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1

International Nuclear Information System (INIS)

The present status of experimental measurements of the nucleon structure functions is reviewed. The results from nearly all deep inelastic experiments are in good mutual agreement. Principles of the analysis of these structure function data in the framework of QCD are described. The specific features of the perturbative QCD predictions are observed in the data. This provides quantitative tests of the validity of QCD as well as determinations of the various parton distributions in the nucleon and some of the most precise measurements of the strong coupling constant ?s. The future of this field of experimental physics is sketched

2

Diquarks and nucleon structure functions

International Nuclear Information System (INIS)

Formulae for structure functions of the deep-inelastic lepton-nucleon scattering are obtained through relativistic wave functions of systems composed of particles with spins 0, 1/2 and 1, 1/2. These wave functions are solutions of covariant two-particle single-time equations describing the nucleon as a system formed out of a quark and a diquark. Diquark is considered as a boson with the spin 0 and 1. The expressions for the nucleon structure functions are obtained by using the matrix elements of the current operator corresponding to the elastic scattering of the photon on a quark and on a diquark

3

Statistical Model for the Nucleon Structure Functions

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.

Bhalerao, R. S.

1996-01-01

4

Nucleon Structure Functions and Nuclear DIS

The nucleon structure study in nuclear deep inelastic scattering is considered. It is shown that nuclear data provide a new source of information about dynamics of parton distributions in the nucleon. An example of the neutron structure function extraction from the deuteron and proton data is considered. The limit $x\\to 1$ of the neutron to proton structure functions ratio is studied. A link between the deep inelastic scattering off the nucleon at high $x$ and elastic scatte...

Molochkov, A.

2004-01-01

5

Influence of temperature on nucleon structure functions

A simple statistical approach is performed to calculate the nucleon structure functions F2 and xF3 in the kinematic range 0.05Q2<125 GeV by considering the effect of temperature on nucleon radius and mass simultaneously. The role of change in mass and radius with temperature in estimating the nucleon structure function is analyzed. The results show that these effects are significant and the change in effective mass of nucleon affects the structure function about two times greater than that of change in radius.

Ganesamurthy, K.; Hariharan, C.; Muruganantham, S.

2014-10-01

6

Nucleon neutral-current structure functions

International Nuclear Information System (INIS)

The structure of the nucleon is studied by means of deep-inelastic neutrino-nucleon scattering at high energies through the weak neutral current. The neutrino-nucleon scattering events were observed in a 340-metric-ton fine-grained calorimeter exposed to a narrow-band (dichromatic) neutrino beam at Fermilab. The data sample after analysis cuts consists of 9200 charged-current and 3000 neutral-current neutrino and antineutrino events. The neutral-current valence and sea nucleon structure functions are extracted from the x distribution reconstructed from the measured angle and energy of the recoil-hadron shower and the incident narrow-band neutrino-beam energy. They are compared to those extracted from charged-current events analyzed as neutral-current events. It is shown that the nucleon structure is independent of the type of neutrino interaction, which confirms an important aspect of the standard model. The data are also used to determine the value of sin2?W=0.238±0.013±0.015±0.010 for a single-parameter fit, where the first error is from statistical sources, the second from experimental systematic errors, and the third from estimated theoretical errors

7

Parton Gas Model for the Nucleon Structure Functions

A phenomenological model for the nucleon structure functions is presented. Visualising the nucleon as a cavity filled with parton gas in thermal equilibrium and parametrizing the effects due to the finiteness of the nucleon volume, we obtain a good fit to the data on the unpolarized nucleon structure functions.

Bhalerao, R. S.

1995-01-01

8

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

9

Quark model calculations of nucleon structure functions

International Nuclear Information System (INIS)

We present calculations of those structure functions of the nucleon which are measured in deep inelastic electron scattering. A quark model which preserves translational invariance is used. The model exhibits scaling and the structure functions satisfy the Callan-Gross relation in the scaling region. It is possible to fit the experimental values of F2/sup p/(x)-F2/sup n/(x) using wave functions that correspond to a relatively small region of confinement. The ratio of F2/sup n/(x)/F2/sup p/(x) is also calculated. One can explain the deviation of the value of the latter quantity from the value (2/3) obtained in the simplest quark model by allowing the neutron confinement radius to be about 10 percent larger than the corresponding proton radius. We also discuss the role of this radius modification in explaining the deviation of the ratio of the proton and neutron magnetic moments from the value of -(3/2) obtained in standard quark models

10

Measurement of the nucleon structure functions

International Nuclear Information System (INIS)

Measurements have been made of the inclusive scattering of 96, 147, and 219 GeV muons from hydrogen, and of 147 GeV muons from deuterium. Results are presented for the nucleon structure function F2(x,Q2) [equivalent?W2(x,Q2)] for 10 2 2. The value of F2 rises with Q2 at small x, and falls with Q2 at large x, in agreement with the ideas of quantum chromodynamics. An average value of the ratio sigma/sub L//sigma/sub T/ equivalent R = 0.52 +- 0.35 has been obtained for the region 0.003 2 2. The values of F2 from this experiment have been combined with those from other charged-lepton scattering experiments to determine moments of the structure functions. The variation with Q2 of these moments is used to derive values for ?, taking into account corrections up to second order in ?/sub s/. The fit to the data is very good

11

Statistical model for the structure functions of the nucleon

International Nuclear Information System (INIS)

The author presents a model of the structure functions of the nucleon which he has been working on during the past year. The structure functions of the nucleon are measured experimentally in the deep inelastic scattering of leptons off nucleons. The notations he follows are standard. To be specific the author considers the leptons to be electrons or muons but it is obvious that also neutrinos or antinuetrinos can be considered. The relevant tensor W/sub ??/ is related to the Lorentz-covariant structure functions W/sub 1/ and W/sub 2/

12

Towards a lattice calculation of the nucleon structure functions

International Nuclear Information System (INIS)

We have initiated a programme to compute the lower moments of the unpolarised and polarised deep inelastic structure functions of the nucleon in the quenched approxiation. We review our progress to date. (orig.)

13

Towards a lattice calculation of the nucleon structure functions

We have initiated a programme to compute the lower moments of the unpolarised and polarised deep inelastic structure functions of the nucleon in the quenched approximation. We review our progress to date.

Göckeler, M; Ilgenfritz, E M; Perlt, H; Rakow, P; Schierholz, G; Schiller, A; Goeckeler, M; Horsley, R; Ilgenfritz, M; Perlt, H; Schierholz, G; Schiller, A

1994-01-01

14

Structure function in nucleon using a thermal model

International Nuclear Information System (INIS)

A statistical model, that uses a confining potential model for quarks, was used to obtain the structure function of the nucleon. This model shows a good fit for the Gottfried sum rule with a temperature of about 110 MeV. The instanton contribution will give the right split between ? (1232) and the Nucleon. Once adjusted the temperature parameter by the Gottfried sum rule, we show that the experimental result for the strange content of the nucleon can be obtained by adjusting the effective mass of the quark s. (author)

15

Experimental study of structure functions of nucleons and nuclei

International Nuclear Information System (INIS)

The data obtained in experiments of collaboration Bologna-CERN-Dubna-Munic -Sacle (BCDMS) at 120 and 200 GeV and preliminary data at 280 GeV are discussed. The results of structure function measurements in deep inelastic interactions at the above mentioned energies are presented. Experimental data are compared with quantum chromodynamics predictions for structure nucleon function and its moments. The investigation results of quark-parton structure nucleus function are considered as well

16

Energy Technology Data Exchange (ETDEWEB)

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.

Bertini, M.

1995-05-12

17

Truncated Moment Analysis of Nucleon Structure Functions

Energy Technology Data Exchange (ETDEWEB)

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.

A. Psaker; W. Melnitchouk; M. E. Christy; C. E. Keppel

2007-11-16

18

Analysis of scaling violation in nucleon structure functions

International Nuclear Information System (INIS)

Some new measurements of the nucleon structure functions F2 and xF3 have been carried out in an antineutrino experiment with a 15-foot bubble chamber. The structure functions are analyzed. The scaling violation in xF3 can be described by quantum-chromodynamics effects with the scaling parameter #betta#/sub M/S-bar roughly-equal0.3 GeV and also by higher-twist effects

19

Diquark contributions to the nucleon deep inelastic structure functions

International Nuclear Information System (INIS)

The contributions of diquarks to the nucleon structure functions are discussed in the framework of the parton model and in the most general case of both vector and scalar diquarks inside unpolarized and polarized nucleons. The vector diquark anomalous magnetic moment and the scalar-vector and vector-scalar diquark transitions are also taken into account. The properties of the diquarks and of their form factors, required in order for the resulting scaling violations to be compatible with the observed ones, are discussed. (author)

20

Nucleon structure functions in the composite quark-diquark model

International Nuclear Information System (INIS)

An explicit expression is found for the nucleon structural functions through relativistic single-time wave functions of the quark-diquiark system. The formulae obtained independently of the quark interaction dynamics (which determines the wave function form) contain both the term resulting in the xi-scaling violation and solely scaling terms. The form of the scaling part and the character of violation of the structural function scale-invariance behaviour by the prescaling terms are determined by the form of wave functions. The deep-inelastic limit contains the relation of the Callan-Gross form

21

Sum Rules and Moments of the Nucleon Spin Structure Functions

The nucleon has been used as a laboratory to investigate its own spin structure and Quantum Chromodynamics. New experimental data on nucleon spin structure at low to intermediate momentum transfers combined with existing high momentum transfer data offer a comprehensive picture of the transition region from the {\\it confinement} regime of the theory to its {\\it asymptotic freedom} regime. Insight for some aspects of the theory is gained by exploring lower moments of spin structure functions and their corresponding sum rules (i.e. the Gerasimov-Drell-Hearn, Bjorken and Burkhardt-Cottingham). These moments are expressed in terms of an operator product expansion using quark and gluon degrees of freedom at moderately large momentum transfers. The sum rules are verified to a good accuracy assuming that no singular behavior of the structure functions is present at very high excitation energies. The higher twist contributions have been examined through the moments evolution as the moments evolution as the momentum t...

Chen, J P; Meziani, Z E; Meziani, Zein-Eddine

2005-01-01

22

EMC-SLAC-effect and structure nucleon functions in nuclei

International Nuclear Information System (INIS)

The EMC - SLAG-effect is explained without involving ''exotic'' configuration in nuclei. It is shown that the functional dependence of the structure function ratio F2A/F2D is determined by the relation of the total Lagrangian of the NN system that describes the Fermi motion to its part, that is due to scalar meson exchange and leads to the renormalization of the virtual nucleon mass

23

Sum Rules and Moments of the Nucleon Spin Structure Functions

The nucleon has been used as a laboratory to investigate its own spin structure and quantum chromodynamics. New experimental data on nucleon spin structure at low to intermediate momentum transfers combined with existing high momentum transfer data offer a comprehensive picture of the transition region from the confinement regime of the theory to its asymptotic freedom regime. Insight for some aspects of the theory is gained by exploring lower moments of spin structure functions and their corresponding sum rules (i.e. the Gerasimov-Drell-Hearn, Bjorken and Burkhardt-Cottingham). These moments are expressed in terms of an operator-product expansion using quark and gluon degrees of freedom at moderately large momentum transfers. The sum rules are verified to good accuracy assuming that no singular behavior of the structure functions is present at very high excitation energies. The higher-twist contributions have been examined through the moments evolution as the momentum transfer varies from higher to lower values. Furthermore, QCD-inspired low-energy effective theories, which explicitly include chiral symmetry breaking, are tested at low momentum transfers. The validity of these theories is further examined as the momentum transfer increases to moderate values. It is found that chiral perturbation calculations agree reasonably well with the first moment of the spin structure function g1 at momentum transfer of 0.1 GeV2 but fail to reproduce the neutron data in the case of the generalized polarizability ?LT.

Chen, J.-P.; Deur, A.; Meziani, Z.-E.

24

Prescriptions for the scaling variable of the nucleon structure function in nuclei

We tested several choices of the in-medium value of the Bjorken scaling variable assuming the nucleon structure function in nucleus to be the same as that of free nucleon. The results unambiguously show that it is different.

Ryazanov, V. I.; Birbrair, B. L.; Ryskin, M. G.

2006-01-01

25

Nucleon spin structure functions from HERMES: The first year

International Nuclear Information System (INIS)

HERMES, HERA Measurement of Spin, is a second generation exper to study the spin structure of the nucleon by using polarized internal gas targets in the HERA 28 GeV electron storage ring. Scattered positrons and coincident hadrons are detected in an open geometry spectrometer which includes particle identification. Inclusive data with polarized 3He give the spin structure function gn1(x) and the Ellis-Jaffe integral RR? = ?01 gn1(x)dx for the neutron. The semi-inclusive spin asymmetries are a unique and sensitive probe of the flavor dependence of quark helicity distributions and properties of the quark sea. Data taken in 1995 with unpolarized hydrogen and deuterium targets provide measurements of the flavor distributions of sea and valence quarks. In a preliminary analysis, ?n1 = -0.032±0. 013stat. ± O.017syst. is obtained at Q2 = 3(GeV/c)2 for the Ellis-Jaffe integral

26

Convolution model for the structure functions of the nucleon

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...

Keppler, J

1994-01-01

27

Detailed Measurements of Structure Functions from Nucleons and Nuclei

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...

2002-01-01

28

Nucleon structure and nucleon-nucleon interaction

International Nuclear Information System (INIS)

The understanding of the hadronic strucutre of the particles as well as their interactions in the nuclei is a fundamental problem of strong interaction physics. A very successful method to study the nucleons and the nuclei is the elastic and inelastic scattering of relativistic electrons. Such experiments have been performed for a long time, but the better accuracy of the experimental method of today as well as the possibilities to calculate the radiative corrections in a wide energy range led to new results which are sensitive enough to answer important questions in this part of physics. In the first part of this talk we report about the elastic scattering results gained from investigation of e-p and e-d measurements are presented. The cross sections of the elastic electron-nucleon scattering for single photon exchange are given by the Rosenbluth formula. The two form factors, for instance, the electric and the magnetic form factor Gsub(E) and Gsub(M) introduced by Sachs, are pure functions of q2, the squared four momentum carried by the exchanged photon if all particles are on mass-shell. The whole information on the hadronic structure of the nucleons are obtained completely by the q2 dependence of both form factors. (orig./AH)

29

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

30

Structure functions of the nucleon in a statistical model

International Nuclear Information System (INIS)

Deep inelastic scattering is considered in a statistical model of the nucleon. This incorporates certain features which are absent in the standard parton model such as quantum statistical correlations which play a role in the propagation of particles when considering Feynman diagrams containing internal lines. The inclusion of the O(?s) corrections in our numerical calculations allows a good fit to the data for x ? 0.25. The fit corresponds to values of temperature and chemical potential of approximately T = 0.067 GeV and ? = 0.133 GeV. The latter values of parameters, however, give rise, for all x, to a large value for R = ?L/?T. Even when taking into account that all measurements of R suffer from large experimental errors due to the weak dependence of the deep inelastic cross section for charged leptons on R, the size of the discrepancy remains unacceptable. This indicates a shortcoming of the statistical model in its present form to reproduce the structure function of the proton. (orig.)

31

Bound nucleon structure function in the picture of relativistic constituent quarks

International Nuclear Information System (INIS)

The structure function F2N of nucleons in the deuterium, carbon and iron nuclei is calculated as a function of Q2 in two approaches: taking into account the nucleon swelling in nuclei due to the partial deconfinement of quarks in nuclear medium; in the conventional approach of nuclear physics, taking into account the getting off the mass shell of the bound nucleon and Fermi motion in nucleons. It is shown that the conventional approach of nuclear physics does not explain the EMC effect in the region of small x

32

Measurement of the nucleon structure function using high energy muons

Energy Technology Data Exchange (ETDEWEB)

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.

Meyers, P.D.

1983-12-01

33

Non-perturbative effect in the nucleon structure function and the Gottfried sum

We investigate the non-perturbative effect in the nucleon structure function and the Gottfried sum by using a non-perturbative quark propagator with lowest dimensional condensate contributions from the QCD vacuum. It is shown that the non-perturbative effect modifies the conventional quark-parton model formula of the nucleon structure function at finite $Q^2$ and suggests a non-trivial $Q^2$ dependence in the Gottfried sum.

Yang, Jian-jun; Ma, Bo-qiang; Li, Guang-lie

1996-01-01

34

Charged current neutrino and antineutrino interactions and nucleon structure functions

International Nuclear Information System (INIS)

Final results are presented for studies, carried out by the HPWFRO-E310 group at Fermi National Accelerator Laboratory, of inclusive charged current neutrino and antineutrino interactions. The data sample consists of 21578 neutrino and 7358 antineutrino events within the fiducial regions of the calorimeter targets in the energy interval 20 2 >/E with increasing energy. R = (integral F2(x)dx/integral 2xF1(x)dx)-1 was determined in the energy interval 20 2 and xF3 for an isoscalar target are calculated and studied as functions of x at fixed energy and as functions of Q2 at fixed x. Both F2 and xF3 increase at small x and decrease at large x as either the energy of Q2 increases. The changes in the structure functions, hence the distributions in the scaling variables x and y, are attributed to charm production from strange quarks in the sea and the inherent Q2 dependence of the structure functions as predicted by quantum chromodynamics (QCD). Tables o by quantum chromodynamics (QCD). Tables of the structure functions are provided, in addition, momentum fraction distributions of the antiquarks are calculated by several methods and presented in various energy intervals. A comparison is made between the antiquark distributions and x anti s/sub p/(x) as derived from the antineutrino induced dimuon data from the experiment. Systematic effects are discussed throughout and detailed comparisons are made with data from other experiments

35

Higher twist analysis of the nucleon g 1 structure function

Different methods to extract the polarized parton densities from the world polarized DIS data are considered. The higher twist corrections h N (x)/ Q 2 to the spin dependent proton and neutron g 1 structure functions are taken into account and found to be nonnegligible and important in the QCD analysis of the present experimental data. Their role in determining the polarized parton densities in the framework of the different approaches is discussed.

Leader, E.; Sidorev, A. V.; Stamenov, D. B.

2005-01-01

36

International Nuclear Information System (INIS)

The non-singlet part of the nucleon structure functions measured in the Q2 range 0.5 to 50 (GeV/c)2 is compared to leading and next-to-leading order QCD predictions. The possible contributions of higher twist and target mass effects are also evaluated. (orig.)

37

The QCD Analysis of the Structure Functions and Effective Nucleon Mass

On the basis of the target mass corrections to structure functions of deep-inelastic scattering of leptons, we evaluate effective nucleon mass that turns out to be twice $M_{nucl.}$ for deep-inelastic scattering on the nucleus target and equals $M_{nucl.}$ for the hydrogen target.

Sidorov, A. V.

1995-01-01

38

Recent lattice QCD results on nucleon structure

Energy Technology Data Exchange (ETDEWEB)

I review recent developments in lattice calculations of nucleon structure. In particular, I cover the calculations of nucleon matrix elements related to generalized parton distribution functions, structure functions and form factors.

Konstantinos Orginos

2006-06-25

39

Recent lattice QCD results on nucleon structure

Energy Technology Data Exchange (ETDEWEB)

I review recent developments in lattice calculations of nucleon structure. In particular, I cover the calculations of nucleon matrix elements related to generalized parton distribution functions, structure functions and form factors.

Konstantinos Orginos

2006-07-01

40

Pion and nucleon twist -4 structure functions in the limit x->1

Energy Technology Data Exchange (ETDEWEB)

The chi -> 1 behavior of the pion and nucleon structure functions is studied here within the framework of the operator product expansion. The work on the twist-4 structure functions is performed in the longitudinal operator basis, which has the advantage that all the exact information known about the operator matrix elements has been used during the transformation into this basis. The simplicity of the twist-4 operator matrix elements is such that it is possible to arrive at power counting arguments for the chi -> 1 behavior in anlogy with the standard counting rules for the twist-2 structure functions.

Soldate, M. (Stanford Linear Accelerator Center, CA (USA))

1983-08-15

41

Moments of nuclear and nucleon structure functions at low Q^2 and the momentum sum rule

New nuclear structure function data from Jefferson Lab covering the higher x and lower Q^2 regime make it possible to extract the higher order F_2 moments for iron and deuterium at low four-momentum transfer squared Q^2. These moments allow for an experimental investigation of the nuclear momentum sum rule and a direct comparison of the non-singlet nucleon moment with Lattice QCD results.

Niculescu, I.; Arrington, J.; Ent, R.; Keppel, C. E.

2005-01-01

42

Moments of nuclear and nucleon structure functions at low Q2 and the momentum sum rule

International Nuclear Information System (INIS)

New nuclear structure function data from Jefferson Lab covering the higher-x and lower-Q2 regime make it possible to extract the higher-order F2 moments for iron and deuterium at low four-momentum transfer squared Q2. These moments allow for an experimental investigation of the nuclear momentum sum rule and a direct comparison of the nonsinglet nucleon moment with lattice QCD results

43

Gold-plated moments of nucleon structure functions in baryon chiral perturbation theory

We obtain leading- and next-to-leading order predictions of chiral perturbation theory for several prominent moments of nucleon structure functions. These free-parameter free results turn out to be in overall agreement with the available empirical information on nearly all of the considered moments, in the region of low-momentum transfer ($Q^2 < 0.3$ GeV$^2$). Especially surprising is the situation for the spin polarizability $\\delta_{LT}$, which thus far was not reproducibl...

Lensky, Vadim; Alarco?n, Jose Manuel; Pascalutsa, Vladimir

2014-01-01

44

Moments of nuclear and nucleon structure functions at low Q2 and the momentum sum rule

International Nuclear Information System (INIS)

New nuclear structure function data from Jefferson Lab covering the higher x and lower Q2 regime make it possible to extract the higher order F2 moments for iron and deuterium at low four-momentum transfer squared Q2. These moments allow for an experimental investigation of the nuclear momentum sum rule and a direct comparison of the non-singlet nucleon moment with Lattice QCD results

45

Next-to-Leading Order Description of Nucleon Structure Function In Valon Model

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 $Q^{2}$. ...

Arash, Firooz; Khorramia, Ali Naghi

1999-01-01

46

On the relation between nuclear and nucleon Structure Functions and their moments

Calculations of nuclear Structure Functions (SF) F_k^A(x,Q^2) routinely exploit a generalized convolution, involving the SF for nucleons F_k^N and the linking SF f^{PN,A} of a fictitious nucleus, composed of point-particles, with the latter usually expressed in terms of hadronic degrees of freedom. For finite Q^2 the approach seemed to be lacking a solid justification and the same is the case for recently proposed, effective nuclear parton distribution functions (pdf), which exactly reproduce the above-mentioned hadronically computed F_k^A. Many years ago Jaffe and West proved the above convolution in the Plane Wave Impulse Approximation (PWIA) for the nuclear components in the convolution. In the present note we extend the above proof to include classes of nuclear Final State Interactions (FSI). One and the same function appears to relate parton distribution functions (pdf) in nuclei and nucleons, and SF for nuclear targets and for nucleons. That relation is the previously conjectured one,with an entirely di...

Rinat, A S

2006-01-01

47

QCD analysis of the structure function F2 in muon nucleon scattering

International Nuclear Information System (INIS)

A QCD analysis in leading and next to leading order of the structure function F2 measured in deep inelastic muon nucleon scattering is presented. Taking into acount several phenomenological uncertainties, including the gluon description and the charm contribution, fits to the data give values of the QCD scale parameter ?sub(LO) in the range 70-250 MeV. A consistent description of muon scattering and lower Q2 electron scattering requires the presence of higher twist 1/Q2 contributions to the scale breaking which are then determined as a function of x from the data. (orig.)

48

Finite Pressure Corrections to Nucleon Structure Function Inside a Nuclear Medium

Our model calculations performed in the frame of the Relativistic Mean Field (RMF) approach show how important are the modifications of nucleon Structure Function (SF) in Nuclear Matter (NM) above the saturation point. They originated from the conservation of a parton longitudinal momenta - essential in the explanation of the EMC effect at the saturation point of NM. For higher density the finite pressure corrections emerge from the Hugenholtz -van Hove (HH) theorem valid for NM and asks to modify the nucleon SF. The density evolution of the nuclear SF seems to be stronger for higher densities. Here we show that the course of Equation o State (EoS) in our modified Walecka model is very close to that obtained from extensive DBHF calculations with a Bonn A potential. The nuclear compressibility decreases. Our model - a nonlinear extension of nuclear RMF, has no additional parameters.

Ro?ynek, J

2011-01-01

49

A detailed study of the nucleon structure functions in deep inelastic muon scattering in iron

International Nuclear Information System (INIS)

The chi and Q2 dependences of the nucleon structure functions F2sup(N)(chi,Q2) and Rsup(N)(chi,Q2) have been measured in deep inelastic muon scattering from an iron target in the region 0.0422. By comparing data taken at different incident muon energies Rsup(N) was found to be small with an average value of 0.026+-0.037 (stat.)+-0.174 (syst.). The observed deviations from scaling gave the value of the QCD mass scale parameter theta. The fraction of the momentum of the nucleon carried by quarks was found to be (49+-1 stat.+-4 syst.)% at Q2proportional15 GeV2. (orig./HSI)

50

Moments of nucleon structure functions at next-to-leading order in baryon chiral perturbation theory

We obtain leading- and next-to-leading-order predictions of chiral perturbation theory for several prominent moments of nucleon structure functions. These parameter-free results turn out to be in overall agreement with the available empirical information on nearly all of the considered moments, in the region of low momentum transfer (Q2<0.3 GeV2). Especially surprising is the situation for the spin polarizability ?L T, which thus far was not reproducible in chiral perturbation theory for proton and neutron simultaneously. This problem, known as the "?L T puzzle," is not seen in the present calculation.

Lensky, Vadim; Alarcón, Jose Manuel; Pascalutsa, Vladimir

2014-11-01

51

Study of nuclear effects in the determination of nucleon structure functions with heavy targets

International Nuclear Information System (INIS)

Results of the experiment on deep inelastic scattering of 280 GeV muons on deuterium, nitrogen and iron nuclei are presented. The purpose of the measurements was to compare the Bjorken variable dependence of nucleon structure functions obtained in experiments on different nuclei and also Q2-dependence (Q- four-momentum transfer) of structure functions. The results of the experiments do not indicate any Q2-dependence of the Fsub(2)sup(Fe)/Fsub(2)sup(Dsub(2)) and Fsub(2)sup(Nsub(2))Fsub(2)sup(Dsub(2)) ratios. These ratios depend linearly on the parameter x: R=a+bx. The parameters of the linear fit for the iron/deuterium ratio are a=1.16+-0.03, b=-0.56+-0.08; and for the. ni;rogen/deuterium ratio, a=1.10+-0.04, anti b=-0.39+-0.09

52

Nucleon structure functions from dynamical (2+1)-flavor domain wall fermions

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_...

