.; Bogner, S. K.; Duguet, T.
2011-02-01
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyrme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in arXiv:0910.4979 by Gebremariam et al. to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions at next-to-next-to-leading-order (N2LO). The structure of the chiral interactions is such that each coupling in the DME Fock functional can be decomposed into a coupling constant arising from zero-range contact interactions and a coupling function of the density arising from the universal long-range pion exchanges. This motivates a new microscopically-guided Skyrme phenomenology where the density-dependent couplings associated with the underlying pion-exchange interactions are added to standard empirical Skyrme functionals, and the density-independent Skyrme parameters subsequently refit to data. A link to a downloadable Mathematica notebook containing the novel density-dependent couplings is provided.
Energy Technology Data Exchange (ETDEWEB)
Gebremariam, B., E-mail: gebremar@gmail.co [National Superconducting Cyclotron Laboratory, 1 Cyclotron Laboratory, East-Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Bogner, S.K., E-mail: bogner@nscl.msu.ed [National Superconducting Cyclotron Laboratory, 1 Cyclotron Laboratory, East-Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Duguet, T., E-mail: thomas.duguet@cea.f [National Superconducting Cyclotron Laboratory, 1 Cyclotron Laboratory, East-Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); CEA, Centre de Saclay, IRFU/Service de Physique Nucleaire, F-91191 Gif-sur-Yvette (France)
2011-02-01
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyrme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in (arXiv:0910.4979) by Gebremariam et al. to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions at next-to-next-to-leading-order (N{sup 2}LO). The structure of the chiral interactions is such that each coupling in the DME Fock functional can be decomposed into a coupling constant arising from zero-range contact interactions and a coupling function of the density arising from the universal long-range pion exchanges. This motivates a new microscopically-guided Skyrme phenomenology where the density-dependent couplings associated with the underlying pion-exchange interactions are added to standard empirical Skyrme functionals, and the density-independent Skyrme parameters subsequently refit to data. A link to a downloadable Mathematica notebook containing the novel density-dependent couplings is provided.
Nucleon wave functions from lattice-gauge theories
International Nuclear Information System (INIS)
We present measurements of the matrix elements of certain 3-quark operators that gover the short-distance and light-cone properties of the proton wave function obtained on an 83x16 lattice at ? = 5.7 with Wilson fermions. Using these measurements we find the proton lifetime in the minimal SU(5) grand unified theory to be incompatible with the current experimental limits, in accord with another recent lattice calculation. (orig.)
Nuclear energy density functional from chiral pion-nucleon dynamics
Kaiser, N.; Fritsch, S.; Weise, W.
2002-01-01
We calculate the nuclear energy density functional relevant for N=Z even-even nuclei in the systematic framework of chiral perturbation theory. The calculation includes the one-pion exchange Fock diagram and the iterated one-pion exchange Hartree and Fock diagrams. From these few leading order contributions in the small momentum expansion one obtains already a very good equation of state of isospin symmetric nuclear matter. We find that in the region below nuclear matter sat...
Polarized Structure of Nucleon in the Valon Representation
Arash, Firooz
2007-01-01
We have utilized the concept of valon model to calculate the spin structure functions of proton, neutron and deuteron. The valon structure itself is universal and arises from the perturbative dressing of the valence quark in QCD. Our results agree rather well with all the relevant experimental data on $g_{1}^{p, n, d}$ and $g_{A}/g_{v}$, and suggests that the sea quark contribution to the spin of proton is consistent with zero. It also reveals that while the total quark contribution to the spin of valon is almost constant at $Q^{2}>=1$ the gluon contribution grows with the increase of $Q^2$ and hence requiring a sizable negative orbital angular momentum component $L_z$. This component along with the singlet and non-singlet parts are calculated in the Next-to-Leading order in QCD. We speculate that gluon contribution to the spin content of the proton is about 60% for all $Q^2$ values. Finally, we show that the size of gluon polarization and hence, $L_{z}$, is sensitive to the initial scale$Q_{0}^{2}$.
Polarized structure of nucleon in the valon representation
International Nuclear Information System (INIS)
We have utilized the concept of valon model to calculate the spin structure functions of proton, neutron, and deuteron. The valon structure itself is universal and arises from the perturbative dressing of the valence quark in QCD. Our results agree rather well with all of the relevant experimental data on g1p,n,d and gA/gV, and suggests that the sea quark contribution to the spin of proton is consistent with zero. It also reveals that while the total quark contribution to the spin of a valon, ??valon, is almost constant at Q2 ? 1 the gluon contribution grows with the increase of Q2 and hence requiring a sizable negative orbital angular momentum component Lz. This component along with the singlet and non-singlet parts are calculated in the Next-to-Leading order in QCD . We speculate that gluon contribution to the spin content of the proton is about 60% for all Q2 values. Finally, we show that the size of gluon polarization and hence, Lz, is sensitive to the initial scale Q02
Polarized structure of nucleon in the valon representation
Arash, Firooz; Taghavi-Shahri, Fatemeh
2007-07-01
We have utilized the concept of valon model to calculate the spin structure functions of proton, neutron, and deuteron. The valon structure itself is universal and arises from the perturbative dressing of the valence quark in QCD. Our results agree rather well with all of the relevant experimental data on g1p,n,d and gA/gV, and suggests that the sea quark contribution to the spin of proton is consistent with zero. It also reveals that while the total quark contribution to the spin of a valon, ??valon, is almost constant at Q2 >= 1 the gluon contribution grows with the increase of Q2 and hence requiring a sizable negative orbital angular momentum component Lz. This component along with the singlet and non-singlet parts are calculated in the Next-to-Leading order in QCD . We speculate that gluon contribution to the spin content of the proton is about 60% for all Q2 values. Finally, we show that the size of gluon polarization and hence, Lz, is sensitive to the initial scale Q02.
Nuclear energy density functional from chiral pion-nucleon dynamics revisited
Kaiser, N.; Weise, W.
2009-01-01
We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from $1\\pi$-exchange, iterated $1\\pi$-exchange, and irreducible $2\\pi$-exchange with intermediate $\\Delta$-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass $M^*(\\rho)$ entering the energy density ...
Recent COMPASS results on the nucleon longitudinal spin structure and QCD fits
Directory of Open Access Journals (Sweden)
Andrieux Vincent
2014-01-01
Full Text Available The latest measurements of the proton longitudinal spin structure function, ?1p, in the deep inelastic (DIS regime are presented. They improve the statistical accuracy of the existing data and extend the kinematic domain to a lower value of x and higher values of Q2. A global NLO QCD fit of all ?1 world data on the proton, deuteron and neutron has been achieved. The results give a quantification of the quark spin contribution to the nucleon spin, 0.26 < ?? < 0.34 at 3 (GeV/c2 in M?S? scheme. The errors are dominated by the uncertainty on the shape of the functional forms assumed in the fit. A new verification of the fundamental Bjorken sum rule is obtained at a 9% level, using only COMPASS ?1 proton and deuteron measurements. Preliminary results of a reevaluation of the gluon polarization ??/? are presented. The analysis is based on double spin asymmetry of high-pT hadron production cross-sections in the DIS regime. A positive value of ???/?? = 0.113 0.038 0.035 is obtained at leading order at x ~ 0.1. In parallel, the double spin asymmetry in the photoproduction regime is also studied. Finally, preliminary results on quark fragmentation functions into pions extracted from a LO fit of pion multiplicities in semi-inclusive DIS are presented.
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
Kaiser, N.
2012-03-01
A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading-order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value A( ? 0) ? 26.5 MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar coupling terms and in the relevant density range one finds agreement with phenomenological Skyrme forces. The specific isospin and density dependences arising from the chiral two- and three-nucleon interactions can be explored and tested in neutron-rich systems.
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
Energy Technology Data Exchange (ETDEWEB)
Kaiser, N. [Technische Universitaet Muenchen, Physik Department T39, Garching (Germany)
2012-03-15
A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading-order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value A({rho}{sub 0}) {approx_equal} 26.5 MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar coupling terms and in the relevant density range one finds agreement with phenomenological Skyrme forces. The specific isospin and density dependences arising from the chiral two- and three-nucleon interactions can be explored and tested in neutron-rich systems. (orig.)
Gebremariam, B; Duguet, T
2010-01-01
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in arXiv:0910.4979 by Gebremariam {\\it et al.} to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions at next-to-next-to-leading-order (N$^2$LO). The structure of the chiral interactions is such that each coupling in the DME Fock functional can be decomposed into a cutoff-dependent coupling {\\it constant} arising from zero-range contact interactions and a cutoff-independent coupling {\\it function} of the density arising from the universal long-range pion exchanges. This motivates a new microscopically-guided Skyrme phenomenology where the density-dependent couplings associated with the underlying pion-exchange interactions...
Nucleon structure in the chiral regime with domain wall fermions on an improved staggered sea
International Nuclear Information System (INIS)
Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The twist two matrix elements are calculated using a mixed action of domain wall valence quarks and asqtad staggered sea quarks and are renormalized perturbatively. Several observables are extrapolated to the physical limit using chiral perturbation theory. Results are compared with experimental moments of quark distributions and electromagnetic form factors and phenomenologically determined generalized form factors, and the implications on the transverse structure and spin content of the nucleon are discussed. (orig.)
Effect of nucleon and hadron structure changes in-medium and its impact on observables
Energy Technology Data Exchange (ETDEWEB)
K. Saito; K. Tsushima; A.W. Thomas
2005-07-05
We study the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model. The QMC model is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent exchange of scalar and vector mesons in the isoscalar and isovector channels. The model is extended to investigate the properties of finite nuclei, in which, using the Born-Oppenheimer approximation to describe the interacting quark-meson system, one can derive the effective equation of motion for the nucleon (or baryon), as well as the self-consistent equations for the meson mean fields.
Can a many-nucleon structure be visible in bremsstrahlung emission during $\\alpha$ decay?
Maydanyuk, Sergei P; Zou, Li-Ping
2015-01-01
We analyze if the nucleon structure of the $\\alpha$ decaying nucleus can be visible in the experimental bremsstrahlung spectra of the emitted photons which accompany such a decay. We develop a new formalism of the bremsstrahlung model taking into account distribution of nucleons in the $\\alpha$ decaying nuclear system. We conclude the following: (1) After inclusion of the nucleon structure into the model the calculated bremsstrahlung spectrum is changed very slowly for a majority of the $\\alpha$ decaying nuclei. However, we have observed that visible changes really exist for the $^{106}{\\rm Te}$ nucleus ($Q_{\\alpha}=4.29$ MeV, $T_{1/2}$=70 mks) even for the energy of the emitted photons up to 1 MeV. This nucleus is a good candidate for future experimental study of this task. (2) Inclusion of the nucleon structure into the model increases the bremsstrahlung probability of the emitted photons. (3) We find the following tendencies for obtaining the nuclei, which have bremsstrahlung spectra more sensitive to the ...
Nuclear energy density functional from chiral pion-nucleon dynamics revisited
Kaiser, N
2009-01-01
We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from $1\\pi$-exchange, iterated $1\\pi$-exchange, and irreducible $2\\pi$-exchange with intermediate $\\Delta$-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass $M^*(\\rho)$ entering the energy density functional is identical to the one of Fermi-liquid theory when employing the improved density-matrix expansion. The strength $F_\
McGraw, John T. (Placitas, NM); Zimmer, Peter C. (Albuquerque, NM); Ackermann, Mark R. (Albuquerque, NM)
2012-01-24
Methods and apparatus for a structure function monitor provide for generation of parameters characterizing a refractive medium. In an embodiment, a structure function monitor acquires images of a pupil plane and an image plane and, from these images, retrieves the phase over an aperture, unwraps the retrieved phase, and analyzes the unwrapped retrieved phase. In an embodiment, analysis yields atmospheric parameters measured at spatial scales from zero to the diameter of a telescope used to collect light from a source.
Purely Functional Structured Programming
Obua, Steven
2010-01-01
The idea of functional programming has played a big role in shaping today's landscape of mainstream programming languages. Another concept that dominates the current programming style is Dijkstra's structured programming. Both concepts have been successfully married, for example in the programming language Scala. This paper proposes how the same can be achieved for structured programming and PURELY functional programming via the notion of LINEAR SCOPE. One advantage of this ...
The Structure of the Nucleon and its Excited States
International Nuclear Information System (INIS)
The past year has been an exciting and productive one for particle physics research at Abilene Christian University. The thrust of our experimental investigations is the study of the nucleon and its excited states. Laboratories where these investigations are presently being conducted are the AGS at Brookhaven, Fermilab and LAMPF. Some analysis of the data for experiments at the Petersburg Nuclear Physics Institute (Gatchina, Russia) is still in progress. Scheduling of activities at different laboratories inevitably leads to occasional conflicts. This likelihood is increased by the present budget uncertainties at the laboratories that make long-term scheduling difficult. For the most part, the investigators have been able to avoid such conflicts. Only one experiment received beam time in 1994 (E890 at the AGS). The situation for 1995-1996 also appears manageable at this point. E890 and another AGS experiment (E909) will run through May, 1995. El 178 at LAMPF is presently scheduled for August/September 1995. E866 at Fermilab is scheduled to start in Spring/Summer 1996. Undergraduate student involvement has been a key element in this research contract since its inception. Summer students participated at all of the above laboratories in 1994 and the same is planned in 1995. A transition to greater involvement by graduate students will provide cohesiveness to ACU involvement at a given laboratory and full-time on-site involvement in the longer running experiments at FNAL and BNL. Funds to support a full-time graduate student are requested this year. Finally, collaboration by Russian, Croatian and Bosnian scientists has proven to be mutually beneficial to these experimental programs and to the overall programs at the institutions involved. Past support has been augmented by other grants from government agencies and from the Research Council at Abilene Christian University. Additional funds are requested in this renewal to enable more programmatic support for these efforts, so that long-range plans can be made to carry out the experiments and to perform the analysis
Chromatin Structure and Function
Wolffe, Alan P
1999-01-01
The Third Edition of Chromatin: Structure and Function brings the reader up-to-date with the remarkable progress in chromatin research over the past three years. It has been extensively rewritten to cover new material on chromatin remodeling, histone modification, nuclear compartmentalization, DNA methylation, and transcriptional co-activators and co-repressors. The book is written in a clear and concise fashion, with 60 new illustrations. Chromatin: Structure and Function provides the reader with a concise and coherent account of the nature, structure, and assembly of chromatin and its active
Photon structure function revisited
Berger, Ch
2014-01-01
The flux of papers from electron positron colliders containing data on the photon structure function ended naturally around 2005. It is thus timely to review the theoretical basis and confront the predictions with a summary of the experimental results. The discussion will focus on the increase of the structure function with x (for x away from the boundaries) and its rise with log Q**2, both characteristics beeing dramatically different from hadronic structure functions. Comparing the data with a specific QCD prediction a new determination of the QCD coupling coupling constant is presented. The agreement of the experimental observations with the theoretical calculations of the real and virtual photon structure is a striking success of QCD.
Neutron Structure Functions From Nuclear Data
Melnitchouk, W; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
1996-01-01
The spin-averaged structure function of the neutron, F_2^n, is extracted from recent deuteron data, taking into account the small but significant corrections due to nuclear effects in the deuteron. At small x, the F_2D/F_2p ratio measured by the New Muon and Fermilab E665 Collaborations is interpreted to suggest a small amount of shadowing in deuterium, which acts to enhance F_2^n for x < 0.1. A careful treatment of Fermi motion, binding and nucleon off-shell effects in the ...
International Nuclear Information System (INIS)
When the new data on polarised lepton nucleon scattering are compared at the same value of Q2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in O(?s), higher twist effects, modern data on unpolarised structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle. (author)
International Nuclear Information System (INIS)
Chiral theories with spontaneous symmetry breaking such as the Nambu-Jona-Lasinio (NJL) model lead to the existence of a scalar mode. We present in a detailed manner how the corresponding low-momentum effective Lagrangian involving the scalar field can be constructed starting from the NJL model. We discuss the relevance of the scalar mode for the problem of nuclear binding and saturation. We show that it depends on the nucleon mass origin with two extreme cases. If this origin is entirely due to confinement, the coupling of this mode to the nucleons vanishes, making it irrelevant for the nuclear binding problem. If instead it is entirely due to spontaneous symmetry breaking, it couples to the nucleons but nuclear matter collapses. It is only in the case of a mixed origin with spontaneous breaking that nuclear matter can be stable and reach saturation. We describe models of nucleon structure where this balance is achieved. We also show how chiral constraints and confinement modify the QCD sum rules for mass evolution in nuclear matter.
Neutron Structure Function and A=3 Mirror Nuclei
Afnan, I. R.; Bissey, F.; Gomez, J; Katramatou, A.T.; Melnitchouk, W; Petratos, G.G.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
2000-01-01
We investigate deep inelastic scattering from He-3 and H-3 within a conventional convolution treatment of binding and Fermi motion effects. Using realistic Faddeev wave functions together with a nucleon spectral function, we demonstrate that the free neutron structure function can be extracted in deep-inelastic scattering from A=3 mirror nuclei, with nuclear effects canceling to within 2% for x < 0.85.
Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces
Kaiser, N
2012-01-01
A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin-asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value $A(\\rho_0) \\simeq 26.5\\,$MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar...
Nuclear energy density functional from chiral pion-nucleon dynamics revisited
International Nuclear Information System (INIS)
We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from 1?-exchange, iterated 1?-exchange, and irreducible 2?-exchange with intermediate ?-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass M*(?) entering the energy density functional is identical to the one of Fermi-liquid theory when employing the improved density-matrix expansion. The strength F?(?) of the (???)2 surface-term as provided by the pion-exchange dynamics is in good agreement with that of phenomenological Skyrme forces in the density region ?0/20. The spin-orbit coupling strength Fso(?) receives contributions from iterated 1?-exchange (of the 'wrong sign') and from three-nucleon interactions mediated by 2?-exchange with virtual ?-excitation (of the 'correct sign'). In the region around ?0/2?0.08 fm-3 where the spin-orbit interaction in nuclei gains most of its weight these two components tend to cancel, thus leaving all room for the short-range spin-orbit interaction. The strength function FJ(?) multiplying the square of the spin-orbit density comes out much larger than in phenomenological Skyrme forces and it has a pronounced density dependeed density dependence.
Structure and direct nucleon decay properties of isoscalar giant monopole and dipole resonances
Energy Technology Data Exchange (ETDEWEB)
Gorelik, M. L.; Shlomo, S.; Urin, M. H.
2000-10-01
The strength function and partial widths for the direct nucleon decay of the isoscalar giant monopole and dipole resonances are analyzed within an extended continuum-random-phase-approximation approach. Calculations are performed for several medium and heavy mass nuclei with the use of a phenomenological nuclear mean field, the Landau-Migdal particle-hole interaction, and some partial self-consistency conditions. Calculation results are compared with available experimental data.
Progress in resolving charge symmetry violation in nucleon structure
Young, R.D.(ARC Centre of Excellence for Particle Physics at the Terascale, CSSM, School of Chemistry and Physics, University of Adelaide, Adelaide, SA, 5005, Australia); Shanahan, P. E.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
2013-01-01
Recent work unambiguously resolves the level of charge symmetry violation in moments of parton distributions using 2+1-flavor lattice QCD. We introduce the methods used for that analysis by applying them to determine the strong contribution to the proton-neutron mass difference. We also summarize related work which reveals that the fraction of baryon spin which is carried by the quarks is in fact structure-dependent rather than universal across the baryon octet.
Meson-nucleon scattering in the functional quantum theory of the non linear spinor field
International Nuclear Information System (INIS)
The results of this work are sumarized in the following points: 1. Determination of coupling constants, based on the nucleon eigenvalue equation with the two-point function, regularized by two single poles with small masses, gives a result deviating only little from the values given the theory with dipolar regularisation. These masses are considered here only as a means for regularisation and are not connected with physical particles. 2. The meson masses calculated are satisfying, too. So the two-point function, modified owing to the scalar product, has been shown to give equally good results for the calculation of coupling constants and mass eigenvalues. 3. In forward direction the differential cross section for pion-proton-scattering qualitively shows the correct behaviour. Indeed for back scattering a singularity exists which is characteristic for a theory with particles of zero mass. Thus ist seems necessary to first adapt the Greens function and to leave the unsymmetrical treatment of F and G. (orig.)
Chang, Yongbin
2009-04-01
In the kinetic theory of gases and plasmas, many integrals associated with Maxwellian velocity distribution such as collision frequencies, Rosenbluth's super potentials and arbitrary order of Fokker-Planck coefficients, can be reduced to the integrals R_n^{(\\ell)}(u) = \\frac{2}{ \\sqrt{\\pi}}\\int_{0}^{\\infty}\\!\\!\\int_{0}^{1} \\big[e^{-(y-ux)^2}\\pm e^{-(y+ux)^2}\\big]y^{n}x^{\\ell}\\,dx\\,dy. The usual approach to calculating the integrals is very tedious, particularly for large n and ell, and the results expressed in common elemental functions, including power, exponential and error functions, are complex. In this paper, R(ell)n(u) are calculated for arbitrary n and ell. The properties of the functions R(ell)n(u) are studied in detail and systematically. It was found that these functions have very simple properties. In many ways, they are much like common power functions un. Thus, R(ell)n(u) are referred to as structured power functions in this paper. With structured power functions, many physical results of arbitrary order can be presented in simple and meaningful expressions.
Mallot, Gerhard K.
1997-01-01
The experimental status of the spin-dependent structure functions as obtained from the deep inelastic scattering experiments at CERN, SLAC, and DESY is reviewed. All data show a violation of the Ellis-Jaffe sum rule. The Bjorken sum rule is found to be valid and is tested to the 10 % level.
Neutron structure function from nuclear data
Energy Technology Data Exchange (ETDEWEB)
Melnitchouk, W. [Dept. of Physics, Univ. of Maryland, College Park, MD (United States); Thomas, A.W. [Dept. of Physics and Mathematical Physics, Univ. of Adelaide, Adelaide (Australia)
1996-06-01
The spin-averaged structure function of the neutron, F{sub 2}{sup n}, is extracted from the latest deuteron data, taking into account the most recent developments in the treatment of nuclear effects in the deuteron. At small x, the F{sub 2}{sup D}/F{sub 2}{sup p} ratio measured by the New Muon and Fermilab E665 Collaborations is interpreted to suggest a small amount of shadowing in deuterium, which acts to enhance F{sub 2}{sup n} for x {approx}< 0.1. A careful treatment of Fermi motion, binding and nucleon off shell effects in the deuteron also indicates that the neutron/proton structure function ratio as x {yields} 1 is consistent with the perturbative QCD expectation of 3/7, but larger than the traditional value of 1/4. (author) 40 refs, 5 figs
NuN, ?N interactions: structure functions, higher twist
International Nuclear Information System (INIS)
Data on deep inelastic scattering of leptons by nucleons and nuclei have been accumulated for several years. Results exist from several experiments with electron, muon, neutrino beams. This talk reviews the most recent experiments which measured nucleon structure functions with nu and ? beams. In particular, the results on R = sigma/sub L//sigma/sub T/ measurement, on F2(x, Q2) and xF3(x, Q2), and their interpretation in terms of QCD, including both gluon radiation and higher twist phenomena are summarized
Global study of nuclear structure functions
International Nuclear Information System (INIS)
We present the results of a phenomenological study of unpolarized nuclear structure functions for a wide kinematical region of x and Q2. As a basis of our phenomenology we develop a model which takes into account a number of different nuclear effects including nuclear shadowing, Fermi motion and binding, nuclear pion excess and off-shell correction to bound nucleon structure functions. Within this approach we perform a statistical analysis of available data on the ratio of the nuclear structure functions F2 for different nuclei in the range from the deuteron to the lead. We express the off-shell effect and the effective scattering amplitude describing nuclear shadowing in terms of few parameters which are common to all nuclei and have a clear physical interpretation. The parameters are then extracted from statistical analysis of data. As a result, we obtain an excellent overall agreement between our calculations and data in the entire kinematical region of x and Q2. We discuss a number of applications of our model which include the calculation of the deuteron structure functions, nuclear valence and sea quark distributions and nuclear structure functions for neutrino charged-current scattering
Unified approach to structure factors and neutrino processes in nucleon matter
International Nuclear Information System (INIS)
We present a unified approach to neutrino processes in nucleon matter based on Landau's theory of Fermi liquids that includes one and two quasiparticle-quasihole pair states as well as mean-field effects. We show how rates of neutrino processes involving two nucleons may be calculated in terms of the collision integral in the Landau transport equation for quasiparticles. Using a relaxation time approximation, we solve the transport equation for density and spin-density fluctuations and derive a general form for the response functions. We apply our approach to neutral-current processes in neutron matter, where the spin response function is crucial to the calculation of neutrino elastic and inelastic scattering and neutrino-pair bremsstrahlung and absorption from strongly interacting nucleons. We calculate the relaxation rates using modern nuclear interactions and including many-body contributions, and find that rates of neutrino processes are reduced compared with estimates based on the one-pion exchange interaction, which is used in current simulations of core-collapse supernovae
Nuclear energy density functional from chiral pion-nucleon dynamics revisited
Kaiser, N.; Weise, W.
2010-05-01
We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from 1 ?-exchange, iterated 1 ?-exchange, and irreducible 2 ?-exchange with intermediate ?-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass M(?) entering the energy density functional is identical to the one of Fermi-liquid theory when employing the improved density-matrix expansion. The strength F(?) of the ( surface-term as provided by the pion-exchange dynamics is in good agreement with that of phenomenological Skyrme forces in the density region ?/2Skyrme forces and it has a pronounced density dependence.
Deep Inelastic Structure Functions in a Covariant Spectator Model
Kusaka, K.; Piller, G.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia); Williams, A. G.
1996-01-01
Deep-inelastic structure functions are studied within a covariant scalar diquark spectator model of the nucleon. Treating the target as a two-body bound state of a quark and a scalar diquark, the Bethe-Salpeter equation (BSE) for the bound state vertex function is solved in the ladder approximation. The valence quark distribution is discussed in terms of the solutions of the BSE.
A-dependence of weak nuclear structure functions
Haider, H.; Simo, I Ruiz; Athar, M. Sajjad
2013-01-01
Effect of nuclear medium on the weak structure functions $F_2^A(x,Q^2)$ and $F_3^A(x,Q^2)$ have been studied using charged current (anti)neutrino deep inelastic scattering on various nuclear targets. Relativistic nuclear spectral function which incorporate Fermi motion, binding and nucleon correlations are used for the calculations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these str...
EM vs Weak Structure Functions in DIS processes
Athar, M Sajjad; Simo, I Ruiz; Vacas, M J Vicente
2013-01-01
We obatin the ratio $F_i^A/F_i^{D}$(i=2,3, A=Be, C, Fe, Pb; D=Deuteron) in the case of weak and electromagnetic nuclear structure functions. For this, relativistic nuclear spectral function which incorporate the effects of Fermi motion, binding and nucleon correlations is used. We also consider the pion and rho meson cloud contributions and shadowing and antishadowing effects.
Deuteron Spin Structure Functions in the Resonance and DIS Regions
Energy Technology Data Exchange (ETDEWEB)
S. Kulagin; W. Melnitchouk
2007-10-03
We derive relations between spin-dependent nuclear and nucleon g_1 and g_2 structure functions, valid at all Q^2, and in both the resonance and deep inelastic regions. We apply the formalism to the specific case of the deuteron, which is often used as a source of neutron structure information, and compare the size of the nuclear corrections calculated using exact kinematics and using approximations applicable at large Q^2.
International Nuclear Information System (INIS)
We present high statistics results for the structure of the nucleon from a mixed-action calculation using 2+1 flavors of asqtad sea and domain-wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.
Nuclear energy density functional from chiral pion-nucleon dynamics revisited
Energy Technology Data Exchange (ETDEWEB)
Kaiser, N. [Physik Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)], E-mail: nkaiser@ph.tum.de; Weise, W. [Physik Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)
2010-05-15
We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from 1{pi}-exchange, iterated 1{pi}-exchange, and irreducible 2{pi}-exchange with intermediate {delta}-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass M{sup *}({rho}) entering the energy density functional is identical to the one of Fermi-liquid theory when employing the improved density-matrix expansion. The strength F{sub {nabla}}({rho}) of the ({nabla}{sup {yields}}{rho}){sup 2} surface-term as provided by the pion-exchange dynamics is in good agreement with that of phenomenological Skyrme forces in the density region {rho}{sub 0}/2<{rho}<{rho}{sub 0}. The spin-orbit coupling strength F{sub so}({rho}) receives contributions from iterated 1{pi}-exchange (of the 'wrong sign') and from three-nucleon interactions mediated by 2{pi}-exchange with virtual {delta}-excitation (of the 'correct sign'). In the region around {rho}{sub 0}/2{approx_equal}0.08 fm{sup -3} where the spin-orbit interaction in nuclei gains most of its weight these two components tend to cancel, thus leaving all room for the short-range spin-orbit interaction. The strength function F{sub J}({rho}) multiplying the square of the spin-orbit density comes out much larger than in phenomenological Skyrme forces and it has a pronounced density dependence.
Nucleon Spin Fluctuations and Neutrino-Nucleon Energy Transfer in Supernovae
Sigl, G
1997-01-01
The formation of neutrino spectra in a supernova depends crucially on strength and inelasticity of weak interactions in hot nuclear matter. Neutrino interactions with nonrelativistic nucleons are mainly governed by the dynamical structure function for the nucleon spin density which describes its fluctuations. It has recently been shown that these fluctuations give rise to a new mode of energy transfer between neutrinos and nucleons which inside the neutrinosphere is of comparable or greater importance than ordinary recoil. We calculate numerically the spin density structure function in the limit of a dilute, non-degenerate medium from exact two-nucleon wave functions for some representative nuclear interaction potentials. We show that spectrum and magnitude of the energy transfer can deviate significantly from those based on the Born approximation. They are, however, rather insensitive to the particular nuclear potential as long as it reproduces experimental nucleon scattering phase shifts at energies up to a...
Cao, X G; Ma, Y G; Fang, D Q; Zhang, G Q; Guo, W; Chen, J G; Wang, J S; 10.1103/PhysRevC.86.044620
2012-01-01
Proton-neutron, neutron-neutron and proton-proton momentum correlation functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for $^{15}$C and other C isotopes induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum molecular dynamics (IDQMD) model complemented by the CRAB (correlation after burner) computation code. $^{15}$C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron shell nucleus $^{14}$C. In order to study density dependence of correlation function by removing the isospin effect, the initialized $^{15}$C projectiles are sampled from two kinds of density distribution from RMF model, in which the valence neutron of $^{15}$C is populated on both 1$d$5/2 and 2$s$1/2 states, respectively. The results show that the density distributions of valence neutron significantly influence nucleon-nucleon momentum correlation function at large impact parameter and high incident energy. T...