Ohta, Shigemi

2008-01-01

53

Mesons and the nucleon structure

International Nuclear Information System (INIS)

The nucleon light-cone wave function is expanded in terms of two-body meson-(bare baryon) Fock components. We find many interesting and surprising results for the flavour, spin and electromagnetic structure of the nucleon. The model leads to asymmetry of the light sea quarks which has important consequences for elementary Drell-Yan processes. We propose a further possibility to test this concept at HERA through the analysis of the structure of deep inelastic scattering (DIS) events induced by pion-exchange. Momentum and energy distributions of outgoing nucleons as well as rapidity and multiplicity distributions are investigated using Monte Carlo simulations. We investigate also possible consequences of the meson cloud in the nucleon for the production of W and Z bosons in the hadron-hadron collisions. A consistent analysis of deep-inelastic data and the gauge boson production data shows that the concept of virtual mesons in the nucleon is very useful in understanding the charged lepton asymmetry measured by the CDF collaboration at Fermilab. We critically study a possibility to test the d-u asymmetry in the nucleon by the analysis of some asymmetries possible to measure in principle at RHIC. (author)

54

Low $x$ double $ln^2(1/x)$ resummation effects at the sum rules for nucleon structure function $g_1$

We have estimated the contributions to the moments of polarized nucleon structure function $g_1(x,Q^2)$ coming from the region of the very low x ($10^{-5}

Ziaja, B

2001-01-01

55

International Nuclear Information System (INIS)

Results are presented for nucleon structure functions in the range 0.1 2 2. In order to cover this wide range of Q2 the new data from the narrow-band beam BEBC Ne/H2 experiment were combined with Gargamelle (PS) results. The data are consistent with the Callan Gross relation (2xF1/F2 = 0.94 +- 0.09). The moments of the structure functions are compared to QCD predictions including second-order corrections. The value of the scale parameter ? is found to be very sensitive to the low-Q2 data. For Q2 > 1.5 GeV2 one obtains ?sub(anti Manti S) = 0.22 +- 0.04 GeV. An attempt was made to fit a simple higher twist parametrisation and a combination of QCD and higher twist to the moments. From a fit to the structure functions values are obtained of ?sub(LO) = 0.23 +- 0.08 GeV in good agreement with the fit to the moments. (orig.)

56

Nucleon structure using lattice QCD

International Nuclear Information System (INIS)

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.

57

Nucleon structure using lattice QCD

Energy Technology Data Exchange (ETDEWEB)

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.

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

58

International Nuclear Information System (INIS)

Using Gerasimov-Drell-Hearn sum rule it is shown that the neutron polarized structure function reaches the asymptotic value at Q2=2 GeV2. For the proton polarization structure function, it is shown that starting from 1.5 GeV2 its deviation from the asymptotic value does not exceed 15-20%. The integrals over the nucleon polarized structure functions are obtained in the interval of x=0.45-1 on the basis of the available data in the resonance energy region at Q2<3 GeV. 23 refs.; 2 figs

59

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.

Watanabe, Akira; Suzuki, Katsuhiko

2014-06-01

60

Nucleon spin structure II: Spin structure function $g_1^p$ at small $x$

The spin structure function $g_1^p$ of the proton is studied in a two component framework, where the perturbative evolution of parton distributions and nonperturbative vector meson dominance model are used. We predict the $g_1^p$ asymmetric behavior at small $x$ from lower $Q^2$ to higher $Q^2$. We find that the contribution of the large gluon helicity dominates $g_1^p$ at $x>10^{-3}$ but mixed with nonperturbative component which complicates the asymptomatic behavior of $g_1^p$ at $x<10^{-3}$. The results are compatible with the data including the HERA early estimations and COMPASS new results. The predicted strong $Q^2$- and $x$-dependence of $g_1^p$ at $0.01

Zhu, Wei

2015-01-01

61

Composite structure of the nucleon

International Nuclear Information System (INIS)

The nonlinear ?-model with vector mesons introduced as gauge bosons and an interacting chiral quark sector depicts the nucleon as a topological soliton embedded in a chiral condensate. High-energy elastic pp and bar pp scattering data from CERN ISR and SPS Collider appear to provide strong evidence in favor of this nucleon structure. 13 refs., 2 figs

62

International Nuclear Information System (INIS)

There is a need for covariant solutions of bound state equations in order to construct realistic QCD based models of mesons and baryons. Furthermore, we ideally need to know the structure of these bound states in all kinematical regimes, which makes a direct solution in Minkowski space (without any 3-dimensional reductions) desirable. The Bethe-Salpeter equation (BSE) for bound states in scalar theories is reformulated and solved for arbitrary scattering kernels in terms of a generalized spectral representation directly in Minkowski space. This differs from the conventional Euclidean approach, where the BSE can only be solved in ladder approximation after a Wick rotation. An application of covariant Bethe-Salpeter solutions to a quark-diquark model of the nucleon is also briefly discussed. (orig.)

63

Exchange currents and nucleon structure

International Nuclear Information System (INIS)

In this paper the reformulation of the Meson Exchange Currents with explicit reference to the internal nucleon structure is illustrated and compared to the conventional approach. The general features of the two-nucleon current are investigated in the framework of both the Constituent Quark Model and the MIT Bag Model, showing that the results are not too much different. The possible advantages of such a microscopic description are also discussed

64

Nonpartonic components in the nucleon structure functions at small Q2 in a broad range of x

International Nuclear Information System (INIS)

We construct a simple two-phase model of the nucleon structure functions valid for both small and large Q2 and in the broad range of Bjorken x. The model incorporates hadron dominance at small x and Q2 and parton model at large Q2. The VDM contribution is modified for small fluctuation times of the hadronic state of the photon. With two free parameters we describe SLAC, CERN NMC, Fermilab E665 and CERN BCDMS data for both proton and deuteron structure functions. Our model explains some phenomenological higher-twist effects extracted from earlier analyses. A good description of the NMC F2p(x)-F2n(x) data is obtained in contrast to other models in the literature. We predict faster vanishing of the partonic component at low Q2 than previously expected and strong Q2 dependence of the Gottfried sum rule below Q2 ? 4 GeV2. (orig.)

65

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.)

66

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

67

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 $x\\to 0$ and $x\\to 1$, 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 Electron-Ion Collider, and at large-$x$ by recent measurements at Jefferson...

Nocera, Emanuele Roberto

2014-01-01

68

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 Electron-Ion Collider, and at large x by recent measurements at Jefferson Lab, also in view of its 12 GeV upgrade.

Nocera, E. R.

2015-03-01

69

Structure functions are a measure of the partonic structure of hadrons, which is important for any process which involves colliding hadrons. They are a key ingredient for deriving partons distributions in nucleons. In recent years dramatic progress has been made in the understanding of the nucleon structure and the precision of its partonic content, due to vast theoretical progress, and the availability of new high precision measurements. This review gives an overview on present structure function and related data, and on the most recent techniques used to extract parton distribution functions to describe the structure of the proton. Special attention is given to the determination of the uncertainties on the parton distributions.

De Roeck, A

2011-01-01

70

Measurement of the nucleon structure functions F2 and R in deep inelastic muon scattering

International Nuclear Information System (INIS)

An analysis of the structure functions F2 and R from data taken by the New Muon Collaboration in deep inelastic scattering of muons off deuterium and hydrogen targets is presented. Data were collected during 1986-87 and 1989 at the M2 muon beam line of the CERN Super Proton Synchrotron. They cover a range 0.006Bj222, respectively, in the Bjorken scaling variable xBj and the negative 4-momentum transfer squared Q2. The structure functions were extracted by studying the inclusive process ?+N??'+X and measuring the incident and scattered muons. The acceptance of the apparatus was taken into account via Monte Carlo simulations. The measured differential cross-section was corrected for higher order electroweak processes on a statistical basis. A preliminary measurement of the structure function R, the ration of the longitudinally and transversely polarised virtual photon absorption cross-sections, is presented. This measurement is the most accurate result on R for both the deuteron and proton at low xBj (down to xBj=0.006). It is compatible with other measurements and with predictions of quantum chromodynamics. A rise of R with decreasing xBj is observed. A Complementary set-up of two sets of liquid deuterium and hydrogen targets, and a dedicated small angle trigger, allowed an accurate determination of the ratio of the deu determination of the ratio of the deuteron and proton structure functions down to xBj=0.0008. The ratio is always smaller than unity, which at low xBj indicates shadowing effects in the deuteron. The determination of the structure function ratio at four different incident muon energies permitted an evaluation of the difference of the structure functions R for the deuteron and proto, which was found to be consistent with zero. New experimental information induced a re-evaluation of the Gottfried sum, which still violates the Gottfried sum rule. 79 refs

71

Nucleon Transverse Structure at COMPASS

COMPASS is a fixed target experiment at CERN. Part of its physics programme is dedicated to study the transverse spin and the transverse momentum structure of the nucleon using SIDIS. For these measurements, data have been collected using transversely polarised proton and deuteron targets. A selection of recent measurements of azimuthal asymmetries using data collected with transversely polarised protons is presented.

Makke, Nour

2014-01-01

72

International Nuclear Information System (INIS)

The spin and flavor structure of quarks and gluons in nucleons and nuclei is more complicated than expected in the original naive quark model. Recent results which show some of the key failures of the naive picture are summarized here with emphasis on recent results from the HERMES experiment. Some future options to study the quarks structure in exclusive processes in electroproduction, photoproduction and pp annihilation are presented. (orig.)

73

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

74

Energy Technology Data Exchange (ETDEWEB)

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{approx}2.4 GeV with four-momentum transfers Q{sup 2} ranging from 0.2 to 5(GeV/c){sup 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 Q{sup 2} 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 F{sub 2} structure function and its moments. Using an OPE-based twist expansion, we studied the Q{sup 2}-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 F{sub 2} 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.

Osipenko, M., E-mail: osipenko@ge.infn.i [INFN, Sezione di Genova, 16146 Genova (Italy); Skobeltsyn Nuclear Physics Institute, Skobeltsyn Nuclear Physics Institute, 119899 Moscow (Russian Federation); Ricco, G. [INFN, Sezione di Genova, 16146 Genova (Italy); Simula, S. [INFN, Sezione di ROMA III, 00146 Rome (Italy); Ripani, M.; Taiuti, M. [INFN, Sezione di Genova, 16146 Genova (Italy); Adhikari, K.P.; Amaryan, M.J. [Old Dominion University, Norfolk, VA 23529 (United States); Anghinolfi, M. [INFN, Sezione di Genova, 16146 Genova (Italy); Avakian, H. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); INFN, Laboratori Nazionali di Frascati, 00044 Frascati (Italy); Baghdasaryan, H. [University of Virginia, Charlottesville, VA 22901 (United States); Battaglieri, M. [INFN, Sezione di Genova, 16146 Genova (Italy); Batourine, V. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Bedlinskiy, I. [Institute of Theoretical and Experimental Physics, Moscow 117259 (Russian Federation); Biselli, A.S. [Fairfield University, Fairfield, CT 06824 (United States); Rensselaer Polytechnic Institute, Troy, NY 12180-3590 (United States); Branford, D. [Edinburgh University, Edinburgh EH9 3JZ (United Kingdom); Briscoe, W.J. [The George Washington University, Washington, DC 20052 (United States); Brooks, W.K. [Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile); Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Burkert, V.D. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Careccia, S.L. [Old Dominion University, Norfolk, VA 23529 (United States); Carman, D.S. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States)

2010-11-15

75

Experimental results on polarized structure functions in deep inelastic lepton-nucleon scattering

International Nuclear Information System (INIS)

A summary is given of experimental results on spin structure functions of the proton g1p(x,Q2), deuteron g1d(x,Q2), and neutron g1n(x,Q2) as measured in deep inelastic scattering of polarized leptons from a polarized target. All results are consistent with the Bjorken sum rule predictions at the Q2 of each experiment. The data do not support the Ellis-Jaffe sum rule prediction for the proton which implies that the hencity carried by the strange quark may be nonzero and that the net quark helicity is smaller than expected from simple quark models

76

Measurement of the nucleon structure functions F2 in muon-iron interactions at 120, 250 and 280 GeV

International Nuclear Information System (INIS)

A measurement of the nucleon structure function F2 on iron is presented. The data cover a kinematic range of 3.25 2 2 and 0.05 <= x <= 0.65. The data clearly show scaling violation. Fits in ledaing-order QCD have been made and values for the scale breaking parameter ? are given. (orig.)

77

Finite-temperature quantum field theory and structure functions of the nucleon

International Nuclear Information System (INIS)

The deep inelastic scattering of leptons off a proton in the statistical model is considered. The interior of the nucleon is viewed as a thermalized assembly of up and down quarks and gluons. This enables the incorporation of features which are absent in the parton model. These include the presence of identical quarks and gluons in initial and final states and of quantum statistical correlations which have a role to play in the propagation of particles when considering Feynman diagrams containing internal lines in next-to-leading-order calculations. These features are incorporated through the use of Fermi-Dirac and Bose-Einstein distributions for quarks and gluons, respectively. Stimulated emission factors for final-state gluons and Pauli-blocking factors for final-state quarks are incorporated. The propagation of particles through a many-body medium is taken into account by using thermal Feynman rules for propagators and vertices. The statistical model could also be seen as an attempt to describe the interior of the nucleon at a more fundamental level than that attained through the use of arbitrary parton distributions containing many parameters in the parton model. 79 refs., 46 figs., 8 tabs

78

Measurements of the nucleon structure function in the range 0.00222 in deuterium, carbon and calcium

International Nuclear Information System (INIS)

Small angle scattering of 280 GeV positive muons by deuterium, carbon and calcium has been measured at scattering angles down to 2 mrad. The nucleon structure function F2 extracted from deuterium does not show a significant x dependence in the measured range of Q2 and its Q2 dependence is linear in log Q2. For calcium, a depletion of F2 is observed at low x by 30% as compared with the values at x=0.1 where F2(Ca) and F2(D) are not significantly different. This depletion is attributed to shadowing. The carbon structure function exhibits a similar, but less pronounced, x dependence. Such behaviour is observed to be independent of Q2. The data are consistent with those obtained from other charged lepton experiments both a similar and higher values of x and Q2 and considerably extend the range of the measurements down to the low values of x to be measured in forthcoming experiments at HERA. (orig.)

79

Use of leptons to study the internal structure of nucleons

International Nuclear Information System (INIS)

In the light of recent results in leptoproduction experiments, a review of the lepton deep inelastic scattering is given. The nucleon structure functions are introduced in the frame of the Quark Parton Model, their Q2 evolution is described with the formalism of Quantum Chromodynamic (QCD) to the leading order. The last experimental results from high energy muon-nucleon and neutrino-nucleon scattering experiments are reported and compared with the QCD predictions. All the experiments are in fair agreement and show a small but clear scaling violation corresponding to the rise with Q2 of the quark-antiquark sea and gluon contributions to the nucleon structure functions

80

Nucleon structure from stochastic estimators

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.

Bali, Gunnar S; Gläßle, Benjamin; Göckeler, Meinulf; Najjar, Johannes; Rödl, Rudolf; Schäfer, Andreas; Sternbeck, André; Söldner, Wolfgang

2013-01-01

81

Nuclear Structure based on Correlated Realistic Nucleon-Nucleon Potentials

We present a novel scheme for nuclear structure calculations based on realistic nucleon-nucleon potentials. The essential ingredient is the explicit treatment of the dominant interaction-induced correlations by means of the Unitary Correlation Operator Method (UCOM). Short-range central and tensor correlations are imprinted into simple, uncorrelated many-body states through a state-independent unitary transformation. Applying the unitary transformation to the realistic Hamil...

Roth, R.; Neff, T.; Hergert, H.; Feldmeier, H.

2004-01-01

82

Nucleon spin structure at Jefferson Lab

International Nuclear Information System (INIS)

In the past decade an extensive experimental program to measure the spin structure of the nucleon has been carried out in the three halls at Jefferson Lab. Using a longitudinally polarized beam scattering off longitudinally or transversely polarized 3He, NH3 and ND3 targets, the double spin asymmetries A|| and A[perpendicular] were measured, providing data of impressively high precision that gives a better understanding of the structure of the nucleon in the deep inelastic scattering and the valence quarks regions. The virtual photon asymmetries A1,2 and polarized structure functions g1,2 were also extracted for the proton, neutron and deuteron over large kinematic ranges, allowing the extraction of first moments and the testing of sum rules and duality.

83

The quark structure of the nucleons

International Nuclear Information System (INIS)

The suitableness of the non-relativistic potential model for the description of quarks in nucleons is proved and the model extensively presented. Practical applications are some contributions to the nucleon-nucleon interaction which result from the quark structure of the nucleons. These are especially the quark-gluon exchange and the quark-pion exchange between nucleons. The influences of these interactions on the s and p scattering of the nucleons are calculated in the framework of the resonating-group method. Furthermore we study the change of the quark structure if two nucleons approach very closely. The interaction of the nucleons by quark-gluon exchange causes an increase of the nucleon radius and a shift of the quark momenta to lower values. On this base the momentum distribution of quarks in nuclei is calculated and a natural explanation of the EMC effect is given. The distance distribution of nucleons and their Fermi motion are calculated for this in the shell model. Then we make further considerations in connection with the flavor symmetry, the collapse of the nucleons and the properties of six-quark bags. Altogether it is shown that in the potential model the most different effects of the quark structure of nucleons can be surprisingly well described in an illustrative way. (orig.)

84

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.

Nasseripour, R; Ambrozewicz, P; Carman, D S; Amaryan, M J; Anciant, E; Anghinolfi, M; Asavapibhop, B; Asryan, G; Audit, G; Auger, T; Avakian, H; Bagdasaryan, H; Baillie, N; Ball, J P; Baltzell, N A; Barrow, S; Battaglieri, M; Beard, K; Bedlinskiy, I; Bektasoglu, M; Bellis, M; Benmouna, N; Berman, B L; Biselli, A S; Blaszczyk, L; Bonner, B E; Bouchigny, S; Boiarinov, S; Bradford, R; Branford, D; Briscoe, W J; Brooks, W K; Burkert, V D; Butuceanu, C; Calarco, J R; Careccia, S L; Casey, L; Cetina, C; Chen, S; Cheng, L; Cole, P L; Collins, P; Coltharp, P; Cords, D; Corvisiero, P; Crabb, D; Credé, V; Dale, D; Dashyan, N; De Masi, R; De Vita, R; De Sanctis, E; Degtyarenko, P V; Dennis, L; Deur, A; Dhuga, K S; Dickson, R; Djalali, C; Dodge, G E; Doughty, D; Dragovitsch, P; Dugger, M; Dytman, S; Dzyubak, O P; Egiyan, H; Egiyan, K S; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fatemi, R; Fedotov, G; Feldman, G; Feuerbach, R J; Forest, T A; Fradi, A; Funsten, H; Garçon, M; Gavalian, G; Gevorgyan, N; Gilfoyle, G P; Giovanetti, K L; Girard, P; Girod, F X; Goetz, J T; Gothe, R W; Griffioen, K A; Guidal, M; Guillo, M; Guler, N; Guo, L; Gyurjyan, V; Hafidi, K; Hakobyan, H; Hanretty, C; Hardie, J; Heddle, D; Hersman, F W; Hicks, K; Hleiqawi, I; Holtrop, M; Hu, J; Hyde-Wright, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Isupov, E L; Ito, M M; Jenkins, D; Jo, H S; Johnstone, J R; Joo, K; Jüngst, H G; Kalantarians, N; Kellie, J D; Khandaker, M; Kim, K Y; Kim, K; Kim, W; Klein, A; Klein, F J; Kossov, M; Krahn, Z; Kramer, L H; Kubarovski, V; Kühn, J; Kuhn, S E; Kuleshov, S V; Kuznetsov, V; Lachniet, J; Laget, J M; Langheinrich, J; Lawrence, D; Livingston, K; Lu, H Y; Lukashin, K; MacCormick, M; Manak, J J; Markov, N; Mattione, P; McAleer, S; McKinnon, B; McNabb, J W C; Mecking, B A; Mestayer, M D; Meyer, C A; Mibe, T; Mikhailov, K; Minehart, R; Mirazita, M; Miskimen, R; Mokeev, V; Moreno, B; Moriya, K; Morrow, S A; Moteabbed, M; Müller, J; Munevar, E; Mutchler, G S; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Niculescu, I; Niczyporuk, B B; Niroula, M R; Niyazov, R A; Nozar, M; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Paterson, C; Anefalos Pereira, S; Peterson, G; Philips, S A; Pierce, J; Pivnyuk, N; Pocanic, D; Pogorelko, O; Pozdniakov, S; Preedom, B M; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Qin, L M; Riccardi, G; Ricco, G; Ripani, M; Ritchie, B G; Rosner, G; Rossi, P; Rubin, P D; Sabati, F; Salamanca, J; Salgado, C; Santoro, J P; Sapunenko, V; Sayre, D; Schumacher, R A; Serov, V S; Shafi, A; Sharabyan, Yu G; Sharov, D; Shvedunov, N V; Simionatto, S; Skabelin, A V; Smith, E S; Smith, L C; Sober, D I; Sokhan, D; Stavinsky, A; Stepanyan, S S; Stepanyan, S; Stokes, B E; Stoler, P; Strakovsky, I I; Strauch, S; Taiuti, M; Taylor, S; Tedeschi, D J; Thoma, U; Thompson, R; Tkabladze, A; Tkachenko, S; Ungaro, M; Vineyard, M F; Vlassov, A V; Wang, K; Watts, D P; Weinstein, L B; Weygand, D P; Williams, M; Wolin, E; Wood, M H; Yegneswaran, A; Yun, J; Zana, L; Zhang, J; Zhao, B; Zhao, Z W

2008-01-01

85

Sea contributions and nucleon structure

International Nuclear Information System (INIS)

We suggest a general formalism to treat a baryon as a composite system of three quarks and a ''sea.'' In this formalism, the sea is a cluster which can consist of gluons and quark-antiquark pairs. The hadron wave function with a sea component is given. The magnetic moments, related sum rules, and axial vector weak coupling constants are obtained. The data seem to favor a vector sea rather than a scalar sea. The quark spin distributions in the nucleon are also discussed

86

The Spin Structure of the Nucleon

This article reviews our present understanding of QCD spin physics: the proton spin puzzle and new developments aimed at understanding the transverse structure of the nucleon. We discuss present experimental investigations of the nucleon's internal spin structure, the theoretical interpretation of the different measurements and the open questions and challenges for future investigation.

Aidala, Christine A; Hasch, Delia; Mallot, Gerhard K

2013-01-01

87

New Results on Nucleon Spin Structure

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, $A_1^n$, in the high-$x$ region are discussed. The new data shows that $A_1^n$ becomes positive at high $x$. They provide crucial input for the global fits to world data to extract polarized parton distribution functions. 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 $g_2^n$ structure function to study higher-twist effects are presented. The data show a clear deviation from the lead-twist contribution. The second moment of the spin structure functions and the twist-3 matrix element $d_2^n$ results wer...

Chen, J

2005-01-01

88

COMPASS results on the nucleon spin structure

International Nuclear Information System (INIS)

A review of the COMPASS results on the longitudinal and transverse spin structure of nucleon is presented. The gluon contribution to the spin of nucleon, measured by several methods, is found to be small. The solid evidence for Sivers and Collins asymmetries is observed.

89

Studies of nucleon spin structure at HERMES

International Nuclear Information System (INIS)

The HERMES experiment studies the spin structure of the nucleon using polarized semi-inclusive deep-inelastic positron scattering and polarized quasi-real photoproduction. Previous analyses of nucleon spin structure combine inclusive deep-inelastic scattering data and measured hyperon decay constants assuming SU(3)flavor symmetry; asymmetries in the processes studied at HERMES may constrain nucleon spin structure more directly. Results are discussed for quark polarizations extracted from semi-inclusive deep-inelastic scattering asymmetries, for gluon polarization extracted from the asymmetry of high-pT hadron pairs, and for the first observation of single-spin azimuthal asymmetries in pion production

90

Covariant soliton dynamics: Structure of the nucleon

International Nuclear Information System (INIS)

We present a model of nucleon structure that is fully covariant. We begin with a Lagrangian that describes quarks coupled to various mesonic fields (sigma,?,rho,?) and an additional field, chi, which is required to bind the quarks into a nucleon. The couplings of the sigma, ?, rho, and ? fields to the quarks are fixed so as to reproduce the empirically determined coupling of these mesons to the nucleon. The latter couplings are taken from fits to nucleon-nucleon scattering data made using one-boson-exchange models. Therefore the free parameters of the model are the mass and coupling constant of the chi field and the quark mass, m/sub q/. In order to simplify the problem, the nucleon is assumed to virtually decay into a quark and a diquark. Equations which specify this amplitude are found by using the equations for the quark and meson field operators obtained from our Lagrangian. The equations which we solve are fully covariant and nonlinear and are solved by iteration. In this model the quark dynamics is governed by the mesonic fields whose source is the nucleon itself. The amplitudes for the emission of these fields by the nucleon depend upon the (nucleon)?(quark + diquark) amplitudes whose structures we are attempting to determine. This model therefore requires a self-consistent solution and leads to the nonlinear equations noted above. At this point we have not calculated mesonic corrections to the nucleon observables such as the magnetic moments, form factoras the magnetic moments, form factors, and g/sub A/, although we have included the effects of all the mesonic fields in the calculation of the nucleon mass

91

International Nuclear Information System (INIS)

Scaling violations in the nucleon structure function F2(x, Q2) measured with high statistics in deep inelastic scattering of muons on a carbon target are compared to predictions of perturbative QCD. Excellent agreement is observed with numerical solutions of the Altarelli-Parisi evolution equations over entire x and Q2 range of the data. In a next-to-leading order nonsinglet approximation, the QCD mass scale parameter ?MS is determined to be 230 ± 20 (stat.) ± 60 (syst.) MeV. A singlet fit to the data favours a soft gluon distribution

92

Determination of the nucleon structure using the weak neutral current

International Nuclear Information System (INIS)

An experimental determination of the neutral current structure functions of the nucleon is obtained by measuring the ratio of the neutral current x distribution to the charged current x distribution. The analysis is based on deep inelastic neutrino nucleon scattering data gathered in a massive fine-grained neutrino detector exposed to a narrow band neutrino beam at Fermilab. 12 refs., 2 figs., 2 tabs

93

International Nuclear Information System (INIS)

Various aspects of nuclear physics at intermediate energies, in connection with the description of the nucleon-nucleon potential in terms of mesons, are presented in this thesis. The meson exchange current contribution is studied in the case of the deuteron (np capture and electrodisintegration near threshold). A consistent description of these processes is discussed, with particular emphasis on the effective range of the current, for momentum transfers as large as q2?1 (GeV/c)2. The structure of finite nuclei and nuclear matter is then analysed in the framework of a relativistic formalism, in which the negative energy component of the nucleon wave function is explicitly taken into account. The nuclear matter saturation mechanism is studied in details and compared with the non-relativistic limit. Properties of finite nuclei are also discussed. Finally, the structure of the nucleon itself in the nuclear medium is investigated. A connection between the polarisation of the nucleon (three valence quark component), the incompressibility parameter and the mass of the first monopole excitation of the nucleon is presented

94

Energy Technology Data Exchange (ETDEWEB)

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.