The Behavior of Form Factors of Nucleon Resonances and Quark-Hadron Duality
Davidovsky, V G
2002-01-01
A behavior of the nucleon structure functions in the resonance region is investigated. Expressions for resonance production form factors, dependent on photon virtuality $Q^2$, which have correct threshold behavior and take into account available data on resonance decays, are obtained. Contributions of resonances to nucleon structure functions are calculated. Obtained expressions are used to investigate the quark-hadron duality in the electron-nucleon scattering processes with the structure function $F_2$ as an example.
Nuclear structure functions at low-x in a holographic approach
International Nuclear Information System (INIS)
Nuclear effects in deep inelastic scattering at low x are phenomenologically described changing the typical dynamical and/or kinematical scales characterizing the free nucleon case. In a holographic approach, this rescaling is an analytical property of the computed structure function F2(x, Q2). This function is given by the sum of a conformal term and of a contribution due to quark confinement, depending on IR hard-wall parameter z0 and on the mean square distances, related to a parameter Q', among quarks and gluons in the target. The holographic structure function per nucleon in a nucleus A is evaluated showing that a rescaling of the typical nucleon size, z0 and Q', due to nuclear binding, can be reabsorbed in a Q2-rescaling scheme. The difference between neutron and proton structure functions and the effects of the longitudinal structure functions can also be taken into account. The obtained theoretical results favorably compare with the experimental data. (orig.)
R ratios and moments of nuclear structure functions
Rinat, A. S.; Taragin, M. F.
2000-09-01
We study implications of a model which links nuclear and nucleon structure functions. For this model, computed Callen-Gross functions ?A(x,Q2)=2xFA1(x,Q2)/FA2(x,Q2) are for finite Q2 close to their asymptotic value 1. Using those ?, we compute R ratios for Q2>~5 GeV2. We review approximate methods for the extraction of R from inclusive scattering and EMC data. We also calculate ratios of moments of FAk and find these to describe the data and in particular their Q2 dependence. The above observables, as well as inclusive cross sections, are sensitive tests for the underlying relation between nucleonic and nuclear structure functions. In view of the overall agreement, we speculate that the above relation effectively circumvents a QCD calculation.
Status of nucleon structure calculations with 2+1 flavors of domain wall fermions
Lin, Meifeng
2013-01-01
We report the status of our nucleon structure calculations with 2+1 flavors of domain wall fermions on the RBC-UKQCD $32^3\\times64$ gauge ensembles with the Iwasaki+DSDR action. These ensembles have a fixed lattice scale of 1/a = 1.37 GeV, and two pion masses of about 170 and 250 MeV. Preliminary results for the isovector electromagnectic form factors and their corresponding root-mean-squared (r.m.s.) radii will be presented.
Monte Carlo Generators for Studies of the 3D Structure of the Nucleon
Energy Technology Data Exchange (ETDEWEB)
Avagyan, Harut A. [JLAB
2015-01-01
Extraction of transverse momentum and space distributions of partons from measurements of spin and azimuthal asymmetries requires development of a self consistent analysis framework, accounting for evolution effects, and allowing control of systematic uncertainties due to variations of input parameters and models. Development of realistic Monte-Carlo generators, accounting for TMD evolution effects, spin-orbit and quark-gluon correlations will be crucial for future studies of quark-gluon dynamics in general and 3D structure of the nucleon in particular.
Gebremariam, B.; Bogner, S. K.; Duguet, T
2010-01-01
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in arXiv:0910.4979 by Gebremariam {\\it et al.} to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (...
Nuclear structure functions and off-shell corrections
Benhar, O; Fantoni, S.; Lykasov, G. I.
2000-01-01
The $n$-th moments of the nuclear structure function $F_2^A(x,Q^2)$ are analyzed using the off-shell kinematics appropriate to describe deep inelastic electron-nucleus scattering within the impulse approximation. It is shown that off-shell effects are sensitive to the form of both the nuclear spectral function and the nucleon structure function $F_2^N(x,Q^2)$, and can be as large as $\\sim 10%$ at Q$^2~\\sim~2$~(GeV/c)$^2$.
On the unabridged 7D-folding structure of the optical model potential for nucleon-nucleus scattering
International Nuclear Information System (INIS)
Microscopic optical model potentials for nucleon-nucleus collisions, based on density-dependent effective interactions, involve multi-dimensional integrals to account for the Fermi motion of the bound nucleons of the target. If a spherical matter distribution is assumed, each matrix element of the optical potential, U(k',k;E), requires the evaluation of seven-dimensional integrals. In this contribution we report results when a full account of such integrals is in place, retaining the genuine off-shell structure of the nucleon-nucleon effective interaction given by solutions for the g matrix in the Brueckner-Bethe-Goldstone framework. These calculations are very intensive in CPU computing time, becoming feasible only with the use of multiprocessor platforms. The resulting non-local potentials, based on g matrices from the Paris nucleon-nucleon (NN) potential, are applied to proton elastic scattering from 16O and 90Zr at beam energies between 30 and 65 MeV. We have compared these results with those obtained with alternative approximations observing moderate differences among their scattering observables. In this presentation we shall also address issues regarding the coordinate-space structure implied by the unabridged optical potential, aiming to disclose its equivalence with traditional coordinate-space approaches based on local effective interactions within the local density approximation. (author)
Flavor Dependence of Sea Quark Structure Functions
Kim, C S; S. M. Kim; Olsson, M. G.
1993-01-01
Quark masses are shown to play an important role in the nucleon sea. Our analysis using massive QCD splitting functions demonstrates the existence of two Feynman-$x$ sea regimes. For small $x$ the strange sea is larger while at large $x$ the non-strange light sea is dominant. This crossover effect has been observed in a phenomenological analysis by the CTEQ Collaboration. We also investigate the charm component in the nucleon.
International Nuclear Information System (INIS)
MENU'97 covered many stunning successes of chiral symmetry in intermediate energy reactions, especially of processes that involve pions. These successes include coupling constants, scattering lengths, threshold meson production, electric and magnetic polarizabilities of pions and nucleons, peripheral NN scattering, ?, ? and K decay rates and spectra. The ?N data bank at low energy, which in the past was notorious for the inconsistencies of different data sets, is shown to become consistent by deleting a modest number of previously accepted data sub-sets. There is a consensus on a better value for the pion-nucleon coupling constant, which has been a bone of contention earlier, namely, f?NN2/4?=(75.40.4)x10-3 in satisfactory agreement with the Goldberger-Treiman relation. The mass-spin/parity distribution of the experimentally established ?N resonances does not support the prediction of the harmonic oscillator type quark model. Some massive ?++ resonances decay by ? emission to the ?+p? final state. In contrast to this the decay of massive N* states to ?-p? in small, less than 5% of ?++??+p?. A new s-wave ? decay has been identified, D33(1700)?P33(1232)+?. There is interesting new threshold data from CELSIUS on np?d? as well as on pp?pp? and np?np?
Nucleon spin structure functions from the spin muon collaboration
International Nuclear Information System (INIS)
The spin muon collaboration (SMC) has studied polarized deep inelastic scattering of muons on protons and deuterons using a high energy muon beam at CERN. We present here a summary of the results obtained from data taken in the last two years. copyright 1995 American Institute of Physics
DEFF Research Database (Denmark)
Sinden, Richard R.; E. Pearson, Christopher
1998-01-01
This chapter discusses the structure and function of DNA. DNA occupies a critical role in cells, because it is the source of all intrinsic genetic information. Chemically, DNA is a very stable molecule, a characteristic important for a macromolecule that may have to persist in an intact form for a long period of time before its information is accessed by the cell. Although DNA plays a critical role as an informational storage molecule, it is by no means as unexciting as a computer tape or disk drive. The structure of the DNA described by Watson and Crick in 1953 is a right handed helix of two individual antiparallel DNA strands. Hydrogen bonds provide specificity that allows pairing between the complementary bases (A.T and G.C) in opposite strands. Base stacking occurs near the center of the DNA helix and provides a great deal of stability to the helix (in addition to hydrogen bonding). The sugar and phosphate groups form a backbone on the outside of the helix. There are about 10 base pairs (bp) per turn ofthe double helix.
Travers, Andrew; Muskhelishvili, Georgi
2015-06-01
The proposal of a double-helical structure for DNA over 60 years ago provided an eminently satisfying explanation for the heritability of genetic information. But why is DNA, and not RNA, now the dominant biological information store? We argue that, in addition to its coding function, the ability of DNA, unlike RNA, to adopt a B-DNA structure confers advantages both for information accessibility and for packaging. The information encoded by DNA is both digital - the precise base specifying, for example, amino acid sequences - and analogue. The latter determines the sequence-dependent physicochemical properties of DNA, for example, its stiffness and susceptibility to strand separation. Most importantly, DNA chirality enables the formation of supercoiling under torsional stress. We review recent evidence suggesting that DNA supercoiling, particularly that generated by DNA translocases, is a major driver of gene regulation and patterns of chromosomal gene organization, and in its guise as a promoter of DNA packaging enables DNA to act as an energy store to facilitate the passage of translocating enzymes such as RNA polymerase. PMID:25903461
Spin structure function measurements with polarized protons and electrons at HERA
International Nuclear Information System (INIS)
Useful insights into the spin structure functions of the nucleon can be achieved by measurements of spin-dependent asymmetries in inclusive scattering of high energy polarized electrons by high energy polarized protons at HERA. Such an experiment would be a natural extension of the polarized lepton-nucleon scattering experiments presently carried out at CERN and SLAC. We present here estimates of possible data in the extended kinematic range of HERA and associated statistical errors. (orig.)
Nucleon quark distributions in a covariant quark-diquark model
Cloet, I. C.; Bentz, W.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
2005-01-01
Spin-dependent and spin-independent quark light-cone momentum distributions and structure functions are calculated for the nucleon. We utilize a modified Nambu-Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. We find excellent agreement ...
Strange / anti-strange asymmetry in the nucleon sea
Christiansen, H. R.; Magnin, J.(Centro Brasileiro de Pesquisas Fsicas (CBPF), Rio de Janeiro, Brazil)
1998-01-01
We analyze the non-perturbative structure of the strange sea of the nucleon within a meson cloud picture. In a low $Q^2$ approach in which the nucleon is viewed as a three valon bound state, we evaluate the probability distribution of an in-nucleon Kaon-Hyperon pair in terms of splitting functions and recombination. The resulting kaon and hyperon probability densities are convoluted with suitable strange distributions inside the meson and baryon in order to obtain non-pertur...
Bound Nucleon Form Factors, Quark-Hadron Duality, and Nuclear EMC Effect
Tsushima, K.; Lu, D. H.; Melnitchouk, W.(Jefferson Lab, Newport News, VA 23606, USA); Saito, K.(Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan); Thomas, A. W.
2003-01-01
We discuss the electromagnetic form factors, axial form factors, and structure functions of a bound nucleon in the quark-meson coupling (QMC) model. Free space nucleon form factors are calculated using the improved cloudy bag model (ICBM). After describing finite nuclei and nuclear matter in the quark-based QMC model, we compute the in-medium modification of the bound nucleon form factors in the same framework. Finally, limits on the medium modification of the bound nucleon ...
Litvinova, Elena
2015-01-01
The relativistic particle-vibration coupling (RPVC) model is extended by the inclusion of spin- and isospin-flip excitation modes into the phonon space, introducing a new mechanism of dynamical interaction between nucleons with different isospin in the nuclear medium. Protons and neutrons exchange by collective modes which are formed by isovector $\\pi$ and $\\rho$-mesons, in turn, softened considerably because of coupling to nucleons of the medium. These modes are investigated within the proton-neutron relativistic random phase approximation (pn-RRPA) and relativistic proton-neutron time blocking approximation (pn-RTBA). The appearance of isospin-flip states with sizable transition probabilities at low energies points out that they are likely to couple to the single-particle degrees of freedom and, in addition to isoscalar low-lying phonons, to modify their spectroscopic characteristics. Such a coupling is quantified for the shell structure of $^{100,132}$Sn and found significant for the location of the domina...
Neutron/Proton Structure Function Ratio at Large x
Melnitchouk, W; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
1996-01-01
We re-examine the large-x neutron/proton structure function ratio extracted from the latest deuteron data, taking into account the most recent developments in the treatment of Fermi motion, binding and nucleon off-shell effects in the deuteron. Our findings suggest that as x->1 the ratio of the neutron to proton structure functions (F_2^n/F_2^p) is consistent with the perturbative QCD expectation of 3/7, but larger than the value of 1/4 obtained in earlier analyses.
The effect of confinement size on nuclear structure functions
International Nuclear Information System (INIS)
The differences in the structure function of a heavy nucleus, such as iron, compared to a light nucleus, are considered. In the context of QCD, a suggestion that these differences arise as a result of differences in the scale of confinement of the nuclear constituents is investigated. This results in a simple relationship between heavy and light nucleus structure functions which is in reasonable agreement with experiment if the confinement size in iron is around 10-20% greater than in a free nucleon. (author)
Nucleon-nucleon scattering lengths in QCD sum rules
International Nuclear Information System (INIS)
Nucleon-nucleon scattering lengths are calculated using QCD sum rules. The calculation is based on the observation that the coefficient of the second-order pole term of the nucleon correlation function is proportional to the nucleon-nucleon scattering length at the threshold. By applying the Borel sum rules, we express the scattering length in terms of the expectation values of the quark-gluon field operators with respect to the one-nucleon state. The scattering lengths calculated are in qualitative agreement with the experiment. It is also shown that in the linear density approximation the nucleon mass shift in nuclear matter is related to the nucleon-nucleon scattering length. It is concluded that the recent calculations of the effective nucleon mass in nuclear matter using QCD sum rules with linear density approximation for the condensates should be interpreted in this way. (author)
International Nuclear Information System (INIS)
Prospects of decribing polarization effects within the framework of quark-parton models (QPM) using a density matrix in order to describe the parton spin states in hadrons are discussed. Such an approach allows one to get rid of contradictions occuring when describing the QPM of reactions of hadrons polarized in perpendicular to the scattering plane in case of applying spin distribution functions. Different model predictions for the observed one- and two-spin correlations in elastic nucleon-nucleon scattering are analyzed. 12 refs., 2 tabs
Ab initio Nuclear structure Theory with chiral two- plus three-nucleon interactions
International Nuclear Information System (INIS)
Low-energy nuclear theory has entered an era of ab initio nuclear structure and reaction calculations based on input from QCD. One of the most promising paths from QCD to nuclear observables employs Hamiltonians constructed within chiral effective field theory as consistent starting point for precise ab initio nuclear structure and reaction studies. However, the full inclusion of chiral two- plus three-nucleon (NN+3N) interactions in exact and approximate many-body calculations still poses a formidable challenge. We discuss recent developments towards this goal, ranging from consistent Similarity Renormalization Group evolutions of NN+3N Hamiltonians to large-scale ab initio calculations for ground states and spectra in the Importance-Truncated No-Core Shell Model with full 3N interactions. We highlight recent achievements and discuss open issues and future perspectives for nuclear structure theory with QCD-based interactions. Moreover, we discuss successful steps towards merging ab initio structure and reaction theory and show applications to low-energy reactions in the p-shell relevant for astrophysics.
International Nuclear Information System (INIS)
The longitudinal charge function in the quasi-elastic peak region is calculated, including effects of two-nucleon collisions. The coupled RPA equation for 2p2h states is solved, using a Thomas-Fermi type theory. To calculate the response function for RPA orders, the Gogny force (a density dependent finite range force) is used, both for the mean field and the residual ph interaction. To include the 2p2h states it was necessary to study the dynamic nuclear mass operator M in the 2p1h (2h1p) approximation. The Gogny force was used as interaction at the vertex of the mass operator. The density dependence of the Gogny force gives a pronounced surface peak in the imaginary part of M. The inclusion of the mass operator in the ph motion gives 2p2h states. Their influence considerably reduces the RPA order response and generally produces a better agreement between theory and experiment, although inexplicable exceptions remain. The investigation suggests that it is not necessary to modify the nuclear form factor
The functions of structural priming
Ferreira, Victor S.; Bock, Kathryn
2006-01-01
Structural priming refers to speakers tendency to produce sentences with previously heard or produced syntactic structures. We review arguments and evidence for three common accounts of the functions of structural priming. One is that structural priming enhances fluency. Only some (reaction time and fluency measure) evidence supports this view. A second account argues that structural priming stems from implicit learning of how features of meaning are linked to syntactic configurations. We de...
Nuclear medium modification of the F2 structure function
Athar, M Sajjad; Vacas, M J Vicente
2009-01-01
We study the nuclear effects in the electromagnetic structure function $F_{2}(x, Q^2)$ in nuclei in the deep inelastic lepton nucleus scattering process by taking into account Fermi motion, binding, pion and rho meson cloud contributions. Calculations have been done in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations for nuclear matter. The ratios $R_{F2}^A(x,Q^2)=\\frac{2F_2^A(x,Q^2)}{AF_{2}^{Deut}(x,Q^2)}$ are obtained and compared with the recent JLAB results for light nuclei that show a non trivial A dependence.
Tensor-polarized structure functions: Tensor structure of deuteron in 2020's
Kumano, S
2014-01-01
We explain spin structure for a spin-one hadron, in which there are new structure functions, in addition to the ones ($F_1$, $F_2$, $g_1$, $g_2$) which exist for the spin-1/2 nucleon, associated with its tensor structure. The new structure functions are $b_1$, $b_2$, $b_3$, and $b_4$ in deep inelastic scattering of a charged-lepton from a spin-one hadron such as the deuteron. Among them, twist-two functions are related by the Callan-Gross type relation $b_2 = 2 x b_1$ in the Bjorken scaling limit. First, these new structure functions are introduced, and useful formulae are derived for projection operators of $b_{1-4}$ from a hadron tensor $W_{\\mu\
Target mass correction on the {sup 3}He polarized structure function
Energy Technology Data Exchange (ETDEWEB)
Mirjalili, A. [Yazd University, Physics Department, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of); Yazdanpanah, M.M. [Kerman Shahid Bahonar University, Physics Department, Kerman (Iran, Islamic Republic of)
2012-05-15
Target mass correction (TMC) is employed to amend the polarized helium structure functions, {sup 3}He. The structure function can be obtained via the convolution of the light cone momentum distribution with the polarized structure of the proton and neutron. The calculation of the polarized structure function of the nucleon is based on the constituent quark model. The analytical result for {sup 3}He polarized structure function at low values of Q{sup 2} is not in good agreement with the available experimental data. The reliability of calculations is increased using TMC effect. New comparison confirms a better agreement with the experimental data. (orig.)
Radioprotectors: structure and function
International Nuclear Information System (INIS)
Research of means of pharmacological protection of the organism against ionizing radiation effect is presented. A modern state of the problem is shown. Non-routine classification of the radioprotectors is given. A connection between chemical structure of the preparations and their antiactinic efficiency is analyzed on the example of many radioprotectors. Some aspects of mechanism of action of various radioprotective substances are studied. The certain chapter is devoted to the problem of preparation of antiactinic compositions. 336 refs.; 29 figs.; 43 tabs
Spin-orbit coupling in nuclei and realistic nucleon-nucleon potentials
Kaiser, N
2004-01-01
We analyze the spin-orbit coupling term in the nuclear energy density functional in terms of a zero-range NN-contact interaction and finite-range contributions from two-pion exchange. We show that the strength of the spin-orbit contact interaction as extracted from high-precision nucleon-nucleon potentials is in perfect agreement with that of phenomenological Skyrme forces employed in non-relativistic nuclear structure calculations. Additional long-range contributions from c...
Directory of Open Access Journals (Sweden)
F Zolfagharpour
2012-03-01
Full Text Available In this paper, we calculate nuclear structure function and EMC effect of 40Ca and 56Fe nuclei. To achive the goals, we consider Fermi motion and binding energy contrbiution in the harmonic oscillator model. In this model, harmonic oscillator parameter ?? related to shells root mean square radius and for free nucleon structure functions, is obtained from GRVs free nucleon structure functions. Then, we calculate differential cross section of lepton scattering from those nuclei at the E=4.8 GeV and E=4.032 GeV. The obtained results show good agreement with available experimental data.
Fine structure in ? decay of even-even nuclei using a finite-range nucleon-nucleon interaction
Adel, A.; Alharbi, T.
2015-07-01
A systematic study on ? -decay fine structure is presented for even-even nuclei in the range 78 ?Z ?102 . The penetration probability is obtained from the WKB approximation in combination with the Bohr-Sommerfeld quantization condition. The potential barrier is numerically constructed in the well-established double-folding model for both Coulomb and nuclear potentials. A realistic M3Y interaction, based on the G -matrix elements of the Paris N N potential, has been used in the folding calculation. The local approximation for the nondiagonal one-body density matrix in the calculation of the exchange potential was included by using the harmonic oscillator representation of the nondiagonal density matrix of the ? particle. The computed partial half-lives and branching ratios are compared with the recent experimental data and they are in good agreement.
Influence of the target nucleus shell structure on the pre-equilibrium nucleon emission
International Nuclear Information System (INIS)
A modified version of the exciton model is used for the analysis of nucleon emission spectra in neutron induced reactions at 14 MeV. Details of the model and several important conclusions are discussed. (author)
In-medium nucleon-nucleon potentials in configuration space
Beyer, M
2001-01-01
Based on the thermodynamic Green function approach two-nucleon correlations in nuclear matter at finite temperatures are revisited. To this end, we derive phase equivalent effective $r$-space potentials that include the effect of the Pauli blocking at a given temperature and density. These potentials enter into a Schr\\"odinger equation that is the $r$-space representation of the Galitskii-Feynman equation for two nucleons. We explore the analytical structure of the equation in the complex $k$-plane by means of Jost functions. We find that despite the Mott effect the correlation with deuteron quantum numbers are manifested as antibound states, i.e., as zeros of the Jost function on the negative imaginary axis of the complex momentum space. The analysis presented here is also suited for Coulombic systems.
Bound Nucleon Form Factors, Quark-Hadron Duality, and the Nuclear EMC Effect
International Nuclear Information System (INIS)
We discuss the electromagnetic form factors, axial form factors, and structure functions of a nucleon bound in the quark-meson coupling (QMC) model. Free space nucleon form factors are calculated using the improved cloudy bag model (ICBM). After describing finite nuclei and nuclear matter in the quark-based (EMC) model, the in-medium modification of the bound nucleon form factors is calculated in the same model. Finally, the bound nucleon structure function, F2, is extracted using the calculated in-medium electromagnetic form factors and Bloom-Gilman (quark-hadron) duality
Bound Nucleon Form Factors, Quark-Hadron Duality, and Nuclear EMC Effect
Tsushima, K; Melnitchouk, W; Sait, K; Thomas, A W
2003-01-01
We discuss the electromagnetic form factors, axial form factors, and structure functions of a bound nucleon in the quark-meson coupling (QMC) model. Free space nucleon form factors are calculated using the improved cloudy bag model (ICBM). After describing finite nuclei and nuclear matter in the quark-based QMC model, we compute the in-medium modification of the bound nucleon form factors in the same framework. Finally, limits on the medium modification of the bound nucleon $F_2$ structure function are obtained using the calculated in-medium electromagnetic form factors and local quark-hadron duality.
SYSTEMS THEORY AND STRUCTURAL FUNCTIONALISM
Directory of Open Access Journals (Sweden)
Shrikant Yelegaonkar
2014-12-01
Full Text Available Albeit structural functionalism thinks that its roots much sooner than frameworks does hypothesis, as analysts utilization it today, it is focused around frameworks hypothesis. Structural functionalism follows its beginnings back to the aged Greeks and the compositions of Aristotle (Susser, 1992. Frameworks hypothesis rose much later. Despite the fact that the discourse of frameworks started with scientists in the nineteenth century, frameworks hypothesis was not completely verbalized until the 1920s. Ludwig von Bertalanffy (1956, 1962, who created general frameworks hypothesis, was a primary in making it as a field of study. In spite of the fact that frameworks hypothesis began later than functionalism, when scientists study works inside their structures, they do it inside the extent of frameworks. The investigation of political frameworks contributed more than its fair share with the selection of a structural- utilitarian methodology
Functional Insights from Structural Genomics
Energy Technology Data Exchange (ETDEWEB)
Forouhar,F.; Kuzin, A.; Seetharaman, J.; Lee, I.; Zhou, W.; Abashidze, M.; Chen, Y.; Montelione, G.; Tong, L.; et al
2007-01-01
Structural genomics efforts have produced structural information, either directly or by modeling, for thousands of proteins over the past few years. While many of these proteins have known functions, a large percentage of them have not been characterized at the functional level. The structural information has provided valuable functional insights on some of these proteins, through careful structural analyses, serendipity, and structure-guided functional screening. Some of the success stories based on structures solved at the Northeast Structural Genomics Consortium (NESG) are reported here. These include a novel methyl salicylate esterase with important role in plant innate immunity, a novel RNA methyltransferase (H. influenzae yggJ (HI0303)), a novel spermidine/spermine N-acetyltransferase (B. subtilis PaiA), a novel methyltransferase or AdoMet binding protein (A. fulgidus AF{_}0241), an ATP:cob(I)alamin adenosyltransferase (B. subtilis YvqK), a novel carboxysome pore (E. coli EutN), a proline racemase homolog with a disrupted active site (B. melitensis BME11586), an FMN-dependent enzyme (S. pneumoniae SP{_}1951), and a 12-stranded {beta}-barrel with a novel fold (V. parahaemolyticus VPA1032).
The Role of Higher Order Corrections in Determining Polarized Parton Densities in the Nucleon
Khorramian, A. N.; Mirjalili, A.; Tehrani, S. Atashbar
2005-04-01
We study moments of polarized valon distributions in leading and next-to-leading order approximation. By computing the internal structure of polarized valons from inverse Mellin transformation and using their distributions in the nucleon, we will be able to calculate the polarized parton distributions and structure function in the nucleon.
Chiral three-nucleon interactions in ab-initio nuclear structure and reactions
International Nuclear Information System (INIS)
The prediction of nuclear structure and reaction observables based on nuclear Hamiltonians including two- and three-nucleon (NN+3N) interactions derived from chiral effective field theory constitutes a challenging task for ab-initio nuclear theory. In particular, the consistent inclusion of 3N interactions requires formal extensions of the many-body methods and, at the same time, causes a significant increase of the computational cost. This work presents the necessary steps for the inclusion and the subsequent application of 3N interactions in different ab-initio nuclear structure and reaction approaches. The first part is dedicated to the preparation of the chiral nuclear forces before they enter the many-body methods. It addresses the similarity renormalization group (SRG) as a tool to soften the initial chiral interactions and its generalization to consistently include 3N interactions. Moreover, the technically important 3N matrix-element management in a convenient basis for the subsequent many-body methods including an efficient storage scheme is discussed. In addition, a possibility to derive approximative schemes for 3N interactions using normal ordering is presented. In the second part the SRG-evolved chiral NN+3N Hamiltonians are applied in nuclear structure calculations using the importance truncated no-core shell model (IT-NCSM) as well as coupled-cluster theory. The impact of SRG-induced and chiral 3N interactions on ground-state energies and low-energy spectra of different p-shell nuclei is studied, including a sensitivity analysis concerning uncertainties of the chiral interactions in the 12C and 10B spectra. Furthermore, the first ab-initio study of even oxygen isotopes with explicit 3N interactions is presented, and by means of the normal-ordered two-body approximation the ground-state energy systematics of selected closed-shell nuclei throughout the calcium, nickel, and tin isotopic chains are obtained in qualitative agreement with experiment. The third part of this work focuses on 3N interactions in ab-initio nuclear scattering approaches. This includes a detailed discussion of the inclusion of 3N interactions in the no-core shell model combined with the resonating-group method (NCSM/RGM) with emphasis on the ability to treat targets beyond the lightest nuclei. The extended formalism is then applied to nucleon-4He scattering, where the 3N interaction overall improves scattering phase shifts, differential cross sections and analyzing powers. Finally, the no-core shell model with continuum approach, which constitutes a unified ab-initio approach to bound and scattering states resulting from the combination of the NCSM and the NCSM/RGM, is generalized to 3N interactions and applied to the neutron-8Be system to study the impact of the continuum on the 9Be energy levels. The results demonstrate the importance of the consistent treatment of continuum states.
Chiral three-nucleon interactions in ab-initio nuclear structure and reactions
Energy Technology Data Exchange (ETDEWEB)
Langhammer, Joachim
2014-04-23
The prediction of nuclear structure and reaction observables based on nuclear Hamiltonians including two- and three-nucleon (NN+3N) interactions derived from chiral effective field theory constitutes a challenging task for ab-initio nuclear theory. In particular, the consistent inclusion of 3N interactions requires formal extensions of the many-body methods and, at the same time, causes a significant increase of the computational cost. This work presents the necessary steps for the inclusion and the subsequent application of 3N interactions in different ab-initio nuclear structure and reaction approaches. The first part is dedicated to the preparation of the chiral nuclear forces before they enter the many-body methods. It addresses the similarity renormalization group (SRG) as a tool to soften the initial chiral interactions and its generalization to consistently include 3N interactions. Moreover, the technically important 3N matrix-element management in a convenient basis for the subsequent many-body methods including an efficient storage scheme is discussed. In addition, a possibility to derive approximative schemes for 3N interactions using normal ordering is presented. In the second part the SRG-evolved chiral NN+3N Hamiltonians are applied in nuclear structure calculations using the importance truncated no-core shell model (IT-NCSM) as well as coupled-cluster theory. The impact of SRG-induced and chiral 3N interactions on ground-state energies and low-energy spectra of different p-shell nuclei is studied, including a sensitivity analysis concerning uncertainties of the chiral interactions in the {sup 12}C and {sup 10}B spectra. Furthermore, the first ab-initio study of even oxygen isotopes with explicit 3N interactions is presented, and by means of the normal-ordered two-body approximation the ground-state energy systematics of selected closed-shell nuclei throughout the calcium, nickel, and tin isotopic chains are obtained in qualitative agreement with experiment. The third part of this work focuses on 3N interactions in ab-initio nuclear scattering approaches. This includes a detailed discussion of the inclusion of 3N interactions in the no-core shell model combined with the resonating-group method (NCSM/RGM) with emphasis on the ability to treat targets beyond the lightest nuclei. The extended formalism is then applied to nucleon-{sup 4}He scattering, where the 3N interaction overall improves scattering phase shifts, differential cross sections and analyzing powers. Finally, the no-core shell model with continuum approach, which constitutes a unified ab-initio approach to bound and scattering states resulting from the combination of the NCSM and the NCSM/RGM, is generalized to 3N interactions and applied to the neutron-{sup 8}Be system to study the impact of the continuum on the {sup 9}Be energy levels. The results demonstrate the importance of the consistent treatment of continuum states.
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-10-01
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out by New Mexico State University from April 1, 1994, through March 31, 1996 under a grant from the US Department of Energy. During this period we began phasing out our programs of study of pion-nucleus and pion-nucleon interaction and of nucleon-nucleus charge-exchange reactions, which have been our major focus of the past two or three years. At the same time we continued moving in a new direction of research on studies of the internal structure of nucleons and nuclei in terms of quarks and gluons. The pion and nucleon work has been aimed at improving our understanding of the nature of pion and proton interactions in the nuclear medium and of various aspects of nuclear structure. The studies of the quark-gluon structure of nucleons are aimed at clarifying such problems as the nature of the quark sea and the relation of the nucleon spin to the spins of the quarks within the nucleon, questions which are of a very fundamental nature.
International Nuclear Information System (INIS)
This report summarizes the work on experimental research in intermediate energy nuclear physics carried out by New Mexico State University from April 1, 1994, through March 31, 1996 under a grant from the US Department of Energy. During this period we began phasing out our programs of study of pion-nucleus and pion-nucleon interaction and of nucleon-nucleus charge-exchange reactions, which have been our major focus of the past two or three years. At the same time we continued moving in a new direction of research on studies of the internal structure of nucleons and nuclei in terms of quarks and gluons. The pion and nucleon work has been aimed at improving our understanding of the nature of pion and proton interactions in the nuclear medium and of various aspects of nuclear structure. The studies of the quark-gluon structure of nucleons are aimed at clarifying such problems as the nature of the quark sea and the relation of the nucleon spin to the spins of the quarks within the nucleon, questions which are of a very fundamental nature
Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass
Abdel-Rehim, A; Constantinou, M; Dimopoulos, P; Frezzotti, R; Hadjiyiannakou, K; Jansen, K; Kallidonis, Ch; Kostrzewa, B; Koutsou, G; Mangin-Brinet, M; Oehm, M; Rossi, G C; Urbach, C; Wenger, U
2015-01-01
We present results on the nucleon scalar, axial and tensor charges as well as on the momentum fraction, and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key observables is carried out using lattice QCD simulations at a physical value of the pion mass. The evaluation is based on gauge configurations generated with two degenerate sea quarks of twisted mass fermions with a clover term. We investigate excited states contributions with the nucleon quantum numbers by analyzing three sink-source time separations. We find that, for the scalar charge, excited states contribute significantly and to a less degree to the nucleon momentum fraction and helicity moment. Our analysis yields a value for the nucleon axial charge agrees with the experimental value and we predict a value of 1.027(62) in the $\\overline{\\text{MS}}$ scheme at 2 GeV for the isovector nucleon tensor charge directly at the physical point. The pion momentum fraction is found to be $\\langl...
Longitudinal heavy quark structure function
Energy Technology Data Exchange (ETDEWEB)
Khorramian, Ali N. [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of); School of Particles and Accelerators, IPM - Institute for Studies in Theoretical Physics and Mathematics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: khorramiana@theory.ipm.ac.ir; Atashbar Tehrani, S. [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of); School of Particles and Accelerators, IPM - Institute for Studies in Theoretical Physics and Mathematics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: atashbar@ipm.ir; Mirjalili, A. [Physics Department, Yazd University, Yazd (Iran, Islamic Republic of); School of Particles and Accelerators, IPM - Institute for Studies in Theoretical Physics and Mathematics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: mirjalili@ipm.ir
2009-01-15
In this paper we study the heavy-quark contribution to the proton non-singlet structure functions F{sub L}{sup NS}(x,Q{sup 2}). In this way we use very recently results for massive operator matrix elements, which contribute to the heavy flavor Wilson coefficients in unpolarized deeply inelastic scattering in the region Q{sup 2}>>m{sup 2}. The method of QCD analysis of non-singlet structure function, based on their Jacobi polynomials reconstruction from perturbative QCD predictions for the Mellin moments, is also described.
Energy Technology Data Exchange (ETDEWEB)
Colleen Ellis
2010-07-01
The G0 backward angle experiment, completed in Hall C of the Thomas Jefferson National Accelerator Facility (TJNAF), measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2 = 0.22 and 0.63 (GeV/c)2. The asymmetries are sensitive to strange quark contributions to currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of lte 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. This was also the first measurement of the anapole moment effects in the axial-vector current at these four-momentum transfers.
Electromagnetic Structure and Reactions of Few-Nucleon Systems in ?EFT
Directory of Open Access Journals (Sweden)
Schiavilla R.
2010-04-01
Full Text Available We summarize our recent work dealing with the construction of the nucleon-nucleon potential and associated electromagnetic currents up to one loop in chiral e?ective ?eld theory (?EFT. The magnetic dipole operators derived from these currents are then used in hybrid calculations of static properties and low-energy radiative capture processes in few-body nuclei. A preliminary set of results are presented for the magnetic moments of the deuteron and trinucleons and thermal neutron captures on p, d, and 3He.
Lepton-nucleon scattering at high energies
International Nuclear Information System (INIS)
Recent theoretical developments in the field of inelastic lepton-nucleon scattering are reviewed with emphasis on physics at HERA. Structure functions at small Bjorken-x are discussed in detail. Further topics are photoproduction of jets, the gluon densities in proton and photon, charm physics, electroweak processes and the search for new particles and interactions. (orig.)
The dipole model structure functions
International Nuclear Information System (INIS)
We present an approach to the evolution of the valence structure functions based on the Colour Dipole Cascade Model for deep inelastic lepto-production. We show that this approach leads to an evolution equation similar to the DGLAP equation. In our approach the dependence on Q2 is however much weaker and the evolution levels out at high Q2. (orig.)
Instantons and Polarized Structure Functions
Kochelev, N. I.
1997-01-01
The contribution of the quark-quark and quark-gluon interaction induced by instantons to the valence quark and proton spin-dependent structure functions $g_1(x,Q^2)$ is estimated within the instanton liquid model for QCD vacuum. It is shown, that this interaction leads to a rather large violation of the Ellis-Jaffe sum rule.
Chiral Odd Structure Functions within a Chiral Soliton
Gamberg, L P; Weigel, H
1998-01-01
We calculate the chiral odd structure functions $h_T(x,Q^2)$ and $h_L(x,Q^2)$ within the Nambu-Jona-Lasinio chiral soliton model for the nucleon. The $Q^2$ evolution of the twist--2 contributions is performed according to the standard GLAP formalism while the twist-three piece, $\\bar{h}_L(x)$, is evolved according to the large $N_C$ scheme. We carry out a comparison between the chiral odd structure functions of the proton and the neutron. At the low model scale ($Q_0^2$) we find that the leading twist effective quark distributions, $f_1^{(u)}(x,Q_0^2)$, $g_1^{(u)}(x,Q_0^2)$ and $h_T^{(u)}(x,Q_0^2)$ satisfy Soffer's inequality.
Deuteron A(Q2) structure function and the neutron electric form factor
International Nuclear Information System (INIS)
We present new measurements of the deuteron A(Q2) structure function in the momentum transfer region between 1 and 18 fm-2. The accuracy of the data ranges from 2% to 6%. We investigate the sensitivity of A(Q2) to the nucleon-nucleon interaction and to the neutron electric form factor GEn. Our analysis shows that below 20 fm-2 GEn can be inferred from these data with a significantly improved accuracy. The model dependence of this analysis is discussed
Chiral perturbation theory with nucleons
International Nuclear Information System (INIS)
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, ?N scattering and the ?-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon
x- and xi-scaling of the Nuclear Structure Function at Large x
International Nuclear Information System (INIS)
Inclusive electron scattering data are presented for 2H and Fe targets at an incident electron energy of 4.045 GeV for a range of momentum transfers from Q2 = 1 to 7 (GeV/c)2. Data were taken at Jefferson Laboratory for low values of energy loss, corresponding to values of Bjorken x greater than or near 1. The structure functions do not show scaling in x in this range, where inelastic scattering is not expected to dominate the cross section. The data do show scaling, however, in the Nachtmann variable ?. This scaling may be the result of Bloom Gilman duality in the nucleon structure function combined with the Fermi motion of the nucleons in the nucleus. The resulting extension of scaling to larger values of ? opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q2 than previously believed
Nuclear structure function FA2: Moments Mn(FA2) and kinematics beyond x=1
Kaptari, L. P.; Umnikov, A. Yu; Kmpfer, B.
1993-05-01
An analysis of the behavior of nuclear structure functions FA2 at large x and their moments MAn at large n has been performed within two theoretical approaches: (i) the QCD-motivated Q2-rescaling model and (ii) the operator product expansion method within an effective meson-nucleon theory which is prompted by nuclear physics. Our theoretical estimates of the nuclear structure function at x>=1 are in good agreement with existing data. The moments, derived from experimental data, are found to depend essentially on the behavior of the respective structure functions beyond x=1. A relation between the Q2-rescaling parameter ?A and nuclear averages, i.e., mean kinetic energy and chemical potential of nucleons, as well as a dependence of ?A on n are established.
Role of Vector Mesons in High-Q^2 Lepton-Nucleon Scattering
Melnitchouk, W; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
1993-01-01
The possible role played by vector mesons in inclusive deep inelastic lepton-nucleon scattering is investigated. In the context of the convolution model, we calculate self-consistently the scaling contribution to the nucleon structure function using the formalism of time-ordered perturbation theory in the infinite momentum frame. Our results indicate potentially significant effects only when the vector meson---nucleon form factor is very hard. Agreement with the experimental...
First moment of the flavour octet nucleon parton distribution function using lattice QCD
International Nuclear Information System (INIS)
We perform a lattice computation of the flavour octet contribution to the average quark momentum in a nucleon, left angle x right angle (8)?2=4 GeV2. In particular, we fully take the disconnected contributions into account in our analysis for which we use a generalization of the technique developed by S. Dinter et. al. (2012). We investigate systematic effects with a particular emphasis on the excited states contamination. We find that in the renormalization free ratio (left angle x right angle (3))/(left angle x right angle (8)) (with left angle x right angle (3) the non-singlet moment) the excited state contributions cancel to a large extend making this ratio a promising candidate for a comparison to phenomenological analyses. Our final result for this ratio is in agreement with the phenomenological value and we find, including systematic errors, (left angle x right angle (3))/(left angle x right angle (8))=0.39(1)(4).
Nuclear energy density functional from chiral pion-nucleon dynamics: Isovector terms
Energy Technology Data Exchange (ETDEWEB)
Kaiser, N. [Technische Universitaet Muenchen, Physik Department T39, Garching (Germany)
2010-07-15
We extend a recent calculation of the nuclear energy density functional in the framework of chiral perturbation theory by computing the isovector surface and spin-orbit terms: (vector {nabla}{rho}{sub p}-vector {nabla}{rho}{sub n}){sup 2} G{sub d}({rho})+(vector {nabla}{rho}{sub p}-vector {nabla}{rho}{sub n}).(vector J{sub p}-vector J{sub n})G{sub so}({rho})+(vector J{sub p}-vector J{sub n}){sup 2} G{sub J}({rho}) pertaining to different proton and neutron densities. Our calculation treats systematically the effects from 1 {pi} -exchange, iterated 1 {pi} -exchange, and irreducible 2{pi} -exchange with intermediate {delta} -isobar excitations, including Pauli-blocking corrections up to three-loop order. Using an improved density-matrix expansion, we obtain results for the strength functions G{sub d}({rho}), G{sub so}({rho}) and G{sub J}({rho}) which are considerably larger than those of phenomenological Skyrme forces. These (parameter-free) predictions for the strength of the isovector surface and spin-orbit terms as provided by the long-range pion-exchange dynamics in the nuclear medium should be examined in nuclear structure calculations at large neutron excess. (orig.)
Nuclear energy density functional from chiral pion-nucleon dynamics: Isovector terms
Kaiser, N.
2010-07-01
We extend a recent calculation of the nuclear energy density functional in the framework of chiral perturbation theory by computing the isovector surface and spin-orbit terms: (?c nabla ? _p - ?c nabla ? _n )2 G d( ?) + (?c nabla ? _p - ?c nabla ? _n (?c J_p - ?c J_n ) G so( ?) + (?c J_p - ?c J_n )2 G J( ?) pertaining to different proton and neutron densities. Our calculation treats systematically the effects from 1 ? -exchange, iterated 1 ? -exchange, and irreducible 2 ? -exchange with intermediate ? -isobar excitations, including Pauli-blocking corrections up to three-loop order. Using an improved density-matrix expansion, we obtain results for the strength functions G d( ?) , G so( ?) and G J( ?) which are considerably larger than those of phenomenological Skyrme forces. These (parameter-free) predictions for the strength of the isovector surface and spin-orbit terms as provided by the long-range pion-exchange dynamics in the nuclear medium should be examined in nuclear structure calculations at large neutron excess.
Quark cluster model in the three-nucleon system
International Nuclear Information System (INIS)
The quark cluster model is used to investigate the structure of the three-nucleon systems. The nucleon-nucleon interaction is proposed considering the colour-nucleon clusters and incorporating the quark degrees of freedom. The quark-quark potential in the quark compound bag model agrees with the central force potentials. The confinement potential reduces the short-range repulsion. The colour van der Waals force is determined. Then, the probability of quark clusters in the three-nucleon bound state systems are numerically calculated using realistic nuclear wave functions. The results of the present calculations show that quarks cluster themselves in three-quark systems building the quark cluster model for the trinucleon system. (author)
Cell Structure and Function Lessons
Ingrid Waldron
This overview presents key concepts that students often do not learn from standard textbook presentations and suggests a sequence of learning activities to help students understand how the parts of a cell work together to accomplish the multiple functions of a dynamic living cell. Suggested activities also reinforce student understanding of the relationships between molecules, organelles and cells, the diversity of cell structure and function, and the importance and limitations of diffusion. This overview provides links to Web resources, hands-on activities and discussion activities.
Energy Technology Data Exchange (ETDEWEB)
D. Day
2007-03-01
The nucleon form factors are still the subject of active investigation even after an experimental effort spanning 50 years. This is because they are of critical importance to our understanding of the electromagnetic properties of nuclei and provide a unique testing ground for QCD motivated models of nucleon structure. Progress in polarized beams, polarized targets and recoil polarimetry have allowed an important and precise set of data to be collected over the last decade. I will review the experimental status of elastic electron scattering from the nucleon along with an outlook for future progress.
Ou, Li
2015-01-01
Within the framework of the improved quantum molecular dynamics model, the medium modifications on the free nucleon-nucleon elastic cross sections are investigated. By using various in-medium nucleon-nucleon elastic cross sections in the model, the nucleon-induced reactions on various targets are simulated, and the excitation functions of reaction cross sections in the energy range from 25 MeV to 1 GeV are calculated. By comparing the calculations with the experimental data, an isospin, density, and momentum-dependence medium correction factor on free nucleon-nucleon elastic cross sections is determined.
Parton and valon distributions in the nucleon
International Nuclear Information System (INIS)
Structure functions of the nucleon are analyzed in the valon model in which a nucleon is assumed to be a bound state of three valence quark clusters (valons). At high Q2 the structure of the valons is described by leading-order results in the perturbative quantum chromodynamics. From the experimental data on deep-inelastic scattering off protons and neutrons, the flavor-dependent valon distributions in the nucleon are determined. Predictions for the parton distributions are then made for high Q2 without guesses concerning the quark and gluon distributions at low Q2. The sea-quark and gluon distributions are found to have a sharp peak at very small x. Convenient parametrization is provided which interpolates between different numbers of flavors
Parton and valon distributions in the nucleon
Hwa, Rudolph C.; Zahir, M. Sajjad
1981-06-01
Structure functions of the nucleon are analyzed in the valon model in which a nucleon is assumed to be a bound state of three valence quark clusters (valons). At high Q2 the structure of the valons is described by leading-order results in the perturbative quantum chromodynamics. From the experimental data on deep-inelastic scattering off protons and neutrons, the flavor-dependent valon distributions in the nucleon are determined. Predictions for the parton distributions are then made for high Q2 without guesses concerning the quark and gluon distributions at low Q2. The sea-quark and gluon distributions are found to have a sharp peak at very small x. Convenient parametrization is provided which interpolates between different numbers of flavors.
Spin and angular momentum in the nucleon
Gross, Franz; Pena, M T
2012-01-01
Using the covariant spectator theory (CST), we present the results of a valence quark-diquark model calculation of the nucleon structure function f(x) measured in unpolarized deep inelastic scattering (DIS), and the structure functions g1(x) and g2(x) measured in DIS using polarized beams and targets. Parameters of the wave functions are adjusted to fit all the data. The fit fixes both the shape of the wave functions and the relative strength of each component. Two solutions are found that fit f(x) and g1(x), but only one of these gives a good description of g2(x). This fit requires the nucleon CST wave functions contain a large D-wave component (about 35%) and a small P-wave component (about 0.6%). The significance of these results is discussed.
Spin and angular momentum in the nucleon
Energy Technology Data Exchange (ETDEWEB)
Franz Gross, Gilberto Ramalho, Teresa Pena
2012-05-01
Using the covariant spectator theory (CST), we present the results of a valence quark-diquark model calculation of the nucleon structure function f(x) measured in unpolarized deep inelastic scattering (DIS), and the structure functions g1(x) and g2(x) measured in DIS using polarized beams and targets. Parameters of the wave functions are adjusted to fit all the data. The fit fixes both the shape of the wave functions and the relative strength of each component. Two solutions are found that fit f(x) and g1(x), but only one of these gives a good description of g2(x). This fit requires the nucleon CST wave functions contain a large D-wave component (about 35%) and a small P-wave component (about 0.6%). The significance of these results is discussed.
Nucleon electromagnetic form factors
International Nuclear Information System (INIS)
Elastic electromagnetic nucleon form factors have long provided vital information about the structure and composition of these most basic elements of nuclear physics. The form factors are a measurable and physical manifestation of the nature of the nucleons' constituents and the dynamics that binds them together. Accurate form factor data obtained in recent years using modern experimental facilities has spurred a significant reevaluation of the nucleon and pictures of its structure; e.g., the role of quark orbital angular momentum, the scale at which perturbative QCD effects should become evident, the strangeness content, and meson-cloud effects. We provide a succinct survey of the experimental studies and theoretical interpretation of nucleon electromagnetic form factors
On the photon structure function
International Nuclear Information System (INIS)
The solution of the inhomogeneous evolution equations for the parton distributions of the photon in moment space with a general Born term and three arbitrary energy parameters has been investigated. In some special cases, the general solution can be reduced to the formulas which have been obtained by the previous papers. The differences between our result and those given by the previous papers for the photon structure function are significant not only numerically, but also in singularity behavior. (author). 10 refs
Structure function tests of QCD
International Nuclear Information System (INIS)
The problems involved in comparing QCD predictions with the Q2 evolution of deep inelastic structure functions are discussed. These involve the resummation of higher order terms approximately equal to (?sub(s) ln(1-z))sup(s) and the use of QCD perturbative analysis in the timelike domain. A comparison is made between theory and experiment for various QCD predictions with and without resummation of the dangerously large terms. The implications for the value of lambda are considered. (author)
The structure and function of fungal cells
Nozawa, Y.
1984-01-01
The structure and function of fungal cell walls were studied with particular emphasis on dermatophytes. Extraction, isolation, analysis, and observation of the cell wall structure and function were performed. The structure is described microscopically and chemically.
Nuclear structure functions at low-x in a holographic approach
Energy Technology Data Exchange (ETDEWEB)
Agozzino, Luca [Universita di Catania, Dipartimento di Fisica, Catania (Italy); INFN, Sezione di Catania, Catania (Italy); Castorina, Paolo [Universita di Catania, Dipartimento di Fisica, Catania (Italy); INFN, Sezione di Catania, Catania (Italy); CERN, PH Department, TH Unit, Geneva 23 (Switzerland); Colangelo, Pietro [INFN, Sezione di Bari, Bari (Italy)
2014-04-15
Nuclear effects in deep inelastic scattering at low x are phenomenologically described changing the typical dynamical and/or kinematical scales characterizing the free nucleon case. In a holographic approach, this rescaling is an analytical property of the computed structure function F{sub 2}(x, Q{sup 2}). This function is given by the sum of a conformal term and of a contribution due to quark confinement, depending on IR hard-wall parameter z{sub 0} and on the mean square distances, related to a parameter Q', among quarks and gluons in the target. The holographic structure function per nucleon in a nucleus A is evaluated showing that a rescaling of the typical nucleon size, z{sub 0} and Q', due to nuclear binding, can be reabsorbed in a Q{sup 2}-rescaling scheme. The difference between neutron and proton structure functions and the effects of the longitudinal structure functions can also be taken into account. The obtained theoretical results favorably compare with the experimental data. (orig.)
Unquenched simulations of four-nucleon interactions
International Nuclear Information System (INIS)
Exploratory simulations of four-nucleon interactions are performed taking into account the dynamical effects of internal nucleon loops. The four-nucleon interactions in the isoscalar and isovector channels are described by Yukawa interactions with auxiliary scalar fields. The nucleon mass and the average field lengths of the scalar fields are determined as a function of nucleon hopping parameter and Yukawa coupling strengths. There are no problems with ''exceptional configurations'' at strong couplings which make quenched simulations unreliable.
Parity doubling structure of nucleon at non-zero density in the holographic mean field theory
Directory of Open Access Journals (Sweden)
He Bing-Ran
2014-06-01
Full Text Available We summarize our recent work in which we develope the holographic mean field approach to study the dense baryonic matter in a bottom-up holographic QCD model including baryons and scalar mesons in addition to vector mesons. We first show that, at zero density, the rate of the chiral invariant mass of nucleon is controlled by the ratio of the infrared boundary values of two baryon fields included in the model. Then, at non-zero density, we find that the chiral condensate decreases with the increasing density indicating the partial restoration of the chiral symmetry. Our result shows that the more amount of the proton mass comes from the chiral symmetry breaking, the faster the effective nucleon mass decrease with density.
Conflicting Coupling of Unpaired Nucleons and the Structure of Collective Bands in Odd-Odd Nuclei
International Nuclear Information System (INIS)
The conflicting coupling of unpaired nucleons in odd-odd nuclei is discussed. A very simple explanation is suggested for the damping of the energy spacing of the lowest levels in the rotational bands in odd-odd nuclei with the 'conflicting' coupling of an odd proton and an odd neutron comparative to those of the bands based on the state of a strongly coupled particle in the neighboring odd nucleus entering the 'conflicting' configuration.
The isospin structure of photoproduction of ?? pairs from the nucleon in the threshold region
Kser, A.; Ahrens, J.; Annand, J. R. M.; Arends, H. J.; Bantawa, K.; Bartolome, P. A.; Beck, R.; Bekrenev, V.; Berghuser, H.; Braghieri, A.; Branford, D.; Briscoe, W. J.; Brudvik, J.; Cherepnya, S.; Costanza, S.; Demissie, B.; Dieterle, M.; Downie, E. J.; Drexler, P.; Fil'kov, L. V.; Fix, A.; Glazier, D. I.; Hamilton, D.; Heid, E.; Hornidge, D.; Howdle, D.; Huber, G. M.; Jahn, O.; Jaegle, I.; Jude, T. C.; Kashevarov, V. L.; Keshelashvili, I.; Kondratiev, R.; Korolija, M.; Kruglov, S. P.; Krusche, B.; Lisin, V.; Livingston, K.; MacGregor, I. J. D.; Maghrbi, Y.; Mancell, J.; Manley, D. M.; Marinides, Z.; McGeorge, J. C.; McNicoll, E.; Mekterovic, D.; Metag, V.; Micanovic, S.; Middleton, D. G.; Mushkarenkov, A.; Nikolaev, A.; Novotny, R.; Oberle, M.; Ostrick, M.; Otte, P.; Oussena, B.; Pedroni, P.; Pheron, F.; Polonski, A.; Prakhov, S. N.; Robinson, J.; Rosner, G.; Rostomyan, T.; Schumann, S.; Sikora, M. H.; Sober, D. I.; Starostin, A.; Supek, I.; Thiel, M.; Thomas, A.; Unverzagt, M.; Watts, D. P.; Werthmller, D.; Witthauer, L.
2015-09-01
Photoproduction of ??-pairs from nucleons has been investigated from threshold up to incident photon energies of ? 1.4 GeV. The quasi-free reactions ?p ? p?0 ?, ?n ? n?0 ?, ?p ? n?+ ?, and ?n ? p?- ? were for the first time measured from nucleons bound in the deuteron. The corresponding reactions from a free-proton target were also studied to investigate final-state interaction effects (for neutral pions the free-proton results could be compared to previous measurements; the ?p ? n?+ ? reaction was measured for the first time). For the ?0 ? final state coherent production via the ?d ? d?0 ? reaction was also investigated. The experiments were performed at the tagged photon beam of the Mainz MAMI accelerator using an almost 4? coverage electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. The total cross sections for the four different final states obey the relation ? (p?0 ?) ? ? (n?0 ?) ? 2 ? (p?- ?) ? 2 ? (n?+ ?) as expected for a dominant contribution from a ?? ? ?? (1232) ? ??N reaction chain, which is also supported by the shapes of the invariant-mass distributions of nucleon-meson and ?-? pairs. The experimental results are compared to the predictions from an isobar reaction model.
Precision measurement of the neutron spin dependent structure functions
International Nuclear Information System (INIS)
In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function g1n (x, Q2) of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized 3He target. The high beam energy allowed the author to extend the kinematic coverage compared to the previous SLAC experiments to 0.014 ? x ? 0.7 with an average Q2 of 5 GeV2. The author reports the integral of the spin dependent structure function in the measured range to be ?0.0140.7 dx g1n(x, 5 GeV2) = -0.036 0.004(stat.) 0.005(syst.). The author observes relatively large values of g1n at low x that call into question the reliability of data extrapolation to x ? 0. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. The author performs a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions g1p and g1n paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, the author evolves the data to Q2 = 5 GeV2, determines the first moments of the polarized structure functions of the proton and neutron, and finds agreement with the Bjorken sum rule
Non-singlet spin structure function in valon model
Energy Technology Data Exchange (ETDEWEB)
Taghavi Shahri, Fatemeh [School of Particles and Accelerators,IPM, Institute for Studies in Theoretical Physics and Mathematics, P.O.Box 19395-5531, Tehran (Iran); Arash, Firooz [Department of Physics, Tafresh University, Tafresh (Iran)
2009-07-01
We present a Next-to-leading order QCD calculation of non-singlet spin structure function g{sub 1}{sup NS}(x,Q{sup 2}), of the nucleon in the so-called the valon representation. The structure of the valon itself develops through the perturbative dressing of a valence quark in QCD, which is independent of the hosting hadron. The results of this calculations are in excellent agreement with the experimental data from HERMES collaborations for the entire measured range of x. It also provides an acceptable agreement with the older data from SMC, E143 and E155 experiments. We have further compared our results with those from AA, BB, GRSV, and DNS global fits.
Non-singlet spin structure function in valon model
International Nuclear Information System (INIS)
We present a Next-to-leading order QCD calculation of non-singlet spin structure function g1NS(x,Q2), of the nucleon in the so-called the valon representation. The structure of the valon itself develops through the perturbative dressing of a valence quark in QCD, which is independent of the hosting hadron. The results of this calculations are in excellent agreement with the experimental data from HERMES collaborations for the entire measured range of x. It also provides an acceptable agreement with the older data from SMC, E143 and E155 experiments. We have further compared our results with those from AA, BB, GRSV, and DNS global fits.
Bound-state quark and gluon contributions to structure functions in QCD
International Nuclear Information System (INIS)
One can distinguish two types of contributions to the quark and gluon structure functions of hadrons in quantum chromodynamics: ''intrinsic'' contributions, which are due to the direct scattering on the bound-state constituents, and ''extrinsic'' contributions, which are derived from particles created in the collision. In this talk, I discussed several aspects of deep inelastic structure functions in which the bound-state structure of the proton plays a crucial role: the properties of the intrinsic gluon distribution associated with the proton bound-state wavefunction; the separation of the quark structure function of the proton onto intrinsic ''bound-valence'' and extrinsic ''non-valence'' components which takes into account the Pauli principle; the properties and identification of intrinsic heavy quark structure functions; and a theory of shadowing and anti-shadowing of nuclear structure functions, directly related to quark-nucleon interactions and the gluon saturation phenomenon. 49 refs., 5 figs
Supramolecular Structure and Function 9
Pifat-Mrzljak, Greta
2007-01-01
The book is based on International Summer Schools on Biophysics held in Croatia which, contrary to other workshops centered mainly on one topic or technique, has very broad scope providing advanced training in areas related to biophysics. This volume is presenting papers in the field of biophysics for studying biological phenomena by using physical methods (NMR, EPR, FTIR, Mass Spectrometry, etc.) and/or concepts (predictions of protein-protein interactions, virtual ligand screening etc.). The interrelationship of supramolecular structures and there functions is enlightened by applications of principals of these physical methods in the biophysical and molecular biology context.