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

95

International Nuclear Information System (INIS)

The perturbative QCD is applied to calculation of nuclear shadowing correction to the deuterium structure function F2D(x) at x ? 1. This correction is shown to be numerically large. It is emphasized that the neglect of nuclear shadowing leads to underestimating of the neutron structure function F2n(x) and, as a result, to gross overestimating of the Gottfried integral ?01[F2p(x)-F2n(x)]dx/x. (orig.)

96

Nucleon spin structure at low momentum transfers

The generalized Gerasimov-Drell-Hearn (GDH) sum rule is known to be very sensitive to QCD radiative and power corrections. We improve the previously developed QCD-inspired model for the $Q^2$-dependence of the GDH sum rule. We take into account higher order radiative and higher twist power corrections extracted from precise Jefferson Lab data on the lowest moment of the spin-dependent proton structure function $\\Gamma_1^{p}(Q^2)$ and on the Bjorken sum rule $\\Gamma_1^{p-n}(Q^2)$. By using the singularity-free analytic perturbation theory we demonstrate that the matching point between chiral-like positive-$Q^2$ expansion and QCD operator product $1/Q^2$-expansion for the nucleon spin sum rules can be shifted down to rather low $Q\\simeq\\Lambda_{QCD}$ leading to a good description of recent proton, neutron, deuteron and Bjorken sum rule data at all accessible $Q^2$.

Pasechnik, Roman; Teryaev, Oleg

2010-01-01

97

Nucleon spin structure at low momentum transfers

The generalized Gerasimov-Drell-Hearn sum rule is known to be very sensitive to QCD radiative and power corrections. We improve the previously developed QCD-inspired model for the Q2 dependence of the Gerasimov-Drell-Hearn sum rule. We take into account higher order radiative and higher-twist power corrections extracted from precise Jefferson Lab data on the lowest moment of the spin-dependent proton structure function ?1p(Q2) and on the Bjorken sum rule ?1p-n(Q2). By using the singularity-free analytic perturbation theory we demonstrate that the matching point between chiral-like positive-Q2 expansion and QCD operator product 1/Q2 expansion for the nucleon spin sum rules can be shifted down to rather low Q??QCD leading to a good description of recent proton, neutron, deuteron, and Bjorken sum rule data at all accessible Q2.

Pasechnik, Roman S.; Soffer, Jacques; Teryaev, Oleg V.

2010-10-01

98

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

99

Meson-cloud effects in the electromagnetic nucleon structure

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.

Kupelwieser, Daniel

2013-01-01

100

The role of color neutrality in nuclear physics modifications of nucleonic wave functions

The influence of the nuclear medium upon the internal structure of a composite nucleon is examined. The interaction with the medium is assumed to depend on the relative distances between the quarks in the nucleon consistent with the notion of color neutrality, and to be proportional to the nucleon density. In the resulting description the nucleon in matter is a superposition of the ground state (free nucleon) and radial excitations. The effects of the nuclear medium on the electromagnetic and weak nucleon form factors, and the nucleon structure function are computed using a light-front constituent quark model. Further experimental consequences are examined by considering the electromagnetic nuclear response functions. The effects of color neutrality supply small but significant corrections to predictions of observables.

Frank, M R; Miller, G A

1996-01-01

101

Nuclear structure based on correlated realistic nucleon-nucleon potentials

Energy Technology Data Exchange (ETDEWEB)

We present a novel scheme for nuclear structure calculations based on realistic nucleon-nucleon potentials. The essential ingredient is the explicit treatment of the dominant interaction-induced correlations by means of the unitary correlation operator method (UCOM). Short-range central and tensor correlations are imprinted into simple, uncorrelated many-body states through a state-independent unitary transformation. Applying the unitary transformation to the realistic Hamiltonian leads to a correlated, low-momentum interaction, which is well suited for all kinds of many-body models, e.g., Hartree-Fock or shell-model. We employ the correlated interaction, supplemented by a phenomenological correction, in the framework of variational calculations with antisymmetrised Gaussian trial states (fermionic molecular dynamics). Ground state properties of nuclei up to mass numbers A-bar 60 are discussed. Binding energies, charge radii, and charge distributions are in good agreement with experimental data. We perform angular momentum projections of the intrinsically deformed variational states (projection after variation) to extract rotational spectra. Finally, we discuss perspectives for variation after projection and multi-configuration calculations.

Roth, R. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany)]. E-mail: robert.roth@physik.tu-darmstadt.de; Neff, T. [Gesellschaft fuer Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany); Hergert, H. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Feldmeier, H. [Gesellschaft fuer Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany)

2004-11-29

102

Probing nuclear structure with nucleons; Sonder la structure nucleaire avec des nucleons

Energy Technology Data Exchange (ETDEWEB)

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)

Bauge, E. [CEA Bruyeres-le-Chatel, Service de Physique Nucl aire, 91 (France)

2007-07-01

103

Nucleon spin structure studies at COMPASS

International Nuclear Information System (INIS)

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 6LiD 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 ?G/G, accessed via asymmetries involving photon-gluon fusion mechanism (PGF). Both open charm production (detecting D0's), as well as production of height pT hadron pairs are used to tag PGF. Preliminary results for ?G/G based on the analysis of 2002 and 2003 data are shown. In addition, improved measurement of the deuteron structure function g1d at small x, as well as studies of transverse distribution functions in the deuteron by measuring Collins and Sivers azimuthal asymmetries, are reported

104

Isospin symmetry breaking nucleon-nucleon potentials and nuclear structure

Modern nucleon-nucleon (NN) potentials, which accurately fit the nucleon-nucleon scattering phase shifts, contain terms which break isospin symmetry. The effects of these symmetry violating terms on the bulk properties of nuclear matter are investigated. The predictions of the charge symmetry breaking (CSB) terms are compared with the Nolen-Schiffer (NS) anomaly regarding the energies of neighboring mirror nuclei. We find that, for a quantitative explanation of the NS anomaly, it is crucial to include CSB in partial waves with $L>0$ (besides $^1S_0$) as derived from a microscopic model for CSB of the NN interaction.

Müther, H; Machleidt, R

1999-01-01

105

Spin Structure of the Nucleon - Status and Recent Results

Energy Technology Data Exchange (ETDEWEB)

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_

Kuhn, Sebastian; Chen, Jian-Ping; Leader, Elliot

2009-07-01

106

Theoretical predictions show that at low values of Bjorken $x$ the spin structure function is influenced by large logarithmic corrections, $ln^2(1/x)$, which may be predominant in this region. These corrections are also partially contained in the NLO part of the standard DGLAP evolution. Here we calculate the non-singlet component of the nucleon structure function, $g_1^{NS}=g_1^p-g_1^n$, and its first moment, using a unified evolution equation. This equation incorporates the terms describing the NLO DGLAP evolution and the terms which contribute to the $ln^2(1/x)$ resummation. In order to avoid double counting in the overlapping regions of the phase-space, a unique way of including the NLO terms into the unified evolution equation is proposed. The scheme-independent results obtained from this unified evolution are compared to the NLO fit to experimental data, GRSV'2000. Analysis of the first moments of $g_1^{NS}$ confirms that the unified evolution including the $ln^2(1/x)$ resummation goes beyond the NLO DG...

Ziaja, B

2002-01-01

107

Two-Nucleon Spectral Function in Infinite Nuclear Matter

The two-nucleon spectral function in nuclear matter is studied using Correlated Basis Function perturbation theory, including central and tensor correlations produceded by a realistic hamiltonian. The factorization property of the two-nucleon momentum distribution into the product of the two single nucleon distributions shows up in an analogous property of the spectral function. The correlated model yields a two-hole contribution quenched whith respect to Fermi gas model, wh...

Benhar, Omar; Fabrocini, Adelchi

1999-01-01

108

Structure and Spin of the Nucleon

Energy Technology Data Exchange (ETDEWEB)

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.

Avakian, Harut A. [JLAB

2014-03-01

109

Nucleon-pion-state contribution to nucleon two-point correlation functions

We study the nucleon-pion-state contribution to the QCD two-point function of the standard nucleon interpolating fields. For sufficiently small quark masses these two-particle states are expected to have a smaller total energy than the single-particle excited states. We calculate the nucleon-pion-state contribution to leading order in chiral perturbation theory. Both parity channels are considered. We find the nucleon-pion-state contribution to be small, contributing at the few percent level to the effective mass in the positive parity channel.

Bar, Oliver

2015-01-01

110

Nucleon longitudinal spin structure at COMPASS

The nucleon spin structure is studied at COMPASS via the measurement of the spin dependent properties of deep inelastic muon-deuteron scattering. Both inclusive and semi-inclusive observables are investigated, with the emphasis put on the latter. This allows to access, in particular, the gluon polarization ($\\Delta G/G$) and the flavor decomposition of the quark helicity distributions. Results from measurements with longitudinal target polarization are presented, as well as ...

Bedfer, Yann

2005-01-01

111

The nucleon spin structure in a simple quark model

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.

Ma, Bo-qiang; Schmidt, Ivan; Yang, Jian-jun

2000-01-01

112

Electromagnetic studies of nucleon and nuclear structure

Energy Technology Data Exchange (ETDEWEB)

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 {sup 12}C and {sup 16}O are reported, as well as work on nuclear structure models and instrumentation development.

Heisenberg, J.H.; Calarco, J.R.; Hersman, F.W.; Dawson, J.F.

1993-06-01

113

The nucleon spectral function in nuclear matter

Energy Technology Data Exchange (ETDEWEB)

A microscopic theory based on orthogonal correlated basis functions is developed for the single-particle spectral function of an infinite Fermi system. The nucleon spectral function P(k,E) has been calculated for a realistic model of nuclear matter in which spin-isospin and tensor correlations are fully taken into account. P(k,E) is analyzed in terms of a single-particle strength, which turns out to be completely determined by two-body breakup processes, and a background which is mainly furnished by three-body breakup processes. The strength of single-particle states close to the Fermi surface can be measured by (e,e'p) reactions in kinematical conditions corresponding to low missing energy E, whereas the background requires a wide range of E values, extended up to several hundreds of MeV. The relations between P(k,E), the momentum distribution and the response function are discussed in connection with the analysis of inclusive (e,e') data at high momentum transfer. (orig.).

Benhar, O. (Istituto Nazionale di Fisica Nucleare, Rome (Italy). Sezione Sanita Istituto Superiore di Sanita, Rome (Italy). Lab. di Fisica); Fabrocini, A. (Pisa Univ. (Italy). Dipt. di Fisica Istituto Nazionale di Fisica Nucleare, Pisa (Italy)); Fantoni, S. (Istituto Nazionale di Fisica Nucleare, Lecce (Italy) Lecce Univ. (Italy). Dipt. di Fisica)

1989-12-11

114

The nucleon spectral function in nuclear matter

A microscopic theory based on orthogonal correlated basis functions is developed for the single-particle spectral function of an infinite Fermi system. The nucleon spectral function P( k, E) has been calculated for a realistic model of nuclear matter in which spin-isospin and tensor correlations are fully taken into account. P( k, E) is analyzed in terms of a single-particle strength, which turns out to be completely determined by two-body breakup processes, and a background which is mainly furnished by three-body breakup processes. The strength of single-particle states close to the Fermi surface can be measured by (e, e'p) reactions in kinematical conditions corresponding to low missing energy E, whereas the background requires a wide range of E values, extended up to several hundreds of MeV. The relations between P( k, E), the momentum distribution and the response function are discussed in connection with the analysis of inclusive (e,e') data at high momentum transfer.

Benhar, Omar; Fabrocini, Adelchi; Fantoni, Stefano

1989-12-01

115

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.)

116

Energy Technology Data Exchange (ETDEWEB)

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.

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

117

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)

118

Nucleon structure study by virtual compton scattering

International Nuclear Information System (INIS)

We propose to study nucleon structure by Virtual Compton Scattering using the reaction p(e,e'p)? with the MAMI facility. We will detect the scattered electron and the recoil proton in coincidence in the high resolution spectrometers of the hall A1. Compton events will be separated from the other channels (principally ?0 production) by missing-mass reconstruction. We plan to investigate this reaction near threshold. Our goal is to measure new electromagnetic observables which generalize the usual magnetic and electric polarizabilities. (authors). 9 refs., 18 figs., 7 tabs

119

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.

120

Nucleon wave function from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

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.)

Warkentin, Nikolaus

2008-04-15

121

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.)

122

International Nuclear Information System (INIS)

I show that the recent precise data on the Nachtmann moments M(n,Q2) from Q2 = 3 to 40 (GeV/c)2 are extremely well represented by straight lines in the variable 1/Q2 indicating M(n,Q2) approx. equal to A0(n) + A1(n)/Q2. The threshold behaviour of the scaling function F2(x) obtained from the above ansatz, is in excellent agreement with the Drell-Yan-West relation. The predictions for M(n,Q2) for values of Q2 larger than about 200 (GeV/c)2 are quite distinct from QCD-expectations. (orig.)

123

Nucleon effective mass effects on the Pauli-blocking function

International Nuclear Information System (INIS)

The effects of nucleon effective mass on the Pauli-blocking function are worked out. We have shown that such effects on the quasi-deuteron mechanism of photonuclear absorption are rather relevant. The pauli-blocking function has been evaluated by applying a Monte Carlo calculation particularly suitable for simulation of intranuclear cascade process of intermediate-energy nuclear reactions. The nucleon binding in the photonuclear absorption mechanism is accordingly taken into account. (author)

124

Nucleon effective mass effects on the Pauli-blocking function

Energy Technology Data Exchange (ETDEWEB)

The effects of nucleon effective mass on the Pauli-blocking function are worked out. We have shown that such effects on the quasi-deuteron mechanism of photonuclear absorption are rather relevant. The pauli-blocking function has been evaluated by applying a Monte Carlo calculation particularly suitable for simulation of intranuclear cascade process of intermediate-energy nuclear reactions. The nucleon binding in the photonuclear absorption mechanism is accordingly taken into account. (author)

Pina, S.R. de; Mesa, J.; Deppman, A.; Arruda-Neto, J.D.T. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Duarte, S.B.; Oliveira, E.C. de; Tavares, O.A.P.; Medeiros, E.L. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Goncalves, M.; Paiva, E. de [Instituto de Radioprotecao e Dosimetria (IRD), Rio de Janeiro, RJ (Brazil)]|[Sociedade Educacional Sao Paulo Apostolo - UniverCidade, Rio de Janeiro, RJ (Brazil)

2002-05-01

125

Disconnected Quark Loop Contributions to Nucleon Structure

We calculate the disconnected contribution to isoscalar nucleon charges for scalar, axial and tensor channels of light and strange quarks. The calculation has been done with the Clover valence quarks on the MILC $N_f=2+1+1$ HISQ lattices whose light quark masses corresponding to the pion masses of 305 MeV and 217 MeV at $a \\approx 0.12$ fm and 312 MeV at $a \\approx 0.09$ fm. All-mode-averaging technique is used for the evaluation two-point functions. Disconnected quark loops are estimated by using the truncated solver method with Gaussian random noise sources. Contamination from the excited states is removed by fitting the results of various source-sink separations and operator insertions to the formula including up to the first excited state, simultaneously.

Bhattacharya, Tanmoy; Yoon, Boram

2015-01-01

126

Structure and spin of the nucleon

Directory of Open Access Journals (Sweden)

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.

Avakian H.

2014-03-01

127

Recent measurements of unpolarised and polarised nucleon structure functions and F_2(gamma) are reviewed. The implications for QCD and the gluon momentum distribution are discussed. The status of the understanding of the total virtual-photon proton total cross-section in the transition region between real photoproduction and deep-inelastic scattering is summarised briefly.

Devenish, Robin

1998-01-01

128

Two-Nucleon Spectral Function in Infinite Nuclear Matter

The two-nucleon spectral function in nuclear matter is studied using Correlated Basis Function perturbation theory, including central and tensor correlations produceded by a realistic hamiltonian. The factorization property of the two-nucleon momentum distribution into the product of the two single nucleon distributions shows up in an analogous property of the spectral function. The correlated model yields a two-hole contribution quenched whith respect to Fermi gas model, while the peaks acquire a quasiparticle width that vanishes as the two momenta approach $k_F$. In addition, three-hole one-particle and more complicated intermediate states give rise to a background, spread out in energy and absent in the uncorrelated models. The possible connections with one- and two-nucleon emission processes are briefly discussed.

Benhar, O; Benhar, Omar; Fabrocini, Adelchi

2000-01-01

129

Two-nucleon spectral function in infinite nuclear matter

The two-nucleon spectral function in nuclear matter is studied using correlated basis function perturbation theory, including central and tensor correlations produced by a realistic Hamiltonian. The factorization property of the two-nucleon momentum distribution into the product of the two single nucleon distributions shows up in an analogous property of the spectral function. The correlated model yields a two-hole contribution quenched with respect to the Fermi gas model, while the peaks acquire a quasiparticle width that vanishes as the two momenta approach the Fermi momentum kF. In addition, three-hole one-particle and more complicated intermediate states give rise to a background, spread out in energy and absent in the uncorrelated models. The possible connections with one- and two-nucleon emission processes are briefly discussed.

Benhar, Omar; Fabrocini, Adelchi

2000-09-01

130

Nucleon Excited State Wave Functions from Lattice QCD

We apply the eigenvectors from a variational analysis to successfully extract the wave functions of even-parity excited states of the nucleon, including the Roper. We explore the first four states in the spectrum excited by the standard nucleon interpolating field. We find that the states exhibit a structure qualitatively consistent with a constituent quark model, where the ground, first-, second- and third-excited states have 0, 1, 2, and 3 nodes in the radial wave function of the d-quark about two $u$ quarks at the origin. Moreover the radial amplitude of the probability distribution is similar to that predicted by constituent quark models. We present a detailed examination of the quark-mass dependence of the probability distributions for these states, searching for a nontrivial role for the multi-particle components mixed in the finite-volume QCD eigenstates. Finally we examine the dependence of the d-quark probability distribution on the positions of the two u quarks. The results are fascinating, with the...

Roberts, Dale S; Leinweber, Derek B

2013-01-01

131

Nucleon Structure and Hyperon Form Factors from Lattice QCD.

Energy Technology Data Exchange (ETDEWEB)

In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point. to be 1.23(5), consistent with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(2G), consistent with the Adelaide-JLab Collaboration's result. The hyperon {Sigma} and {Xi} axial coupling constants are also performed for the first time in a lattice calculation, g{sub {Sigma}{Sigma}} = 0.441(14) and g{sub {Xi}{Xi}} = -0.277(11).

Lin,H.W.

2007-06-11

132

Nucleon spin structure I: A dynamical determination of gluon helicity distribution in the nucleon

Gluon helicity distribution in the nucleon is dynamically predicted by using a nonlinear QCD evolution equation-the DGLAP equation with the parton recombination corrections - starting from a low scale, where the nucleon is almost only consisted of valence quarks. The comparisons of our predicted gluon helicity distribution with the available data are presented. We find that the contribution of the gluon helicity to the nucleon spin structure is much larger than the predictions of most other theories. This result suggests a significant orbital angular momentum of the gluons is required to balance the gluon helicity. A novel spin-orbital structure of the proton in the light-cone frame is described based on the quantitative calculations,and the nucleon spin crisis is discussed.

Zhu, Wei

2015-01-01

133

The Structure of the Nucleon: Elastic Electromagnetic Form Factors

Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon's static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future.

Punjabi, V; Jones, M K; Brash, E J; Carlson, C E

2015-01-01

134

Nucleon structure by Lattice QCD computations with twisted mass fermions

International Nuclear Information System (INIS)

Understanding the structure of the nucleon from quantum chromodynamics (QCD) is one of the greatest challenges of hadronic physics. Only lattice QCD allows to determine numerically the values of the observables from ab-initio principles. This thesis aims to study the nucleon form factors and the first moments of partons distribution functions by using a discretized action with twisted mass fermions. As main advantage, the discretization effects are suppressed at first order in the lattice spacing. In addition, the set of simulations allows a good control of the systematical errors. After reviewing the computation techniques, the results obtained for a wide range of parameters are presented, with lattice spacings varying from 0.0056 fm to 0.089 fm, spatial volumes from 2.1 up to 2.7 fm and several pion masses in the range of 260-470 MeV. The vector renormalization constant was determined in the nucleon sector with improved precision. Concerning the electric charge radius, we found a finite volume effect that provides a key towards an explanation of the chiral dependence of the physical point. The results for the magnetic moment, the axial charge, the magnetic and axial charge radii, the momentum and spin fractions carried by the quarks show no dependence on the lattice spacing nor volume. In our range of pion masses, their values show a deviation from the experimental values. Their chiral behaviour do not exhibit the curvature predicted by the chiral perturbation theory which could explain the apparent discrepancy. (author)

135

Nucleon structure from lattice QCD - recent achievements and perspectives

We present recent developments in lattice QCD simulations as applied in the study of hadron structure. We discuss the challenges and perspectives in the evaluation of benchmark quantities such as the nucleon axial charge and the isovector parton momentum fraction, as well as, in the computation of the nucleon $\\sigma$-terms, which involve the calculation of disconnected quark loop contributions.

Alexandrou, Constantia

2014-01-01

136

Correlated overlap functions and nucleon removal reactions from 16 O

International Nuclear Information System (INIS)

Using the relationship between the one-nucleon overlap functions related to bound states of the (A - 1)-particle system and the one-body density matrix for the ground state of the A-particle system the overlap functions and spectroscopic factors are calculated within different correlation methods, such as: i) the Jastrow correlation method; ii) the Correlated Basis Function Theory; iii) the Green Function Method and, iv) the Generator Coordinate Method. The resulting bound-state overlap functions are used to calculate the cross sections of the (p,d), (e,e'n), (e, e'p) and (?,p) reactions on 16 O. The nucleon-nucleon correlation effects are studied and various correlation methods are tested in the comparison with the experimental data. (authors)

137

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

138

The scaling violations of the structure functions F/sub 2/, xF/sub 3/, and q, as measured in deep-inelastic neutrino-nucleon scattering at high hadron class W, have been compared with the predictions of QCD and other candidate field theories of strong interactions. Non- asymptotically free theories with scalar and vector gluons are incompatible with the data. This leaves QCD as the only field theory that gives a consistent description of all the observed scaling violations. The data do not, however, permit a sensitive test of the existence of the gluon self-coupling.

Abramowicz, H; Duda, J; Dydak, F; Eisele, F; Flottmann, T; Geweniger, C; Guyot, C; He, J T; Klasen, H P; Kleinknecht, K; Knobloch, J; Królikowski, J; May, J; Merlo, J P; Palazzi, P; Para, A; Peyaud, B; Pszola, B; Rander, J; Ranjard, F; Renk, B; Rothberg, J E; Ruan, T Z; Schlatter, W D; Schuller, J P; Steinberger, J; Taureg, H; Tittel, K; Turlay, René; von Rüden, Wolfgang; Wahl, H; Willutzki, H J; Wotschack, J; Wu, W M

1982-01-01

139

International Nuclear Information System (INIS)

The scaling violations of the structure functions F2, xF3, and anti q, as measured in deep-inelastic neutrino-nucleon scattering at high hadron mass W, have been compared with the predictions of QCD and other candidate field theories of strong interactions. Non-asympotically free theories with scalar and vector gluons are incompatible with the data. This leaves QCD as the only field theory that gives a consistent description of all the observed scaling violations. The data do not, however, permit a sensitive test of the existence of the gluon self-coupling. (orig.)

140

Generalized Parton Distributions and the Spin Structure of the Nucleon

Generalized parton distributions are a new type of hadronic observables which has recently stimulated great interest among theorists and experimentalists alike. Introduced to delineate the spin structure of the nucleon, the orbital angular momentum of quarks in particular, the new distributions contain vast information about the internal structure of the nucleon, with the usual electromagnetic form factors and Feynman parton distributions as their special limits. While new p...

Ji, Xiangdong

2002-01-01

141

Probing nucleon strangeness structure with $\\phi$ electroproduction

We study the possibility to constrain the hidden strangeness content of the nucleon by means of the polarization observables in phi meson electroproduction. We consider the OZI evading direct knockout mechanism that arises from the non-vanishing s\\bar{s} sea quark admixture of the nucleon as well as the background of the dominant diffractive and the one-boson-exchange processes. Large sensitivity on the nucleon strangeness are found in several beam-target and beam-recoil double polarization observables. The small \\sqrt{s} and W region, which is accesible at some of the current high-energy electron facilities, is found to be the optimal energy region for extracting out the OZI evasion process.

Oh, Yu; Yang, S N; Mori, T; Oh, Yongseok; Titov, Alexander I.; Yang, Shin Nan; Morii, Toshiyuki

1999-01-01

142

Spin-Isospin Structure and Pion Condensation in Nucleon Matter

We report variational calculations of symmetric nuclear matter and pure neutron matter, using the new Argonne v18 two-nucleon and Urbana IX three-nucleon interactions. At the equilibrium density of 0.16 fm^-3 the two-nucleon densities in symmetric nuclear matter are found to exhibit a short-range spin-isospin structure similar to that found in light nuclei. We also find that both symmetric nuclear matter and pure neutron matter undergo transitions to phases with pion condens...