Energy Technology Data Exchange (ETDEWEB)
Babusci, D.; Giordano, G. [Laboratori Nationali di Frascati-INFN, Rome (Italy); Baghaei, H.; Cichocki, A. [Univ. of Virginia, Charlottesville, VA (United States); Blecher, M. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States); Breuer, M.; Commeaux, C.; Didelez, J.P. [IN2P3, Orsay (France); Caracappa, A. [Brookhaven National Lab., Upton, NY (United States); Fan, Q. [Syracuse Univ., NY (United States)] [and others
1995-12-31
Energy weighted integrals of the difference in helicity-dependent photo-production cross sections ({sigma}{sub {1/2}} - {sigma}{sub 3/2}) provide information on the nucleon`s Spin-dependent Polarizability ({gamma}), and on the spin-dependent part of the asymptotic forward Compton amplitude through the Drell-Hearn-Gerasimov (DHG) sum rule. (The latter forms the Q{sup 2}=0 limit of recent spin-asymmetry experiments in deep-inelastic lepton-scattering.) There are no direct measurements of {sigma}{sub {1/2}} or {sigma}{sub 3/2}, for either the proton or the neutron. Estimates from current {pi}-photo-production multipole analyses, particularly for the proton-neutron difference, are in good agreement with relativistic-l-loop Chiral calculations ({chi}PT) for {gamma} but predict large deviations from the DHG sum rule. Either (a) both the 2-loop corrections to the Spin-Polarizability are large and the existing multipoles are wrong, or (b) modifications to the Drell-Hearn-Gerasimov sum rule are required to fully describe the isospin structure of the nucleon. The helicity-dependent photo-reaction amplitudes, for both the proton and the neutron, will be measured at LEGS from pion-threshold to 470 MeV. In these double-polarization experiments, circularly polarized photons from LEGS will be used with SPHICE, a new frozen-spin target consisting of {rvec H} {center_dot} {rvec D} in the solid phase. Reaction channels will be identified in SASY, a large detector array covering about 80% of 4{pi}. A high degree of symmetry in both target and detector will be used to minimize systematic uncertainties.
Experimental Review of Photon Structure Function Data
Nisius, Richard
2009-01-01
The present knowledge of the structure of the photon is presented based on results obtained by measurements of photon structure functions at e+e- collider. Results are presented both for the QED structure of the photon as well as for the hadronic structure, where the data are also compared to recent parametrisations of the hadronic structure function F2gamma(x,Q^2). Prospects of future photon structure function measurements, especially at an International Linear Collider are...
Parity doubling structure of nucleon at non-zero density in the holographic mean field theory
He Bing-Ran; Harada Masayasu
2014-01-01
We summarize our recent work in which we develope the holographic mean field approach to study the dense baryonic matter in a bottom-up holographic QCD model including baryons and scalar mesons in addition to vector mesons. We first show that, at zero density, the rate of the chiral invariant mass of nucleon is controlled by the ratio of the infrared boundary values of two baryon fields included in the model. Then, at non-zero density, we find that the chiral condensate decreases with the inc...
Axial structure of the nucleon in a three-flavor chiral quark-meson model
International Nuclear Information System (INIS)
Nucleon matrix elements of the 0, 3 and 8 flavor components of the axial current are calculated in an SU(3)L x SU(3)R chiral quark-meson model. An extension of the Gell-Mann-Levy lagrangian with effects of meson mixing is used. The cranking projection method is applied. The results are consistent with the recent EMC experiment, reinterpreted by taking into account non-perturbative effects. In particular, I find a sizable value of the flavor singlet axial current matrix element and a negligible contribution of the ss-bar components. 36 refs., 3 figs., 3 tabs. (author)
Flavor asymmetry of the polarized nucleon sea
Nocera, Emanuele Roberto
2014-01-01
We discuss the flavor asymmetry of polarized light antiquarks in the nucleon, $\\Delta\\bar{u}-\\Delta\\bar{d}$. We present a determination of this quantity based on two global QCD analyses of experimental data, DSSV08 and NNPDFpol1.1, in which sea-quark parton distribution functions are determined respectively either from semi-inclusive deep-inelastic scattering or W-boson production data. The latter have become available only very recently, and their effect on the polarized flavor asymmetry is presented here for the first time. We find that the flavor asymmetry of polarized antiquarks in the nucleon is definitely positive, and has almost the same absolute size as its unpolarized counterpart. We compare this result with various theoretical models of the nucleon structure in order to test their validity. We show that some of them are clearly disfavored.
Strange / anti-strange asymmetry in the nucleon sea
Christiansen, H. R.; Magnin, J.
1998-12-01
We analyze the non-perturbative structure of the strange sea of the nucleon within a meson cloud picture. In a low Q2 approach in which the nucleon is viewed as a three valon bound state, we evaluate the probability distribution of an in-nucleon Kaon-Hyperon pair in terms of splitting functions and recombination. The resulting kaon and hyperon probability densities are convoluted with suitable strange distributions inside the meson and baryon in order to obtain non-perturbative contributions to the strange sea of the nucleon. We find a structured strange/anti-strange asymmetry, displaying a clear excess of quarks (anti-quarks) for large (small) momentum fractions.
pp Elastic Scattering in Near Forward Direction at LHC and Nucleon Structure
Islam, M M; Prokudin, A V
2005-01-01
We predict pp elastic differential cross section at LHC at the c.m. energy 14 TeV and momentum transfer range |t| = 0-10 GeV*2, which is planned to be measured by the TOTEM group. The field theory model underlying our phenomenological investigation describes the nucleon as a composite object with an outer cloud of quark-antiquark condensate, an inner core of topological baryonic charge, and a still smaller quark-bag of valence quarks. The model satisfactorily describes the asymptotic behavior of sigma-total(s) and rho(s) as well as the measured antiproton-proton elastic differential cross section at c.m. energies 546 GeV, 630 GeV, and 1.8 TeV. The large |t| elastic amplitude of the model incorporates the QCD hard pomeron (BFKL Pomeron plus next to leading order approximations), the perturbative dimensional counting behavior, and the confinement of valence quarks in a small region within the nucleon. Our predicted pp elastic differential cross section at LHC is compared with those of Bourrely et al. and Desgro...
Hupin, Guillaume; Quaglioni, Sofia; Navrtil, Petr
2015-05-29
We provide a unified abinitio description of the ^{6}Li ground state and elastic scattering of deuterium (d) on ^{4}He (?) using two- and three-nucleon forces from chiral effective field theory. We analyze the influence of the three-nucleon force and reveal the role of continuum degrees of freedom in shaping the low-lying spectrum of ^{6}Li. The calculation reproduces the empirical binding energy of ^{6}Li, yielding an asymptotic D- to S-state ratio of the ^{6}Li wave function in the d+? configuration of -0.027, in agreement with a determination from ^{6}Li-^{4}He elastic scattering, but overestimates the excitation energy of the 3^{+} state by 350keV. The bulk of the computed differential cross section is in good agreement with data. These results endorse the application of the present approach to the evaluation of the ^{2}H(?,?)^{6}Li radiative capture, responsible for the big-bang nucleosynthesis of ^{6}Li. PMID:26066431
Electromagnetic form factors of the bound nucleon
Lu, D. H.; Tsushima, K.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia); Williams, A. G.; Saito, K
1998-01-01
We calculate electromagnetic form factors of the proton bound in specified orbits for several closed shell nuclei. The quark structure of the nucleon and the shell structure of the finite nuclei are given by the QMC model. We find that orbital electromagnetic form factors of the bound nucleon deviate significantly from those of the free nucleon.
Structure Functions in Semihadronic $\\tau$ Decays
Colangelo, G; Mirkes, E; Urech, R; Colangelo, Gilberto; Finkemeier, Markus; Mirkes, Erwin; Urech, Res
1996-01-01
We review a variety of topics related to hadronic structure functions in exclusive semihadronic tau decays. We introduce the concept of structure functions and summarize the most important concepts. We then calculate the decay $\\tau \\to 3 \\pi \
Non-empirical energy density functional for the nuclear structure
International Nuclear Information System (INIS)
The energy density functional (EDF) formalism is the tool of choice for large-scale low-energy nuclear structure calculations both for stable experimentally known nuclei whose properties are accurately reproduced and systems that are only theoretically predicted. We highlight in the present dissertation the capability of EDF methods to tackle exotic phenomena appearing at the very limits of stability, that is the formation of nuclear halos. We devise a new quantitative and model-independent method that characterizes the existence and properties of halos in medium- to heavy-mass nuclei, and quantifies the impact of pairing correlations and the choice of the energy functional on the formation of such systems. These results are found to be limited by the predictive power of currently-used EDFs that rely on fitting to known experimental data. In the second part of this dissertation, we initiate the construction of non-empirical EDFs that make use of the new paradigm for vacuum nucleon-nucleon interactions set by so-called low-momentum interactions generated through the application of renormalization group techniques. These soft-core vacuum potentials are used as a step-stone of a long-term strategy which connects modern many-body techniques and EDF methods. We provide guidelines for designing several non-empirical models that include in-medium many-body effects at various levels of approximation, and can be handled in state-of-the art nuclear structure codes. In the present work, the first step is initiated through the adjustment of an operator representation of low-momentum vacuum interactions using a custom-designed parallel evolutionary algorithm. The first results highlight the possibility to grasp most of the relevant physics for low-energy nuclear structure using this numerically convenient Gaussian vertex. (author)
Alvioli, M; Kaptari, L P; Mezzetti, C B; Morita, H
2012-01-01
The nucleon momentum distribution n_A(k) for A=2, 3, 4, 16, and 40 nuclei is systematically analyzed in terms of wave functions resulting from advanced solutions of the non-relativistic Schr\\"{o}dinger equation, obtained within different many-body approaches and different realistic nucleon-nucleon (NN) interactions. In order to analyze and understand the frequently addressed question concerning the relationships between the nucleus, n_A(k), and the deuteron, n_D(k), momentum distributions, the spin(S)-isospin (T) structure of few-nucleon systems and complex nuclei is analyzed in terms of realistic NN interactions and many-body approaches. To this end the number of NN pairs in agiven (ST) state, viz. (ST)=(10), (00), (01), and (11), and the contribution of these states to the nucleon momentum distributions, are calculated. It is shown that, apart from the (00) state which has very small effects, all other spin-isospin states contribute to the momentum distribution in a wide range of momenta. It is shown that t...
Direct observation of quark-hadron duality in the free neutron F2 structure function
Niculescu, I.; Niculescu, G.; Melnitchouk, W.; Arrington, J.; Christy, M. E.; Ent, R.; Griffioen, K. A.; Kalantarians, N.; Keppel, C. E.; Kuhn, S.; Tkachenko, S.; Zhang, J.
2015-05-01
Using the recently published data from the BONuS (Barely Off-shell Nucleon Structure) experiment at Jefferson Lab, which utilized a spectator tagging technique to extract the inclusive electron-free neutron scattering cross section, we obtain the first direct observation of quark-hadron duality in the neutron F2 structure function. The data are used to reconstruct the lowest few (N =2 , 4, and 6) moments of F2 in the three prominent nucleon resonance regions, as well as the moments integrated over the entire resonance region. Comparison with moments computed from global parametrizations of parton distribution functions suggest that quark-hadron duality holds locally for the neutron in the second and third resonance regions down to Q2?1 GeV2 , with violations possibly up to 20% observed in the first resonance region.
The second moments of quark and gluon distribution functions in nucleon
International Nuclear Information System (INIS)
The second moments of quark and gluon distribution functions in proton are calculated on the basis of the QCD sum rule approach. The results obtained are in a good agreement with the experimental data
Study of the Three-Nucleon (e,e') Longitudinal Response Function with a New Approach
Dobretsov, V. Yu.; Efros, V D; Shao, Bin
1993-01-01
A new method for studying the many-body response functions is elaborated and first applied to the $^3$He longitudinal response. An integral transform of the response function is calculated from the bound-state-type equations for several versions of the N-N force. The equations are solved with the help of the hyperspherical expansion. The final-state interaction is completely taken into account. The results are compared with the integral transform of the experimental response...
Diakonov, D I; Diakonov, Dmitri; Petrov, Victor
2000-01-01
In the limit of large number of colors N the nucleon consisting of N quarks is heavy, and one can treat it semiclassically, like the large-Z Thomas--Fermi atom. The role of the semiclassical field binding the quarks in the nucleon is played by the pion or chiral field; its saddle-point distribution inside the nucleon is called the chiral soliton. The old Skyrme model for this soliton is an over-simplification. One can do far better by exploiting a realistic and theoretically-motivated effective chiral lagrangian presented in this paper. As a result one gets not only the static characteristics of the nucleon in a fair accordance with the experiment (such as masses, magnetic moments and formfactors) but also much more detailed dynamic characteristics like numerous parton distributions. We review the foundations of the Chiral Quark-Soliton Model of the nucleon as well as its recent applications to parton distributions, including the recently introduced `skewed' distributions, and to the nucleon wave function on ...
Structure and functions of fungal cell surfaces
Nozawa, Y.
1984-01-01
A review with 24 references on the biochemistry, molecular structure, and function of cell surfaces of fungi, especially dermatophytes: the chemistry and structure of the cell wall, the effect of polyene antibiotics on the morphology and function of cytoplasmic membranes, and the chemical structure and function of pigments produced by various fungi are discussed.
Structures and Functions of Oligosaccharins
Energy Technology Data Exchange (ETDEWEB)
Albersheim, Peter
1995-12-01
We have made considerable progress during the 2.5 year funding period just ending in our studies of the structures and functions of oligosaccharide signal molecules (oligosaccharins). We have emphasized studies of the enzymes that solubilize, process, and degrade oligosaccharins and of the proteins that inhibit those enzymes. We have been especially interested in elucidating how oligosaccharins and their processing enzymes participate in determining the outcome of challenges to plants by pathogenic microbes. We have studied, to a lesser extent, the roles of oligosaccharins in plant growth and development. Abstracts of papers describing results acquired with support from this grant that have been published, submitted, or in preparation are presented to summarize the progress made during the last two and one half years. The report highlights the most important contributions made in our oiigosaccharin research during this time period, and the corresponding abstract is referenced. Results of work in progress are described primarily in conjunction with our application for continued support.
Perturbative QCD study of the polarized structure function g1 at Next-to-Leading-Order
International Nuclear Information System (INIS)
A NLO perturbative study of all available data on polarized structure function g1(x,Q2) is presented. It is first explained how the Q2 evolution was performed using the DGLAP equations, which used with the present data, allow to constrain the behaviour of polarized parton distributions. Implications of such a study are discussed and important quantities are derived such as an estimation of the quark and gluon polarizations in the nucleon. (author)
Nuclear Dependence in Weak Structure Functions and the Determination of Weak Mixing Angle
Athar, M Sajjad; Simo, I Ruiz; Vacas, M J Vicente
2013-01-01
We have studied nuclear medium effects in the weak structure functions $F^A_2(x)$ and $F^A_3(x)$ and in the extraction of weak mixing angle using Paschos Wolfenstein(PW) relation. We have modified the PW relation for nonisoscalar nuclear target. We have incorporated the medium effects like Pauli blocking, Fermi motion, nuclear binding energy, nucleon correlations, pion $\\&$ rho cloud contributions, and shadowing and antishadowing effects.
Dynamical rescaling, the EMC effect and universality of hadron structure functions
International Nuclear Information System (INIS)
Data are compared on the EMC effect, with the hypothesis that the quark confinement size increases in going from a free nucleon to a nucleus. In QCD a dynamical rescaling is predicted: Q2 variation of the distribution function in a given target parallels the dependence on confinement size, R, at fixed Q2. Thus a dynamical scale invariance obtains when both R and Q2 are varied, yielding the dynamical rescaling relation F2sup(A)(x, Q2) = F2sup(N)(x, zetaQ2) where zeta > 1 is predicted for any nucleus and is a function of the confinement size. Data on 12 nuclei agree with this, implying that confinement size is governed by nuclear density. The formalism is tested by relating the pion and nucleon structure functions. (author)
Production cross sections of dimuons and experimental analysis of hadronic structure functions
International Nuclear Information System (INIS)
Analysis, by spectrometry (spectrometer Lezard NA3), of the particle structure (nucleons, mesons) and determination of a multiplicative factor (nearly 2) for the Drell-Yan cross section. Description of the experimental apparatus, production of dimuons on hydrogen and heavy nuclei (platinum), exploration of the nucleon (by inelastic diffusion of leptons, especially neutrinos, and use of the parton model), utilization of the Drell-Yan mechanism describing the production of a continuous spectrum of muons pairs (with experimental test), study of the effects (and subsequent corrections) of the quantum chromodynamics on the amplitude of the strong coupling and on the evolution of the hadronic structure observed as a function of the sensor energy, and at last, after presenting how data are processed analysis of the hadronic structure appearing during the pair production of muons of great masses (4.2< M??<8,5 GeV)
Airway Gland Structure and Function.
Widdicombe, Jonathan H; Wine, Jeffrey J
2015-10-01
Submucosal glands contribute to airway surface liquid (ASL), a film that protects all airway surfaces. Glandular mucus comprises electrolytes, water, the gel-forming mucin MUC5B, and hundreds of different proteins with diverse protective functions. Gland volume per unit area of mucosal surface correlates positively with impaction rate of inhaled particles. In human main bronchi, the volume of the glands is ?50 times that of surface goblet cells, but the glands diminish in size and frequency distally. ASL and its trapped particles are removed from the airways by mucociliary transport. Airway glands have a tubuloacinar structure, with a single terminal duct, a nonciliated collecting duct, then branching secretory tubules lined with mucous cells and ending in serous acini. They allow for a massive increase in numbers of mucus-producing cells without replacing surface ciliated cells. Active secretion of Cl(-) and HCO3 (-) by serous cells produces most of the fluid of gland secretions. Glands are densely innervated by tonically active, mutually excitatory airway intrinsic neurons. Most gland mucus is secreted constitutively in vivo, with large, transient increases produced by emergency reflex drive from the vagus. Elevations of [cAMP]i and [Ca(2+)]i coordinate electrolyte and macromolecular secretion and probably occur together for baseline activity in vivo, with cholinergic elevation of [Ca(2+)]i being mainly responsive for transient increases in secretion. Altered submucosal gland function contributes to the pathology of all obstructive diseases, but is an early stage of pathogenesis only in cystic fibrosis. PMID:26336032
Zahed, Ismail
2010-01-01
Recent developments in holography have provided a new vista to the nucleon composition. A strongly coupled core nucleon tied with vector mesons emerge in line with the Cheshire cat principle. The cat is found to hide in the holographic direction. We discuss the one, two and many baryon problem in this context and point at the striking similarities between the holographic results and recent lattice simulations at strong coupling.
Measuring spin-dependent structure functions at CEBAF
Energy Technology Data Exchange (ETDEWEB)
Schaefer, A. [Universitaet Frankfurt (Germany)
1994-04-01
The author analyses whether CEBAF with a 10 GeV beam could contribute significantly to the understanding of spin-dependent deep-inelastic scattering as well as semi-inclusive reactions. The main advantage of CEBAF is the much better attainable statistics, its great disadvantage its comparably low energy, which limits the accessible x-range to about 0.15 to 0.7. Within these constraints CEBAF could provide (1) high precision data which would be very valuable to understand the Q{sup 2} dependence of the spin-dependent structure functions g{sub 1}(x) and G{sub 2}(x) and (2) the by far most precise determination of the third moments of g{sub 1}(x) and g{sub 2}(x) the latter of which the author argues to be related to a fundamental property of the nucleon.
Energy Technology Data Exchange (ETDEWEB)
Jossten, Sylvester Johannes
2013-10-15
Multiplicities for the semi-inclusive production of each charge state of {pi}{sup {+-}} and K{sup {+-}} mesons in deep-inelastic scattering are presented as a function of the kinematic quantities x, Q{sup 2}, z and P{sub h} {sub perpendicular} {sub to}. The multiplicities were extracted from data collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams on a hydrogen or deuterium gas target. These results for identified hadrons constitute the most precise measurement to date, and will significantly enhance our understanding of the proton structure, as well as the fragmentation process in deep-inelastic scattering. Furthermore, the 3D binning at an unprecedented level of precision provides a handle to help disentangle the transverse momentum structure of both. The high level of precision coupled with an intermediate energy regime requires a careful study of the complex interaction between the experimental systematics, theoretical uncertainties, and the applicability of the factorization theorem within the standard framework of leading-twist collinear QCD. This is illustrated by the extraction of the valence quark ratio d{sub {nu}}/u{sub {nu}} at leading-order in {alpha}{sub s}. These results show a strong z-dependence below z {approx} 0.30, which could be interpreted as evidence for factorization breaking. This evidence weakens somewhat when isospin invariance of the fragmentation functions is assumed to be broken. Additionally, the multiplicities for the semi-inclusive production of {pi}{sup 0} mesons in deep-inelastic scattering are presented as a function of z. These multiplicities were extracted from the same data sample as used for the charged meson results. The neutral pion multiplicity is the same as the average charged pion multiplicity, up to z {approx} 0.70. This is consistent with isospin invariance below z {approx} 0.70. The results at high values of z show strong signs of isospin symmetry breaking.
Sensitivity to properties of the phi-meson in the nucleon structure in the chiral soliton model
International Nuclear Information System (INIS)
The influence of the ?-meson on the nucleon properties in the chiral soliton model is discussed. Properties of the ?-meson and its photo- and electroproduction are of fundamental interest to CEBAF and its possible future extension. The quark model assigns ? an s bar s structure, thus forbidding the radiative decay ???0?. Experimentally it is also found to be suppressed, yielding a branching fraction of 1.3x10-3. However, ???? and ???+?-?0 are not suppressed at all. Thus, it is possible to incorporate the widths of these decays into the framework of the chiral soliton model, by making use of a specific model for the compliance with OZI rule. Such a model is for example, the ?-? mixing model. Consequence of this in the context of a chiral soliton model, which builds on the ???a1(f1) meson effective Lagrangian, is the context of this report
Nucleon wave functions from lattice gauge theories: Renormalisation of baryonic operators
International Nuclear Information System (INIS)
We study the 3-quark operators which govern the short-distance and light-cone properties of the proton's wave function. In particular we obtain expressions for the matrix elements of these operators in a continuum renormalisation scheme in terms of those measured on a lattice. These matrix elements, which are not calculable in perturbative QCD, are required for the predictions of hard exclusive processes and in the calculation of the proton's lifetime in grand unified theories. (orig.)
Behavior of formfactors of nucleon resonances and quark-hadron duality
Davidovsky, V V
2002-01-01
Nucleon structure functions in the resonance region are investigated. Expressions for resonance production formfactors dependent on photon virtuality Q sup 2 , which have correct threshold behavior and take into account the available data on resonance decays, are obtained. The resonance part of nucleon structure functions is calculated. The manifestation of the quark-hadron duality in the behavior of the structure function F sub 2 is studied using the obtained expressions. The relation between the structure functions F sub 1 and F sub 2 in the resonance region is derived.
Use of quark wave functions in the calculation of structure functions of mesons
International Nuclear Information System (INIS)
In the description of deep-inelastic scattering the most extensively used model is the parton model. However, there has been an ongoing effort to understand structure functions of nucleons and mesons in terms of wave functions of quarks. Calculations made using the constituent quark model usually do not fit the experimental data. It has been argued that such calculations refer to some low-momentum scale parameterized by Q20. The calculated distribution is then evolved up to a large scale, Q2, by perturbative QCD evolution. The change needed if the distribution is to fit the data is quite large and, therefore, the scale Q20 is taken to be quite small. The large changes required for the distribution makes this procedure suspect. In this work we introduce a class of wave functions that are meant to apply at the scale Q2, so that evolution is not required. These wave functions describe the motion of a current quark, or parton, relative to a residual system. (In order to calculate a cross section the residual system is placed on mass shell in the calculation.) Our procedure is inherently asymmetric in the description of the struck particle and the residual system. We show how we are able to fit the (valence) structure function of the pion at Q2=20 GeV2 (without QCD evolution) using our scheme. copyright 1996 The American Physical Society
Structure and Function of Molecules and Cells
Ingrid Waldron
In this analysis and discussion activity, students learn how the function of molecules and cells is related to structure (including shape, constituent components, and relationships between components). Students analyze multiple examples of the relationship between structure and function in diverse proteins and eukaryotic cells. In addition, students learn that cells are dynamic structures with constant activity, students learn about emergent properties, and students engage in argument from evidence to evaluate three alternative claims concerning the relationship between structure and function.
Nucleon and nucleon-pair momentum distributions in A <= 12 nuclei
Wiringa, R B; Pieper, Steven C; Carlson, J
2013-01-01
We report variational Monte Carlo calculations of single-nucleon momentum distributions for A <= 12 nuclei and nucleon-pair and nucleon-cluster momentum distributions for A <= 8. The wave functions have been generated for a Hamiltonian containing the Argonne v18 two-nucleon and Urbana X three-nucleon potentials. The single-nucleon and nucleon-pair momentum distributions exhibit universal features attributable to the one-pion-exchange tensor interaction. The single-nucleon distributions are broken down into proton and neutron components and spin-up and spin-down components where appropriate. The nucleon-pair momentum distributions are given separately for pp and pn pairs. The nucleon-cluster momentum distributions include dp in 3He, tp and dd in 4He, alpha-d in 6Li, alpha-t in 7Li, and alpha-alpha in 8Be. Detailed tables are provided on-line for download.
International Nuclear Information System (INIS)
MENU close-quote 97 covered many stunning successes of chiral symmetry in intermediate energy reactions, especially of processes that involve pions. These successes include coupling constants, scattering lengths, threshold meson production, electric and magnetic polarizabilities of pions and nucleons, peripheral NN scattering, ?, ? and K decay rates and spectra. The ?N data bank at low energy, which in the past was notorious for the inconsistencies of different data sets, is shown to become consistent by deleting a modest number of previously accepted data sub-sets. There is a consensus on a better value for the pion-nucleon coupling constant, which has been a bone of contention earlier, namely, f?NN2/4?=(75.40.4)x10-3 in satisfactory agreement with the Goldberger-Treiman relation. The mass-spin/parity distribution of the experimentally established ?N resonances does not support the prediction of the harmonic oscillator type quark model. Some massive ?++ resonances decay by ? emission to the ?+p? final state. In contrast to this the decay of massive N* states to ?-p? in small, less than 5% of ?++??+p?. A new s-wave ? decay has been identified, D33(1700)?P33(1232)+?. There is interesting new threshold data from CELSIUS on np?d? as well as on pp?pp? and np?np?. copyright 1998 American Institute of Physics
Polarized structure functions in nuclear matter
International Nuclear Information System (INIS)
We present a comprehensive analysis of the structure functions for the polarized nuclei 3He, and focus on the polarized distribution functions and light-cone momentum distributions of protons and neutrons. We demonstrate that the first moment of the 3He structure function can provide an incisive test of the Bjorken sum rule.
International Nuclear Information System (INIS)
Some of the history behind the form of the wavefunctions of the nucleon and the delta in models of hadron structure is briefly reviewed. The possibility of D-state admixture and its magnitude is analyzed. Moreover the dynamical origin of such admixture and its observable consequences are investigated. Finally comments are given about some recent data analysis. 19 refs.; 1 table
The Jefferson Lab 12 GeV program on nucleon structure
Energy Technology Data Exchange (ETDEWEB)
Burkert, Volker D. [JLAB
2013-10-01
This slide-show presents the experiments planned at JLab with their 12 GeV upgrade. Experiments reported address: the use of hadron spectra as probes of QCD; the transverse structure of hadrons; the longitudinal structure of hadrons; the 3-dimensional structure of hadrons; hadrons and cold nuclear matter; and low-energy tests of the Standard Model and fundamental symmetries.
Precision measurement of the neutron spin dependent structure functions
Energy Technology Data Exchange (ETDEWEB)
Kolomensky, Y.G.
1997-02-01
In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function g{sub 1}{sup n} (x, Q{sup 2}) of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized {sup 3}He target. The high beam energy allowed the author to extend the kinematic coverage compared to the previous SLAC experiments to 0.014 {le} x {le} 0.7 with an average Q{sup 2} of 5 GeV{sup 2}. The author reports the integral of the spin dependent structure function in the measured range to be {integral}{sub 0.014}{sup 0.7} dx g{sub 1}{sup n}(x, 5 GeV{sup 2}) = {minus}0.036 {+-} 0.004(stat.) {+-} 0.005(syst.). The author observes relatively large values of g{sub 1}{sup n} at low x that call into question the reliability of data extrapolation to x {r_arrow} 0. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. The author performs a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions g{sub 1}{sup p} and g{sub 1}{sup n} paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, the author evolves the data to Q{sup 2} = 5 GeV{sup 2}, determines the first moments of the polarized structure functions of the proton and neutron, and finds agreement with the Bjorken sum rule.
The structure and function of cartilage proteoglycans
Directory of Open Access Journals (Sweden)
P J Roughley
2006-11-01
Full Text Available Cartilage contains a variety of proteoglycans that are essential for its normal function. These include aggrecan, decorin, biglycan, fibromodulin and lumican. Each proteoglycan serves several functions that are determined by both its core protein and its glycosaminoglycan chains. This review discusses the structure/function relationships of the cartilage proteoglycans, and the manner in which perturbations in proteoglycan structure or abundance can adversely affect tissue function.
Soma, V; Barbieri, C
2011-01-01
An ab-initio calculation scheme for finite nuclei based on self-consistent Green's functions in the Gorkov formalism is developed. It aims at describing properties of doubly-magic and semi-magic nuclei employing state-of-the-art microscopic nuclear interactions and explicitly treating pairing correlations through the breaking of U(1) symmetry associated with particle number conservation. The present paper introduces the formalism, necessary to undertake applications at (self-consistent) second-order using two-nucleon interactions, in a detailed and self-contained fashion. First applications of such a scheme will be reported soon in a forthcoming publication. Future works will extend the present scheme to include three-nucleon interactions and implement more advanced truncation schemes.
International Nuclear Information System (INIS)
An ab initio calculation scheme for finite nuclei based on self-consistent Green's functions in the Gorkov formalism is developed. It aims at describing properties of doubly magic and semimagic nuclei employing state-of-the-art microscopic nuclear interactions and explicitly treating pairing correlations through the breaking of U(1) symmetry associated with particle number conservation. The present paper introduces the formalism necessary to undertake applications at (self-consistent) second order using two-nucleon interactions in a detailed and self-contained fashion. First applications of such a scheme will be reported soon in a forthcoming publication. Future works will extend the present scheme to include three-nucleon interactions and implement more advanced truncation schemes.
Nucleon mass and pion loops Renormalization
ttel, M
2002-01-01
Using Dyson--Schwinger equations, the nucleon propagator is analyzed nonperturbatively in a field--theoretical model for the pion--nucleon interaction. Infinities are circumvented by using pion--nucleon form factors which define the physical scale. It is shown that the correct, finite, on--shell nucleon renormalization is important for the value of the mass--shift and the propagator. For physically acceptable forms of the pion--nucleon form factor the rainbow approximation together with renormalization is inconsistent. Going beyond the rainbow approximation, the full pion--nucleon vertex is modelled by its bare part plus a one--loop correction including an effective $\\Delta$. It is found that a consistent value for the nucleon mass--shift can be obtained as a consequence of a subtle interplay between wave function and vertex renormalization. Furthermore, the bare and renormalized pion--nucleon coupling constant are approximately equal, consistent with results from the Cloudy Bag Model.
From structure to function, via dynamics
Stetter, O.; Soriano, J.; Geisel, T.; Battaglia, D.
2013-01-01
Neurons in the brain are wired into a synaptic network that spans multiple scales, from local circuits within cortical columns to fiber tracts interconnecting distant areas. However, brain function require the dynamic control of inter-circuit interactions on time-scales faster than synaptic changes. In particular, strength and direction of causal influences between neural populations (described by the so-called directed functional connectivity) must be reconfigurable even when the underlying structural connectivity is fixed. Such directed functional influences can be quantified resorting to causal analysis of time-series based on tools like Granger Causality or Transfer Entropy. The ability to quickly reorganize inter-areal interactions is a chief requirement for performance in a changing natural environment. But how can manifold functional networks stem "on demand" from an essentially fixed structure? We explore the hypothesis that the self-organization of neuronal synchronous activity underlies the control of brain functional connectivity. Based on simulated and real recordings of critical neuronal cultures in vitro, as well as on mean-field and spiking network models of interacting brain areas, we have found that "function follows dynamics", rather than structure. Different dynamic states of a same structural network, characterized by different synchronization properties, are indeed associated to different functional digraphs (functional multiplicity). We also highlight the crucial role of dynamics in establishing a structure-to-function link, by showing that whenever different structural topologies lead to similar dynamical states, than the associated functional connectivities are also very similar (structural degeneracy).
Liuti, S.; Gross, Franz; Gladshev, V.
1995-05-01
The A-dependence of nuclear deep inelastic structure functions, FA2(x), is investigated within the Relativistic Impulse Approximation (RIA). By expanding to first order in the perpendicular momentum squared, k2?, of the bound nucleons, we are able to fully understand the behavior of FA2(x) for x?0.5. The A-dependence of nuclear structure functions which emerges from this analysis is used to extract the ratio of the neutron to proton structure functions, R(x)=Fn2(x)/Fp2(x) at x?1, from data on both deuteron and complex nuclei.
New results from deep inelastic muon-nucleon scattering
International Nuclear Information System (INIS)
New results obtained by three distinct muon-nucleon scattering experiments are reviewed. They concern the F2 structure function measurements, the open and hidden charm production from multimuon events, and the evidence for forward jets and forward protons/antiprotons production from hadronic final states
{sup 3}He and {sup 3}H polarized structure functions, using the constituent quark model
Energy Technology Data Exchange (ETDEWEB)
Yazdanpanah, M.M., E-mail: Myazdan@mail.uk.ac.i [Physics Department, Kerman Shahid Bahonar University, Kerman (Iran, Islamic Republic of); School of Particles and Accelerators, IPM (Institute for Studies in Theoretical Physics and Mathematics), PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Mirjalili, A., E-mail: Mirjalili@ipm.i [Physics Department, Yazd University, 89195-741, Yazd (Iran, Islamic Republic of); School of Particles and Accelerators, IPM (Institute for Studies in Theoretical Physics and Mathematics), PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Tehrani, S. Atashbar, E-mail: Atashbar@ipm.i [School of Particles and Accelerators, IPM (Institute for Studies in Theoretical Physics and Mathematics), PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Taghavi-Shahri, F., E-mail: F_Taghavi@mail.ipm.i [School of Particles and Accelerators, IPM (Institute for Studies in Theoretical Physics and Mathematics), PO Box 19395-5531, Tehran (Iran, Islamic Republic of)
2009-12-15
We calculate polarized structure functions for {sup 3}He and {sup 3}H, using the convolution of the light cone momentum distribution with the polarized structure of the proton and neutron. The polarized structure function of the nucleon is computed using the constituent quark model. Hypergeometric orthogonal polynomials are employed to extract the unknown parameters in this phenomenological approach. These hypergeometric polynomials are placed at the third level of Askey scheme with two free parameters. The results obtained for the polarized nuclear structure functions and the ratio of the Bjorken sum rule for proton-neutron system to {sup 3}He-{sup 3}H system are in good agreement with the available experimental data and some theoretical models. To improve the validity of the model at low x-values, the nuclear shadowing, antishadowing and DELTA-resonance effects are also considered.
Neurotransmitter transporters: structure meets function
Focke, Paul; WANG, XIAOYU; Larsson, H. Peter
2013-01-01
At synapses, sodium-coupled transporters remove released neurotransmitters, thereby recycling them and maintaining a low extracellular concentration of the neurotransmitter. The molecular mechanism underlying sodium-coupled neurotransmitter uptake is not completely understood. Several structures of homologues of human neurotransmitter transporters have been solved with X-ray crystallography. These crystal structures have spurred a plethora of computational and experimental work to elucidate t...
Nuclear Structure Functions at Low-$x$ in a Holographic Approach
Agozzino, LucaDipartimento di Fisica, Universit di Catania, via S. Sofia 62, 95125, Catania, Italy; Castorina, Paolo; Colangelo, Pietro
2014-01-01
Nuclear effects in deep inelastic scattering at low x are phenomenologically described changing the typical dynamical and/or kinematical scales characterizing the free nucleon case. In a holographic approach, this rescaling is an analytical property of the computed structure function F2(x,Q2) . This function is given by the sum of a conformal term and of a contribution due to quark confinement, depending on IR hard-wall parameter z0 and on the mean square distances, related to a parameter Q? ...
A study of nuclear effect in $F_3$ structure function in the deep inelastic $\
Athar, M Sajjad; Singh, S K; Vacas, M J Vicente
2009-01-01
We study nuclear effect in the $F^A_3(x)$ structure function in the deep inelastic neutrino reactions on iron by taking into account Fermi motion, binding, target mass correction, shadowing and anti-shadowing corrections. Calculations have been done in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations for nuclear matter. Results for $F^A_3(x)$ have been compared with the results reported at NuTeV and also with some of the older experiments reported in the literature.
Sensitivity to properties of the phi-meson in the nucleon structure in the chiral soliton model
Energy Technology Data Exchange (ETDEWEB)
Mukhopadhyay, N.C.; Zhang, L. [Rensselaer Polytechnic Inst., Troy, NY (United States)
1994-04-01
The influence of the {phi}-meson on the nucleon properties in the chiral soliton model is discussed. Properties of the {phi}-meson and its photo- and electroproduction are of fundamental interest to CEBAF and its possible future extension. The quark model assigns {phi} an s{bar s} structure, thus forbidding the radiative decay {phi}{yields}{pi}{sup 0}{gamma}. Experimentally it is also found to be suppressed, yielding a branching fraction of 1.3{times}10{sup {minus}3}. However, {phi}{yields}{rho}{pi} and {phi}{yields}{pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} are not suppressed at all. Thus, it is possible to incorporate the widths of these decays into the framework of the chiral soliton model, by making use of a specific model for the compliance with OZI rule. Such a model is for example, the {omega}-{phi} mixing model. Consequence of this in the context of a chiral soliton model, which builds on the {pi}{rho}{omega}a{sub 1}(f{sub 1}) meson effective Lagrangian, is the context of this report.
Low x physics, deep inelastic scattering and structure functions
International Nuclear Information System (INIS)
HERA experiments together with polarised fixed target lepton-nucleon scattering experiments and hadron-hadron interactions have provided this year a wealth of new results on the structure of the proton and on low x physics where x is the fraction of nucleon momentum carried by the struck quark in lepton a scattering. Measurement o the W charge asymmetry in CDF at FNAL has provided new constraints on the d/u ratio in the proton. The Drell-Yan asymmetry (?pp - ?pn)/(?pp + ?pn) measured by the NA51 experiment at CERN confirms that there are more of anti d than anti u in the proton. New data on proton, deuteron and neutron polarized structure functions from the SLAC E143 and CERN SMC experiments are in good agreement. The naive Ellis-Jaffe sum rule is violated by at least two standard deviations and the Bjorken Sum rule is verified to within about 10%. The measured QCD corrections to the Bjorken Sum Rule using the low Q2 data from E143 provide a new method to determine the QCD running coupling constant ?5. Combining fixed target data from E665 and FNAL and HERA results from H1 and ZEUS, the measurements of the proton structure function F2(x,Q2) cover the very large kinematic range of 0.3 2 4 GeV2 and 2.10-4 2 with x decreasing is observed at x values below 10-1 and up to Q2 values of about 1000 GeV2. The interpretation of the F2 behaviour at low x by the BFKL and GLAP mechanisms is discussed together with possible ''footprints'' of the BFKL dynamics in the hadronic final states of deep inelastic scattering events at HERA. The properties of the deep inelastic scattering events at HERA with no energy in a large gap of rapidity close to the proton direction are reviewed. A signal from rapidity gap events in CDF and DO experiments is presented. (author). 102 refs., 31 figs., 5 tabs
Unquenched simulations of four-nucleon interactions
Energy Technology Data Exchange (ETDEWEB)
Montvay, I.
2012-10-15
Exploratory simulations of four-nucleon interactions are performed taking into account the dynamical effects of internal nucleon loops. The four-nucleon interactions in the isoscalar and isovector channels are described by Yukawa interactions with auxiliary scalar fields. The nucleon mass and the average field lengths of the scalar fields are determined as a function of nucleon hopping parameter and Yukawa coupling strengths. There are no problems with ''exceptional configurations'' at strong couplings which make quenched simulations unreliable.
International Nuclear Information System (INIS)
Enormous technical and economic benefits have been conferred on the industry in many countries by the application of nucleonic gauging. The last few years have witnessed many important advances in the field. Basically radioisotope instruments are used to measure a variety of physical properties of material in solid, liquid and gaseous state and many of them are designed to work in the industrial plants and fields under rigorous conditions
Cell Membrane Structure and Function
VU Bioengineering RET Program,
Students learn about the different structures that comprise cell membranes, fulfilling part of the Research and Revise stages of the legacy cycle. They view online animations of cell membrane dynamics (links provided). Then they observe three teacher demonstrations that illustrate diffusion and osmosis concepts, as well as the effect of movement through a semi-permeable membrane using Lugol's solution.
Neurotransmitter transporters: structure meets function.
Focke, Paul J; Wang, Xiaoyu; Larsson, H Peter
2013-05-01
At synapses, sodium-coupled transporters remove released neurotransmitters, thereby recycling them and maintaining a low extracellular concentration of the neurotransmitter. The molecular mechanism underlying sodium-coupled neurotransmitter uptake is not completely understood. Several structures of homologs of human neurotransmitter transporters have been solved with X-ray crystallography. These crystal structures have spurred a plethora of computational and experimental work to elucidate the molecular mechanism underlying sodium-coupled transport. Here, we compare the structures of GltPh, a glutamate transporter homolog, and LeuT, a homolog of neurotransmitter transporters for the biogenic amines and inhibitory molecules GABA and glycine. We relate these structures to data obtained from experiments and computational simulations, to draw conclusions about the mechanism of uptake by sodium-coupled neurotransmitter transporters. Here, we propose how sodium and substrate binding is coupled and how binding of sodium and substrate opens and closes the gates in these transporters, thereby leading to an efficient coupled transport. PMID:23664361
Transversity and Transverse Spin in Nucleon Structure through SIDIS at Jefferson Lab
Afanasev, A; Avakian, H; Cates, G; Chen, J P; Chudakov, E; Cisbani, E; De Jager, C; Gamberg, L; Gao, H; Garibaldi, F; Jiang, X; Kumar, K S; Meziani, Z E; Mulders, P J; Peng, J C; Qian, X; Schlegel, M; Souder, P; Yuan, F; Zhu, L
2007-01-01
The JLab 12 GeV upgrade with a proposed solenoid detector and the CLAS12 detector can provide the granularity and three-dimensional kinematic coverage in longitudinal and transverse momentum, $0.1\\le x \\le 0.5$, $0.3 \\le z \\le 0.7$ with $P_T \\le 1.5 {\\rm GeV}$ to precisely measure the leading twist chiral-odd and $T$-odd quark distribution and fragmentation functions in SIDIS. The large $x$ experimental reach of these detectors with a 12 GeV CEBAF at JLab makes it {\\em ideal} to obtain precise data on the {\\em valence-dominated} transversity distribution function and to access the tensor charge.
Structure functions in semihadronic tau decays
International Nuclear Information System (INIS)
We review a variety of topics related to hadronic structure functions in exclusive semihadronic tau decays. We introduce the concept of structure functions and summarize the most important concepts. We then calculate the decay ??3??? for very small hadronic invariant mass to one loop in chiral perturbation theory. New interesting features emerge with respect to the known results at tree level, in particular for the structure functions wD and wE. We discuss the prospects for experimental verification of our predictions. Finally, we discuss various issues at higher Q2, related to hadronic resonance physics. Here we consider 2?, ?K, 3?, K?K and ?K? hadronic final states. (orig.)
Comparing some nucleon-nucleon potentials
Naghdi, M.
2014-07-01
The aim is to compare a few Nucleon-Nucleon (NN) potentials especially Reid68, Reid68-Day, Reid93, UrbanaV14, ArgonneV18, Nijmegen 93, Nijmegen I and Nijmegen II. Although these potentials have some likenesses and are almost phenomenological, they include in general different structures and their own characteristics. The potentials are constructed in a manner that fit NN scattering data or phase shifts and are compared in this way. A high-quality scale of a potential is that it fits the data with ?2/ N data ? 1, describes well the deuteron properties and gives satisfactory results in nuclear-structure calculations. However, these scales have some failures. Here, we first compare many potentials by confronting them with the data. Then, we try to compare the potential forms by considering the potential structures directly and therefore regarding their substantial bases somehow. To do so, we note that since the potentials are written in different schemas, it is necessary to write them in a unique schema. On the other hand, because three major terms in the NN interaction are central, tensor and spin-orbit terms; so, to perform a reduction plan and arrive at a common structure, we choose the Reid's potential form. Next, we compare the potentials for some states and address some other related issues as well.
The dynamic of diffractive structure functions
Monfared, S Taheri; Tehrani, S Atashbar
2011-01-01
We extract diffractive parton distribution functions (DPDFs) and diffractive structure functions from the most recent H1 and ZEUS diffractive DIS data obtained by various methods. We consider Pomeron as an object with parton distribution function, evolving according to the next-to-leading order (NLO) DGLAP equations within the framework of the `Fixed Flavour Number Scheme' (FFNS). Having performed a global fit analysis, we achieve a very good description of all available measurements by introducing a new set of quark distribution form for the Pomeron. We predict longitudinal and charm proton diffractive structure function as well. Our results are compared with other analysis from the literature.
Extraction of the neutron structure function F2n from inclusive scattering data on composite nuclei
Rinat, A. S.; Taragin, M. F.
2003-01-01
We consider a generalized convolution, linking structure functions (SF) FN2 for nucleons, FA2 for a physical nucleus and fPN,A for a nucleus, composed of point-nucleons. In order to extract F2n we employ data on F2p,A and the computed fPN,A. Only for Q2?3.5 GeV2 do data permit the extraction of F2A(x,3.5) over a sufficiently wide x-range. Applying Mellin transforms, the above relation between SF turns into an algebraic one, which one solves for the Mellin transform of the unknown F2n. We present inversion methods leading to the desired F2n, all using a parametrization for C(x,Q2)=F2n(x,Q2)/F2p(x,Q2). Imposing motivated constraints, the simplest parametrization leaves one free parameter C(x=1,Q2). For Q2=3.5 GeV2 its average over several targets and different methods is =0.540.03. We argue that for the investigated Q2, C(x?1,3.5) is determined by the nucleon-elastic (NE) part of SF. A calculation of the latter comes close to the extracted value. Both are close to the SU(6) limit uV(x,3.5)=2dV(x,3.5) for parton distribution functions.
New Parametrizations for the Photon Structure Function
International Nuclear Information System (INIS)
In the last year four new parametrizations of the Hadronic Photon Structure Function at Next to Leading Order have appeared. In this talk, I briefly review the main features of the three of them: the FFNSCJK, CJK and AFG. (author)
Snake Jaws: Connecting Structure and Function
2010-11-17
In this lesson designed to enhance literacy skills, students learn how animals' physical characteristics, such as jaw structure, are directly related to the function they perform when the animal interacts with its environment.
Structure Function Studies for Turbulent Interstellar Medium
Sun, X H; Han, J.L.
2004-01-01
We study structure functions of rotation measures in the Canadian Galactic Plane Survey (CGPS) region and the North Galactic Pole (NGP) to extract the interstellar medium (ISM) fluctuation information. The CGPS data are divided into three longitude intervals: $82^\\circ
Network structure shapes spontaneous functional connectivity dynamics.
Shen, Kelly; Hutchison, R Matthew; Bezgin, Gleb; Everling, Stefan; McIntosh, Anthony R
2015-04-01
The structural organization of the brain constrains the range of interactions between different regions and shapes ongoing information processing. Therefore, it is expected that large-scale dynamic functional connectivity (FC) patterns, a surrogate measure of coordination between brain regions, will be closely tied to the fiber pathways that form the underlying structural network. Here, we empirically examined the influence of network structure on FC dynamics by comparing resting-state FC (rsFC) obtained using BOLD-fMRI in macaques (Macaca fascicularis) to structural connectivity derived from macaque axonal tract tracing studies. Consistent with predictions from simulation studies, the correspondence between rsFC and structural connectivity increased as the sample duration increased. Regions with reciprocal structural connections showed the most stable rsFC across time. The data suggest that the transient nature of FC is in part dependent on direct underlying structural connections, but also that dynamic coordination can occur via polysynaptic pathways. Temporal stability was found to be dependent on structural topology, with functional connections within the rich-club core exhibiting the greatest stability over time. We discuss these findings in light of highly variable functional hubs. The results further elucidate how large-scale dynamic functional coordination exists within a fixed structural architecture. PMID:25855174
Recent Structure Function Results from CCFR
Fleming, B T; Alton, A; Arroyo, C G; Avvakumov, S; De Barbaro, L; De Barbaro, P; Bazarko, A O; Bernstein, R H; Bodek, Arie; Bolton, T; Brau, J E; Buchholz, D; Budd, H S; Bugel, L; Conrad, J; Drucker, R B; Formaggio, J A; Frey, R; Goldman, J; Goncharov, M; Harris, D A; Johnson, R A; Kim, J H; King, B J; Kinnel, T; Koutsoliotas, S; Lamm, M J; Marsh, W; Mason, D; McFarland, K S; McNulty, C; Mishra, S R; Naples, D; Nienaber, P; Romosan, A; Sakumoto, W K; Schellman, H; Sciulli, F J; Seligman, W G; Shaevitz, M H; Smith, W H; Spentzouris, P; Stern, E G; Vakili, M; Vaitaitis, A G; Yang, U K; Yu, J; Zeller, G P; Zimmerman, E D
2000-01-01
A new structure function analysis of CCFR deep inelastic nu-N and nubar-N scattering data is presented for previously unexplored kinematic regions down to Bjorken x=0.0045 and Q^2=0.3 GeV^2. Comparisons to charged lepton scattering data from NMC and E665 experiments are made and the behavior of the structure function F2_nu is studied in the limit Q^2 -> 0
Comparing Some Nucleon-Nucleon Potentials
Naghdi, M
2013-01-01
The aim is to compare a few Nucleon-Nucleon (NN) potentials especially Reid68, Reid68-Day, Reid93, UrbanaV14, ArgonneV18, Nijmegen 93, Nijmegen I, Nijmegen II. Although these potentials have some likenesses and are almost phenomenological, they include in general different structures and its own characteristics. The potentials are constructed in a manner that fit the NN scattering data or phase shifts and are compared in this way. A high-quality scale of a potential is that it fits the data with $\\chi^{2}/N_{data} \\approx 1$, describes well deuteron properties or gives satisfactory results in nuclear structure calculations. However, these scales have some failures. Here, we first compare many potentials by confronting with data. Then, we try to compare the potential forms by considering the potential structures directly and therefore regarding their substantial basis somehow. On the other hand, since the potentials are written in different schema, it is necessary to write the potentials in a unique schema to ...
New model for nucleon generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Radyushkin, Anatoly V. [JLAB, Newport News, VA (United States)
2014-01-01
We describe a new type of models for nucleon generalized parton distributions (GPDs) H and E. They are heavily based on the fact nucleon GPDs require to use two forms of double distribution (DD) representations. The outcome of the new treatment is that the usual DD+D-term construction should be amended by an extra term, {xi} E{sub +}{sup 1} (x,{xi}) which has the DD structure {alpha}/{beta} e({beta},{alpha}, with e({beta},{alpha}) being the DD that generates GPD E(x,{xi}). We found that this function, unlike the D-term, has support in the whole -1 <= x <= 1 region. Furthermore, it does not vanish at the border points |x|={xi}.
Spectral Density Functionals for Electronic Structure Calculations
Savrasov, S Y
2001-01-01
We introduce a functional of the local spectral electron density which can be used to to compute the total energy and the local spectral function of strongly-correlated materials. We illustrate the applicability of the method by using as an example the long-standing problem of the electronic structure of metallic plutonium.
International Nuclear Information System (INIS)
It is possible to measure the deep-inelastic spin-dependent structure functions g1/sup p/(x) and g1/sup n/(x) for the proton and neutron using internal polarized hydrogen, deuterium, and 3He targets of polarization 50% and thickness 1014 to 1015 cm-2 and the 60 mA longitudinally polarized 30 GeV electron beam in the HERA electron storage ring. The measurement of the deep-inelastic spin-structure of both isospin states of the nucleon at the same kinematics and using the same apparatus allows the Bjorken sum rule to be experimentally checked. In addition, it uniquely constrains the spin distribution of the u and d quarks as a function of x in any model of the nucleon. Possible target and detector configurations are described and an estimate of the accuracy of such a measurement is presented
First measurement of the gluon polarisation in the nucleon using D mesons at COMPASS
von Hodenberg, Martin
2005-01-01
The complicated structure of the nucleon has been studied with great success in deep-inelastic lepton-nucleon scattering (DIS) experiments at CERN, SLAC and DESY. As a result the unpolarised structure functions have been measured accurately over a wide kinematic range. From these measurements it is possible to determine the gluon density in the nucleon with good accuracy via a so-called QCD fit. In the case of the spin structure of the nucleon the situation is different. Even after decades of experimental and theoretical efforts it remains to be understood how the spin of the nucleon of 1/2 in units of h-bar is to be accounted for in terms of contributions from the quarks and gluons inside the nucleon. Of particular interest is the question whether the polarised gluon density can explain the unexpected smallness of the quark contribution to the nucleon spin. The QCD fit, which worked well in the unpolarised case, yields a polarised gluon density Delta G which is only badly constrained. This is due to the fact...
International Nuclear Information System (INIS)
In the framework of the Quantum Chromodynamics (QCD), the nucleon is described as being composed of three valence quarks surrounded by a sea of virtual quark-antiquark pairs and gluons. If the role of this virtual sea in the nucleon properties is inferred to be important, this contribution is still poorly understood. In this context, we study the role of the strange quarks in the nucleon since this is the lightest quark flavor of the sea with no valence contribution. We are determining its contribution to the charge and magnetization distributions in the nucleon via parity violation experiments. The measurement is performed by elastically scattering polarized electrons from nucleon target. A world wide program in which the G0 experiment takes place has been performing for a decade. The G0 experiment and the analysis of the results from its forward angles phase are the topics of this thesis. This document presents the physics case of the strangeness content of the nucleon (mass, spin, impulsion). It describes also the formalism related to the electroweak probe and the form factors, and then the principle of parity violating asymmetry measurement. The G0 experimental setup, which was built and installed in the Hall C of the Jefferson Laboratory (Usa), is detailed. This set-up was designed for the measurement of asymmetries of the order of 10-6 with an overall relative uncertainty better than 10 %, over a momentum transfer range 0.1-1 (GeV/c)2. The various steps of the data analysis are exposed. They have allowed us to start from measured counting rates to reach parity violating physics asymmetries. This required a careful treatment of the various sources of systematical errors which is discussed extensively. Finally the results from the G0 forward angle measurement, its comparison with others experiments and with theoretical models, are presented. They support a non null strange quark contribution. (author)
Analytic approach to small x structure functions
International Nuclear Information System (INIS)
We present a method for the analytical solution of small x structure functions. The essential small x logarithms are summed to all orders in the anomalous dimensions and coefficient functions. Although we work at leading logarithmic accuracy, the method is general enough to allow the systematic inclusion of sub-leading logarithms. Results and predictions are presented for the gluon density, and the structure functions F2(x,Q2) and FL(x,Q2). We find that corrections to the simple double logarithmic calculation are important in the HERA range and obtain good fits to all available data. (author)
Structure functions in the chiral bag model
Energy Technology Data Exchange (ETDEWEB)
Sanjose, V.; Vento, V.
1989-07-13
We calculate the structure functions of an isoscalar nuclear target for the deep inelastic scattering by leptons in an extended version of the chiral bag model which incorporates the qanti q structure of the pions in the cloud. Bjorken scaling and Regge behavior are satisfied. The model calculation reproduces the low-x behavior of the data but fails to explain the medium- to large-x behavior. Evolution of the quark structure functions seem inevitable to attempt a connection between the low-energy models and the high-energy behavior of quantum chromodynamics. (orig.).
Kaiser, N
2003-01-01
We calculate the imaginary parts of the isoscalar scalar and isovector electromagnetic form factors of the nucleon up to two-loop order in chiral perturbation theory. Particular attention is paid on the correct behavior of Im $\\sigma_N(t)$ and Im $G_{E,M}^V(t)$ at the two-pion threshold $t_0=4 m_\\pi^2$ in connection with the non-relativistic 1/M-expansion. We recover the well-known strong enhancement near threshold originating from the nearby anomalous singularity at $t_c = ...
Magnetism and Structure in Functional Materials
Planes, Antoni; Saxena, Avadh
2005-01-01
Magnetism and Structure in Functional Materials addresses three distinct but related topics: (i) magnetoelastic materials such as magnetic martensites and magnetic shape memory alloys, (ii) the magnetocaloric effect related to magnetostructural transitions, and (iii) colossal magnetoresistance (CMR) and related magnanites. The goal is to identify common underlying principles in these classes of materials that are relevant for optimizing various functionalities. The emergence of apparently different magnetic/structural phenomena in disparate classes of materials clearly points to a need for common concepts in order to achieve a broader understanding of the interplay between magnetism and structure in this general class of new functional materials exhibiting ever more complex microstructure and function. The topic is interdisciplinary in nature and the contributors correspondingly include physicists, materials scientists and engineers. Likewise the book will appeal to scientists from all these areas.
Spin-orbit coupling in nuclei and realistic nucleon-nucleon potentials
Kaiser, N.
2004-09-01
We analyze the spin-orbit coupling term in the nuclear energy density functional in terms of a zero-range NN-contact interaction and finite-range contributions from two-pion exchange. We show that the strength of the spin-orbit contact interaction as extracted from high-precision nucleon-nucleon potentials is in perfect agreement with that of phenomenological Skyrme forces employed in non-relativistic nuclear structure calculations. Additional long-range contributions from chiral two-pion exchange turn out to be relatively small. These explicitly density-dependent contributions reduce the ratio of the isovector to the isoscalar spin-orbit strength significantly below the Skyrme value 1/3 . We perform a similar analysis for the strength function of the (??)2 -term and find values not far from those of phenomenological Skyrme parametrizations.
Spin-orbit coupling in nuclei and realistic nucleon-nucleon potentials
Kaiser, N
2004-01-01
We analyze the spin-orbit coupling term in the nuclear energy density functional in terms of a zero-range NN-contact interaction and finite-range contributions from two-pion exchange. We show that the strength of the spin-orbit contact interaction as extracted from high-precision nucleon-nucleon potentials is in perfect agreement with that of phenomenological Skyrme forces employed in non-relativistic nuclear structure calculations. Additional long-range contributions from chiral two-pion exchange turn out to be relatively small. These explicitly density-dependent contributions reduce the ratio of the isovector to the isoscalar spin-orbit strength significantly below the Skyrme value 1/3. We perform a similar analysis for the strength function of the $(\\vec \
Nucleon-pion-state contributions in the determination of the nucleon axial charge
Bar, Oliver
2015-01-01
The nucleon-pion-state contributions to QCD 2- and 3-point functions used in the calculation of the nucleon axial charge are studied in chiral perturbation theory. For sufficiently small quark masses and large volumes the nucleon-pion states are expected to have smaller total energy than the single-particle excited states. To leading order in chiral perturbation theory the results do not depend on low-energy constants associated with the interpolating nucleon fields and apply to local as well as smeared interpolators. The nucleon-pion-state contribution is found to be at the few percent level.
Structure functions in semihadronic tau decays
Energy Technology Data Exchange (ETDEWEB)
Colangelo, G. [Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati; Finkemeier, M. [Harvard Univ., Cambridge, MA (United States). Lyman Lab. of Physics; Mirkes, E. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Theoretische Teilchenphysik; Urech, R. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Theoretische Teilchenphysik
1997-05-01
We review a variety of topics related to hadronic structure functions in exclusive semihadronic tau decays. We introduce the concept of structure functions and summarize the most important concepts. We then calculate the decay {tau}{yields}3{pi}{nu}{sub {tau}} for very small hadronic invariant mass to one loop in chiral perturbation theory. New interesting features emerge with respect to the known results at tree level, in particular for the structure functions w{sub D} and w{sub E}. We discuss the prospects for experimental verification of our predictions. Finally, we discuss various issues at higher Q{sup 2}, related to hadronic resonance physics. Here we consider 2{pi}, {pi}K, 3{pi}, K{pi}K and {pi}K{pi} hadronic final states. (orig.).
The triton with long-range chiral N3LO three nucleon forces
Skibinski, R; Topolnicki, K; Witala, H; Epelbaum, E; Gloeckle, W; Krebs, H; Nogga, A; Kamada, H
2011-01-01
Long-range contributions to the three-nucleon force that have been recently worked out in chiral effective field theory at next-to-next-to-next-to-leading order are for the first time included in the triton and the doublet nucleon-deuteron scattering length calculations. The strengths of the two short-range terms available at this order in the chiral expansion are determined from the triton binding energy and the neutron-deuteron doublet scattering length. The structure of the resulting three-nucleon force is explored and effects for the two-nucleon correlation function in the triton are investigated. Expectation values of the individual contributions to the three-nucleon force in the triton are found to be in the range from a few 100 keV to about 1 MeV. Our study demonstrates that the very complicated operator structure of the novel chiral three-nucleon forces can be successively implemented in three-nucleon Faddeev calculations.