Akmal, Arya; Pandharipande, Vijay R.

1997-01-01

143

Neutrino-nucleon scattering, which produces the parity violating term, xF3(x,Q2) the non-singlet hadron structure function in their weak interaction has significant contribution towards the understanding of valence quark distribution for low-Q2 and small-x region inside hadrons. Here x is the fractional momentum of partons and Q2 is the four momentum transfer in a deep inelastic scattering process. In this paper, the xF3(x,Q2) structure function has been obtained by solving the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equation in leading order and next-to-leading order at small-x limit by using the method to get unique solution. The results are compared with recent experimental data and parametrizations. Also a qualitative discussion of nuclear effect in xF3(x,Q2) is done in this regards.

Nath, N M; Sarma, J K

2011-01-01

144

Study of excited nucleons and their structure

International Nuclear Information System (INIS)

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

145

The nucleon spectral function in infinite nuclear matter

A perturbadve calculation of the nucleon spectral function in infinite nuclear matter has been carried out using a complete set of orthonormal correlated states. Correlation effects, giving rise to a quenching of the single particle strengths and to a sizeable background contribution are discussed.

Benhar, Omar; Fabrocini, Adelchi; Fantoni, Stefano

1989-06-01

146

The nucleon spectral function in infinite nuclear matter

Energy Technology Data Exchange (ETDEWEB)

A perturbative calculation of the nucleon spectral function in infinite nuclear matter has been carried out using a complete set of orthonormal correlated states. Correlation effects, giving rise to a quenching of the single particle strengths and to a sizeable background contribution are discussed. (orig.).

Benhar, O. (Istituto Nazionale di Fisica Nucleare, Rome (Italy). Ist. Superiore di Sanita); Fabrocini, A. (Pisa Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Pisa (Italy)); Fantoni, S. (Lecce Univ. (Italy). Dipt. di Fisica; Istituto Nazionale di Fisica Nucleare, Lecce (Italy))

1989-06-26

147

International Nuclear Information System (INIS)

This report covers many aspects and some of the singular events which occurred over a two year period (November 1975-November 1977) in the field of nucleonics. Tables (I-IV) include listings of new books, reviews, bibliographies, and conference proceedings. Table III, (the list of conference proceedings) is not as complete as the authors had wished because of the often-experienced long delay time between oral presentation and proceedings publication; therefore, some of the publication dates were not available. By referring to these tables, however, one can find information on almost any facet of nucleonics. According to the authors, their brief written summary emphasizes only the new, interesting, or occasionally, the peculiar aspects of the subject. Discussed are developments in radiation detectors, radiotracer techniques, nuclear archeology, growth in application of activation analysis, decay rate perturbations, and environmental concerns. 213 references

148

International Nuclear Information System (INIS)

A review of nucleonics indicates that other techniques in the analytical field, e.g. inductively coupled lasers, variations on the mass spec theme such as resonance ionization mass spectrometry, continue to push nuclear techniques aside and to claim analyses that were once the exclusive province of nuclear activation analysis. However, some persons continue to persevere in the face of much adversity in the nuclear analytical techniques. In this review, the new aspects of nucleonics and the books, data compilation, and conference proceedings are discussed. Here less emphasis has been placed on the source of information (highlighted in previous reviews) than on the information itself. Table entries have been limited to items that are of most interest to analytical chemist; and in the body of the text at least one or two innovative or potentially useful new techniques are described a bit more in detail

149

Polarized Parton Distribution Functions in the Nucleon

Polarized parton distribution functions are determined by using world data from the longitudinally polarized deep inelastic scattering experiments. A new parametrization of the parton distribution functions is adopted by taking into account the positivity and the counting rule. From the fit to the asymmetry data A_1, the polarized distribution functions of u and d valence quarks, sea quarks, and gluon are obtained. The results indicate that the quark spin content is \\Delta\\Sigma=0.20 and 0.05 in the leading order (LO) and the next-to-leading-order (NLO) MS-bar scheme, respectively. However, if x dependence of the sea-quark distribution is fixed at small x by "perturbative QCD" and Regge theory, it becomes \\Delta \\Sigma=0.24 ~ 0.28 in the NLO. The small-x behavior cannot be uniquely determined by the existing data, which indicates the importance of future experiments. From our analysis, we propose one set of LO distributions and two sets of NLO ones as the longitudinally-polarized parton distribution functions...

Goto, Y; Hirai, M; Horikawa, H; Kumano, S; Miyama, M; Mori, T; Saitô, N; Shibata, T A; Taniguchi, E; Yamanishi, T

2000-01-01

150

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.)

151

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

152

Experimental study of the nucleon spin structure

Energy Technology Data Exchange (ETDEWEB)

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.).

Litmaath, M.F.

1996-05-07

153

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.)

154

The spin structure of the nucleon

Energy Technology Data Exchange (ETDEWEB)

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.)

Le Goff, J.M

2005-02-15

155

Study of nucleon spin structure by using transversely polarized nucleon targets at HERMES experiment

International Nuclear Information System (INIS)

In this paper, the nucleon spin structure studies made by using transversely' polarized nucleon target at DESY in Hamburg, Germany is reported. Asymmetry of hadron generation, which is called Sivers, Collins asymmetry, was successfully separated for the first time in the world. At the HERMES experiment, deep inelastic scattering was measured using the 27.5 GeV positron beam and transversely polarized hydrogen target, to obtain the degree of asymmetry for the generation of ?+, ?- and ?0. The results are summarized as follows. Sivers asymmetry; ?+: positive value with 3? statistical accuracy, ?0: positive value with 2? statistical accuracy, and ?-: zero within statistical error. Collins asymmetry; ?-: negative value with 3? statistical accuracy, ?+: positive value with 2? statistical accuracy, and ?0: zero within statistical error. The paper [A.Airapetian et al., HERMES, Phys.Rev.Lett. 94('05)012002] is recommended to be referred to. (S. Funahashi)

156

Delineating the polarized and unpolarized partonic structure of the nucleon

Reports on our latest extractions of parton distribution functions of the nucleon are given. 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 reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.

Jimenez-Delgado, Pedro

2014-01-01

157

Delineating the Polarized and Unpolarized Partonic Structure of the Nucleon

Reports on our latest extractions of parton distribution functions of the nucleon are given. 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 reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.

Jimenez-Delgado, Pedro

2015-02-01

158

Delineating the polarized and unpolarized partonic structure of the nucleon

Energy Technology Data Exchange (ETDEWEB)

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.

Jimenez-Delgado, Pedro [JLAB

2015-03-01

159

Advanced nucleon electromagnetic structure model and charge proton rms radius

Energy Technology Data Exchange (ETDEWEB)

Description of the nucleon electromagnetic structure by advanced Unitary and Analytic approach, respecting SU(3) symmetry and analyzing also the recent Mainz MAMI data with impact on the proton charge radius to be compared with the results from the muon hydrogen atom spectroscopy.

Adamuš?ín, C.; Bartoš, E.; Dubni?ka, S. [Institute of Physics, Slovak Academy of Sciences, Bratislava (Slovakia); Dubni?ková, A.Z. [FMPI Comenius University, Mlynská dolina, 84248 Bratislava (Slovakia)

2013-12-15

160

The largest polarized target for nucleon spin structure study

International Nuclear Information System (INIS)

One of the goals of the COMPASS experiment at CERN is to investigate the spin structure of a nucleon, which needs a highly polarized nucleon target with a considerable thickness along with a highly polarized muon beam. The largest ever polarized solid target containing 1 liter of the target material has been constructured for COMPASS, and the Dynamic Nuclear Polarization technique has been applied to realize the highest polarization of a proton and a deuteron at the temperature of 50 mK and in the magnetic field of 2.5 T. The techniques and the advantages of the COMPASS target are described in this report. (author)

161

pp Elastic Scattering at LHC and Nucleon Structure

International Nuclear Information System (INIS)

High energy elastic pp differential cross section at LHC at the c.m. energy 14 TeV is predicted using the asymptotic behavior of ?tot(s) and ?(s), and the measured p-barp differential cross section at ?(s) =546 GeV. The phenomenological investigation has progressively led to an effective field theory model that describes the nucleon as a chiral bag embedded in a quark-antiquark condensed ground state. The measurement of pp elastic scattering at LHC up to large vertical bar t vertical bar > or approx. 10 GeV2 by the TOTEM group will be crucial to test this structure of the nucleon

162

The pretzelosity distribution function and intrinsic motion of the constituents in nucleon

The pretzelosity distribution function $h_{1T}^\\perp$ is studied in a covariant the quark-parton model which describes the structure of the nucleon in terms of 3D quark intrinsic motion. This relativistic model framework supports the relation between helicity, transversity and pretzelosity observed in other relativistic models {\\sl without} assuming SU(6) spin-flavor symmetry. Numerical results and predictions for SIDIS experiments are presented.

Efremov, A. V.; Schweitzer, P.; Teryaev, O. V.; Zavada, P.

2008-01-01

163

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

164

Nucleon structure in a light-front quark model consistent with quark counting rules and data

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.

Gutsche, Thomas; Schmidt, Ivan; Vega, Alfredo

2014-01-01

165

Nuclear energy density functional from chiral pion-nucleon dynamics

International Nuclear Information System (INIS)

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?-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*(?) is identical to the one of Fermi-liquid theory. The strength F?(?) of the (vector ??)2 surface-term as provided by the pion-exchange dynamics is in good agreement with that of phenomenological Skyrme forces in the density region ?0/2 0. 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 squared spin-orbit density vector J2 is also studied.

166

Nucleon Polarizabilities from Deuteron Compton Scattering within a Green's-Function Hybrid Approach

We examine elastic Compton scattering from the deuteron for photon energies ranging from zero to 100 MeV, using state-of-the-art deuteron wave functions and NN-potentials. Nucleon-nucleon rescattering between emission and absorption of the two photons is treated by Green's functions in order to ensure gauge invariance and the correct Thomson limit. With this Green's-function hybrid approach, we fulfill the low-energy theorem of deuteron Compton scattering and there is no significant dependence on the deuteron wave function used. Concerning the nucleon structure, we use Chiral Effective Field Theory with explicit \\Delta(1232) degrees of freedom within the Small Scale Expansion up to leading-one-loop order. Agreement with available data is good at all energies. Our 2-parameter fit to all elastic $\\gamma d$ data leads to values for the static isoscalar dipole polarizabilities which are in excellent agreement with the isoscalar Baldin sum rule. Taking this value as additional input, we find \\alpha_E^s= (11.3+-0.7...

Hildebrandt, R P; Hemmert, T R; Griesshammer, Harald W.; Hemmert, Thomas R.; Hildebrandt, Robert P.

2005-01-01

167

Studies of the three-nucleon system properties using the interpolating amplitude scattering function

International Nuclear Information System (INIS)

The three-nucleon motion problem is formulated and investigated using the interpolating function method. The pole functions corresponding to the bound state of the three-nucleon system and the low energy functions interpolating the nd-scattering length are calculated for a separable potential

168

Chiral Corrections to Nucleon Two- and Three-Point Correlation Functions

We consider multi-particle contributions to nucleon two- and three-point functions from the perspective of chiral dynamics. Lattice nucleon interpolating operators, which have definite chiral transformation properties, can be mapped into chiral perturbation theory. Using the most common of such operators, we determine pion-nucleon and pion-delta couplings to nucleon two- and three-point correlation functions at leading order in the low-energy expansion. The couplings of pions to nucleons and deltas in two-point functions are consistent with simple phase-space considerations, in accordance with the Lehmann spectral representation. An argument based on available phase space on a torus is utilized to derive the scaling of multiple-pion couplings. While multi-pion states are indeed suppressed, this suppression scales differently with particle number compared to that in infinite volume. For nucleon three-point correlation functions, we investigate the axial-vector current at vanishing momentum transfer. The effect...

Tiburzi, Brian C

2015-01-01

169

Electromagnetic properties of light nuclei and nucleon structure

International Nuclear Information System (INIS)

The influence of nucleon structure in the e.m. interactions of light nuclei is pointed out. After a discussion of the particular role played by quark degrees of freedom in the high q/sup 2/-behaviour of form factors (scaling, EMC effect, ...), a constituent quark model for the nucleon spectrum and e.m. properties is discussed. Such a model is used for the calculation of effective two-body operators, which may provide an alternative way to the treatment of EMC effects. The quark picture is a unified approach leading to some definite theoretical previsions which can be tested in electron-proton scattering and presents some peculiar features like the existence of 3-quark forces which may be of relevant interest both for the NN problem and the /sup 3/He charge form factor

170

Feasibility studies for nucleon structure measurements with PANDA

Directory of Open Access Journals (Sweden)

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.

Atomssa Ermias

2014-01-01

171

Covariant nucleon wave function with S, D, and P-state components

Energy Technology Data Exchange (ETDEWEB)

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.

Franz Gross, G. Ramalho, M. T. Pena

2012-05-01

172

Pion-nucleon interaction in the P11 partial wave and the pion-nucleon vertex function

International Nuclear Information System (INIS)

We have studied pion-nucleon interaction in the P11 channel considering its important role in the absorption and production of the pion by nuclei. Specifically we show that the total P11 t-matrix (or amplitude) can be naturally decomposed into two parts: the direct (and dressed) pole part and the non-pole part. It is then easy to observe that individually these two parts can be large but tend to nearly cancel each other and produce small and negative phase shift values from threshold to Tsub(Lab)sup? approximately 170 MeV and that at higher energies the non-pole term dominates giving positive phase shift values. We then try to find the parametrisation of this partial wave t-matrix within the framework of the Blankenbecler-Sugar reduction. As a biproduct we have obtained the ?NN vertex function (with one nucleon off-mass-shell) and the dressed nucleon propagator

173

Low temperature polarized target for spin structure studies of nucleons at COMPASS

In presented thesis we describe concept of Deep Inelastic Scattering of leptons on nucleons in context of nucleon spin structure studies. Both polarized and unpolarized cases are discussed and concept of Transverse Momentum Dependent Parton Distribution Functions (TMD PDF) is introduced. The possibility of TMDs measurement using Semi-inclusive DIS (SIDIS) is described along with related results from COMPASS experiment. The future Drell-Yan programme at COMPASS is briefly mentioned and its importance is presented on the universality test i.e. change of sign of T-odd TMDs when measured in Drell-Yan and SIDIS. The importance of Polarized Target (PT) for spin structure studies is highlighted and principles of Dynamic Nuclear Polarization (DNP) are given using both Solid effect and spin temperature concept. COMPASS experiment is described in many details with accent given to PT. Finally the thermal equilibrium (TE) calibration procedure is described and carried out for 2010 and 2011 physics runs at COMPASS. The av...

Pesek, Michael

174

Superscaling, scaling functions, and nucleon momentum distributions in nuclei

International Nuclear Information System (INIS)

The scaling functions f(?') and F(y) from the ?'- and y-scaling analyses of inclusive electron scattering from nuclei are explored within the coherent density fluctuation model (CDFM). In addition to the CDFM formulation in which the local density distribution is used, we introduce a new equivalent formulation of the CDFM based on the one-body nucleon momentum distribution (NMD). Special attention is paid to the different ways in which the excitation energy of the residual system is taken into account in y and ?' scaling. Both functions, f(?') and F(y), are calculated using different NMDs and compared with the experimental data for a wide range of nuclei. The good description of the data for y''' and y scaling are informative for NMDs at momenta not larger than 2.0-2.5 fm-1. The CDFM allows us to study simultaneously and on the same footing the role of both basic quantities--the momentum and density distributions--for the description of scaling and superscaling phenomena in nuclei

175

Superscaling, scaling functions, and nucleon momentum distributions in nuclei

The scaling functions f(?') and F(y) from the ?'- and y-scaling analyses of inclusive electron scattering from nuclei are explored within the coherent density fluctuation model (CDFM). In addition to the CDFM formulation in which the local density distribution is used, we introduce a new equivalent formulation of the CDFM based on the one-body nucleon momentum distribution (NMD). Special attention is paid to the different ways in which the excitation energy of the residual system is taken into account in y and ?' scaling. Both functions, f(?') and F(y), are calculated using different NMDs and compared with the experimental data for a wide range of nuclei. The good description of the data for yNMDs in different regions of momenta. It is concluded that the existing data on ?' and y scaling are informative for NMDs at momenta not larger than 2.0 2.5fm-1. The CDFM allows us to study simultaneously and on the same footing the role of both basic quantities—the momentum and density distributions—for the description of scaling and superscaling phenomena in nuclei.

Antonov, A. N.; Gaidarov, M. K.; Ivanov, M. V.; Kadrev, D. N.; Moya de Guerra, E.; Sarriguren, P.; Udias, J. M.

2005-01-01

176

Nucleon electromagnetic structure studies in the spacelike and timelike regions

International Nuclear Information System (INIS)

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+p/e-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+e- 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??0e+e- 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?>?0?.

177

Flavor Structure of the Nucleon Sea from Lattice QCD

We present the first direct lattice calculation of the isovector sea-quark parton distributions using the formalism developed recently by one of the authors. We use $N_f=2+1+1$ HISQ lattice gauge ensembles (generated by MILC Collaboration) and clover valence fermions with pion mass 310 MeV. We are able to obtain the qualitative features of the nucleon sea flavor structure even at this large pion mass: We observe violation of the Gottfried sum rule, indicating $\\overline{d}(x) > \\overline{u}(x)$; the helicity distribution obeys $\\Delta \\overline{u}(x) > \\Delta \\overline{d}(x)$, which is consistent with the STAR data at large and small leptonic pseudorapidity.

Lin, Huey-Wen; Cohen, Saul D; Ji, Xiangdong

2014-01-01

178

Nonequilibrium distribution functions of nucleons in relativistic nucleus-nucleus collisions

Directory of Open Access Journals (Sweden)

Full Text Available The collision smearing of the nucleon momenta about their initial values during relativistic nucleus-nucleus collisions is investigated. To a certain degree, our model belongs to the transport type, and we investigate the evolution of the nucleon system created at a nucleus-nucleus collision. However, 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 functions are derived which depend on a certain number of collisions of a nucleon before a freeze-out.

D. Anchishkin

2013-03-01

179

Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction

Studies of the structure of excited baryons are key to the N* program at Jefferson Lab. Within the first year of data taking with the Hall B CLAS12 detector following the 12 GeV upgrade, a dedicated experiment will aim to extract the N* electrocouplings at high photon virtualities Q2. This experiment will allow exploration of the structure of N* resonances at the highest photon virtualities ever yet achieved, with a kinematic reach up to Q2 = 12 GeV2. This high-Q2 reach will make it possible to probe the excited nucleon structures at distance scales ranging from where effective degrees of freedom, such as constituent quarks, are dominant through the transition to where nearly massless bare-quark degrees of freedom are relevant. In this document, we present a detailed description of the physics that can be addressed through N* structure studies in exclusive meson electroproduction. The discussion includes recent advances in reaction theory for extracting N* electrocouplings from meson electroproduction off pro...

Aznauryan, I G; Braun, V; Brodsky, S J; Burkert, V D; Chang, L; Chen, Ch; El-Bennich, B; Cloët, I C; Cole, P L; Edwards, R G; Fedotov, G V; Giannini, M M; Gothe, R W; Lin, Huey-Wen; Kroll, P; Lee, T -S H; Melnitchouk, W; Mokeev, V I; Peña, M T; Ramalho, G; Roberts, C D; Santopinto, E; de Teramond, G F; Tsushima, K; Wilson, D J

2013-01-01

180

Spin structure functions at SLAC E142/E143 experiments

International Nuclear Information System (INIS)

A status report is given on a new experiment performed recently at SLAC on polarized deep inelastic electron scattering. The E143 experiment will provide a precise measurement of the nucleon spin structure functions, allowing further tests of QCD Sum Rules and of the quarks contribution to the spin of the nucleon. (author)

181

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 sion 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

182

Last experimental results obtained at SLAC on the nucleon spin structure

International Nuclear Information System (INIS)

Recent precise measurements of the spin structure function g1 for proton and for deuteron using deep inelastic scattering of polarized electrons from polarized ammonia targets are presented. The integrals evaluated at the average experimental Q = 3 (GeV/c)2 are in agreement with previous results and well below the Ellis-Jaffe sum rule prediction, while the Bjorken sum rule prediction is satisfied. The analysis of the results in term of Quark Parton Model implies that the quark carry about a third of the nucleon helicity. (author). 17 refs., 5 figs

183

Quark structure of nucleons: experimental results of BCDMS, SMC (CERN) and HERMES (DESY)

International Nuclear Information System (INIS)

The review of the physics results of the nucleon quark-structure investigation in the completed experiments BCDMS and SMC (CERN) as well as current experiment at the HERMES set-up (DESY) is given. The perspectives of the further investigations of the nucleon spin physics are discussed in the context of future experiments at the COMPASS (CERN) and STAR (BNL) set-up

184

International Nuclear Information System (INIS)

We have performed a separation of the longitudinal and transverse structure functions for the 40Ca(e,e'p)39K reaction in the quasi-elastic region. Their ratio (L/T) is found reduced by about 30% from the Distorted Wave Impulse Approximation prediction. This result is compatible with the quenching of the Coulomb Sum-Rule observed in the inclusive ee' reaction. Since a possible swelling of the nucleon in nuclear matter has been advocated to explain this quenching, we have also measured the q-dependence of both structure functions to test this hypothesis. The results are not in favour of a large modification of the electromagnetic radius of the nucleon. From the transverse component, an upper limit of 5% can be derived for a possible increase of the radius

185

Self-consistent Green's functions calculation of the nucleon mean-free path

The extension of Green's functions techniques to the complex energy plane provides access to fully dressed quasi-particle properties from a microscopic perspective. Using self-consistent ladder self-energies, we find both spectra and lifetimes of such quasi-particles in nuclear matter. With a consistent choice of the group velocity, the nucleon mean-free path can be computed. Our results indicate that, for energies above 50 MeV at densities close to saturation, a nucleon has...

Rios, A.; Soma, V.

2011-01-01

186

Quark Structure of the Nucleon and Angular Asymmetry of Proton-Neutron Hard Elastic Scattering

We investigate an asymmetry in the angular distribution of hard elastic proton-neutron scattering with respect to 90deg center of mass scattering angle. We demonstrate that the magnitude of the angular asymmetry is related to the helicity-isospin symmetry of the quark wave function of the nucleon. Our estimate of the asymmetry within the quark-interchange model of hard scattering demonstrates that the quark wave function of a nucleon based on the exact SU(6) symmetry predict...

Granados, Carlos G.; Sargsian, Misak M.

2009-01-01

187

Studies of the transverse structure of the nucleon at JLab

Energy Technology Data Exchange (ETDEWEB)

Since the earliest measurements in the '70, hadronic physics deals with a number of surprising phenomena that cannot be explained in the framework of perturbative QCD. Examples are the small fraction of the proton spin carried by the valence quark spins, the persistence at high energies of single spin asymmetries and azimuthal asymmetries in unpolarized processes. It is now believed that the answer to these questions may come from the transverse motion of partons inside the nucleon, which is encoded in the Transverse Momentum Dependent (TMD) Parton Distribution Functions. Among the large variety of processes that can be described in terms of TMDs, a major role is played by Semi-Inclusive Deep Inelastic Scattering (SIDIS) reactions, in which, together with the scattered electron, one or more hadrons are detected in the final state. Single and Double Spin Asymmetries are the experimental observables sensitive to TMDs. The identification of the final hadrons allows the tagging of the quark involved in the reaction at the parton level, and then the flavor separation of the relevant TMDs. SIDIS reactions are studied at Jefferson Laboratories since many years and are one of the main items in the physics program after the upgrade of the CEBAF accelerator. The large amount of new data that will be available in few years calls for the implementation of new tools, such as multidimensional analyses and refined techniques of TMDs extraction from the experimental asymmetries. In this talk, the more recent results obtained at 6 GeV will be shown and the future measurements will be discussed.

Mirazita, Marco [INFN, Frascati (Italy)

2014-03-01

188

The Gerasimov-Drell-Hearn sum rule and nucleon structure

International Nuclear Information System (INIS)

A modification of the Gerasimov-Drell-Hearn sum rule suggested by the current experimental data is presented. Within the conventional theoretical framework, we find it necessary to consider the possibility of the presence of a localized region inside a nucleon, in which the electromagnetic (EM) gauge symmetry is spontaneously broken down, if the constraints of the gauge invariance, Lorentz invariance and the assumption of commutativity of the EM charge density operator at equal-time are considered. We also discuss the propagation of a virtual photon inside a nucleon under such a scenario. (author)

189

Unpolarized structure functions at Jefferson Lab

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...

Christy, M. E.; Melnitchouk, W.

2011-01-01

190

The general structure of weak electron-nucleon interactions

International Nuclear Information System (INIS)

In this chapter, the author first discusses the Fermi theory of beta-decay. Next, he looks at weak interactions due to neutral currents, in particular the electron-proton and electron-neutron interactions. He concludes, with a discussion of the non-relativistic potential of P-odd weak electron-nucleon interaction

191

International Nuclear Information System (INIS)

The deconvolution problem of the Constituent Quark Model (CQM) in finding the parton distribution function in valon at Q02 is reduced to an optimum problem and solved successfully with Newton-Raphson method. Moreover, by discretizing the QCD evolution equations into ordinary simultaneous differential equations, the author obtained the parton distribution functions in valon at arbitrary Q2>Q02, and thus, through convolution, finally found the Q2-dependent nucleon parton distribution functions in CQM picture

192

Structure and Flow of the Nucleon Eigenstates in Lattice QCD

A determination of the excited energy eigenstates of the nucleon, $s=\\frac{1}{2}$, $I=\\frac{1}{2}$, $N^{\\pm}$, is presented in full QCD using 2+1 flavor PACS-CS gauge configurations. The correlation-matrix method is used and is built using standard nucleon interpolators employing smearings at the fermion sources and sinks. We develop and demonstrate a new technique that allows the eigenvectors obtained to be utilized to track the propagation of the intrinsic nature of energy-states from one quark mass to the next. This approach is particularly useful for larger dimension correlation matrices where more near-degenerate energy-states can appear in the spectrum.

Mahbub, M Selim; Leinweber, Derek B; Moran, Peter J; Williams, Anthony G

2013-01-01

193

Gerasimov-Drell-Hearn sum rule and nucleon structure

A modification of the Gerasimov--Drell--Hearn sum rule suggested by the current experimental data is presented. Within the conventional theoretical framework, we find it necessary to consider the possibility of the presence of a localized region inside a nucleon, in which the electromagnetic (EM) gauge symmetry is spontaneous broken down, if the constraints of the gauge invariance, Lorentz invariance and the assumption of the commutativity of the EM charge density operator a...

Ying, S.

1998-01-01

194

Local Duality Predictions for x ~ 1 Structure Functions

Recent data on the proton F2 structure function in the resonance region suggest that local quark-hadron duality works remarkably well for each of the low-lying resonances, including the elastic, to rather low values of Q^2. Using quark-hadron duality we derive model-independent relations between structure functions at x -> 1 and elastic electromagnetic form factors. The x -> 1 behavior of nucleon polarization asymmetries and the neutron to proton structure function ratios are predicted from available data on the nucleon electric and magnetic form factors.

Melnitchouk, W

2001-01-01

195

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

196

Structure Functions at Low Q^2: Target Mass Corrections

Energy Technology Data Exchange (ETDEWEB)

We discuss recent developments in the study of structure functions at low Q^2, focusing in particular on the issue of target mass corrections (TMC) to nucleon structure functions. We summarize the standard TMC implementation, and contrast this with a new formulation which has the correct kinematic threshold behavior at finite Q^2 in the x -> 1 limit.

Wally Melnitchouk

2007-05-30

197

Shell structure and few-nucleon removal in intranuclear cascade

It is well known that intranuclear-cascade models generally overestimate the cross sections for one-proton removal from heavy, stable nuclei by a high-energy proton beam, but they yield reasonable predictions for one-neutron removal from the same nuclei and for one- nucleon removal from light targets. We use simple shell-model calculations to investigate the reasons of this deficiency. We find that a correct description of the neutron skin and of the energy density in the nuclear surface is crucial for the aforementioned observables. Neither ingredient is sufficient if taken separately.

Mancusi, D.; Boudard, A.; Carbonell, J.; Cugnon, J.; David, J.-C.; Leray, S.

2015-02-01

198

Shell structure and few-nucleon removal in intranuclear cascade

It is well known that intranuclear-cascade models generally overestimate the cross sections for one-proton removal from heavy, stable nuclei by a high-energy proton beam, but they yield reasonable predictions for one-neutron removal from the same nuclei and for one-nucleon removal from light targets. We use simple shell-model calculations to investigate the reasons of this deficiency. We find that a correct description of the neutron skin and of the energy density in the nuclear surface is crucial for the aforementioned observables. Neither ingredient is sufficient if taken separately.

Mancusi, Davide; Carbonell, Jaume; Cugnon, Joseph; David, Jean-Christophe; Leray, Sylvie

2014-01-01

199

Evolution of the nucleon structure in light nuclei

International Nuclear Information System (INIS)

The evolution of the EMC effect as a function of atomic mass A is considered for the first time for the lightest nuclei, D, 3He and , 4He, with an approach based on the Bethe-Salpeter formalism. We show that the pattern of the oscillation of the ratio rA(x)=F2A/F2N(D) with respect to the line rA(x)=1 varies with A, unlike the pattern for nuclei with masses A>4, where only the amplitude of the oscillation changes. It is found that the shape of the structure function distortions, which is typical for metals, is being reached in 3He

200

Longitudinal spin structure of the nucleon at COMPASS (SPS CERN)

We present new results on longitudinal inclusive double-spin asymmetry A 1, p ( x) in deep-inelastic muon-proton scattering and proton spin-dependent structure function g {1/ p }( x, Q 2). New COMPASS data on longitudinal polarised NH3 target were collected during the year 2011 with beam of positive muons with energy E = 200 GeV. Kinematical threshold Q 2 ? 1 (GeV/ c)2 and the fractional energy 0.1 < y < 0.9 allow us to cover low x region down to 0.025.

Zemlyanichkina, E.

2014-01-01

201

Impact of the recent Jefferson lab data on the structure of the nucleon

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

W.R.B. de, Araújo; T., Frederico; M., Beyer; H.J., Weber.

2004-03-01

202

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.)

203

The Isospin structure of the 3-nucleon form-factors

International Nuclear Information System (INIS)

Isospin is a good symmetry for the strong interaction. Nuclear observables are therefore easier to interpret by considering their isospin projections. The properties of the electromagnetic current of hadrons impose isospin 0 and 1 to be the relevant components for nuclear studies with electromagnetic probes. Thus, an isoscalar-isovector separation is not simply another way of presenting data. It helps to disentangle different physical processes that are mixed before separation. The purpose of the present contribution is to give the results of such a separation in the case of the 3-nucleon form factors. This approach may also be useful for a comparison of electromagnetic and weak properties: the electromagnetic observables have both components, whereas the charged weak interactions (such as beta-decay or muon-capture) are purely of isovector character

204

The isospin structure of the 3-nucleon form factors

International Nuclear Information System (INIS)

Isospin is a good symmetry for the strong interaction. Nuclear observables are therefore easier to interpret by considering their isospin projections. The properties of the electromagnetic current of hadrons impose isospin 0 and 1 to be the relevant components for nuclear studies with electromagnetic probes. Thus, an isoscalar-isovector (IS-IV) separation is not simply another way of presenting data. It helps to disentangle different physycal processes that are mixed before separation. A well known example is the subject of meson-exchange corrections (MEC) where the physical processes are of different nature for the isoscalar and invector pieces. Therefore an IS-IV separation is crucial to the understanding of the two independent isospin components. The purpose of the present contribution is to give the results of such a separation in the case of the 3-nucleon form factors. (orig./WL)

205

A pure $S$-wave covariant model for the nucleon

Energy Technology Data Exchange (ETDEWEB)

Using the manifestly covariant spectator theory, and modeling the nucleon as a system of three constituent quarks with their own electromagnetic structure, we show that all four nucleon electromagnetic form factors can be very well described by a manifestly covariant nucleon wave function with zero orbital angular momentum.

Franz Gross; G. Ramalho; M.T. Pena

2008-01-01

206

Magnetic electron scattering and valence nucleon radial wave functions

International Nuclear Information System (INIS)

Cross sections have been measured for elastic electron scattering from the magnetization distributions of 49Ti, 51V, 59Co, 87Sr, 93Nb, and 209Bi. Particular emphasis has been placed on the multipole distribution of the highest order possible, which dominates the magnetic form factor at momentum transfer values q between 1.7 and 3.0 fm-1. The data for the 1f/sub 7/2/ shell nuclei 49Ti, 51V and for the 1g/sub 9/2/ shell nuclei 87Sr, 93Nb are interpreted in terms of occupation probability and radial extension of the odd proton or neutron wave function. An accuracy of 1% is obtained for the valence orbit rms radii for both protons and neutrons. Corrections due to two-body magnetization currents and core polarization effects are investigated and found to be small. A detailed comparison of the experimental results with different types of density-dependent Hartree-Fock calculations is made in both momentum space and configuration space. It is found that the best available theory predicts the rms valence radii to within 2%. Comparisons are made between the present results and information on radial wave functions obtained from isotone shifts, proton scattering, and transfer reactions

207

Recent COMPASS results on the nucleon longitudinal spin structure and QCD fits

Directory of Open Access Journals (Sweden)

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.

Andrieux Vincent

2014-01-01

208

Single-Particle Structure of Radioactive Beams from One-Nucleon Knockout Reactions

Energy Technology Data Exchange (ETDEWEB)

Studies of the single-particle structure of radioactive beams produced in fragmentation reactions are described. The experiments are based on observing the individual final states of the projectile residues produced in one-nucleon knockout reactions. The measured partial cross sections to the various final states of the projectile residue and the shape of the corresponding longitudinal momentum distributions reflect the single particle properties, spectroscopic factors and the angular momentum l of the removed nucleon. Applications to {sup 26,27}P and {sup 15}C are discussed.

A. Navin; T. Aumann; D. Bazin; B.A. Brown; T. Glasmacher; P.G. Hansen; R.W. Ibbotson; V. Maddalena; B.M. Sherrill; J.A. Tostevin; J. Yurkon

1999-12-31

209

Effect of nucleon and hadron structure changes in-medium and its impact on observables

Energy Technology Data Exchange (ETDEWEB)

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.

K. Saito; K. Tsushima; A.W. Thomas

2005-07-05

210

Initial nucleon structure results with chiral quarks at the physical point

We report initial nucleon structure results computed on lattices with 2+1 dynamical M\\"obius domain wall fermions at the physical point generated by the RBC and UKQCD collaborations. At this stage, we evaluate only connected quark contributions. In particular, we discuss the nucleon vector and axial-vector form factors, nucleon axial charge and the isovector quark momentum fraction. From currently available statistics, we estimate the stochastic accuracy of the determination of $g_A$ and $_{u-d}$ to be around 10%, and we expect to reduce that to 5% within the next year. To reduce the computational cost of our calculations, we extensively use acceleration techniques such as low-eigenmode deflation and all-mode-averaging (AMA). We present a method for choosing optimal AMA parameters.

Syritsyn, S; Engelhardt, M; Green, J; Izubuchi, T; Jung, C; Krieg, S; Lin, M; Meinel, S; Negele, J; Ohta, S; Pochinsky, A; Shintani, E

2014-01-01

211

International Nuclear Information System (INIS)

The x dependence of hadron structure functions is investigated. If quarks can exist in very low mass states (10 MeV for d and u quarks) the pion structure function is predicted to behave like (1-x) and not (1-x)2 in a x-region around 1. Relativistic and non-relativistic quark bound state pictures of hadrons are considered together with their relation with the Q2 evolution of structure functions. Good agreement with data is in general obtained

212

International Nuclear Information System (INIS)

The surprising answer to this question Is nucleon deformed? is : Yes. The evidence comes from a study of the quark model of the single nucleon and when it is found in a nucleus. It turns out that many of the long standing problems of the Naive Quark Model are taken care of if the nucleon is assumed to be deformed. Only one value of the parameter PD ?1/4 (which specifies deformation) fits gA (the axial vector coupling constant) for all the semileptonic decay of baryons, the F/D ratio, the pion-nucleon-delta coupling constant fsub(?N?), the double delta coupling constant1 fsub(???), the Ml transition moment ??N and g1p the spin structure function of proton2. All this gives strong hint that both neutron and proton are deformed. It is important to look for further signatures of this deformation. When this deformed nucleon finds itself in a nuclear medium its deformation decreases. So much that in a heavy nucleus the nucleons are actually spherical. We look into the Gamow-Teller strengths, magnetic moments and magnetic transition strengths in nuclei to study this property. (author). 15 refs

213

Wave functions of the nucleon and its parity partner from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

We compute moments of distribution amplitudes using gauge configurations with two flavors of clover fermions from QCDSF/DIK and operators which are optimized with respect to their behavior under the lattice symmetries. The knowledge of these quantities helps in understanding the internal structure of hadrons and in the analysis of (semi-)exclusive processes. We present results for the nucleon distribution amplitude which suggest that the asymmetries (the deviations from the asymptotic form) are smaller than indicated by sum rule calculations. Using the same approach we were also able to calculate the same quantities for the N{sup *}(1535), the parity partner of the nucleon. These results show a stronger deviation from the asymptotic form. (orig.)

Warkentin, Nikolaus; Braun, Vladimir M.; Goeckeler, Meinulf [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)

2008-11-15

214

Recent COMPASS results on the nucleon longitudinal spin structure and QCD fits

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 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.

Andrieux, Vincent

2014-11-01

215

Transverse spin and transverse momentum structure of the nucleon from the COMPASS experiment

COMPASS is a fixed target experiment at the CERN SPS M2 beam line, taking data since year 2002. Part of the physics programme is dedicated to the study of the transverse spin and transverse momentum structure of the nucleon, by means of semi-inclusive deeply inelastic lepton scattering (SIDIS). For these measurements, data have been collected using transversely polarised proton (NH3) and deuteron (6LiD) targets. A selection of the results on the azimuthal asymmetries measured is presented, with particular focus on the most recent measurements from the data collected in 2007 and 2010 with the proton target. These results exhibit clear signals for the Collins asymmetry, interpreted as a convolution of a non-zero transversity PDF and Collins fragmentation function, and for the Sivers asymmetry which is related to the Sivers function, the most famous and discussed of the TMD PDFs. The data collected with the 6LiD target, have also been recently analysed to search for the azimuthal modulations in the production of hadrons which are expected to be present in the unpolarised part of the SIDIS cross-section. The azimuthal hadron asymmetries, which are related to the Boer-Mulders TMD PDF, show strong and somewhat puzzling kinematical dependencies.

Sozzi, Federica

2014-03-01

216

Transverse spin and transverse momentum structure of the nucleon from the COMPASS experiment

Directory of Open Access Journals (Sweden)

Full Text Available COMPASS is a fixed target experiment at the CERN SPS M2 beam line, taking data since year 2002. Part of the physics programme is dedicated to the study of the transverse spin and transverse momentum structure of the nucleon, by means of semi-inclusive deeply inelastic lepton scattering (SIDIS. For these measurements, data have been collected using transversely polarised proton (NH3 and deuteron (6LiD targets. A selection of the results on the azimuthal asymmetries measured is presented, with particular focus on the most recent measurements from the data collected in 2007 and 2010 with the proton target. These results exhibit clear signals for the Collins asymmetry, interpreted as a convolution of a non-zero transversity PDF and Collins fragmentation function, and for the Sivers asymmetry which is related to the Sivers function, the most famous and discussed of the TMD PDFs. The data collected with the 6LiD target, have also been recently analysed to search for the azimuthal modulations in the production of hadrons which are expected to be present in the unpolarised part of the SIDIS cross-section. The azimuthal hadron asymmetries, which are related to the Boer-Mulders TMD PDF, show strong and somewhat puzzling kinematical dependencies.

Sozzi Federica

2014-03-01

217

Excitation functions for multi-nucleon emission in helium ion reactions with 197Au

International Nuclear Information System (INIS)

Excitation functions for the production of heavy residues through 4He reactions on 197Au targets have been measured in the incident energy range of 35-50 MeV which probes and extends the lower limits of the excitation functions for cluster and multi-nucleon emission. The older cross-section values that partially cover this energy region have been re-evaluated using more recent decay schema data and compared with the present measurements. Interference from secondary neutrons in the cross-sections of interest were investigated. (orig.)

218

PREFACE: International Symposium on Exotic Nuclear Structure From Nucleons (ENSFN 2012)

The International Symposium on 'Exotic Nuclear Structure From Nucleons (ENSFN2012)' was held at the Koshiba Hall, the University of Tokyo, Japan, from October 10th to 12th, 2012. This symposium was supported by RIKEN Nishina Center (RNC) and the Center for Nuclear Study (CNS), University of Tokyo. This symposium was devoted to discussing recent achievement and perspectives in the structure of exotic nuclei from the viewpoint of the nuclear force. The following subjects were covered in this symposium from both theoretical and experimental sides: Evolution of shell structure and collectivity in exotic nuclei Ab-initio theory and its application to exotic nuclei Advancement in large-scale nuclear-structure calculations Effective Hamiltonian and energy density functional Spin-isospin responses New aspects of two- and three-body forces Impact on nuclear astrophysics Emphasis was placed on the development of large-scale nuclear-structure calculations and the new experimental information on exotic nuclei. Around 80 participants attended this symposium and we enjoyed 37 excellent invited talks and 9 selected oral presentations. A special talk was presented to celebrate the 60th birthday of professor Takaharu Otsuka, who has made invaluable contribution to the progress in the fields covered in this symposium. The organizing committee consisted of T Abe (Tokyo), M Honma (Aizu; chair), N Itagaki (YITP, Kyoto), T Mizusaki (Senshu), T Nakatsukasa (RIKEN), H Sakurai (Tokyo/RIKEN), N Shimizu (CNS, Tokyo; scientific secretary), S Shimoura (CNS, Tokyo), Y Utsuno (JAEA/CNS, Tokyo; scientific secretary). Finally, we would like to thank all the speakers and the participants as well as the other organizers for their contributions which made the symposium very successful. Michio Honma, Yutaka Utsuno and Noritaka Shimizu Editors Tokyo, April 2013 Sponsors logo1 Sponsors logo2 The PDF also contains the conference program.

Honma, Michio; Utsuno, Yutaka; Shimizu, Noritaka

2013-07-01

219

Structure of the Nucleon in Deep Inelastic Scattering (where from-where to)

International Nuclear Information System (INIS)

Deep Inelastic Scattering (DIS) of leptons off the proton is a rich laboratory for studying the structure of the nucleon as well as the properties of Quantum Chromodynamics - the theory of strong interactions. The power of DIS is derived from the fact that the electroweak field generated during the scattering of the lepton is well understood and thus one can probe the 'unknown structure' of the target hadron

220

Moments of Spin Structure Functions: Sum Rules and Polarizabilities

Energy Technology Data Exchange (ETDEWEB)

Nucleon structure study is one of the most important research areas in modern physics and has challenged us for decades. Spin has played an essential role and often brought surprises and puzzles to the investigation of the nucleon structure and the strong interaction. New experimental data on nucleon spin structure at low to intermediate momentum transfers combined with existing high momentum transfer data offer a comprehensive picture in the strong region of the interaction and of the transition region from the strong to the asymptotic-free region. Insight for some aspects of the theory for the strong interaction, Quantum Chromodynamics (QCD), is gained by exploring lower moments of spin structure functions and their corresponding sum rules (i.e. the Bjorken, Burkhardt-Cottingham, Gerasimov-Drell-Hearn (GDH), and the generalized GDH). These moments are expressed in terms of an operator-product expansion using quark and gluon degrees of freedom at moderately large momentum transfers.

Jian-Ping Chen

2010-10-01

221

When the new data on polarised lepton nucleon scattering are compared at the same value of $Q^2$ and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in $0(\\alpha_s)$, 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.

Close, Francis Edwin

1993-01-01

222

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 0(?s), higher twist effects, modern data on unpolarized 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)

223

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)

224

International Nuclear Information System (INIS)

This book contains the lectures given at the International Summer School on Structure and Stability of Nucleon and Nuclear Systems held in Predeal, Romania, in the period August 24 - September 5, 1998. The program of the school covered the following six topics: Nuclear structure (11 lectures); Dynamics of nuclear systems explored by collisions with various projectiles at different energies (8 lectures); Light and heavy cluster emission, cold and ternary fission (4 lectures); ?+-, 2???, 0??? and other neutrino processes; Structure and stability of nucleons (3 lectures); Nuclear matter under exotic conditions (2 lectures). Related to these topics were 17 short communications whose full text can be obtained on request from the authors or from a special issue of Romanian Journal of Physics. The aim of the school was concentrated on the behaviour of nuclear systems under extreme conditions, to understand newly discovered properties of complex nuclei and nucleons, to approach subjects bordering nuclear and particle physics, to identify specific phenomena taking place under conditions met presumably in stars, to investigate the newly explored systems of very short half-life. Exotic phenomena like halo structure of some light nuclei, superdeformation, structure of nuclei lying far from the stability line, specific properties of hot nuclei were also considered in many lectures

225

Purely Functional Structured Programming

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 proposal is that mainstream programmers can reap the benefits of purely functional programming like easily exploitable parallelism while using familiar structured programming syntax and without knowing concepts like monads. A second advantage is that professional purely functional programmers can often avoid hard to read functional code by using structured programming syntax that is often easier to parse mentally.

Obua, Steven

2010-01-01

226

Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks

Energy Technology Data Exchange (ETDEWEB)

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments

Huey-Wen Lin; Shigemi Ohta

2006-07-23

227

NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.

Energy Technology Data Exchange (ETDEWEB)

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments

LIN H.-W.; OHTA, S.

2006-10-02

228

Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction

Energy Technology Data Exchange (ETDEWEB)

The studies of N* structure represent a key direction in the N* Program with CLAS detector. After 12 GeV Upgrade, the dedicated experiment on the studies of N* structure at largest photon virtualities ever achieved Q^2<12 GeV^2 is scheduled for the first year of running with the CLAS12 detector. The current status and plans for theory support of the N* structure studies in exclusive meson electroproduction are presented. They include the recent advances in the reaction theory for extraction of N* electrocouplings from the data and the approaches for high level theoretical interpretation of these fundamental quantities, allowing us to access dynamics of non-perturbative strong interaction which is responsible for the resonance formation and explore how it emerges from QCD.

Aznauryan, Inna G. [Yerevan Physics Institute, JLAB; Bashir, Adnan; Braun, Vladimir M.; Brodsky, Stanley J. [SLAC; Burkert, Volker D. [JLAB; Chang, L.; Chen, Ch.; El-Bennich, Bruno O.; Cloet, Ian C.; Cole, Philip L. [Idaho State U.; Edwards, Robert G. [JLAB; Fedotov, Gleb V. [South Carolina U.; Giannini, Mauro M.; Gothe, Ralf W. [South Carolina U.; Lin, Huey-Wen [Washington; Kroll, Peter; Lee, T.-S. H.; Melnitchouk, Wally [JLAB; Mokeev, Viktor I [JLAB; Pena, Maria Teresa [CFTP; Ramalho, Gilberto T.F. [CFTP; Roberts, Craig D. [ANL; Santopinto, Elena; De Teramond, Guy F.; Tsushima, Kazuo [Adelaide U.; Wilson, David J. [Old Dominion U.

2013-06-01

229

Contends that the rapid accumulation of empirical knowledge has led to an emphasis on phenomenology in theoretical physics. The author points to the variety of ways in which mathematical methods, concepts and results find applications in physics and illustrates this with examples from his own work: (i) vibrations of periodic crystal lattice in the harmonic approximation; and (ii) the internal structure of the nucleon and its manifestation in various types of high energy collision. (3 refs).

Van Hove, Léon Charles Prudent

1974-01-01

230

What We Can Learn About Nucleon Spin Structure From Recent Data

We have used recent polarized deep-inelastic scattering data from CERN and SLAC to extract information about nucleon spin structure. We find that the SMC proton data, the E142 neutron data and the deuteron data from SMC and E143 give different results for fractions of the spin carried by each of the constituents. These appear to lead to two different and incompatible models for the polarized strange sea. The polarized gluon distribution occuring in the gluon anomaly does not...

Goshtasbpour, M.; Ramsey, Gordon P.

1995-01-01

231

On the role of diquarks in deep inelastic structure functions

International Nuclear Information System (INIS)

It has been suggested that almost all the Q2 dependence of nucleon structure functions can be understood in terms of quark (scaling) + diquark (approximately 1/Q2) contributions. The simplest version of such a model is confronted here with data from neutrino (high Q2) as well as electron (low Q2) experiments and no overall consistent agreement is found. (author)

232

On the role of diquarks inelastic structure functions

International Nuclear Information System (INIS)

It has been suggested that almost all the Q2 dependence of nucleon structure functions can be understood in terms of quark (scaling) + diquark (approx. equal to 1/Q2) contributions. We confront the simplest version of such a model with data from neutrino (high Q2) as well as electron (low Q2) experiments and find no overall consistent agreement. (orig.)

233

Polarized Structure Functions and the GDH Integral from Lattice QCD

The Gerasimov-Drell-Hearn integral $I_{GDH}(Q^2)$, and its relation to polarized nucleon structure functions, is discussed from the lattice perspective. Of particular interest is the variation of $I_{GDH}(Q^2)$ with $Q^2$, and what it may teach us about the origin and magnitude of higher-twist contributions.

Schierholz, G.

2004-01-01

234

Nuclear versus nucleon structure effects on nuclear transparency

Energy Technology Data Exchange (ETDEWEB)

Nuclear structure effects account for the observed enhancement of the nuclear transparency to moderate energy protons, with respect to the predictions of Glauber theory. This enhancement appears to be comparable to the one associated with the onset of color transparency in the Q2 range spanned by the available (e,e'p) data (Q2 < 7 (GeV/c)2). It is argued that in this kinematical regime a stronger colour transparency signal can be observed in the low energy loss tail of the inclusive electron-nucleus cross section, corresponding to large values of the Bjorken scaling variable x (x>2).

O. Benhar

1997-06-25

235

Chromatin Structure and Function

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

Wolffe, Alan P

1999-01-01

236

Electromagnetic structure of the nucleon and the Roper resonance in a light-front quark approach

A relativistic light-front quark model is used to describe both the elastic nucleon and nucleon-Roper transition form factors in a large Q2 range, up to 35 GeV2 for the elastic and up to 12 GeV2 for the resonance case. Relativistic three-quark configurations satisfying the Pauli exclusion principle on the light-front are used for the derivation of the current matrix elements. The Roper resonance is considered as a mixed state of a three-quark core configuration and a molecular N+sigma hadron component. Based on this ansatz we obtain a realistic description of both processes, elastic and inelastic, and show that existing experimental data are indicative of a composite structure of the Roper resonance.

Obukhovsky, Igor T; Gutsche, Thomas; Lyubovitskij, Valery E

2014-01-01

237

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 GRV’s free nucleon structure functions. Then, we calculate differential cross section of lepton scattering from those nuclei at the E=4...

Zolfagharpour, F.; Mh, Mosavi; Jedi Chorvadeh, M.

2012-01-01

238

Towards an understanding of nucleon spin structure: from hard to soft scales

The workshop "The Helicity Structure of the Nucleon" (BNL June 5, 2006) was organized as part of the 2006 RHIC & AGS Users' Meeting to review the status of the spin problem and future directions. The presentations can be found at http://www.phenix.bnl.gov/WWW/publish/caidala/UsersHelicityWorkshop2006/ . Recent data suggests small polarized glue and strangeness in the proton. Here we present a personal summary of the main results and presentations. What is new and exciting in the data, and what might this tell us about the structure of the proton ?

Bass, S D; Bass, Steven D.; Aidala, Christine A.

2006-01-01

239

Towards AN Understanding of Nucleon Spin Structure:. from Hard to Soft Scales

The workshop The Helicity Structure of the Nucleon (BNL June 5, 2006) was organized as part of the 2006 RHIC & AGS Users' Meeting to review the status of the spin problem and future directions. The presentations can be found at the workshop's website:1 www.phenix.bnl.gov/WWW/publish/caidala/UsersHelicityWorkshop2006/. Recent data suggest small polarized glue and strangeness in the proton. Here we present a personal summary of the main results and presentations. What is new and exciting in the data, and what might this tell us about the structure of the proton?

Bass, Steven D.; Aidala, Christine A.