Vortex structure and characterization of quasiperiodic functions
International Nuclear Information System (INIS)
Quasiperiodic functions (QPFs) are characterized by their full vortex structure in one unit cell. This characterization is much finer and more sensitive than the topological one given by the total vorticity per unit cell (the 'Chern index'). It is shown that QPFs with an arbitrarily prescribed vortex structure exist by constructing explicitly such a 'standard' QPF. Two QPFs with the same vortex structure are equivalent, in the sense that their ratio is a function which is strictly periodic, nonvanishing and at least continuous. A general QPF can then be approximately reconstructed from its vortex structure on the basis of the standard QPF and the equivalence concept. As another application of this concept, a simple method is proposed for calculating the quasiperiodic eigenvectors of periodic matrices. Possible applications to the quantum-chaos problem on a phase-space torus are briefly discussed
Structure Functions of Unstable Lithium Isotopes
Saito, K; Ueda, M.; Tsushima, K.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
2001-01-01
We study both the spin-average and spin-dependent structure functions of the lithium isotopes, $^{6-11}$Li, which could be measured at RIKEN and other nuclear facilities in the future. It is found that the light-cone momentum distribution of the valence neutron in the halo of $^{11}$Li is very sharp and symmetric around y = 1, because of the weak binding. The EMC ratios for Li isotopes are then calculated. We study the possibility of extracting the neutron structure function...
Coherence effects in deuteron spin structure functions
Energy Technology Data Exchange (ETDEWEB)
Edelmann, J.; Piller, G.; Weise, W. [Physik Department, Institut fuer Theoretische Physik, Technische Universitaet Muenchen, Garching (Germany)
1998-05-01
We investigate coherence effects in the deuteron spin structure functions g{sub 1}{sup d} and b{sub 1}. In the kinematic domain of current fixed target experiments we observe that shadowing effects in g{sub 1}{sup d} are approximately twice as large as for the unpolarized structure function F{sub 2}{sup d}. Furthermore, we find that b{sub 1} is large at x<0.1 and receives dominant contributions from coherent double scattering. (author) 13 refs, 2 figs
Future Diffractive Structure Function Measurements at HERA
Mehta, A; Waugh, B
1996-01-01
The purposes and possibilities of future diffractive structure function measurements at HERA are presented. A review of the current range and accuracy of the measurement of $F_2^{D(3)}(\\beta, \\xpom, Q^2)$ is presented and an estimate of the precision of future measurements is given. A feasibility study is performed on the measurement of the structure functions $F_2^{D(4)}(\\beta, \\xpom, Q^2, t)$, $F_{2 charm}^{D}$, $R^{D(3)}$, $R^{D(4)}$ and $F_L^{\\pom}$. Included in this study are estimates of the integrated luminosity required, the analysis techniques to be employed and values of systematic error that could be expected.
Anomalous evolution of nonsinglet structure functions
International Nuclear Information System (INIS)
We review a formalism that includes the effects of nonperturbative U(1) symmetry breaking on the QCD evolution of nonsinglet structure functions. We show that a strong scale dependence is generated in an intermediate energy range 0.522 for all values of x. We show that this explains naturally the observed violation of the Gottfried sum, and allows a determination of the shape of the nonsinglet structure function, in excellent agreement with experiment. We argue that these effects may affect the determination of ?s, from deep-inelastic scattering. ((orig.))
Nucleon-nucleon theory and phenomenology
International Nuclear Information System (INIS)
This project involves five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the ?N and ?? physical regions of the N anti N ? ?? amplitude (with significantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 MeV and the new data near 55 MeV that have never been analyzed properly; (4) the introduction of a K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated permanent nucleon-nucleon data bank in the 0-1200 MeV range that can be used by all nucleon-nucleon reseachers
QCD structure of W boson and electron structure function
Energy Technology Data Exchange (ETDEWEB)
Slominski, W.; Szwed, J. [Institute of Computer Science, Jagiellonian University, Cracow (Poland)
1997-06-01
The QCD structure of the W boson is constructed and compared with that of the photon. A new concept of the electron structure function is also defined. The leading order splitting functions of electron into quarks are extracted, showing an important contribution from {gamma}-Z interference. Leading logarithmic QCD evolution equations are constructed and solved in the asymptotic region where log{sup 2} behaviour of the parton densities is observed. Possible applications with clear manifestation of ``resolved`` photon and weak bosons are discussed. (author) 9 refs, 6 figs
Novel Structure and Function of Typhoid Toxin
... Forms Working Inner Ear Cells July 29, 2013 Novel Structure and Function of Typhoid Toxin Researchers gained ... and CdtB, along with 5 PltB molecules. This novel organization, known as A2B5, forms a pyramid-shaped ...
Structure Function Studies for Turbulent Interstellar Medium
Han, X H S J L
2004-01-01
We study structure functions of rotation measures in the Canadian Galactic Plane Survey (CGPS) region and the North Galactic Pole (NGP) to extract the interstellar medium (ISM) fluctuation information. The CGPS data are divided into three longitude intervals: $82^\\circ1^\\circ$. The power law indices get smaller from CGPS1 to CGPS3 and the amplitudes decrease. The variations of the large-scale field and the electron density have only negligible effects on the structure function and thus cannot account for the changes, indicating that the turbulent properties of the Galactic ISM are intrinsically longitude-dependent. The Kolmogorov-like fluctuation spectrum of the electron density or the magnetic field should produce a power law structure function with an index of 5/3 or 2/3, neither of which is consistent with our results of small indices in the three sub-CGPS regions. For the NGP region, the structure function is flat, showing that the rotation measures are mostly intrinsic to the extragalactic sources, and t...
Levon, A I
2011-01-01
Conflicting coupling of unpaired nucleons in the odd-odd nuclei is discussed. A very simple explanation is suggested for the damping of the energy spacing of the lowest levels in the rotational bands in the odd-odd nuclei in the case of a "conflicting" coupling of the odd proton and neutron comparative to those of the bands based on the state of the strongly-coupled particle in the neighbouring odd nuclei entering the "conflicting" configuration.
Generalized functions, convergence structures, and their applications
Pap, Endre; Pilipovi?, Stevan; Vladimirov, Vasilij; International Conference "Generalized functions, convergence structures and their applications" (GFCA-87)
1988-01-01
This Proceedings consists of a collection of papers presented at the International Conference "Generalized functions, convergence structures and their applications" held from June 23-27, 1987 in Dubrovnik, Yugoslavia (GFCA-87): 71 participants from 21 countr~es from allover the world took part in the Conference. Proceedings reflects the work of the Conference. Plenary lectures of J. Burzyk, J. F. Colombeau, W. Gahler, H. Keiter, H. Komatsu, B. Stankovic, H. G. Tillman, V. S. Vladimirov provide an up-to-date account of the cur rent state of the subject. All these lectures, except H. G. Tillman's, are published in this volume. The published communications give the contemporary problems and achievements in the theory of generalized functions, in the theory of convergence structures and in their applications, specially in the theory of partial differential equations and in the mathematical physics. New approaches to the theory of generalized functions are presented, moti vated by concrete problems of applicat...
Hupin, Guillaume; Navrtil, Petr
2014-01-01
Prototype for the study of weakly bound projectiles colliding on stable targets, the scattering of deuterium ($d$) on $^4$He ($\\alpha$) is an important milestone in the search for a fundamental understanding of low-energy reactions. At the same time, it is also important for its role in the Big-bang nucleosynthesis of $^6$Li and applications in the characterization of deuterium impurities in materials. We present the first unified {\\em ab initio} study of the $^6$Li ground state and $d$-$^4$He elastic scattering using two- and three-nucleon forces derived within the framework of chiral effective field theory. The six-nucleon bound-state and scattering observables are calculated by means of the no-core shell model with continuum. %and are compared to available experimental data. We analyze the influence of the dynamic polarization of the deuterium and of the chiral three-nucleon force, and examine the role of the continuum degrees of freedom in shaping the low-lying spectrum of $^6$Li. We find that the adopted...
The extraction of the spin structure function, g2 (and g1) at low Bjorken x
Energy Technology Data Exchange (ETDEWEB)
Ndukum, Luwani Z. [Mississippi State University
2015-08-01
The Spin Asymmetries of the Nucleon Experiment (SANE) used the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory in Newport News, VA to investigate the spin structure of the proton. The experiment measured inclusive double polarization electron asymmetries using a polarized electron beam, scattered off a solid polarized ammonia target with target polarization aligned longitudinal and near transverse to the electron beam, allowing the extraction of the spin asymmetries A1 and A2, and spin structure functions g1 and g2. Polarized electrons of energies of 4.7 and 5.9 GeV were used. The scattered electrons were detected by a novel, non-magnetic array of detectors observing a four-momentum transfer range of 2.5 to 6.5 GeV*V. This document addresses the extraction of the spin asymmetries and spin structure functions, with a focus on spin structure function, g2 (and g1) at low Bjorken x. The spin structure functions were measured as a function of x and W in four Q square bins. A full understanding of the low x region is necessary to get clean results for SANE and extend our understanding of the kinematic region at low x.
The spin dependent structure function g1 of the deuteron and the proton
International Nuclear Information System (INIS)
This thesis presents a study on the spin structure of the nucleon, via deep inelastic scattering (DIS) of polarised nuons on polarised proton and deuterium targets. The work was done in the Spin Muon Collaboration (SMC) at CERN in Geneva. From the asymmetry in the scattering cross section for nucleon and lepton spins parallel and anti-parallel, one con determine the spin dependent structure function g1, which contains information on the quark and gluon spin distribution functions. The interpretation in the frame work of the quark parton model (QPM) of earlier results on g1p by the European Muon Collaboration (EMC), gave an indication that only a small fraction of the proton spin, compatible with zero, is carried by the spins of the constituent quarks. The SMC was set up to check this unexpected result with improved accuracy, and to combine measurements of g1p and g1d to test a fundamental sum rule in quantum chromodynamics (QCD), the Bjorken sum rule. (orig./WL)
The spin dependent structure function g{sub 1} of the deuteron and the proton
Energy Technology Data Exchange (ETDEWEB)
Klostermann, L.
1995-02-27
This thesis presents a study on the spin structure of the nucleon, via deep inelastic scattering (DIS) of polarised nuons on polarised proton and deuterium targets. The work was done in the Spin Muon Collaboration (SMC) at CERN in Geneva. From the asymmetry in the scattering cross section for nucleon and lepton spins parallel and anti-parallel, one con determine the spin dependent structure function g{sub 1}, which contains information on the quark and gluon spin distribution functions. The interpretation in the frame work of the quark parton model (QPM) of earlier results on g{sub 1}{sup p} by the European Muon Collaboration (EMC), gave an indication that only a small fraction of the proton spin, compatible with zero, is carried by the spins of the constituent quarks. The SMC was set up to check this unexpected result with improved accuracy, and to combine measurements of g{sub 1}{sup p} and g{sub 1}{sup d} to test a fundamental sum rule in quantum chromodynamics (QCD), the Bjorken sum rule. (orig./WL).
International Nuclear Information System (INIS)
The structure of the neutron rich light nuclei 11Be and 10Li has been investigated by means of one nucleon transfer reactions. The experiments have been carried out at GANIL in inverse kinematics using 11Be secondary beams. The 11Be(p,d)10Be reaction bas been studied at 35.3 MeV/u. The 10Be ejectiles were analyzed by the spectrometer SPEG, and coincident deuterons were detected in the position sensitive silicon detector CHARISSA. Transfer cross sections to 0+1 and 2+1, states in 10Be were measured up to ?CM = 16 deg. and compared to DWBA and CRC predictions. The effects of neutron-cure couplings on reaction form factors have been studied by solving coupled equations in the framework of a vibrational model. It is shown that the rate of core excitation 10Be2+ in the 11Begs wave function is overestimated by a standard analysis with form factors given by the usual Separation Energy prescription. The former model predicts a rate of core excitation of 16% and leads to theoretical cross sections which are in good agreement with the experimental data. The aim of the 11Be(d,3He)10Li experiment, realized at 37 MeV/u, was to measure the distribution of the 2s neutron strength in the unbound nucleus 10Li. The energy spectrum was deduced from the 3He energy and angle measured by the silicon strip detector array MUST. An asymmetric peak is clearly observed near the threshold, with a maximum at -Sn = 130 keV. This constitutes a direct proof of the inversion of 2s and 1p1/2 shells in 10Li, which was until now a controversial question in spite of many experimental efforts. On the other band the analysis of the 11Be(d,t)10Be reaction studied in the same experiment confirms the results obtained in the 11Be(p,d)10Be reaction concerning the 11Begs structure. This work shows the interest and feasibility of studies of the shell properties of exotic nuclei using transfer reactions induced by radioactive beams and constitutes the beginning of a program devoted to this kind of experiment. (author)
Nucleon momentum and density distributions of nuclei
International Nuclear Information System (INIS)
In the framework of recently suggested density coherent fluctuations model the nucleon momentum and density distributions are examined. Nucleon momentum and density distributions are expressed in terms of the fluctuation's function, experimentally obtainable from the elastic electron-nuclei scattering. (author)
On the electromagnetic polarisabilities of the nucleon
International Nuclear Information System (INIS)
The dynamic electric and magnetic polarisabilities of the nucleon are calculated taking the photon-nucleon resonance vertex-function ambiguity parameters into account. The annihilation channel in the Compton scattering amplitude is also evaluated from the chiral effective Lagrangian. It is found that the electric and magnetic polarisabilities of the proton are of the same order of magnitude. (author)
The Role of Strange and Charm Quarks in the Nucleon Spin Structure Function
Steffens, F. M.; Thomas, A.W.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, The University of Adelaide, Australia)
1995-01-01
We perform an analysis of the relation between the factorization scale and the masses of the quarks in the calculation of the hard gluon coefficient in polarized deep inelastic scattering. Particular attention is paid to the role of strange and charm quarks at finite momentum transfer. It is found that for the momentum transfer of the present experiments, the contribution from the charm quark is significant.
Using Drell-Yan Processes to Probe Nucleon and Meson Structure Functions
Bhalerao, R. S.; Londergan, J. T.
1997-01-01
We investigate how Drell-Yan processes can be used to measure the magnitude of flavor symmetry violation in the proton sea. We examine the utility of the following beams: protons, charged pions, and charged kaons. In each case we present an approximate expression for the Drell-Yan asymmetry. Using currently available parton distributions, we locate those kinematic regions which provide the greatest information on the quantity $\\bar{d}^p(x) - \\bar{u}^p(x)$. If sufficiently in...
K(+) channels: function-structural overview.
Gonzlez, Carlos; Baez-Nieto, David; Valencia, Ignacio; Oyarzn, Ingrid; Rojas, Patricio; Naranjo, David; Latorre, Ramn
2012-07-01
Potassium channels are particularly important in determining the shape and duration of the action potential, controlling the membrane potential, modulating hormone secretion, epithelial function and, in the case of those K(+) channels activated by Ca(2+), damping excitatory signals. The multiplicity of roles played by K(+) channels is only possible to their mammoth diversity that includes at present 70 K(+) channels encoding genes in mammals. Today, thanks to the use of cloning, mutagenesis, and the more recent structural studies using x-ray crystallography, we are in a unique position to understand the origins of the enormous diversity of this superfamily of ion channels, the roles they play in different cell types, and the relations that exist between structure and function. With the exception of two-pore K(+) channels that are dimers, voltage-dependent K(+) channels are tetrameric assemblies and share an extremely well conserved pore region, in which the ion-selectivity filter resides. In the present overview, we discuss in the function, localization, and the relations between function and structure of the five different subfamilies of K(+) channels: (a) inward rectifiers, Kir; (b) four transmembrane segments-2 pores, K2P; (c) voltage-gated, Kv; (d) the Slo family; and (e) Ca(2+)-activated SK family, SKCa. PMID:23723034
Spectral Density Functionals for Electronic Structure Calculations
Savrasov, S Y
2003-01-01
We introduce a spectral density functional theory which can be used to compute energetics and spectra of real strongly--correlated materials using methods, algorithms and computer programs of the electronic structure theory of solids. The approach considers the total free energy of a system as a functional of a local electronic Green function which is probed in the region of interest. Since we have a variety of notions of locality in our formulation, our method is manifestly basis--set dependent. However, it produces the exact total energy and local excitational spectrum provided that the exact functional is extremized. The self--energy of the theory appears as an auxiliary mass operator similar to the introduction of the ground--state Kohn--Sham potential in density functional theory. It is automatically short--ranged in the same region of Hilbert space which defines the local Green function. We exploit this property to find good approximations to the functional. For example, if electronic self--energy is kn...
Structure of BRS-invariant local functionals
International Nuclear Information System (INIS)
For a large class of gauge theories a nilpotent BRS-operator s is constructed and its cohomology in the space of local functionals of the off-shell fields is shown to be isomorphic to the cohomology of s=s+d on functions f(C,T) of tensor fields T and of variables C which are constructed of the ghosts and the connection forms. The result allows general statements about the structure of invariant classical actions and anomaly cadidates whose BRS-variation vanishes off-shell. The assumptions under which the result holds are thoroughly discussed. (orig.)
Structure of BRS-invariant local functionals
Brandt, F
1993-01-01
For a large class of gauge theories a nilpotent BRS-operator $s$ is constructed and its cohomology in the space of local functionals of the off-shell fields is shown to be isomorphic to the cohomology of $\\4s=s+d$ on functions $f(\\4C,\\PH)$ of tensor fields $\\PH$ and of variables $\\4C$ which are constructed of the ghosts and the connection forms. The result allows general statements about the structure of invariant classical actions and anomaly candidates whose BRS-variation vanishes off-shell. The assumptions under which the result holds are thoroughly discussed.
Proteins with Novel Structure, Function and Dynamics
Pohorille, Andrew
2014-01-01
Recently, a small enzyme that ligates two RNA fragments with the rate of 10(exp 6) above background was evolved in vitro (Seelig and Szostak, Nature 448:828-831, 2007). This enzyme does not resemble any contemporary protein (Chao et al., Nature Chem. Biol. 9:81-83, 2013). It consists of a dynamic, catalytic loop, a small, rigid core containing two zinc ions coordinated by neighboring amino acids, and two highly flexible tails that might be unimportant for protein function. In contrast to other proteins, this enzyme does not contain ordered secondary structure elements, such as alpha-helix or beta-sheet. The loop is kept together by just two interactions of a charged residue and a histidine with a zinc ion, which they coordinate on the opposite side of the loop. Such structure appears to be very fragile. Surprisingly, computer simulations indicate otherwise. As the coordinating, charged residue is mutated to alanine, another, nearby charged residue takes its place, thus keeping the structure nearly intact. If this residue is also substituted by alanine a salt bridge involving two other, charged residues on the opposite sides of the loop keeps the loop in place. These adjustments are facilitated by high flexibility of the protein. Computational predictions have been confirmed experimentally, as both mutants retain full activity and overall structure. These results challenge our notions about what is required for protein activity and about the relationship between protein dynamics, stability and robustness. We hypothesize that small, highly dynamic proteins could be both active and fault tolerant in ways that many other proteins are not, i.e. they can adjust to retain their structure and activity even if subjected to mutations in structurally critical regions. This opens the doors for designing proteins with novel functions, structures and dynamics that have not been yet considered.
Geometrical scaling in charm structure function ratios
International Nuclear Information System (INIS)
By using a Laplace-transform technique, we solve the next-to-leading-order master equation for charm production and derive a compact formula for the ratio Rc=FLcc/F2cc, which is useful for extracting the charm structure function from the reduced charm cross section, in particular, at DESY HERA, at small x. Our results show that this ratio is independent of x at small x. In this method of determining the ratios, we apply geometrical scaling in charm production in deep inelastic scattering (DIS). Our analysis shows that the renormalization scales have a sizable impact on the ratio Rc at high Q2. Our results for the ratio of the charm structure functions are in a good agreement with some phenomenological models
Phosphatidylinositol 4-kinases: Function, structure, and inhibition.
Boura, Evzen; Nencka, Radim
2015-10-01
The phosphatidylinositol 4-kinases (PI4Ks) synthesize phosphatidylinositol 4-phosphate (PI4P), a key member of the phosphoinositide family. PI4P defines the membranes of Golgi and trans-Golgi network (TGN) and regulates trafficking to and from the Golgi. Humans have two type II PI4Ks (? and ?) and two type III enzymes (? and ?). Recently, the crystal structures were solved for both type II and type III kinase revealing atomic details of their function. Importantly, the type III PI4Ks are hijacked by +RNA viruses to create so-called membranous web, an extensively phosphorylated and modified membrane system dedicated to their replication. Therefore, selective and potent inhibitors of PI4Ks have been developed as potential antiviral agents. Here we focus on the structure and function of PI4Ks and their potential in human medicine. PMID:26183104
Red cell antigens: Structure and function
Directory of Open Access Journals (Sweden)
Pourazar Abbasali
2007-01-01
Full Text Available Landsteiner and his colleagues demonstrated that human beings could be classified into four groups depending on the presence of one (A or another (B or both (AB or none (O of the antigens on their red cells. The number of the blood group antigens up to 1984 was 410. In the next 20 years, there were 16 systems with 144 antigens and quite a collection of antigens waiting to be assigned to systems, pending the discovery of new information about their relationship to the established systems. The importance of most blood group antigens had been recognized by immunological complications of blood transfusion or pregnancies; their molecular structure and function however remained undefined for many decades. Recent advances in molecular genetics and cellular biochemistry resulted in an abundance of new information in this field of research. In this review, we try to give some examples of advances made in the field of ?structure and function of the red cell surface molecules.?
Dynamic versus Static Hadronic Structure Functions
International Nuclear Information System (INIS)
'Static' structure functions are the probabilistic distributions computed from the square of the light-front wavefunctions of the target hadron. In contrast, the 'dynamic' structure functions measured in deep inelastic lepton-hadron scattering include the effects of rescattering associated with the Wilson line. Initial- and final-state rescattering, neglected in the parton model, can have a profound effect in QCD hard-scattering reactions, producing single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam-Tung relation in Drell-Yan reactions, nuclear shadowing, and non-universal nuclear antishadowing-novel leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also review how 'direct' higher-twist processes - where a proton is produced in the hard subprocess itself - can explain the anomalous proton-to-pion ratio seen in high centrality heavy ion collisions.
An NIIR structure using HL CPWL functions
Scientific Electronic Library Online (English)
L. R., Castro; J. L., Figueroa; O. E., Agamennoni.
2005-04-01
Full Text Available In this paper we present a nonlinear infinite impulse response (NIIR) model structure for black-box identification of nonlinear dynamic systems. The proposed model structure allows the implementation of an identification algorithm in which the degrees of freedom of the Nonlinear Output Error (NOE) m [...] odel can be easily increased or decreased during the identification process. This property is very attractive to find the appropriate NIIR model, avoiding overfitting. This is done using High Level Canonical Piecewise Linear (HL CPWL) functions with an increasing (decreasing) grid division. Therefore, the algorithm may start using a linear estimation of the model. The parameters of the HL CPWL functions are updated using a simple algorithm based on a modified steepest descent method with an independently adaptive learning rate.
Influenza Virus Neuraminidase: Structure and Function
Shtyrya, Y.A.; Mochalova, L.V.; Bovin, N. V.
2009-01-01
The structure of the influenza virus neuraminidases, the spatial organization of their active site, the mechanism of carbohydrate chains desialylation by neuraminidase, and its role in the influenza virus function at different stages of the viral infectious cycle are considered in this review. Data on the neuraminidase substrate specificity and different approaches in studying the activity of this enzyme are summarized. In addition, data on neuraminidase inhibitors (as antivirals) are provide...
Theoretical analysis of polarized structure functions
Energy Technology Data Exchange (ETDEWEB)
Altarelli, G. [CERN Theoretical Physics Division, Geneva (European Organization for Nuclear Research (CERN)); Ball, R.D. [Department of Physics and Astronomy, University of Edinburgh, Edinburgh (United Kingdom); Forte, S. [INFN, Sezione di Torino, Torino (Italy); Ridolfi, G. [INFN, Sezione di Genova, Genova (Italy)
1998-05-01
We review the analysis of polarized structure function data using perturbative QCD and NLO We use the most recent experimental data to obtain updated results for polarized parton distributions, first moments and the strong coupling. We also discuss several theoretical issues involving in this analysis and in the interpretation of its results. Finally, we compare our results with other similar analyses in the recent literature. (author) 67 refs, 5 figs, 3 tabs
On the structure function of photon
International Nuclear Information System (INIS)
A general solution of the modified Altarelli-Parisi equations in moment representation satisfied by the parton distributions of photon, including a general form of Born term, is obtained by using the variation coefficient procedure. The result shows that it is necessary to apply the general solution to find the x- and Q2-dependence of photon structure function, especially for experimentally relevant Q2 values. (author). 9 refs., 1 tab., 3 figs
Structure and function of mammalian cilia
Satir, Peter; CHRISTENSEN, SREN T.
2008-01-01
In the past half century, beginning with electron microscopic studies of 9+2 motile and 9+0 primary cilia, novel insights have been obtained regarding the structure and function of mammalian cilia. All cilia can now be viewed as sensory cellular antennae that coordinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation. This view has had unanticipated consequences for our understanding ...
Mutational effects on protein structure and function
Carlsson, Jonas
2009-01-01
In this thesis several important proteins are investigated from a structural perspective. Some of the proteins are disease related while other have important but not completely characterised functions. The techniques used are general as demonstrated by applications on metabolic proteins (CYP21, CYP11B1, IAPP, ADH3), regulatory proteins (p53, GDNF) and a transporter protein (ANTR1). When the protein CYP21 (steroid 21-hydroxylase) is deficient it causes CAH (congenital adrenal hyperplasia). For...
International Nuclear Information System (INIS)
High energy electro-excitation cross sections on 6Li and 12C in the region of the first nucleon resonance are compared with calculations in the impulse approximation. It is shown that the 6Li and 12C cross sections can be reproduced by an incoherent superposition of nucleon structure functions for 0.2 2 2 and primary energies in the GeV range. (orig.)
Nucleon pair approximation description of the low-lying structure of $^{108,109}$Te and $^{109}$I
Jiang, H; Lei, Y; Liotta, R; Wyss, R; Zhao, Y M
2013-01-01
The low-lying level schemes and electromagnetic transitions of $^{109}$Te, $^{109}$I, and the neighboring even-even nucleus $^{108}$Te, are calculated within the framework of the $SD$-pair approximation of the nuclear shell model. Good agreement is obtained between the calculated results and experimental data. The favored components of low-lying bands are discussed in the collective nucleon-pair subspace. The weak-coupling picture shown in these nuclei and its relationship with residual quadrupole-quadrupole interaction between valence protons and neutrons are analyzed.
Structural and regulatory functions of keratins
International Nuclear Information System (INIS)
The diversity of epithelial functions is reflected by the expression of distinct keratin pairs that are responsible to protect epithelial cells against mechanical stress and to act as signaling platforms. The keratin cytoskeleton integrates these functions by forming a supracellular scaffold that connects at desmosomal cell-cell adhesions. Multiple human diseases and murine knockouts in which the integrity of this system is destroyed testify to its importance as a mechanical stabilizer in certain epithelia. Yet, surprisingly little is known about the precise mechanisms responsible for assembly and disease pathology. In addition to these structural aspects of keratin function, experimental evidence accumulating in recent years has led to a much more complex view of the keratin cytoskeleton. Distinct keratins emerge as highly dynamic scaffolds in different settings and contribute to cell size determination, translation control, proliferation, cell type-specific organelle transport, malignant transformation and various stress responses. All of these properties are controlled by highly complex patterns of phosphorylation and molecular associations
Structural and functional neuroimaging in intractable epilepsy
Directory of Open Access Journals (Sweden)
Chinchure Swati
2010-01-01
Full Text Available Medical management remains unsatisfactory in about a third of patients with epilepsy and some of them are candidates for resective epilepsy surgery. Structural and functional neuroimaging plays an important role in the identification of the precise cortical region responsible for seizures and is very crucial for a good surgical outcome. Furthermore, identification of eloquent cortical areas near the region to be resected is essential to avoid postoperative neurologic deficit. The magnetic resonance imaging (MRI protocol for epilepsy can be individually tailored depending on the seizure semiology and possibly electroencephalography. New MRI techniques demonstrate the structure of the brain in fine detail, help in understanding the underlying pathology, and demonstrate functional activity of the brain with high spatial and temporal resolution. Metabolic imaging techniques, such as positron emission tomography (PET and single photon emission tomography (SPECT visualize metabolic alterations of the brain in the ictal and interictal states. In MR-negative epilepsy patients, these techniques may have localizing value. The proper use and interpretation of the findings provided by these new technologies is crucial. In this review article, we discuss various conventional and advanced MRI techniques, interpretation of various findings, and the role of functional imaging modalities, such as functional MRI, PET, and SPECT in the localization of epileptogenic substrate as well as for understanding the pathophysiology, propagation, and neurochemical correlates of epilepsy.
The ratio of structure functions for the neutron and the proton
International Nuclear Information System (INIS)
The subject of this thesis is the ratio of the structure functions F2 of the deuteron and the proton. The structure function ratio is measured by the NMC with high precision due to a dedicated target setup. In this thesis the analysis is presented of the data taken in 1989, which were obtained using incident muon energies of 120, 200 and 280 GeV. These data complement the results from earlier measurements performed in 1986 and 1987 which were obtained at 90 and 280 GeV incident muon energy. The newly determined structure function ratio, in a slightly extended range of the scaling parameter x, is compared to the previous one and is found to be in good agreement. All data are combined to give the most accurate determination of the structure function ratio to date. The results are used to determine the dependence of the structure function ratio on the value of Q2, the scale at which the nucleon is probed. Finally, the structure function ratios obtained at four different incident muon energies separately, are used to determine the difference Rd-Rp, where R is the ratio of cross sections for the absorption of longitudinally and transversely polarized virtual photons. The difference in R for the deuteron and the proton is related to differences in the gluon distribution. The result is compatible with a gluon distribution that is identical for the deuteron and the proton. The degree of equality of Rd and Rp is a measure for the correctness of the procedure to extract structure function ratios. The present result is Rd-Rp=0.020.02 and hence compatible with zero. (orig.)