240

Exchange currents and the internal structure of the nucleon in quark models

International Nuclear Information System (INIS)

The influence of internal nucleon structure on meson exchange currents has been investigated, in the framework of the non-relativistic constituent quark model and the MIT bag model with massless quarks. In comparison with the conventional theory of exchange currents, different strengths are found for the model-dependent higher-order terms and no ambiguity between pseudoscalar and pseudovector pion couplings. Furthermore, the retardation and excitation effects in the many-body system have to be treated consistently, in order to preserve gauge invariance. In this way 'damping' factors are obtained which differ in structure from the phenomenological form factors. (author)

241

Megakaryocyte structure and function.

Recent advances in the understanding of megakaryocyte (MK) function largely have been made through the careful observation of the morphological and structural events underlying MK development. Ultrastructural localization of enzymatic activities has facilitated the specific recognition of their committed diploid precursors. Observation of the sequential features of endomitosis demonstrates that although similar to normal mitosis, cell division aborts at the anaphase stage. The ability of thrombopoietin to induce the full maturation MKs in vitro not only facilitates platelet release but has increased our knowledge of various subcellular aspects of the phenomenon and eventually will improve the in vivo detection of the site of platelet formation and shedding. Finally, the structural and functional consequences of MK molecular dysfunction leading to thrombocytopenia or myelofibrosis can now be investigated because of the development of transgenic animal models. This review aims to incorporate these new findings within the classical knowledge of MK structure related to its function. PMID:10468153

Cramer, E M

1999-09-01

242

Energy Technology Data Exchange (ETDEWEB)

The authors calculate properties of A = 6 system using the accurate charge-dependent nucleon-nucleon (NN) potential at fourth order of chiral perturbation theory. By application of the ab initio no-core shell model (NCSM) and a variational calculation in the harmonic oscillator basis with basis size up to 16 {h_bar}{Omega} they obtain the {sup 6}Li binding energy of 28.5(5) MeV and a converged excitation spectrum. Also, they calculate properties of {sup 10}B using the same NN potential in a basis space of up to 8 {h_bar}{Omega}. The results are consistent with results obtained by standard accurate NN potentials and demonstrate a deficiency of Hamiltonians consisting of only two-body terms. At this order of chiral perturbation theory three-body terms appear. It is expected that inclusion of such terms in the Hamiltonian will improve agreement with experiment.

Navratil, P; Caurier, E

2003-10-14

243

International Nuclear Information System (INIS)

The authors calculate properties of A = 6 system using the accurate charge-dependent nucleon-nucleon (NN) potential at fourth order of chiral perturbation theory. By application of the ab initio no-core shell model (NCSM) and a variational calculation in the harmonic oscillator basis with basis size up to 16 (hbar)(Omega) they obtain the 6Li binding energy of 28.5(5) MeV and a converged excitation spectrum. Also, they calculate properties of 10B using the same NN potential in a basis space of up to 8 (hbar)(Omega). The results are consistent with results obtained by standard accurate NN potentials and demonstrate a deficiency of Hamiltonians consisting of only two-body terms. At this order of chiral perturbation theory three-body terms appear. It is expected that inclusion of such terms in the Hamiltonian will improve agreement with experiment

244

International Nuclear Information System (INIS)

A short review of the recent formulations of the models for the nucleon structure is given. Particular attention is devoted to the problem of the nucleon electromagnetic form factors and to the possible connections with recent high Q2 analysis of various reactions involving nucleons

245

Nucleon form factors for elastic electron-deuteron scattering at high momentum transfer

Elastic electron-deuteron scattering at high momentum transfer is investigated within the Bethe-Salpeter approach. The relativistic covariant Graz II separable kernel of nucleon-nucleon interactions is used to analyze the deuteron structure functions, form factors, and tensor of polarization components. The modern data for the electromagnetic structure of nucleons from the double polarization experiments, as well as some other models of the nucleon form factors, are considered.

Bekzhanov, A. V.; Bondarenko, S. G.; Burov, V. V.

2014-08-01

246

Review of nucleon-nucleon scattering experiments and many dinucleon resonances

International Nuclear Information System (INIS)

Structures appearing in various experimental data (particularly those with polarized beams) in nucleon-nucleon systems are reviewed. A number of candidates are presented for dibaryon resonances which can couple to nucleon-nucleon systems

247

Nucleon Compton scattering in the Dyson-Schwinger approach

International Nuclear Information System (INIS)

Full text: Compton scattering on the nucleon provides a unique tool to probe the nonperturbative structure of the nucleon. It allows access to a range of observables that are subject to studies at major experimental facilities, including: the nucleon's generalized polarizabilities; two-photon contributions to form factors; nucleon structure functions and generalized parton distributions; and proton antiproton annihilation processes. A nonperturbative approach for investigating such phenomena is given by the combination of QCD's Dyson-Schwinger equations with covariant Bethe-Salpeter and Faddeev equations. The framework has been recently applied for describing nucleon and delta elastic and transition form factors, and its systematic extension to Compton scattering, pion electroproduction and nucleon-pion scattering has been outlined. I will discuss recent progress in this area and present rst results for the nucleon's Compton scattering amplitude. (author)

248

Mathematics for structure functions

We show some of the mathematics that is being developed for the computation of deep inelastic structure functions to three loops. These include harmonic sums, harmonic polylogarithms and a class of difference equations that can be solved with the use of harmonic sums.

Vermaseren, J. A. M.; Moch, S.

2000-01-01

249

Spin content of the nucleon in the quark model

International Nuclear Information System (INIS)

Successful configuration-mixed quark-model wavefunctions for the nucleon are used to study the spin structure of the nucleon. These provide values within the constituent quark model with which the experimental result for the integrated spin-dependent structure function may be compared. (author)

250

Deuteron Spin Structure Functions in the Resonance and DIS Regions

Energy Technology Data Exchange (ETDEWEB)

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.

S. Kulagin; W. Melnitchouk

2007-10-03

251

Monte Carlo Generators for Studies of the 3D Structure of the Nucleon

Energy Technology Data Exchange (ETDEWEB)

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.

Avagyan, Harut A. [JLAB

2015-01-01

252

Status of nucleon structure calculations with 2+1 flavors of domain wall fermions

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.

Lin, Meifeng

2013-01-01

253

Nucleon correlation effects and nuclear characteristics

International Nuclear Information System (INIS)

The formalism of the density matrices and their natural orbital and overlap function representations are used in studies of nucleon correlation effects on basic characteristics of nuclear structure and reactions within various theoretical correlation methods. Special attention is paid to the restoration procedures which make it possible to obtain realistic one- and two-nucleon overlap functions on the basis of correlated one- and two-body density matrices, respectively, and to use them in nuclear reaction cross section calculations. (author)

254

The observation of the violation of Lam-Tung relation in the $\\pi N$ Drell-Yan process triggered many theoretical speculations. The TMD Boer-Mulders functions characterizing the correlation of transverse momentum and transverse spin for partons in unpolarized hadrons could nicely account for the violation. The COMPASS experiment at CERN will measure the angular distributions of dimuons from the unpolarized Drell-Yan process over a wide kinematic region and study the beam particle dependence. Significant statistics is expected from a successful run in 2015 which will bring further understanding of the origin of the violation of Lam-Tung relation and of the partonic transverse spin structure of the nucleon.

Chang, Wen-Chen

2015-01-01

255

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)

256

Nuclear Effects on the Extraction of Neutron Structure Functions

Nuclear effects in light nuclei due to the presence of spin-one isosinglet 6-quark clusters are investigated. The quark distributions of 6-quark clusters are obtained by using a perturbative QCD (pQCD) based framework, which allows us to get a good description of the ratio of the deuteron structure function to the free nucleon structure function. Nuclear effects on the extraction of the neutron structure functions $F_2^n$ and $g_1^n$ are estimated. We find that the effect on the extracted spin-dependent neutron structure function is very different from that on the spin-independent neutron structure function. The effect enhances the Bjorken sum by about 10%, whereas its correction to the Gottfried sum is rather small. The formalism for calculating nuclear effects is further used to evaluate the spin-dependent structure function of the $^3$He nucleus and a good self-consistent check is obtained.

Schmidt, I; Schmidt, Ivan; Yang, Jian-Jun

2001-01-01

257

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.)

258

Structure functions in ? decays

International Nuclear Information System (INIS)

Semileptonic decays of polarized ? leptons are investigated and the most general angular distribution of two and three meson final states is derived. Emphasis is put on ? studies in electron positron annihilation where the neutrino escapes detection and the ? restframe cannot be reconstructed. It is shown that the most general distribution caan be characterized by 16 structure functions, most of which can be determined in currently ongoing high statistics experiments. Of particular interest for the three meson case are the distribution of the normal to the Dalitz plane and the distribution around this normal. Predictions for the structure functions are given for the two and three pion case and for K*(?K?). Implications for an experiment where the ? restframe could be reconstructed are also considered. (orig.)

259

Isospin dependence of nucleon Correlations in ground state nuclei

The dispersive optical model (DOM) as presently implemented can investigate the isospin (nucleon asymmetry) dependence of the Hartree-Fock-like potential relevant for nucleons near the Fermi energy. Data constraints indicate that a Lane-type potential adequately describes its asymmetry dependence. Correlations beyond the mean-field can also be described in this framework, but this requires an extension that treats the non-locality of the Hartree-Fock-like potential properly. The DOM has therefore been extended to properly describe ground-state properties of nuclei as a function of nucleon asymmetry in addition to standard ingredients like elastic nucleon scattering data and level structure. Predictions of nucleon correlations at larger nucleon asymmetries can then be made after data at smaller asymmetries constrain the potentials that represent the nucleon self-energy. A simple extrapolation for Sn isotopes generates predictions for increasing correlations of minority protons with increasing neutron number. S...

Charity, R J; Sobotka, L G; Waldecker, S J

2013-01-01

260

New measurements of high-momentum nucleons and short-range structures in nuclei.

We present new measurements of electron scattering from high-momentum nucleons in nuclei. These data allow an improved determination of the strength of two-nucleon correlations for several nuclei, including light nuclei where clustering effects can, for the first time, be examined. The data also include the kinematic region where three-nucleon correlations are expected to dominate. PMID:22463628

Fomin, N; Arrington, J; Asaturyan, R; Benmokhtar, F; Boeglin, W; Bosted, P; Bruell, A; Bukhari, M H S; Christy, M E; Chudakov, E; Clasie, B; Connell, S H; Dalton, M M; Daniel, A; Day, D B; Dutta, D; Ent, R; El Fassi, L; Fenker, H; Filippone, B W; Garrow, K; Gaskell, D; Hill, C; Holt, R J; Horn, T; Jones, M K; Jourdan, J; Kalantarians, N; Keppel, C E; Kiselev, D; Kotulla, M; Lindgren, R; Lung, A F; Malace, S; Markowitz, P; McKee, P; Meekins, D G; Mkrtchyan, H; Navasardyan, T; Niculescu, G; Opper, A K; Perdrisat, C; Potterveld, D H; Punjabi, V; Qian, X; Reimer, P E; Roche, J; Rodriguez, V M; Rondon, O; Schulte, E; Seely, J; Segbefia, E; Slifer, K; Smith, G R; Solvignon, P; Tadevosyan, V; Tajima, S; Tang, L; Testa, G; Trojer, R; Tvaskis, V; Vulcan, W F; Wasko, C; Wesselmann, F R; Wood, S A; Wright, J; Zheng, X

2012-03-01

261

Experimental determination of the antiproton structure function by the Drell-Yan mechanism

We present results on the measurement of the Drell-Yan absolute cross section and of the shape of the nucleon structure functions by the analysis of massive dimuon events produced by antiprotons at 150 GeV and by protons at 150 and 200 GeV. Good agreement is found with the results of the neutrino deep inelastic scattering (DIS) experiments, for the shape of the valence structure function. The measured cross section however, when compared to the model predictions assuming the DIS nucleon structure function exhibits a normalization factor K = 2.3 ± 0.4.

Badier, J.; Boucrot, J.; Bourotte, J.; Burgun, G.; Callot, O.; Charpentier, Ph.; Crozon, M.; Decamp, D.; Delpierre, P.; Diop, A.; Du´, R.; Espigat, P.; Gandois, B.; Hagelberg, R.; Hansroul, M.; Karyotakis, Y.; Kienzle, W.; Lafontaine, A.; Le Du, P.; Lefrançois, J.; Leray, Th.; Maillard, J.; Matthiae, G.; Michelini, A.; Mi´, Ph.; Rahal, G.; Runolfsson, O.; Siegrist, P.; Tilquin, A.; Timmermans, J.; Valentin, J.; Vanderhaghen, R.; Weisz, S.

1980-11-01

262

Some analytic investigations of two-nucleon S matrices and wave functions

International Nuclear Information System (INIS)

Models of the two-nucleon interaction have been investigated in s wave using new analytic methods. They are central interactions expressible as sums of Yukawas. The results can be related to separable expansion of potentials and to inverse scattering theory. Some rational functions methods are presented which give solutions of the homogeneous Lippmann-Schwinger equation either at bound state or antibound state energies. These solutions are used to construct an analytic unitary pole expansion of rank N for both cases. A new result is the convergence of the phase shifts and wave functions at intermediate energies, up to k = 5fm-1, as the rank N approaches 13. Accurately computed phase shifts have been used to construct (i) rational S matrices and (ii) S matrices with a rational factor and an essential singularity at infinity. A powerful statistical Pade method is presented and employed in these constructions. S matrices such as these, characterized by their zeros and poles, are in a convenient form for inverse scattering theory. A new result, falling into case (ii), is that Gamow (i.e., resonance) states, identified as poles in the fourth quadrant of the momentum plane for the S matrix, occur in such large numbers for Re(k) ? 5 fm-1 that Gamow separable expansions would be expected to converge slowly at intermediate energies

263

Photon structure functions at small $x$ in holographic QCD

We investigate the photon structure functions at small Bjorken variable $x$ in the framework of the holographic QCD, assuming dominance of the Pomeron exchange. The quasi-real photon structure functions are expressed as convolution of the Brower-Polchinski-Strassler-Tan (BPST) Pomeron kernel and the known wave functions of the U(1) vector field in the five-dimensional AdS space, in which the involved parameters in the BPST kernel have been fixed in previous studies of the nucleon structure functions. The predicted photon structure functions, as confronted with data, provide a clean test of the BPST kernel. The agreement between theoretical predictions and data is demonstrated, which supports applications of holographic QCD to hadronic processes in the nonperturbative region. Our results are also consistent with those derived from the parton distribution functions of the photon proposed by Gl\\"uck, Reya, and Schienbein, implying realization of the vector meson dominance in the present model setup.

Watanabe, Akira

2015-01-01

264

Spin-dependent Parton Distributions from Polarized Structure Function Data

In the past year, polarized deep inelastic scattering experiments at CERN and SLAC have obtained structure function measurements off proton, neutron and deuteron targets at a level of precision never before achieved. The measurements can be used to test the Bjorken and Ellis-Jaffe sum rules, and also to obtain information on the parton distributions in polarized nucleons. We perform a global leading-order QCD fit to the proton deep inelastic data in order to extract the spin...

Gehrmann, T.; Stirling, W. J.

1994-01-01

265

International Nuclear Information System (INIS)

The topic of lepton-nucleon inclusive scattering is reviewed. Some of the experiments providing data on these interactions are described first. Then the constituent model of the nucleon and the contribution of various types of experiments are discussed; data from the experiments are compared and some simple predictions of the quark model are covered. Next, some of the fundamental notions behind quantum chromodynamics (QCD) are presented. Subsequent sections examine detailed tests of QCD. These include the ratio of longitudinal to transverse photoabsorption cross sections, the proton form factor in elastic ep scattering, and the dependence of structure functions on Q2. In conclusion, all the tests of QCD are tabulated, and the results are evaluated. 32 references, 33 figures, 4 tables

266

Nucleon color oscillations in nuclei and the EMC-effect

International Nuclear Information System (INIS)

The problem of the EMC-effect is discussed. It is shown that the existence of long-range six-quark clusters in nuclei allows to understand why the nucleon structure function in a nucleus differs from that of a free nucleon

267

We discuss the general formalism for the calculation in light-front quark models of the fully unintegrated, off-diagonal quark-quark correlator of the nucleon, parametrized in terms of generalized transverse momentum dependent parton distributions (GTMDs). By taking specific limits or projections, these GTMDs yield various transverse-momentum dependent and generalized parton distributions, thus providing a unified framework to simultaneously model different observables. The corresponding distributions in impact-parameter space are the Wigner functions which provide multidimensional images of the quark distributions in phase space. We present results within a light-front constituent quark model, discussing some of the complementary aspects encoded in the different distributions and the relation to the quark orbital angular momentum of the proton.

Pasquini, B

2013-01-01

268

Properties of meson structure function

International Nuclear Information System (INIS)

Meson structure functions have been extracted from high transverse momentum pion production by various hadron beams. The agreement with structure functions obtained by leptonic probes is amazingly good. The scaling violations in the pion structure function are extracted, and are consistent with those expected from asymptotic freedom. No indication of higher twist power law corrections is found

269

Parity doubling structure of nucleon at non-zero density in the holographic mean field theory

We develope the holographic mean field theory approach in a bottom-up holographic QCD model including baryons and scalar mesons in addition to vector mesons and pions. We study the effect of parity doubling structure of baryons at non-zero density to the equation of state between the chemical potential and the baryon number density. We first show that we can adjust the amount of nucleon mass coming from the chiral symmetry breaking by changing the boundary value of the five-dimensional baryon fields. Then, introducing the mean field for the baryon fields, we shows that, larger the percentage of the mass coming from the spontaneous $\\chi$SB is, more rapidly the chemical potential decreases with increasing baryon number density. We also discuss the interpretation of the result in terms of the Walecka-type model.

He, Bing-Ran

2013-01-01

270

Functional structure of stomodeum

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: identification of the structure providing outflow of liquid from stomodeum in the process of formation. Material and Methods. 150 stomodea have been investigated for the ways of removal of liquid by the following methods: stage-by-stage freezing, contrasting and macerations. Result. One of the ways of removal of liquid from enamel of a being formed tooth is the crypt canal. Conclusion. Function of the channel of a crypt of developing teeth consists of removal of biological specific dental fluid from a surface of enamel of stomodeum in a mouth in the following options: on an oral surface of alveolar processes, near a periodontal fissure, or directly in a periodontium of a milk tooth — predecessor.

Chependyuk ?.?.

2014-06-01

271

Spanwave Structure Functions Experiments

The SPANWAVE European large scale facility was used toperform an experiment on the small scale turbulence of breaking and non-breaking flows. Different types of both regular and irregular waves were generated at the 100 m long wave flume at LIM-UPC, Barcelona. A range of wave periode was varied between 3 and 6 s and wave hieght was varied between 0.1 and 0.4 m. The velocity components were measered using two sonic velocimeters (SONTEK). The measurements of the longitudinal velocity structure functions at different depths and horizontal positions in the turbulent flow shown that there is no clear inertial range where the absolute scaling expenents are constants. Using the technique of Extended Self Similarity (ESS), we can define an inertial where the relative scaling exponents tend to be a scale independent quantity. The departure from the Kolmogorov's law K41 is shown at all the measured positions.

Mahjoub, O. B.

272

DEFF Research Database (Denmark)

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.

Sinden, Richard R.; E. Pearson, Christopher

1998-01-01

273

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)

274

The nucleon-nucleon interaction

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Recent developements in our understanding of the fundamental nucleon-nucleon interaction are reviewed. Among the topics considered are (1) the so-called high-precision nucleon-nucleon potentials that emerged in the mid 1990s, (2) progress in the microscopic description of the intermediate-range part [...] of the nucleon-nucleon interaction in terms of correlated pion-pion and rho-pion exchange and (3) efforts towards a quantitative descripton of the nucleon-nucleon interaction utilizing methods based on effective field theory.

J., Haidenbauer.

2004-09-01

275

Studying the Phase-Space Structure of Nucleons Using Generalized Parton Distributions

We study the correlation of momentum and coordinate space distributions of partons which are measured in Deeply Virtual Compton Scattering (DVCS) reactions. Being able to understand the phase-space distributions of quarks, we hope to look into the question of `how much quark orbital angular momentum contributes towards the nucleon spin?' It was in fact suggested recently [1] that using the information provided by DVCS experiments, one can develop a complete three dimensional spatial picture of nucleons, along with the momentum distributions (the so-called Wigner distributions). However, in order pin down the spatial distribution in the longitudinal direction one has to take into account the constraint imposed by the uncertainty principle. In addition, similarly to inclusive deep-inelastic scattering, the lectromagnetic probe has an extended length in the longitudinal direction, known in the literature as ``Ioffe time'' [2]. Using the Generalized Parton Distributions (GPDs) obtained in [3] we define and evaluate ``Generalized Ioffe time'' distributions as a function of the additional degrees of freedom--both transverse, t = -2? and longitudinal, ?--extracted from DVCS experiments. [1] A. V. Belitsky, X. d. Ji and F. Yuan, Phys. Rev. D 69, 074014 (2004) [2] B. L. Ioffe, Phys. Lett. B 30, 123 (1969); V. Del Duca, S. J. Brodsky and P. Hoyer, Phys. Rev. D 46, 931 (1992); V. Braun, P. Gornicki and L. Mankiewicz, Phys. Rev. D 51, 6036 (1995). [3] S. Liuti and S. K. Taneja, Phys. Rev. D 70, 074019 (2004); H. Honkanen, S. K. Taneja, S. Ahmad and S. Liuti, in preparation.

Ahmad, Saeed; Liuti, Simonetta; Honkanen, Heli; Taneja, Swadhin K.

2006-11-01

276

Treatment of Two Nucleons in Three Dimensions

We extend a new treatment proposed for two-nucleon (2N) and three-nucleon (3N) bound states to 2N scattering. This technique takes momentum vectors as variables, thus, avoiding partial wave decomposition, and handles spin operators analytically. We apply the general operator structure of a nucleon-nucleon (NN) potential to the NN T-matrix, which becomes a sum of six terms, each term being scalar products of spin operators and momentum vectors multiplied with scalar functions of vector momenta. Inserting this expansions of the NN force and T-matrix into the Lippmann-Schwinger equation allows to remove the spin dependence by taking traces and yields a set of six coupled equations for the scalar functions found in the expansion of the T-matrix.

Fachruddin, I; Golak, J; Skibinski, R; Gloeckle, W; Witala, H; 10.1051/epjconf/20100305021

2010-01-01

277

Treatment of Two Nucleons in Three Dimensions

Directory of Open Access Journals (Sweden)

Full Text Available We extend a new treatment proposed for two-nucleon (2N and three-nucleon (3N bound states to 2N scattering. This technique takes momentum vectors as variables, thus, avoiding partial wave decomposition, and handles spin operators analytically. We apply the general operator structure of a nucleon-nucleon (NN potential to the NN T-matrix, which becomes a sum of six terms, each term being scalar products of spin operators and momentum vectors multiplied with scalar functions of vector momenta. Inserting this expansions of the NN force and T-matrix into the Lippmann-Schwinger equation allows to remove the spin dependence by taking traces and yields a set of six coupled equations for the scalar functions found in the expansion of the T-matrix.

Glöckle W.

2010-04-01

278

Operator analysis of nucleon decay

International Nuclear Information System (INIS)

The operator structure of the effective Hamiltonian mediating nucleon decay is analyzed. Selection rules diagnostic of the underlying superunified theories are derived. A kinship hypothesis important in analyzing nucleon decay is formulated and tests of it are proposed

279

Spin structure functions: a window into the structure of hadrons

International Nuclear Information System (INIS)

A large program of spin structure measurements is underway in Jefferson Lab's Hall B. Of particular interest is the first moment of the spin structure function g1, which 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. One can then study the transition from hadronic to quark degrees of freedom over the whole range of Q2. It is also interesting to look for the onset of quark-hadron duality in spin structure functions. We use longitudinally polarized electrons with energies from 1.6 to 5.7 GeV incident upon polarized NH3 and ND3 targets to investigate proton and deuteron spin observables in and above the resonance region. We present the GDH and Bjorken integrals using the 1.6 and 5.7 GeV data and comment on the validity of local quark-hadron duality over the wide kinematical range (0.05 ? Q2 ? 4.5 GeV2 and W < 3.2)

280

The Generalized Gerasimov-Drell-Hearn Integral and the Spin Structure of the Nucleon

The spin structure functions g1 and g2 have been calculated in the resonance region and for small and intermediate momentum transfer. The calculation is based on a gauge-invariant and unitary model for one-pion photo- and electroproduction. The predictions of the model agree with the asymmetries and the spin sturcture functions recently measured at SLAC, and the first moments of the calculated spin structure functions fullfil the Gerasimov-Drell-Hearn and Burkhardt-Cottingha...

Drechsel, D.; Kamalov, S. S.; Krein, G.; Tiator, L.

1998-01-01

281

Probing The Standard Model And Nucleon Structure Via Parity-violating Electron Scattering

Parity-violating electron scattering has developed over the last 25 years into a tool to study both the structure of electroweak interactions and the structure of nucleons. This thesis reports work on two parity- violation experiments, the Hall A Proton Parity Experiment (HAPPEX) and SLAC E-158. HAPPEX (Jefferson Laboratory, 1998–1999) measured the parity-violating asymmetry in elastic e- p scattering at Q2 = 0.477 GeV2. This asymmetry is sensitive to the proton's strange elastic form factors. An asymmetry of ALR = ?15.05 ± 0.98(stat) ± 0.56(syst) ppm was measured. This asymmetry measurement allowed HAPPEX to set new constraints on the strange elastic form factors of the proton: GEs+0.392G Ms=0.025 ±0.20± 0.014, where GEs and GMs are the strange electric and magnetic form factors of the proton, respectively. The first error is the quadrature sum of the experimental errors and the second error is due to uncertainty in electromagnetic form fact...

Humensky, T B

2003-01-01

282

Moments of Spin Structure Functions:. Sum Rules and Polarizabilities

Nucleon structure study is one of the most important research areas in modern physics and has challenged us for decades. Spin has played an essential role and often brought surprises and puzzles to the investigation of the nucleon structure and the strong interaction. New experimental data on nucleon spin structure at low to intermediate momentum transfers combined with existing high momentum transfer data offer a comprehensive picture in the strong region of the interaction and of the transition region from the strong to the asymptotic-free region. Insight into some aspects of the theory for the strong interaction, Quantum Chromodynamics (QCD), is gained by exploring lower moments of spin structure functions and their corresponding sum rules (i.e., the Bjorken, Burkhardt-Cottingham, Gerasimov-Drell-Hearn (GDH), and the generalized GDH). These moments are expressed in terms of an operator-product expansion using quark and gluon degrees of freedom at moderately large momentum transfers. The higher-twist contributions have been examined through the evolution of these moments as the momentum transfer varies from higher to lower values. Furthermore, QCD-inspired low-energy effective theories, which explicitly include chiral symmetry breaking, are tested at low momentum transfers. The validity of these theories is further examined as the momentum transfer increases to moderate values. It is found that chiral perturbation theory calculations agree reasonably well with the first moment of the spin structure function g1 at low momentum transfer of 0.05-0.1 GeV2 but fail to reproduce some of the higher moments, noticeably, the neutron data in the case of the generalized polarizability ?LT. The Burkhardt-Cottingham sum rule has been verified with good accuracy in a wide range of Q2 assuming that no singular behavior of the structure functions is present at very high excitation energies.

Chen, J.-P.

283

Measurement of the spin structure function GP1 (X, Q2) with CLAS at Jefferson Lab

International Nuclear Information System (INIS)

Inelastic scattering using polarized nucleon targets and polarized charged lepton beams allows the extraction of the structure functions g1 and g2 which provide information on the spin structure of the nucleon. A program designed to study such processes has been underway in Jefferson Lab since 1998. A polarized electron beam, solid polarized NH3 and ND3 targets and the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B were used to collect the desired data. The measurements cover the resonance region with unprecedented detail and add significantly to the DIS data set at low to moderate Q2 and moderate to high x. The measured electron asymmetries are analyzed to produce quantities of interest, such as the photon-nucleon asymmetry AP1+, the spin structure function gP1 and its first moment Gamma1

284

Light-front quark distributions in the nucleon and nucleon electromagnetic form factors

Energy Technology Data Exchange (ETDEWEB)

Longitudinal and transverse quark momentum distributions in the nucleon are calculated from a phenomenological quark-nucleon vertex function obtained through an investigation of the nucleon electromagnetic form factors within a light-front framework.

Pace, E. [Dipartimento di Fisica, Universita degli Studi di Roma ' Tor Vergata' and Istituto Nazionale di Fisica Nucleare, Sezione Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy); Melo, J.P.B.C. de [Centro de Ciencias Exatas e Tecnologicas, Universidade Cruzeiro do Sul, 08060-070, Sao Paulo (Brazil); Frederico, T. [Dep. de Fisica, Instituto Tecnologico de Aeronautica, 12.228-900 Sao Jose dos Campos, Sao Paulo (Brazil); Pisano, S. [IN2P3, Institut de Physique Nucleaire d' Orsay, 91404 Orsay (France); Salme, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Roma, P.le A. Moro 2, 00185 Roma (Italy)

2010-02-15

285

Nuclear effects in the F3 structure function

By using a relativistic framework and accurate nuclear spectral functions we evaluate the ratio F_{3A}/AF_{3N} of deep inelastic neutrino scattering. Parametrizations of this ratio for different values of Q^2 are provided. These results should be useful for taking into account the nuclear effects in analyses of experimental data in neutrino reactions in nuclear targets, and test QCD predictions for the nucleon structure functions. In particular, the size of the nuclear corrections is of the same order of magnitude as the size of the QCD corrections to the Gross-Llewellyn Smith sum rule.

Marco, E; Singh, S K

1998-01-01

286

Tensor-polarized structure functions: Tensor structure of deuteron in 2020's

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\

Kumano, S

2014-01-01

287

Nucleon Electromagnetic Form Factors

International Nuclear Information System (INIS)

Although nucleons account for nearly all the visible mass in the universe, they have a complicated structure that is still incompletely understood. The first indication that nucleons have an internal structure, was the measurement of the proton magnetic moment by Frisch and Stern (1933) which revealed a large deviation from the value expected for a point-like Dirac particle. The investigation of the spatial structure of the nucleon, resulting in the first quantitative measurement of the proton charge radius, was initiated by the HEPL (Stanford) experiments in the 1950s, for which Hofstadter was awarded the 1961 Nobel prize. The first indication of a non-zero neutron charge distribution was obtained by scattering thermal neutrons off atomic electrons. The recent revival of its experimental study through the operational implementation of novel instrumentation has instigated a strong theoretical interest. Nucleon electro-magnetic form factors (EMFFs) are optimally studied through the exchange of a virtual photon, in elastic electron-nucleon scattering. The momentum transferred to the nucleon by the virtual photon can be selected to probe different scales of the nucleon, from integral properties such as the charge radius to scaling properties of its internal constituents. Polarization instrumentation, polarized beams and targets, and the measurement of the polarization of the recoiling nucleon have been essential in the accurate separation of the charge and magnetic form eparation of the charge and magnetic form factors and in studies of the elusive neutron charge form factor

288

This book deals with the constructive Weierstrassian approach to the theory of function spaces and various applications. The first chapter is devoted to a detailed study of quarkonial (subatomic) decompositions of functions and distributions on euclidean spaces, domains, manifolds and fractals. This approach combines the advantages of atomic and wavelet representations. It paves the way to sharp inequalities and embeddings in function spaces, spectral theory of fractal elliptic operators, and a regularity theory of some semi-linear equations. The book is self-contained, although some parts may

Triebel, Hans

2012-01-01

289

Comments on pseudoscalar-nucleon coupling

International Nuclear Information System (INIS)

In the light of the recent EMC measurement of polarized muon-proton scattering we reexamine the coupling of the pseudoscalar Higgs boson to nucleons in a class of spontaneous CP-violation models where CP-violation can arise from the scalar-pseudoscalar Higgs boson mixings mechanism. Previous naive estimates of the effective direct Higgs-nucleon coupling can be reduced by taking into account the EMC data on the spin-dependent structure function. We show that this coupling can be consistent with being zero. This implies that the electric dipole moment of neutron induced by this Higgs-nucleon coupling in these models may vanish instead of dominating over the other contributions. Remarks on axion-nucleon coupling are also given

290

Renal Structure & Function Activities

This activity includes three sequential classroom activities for pairs of students using worksheets. This includes removeable stickers sequencing kinesthetic activity, diagram coloring and table matching to correlate nephron and cell-level anatomical features with physiological function.

Ms. Terry Thompson (Wor-Wic Community College Math/Science)

2007-07-31

291

On Electroweak Moments of Baryons and Spin-Flavour Structure of the Nucleon

The phenomenological sum-rule-based approach is used to discuss the quark composition dependence of some static and quasi-static electroweak characteristics of nucleons.The role of nonvalence degrees of freedom, the nucleon sea partons and/or peripheral meson currents, is shown to be important to select and make use of the relevant symmetry parametrization of hadron observables. With our preferable universal value of the SU(3)-symmetry parameter $\\alpha_{D}=D/F+D=.58$, taken...

Gerasimov, S. B.

1997-01-01

292

Bound Nucleon Form Factors, Quark-Hadron Duality, and Nuclear EMC Effect

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.

Tsushima, K; Melnitchouk, W; Saitô, K; Thomas, A W

2003-01-01

293

Electro-Magnetic Nucleon Form Factors and their Spectral Functions in Soliton Models

It is demonstrated that in simple soliton models essential features of the electro-magnetic nucleon form factors observed over three orders of magnitude in momentum transfer $t$ are naturally reproduced. The analysis shows that three basic ingredients are required: an extended object, partial coupling to vector mesons, and relativistic recoil corrections. We use for the extended object the standard skyrmion, one vector meson propagator for both isospin channels, and the rela...

Holzwarth, Gottfried

1996-01-01

294

International Nuclear Information System (INIS)

The properties and formation are described of ?-nucleon atoms, the Larmor method of muon spin precession is discussed and the experimental confirmation of the existence of ?-nucleon atoms is shown. The prospects of their use are indicated. (J.P.)

295

Structure functions at large x

Structure function data together with other measurements from fixed-target deep inelastic scattering and hadron-hadron collider experiments which contribute to our knowledge of the parton density functions are reviewed. The inclusive cross-section measurements of neutral and charged current interactions at HERA are presented and their impact on the parton density functions is discussed. Future prospects for an improved knowledge of the parton density functions at large x are...

Zhang, Zhiqing

2001-01-01

296

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

297

Production of open charm in muon nucleon interactions

International Nuclear Information System (INIS)

Cross sections for open charm production are derived from dimuon and trimuon events. The nucleon structure function F2(charm) and the charm distribution c(x,Q2) inside the nucleon are calculated and compared to photon-gluon-fusion and intrinsic charm model predictions. The gluon distribution G(x,Q2) inside the nucleon can be studied in the framework of the photon-gluon-fusion model and is found to be independent of Q2. The data favour a rising fragmentation function D(z) for charm quarks

298

Nucleon-nucleon correlations in dense nuclear matter

International Nuclear Information System (INIS)

In this thesis new results on the problematics of the formation of nucleon-nucleon correlations in nuclear matter could be presented. Starting from a general study of the two-particle problem in matter we studied the occurrence of a suprafluid phase (pair condensate of nucleons). The Gorkov decoupling by means of anomalous Green functions was generalized, so that also Cooper pairs with spin 1 (triplet pairing) can be described. A generalized gap equation resulted, which permits to determine the order parameters of the suprafluied phase in arbitrary channels of the nucleon-nucleon scattering states. This equation was solvd in the 1S0-, in the 3P2-3F2, and in the 3S1-3D1 channel under application of realistic nucleon-nucleon potentials. The behaviour of the resulting gap parameters in the single channels was studied as function of density and temperature. (orig.)

299

Comparison of moments from the valence structure function with QCD predictions

International Nuclear Information System (INIS)

Moments (both ordinary and Nachtmann) of the nucleon valence structure function measured in high Q2 ?Fe scattering are presented, supplemented by data from deep inelastic eD scattering. These data seem to agree with QCD predictions for vector gluons. The QCD parameter ? is found to be of the order 0.5 GeV. (Auth.)

300

The internal structures of the nucleon resonances $N(1875)$ and $N(2120)$

A nucleon resonance with spin-parity $J^P=3/2^-$ and mass about 2.1 GeV is essential to reproduce the photoproduction cross sections for $\\Lambda(1520)$ released by the LEPS and CLAS Collaborations. It can be explained as the third nucleon resonance state $[3/2^-]_3$ in the constituent quark model so that there is no position to settle the $N(1875)$ which is listed in the PDG as the third $N3/2^-$ nucleon resonance. An interpretation is proposed that the $N(1875)$ is from the interaction of a decuplet baryon $\\Sigma(1385)$ and a octet meson $K$, which is favored by a calculation of binding energy and decay pattern in a Bethe-Salpeter approach.

He, Jun

2015-01-01

301

Energy Technology Data Exchange (ETDEWEB)

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.

Colleen Ellis

2010-07-01

302

We present a relativistic chiral effective theory for symmetric and asymmetric nuclear matter taken in the Hartree-Fock scheme. The nuclear binding is insured by a background chiral invariant scalar field associated with the radial fluctuations of the chiral quark condensate. Nuclear matter saturation is obtained once the scalar response of the nucleon generating three-body repulsive forces is incorporated. For these parameters related to the scalar sector and quark confinement mechanism inside the nucleon we make use of an analysis of lattice results on the nucleon mass evolution with the quark mass. The other parameters are constrained as most as possible by standard hadron and nuclear phenomenology. Special attention is paid to the treatment of the propagation of the scalar fluctuations. The rearrangement terms associated with in-medium modified mass and coupling constants are explicitly included to satisfy the Hugenholtz -Van Hove theorem. We point out the important role of the tensor piece of the rho exc...

Massot, E

2008-01-01

303

Density-dependent effective nucleon-nucleon interaction from chiral three-nucleon forces

We derive density-dependent corrections to the in-medium nucleon-nucleon interaction from the leading-order chiral three-nucleon force. To this order there are six distinct one-loop diagrams contributing to the in-medium nucleon-nucleon scattering T-matrix. Analytic expressions are presented for each of these in both isospin-symmetric nuclear matter as well as nuclear matter with a small isospin asymmetry. The results are combined with the low-momentum nucleon-nucleon potential V(low-k) to obtain an effective density-dependent interaction suitable for nuclear structure calculations. The in-medium interaction is decomposed into partial waves up to orbital angular momentum L = 2. Our results should be particularly useful in calculations where an exact treatment of the chiral three-nucleon force would otherwise be computationally prohibitive.

Holt, J W; Weise, W

2009-01-01

304

Electromagnetic Structure and Reactions of Few-Nucleon Systems in ?EFT

Directory of Open Access Journals (Sweden)

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.

Schiavilla R.

2010-04-01

305

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.)

306

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

307

Measurement of the proton spin structure function g1p

International Nuclear Information System (INIS)

In order to check the Bjorken sum rule and confirm the EMC surprising conclusion on the spin structure of the proton, the measurement of the spin structure function of the proton has been performed by the Spin Muon Collaboration via the polarized muon nucleon deep inelastic scattering. The results of the 1993 run are presented within a kinematical range of 0.003 2 = 10 GeV2. The first moment of the polarized spin structure function g1p is found to be two standard deviations below the Ellis-Jaffe sum rule. Assuming SU(3) for hyperons ? decays, the quark spin contribution to the proton spin is extracted. Combining all available data on proton, neutron and deuton, The Bjorken sum rule is confirmed within 10%. (author). 25 refs., 3 figs., 2 tabs

308

Nuclear structure functions in the boundary region of the single-particle kinematics

International Nuclear Information System (INIS)

A theoretical analysis of nuclear functions in the region x?1 is given. It is shown that the contributions of pure nucleons and multiquak components of the nuclear wave function in this region are comparable and the binding effects and Q2-evolution lead to softening of the quark distributions in nucleus. Numerical predictions for the carbon structure function in the cumulative region were made

309

SYSTEMS THEORY AND STRUCTURAL FUNCTIONALISM

Directory of Open Access Journals (Sweden)

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

Shrikant Yelegaonkar

2014-12-01

310

Charge structure of the hadronic final state in deep-inelastic muon-nucleon scattering

International Nuclear Information System (INIS)

The general charge properties of the hadronic final state produced in ?+p and ?+d interactions at 280 GeV are investigated. Quark charge retention and local charge compensation is observed. The ratio F2n/F2p of the neutron to proton structure function is derived from the measurement of the average hadronic charge in ?d interactions. (orig.)

311

International Nuclear Information System (INIS)

One-nucleon overlap functions required for various nucleon-removal calculations must be solutions of the inhomogeneous equation with a source term whose shape and strength are determined by nuclear wave functions and the effective interaction of the removed nucleon with the nucleons in the remainder nucleus. A number of previous works has reported calculations of the source term and the overlap functions for a range of A?16 nuclei. It was shown that the source-term approach gives reasonable results for spectroscopic factors and asymptotic normalization coefficients and, in particular, it explains the phenomenon of reduction of spectroscopic factors observed in knockout reactions. In the present article, the source-term approach has been extended to A?16 nuclei. To achieve this, a new technique has been developed which excludes the spurious center-of-mass motion within the translation-invariant oscillator shell model. Applications using this technique are performed for double-closed-shell nuclei, both stable and away from ? stability, such as 16,24O, 40,48,60Ca, 56,78Ni, 100,132Sn, and 208Pb. The spectroscopic factors and asymptotic normalization coefficients for one-nucleon removal and addition have been calculated. They are compared to experimental values and results from other microscopic models when available.

312

Nucleon-nucleon collision profile and cross section fluctuations

The nucleon-nucleon collision profile, being the basic entity of the wounded nucleon model, is usually adopted in the form of hard sphere or the Gaussian shape. We suggest that the cross section fluctuations given by the gamma distribution leads to the profile function which smoothly ranges between the both limiting forms. Examples demonstrating sensitivity of profile function on cross section fluctuations are discussed.

Rybczynski, Maciej

2013-01-01

313

We derive by quantum inversion the relativistic nucleon-nucleon Moscow-type optical potential which describes the $NN$ elastic scattering for $E_{lab}< 3$ GeV and deuteron properties. Using the relativistic quantum mechanics for systems with a fixed number of particles (point form dynamics) the angular distributions of the two-body deuteron photodisintegration differential cross-section are calculated. The calculations cover photon energies between 1.1 and 2.5 GeV. The good agreement between our theory, which has no free parameters, and the recent detailed experimental data confirms the concept of the deep attractive Moscow potential of quark origin with forbidden $S$- and $P$-states.

Khokhlov, N A; Neudatchin, V G

2006-01-01

314

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)

315

Energy Technology Data Exchange (ETDEWEB)

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.

D. Day

2007-03-01

316

Ecosystem structure and function modeling

An important component of ecological assessments is the ability to predict and display changes in ecosystem structure and function over a variety of spatial and temporal scales. These changes can occur over short (less than 1 year) or long time frames (over 100 years). Models may emphasize structural responses (changes in species composition, growth forms, canopy height, amount of old growth, etc.) or functional responses (cycling of carbon, nutrients, and water). Both are needed to display changes in ecosystem components for use in robust ecological assessments. Structure and function models vary in the ecosystem components included, algorithms employed, level of detail, and spatial and temporal scales incorporated. They range from models that track individual organisms to models of broad-scale landscape changes. This chapter describes models appropriate for ecological assessments. The models selected for inclusion can be implemented in a spatial framework and for the most part have been run in more than one system.

Humphries, H.C.; Baron, J.S.

2001-01-01

317

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

318

Structure functions and parton distributions

Energy Technology Data Exchange (ETDEWEB)

The MRS parton distribution analysis is described. The latest sets are shown to give an excellent description of a wide range of deep-inelastic and other hard scattering data. Two important theoretical issues-the behavior of the distributions at small x and the flavor structure of the quark sea-are discussed in detail. A comparison with the new structure function data from HERA is made, and the outlook for the future is discussed.

Martin, A.D.; Stirling, W.J. [Univ. of Durham (United Kingdom); Roberts, R.G. [Rutherford Appleton Lab., Chilton, Didcot (United Kingdom)

1995-07-01

319

On the Electron Structure Function

The collinear QCD structure of the electron is studied within the Standard Model. The electron structure function is defined and calculated in leading logarithmic approximation. It shows important contribution from the interference of the intermediate electroweak bosons. The problem of momentum scales is extensively discussed. The master equations for the QCD parton densities inside the electron are constructed and solved numerically in the asymptotic region. Significant cor...

Slominski, Wojciech; Szwed, Jerzy

1996-01-01

320

Structure functions and parton distributions

International Nuclear Information System (INIS)

The MRS parton distribution analysis is described. The latest sets are shown to give an excellent description of a wide range of deep-inelastic and other hard scattering data. Two important theoretical issues-the behavior of the distributions at small x and the flavor structure of the quark sea-are discussed in detail. A comparison with the new structure function data from HERA is made, and the outlook for the future is discussed

321

Relativistic heavy ion physics is the study of nuclear matter interacting at high energies and densities. The collisions of gold nuclei at the Relativistic Heavy Ion Collider (RHIC) provide a source of high density matter for the study and creation of a novel state of matter, the Quark-Gluon Plasma (QGP). The data set studied in this dissertation is taken from Au+Au interactions at a center of mass energy of 130 GeV, measured in summer 2000. This is the first such data produced at RHIC. The analysis presented here focuses upon the measurement of balance functions, which are new observables in the field of heavy ion physics. The balance function for heavy ion physics is introduced in Bass, Danielewicz, and Pratt, Phys. Rev. Lett. 85, 2689 (2000). The data were taken with the STAR (Solenoidal Tracker At RHIC) detector, with analysis performed on charged particles in a pseudorapidity region of |eta| diffusion. However, pairs which are created late have a narrow separation in rapidity. Balance functions with a broad width show an early hadronization and are reflective of collisions which can be described as a superposition of nucleon-nucleon collisions. Balance functions which have a narrow width suggest late hadronization which is indicative of the formation of a QGP. In addition to late hadronization, flow can narrow the balance function width even more than just the formation of QGP. The balance function was measured for all charged particle pairs and pion pairs as a function of pseudorapidity, with respect to four centralities of collisions ranging from the most central to the peripheral. The balance function was also measured for pion pairs as a function of rapidity. For these measurements, it is found that the central events have a narrow balance function when compared to peripheral events, with a smooth variation in the intervening centralities. The HIJING simulated nucleon-nucleon interactions has a width consistent with that of the peripheral data balance functions, when the simulated events are processed through a STAR detector simulation. A Bjorken thermal model in the simulated STAR detector gives a pion pair balance function width which is wider than the central events (although narrower than peripheral). However the addition of flow narrows the Bjorken model balance function to that of the central data. The contribution of the acceptance of the detector was studied with various mixed events, pseudorapidity cuts, and with a different normalization method in the balance function calculation. These measurements indicate that central events suggest late hadronization, which is consistent with Bjorken model predictions with the inclusion of additional radial flow. The balance function width of the peripheral collisions is consistent with model predictions incorporating a superposition of nucleon-nucleon scattering.

Tonjes, Marguerite Belt

322

Tensor-polarized structure functions: Tensor structure of deuteron in 2020's

We explain spin structure for a spin-one hadron, in which there are new structure functions, in addition to the ones (F1, F2, g1, g2) which exist for the spin-1/2 nucleon, associated with its tensor structure. The new structure functions are b1, b2, b3, and b4 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 b2 = 2xb1 in the Bjorken scaling limit. First, these new structure functions are introduced, and useful formulae are derived for projection operators of b1-4 from a hadron tensor W??. Second, a sum rule is explained for b1, and possible tensor-polarized distributions are discussed by using HERMES data in order to propose future experimental measurements and to compare them with theoretical models. A proposal was approved to measure b1 at the Thomas Jefferson National Accelerator Facility (JLab), so that much progress is expected for b1 in the near future. Third, formalisms of polarized proton-deuteron Drell-Yan processes are explained for probing especially tensor- polarized antiquark distributions, which were suggested by the HERMES data. The studies of the tensor-polarized structure functions will open a new era in 2020's for tensor-structure studies in terms of quark and gluon degrees of freedom, which are very different from ordinary descriptions in terms of nucleons and mesons.

Kumano, S.

2014-10-01

323

Energy Technology Data Exchange (ETDEWEB)

We discuss the Jefferson Lab low momentum transfer data on moments of the nucleon spin structure functions $g_1$ and $g_2$ and on single charged pion electroproduction off polarized proton and polarized neutron. A wealth of data is now available, while more is being analyzed or expected to be taken in the upcoming years. Given the low momentum transfer selected by the experiments, these data can be compared to calculations from Chiral Perturbation theory, the effective theory of strong force that should describe it at low momentum transfer. The data on various moments and the respective calculations do not consistently agree. In particular, experimental data for higher moments disagree with the calculations.The absence of contribution from the $\\Delta$ resonance in the various observables was expected to facilitate the calculations and hence make the theory predictions either more robust or valid over a larger $Q^2$ range. Such expectation is verified only for the Bjorken sum, but not for other observables in which the $\\Delta$ is suppressed. Preliminary results on pion electroproduction off polarized nucleons are also presented and compared to phenomenological models for which contributions from different resonances are varied. Chiral Perturbation calculations of these observables, while not yet available, would be valuable and, together with these data, would provide an extensive test of the effective theory.

Alexandre Deur

2009-12-01

324

New model for nucleon generalized parton distributions

International Nuclear Information System (INIS)

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, ? E+1 (x,?) which has the DD structure ?/? e(?,?, with e(?,?) being the DD that generates GPD E(x,?). 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|=?

325

A thermal model for the strangeness in nucleon

International Nuclear Information System (INIS)

A statistical model, that uses a confining potential model for quarks, was used to obtain the structure function of the nucleon. This model shows a good fit for the Gottfried sum rule, with a temperature of about 100 MeV. The instanton contribution will give the right splitting between ? (1232) and the Nucleon. Once adjusted the temperature parameter by the Gottfried sum rule, we show that the experimental result for the strange content of the nucleon can be obtained by adjusting the effective mass of the quark s. (author)

326

x- and xi-scaling of the Nuclear Structure Function at Large x

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 Q^2 = 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 \\xi. 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 \\xi opens up the possibility of accessing nuclear structure functions in the high-x region at lower values of Q^2 than previously believed.

Arrington, J; Averett, T; Baker, O K; De Bever, L; Bochna, C W; Böglin, W; Bray, B; Carlini, R D; Collins, G; Cothran, C D; Crabb, D; Day, D; Dunne, J A; Dutta, D; Ent, R; Filippone, B W; Honegger, A; Hughes, E W; Jensen, J; Jourdan, J; Keppel, C E; Koltenuk, D M; Lindgren, R; Lung, A; Mack, D J; McCarthy, J; McKeown, R D; Meekins, D G; Mitchell, J H; Mkrtchyan, H G; Niculescu, G; Niculescu, I; Petitjean, T; Rondon, Oscar A; Sick, I; Smith, C; Terburg, B; Vulcan, W F; Wood, S A; Yan, C; Zhao, J; Zihlmann, B

2001-01-01

327

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

328

International Nuclear Information System (INIS)

Deep recent data and phenomenology on low-x structure functions are discussed inelastic scattering. We will be interested primordially in the regions Q2 ? 0 i.e. the transition from ?p to, and x ? 10-4 - 10-6 i.e. the region of high parton densities

329

Rise in proton structure function

International Nuclear Information System (INIS)

By the choice of a new scale factor we obtain a good qualitative fit to the HERA data for the proton structure function in the small x region which exhibits double asymptotic scaling. Any scaling violations in the future measurements when made in smaller bins will be of immense value. (author). 19 refs, 6 figs

330

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.)