Spin Asymmetries of the Nucleon Experiment
Armstrong, Whitney; SANE Collaboration
2014-09-01
The Spin Asymmetries of the Nucleon Experiment (SANE) measured the proton spin structure function g2 in a range of Bjorken x, 0 . 3 twist-3 matrix element, d2p, is most sensitive. The data were taken from Q2 = 2 . 5 GeV2 up to 6 . 5 GeV2 . Using a polarized proton target and polarized electron beam, two double spin asymmetries, A? and A?, were measured at Jefferson Lab's Hall-C with the BETA (Big Electron Telescope Array) detector. BETA consists of a scintillator hodoscope, gas Cherenkov, lucite hodoscope and a large array of lead glass detectors. With a unique open geometry, a threshold gas Cherenkov detector allowed BETA to cleanly identify electrons for this inclusive experiment. In addition to presenting the latest results from SANE on the spin structure functions and virtual Compton scattering asymmetries, I will discuss the physics impact and extraction of the matrix element d2p.
The isospin structure of photoproduction of pi-eta pairs from the nucleon in the threshold region
Kser, A; Annand, J R M; Arends, H J; Bantawa, K; Bartolome, P A; Beck, R; Bekrenev, V; Berghuser, H; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Costanza, S; Demissie, B; Dieterle, M; Downie, E J; Drexler, P; Fil'kov, L V; Fix, A; Glazier, D I; Hamilton, D; Heid, E; Hornidge, D; Howdle, D; Huber, G M; Jahn, O; Jaegle, I; Jude, T C; Kashevarov, V L; Keshelashvili, I; Kondratiev, R; Korolija, M; Kruglov, S P; Krusche, B; Lisin, V; Livingston, K; MacGregor, I J D; Maghrbi, Y; Mancell, J; Manley, D M; Marinides, Z; McGeorge, J C; McNicoll, E; Mekterovic, D; Metag, V; Micanovic, S; Middleton, D G; Mushkarenkov, A; Nikolaev, A; Novotny, R; Oberle, M; Ostrick, M; Otte, P; Oussena, B; Pedroni, P; Pheron, F; Polonski, A; Prakhov, S N; Robinson, J; Rosner, G; Rostomyan, T; Schumann, S; Sikora, M H; Sober, D I; Starostin, A; Supek, I; Thiel, M; Thomas, A; Unverzagt, M; Watts, D P; Werthmller, D; Witthauer, L
2015-01-01
Photoproduction of $\\pi\\eta$-pairs from nucleons has been investigated from threshold up to incident photon energies of $\\approx$~1.4~GeV. The quasi-free reactions $\\gamma p\\rightarrow p\\pi^0\\eta$, $\\gamma n\\rightarrow n\\pi^0\\eta$, $\\gamma p\\rightarrow n\\pi^+\\eta$, and $\\gamma n\\rightarrow p\\pi^-\\eta$ were for the first time measured from nucleons bound in the deuteron. The corresponding reactions from a free-proton target were also studied to investigate final-state interaction effects (for neutral pions the free-proton results could be compared to previous measurements; the $\\gamma p\\rightarrow n\\pi^+\\eta$ reaction was measured for the first time). For the $\\pi^0\\eta$ final state coherent production via the $\\gamma d\\rightarrow d\\pi^0\\eta$ reaction was also investigated. The experiments were performed at the tagged photon beam of the Mainz MAMI accelerator using an almost $4\\pi$ coverage electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. The total cross sections for the four differ...
Study of nucleon-nucleon and hyperon-nucleon interaction
Energy Technology Data Exchange (ETDEWEB)
Shimizu, Kiyotaka [Department of Physics, Sophia University, Tokyo (Japan); Takeuchi, Sachiko [Japan College of Social Work, Kiyose (Japan); Buchmann, A.J. [Institute for Theoretical Physics, University of Tuebinge (Germany)
2000-04-01
In this paper we review recent investigations of nucleon-nucleon and hyperon-nucleon interactions employing a non-relativistic quark cluster model. We concentrate mainly on the short and medium-range behavior of the baryon-baryon interaction based on the one-gluon and meson exchange potentials. The chiral quark model based on pion and sigma exchange between quarks is also discussed. We also review a study of the deuteron and its electromagnetic properties in a quark model with exchange currents. (author)
Muangma, I Korover N; Shneor, R; Sulkosky, V; Kelleher, A; Gilad, S; Higinbotham, D W; Watson, E Piasetzky J; Wood, S; Rakhman, Abdurahim; Aguilera, P; Ahmed, Z; Albataineh, H; Allada, K; Anderson, B; Anez, D; Aniol, K; Annand, J; Armstrong, W; Arrington, J; Averett, T; Badman, T; Baghdasaryan, H; Bai, X; Beck, A; Beck, S; Bellini, V; Benmokhtar, F; Bertozzi, W; Bittner, J; Boeglin, W; Camsonne, A; Chen, C; Chen, J -P; Chirapatpimol, K; Cisbani, E; Dalton, M; Daniel, A; Day, D; de Jager, C W; De Leo, R; Deconinck, W; Defurne, M; Flay, D; Fomin, N; Friend, M; Frullani, S; Fuchey, E; Garibaldi, F; Gaskell, D; Gilman, R; Glamazdin, O; Gu, C; Gueye, P; Hamilton, D; Hanretty, C; Hansen, O; Shabestari, M Hashemi; Holmstrom, T; Huang, M; Iqbal, S; Jin, G; Kalantarians, N; Kang, H; Khandaker, M; LeRose, J; Leckey, J; Lindgren, R; Long, E; Mammei, J; Margaziotis, D J; Markowitz, P; Jimenez-Arguello, A Marti; Meekins, D; Meziani, Z; Michaels, R; Mihovilovic, M; Monaghan, P; Camacho, C Munoz; Norum, B; Nuruzzaman,; Pan, K; Phillips, S; Pomerantz, I; Posik, M; Punjabi, V; Qian, X; Qiang, Y; Qiu, X; Reimer, P E; Riordan, S; Ron, G; Rondon-Aramayo, O; Saha, A; Schulte, E; Selvy, L; Shahinyan, A; Sirca, S; Sjoegren, J; Slifer, K; Solvignon, P; Sparveris, N; Subedi, R; Tireman, W; Wang, D; Weinstein, L B; Wojtsekhowski, B; Yan, W; Yaron, I; Ye, Z; Zhan, X; Zhang, J; Zhang, Y; Zhao, B; Zhao, Z; Zheng, X; Zhu, P; Zielinski, R
2014-01-01
We measured simultaneously the 4He(eep), 4He(eepp), and 4He(e,e'pn) reactions at Q^2=2 [GeV/c]2 and x_B>1, for a (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Neutron-proton pairs dominate the high-momentum tail of the nucleon momentum distributions, but their abundance is reduced as the nucleon momentum increases beyond ~500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum in the range we studied. Our data are compared with ab-initio calculations of two-nucleon momentum distributions in 4He.
Nuclear medium modification of the F{sub 2}(x,Q{sup 2}) structure function
Energy Technology Data Exchange (ETDEWEB)
Sajjad Athar, M., E-mail: sajathar@gmail.co [Department of Physics, Aligarh Muslim University, Aligarh 202 002 (India); Ruiz Simo, I.; Vicente Vacas, M.J. [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia - CSIC, 46100 Burjassot (Valencia) (Spain)
2011-05-01
We study the nuclear effects in the electromagnetic structure function F{sub 2}(x,Q{sup 2}) in the deep inelastic lepton-nucleus scattering process by taking into account Fermi motion, binding, pion and rho meson cloud contributions. Calculations have been done in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations. The ratios R{sub F}{sub 2}{sup A}(x,Q{sup 2})=(2F{sub 2}{sup A}(x,Q{sup 2}))/(AF{sub 2}{sup D}(x,Q{sup 2})) are obtained and compared with recent JLab results for light nuclei with special attention to the slope of the x distributions. This magnitude shows a non-trivial A dependence and it is insensitive to possible normalization uncertainties. The results have also been compared with some of the older experiments using intermediate mass nuclei.
Measurement of the Proton and Deuteron Spin Structure Function g1 in the Resonance Region
International Nuclear Information System (INIS)
We have measured the proton and deuteron spin structure functions g1p and g1d in the region of the nucleon resonances for W2 2 and Q2 ? 0.5 and Q2 ? 1.2 GeV2 by inelastically scattering 9.7 GeV polarized electrons off polarized 15NH3 and 15ND3 targets. We observe significant structure in g1p in the resonance region. We have used the present results, together with the deep-inelastic data at higher W2, to extract ?(Q2) (triplebond) ?01 g1(x,Q2) dx. This is the first information on the low-Q2 evolution of Gamma toward the Gerasimov-Drell-Hearn limit at Q2 = 0
The structure and function of presynaptic endosomes.
Jhne, Sebastian; Rizzoli, Silvio O; Helm, Martin S
2015-07-15
The function of endosomes and of endosome-like structures in the presynaptic compartment is still controversial. This is in part due to the absence of a consensus on definitions and markers for these compartments. Synaptic endosomes are sometimes seen as stable organelles, permanently present in the synapse. Alternatively, they are seen as short-lived intermediates in synaptic vesicle recycling, arising from the endocytosis of large vesicles from the plasma membrane, or from homotypic fusion of small vesicles. In addition, the potential function of the endosome is largely unknown in the synapse. Some groups have proposed that the endosome is involved in the sorting of synaptic vesicle proteins, albeit others have produced data that deny this possibility. In this review, we present the existing evidence for synaptic endosomes, we discuss their potential functions, and we highlight frequent technical pitfalls in the analysis of this elusive compartment. We also sketch a roadmap to definitely determine the role of synaptic endosomes for the synaptic vesicle cycle. Finally, we propose a common definition of synaptic endosome-like structures. PMID:25939282
Autotaxin: structure-function and signaling.
Perrakis, Anastassis; Moolenaar, Wouter H
2014-02-18
Autotaxin (ATX), or ecto-nucleotide pyrophosphatase/phosphodiesterase-2, is a secreted lysophospholipase D (lysoPLD) that hydrolyzes extracellular lysophospholipids into the lipid mediator lysophosphatidic acid (LPA), a ligand for specific G protein-coupled receptors. ATX-LPA signaling is essential for development and has been implicated in a great diversity of (patho)physiological processes, ranging from lymphocyte homing to tumor progression. Structural and functional studies have revealed what makes ATX a unique lysoPLD, and how secreted ATX binds to its target cells. The ATX catalytic domain shows a characteristic bimetallic active site followed by a shallow binding groove that can accommodate nucleotides as well as the glycerol moiety of lysophospholipids, and by a deep lipid-binding pocket. In addition, the catalytic domain has an open tunnel of unknown function adjacent to the active site. Here, we discuss our current understanding of ATX structure-function relationships and signaling mechanisms, and how ATX isoforms use distinct mechanisms to target LPA production to the plasma membrane, notably binding to integrins and heparan sulfate proteoglycans. We also briefly discuss the development of drug-like inhibitors of ATX. PMID:24548887
On hard pomeron enhancement of ultrahigh-energy neutrino-nucleon cross-sections
Berezinsky, Veniamin Sergeevich; Yanush, S I
2002-01-01
An unknown small-$x$ behavior of nucleon structure functions brings to appreciable uncertainties in high-energy neutrino-nucleon cross-sections. We show that Regge theory inspired description of $F_2^{ep}(x,Q^2)$ at small $x$ by \\emph{A. Donnachie and P. V. Landshoff}, comprising \\emph{'soft'} and \\emph{'hard'} pomeron terms, may be fairly combined with perturbative \\emph{QCD} parameterization at large $x$. We meet these descriptions over $\\log x$ at each $Q^2$ with help of simple polynomials, smooth interpolation being provided by an appropriate choice of interpolation zone boundaries. To express the low-$x$ neutrino-nucleon structure functions $F_{2}^{\
Measurement of Spin Structure Functions at Moderate Q2 Using CLAS
International Nuclear Information System (INIS)
Spin structure functions of the nucleon in the region of large z and small to moderate Q2 continue to be of high current interest. Among the topics one can study in this kinematic regime are spin-dependent resonance transition amplitudes and their interference with each other and the non-resonant background, the behavior of the asymmetry A1 at large x, and the presence or absence of local duality in spin structure functions. The first moment of the spin structure function g1 goes through a rapid transition from the photon point (Q2 = 0), where it is constrained by the Gerasimov-Drell-Hearn sum rule, to the deep inelastic limit where it is sensitive to the nucleon spin fraction carried by quarks. This opens up the possibility to study the transition from hadronic to quark degrees of freedom over the whole range of Q2. Recently, we concluded a large experimental program to measure these observables with polarized proton and deuteron targets at Jefferson Lab. A highly polarized electron beam, solid polarized NH3 and ND3 targets and the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B were used to accumulate over 23 billion events with 4 different beam energies of 1.6, 2.5, 4.2 and 5.7 GeV. We present an overview of the experiment, its kinematic coverage and its statistical power. We show final results from the first run at 2.5 GeV and 4 GeV and preliminary results from the 5.7 GeV and the 1.6 GeV data sets
Neutrino-pair bremsstrahlung from nucleon-nucleon scattering
Li, Yi; Liou, M. K.; Schreiber, W. M.; Gibson, B. F.
2015-07-01
Background: Neutrino-pair bremsstrahlung processes from nucleon-nucleon scattering N N ? ? (n n ? ? ,p p ? ? , and n p ? ? ) have recently attracted attention in studies of neutrino emission in neutron stars, because of the implications for the neutron star cooling. The calculated N N ? ? emissivities within the neutron star environment are relatively insensitive to the two-nucleon dynamical model used in the calculations, but differ significantly from those obtained using an one-pion-exchange (OPE) model. Purpose: We investigate the free N N ? ? cross sections using a realistic nucleon-nucleon scattering amplitude, comparing the relative sizes of the cross sections for the three processes n n ? ? ,p p ? ? , and n p ? ? . Method: We employ a realistic one-boson-exchange (ROBE) model for N N scattering and combine those strong scattering amplitudes with the well-known nucleon weak interaction vertices to construct weak bremsstrahlung amplitudes. Using the resulting N N ? ? amplitudes we investigate the relative importance of the vector (?V?) , axial vector (?A?) , and tensor (?T?) terms. The ROBE model bremsstrahlung amplitudes are also used as a two-nucleon dynamical model with which we calculate the cross sections d/? d ? for n n ? ? ,p p ? ? , and n p ? ? . Results: The three free N N ? ? cross sections d/? d ? are of similar order of magnitude. Each increases with increasing neutrino-pair energy ? . For the neutrino-pair energy of ? =1 MeV our n n ? ? results are in quantitative agreement with those previously reported by Timmermans et al. [Phys. Rev. C 65, 064007 (2002), 10.1103/PhysRevC.65.064007], who used the leading-order term of the soft-neutrino-pair bremsstrahlung amplitude to calculate the cross sections. Differences between the n n ? ? and p p ? ? cross section are not discernible over the nucleon-nucleon incident energy region considered, due to the complete dominance of the axial vector component of the weak interaction nucleon vertex function ?? as demonstrated analytically in Appendix A. The n p ? ? cross section is smaller than either the n n ? ? or the p p ? ? cross section for low to moderate values of ? ; this characteristic only changes at larger neutrino-pair energies around ? 50 MeV , which is above the low energy region characterized in Appendix B. Conclusions: The free N N ? ? cross sections, calculated using a realistic nucleon-nucleon amplitude model, are new except for the n n ? ? cross section at ? =1 MeV that was first reported by Timmermans et al., and at ? =0.5 ,1 ,2 MeV by Li et al. [Phys. Rev. C 80, 035505 (2009), 10.1103/PhysRevC.80.035505]. The n n ? ? and p p ? ? cross sections are virtually identical in magnitude. All three N N ? ? processes are dominated by the axial vector component of the vertex function ??, with only slight deviations from this behavior being seen in the n p ? ? process at large neutrino-pair energies.
Study of the derivative expansions for the nuclear structure functions
Simo, I Ruiz
2008-01-01
We study the convergence of the series expansions sometimes used in the analysis of the nuclear effects in Deep Inelastic Scattering (DIS) proccesses induced by leptons. The recent advances in statistics and quality of the data, in particular for neutrinos calls for a good control of the theoretical uncertainties of the models used in the analysis. Using realistic nuclear spectral functions which include nucleon correlations, we find that the convergence of the derivative expansions to the full results is poor except at very low values of $x$.
The spin structure function of the neutron
Thomas, A W
2002-01-01
The neutron spin structure function, $g_{1n}$, has been of considerable interest recently in connection with the Bjorken sum rule and the proton spin crisis. Work on this problem has concentrated on measurements at low-$x$. We recall the important, non-perturbative physics to be learnt by going instead to larger values of $x$ and especially from a determination of the place where the expected sign change occurs. Of course, in order to obtain neutron data one must use nuclear targets and apply appropriate corrections. In this regard, we review recent progress concerning the various nuclear corrections that must be applied to measurements on polarised $^3$He.
Exclusive reactions and polarized structure functions
International Nuclear Information System (INIS)
The first properties studied are the counting rules which give the shape of the decreasing process cross-section. The calculation of the pion form factor implies a factorization between a non-perturbative term and a hard amplitude term controlled by a perturbative development. It is shown that these results can be generalized to any hard exclusive process. Other processes which violate the counting rules, such as Landshoff processes are analyzed in order to define a formalism. A quick account of experimental results about colour transparency is made. The last part of the work is dedicated to polarized structure functions and to the new concept of transversal spin. (A.C.)
Soft matter nanotechnology from structure to function
Chen, Xiaodong
2015-01-01
Using the well-honed tools of nanotechnology, this book presents breakthrough results in soft matter research, benefitting from the synergies between the chemistry, physics, biology, materials science, and engineering communities. The team of international authors delves beyond mere structure-making and places the emphasis firmly on imparting functionality to soft nanomaterials with a focus on devices and applications. Alongside reviewing the current level of knowledge, they also put forward novel ideas to foster research and development in such expanding fields as nanobiotechnology and nanom
Structure and Function of ABC Transporters
Kenneth Linton (Imperial College Hammersmith Hospital Campus)
2007-04-01
ATP binding cassette transporters are ubiquitous integral membrane proteins that actively transport ligands across biological membranes, a process critical for most aspects of cell physiology. These proteins are important clinically and economically. Their dysfunction underlies a number of human genetic diseases, and the ability of some to pump cytotoxic molecules from cells confers resistance to antibiotics, herbicides, and chemotherapeutic drugs. Recent structure analyses interpreted in light of a large body of biochemistry has resulted in the ATP-switch model for function in which the paired nucleotide binding domains switch between an ATP-dependent closed conformation and a nucleotide-free, open conformation to drive the translocation of ligand.
Structure functions at high Q2
International Nuclear Information System (INIS)
Progress in the study of structure functions in deep inelastic scattering is reviewed. A brief introduction to the formalism and the status of global analyses of parton distributions and their uncertainties is given. The review focuses on recent developments in the following areas: HERA results on F2,FL and charm; the resolution of the CCFR-NMC discrepancy; Tevatron jet cross-sections at different energies; and HERA high-Q2 cross-sections and the measurement of xF3
Energy Technology Data Exchange (ETDEWEB)
EN YO,H.; SAITO,N.; SHIBATA,T.A.; YAZAKI,K.; BUNCE,G.
2002-03-29
The RIKEN School on ''Quark-Gluon Structure of the Nucleon and QCD'' was held from March 29th through 31st at the Nishina Memorial Hall of RIKEN, Wako, Saitama, Japan, sponsored by RIKEN (the Institute of Physical and Chemical Research). The school was the second of a new series with a broad perspective of hadron and nuclear physics. The purpose of the school was to offer young researchers an opportunity to learn theoretical aspects of hadron physics based on QCD and related experimental programs being or to be carried out by Japanese groups. We had 3 theoretical courses, each consisting of 3 one-hour lectures, and 6 experimental courses, each consisting of a one-hour lecture.
Neutral-current x-distributions in the neutrino-nucleon scattering
International Nuclear Information System (INIS)
In this thesis the measurement of the x distribution of the structure functions for deep inelastic charged-current and neutral-current neutrino-nucleon interactions at the CERN 200 GeV narrow-band neutrino beam is described. (HSI)
External Momentum, Volume Effects, and the Nucleon Magnetic Moment
Tiburzi, B C
2007-01-01
We analyze the determination of volume effects for correlation functions that depend on an external momentum. As a specific example, we consider finite volume nucleon current correlators, and focus on the nucleon magnetic moment. Because the multipole decomposition relies on SO(3) rotational invariance, the structure of such finite volume corrections is unrelated to infinite volume multipole form factors. One can deduce volume corrections to the magnetic moment only when a zero-mode photon coupling vanishes, as occurs at next-to-leading order in heavy baryon chiral perturbation theory. To deduce such finite volume corrections, however, one must assume continuous momentum transfer. In practice, volume corrections with momentum transfer dependence are required to address the extraction of the magnetic moment, or other observables that arise in momentum dependent correlation functions. Additionally we shed some light on a puzzle concerning differences in lattice form factor data at equal values of momentum trans...
Azores Crustal Structure Derived From Receiver Functions
Silva, P.; Silveira, G.; Lourenco, N.; Stutzmann, E.; Miranda, M.
2003-12-01
During the last two decades efforts have been put together to understand the processes responsible for the Azores plateau formation. The geodynamics of this plateau, located at the triple junction between America, Africa and European plates, is dominated by the tectonics of the triple junction and by hotspot activity. But, the relationship between islands volcanism and a possible plume beneath the Azores is still not well understood and the triple junction exact location is also under debate. From October 2000 to September 2002, temporary broadband seismic stations have been deployed in the Azores archipelago in the framework of the COSEA Memoradum of Understanding. These broadband data have been used to compute receiver functions and estimate the crustal structure beneath the islands. Radial receiver functions where analyzed by both inverse and forward modeling in order to obtain 1-D S-wave profile. Crustal receiver functions exhibit local effects and the stations can be separated into 2 groups. Flores and Corvo islands, that are located at the west of the ridge axis and central islands (Faial and Pico) display slow crustal S-wave velocity whereas the eastern island of Santa Maria is associated with fast crustal S-wave velocity. These results will be discussed in the Azores geodynamic context.
Phototriggered functionalization of hierarchically structured polymer brushes.
de Los Santos Pereira, Andres; Kostina, Nina Yu; Bruns, Michael; Rodriguez-Emmenegger, Cesar; Barner-Kowollik, Christopher
2015-06-01
The precise design of bioactive surfaces, essential for the advancement of many biomedical applications, depends on achieving control of the surface architecture as well as on the ability to attach bioreceptors to antifouling surfaces. Herein, we report a facile avenue toward hierarchically structured antifouling polymer brushes of oligo(ethylene glycol) methacrylates via surface-initiated atom transfer radical polymerization (SI-ATRP) presenting photoactive tetrazole moieties, which permitted their functionalization via nitrile imine-mediated tetrazole-ene cyclocloaddition (NITEC). A maleimide-functional ATRP initiator was photoclicked to the side chains of a brush enabling a subsequent polymerization of carboxybetaine acrylamide to generate a micropatterned graft-on-graft polymer architecture as evidenced by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Furthermore, the spatially resolved biofunctionalization of the tetrazole-presenting brushes was accessed by the photoligation of biotin-maleimide and subsequent binding of streptavidin. The functionalized brushes bearing streptavidin were able to resist the fouling from blood plasma (90% reduction with respect to bare gold). Moreover, they were employed to demonstrate a model biosensor by immobilization of a biotinylated antibody and subsequent capture of an antigen as monitored in real time by surface plasmon resonance. PMID:25961109
Structure, dynamics, and function of biomolecules
International Nuclear Information System (INIS)
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors enhanced Los Alamos' core competency in Bioscience and Biotechnology by building on present strengths in experimental techniques, theory, high-performance computing, modeling, and simulation applied to biomolecular structure, dynamics, and function. Specifically, the authors strengthened their capabilities in neutron/x-ray scattering, x-ray crystallography, NMR, laser, and optical spectroscopies. Initially they focused on supporting the Los alamos Neutron Science Center (LANSCE) in the design and implementation of new neutron scattering instrumentation, they developed new methods for analysis of scattering data, and they developed new projects to study the structures of biomolecular complexes. The authors have also worked to strengthen interactions between theory and experiment, and between the biological and physical sciences. They sponsored regular meetings of members from all interested LANL technical divisions, and supported two lecture series: ''Biology for Physicists'' and ''Issues in Modern Biology''. They also supported the formation of interdisciplinary/inter-divisional teams to develop projects in science-based bioremediation and an integrated structural biology resource. Finally, they successfully worked with a multidisciplinary team to put forward the Laboratory's Genome and Beyond tactical goal
Structure, dynamics, and function of biomolecules
Energy Technology Data Exchange (ETDEWEB)
Frauenfelder, H.; Berendzen, J.R.; Garcia, A.; Gupta, G.; Olah, G.A.; Terwilliger, T.C.; Trewhella, J.; Wood, C.C.; Woodruff, W.H.
1998-11-01
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors enhanced Los Alamos' core competency in Bioscience and Biotechnology by building on present strengths in experimental techniques, theory, high-performance computing, modeling, and simulation applied to biomolecular structure, dynamics, and function. Specifically, the authors strengthened their capabilities in neutron/x-ray scattering, x-ray crystallography, NMR, laser, and optical spectroscopies. Initially they focused on supporting the Los alamos Neutron Science Center (LANSCE) in the design and implementation of new neutron scattering instrumentation, they developed new methods for analysis of scattering data, and they developed new projects to study the structures of biomolecular complexes. The authors have also worked to strengthen interactions between theory and experiment, and between the biological and physical sciences. They sponsored regular meetings of members from all interested LANL technical divisions, and supported two lecture series: ''Biology for Physicists'' and ''Issues in Modern Biology''. They also supported the formation of interdisciplinary/inter-divisional teams to develop projects in science-based bioremediation and an integrated structural biology resource. Finally, they successfully worked with a multidisciplinary team to put forward the Laboratory's Genome and Beyond tactical goal.
Network motifs: structure does not determine function
Directory of Open Access Journals (Sweden)
Stumpf Michael PH
2006-05-01
Full Text Available Abstract Background A number of publications have recently examined the occurrence and properties of the feed-forward motif in a variety of networks, including those that are of interest in genome biology, such as gene networks. The present work looks in some detail at the dynamics of the bi-fan motif, using systems of ordinary differential equations to model the populations of transcription factors, mRNA and protein, with the aim of extending our understanding of what appear to be important building blocks of gene network structure. Results We develop an ordinary differential equation model of the bi-fan motif and analyse variants of the motif corresponding to its behaviour under various conditions. In particular, we examine the effects of different steady and pulsed inputs to five variants of the bifan motif, based on evidence in the literature of bifan motifs found in Saccharomyces cerevisiae (commonly known as baker's yeast. Using this model, we characterize the dynamical behaviour of the bi-fan motif for a wide range of biologically plausible parameters and configurations. We find that there is no characteristic behaviour for the motif, and with the correct choice of parameters and of internal structure, very different, indeed even opposite behaviours may be obtained. Conclusion Even with this relatively simple model, the bi-fan motif can exhibit a wide range of dynamical responses. This suggests that it is difficult to gain significant insights into biological function simply by considering the connection architecture of a gene network, or its decomposition into simple structural motifs. It is necessary to supplement such structural information by kinetic parameters, or dynamic time series experimental data, both of which are currently difficult to obtain.
Lesinski, T.; Bennaceur, K.; Duguet, T; Meyer, J.
2006-01-01
We study the effect of the splitting of neutron and proton effective masses with isospin asymmetry on the properties of the Skyrme energy density functional. We discuss the ability of the latter to predict observable of infinite matter and finite nuclei, paying particular attention to controlling the agreement with ab-initio predictions of the spin-isospin content of the nuclear equation of state, as well as diagnosing the onset of finite size instabilities, which we find to...
Short-Range Nucleon-Nucleon Correlations
Higinbotham, Douglas W
2010-01-01
Valence-shell nucleon knock-out experiments, such as 12C(e,e'p)11B, measure less strength then is predicted by independent particle shell model calculations. The theoretical solution to this problem is to include the correlations between the nucleons in the nucleus in the calculations. Motivated by these results, many electron scattering experiments have tried to directly observe these correlations in order to gain new insight into the short-range part of the nucleon-nucleon potential. Unfortunately, many competing mechanisms can cause the same observable final-state as an initial-state correlation, making truly isolating the signal extremely challenging. This paper reviews the recent experimental evidence for short-range correlations, as well as explores the possibility that such correlations are responsible for the EMC effect in the 0.3 < xB < 0.7 deep inelastic scattering ratios.
Short-Range Nucleon-Nucleon Correlations
Higinbotham, Douglas W.
2011-10-01
Valence-shell nucleon knock-out experiments, such as 12C(e,e'p)11B, measure less strength then is predicted by independent particle shell model calculations. The theoretical solution to this problem is to include the correlations between the nucleons in the nucleus in the calculations. Motivated by these results, many electron scattering experiments have tried to isolate the signal from these correlations in order to gain new insight into the short-range part of the nucleon-nucleon potential. Unfortunately, many competing mechanisms can cause the same observable final-state as an initial-state correlation, making truly isolating the signal extremely challenging. This paper reviews the recent experimental evidence for short-range correlations, as well as explores the possibility that such correlations are responsible for the EMC effect in the 0.3
Repulsive short-range three-nucleon interaction
International Nuclear Information System (INIS)
The three-nucleon interaction that is implied by the pion and the effective scalar and vector meson exchange components of the nucleon-nucleon interaction arises from the excitation of intermediate nucleon-antinucleon pairs. Using several wave-function models we show that this interaction is repulsive, reducing the calculated binding energy of the trinucleons by about 200--300 keV. The contributions of intermediate N(1440) resonances (and the same meson exchanges) to this three-nucleon interaction are also estimated and shown to be small
Overlap functions for reaction theories: challenges and open problems
International Nuclear Information System (INIS)
The overlap functions between the nuclear wave functions in initial and final states are important structural quantities that enter the amplitudes of nuclear reactions such as transfer, knockout and radiative capture. They carry information about the single-particle structure and about the nucleonnucleon interactions and correlations in atomic nuclei. The current status of knowledge of overlap functions is reviewed with an emphasis on their theoretical calculation. The open problems associated with their prediction are highlighted and challenges are discussed. (paper)
Energy Technology Data Exchange (ETDEWEB)
Pita, S
2000-09-01
The structure of the neutron rich light nuclei {sup 11}Be and {sup 10}Li has been investigated by means of one nucleon transfer reactions. The experiments have been carried out at GANIL in inverse kinematics using {sup 11}Be secondary beams. The {sup 11}Be(p,d){sup 10}Be reaction bas been studied at 35.3 MeV/u. The {sup 10}Be ejectiles were analyzed by the spectrometer SPEG, and coincident deuterons were detected in the position sensitive silicon detector CHARISSA. Transfer cross sections to 0{sup +}{sub 1} and 2{sup +}{sub 1}, states in {sup 10}Be were measured up to {theta}{sub CM} = 16 deg. and compared to DWBA and CRC predictions. The effects of neutron-cure couplings on reaction form factors have been studied by solving coupled equations in the framework of a vibrational model. It is shown that the rate of core excitation {sup 10}Be{sub 2+} in the {sup 11}Be{sub gs} wave function is overestimated by a standard analysis with form factors given by the usual Separation Energy prescription. The former model predicts a rate of core excitation of 16% and leads to theoretical cross sections which are in good agreement with the experimental data. The aim of the {sup 11}Be(d,{sup 3}He){sup 10}Li experiment, realized at 37 MeV/u, was to measure the distribution of the 2s neutron strength in the unbound nucleus {sup 10}Li. The energy spectrum was deduced from the {sup 3}He energy and angle measured by the silicon strip detector array MUST. An asymmetric peak is clearly observed near the threshold, with a maximum at -S{sub n} = 130 keV. This constitutes a direct proof of the inversion of 2s and 1p{sub 1/2} shells in {sup 10}Li, which was until now a controversial question in spite of many experimental efforts. On the other band the analysis of the {sup 11}Be(d,t){sup 10}Be reaction studied in the same experiment confirms the results obtained in the {sup 11}Be(p,d){sup 10}Be reaction concerning the {sup 11}Be{sub gs} structure. This work shows the interest and feasibility of studies of the shell properties of exotic nuclei using transfer reactions induced by radioactive beams and constitutes the beginning of a program devoted to this kind of experiment. (author)
Pionic background for nucleon-nucleon observables
International Nuclear Information System (INIS)
A method is presented that allows the unambiguous definition of the one pion exchange contribution to nucleon-nucleon scattering observables and then use it to determine those waves where values of phase shifts and mixing parameters may be understood as sums of pionic and non-pionic dynamical effects. This helps the assessment of the explicative power of the various existing phenomenological potentials and may eventually lead to ways of discriminating their effectiveness. (author) 16 refs.; 19 figs.; 2 tabs
Improved chiral nucleon-nucleon potential up to next-to-next-to-next-to-leading order
Epelbaum, E; Meiner, U -G
2014-01-01
We present improved nucleon-nucleon potentials derived in chiral effective field theory up to next-to-next-to-next-to-leading order. We argue that the nonlocal momentum-space regulator employed in the two-nucleon potentials of Refs. [E. Epelbaum, W. Gloeckle, U.-G. Mei{\\ss}ner, Nucl. Phys. A747 (2005) 362], [D.R. Entem, R. Machleidt, Phys. Rev. C68 (2003) 041001] is not the most efficient choice, in particular since it affects the long-range part of the interaction. We are able to significantly reduce finite-cutoff artefacts by using an appropriate regularization in coordinate space which maintains the analytic structure of the amplitude. The new potentials do not require the additional spectral function regularization employed in Ref. [E. Epelbaum, W. Gloeckle, U.-G. Mei{\\ss}ner, Nucl. Phys. A747 (2005) 362] to cut off the short-range components of the two-pion exchange and make use of the low-energy constants c_i and d_i determined from pion-nucleon scattering without any fine tuning. We discuss in detail t...
NuTeV structure function measurement
Energy Technology Data Exchange (ETDEWEB)
Tzanov, M.; /Pittsburgh U.
2005-07-01
The NuTeV experiment obtained high statistics samples of neutrino and antineutrino charged current events during the 1996-1997 Fermilab fixed target run. The experiment combines sign-selected neutrino and antineutrino beams and the upgraded CCFR iron-scintillator neutrino detector. A precision continuous calibration beam was used to determine the muon and hadron energy scales to a precision of 0.7% and 0.43% respectively. The structure functions F{sub 2}(x, Q{sup 2}) and xF{sub 3}(x, Q{sup 2}) obtained by fitting the y-dependence of the sum and the difference of the {nu} and {bar {nu}} differential cross sections are presented.
The Spin Structure Function g2
International Nuclear Information System (INIS)
We have measured the spin structure functions g2p and g2d over the kinematic range 0.02 ? x ? 0.8 and 0.7 ? Q2 ? 20 GeV2 by scattering 29.1 and 32.3 GeV longitudinally polarized electrons from transversely polarized NH3 and 6LiD targets. Our measured g2 approximately follows the twist-2 Wandzura-Wilczek calculation. The twist-3 reduced matrix elements d2p and d2n are less than two standard deviations from zero. The data are inconsistent with the Burkhardt-Cottingham sum rule. The Efremov-Leader-Teryaev integral is consistent with zero within our measured kinematic range
Energy Technology Data Exchange (ETDEWEB)
Kim, Sung-Hou; Shin, Dong Hae; Hou, Jingtong; Chandonia, John-Marc; Das, Debanu; Choi, In-Geol; Kim, Rosalind; Kim, Sung-Hou
2007-09-02
Advances in sequence genomics have resulted in an accumulation of a huge number of protein sequences derived from genome sequences. However, the functions of a large portion of them cannot be inferred based on the current methods of sequence homology detection to proteins of known functions. Three-dimensional structure can have an important impact in providing inference of molecular function (physical and chemical function) of a protein of unknown function. Structural genomics centers worldwide have been determining many 3-D structures of the proteins of unknown functions, and possible molecular functions of them have been inferred based on their structures. Combined with bioinformatics and enzymatic assay tools, the successful acceleration of the process of protein structure determination through high throughput pipelines enables the rapid functional annotation of a large fraction of hypothetical proteins. We present a brief summary of the process we used at the Berkeley Structural Genomics Center to infer molecular functions of proteins of unknown function.
Controlling Function and Structure with DNA
DEFF Research Database (Denmark)
Trring, Thomas
2011-01-01
In this thesis, the research on three different topics will be described. The overall area of the research is DNA nanotechnology, and the first chapter is therefore an introduction to DNA, and its advantages as a building material. The first research topic is the development of a new method for constructing DNA-protein hybrids. The project is still ongoing, but our initial results and thoughts on the design are reported. The design was based on the concept of DNA directed chemistry, where stable covalent bonds are directed by weaker non-covalent bonds. Applying this concept, an aptamer for the human ?-thrombin was used to direct an oligonucleotide with an activated ester capable of forming covalent bonds with the lysine amino acids. Initial results have demonstrated that such rationally designed systems could indeed result in DNA-protein conjugates. Furthermore, future research strategies and ideas are presented. The second research topic concerns our contributions to the field of DNA origami. This includesinvestigations of single molecule reactions on a DNA origami platform. The reaction between an amine and an activated ester, as well as the Huisgen-Meldal-Sharpless reaction were investigated on a two dimensional DNA origami platform. This was done by incorporating functional groups on the surface of the origami, and reacting these with biotin analogues carrying the complementary functional groups. Successful reactions could then be observed using atomic force microscopy after addition of the protein streptavidin. While the implementation of chemical functionalities on origami can be achieved during automated DNA synthesis, this is laborious and costly. In a separate research project we aimed at improving the accessibility by applying an enzymatic labelling method. We demonstrated that the DNA origami could be massively modified fast and efficiently with versatile groups such as amines, fluorophores and biotin. Applying small dynamic DNA structures to control the function of so-called photosensitizers, was the aim of the third and final research topic presented. Photosensitizers are functional molecules that upon irradiation can excite naturally occurring triplet oxygen to the cytotoxic singlet oxygen. This process is interesting in terms of photodynamic therapy, but lack of control is limiting the applications. The excitation can be controlled by installing quenching molecules close to the photosensitizer, and we exploited this by tethering the two molecules together with a dynamic DNA nanostructure, known as an i-motif. This allowed us to control the distance between the two molecules, and thereby the excitation of triplet oxygen. Finally, the thesis is concluded with an outlook and possible future research strategies.
Structural and Functional Genomics of Tomato
Directory of Open Access Journals (Sweden)
Luigi Frusciante
2008-01-01
Full Text Available Tomato (Solanum lycopersicum L. is the most intensively investigated Solanaceous species both in genetic and genomics studies. It is a diploid species with a haploid set of 12 chromosomes and a small genome (950âMb. Based on the detailed knowledge on tomato structural genomics, the sequencing of the euchromatic regions started in the year 2005 as a common effort of different countries. The manuscript focuses on markers used for tomato, on mapping efforts mainly based on exploitation of natural biodiversity, and it gives an updated report on the international sequencing activities. The principal tools developed to explore the function of tomato genes are also summarized, including mutagenesis, genetic transformation, and transcriptome analysis. The current progress in bioinformatic strategies available to manage the overwhelming amount of data generated from different tomato âomicsâ approaches is reported, and emphasis is given to the effort of producing a computational workbench for the analysis of the organization, as well as the functionality and evolution of the Solanaceae family.
Structure, Function, and Evolution of Rice Centromeres
Energy Technology Data Exchange (ETDEWEB)
Jiang, Jiming
2010-02-04
The centromere is the most characteristic landmark of eukaryotic chromosomes. Centromeres function as the site for kinetochore assembly and spindle attachment, allowing for the faithful pairing and segregation of sister chromatids during cell division. Characterization of centromeric DNA is not only essential to understand the structure and organization of plant genomes, but it is also a critical step in the development of plant artificial chromosomes. The centromeres of most model eukaryotic species, consist predominantly of long arrays of satellite DNA. Determining the precise DNA boundary of a centromere has proven to be a difficult task in multicellular eukaryotes. We have successfully cloned and sequenced the centromere of rice chromosome 8 (Cen8), representing the first fully sequenced centromere from any multicellular eukaryotes. The functional core of Cen8 spans ~800 kb of DNA, which was determined by chromatin immunoprecipitation (ChIP) using an antibody against the rice centromere-specific H3 histone. We discovered 16 actively transcribed genes distributed throughout the Cen8 region. In addition to Cen8, we have characterized eight additional rice centromeres using the next generation sequencing technology. We discovered four subfamilies of the CRR retrotransposon that is highly enriched in rice centromeres. CRR elements are constitutively transcribed and different CRR subfamilies are differentially processed by RNAi. These results suggest that different CRR subfamilies may play different roles in the RNAi-mediated pathway for formation and maintenance of centromeric chromatin.
Structure, function, and mechanism of ribonucleotide reductases.
Kolberg, Matthias; Strand, Kari R; Graff, Pl; Andersson, K Kristoffer
2004-06-01
Ribonucleotide reductase (RNR) is the enzyme responsible for the conversion of ribonucleotides to 2'-deoxyribonucleotides and thereby provides the precursors needed for both synthesis and repair of DNA. In the recent years, many new crystal structures have been obtained of the protein subunits of all three classes of RNR. This review will focus upon recent structural and spectroscopic studies, which have offered deeper insight to the mechanistic properties as well as evolutionary relationship and diversity among the different classes of RNR. Although the three different classes of RNR enzymes depend on different metal cofactors for the catalytic activity, all three classes have a conserved cysteine residue at the active site located on the tip of a protein loop in the centre of an alpha/beta-barrel structural motif. This cysteine residue is believed to be converted into a thiyl radical that initiates the substrate turnover in all three classes of RNR. The functional and structural similarities suggest that the present-day RNRs have all evolved from a common ancestral reductase. Nevertheless, the different cofactors found in the three classes of RNR make the RNR proteins into interesting model systems for quite diverse protein families, such as diiron-oxygen proteins, cobalamin-dependent proteins, and SAM-dependent iron-sulfur proteins. There are also significant variations within each of the three classes of RNR. With new structures available of the R2 protein of class I RNR, we have made a comparison of the diiron centres in R2 from mouse and Escherichia coli. The R2 protein shows dynamic carboxylate, radical, and water shifts in different redox forms, and new radical forms are different from non-radical forms. In mouse R2, the binding of iron(II) or cobalt(II) to the four metal sites shows high cooperativity. A unique situation is found in RNR from baker's yeast, which is made up of heterodimers, in contrast to homodimers, which is the normal case for class I RNR. Since the reduction of ribonucleotides is the rate-limiting step of DNA synthesis, RNR is an important target for cell growth control, and the recent finding of a p53-induced isoform of the R2 protein in mammalian cells has increased the interest for the role of RNR during the different phases of the cell cycle. PMID:15158709
PREFACE: Structure and Function of Biomolecules
Cieplak, Marek; Sienkiewicz, Andrzej
2005-05-01
The Workshop on the Structure and Function of Biomolecules took place in Bedlewo near Poznan, Poland, on 13-15 May 2004, two weeks after Poland joined the European Community. The Workshop was sponsored by the ASPECT Centre of Excellence for Advanced Spectroscopy Applications in Physics, Modern Science, Biology and Environmental Protection (the European Community contract GMA1-2002-72801) and by the Institute of Physics, Polish Academy of Sciences. The Workshop gathered together approximately 100 participants mostly from the European Community but also from Canada, Russia, Switzerland, Turkey and the USA. The scientific aim of this Workshop was to provide an active forum for cross-disciplinary interactions between specialists who are active in different fields related to biomolecules, with an emphasis on proteins and nucleic acids. The workshop covered both experimental and theoretical issues. The subjects that were discussed included: mechanical stretching of biomolecules, protein kinetics and structure, aggregation of biomolecules, and novel spectroscopic methods for studying protein conformation. There were 36 invited lectures and 33 poster contributions presented at the Workshop. This Special Issue of Journal of Physics: Condensed Matter contains a sample of the research presented at the Workshop.
Structure and functionality of bromine doped graphite
Energy Technology Data Exchange (ETDEWEB)
Hamdan, Rashid; Kemper, A. F.; Cao Chao; Cheng, H. P. [Department of Physics and Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)
2013-04-28
First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br{sub 2}). However, with increased compression (decreased layer-layer separation) Br{sub 2} molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br{sub 2} molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.
Structure and functionality of bromine doped graphite
International Nuclear Information System (INIS)
First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br2). However, with increased compression (decreased layer-layer separation) Br2 molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br2 molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.
Measurements of the longitudinal structure function and |V{sub cs}| in the CCFR experiment
Energy Technology Data Exchange (ETDEWEB)
Yang, U.K. [and others
1998-07-01
Measurements of charged current neutrino and anti-neutrino nucleon interactions in the CCFR detector are used to extract the structure functions, F{sub 2}, xF{sub 3}{sup {nu}} , xF{sub 3}{sup {anti {nu}}} and R(longitudinal) in the kinematic region 0.01 < x < 0.6 and 1 < Q{sup 2} < 300 GeV{sup 2}. The new measurements of R in the x < 0.1 region provide a constraint on the level of the gluon distribution. The x and Q{sup 2} dependence of R is compared with a QCD based fit to previous data. The CKM matrix element {vert_bar}V{sub cs}{vert_bar} is extracted from a combined analysis of xF{sub 3} and dimuon data.
Nucleon-nucleon scattering in a chiral constituent quark model
Bartz, D; Stancu, Fl.
2001-01-01
We study the nucleon-nucleon interaction in a chiral constituent quark model by using the resonating group method, convenient for treating the interaction between composite particles. The calculated phase shifts for the 3S1 and 1S0 channels show the presence of a strong repulsive core due to the combined effect of the quark interchange and the spin-flavour structure of the effective quark-quark interaction. Such a symmetry structure stems from the pseudoscalar meson exchange between the quarks and is a consequence of the spontaneous breaking of the chiral symmetry. We perform single and coupled channel calculations and show the role of coupling of the $\\Delta\\Delta$ and hidden color CC channels on the behaviour of the phase shifts.
Polarized and Unpolarized Structure Functions in the Valon Model
Energy Technology Data Exchange (ETDEWEB)
Arash, Firooz [Physics Department, Tafresh University, Tafresh (Iran, Islamic Republic of)]. E-mail: farash@cic.aut.ac.ir
2006-02-15
Hadrons are considered as the bound states of their structureful constituents, the Valons. The valon structure is calculated perturbatively in QCD; which is universal and independent of the hosting hadron. This structure is used to calculate Proton and pion structure functions. For the case of polarized structure function, the valon representation, not only gives all the available data on g {sup p,n,d} {sub 1}, but also requires a sizable orbital angular momentum associated with the partonic structure of the valon.
Polarized and Unpolarized Structure Functions in the Valon Model
Arash, Firooz
2006-02-01
Hadrons are considered as the bound states of their structureful constituents, the Valons. The valon structure is calculated perturbatively in QCD; which is universal and independent of the hosting hadron. This structure is used to calculate Proton and pion structure functions. For the case of polarized structure function, the valon representation, not only gives all the available data on gp,n,d1, but also requires a sizable orbital angular momentum associated with the partonic structure of the valon.
Polarized and Unpolarized Structure Functions in the Valon Model
International Nuclear Information System (INIS)
Hadrons are considered as the bound states of their structureful constituents, the Valons. The valon structure is calculated perturbatively in QCD; which is universal and independent of the hosting hadron. This structure is used to calculate Proton and pion structure functions. For the case of polarized structure function, the valon representation, not only gives all the available data on g p,n,d1, but also requires a sizable orbital angular momentum associated with the partonic structure of the valon
Orbital angular momentum in the nucleons
Lorc, Cdric
2014-01-01
In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular momentum and its extraction from experimental data. We summarize the present situation and discuss recent developments in this field.
Leading and higher twists in proton, neutron and deuteron unpolarized structure functions F2
Energy Technology Data Exchange (ETDEWEB)
S. Simula
2007-03-01
We summarize the results of a recent global analysis of proton and deuteron F2 structure function world data performed over a large range of kinematics, including recent measurements done at JLab with the CLAS detector. From these data the lowest moments (n?10) of the unpolarized structure functions are determined with good statistics and systematics. The Q2 evolution of the extracted moments is analyzed in terms of an OPE-based twist expansion, taking into account soft-gluon effects at large x. A clean separation among the leading- and higher-twist terms is achieved. By combining proton and deuteron measurements the lowest moments of the neutron F2 structure function are determined and its leading-twist term is extracted. Particular attention is paid to nuclear effects in the deuteron, which become increasingly important for the higher moments. Our results for the non-singlet, isovector (p-n) combination of the leading-twist moments are used to test recent lattice simulations. We also determine the lowest few moments of the higher-twist contributions, and find these to be approximately isospin independent, suggesting the possible dominance of ud correlations over uu and dd in the nucleon.
Measurement of the deuterium structure function A(q2) by electron scattering
International Nuclear Information System (INIS)
This work describes an electron scattering experiment on the deuterium nucleus. We were interested in the structure function A(q2) of this nucleus. This structure function is particularly sensitive to the nucleon-nucleon potential and to the neutron electric form factor. Cross sections have been measured at four incident energies: 200, 300, 500, 650 MeV and at scattering angles ranging from 300 to 1200. The momentum transfer range between q2 = 0.5 and q2 = 18 fm-2 was covered. Special care was given to the accuracy of the data. We have studied in detail all experimental corrections, in order to measure absolute cross sections. Most of our data have statistical errors smaller than 1%. The overall accuracy of our cross sections was confirmed by quasi-simultaneous measurements on a hydrogen target. These measurements were found to be in perfect agreement with a prediction computed using a fit to the world data on the electric and magnetic form factors of the proton. We have also measured cross sections for the deuteron electrodesintegration at threshold. These measurements together with cross sections measured previously at 1550 allow a separation of the longitudinal and transverse components of this process. The improved precision of our new data on the deuteron provide a stringent test for the presently available theoretical calculations. We have studied the sensitivity of A(q2) to different theoretical ingredients. We have also shown that within some assumptions, our measurements permit a raisonable estimation of the uncertainty on the neutron electric form factor
Soil-Borne Microbial Functional Structure across Different Land Uses
Kuramae, Eiko E.; Jizhong Z. Zhou; Kowalchuk, George A.; van Veen, Johannes A
2014-01-01
Land use change alters the structure and composition of microbial communities. However, the links between environmental factors and microbial functions are not well understood. Here we interrogated the functional structure of soil microbial communities across different land uses. In a multivariate regression tree analysis of soil physicochemical properties and genes detected by functional microarrays, the main factor that explained the different microbial community functional structures was C...
Polarized light ions and spectator nucleon tagging at EIC
Guzey, V; Hyde, Ch; Nadel-Turonski, P; Park, K; Sargsian, M; Strikman, M; Weiss, C
2014-01-01
An Electron-Ion Collider (EIC) with suitable forward detection capabilities would enable a unique experimental program of deep-inelastic scattering (DIS) from polarized light nuclei (deuterium 2H, helium 3He) with spectator nucleon tagging. Such measurements promise significant advances in several key areas of nuclear physics and QCD: (a) neutron spin structure, by using polarized deuterium and eliminating nuclear effects through on-shell extrapolation in the spectator proton momentum; (b) quark/gluon structure of the bound nucleon at x > 0.1 and the dynamical mechanisms acting on it, by measuring the spectator momentum dependence of nuclear structure functions; (c) coherent effects in QCD, by exploring shadowing in tagged DIS on deuterium at x << 0.1. The JLab MEIC design (CM energy sqrt{s} = 15-50 GeV/nucleon, luminosity ~ 10^{34} cm^{-2} s^{-1}) provides polarized deuterium beams and excellent coverage and resolution for forward spectator tagging. We summarize the physics topics, the detector and bea...
Off-shell properties of the Paris nucleon-nucleon potential and implications for few-body systems
International Nuclear Information System (INIS)
We investigate the half-off-shell properties for the Paris nucleon-nucleon potential and for a separable representation of it. Deuteron bound-state and scattering wave functions as well as Noyes-Kowalski functions are considered. Essential features with respect to elastic electron-deuteron and nucleon-deuteron scattering are discussed. We find that some polarization observables of these processes dismiss certain off-shell behaviours encountered, for instance, in various phenomenological separable potentials
International Nuclear Information System (INIS)
We present results on inelastic J/? production from muon interactions with hydrogen and deuterium at an incident muon energy of 280 GeV. The measured cross section ratio per nucleon for muon-induced J/? production in deuterium and hydrogen was found to be R(D2/H2)=1.010.15. The colour singlet model is shown to provide a good description of the observed differential cross section apart from a normalisation factor. The comparison between the observed cross section and the colour singlet model prediction allows the extraction of the gluon structure function G(?) of the nucleon. The momentum fraction ? of the nucleon carried by the gluon is measured in the range of ?=[0.02,0.30]. The normalised gluon distribution of free nucleons thus found can be parametrised as ?G(?)=1/2(?+1)(1-?)?, with ?=5.10.9(stat.). (orig.)
Modeling Nucleon Generalized Parton Distributions
Energy Technology Data Exchange (ETDEWEB)
Radyushkin, Anatoly V. [JLAB, Old Dominion U.
2013-05-01
We discuss building models for nucleon generalized parton distributions (GPDs) H and E that are based on the formalism of double distributions (DDs). We find that the usual "DD+D-term'' construction should be amended by an extra term, generated by GPD E(x,\\xi). Unlike the $D$-term, this function has support in the whole -1 < x< 1 region, and in general does not vanish at the border points|x|=\\xi.
Deep inelastic lepton scattering on nuclei: operator product expansion and meson-nucleon theory
International Nuclear Information System (INIS)
A novel point of view on the x-rescaling model in lepton-nucleous deep inetic scattering is suggested. Using the operator product expansion method within the effective meson-nucleon theory, a rigorous consideration of the scattering on the deuteron is presented. It is demonstrated that with the contributions interpreter as the Fermi motion corrections, the x-rescaling idea is exactly reproduced. The diagrams of scattering of bound nucleons have also been computed numerically. An example of application of the method, viz. the problem of extraction of the neutron structure function from the combined proton-deuteron data, is considered. 26 refs.; 5 figs
Nucleon form factors, generalized parton distributions and quark angular momentum
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Exact symmetries and the role of the pion cloud in deep-inelastic electron-nucleon scattering
International Nuclear Information System (INIS)
A careful analysis of exact symmetries, such as the charge conjugation symmetry and the electromagnetic and baryon current conservation, shows that exactly two nontrivial Feynman diagrams contribute to deep-inelastic inclusive pion electroproduction from the nucleon to O(g?NN2). The same analysis reveals certain relationships between the two graphs. The two graphs are expressed as convolutions of the pion [g?(y)] and the nucleon [gN(y)] smearing functions and their respective deep-inelastic structure functions. The nucleon smearing functions are evaluated in three models of the nucleon off-shell dependence of the ?NN vertex function and they turn out to have remarkably similar shapes. It is shown that this universality of gN(y) persists in a wide class of models. Such universal gN(y) peaks at y0=1-m?/MN=0.85 and allows a simple parton model interpretation. Furthermore, the normalized smearing functions approximately satisfy the Berger-Coester-Wiringa-Thomas ansatz g?(y)=gN(1-y) for two of the three models examined. Strong constraints on the nucleon off-shell dependence of the ?NN vertex function [g?NN(pN2)] are obtained using the observed Gottfried sum rule violation as empirical input
Pion Structure Function $F_{2}^{\\pi}$ in the Valon Model
Arash, Firooz
2003-01-01
Partonic structure of constituent quark (or{\\it{valon}}) in the Next-to-Leading Order is used to calculate pion structure function. This is a further demonstration of the finding that the constituent quark structure is universal, and once it is calculated, the Structure of any hadron can be predicted thereafter, using a convolution method, without introducing any new free parameter. The results are compared with the pion structure function from ZEUS Coll. Leading Neutron Pro...
Molecular evolution, structure, and function of peroxidasins.
Soudi, Monika; Zamocky, Marcel; Jakopitsch, Christa; Furtmller, Paul G; Obinger, Christian
2012-09-01
Peroxidasins represent the subfamily 2 of the peroxidase-cyclooxygenase superfamily and are closely related to chordata peroxidases (subfamily 1) and peroxinectins (subfamily 3). They are multidomain proteins containing a heme peroxidase domain with high homology to human lactoperoxidase that mediates one- and two-electron oxidation reactions. Additional domains of the secreted and glycosylated metalloproteins are type C-like immunoglobulin domains, typical leucine-rich repeats, as well as a von Willebrand factor C module. These are typical motifs of extracellular proteins that mediate protein-protein interactions. We have reconstructed the phylogeny of this new family of oxidoreductases and show the presence of four invertebrate clades as well as one vertebrate clade that includes also two different human representatives. The variability of domain assembly in the various clades was analyzed, as was the occurrence of relevant catalytic residues in the peroxidase domain based on the knowledge of catalysis of the mammalian homologues. Finally, the few reports on expression, localization, enzymatic activity, and physiological roles in the model organisms Drosophila melanogaster, Caenorhabditis elegans, and Homo sapiens are critically reviewed. Roles attributed to peroxidasins include antimicrobial defense, extracellular matrix formation, and consolidation at various developmental stages. Many research questions need to be solved in future, including detailed biochemical/physical studies and elucidation of the three dimensional structure of a model peroxidasin as well as the relation and interplay of the domains and the in vivo functions in various organisms including man. PMID:22976969
Structure and function of DNA polymerase ?
International Nuclear Information System (INIS)
DNA polymerases are enzymes playing the central role in DNA metabolism, including DNA replication, DNA repair and recombination. DNA polymerase ? (pol ? DNA polymerase ? (pol ?) and terminal deoxynucleotidyltransferase (TdT) in X family DNA polymerases function in non-homologous end-joining (NHEJ), which is the predonmiant repair pathway for DNA double-strand breaks (DSBs). NHEJ involves enzymes that capture both ends of the broken DNA strand, bring them together in a synaptic DNA-protein complex, and repair the DSB. Pol ? and pol ? fill in the gaps at the junction to maintain the genomic integrity. TdT synthesizes N region at the junction during V(D)J recombination and promotes diversity of immunoglobulin or T-cell receptor gene. Among these three polymerases, the regulatory mechanisms of pol ? remain rather unclear. We have approached the mechanism of pol ? from both sides of structure and cellular dynamics. Here, we propose some new insights into pol ? and the probable NHEJ model including our findings. (author)
Three-pion exchange nucleon-nucleon potentials with virtual $\\Delta$-isobar excitation
Kaiser, N
2015-01-01
The nucleon-nucleon interaction arising from the exchange of three pions and the excitation of $\\Delta(1232)$-isobars in intermediate states is studied. Approximating the $\\Delta$-propagator by the inverse $\\Delta$N mass-splitting, analytical expressions are derived for the spectral-functions of the isoscalar and isovector central, spin-spin and tensor NN-potentials in momentum-space. A trans- lation of the spectral-functions into coordinate-space potentials reveals that the...
International Nuclear Information System (INIS)
The longitudinal momentum distributions of the cross sections of heavy projectile-like residues after fast, direct two-like-nucleon knockout reactions are discussed. Both the two-nucleon inelastic breakup (stripping) and the stripping-diffraction removal events are considered. We show that, because the two mechanisms have a very similar nuclear surface localization, they generate essentially identical longitudinal momentum distributions. The approach used combines reaction dynamics, using the sudden, eikonal and spectator-core approximations, with structure wave functions from the many-body shell model. The sensitivities of the resulting longitudinal momentum distributions to the orbital angular momenta, the separation energies, and the angular momentum coupling of the two removed nucleons are clarified. In particular, the widths of these distributions are shown to provide a very clear signal of the total angular momentum of the removed-nucleon pair--pairs coupled to larger total angular momentum giving broader distributions. These now complete distributions, from correlated wave functions, are significantly different from earlier uncorrelated estimates. Confirmation of these theoretical expectations is presented, based on very recent intermediate-energy, residue final-state inclusive and exclusive two-nucleon removal measurements.
Nucleon-nucleon scattering phase shifts
International Nuclear Information System (INIS)
Here are presented 0 to 800 MeV nucleon-nucleon elastic and inelastic phase parameters derived by several groups: Arndt and Roper; Hoshizaki; Bugg; Bystricky, Lechanoine, and Lehar; and Bryan, Clark, and VerWest. Resonant-like behavior appears in the 1D2 and 3F3 states above the inelastic threshold in Hoshizaki's analysis but not in Arndt and Roper's. The np data are inadequate to permit determination of the I = O phase parameters above 600 MeV. 27 references