331

Structure functions and parton distributions

International Nuclear Information System (INIS)

Activities of the structure functions and parton distributions group is summarized. The impact of scheme-dependence of parton distributions (especially sea-quarks and gluons) on the quantitative formulation of the QCD parton model is highlighted. Recent progress on the global analysis of parton distributions is summarized. Issues on the proper use of the next-to-leading parton distributions are stressed

332

International Nuclear Information System (INIS)

To determine tritium wave function in the method of composite quark bags (CQB), the top vertex function G(p2) of He3?pd nucleus break up is calculated. G(p2) value is calculated for several combinations of triplet and singlet CQB potentials. It is noted that the CQB method brings about a more realistic description of the wave function in the three nucleon system

333

Nucleon Electromagnetic Form Factors

International Nuclear Information System (INIS)

Nucleon electromagnetic form factors are fundamental quantities related to the charge and magnetization distributions inside the nucleon. Understanding the nucleon electromagnetic structure in terms of the underlying quark and gluon degrees of freedom of quantum chromodynamics is a challenging and urgent task. The nucleon electromagnetic form factors have been studied in the past extensively in unpolarized electron scattering experiments. With the development in polarized beam, recoil polarimetry, and polarized target technologies, polarization experiments have provided more precise data on these quantities. At the same time, significant theoretical progress in areas ranging from effective field theories to lattice QCD calculations, has been made in describing these data. In this article, we review recent experimental and theoretical progress on this subject. We also provide the future outlook on this topic

334

Hard probes of short-range nucleon-nucleon correlations

Energy Technology Data Exchange (ETDEWEB)

The strong interaction of nucleons at short distances leads to a high-momentum component to the nuclear wave function, associated with short-range correlations between nucleons. These short-range, high-momentum structures in nuclei are one of the least well understood aspects of nuclear matter, relating to strength outside of the typical mean-field approaches to calculating the structure of nuclei. While it is difficult to study these short-range components, significant progress has been made over the last decade in determining how to cleanly isolate short-range correlations in nuclei. We have moved from asking if such structures exist, to mapping out their strength in nuclei and studying their microscopic structure. A combination of several different measurements, made possible by high-luminosity and high-energy accelerators, coupled with an improved understanding of the reaction mechanism issues involved in studying these structures, has led to significant progress, and provided significant new information on the nature of these small, highly-excited structures in nuclei. We review the general issues related to short-range correlations, survey recent experiments aimed at probing these short-range structures, and lay out future possibilities to further these studies.

J. Arrington, D. W. Higinbotham, G. Rosner, M. Sargsian

2012-10-01

335

Partially-Quenched Nucleon-Nucleon Scattering

Nucleon-nucleon scattering is studied to next-to-leading order in a partially-quenched extension of an effective field theory used to describe multi-nucleon systems in QCD. The partially-quenched nucleon-nucleon amplitudes will play an important role in relating lattice simulations of the two-nucleon sector to nature.

Beane, S R; Beane, Silas R.; Savage, Martin J.

2003-01-01

336

Neutron-star matter within the energy-density functional theory and neutron-star structure

In this lecture, we will present some nucleonic equations of state of neutron-star matter calculated within the nuclear energy-density functional theory using generalized Skyrme functionals developed by the Brussels-Montreal collaboration. These equations of state provide a consistent description of all regions of a neutron star. The global structure of neutron stars predicted by these equations of state will be discussed in connection with recent astrophysical observations.

Fantina, A. F.; Chamel, N.; Pearson, J. M.; Goriely, S.

2015-02-01

337

Hidden Color and the $b_1$ structure function of the deuteron

The $b_1$ structure function is an observable feature of a spin-1 system sensitive to non-nucleonic components of the target nuclear wave function. A simple model for hidden-color, six-quark configurations is proposed and found to give substantial contributions for values of $ x>0.2$. Good agreement with Hermes data is obtained. Predictions are made for an upcoming JLab experiment.

Miller, Gerald A

2014-01-01

338

Nuclear structure functions at low-x in a holographic approach

Energy Technology Data Exchange (ETDEWEB)

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.)

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

339

Polarized Parton Distributions in the Nucleon

The distribution of the spin of the nucleon among its constituents can be parametrized in the form of polarized parton distribution functions for quarks and gluons. Using all available data on the polarized structure function $g_1(x,Q^2)$, we determine these distributions both at leading and next-to-leading order in perturbation theory. We suggest three different, equally possible scenarios for the polarized gluon distribution, which is found to be only loosely constrained b...

Gehrmann, T.; Stirling, W. J.

1995-01-01

340

Structure functions in ?-->3?? decay

The structure functions in the ?-->3?? decay are extracted using the model proposed by Li. We compare the predictions of the Li model with the KS ones and the data from the OPAL experiment, and find that predictions by the model for wA(Q2) are consistent with the data except for in the high energy region (Q2>1.2 GeV2), and wC,wD,wE normalized to wA are in reasonable agreement with the experimental results. A running mass function of ma1 is proposed to the model.

Xiong, Zhaohua; Chen, Guoming; Chen, Hesheng

1999-01-01

341

Cell Structure and Function Lessons

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.

Ingrid Waldron

342

Functional nanometer-scale structures

Nanometer-scale structures have properties that are fundamentally different from their bulk counterparts. Much research effort has been devoted in the past decades to explore new fabrication techniques, model the physical properties of these structures, and construct functional devices. The ability to manipulate and control the structure of matter at the nanoscale has made many new classes of materials available for the study of fundamental physical processes and potential applications. The interplay between fabrication techniques and physical understanding of the nanostructures and processes has revolutionized the physical and material sciences, providing far superior properties in materials for novel applications that benefit society. This thesis consists of two major aspects of my graduate research in nano-scale materials. In the first part (Chapters 3--6), a comprehensive study on the nanostructures based on electrospinning and thermal treatment is presented. Electrospinning is a well-established method for producing high-aspect-ratio fibrous structures, with fiber diameter ranging from 1 nm--1 microm. A polymeric solution is typically used as a precursor in electrospinning. In our study, the functionality of the nanostructure relies on both the nanostructure and material constituents. Metallic ions containing precursors were added to the polymeric precursor following a sol-gel process to prepare the solution suitable for electrospinning. A typical electrospinning process produces as-spun fibers containing both polymer and metallic salt precursors. Subsequent thermal treatments of the as-spun fibers were carried out in various conditions to produce desired structures. In most cases, polymer in the solution and the as-spun fibers acted as a backbone for the structure formation during the subsequent heat treatment, and were thermally removed in the final stage. Polymers were also designed to react with the metallic ion precursors during heat treatment in some cases, which led to desired chemical phase formation. The residue of polymer thermal decomposition was also controlled and utilized for certain functionality in some nanostructures. Throughout this study, we successfully fabricated several novel functional structures and revealed a new formation mechanism of metal/metal oxide nanotubes. The magnetic and electrical properties of these nanostructures were studied and optimized for applications in soft magnetic materials and spintronics devices. In the second part, (Chapter 7) a study on memristive switching devices with magnetron-sputtered metal-semiconductor-metal thin film structures based on ZnO is presented. Resistive random access memory (RRAM) is a new, non-volatile memory based on the memristor effect theoretically predicted by Leon Chua in 1971 and first experimentally demonstrated by Hewlett Packard in 2008. The unit cell of a RRAM (a memristor) is a two-terminal device in which the switching medium is sandwiched between the top and bottom electrodes and the resistance of the switching medium can be modulated by applying an electrical signal (current or voltage) to the electrodes. On the other hand, the significance of a memristor, as the fourth element of circuit elements besides resistor, capacitor and inductor, is not limited to just being a candidate for next-generation memory. Owing to the unique i-v characteristics of non-linear memristors that cannot be duplicated with any combinations of the other three basic elements in a passive circuitry, many new electrical functions are being developed based on the memristors. In our study, various contact electrode combinations and semiconductor doping profiles were utilized to achieve different functional resistive switching behaviors and to help fundamentally understand the underlying switching mechanisms in ZnO-based thin film structures. Two distinctive switching mechanisms (ferroelectric charge-induced resistive switching and dopant-induced filament-type resistive switching) have been identified in specified structures. Among them, the ferroelectric charg

Chan, Tsz On Mario

343

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)

344

International Nuclear Information System (INIS)

Multiplicities for the semi-inclusive production of each charge state of ?± and K± mesons in deep-inelastic scattering are presented as a function of the kinematic quantities x, Q2, z and Phperpendicularto. 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?/u? at leading-order in ?s. These results show a strong z-dependence below z ? 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 ?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 ? 0.70. This is consistent with isospin invariance below z ? 0.70. The results at high values of z show strong signs of isospin symmetry breaking.

345

International Nuclear Information System (INIS)

The single-particle density distribution functions (SPDDF) are calculated for nucleons in 6He non-magic even-even nucleus. The calculations are performed in the intrinsic coordinate system, connected with the principal axes of the ellipsoid of the nucleus inertia. The hyper-spherical function approach has been used. The proton and neutron SPDDF are calculated both for the 1=0 state and 1=2 state of 6He. The proton constant SPDDF surface have ellipsoidal shape with the center coinciding with the center of the coordinate system. The neutron SPDDF have two well developed maxima located symmetrically respective to the center of the coordinate system. The ellipsoidal surfaces of the constant SPDDF in the 1=0 state have higher deformation than those for the 1=2 state both for protons and neutrons, and the maximum density of neutrons in the 1=0 state is higher than that in the 1=2 state. This result is an evidence for the prediction that light nuclei deformation is decreased with angular momenta increase

346

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.

Zahed, Ismail

2010-01-01

347

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

348

Nucleon knockout: reaction mechanisms

International Nuclear Information System (INIS)

The treatment of the reactions mechanisms involved in nucleon knockout concerns the ideas of what actually happens in nucleon knockout, whether the deviations from the simplest plane wave picture interfere with an extraction of the wave function, and whether or not the desire to measure the bound state wave functions blinds one to the possibility of obtaining other interesting information from this reaction or from finding exciting new processes taking place. Included are the plane- and distorted-wave impulse approximations, some failures, and more sophisticated reaction mechanisms. 12C(P,2P) and 4He(P,2P) are discussed covering cross sections and spectroscopic factors

349

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

350

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 discuss several aspects of deep inealstic structure functions in which the bound-state structure of the proton plays a crucial role: (1) the properties of the intrinsic gluon distribution associated with the proton bound-state wavefunction; (2) the separation of the quark structure function of the proton into intrinsic 'bound-valence' and extrinsic 'non-valence' components which takes into account the Pauli principle; (3) the properties and identification of intrinsic heavy quark structure functions; and (4) a theory of shadowing and anti-shadowing of nuclear structure functions, directly related to quark-nucleon interactions and the gluon saturation phenomenon. (orig.)

351

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

352

Studies on regge behaviour and spin-independent and spin-dependent structure functions

Deep Inelastic Scattering (DIS) experiments have provided important information on the structure of hadrons and ultimately the structure of matter and on the nature of interactions between leptons and hadrons, since the discovery of partons. Various high energy deep inelastic interactions lead to different evolution equations from which we obtain various structure functions giving information about the partons i.e. quarks and gluons involved in different scattering processes. Actually structure function is a mathematical picture of the hadron structure in the high energy region. Understanding the behaviour of the structure functions of the nucleon at low-x, where x is the Bjorken variable, is interesting both theoretically and phenomenologically. Structure functions are important inputs in many high energy processes and also important for examination of perturbative quantum chromodynamics (PQCD), the underlying dynamics of quarks and gluons. In PQCD, for high-Q2, where Q2 is the four momentum transfer in a DI...

Jamil, Begum Umme

2010-01-01

353

Polarized gluons in the nucleon

QCD suggests that gluons in the nucleon play an important role in {\\it so-called} ``the proton spin problem''. In this talk, the behavior of the polarized gluon distribution in the nucleon is discussed by using the positivity condition of distribution functions together with the unpolarized and polarized experimental data.

Mori, T; Yamanishi, T

1995-01-01

354

Tensor Structure Function b$_1$(x) For Spin-One Hadrons

High-energy spin physics became a popular topic recently after the EMC finding for the proton's spin content. There exist unmeasured spin-dependent structure functions ($b_1$, $b_2$, $b_3$, and $b_4$) for spin-one hadrons such as the deuteron. The tensor structure function $b_1(x)$ could be measured by the proposed 15 GeV European Electron Facility. The measurement provides important clues to physics of non-nucleonic components in spin-one nuclei and to tensor structures on ...

Kumano, S.

1993-01-01

355

Nucleon - Nucleon Interactions at Short Distances

Despite the progress made in understanding the NN interactions at long distances based on effective field theories, the understanding of the dynamics of short range NN interactions remains as elusive as ever. One of the most fascinating properties of short range interaction is its repulsive nature which is responsible for the stability of strongly interacting matter. The relevant distances, $\\le 0.5$ fm, in this case are such that one expects the onset of quark-gluon degrees of freedom with interaction being dominated by QCD dynamics. We review the current status of the understanding of the QCD dynamics of NN interactions at short distances, highlight outstanding questions and outline the theoretical foundation of QCD description of hard NN processes. We present examples of how the study of the hard elastic NN interaction can reveal the symmetry structure of valence quark component of the nucleon wave function and how the onset of pQCD regime is correlated with the onset of color transparency phenomena in har...

Sargsian, Misak M

2014-01-01

356

Nucleon and nucleon-pair momentum distributions in A <= 12 nuclei

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.

Wiringa, R B; Pieper, Steven C; Carlson, J

2013-01-01

357

Structure Function Measurement at HERA

Preliminary results on a measurement of the proton structure function F_2 are reported for momentum transfers squared Q^2 between 1.5~GeV^2 and 5000 GeV^2 and for Bjorken x between 5.10^{-5} and 0.32 using data collected by the HERA experiments H1 and ZEUS in 1994. F_2 increases significantly with decreasing x, even in the lowest reachable Q^2 region. The data are well described by a Next to Leading Order QCD fit, and support within the present precision that the rise at low...

Bernardi, Gregorio

1996-01-01

358

Supramolecular Structure and Function 9

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.

Pifat-Mrzljak, Greta

2007-01-01

359

International Nuclear Information System (INIS)

This Corrigendum contains a text that should replace the text between equations (16) and (19) (including equations (19)) in the article 'The Gerasimov-Drell-Hearn sum rule and nucleon structure', published in J. Phys. G: Nucl. Part. Phys. v. 22 p. 293-303

360

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)

361

Probing the parton content of the nucleon

The parton content of the nucleon is explored within a meson-cloud model developed to derive light-cone wave functions for the physical nucleon. The model is here applied to study electromagnetic form factors, distribution amplitudes and nucleon-to-meson transition distribution amplitudes.

Boffi, S

2009-01-01

362

QCD at low Q2 - a correspondence relation for moments of structure functions

International Nuclear Information System (INIS)

The precocious validity of QCD predictions in deep inelastic lepton nucleon scattering and e+e- annihilation is interpreted as a signal for an underlying 'correspondence principle' relating perturbative and nonperturbative physics on the Q2 average. Correspondence relations for nonsinglet moments of deep inelastic structure functions are formulated, discussed and successfully tested against experiment. The relations provide an independent determination of the QCD ?-parameter from low Q2 data in perfect agreement with results from large Q2 analyses. (author)

363

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: Fsub(2)sup(A)(x,Q2) = Fsub(2)sup(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

364

The Gerasimov-Drell Sum Rule and the Spin Structure of the Nucleon

The Gerasimov-Drell-Hearn sum rule is one of several dispersive sum rules that connect the Compton scattering amplitudes to the inclusive photoproduction cross sections of the target under investigation. Being based on such universal principles as causality, unitarity, and gauge invariance, these sum rules provide a unique testing ground to study the internal degrees of freedom that hold the system together. The present article reviews these sum rules for the spin-dependent cross sections of the nucleon by presenting an overview of recent experiments and theoretical approaches. The generalization from real to virtual photons provides a microscope of variable resolution: At small virtuality of the photon, the data sample information about the long-range phenomena, which are described by effective degrees of freedom (Goldstone bosons and collective resonances), whereas the primary degrees of freedom (quarks and gluons) become visible at the larger virtualities. Through a rich body of new data and several theoretical developments, a unified picture of virtual Compton scattering emerges, which ranges from coherent to incoherent processes, and from the generalized spin polarizabilities on the low-energy side to higher twist effects in deep-inelastic lepton scattering.

Drechsel, Dieter; Tiator, Lothar

2004-12-01

365

Remarks on the Electron Structure Function

The electron and photon structure functions are compared. Advantages of the electron structure function are demonstrated. At very high momenta probabilistic (partonic) interpretation can be preserved despite strong $\\gamma$-$Z$ interference. At present energies analyses of both the electron and the photon structure functions give an important test of the experimentally applied methods. Predictions for the electron structure function at present and future momenta are given.

Slominski, Wojciech; Szwed, Jerzy

2001-01-01

366

Sum rule measurements of the spin-dependent compton amplitude (nucleon spin structure at Q2 = 0)

International Nuclear Information System (INIS)

Energy weighted integrals of the difference in helicity-dependent photo-production cross sections (?1/2 - ?3/2) provide information on the nucleon's Spin-dependent Polarizability (?), and on the spin-dependent part of the asymptotic forward Compton amplitude through the Drell-Hearn-Gerasimov (DHG) sum rule. (The latter forms the Q2=0 limit of recent spin-asymmetry experiments in deep-inelastic lepton-scattering.) There are no direct measurements of ?1/2 or ?3/2, for either the proton or the neutron. Estimates from current ?-photo-production multipole analyses, particularly for the proton-neutron difference, are in good agreement with relativistic-l-loop Chiral calculations (?PT) for ? 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 · rvec D in the solid phase. Reaction channels will be identified in SASY, a large detector array covering about 80% of 4?. A high degree of symmetry in both target and detector will be used to minimize systematic uncertainties

367

Structure functions and the Gottfried sum from NMC data

International Nuclear Information System (INIS)

The QCD analysis of the Fp2 and Fd2 structure functions obtained by New Muon Collaboration is presented. It leads to precise determination of the gluon distribution down to x=0.008. The re-evaluation of the Gottfried sum, i.e., the integral ?(Fp2-Fn2)dx/x,based on better knowledge of the Fd2 at low x, gives at Q2=4 GeV2 value 0.235±0.026(total), significantly smaller than 1/3. This result can be interpreted as flavor symmetry violation in the nucleon sea. Similar conclusion was reached from the analysis of Drell-Yan asymmetry measured by NA51 experiment at CERN. copyright 1995 American Institute of Physics

368

Spin Structure Function Measurements from E143 at SLAC

Recent high statistics measurements of the nucleon spin structure functions by the E143 Collaboration are presented. The structure functions g sub 1 sup n and g sub 1 sup d have been measured over the range 0.029 < x < 0.8 and 1.3 < Q sup 2 < 10 (GeV/c) sup 2 using deep inelastic scattering of polarized electrons from polarized ammonia and deuterated ammonia targets. Evaluation of the integral GAMMA sub 1 sup p = integral sub 0 sup 1 g sub 1 sup p (x, Q sup 2)dx at fixed Q sup 2 = 3 (GeV/c) sup 2 yields 0.127 +- 0.004 +- 0.010, in agreement with previous experiments, but well below the Ellis-Jaffe sum rule prediction of 0.160 +- 0.006. The integral GAMMA sub 1 sup d = integral sub 0 sup 1 g sub 1 sup d (x,Q sup 2)dx also evaluated at fixed Q sup 2 = 3 (GeV/c) sup 2 gives 0.041 +- 0.004 +- 0.004, again below the Ellis-Jaffe sum rule prediction of 0.068 +- 0.005. From g sub 1 sup p and g sub 1 sup d , the neutron structure function g sub 1 sup n can be computed with GAMMA sub 1 sup n measured as -0....

Band, H R

2003-01-01

369

Isospin dependence of nucleon correlations in ground-state nuclei

International Nuclear Information System (INIS)

The dispersive optical model (DOM) as presently implemented can investigate the isospin (nucleon asymmetry) dependence of the Hartree-Fock-like potential relevant for nucleons near the Fermi energy. Data constraints indicate that a Lane-type potential adequately describes its asymmetry dependence. Correlations beyond the mean field can also be described in this framework, but this requires an extension that treats the non-locality of the Hartree-Fock-like potential properly. The DOM has therefore been extended to properly describe ground-state properties of nuclei as a function of nucleon asymmetry in addition to standard ingredients like elastic nucleon scattering data and level structure. Predictions of nucleon correlations at larger nucleon asymmetries can then be made after data at smaller asymmetries constrain the potentials that represent the nucleon self-energy. A simple extrapolation for Sn isotopes generates predictions for increasing correlations of minority protons with increasing neutron number. Such predictions can be investigated by performing experiments with exotic beams. The predicted neutron properties for the double closed-shell 132Sn nucleus exhibit similar correlations as those in 208Pb. Future relevance of these studies for understanding the properties of all nucleons, including those with high momentum, and the role of three-body forces in nuclei are briefly discussed. Such an implementation will require a proper treatment of the non-locality of the imaginary part of the potentials and a description of high-momentum nucleons as experimentally constrained by the (e, e' p) reactions performed at Jefferson Lab. (orig.)

370

Isospin dependence of nucleon correlations in ground-state nuclei

Energy Technology Data Exchange (ETDEWEB)

The dispersive optical model (DOM) as presently implemented can investigate the isospin (nucleon asymmetry) dependence of the Hartree-Fock-like potential relevant for nucleons near the Fermi energy. Data constraints indicate that a Lane-type potential adequately describes its asymmetry dependence. Correlations beyond the mean field can also be described in this framework, but this requires an extension that treats the non-locality of the Hartree-Fock-like potential properly. The DOM has therefore been extended to properly describe ground-state properties of nuclei as a function of nucleon asymmetry in addition to standard ingredients like elastic nucleon scattering data and level structure. Predictions of nucleon correlations at larger nucleon asymmetries can then be made after data at smaller asymmetries constrain the potentials that represent the nucleon self-energy. A simple extrapolation for Sn isotopes generates predictions for increasing correlations of minority protons with increasing neutron number. Such predictions can be investigated by performing experiments with exotic beams. The predicted neutron properties for the double closed-shell {sup 132}Sn nucleus exhibit similar correlations as those in {sup 208}Pb. Future relevance of these studies for understanding the properties of all nucleons, including those with high momentum, and the role of three-body forces in nuclei are briefly discussed. Such an implementation will require a proper treatment of the non-locality of the imaginary part of the potentials and a description of high-momentum nucleons as experimentally constrained by the (e, e' p) reactions performed at Jefferson Lab. (orig.)

Charity, R.J. [Washington University, Department of Chemistry, St. Louis, Missouri (United States); Dickhoff, W.H. [Washington University, Department of Physics, St. Louis, Missouri (United States); Sobotka, L.G. [Washington University, Department of Chemistry, St. Louis, Missouri (United States); Washington University, Department of Physics, St. Louis, Missouri (United States); Waldecker, S.J. [University of Tennessee, Department of Physics, Chattanooga, Tennessee (United States)

2014-02-15

371

Measurement of Spin Structure Functions at Low to Moderate Q2 using CLAS

International Nuclear Information System (INIS)

Spin structure functions of the nucleon in the region of large x and small to moderate Q2 continue to be of high current interest. A large experimental program to measure the spin structure function g1 and its first moment ?1 has been concluded at Jefferson Lab. An overview of the experiment and its kinematic coverage will be discussed. We will also show preliminary results from the 5.7 GeV and the 1.6 GeV data sets

372

The Jefferson Lab 12 GeV program on nucleon structure

Energy Technology Data Exchange (ETDEWEB)

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.

Burkert, Volker D. [JLAB

2013-10-01

373

Finite meson size effects in nucleon-nucleon phase shifts

International Nuclear Information System (INIS)

A realistic quark model of the nucleon is used to determine the interaction between two nucleons. A scalar potential is utilized to confine the quarks and to determine the quark wave function by solving a Dirac equation. Chiral symmetry suggests that confined quarks are surrounded by a pion cloud. A local pion quark interaction is used to determine the energy of such a pion cloud with parameters chosen to reproduce the pion-nucleon coupling found in one-boson exchange potentials. For a finite pion size, the cloud energy is finite. The pion cloud energy is included in variational non-relativistic quark model determination of the nucleon mass. A stable nucleon of the right size and mass comes out of this calculation. The form factors for the one-boson exchange potential are calculated taking finite meson size into account. The OBEP is combined with a non-relativistic quark model of the nucleon to provide input into a resonating group theory to calculate the two nucleon phase shifts. The two nucleon 1S0 phase shifts calculated agree well with experiment. The net effect of finite meson size in this model is a slightly smaller phase shift. (author)

374

Symmetry relations in nucleon decay

International Nuclear Information System (INIS)

Some experimental consequences of the structure of the effective hamiltonian for nucleon decay are presented. New results concern relations among inclusive decay rates, a striking test of the kinship hypothesis involving ?+ polarization, and soft ? theorems. (orig.)

375

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.

376

Structure and Function of Molecules and Cells

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.

Ingrid Waldron

377

The Structure of the Nucleon and it's Excited States

Energy Technology Data Exchange (ETDEWEB)

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.

None

1995-02-20

378

Precise measurements of the deuteron A(q2) structure function

International Nuclear Information System (INIS)

Among all deuteron observables, the A(q2) structure function plays a special role. Since it is sensitive to the shape of the deuteron wave function it is used as a test for models of the nucleon-nucleon interaction. In the absence of a neutron target, it also provides one of the best possible means for extracting the neutron electric form factor. To a smaller extent, A(q2) is also sensitive to meson exchange currents and relativistic effects. Delineating the effect of all these ingredients is however a difficult task. Part of the difficulty comes from the experimental side. In spite of a large number of measurements, the medium momentum transfer region is still not accurately known; precise data between q2 = 1 and 18 fm-2 are reported. 18 refs.; 6 figs

379

Nucleon electromagnetic form factors in a hypercentral quark model

Energy Technology Data Exchange (ETDEWEB)

We study the nucleon electromagnetic form factors within the frame work of hypercentral quark model. We have calculated nucleon electromagnetic form factors at low Q{sup 2}. We calculate the nucleon form factors using hypercentral wave function. The general nature of the nucleon form factors at low Q{sup 2} is consistent with the experimental results.

Thakkar, Kaushal [Department of Applied Physics, S. V. National Institute of Technology, Surat-395 007 (India) and Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120 (India); Vinodkumar, P. C. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120 (India)

2013-06-03

380

Azimuthal correlations in two hadron production in deep inelastic scattering of unpolarized leptons off transversely polarized nucleon are discussed. Specifically, a simple approach for accessing ratios of structure functions corresponding to Sivers effect and transversity induced single spin azimuthal asymmetries to unpolarized structure functions is presented. This approach is then applied to a sample pseudo-data generated by a modified version of the LEPTO Monte Carlo event generator that includes the Sivers effect. Using this data it is shown, that the azimuthal correlations in the Sivers-like structure functions and the unpolarized structure functions are significantly different. Collins-like single hadron asymmetries in a dihadron sample are also discussed, for which experimental results were recently presented by the COMPASS collaboration.

Kotzinian, Aram

2014-01-01

381

The Jlab Upgrade - Nucleon Studies with CLAS12

International Nuclear Information System (INIS)

An overview is presented on the program to study the nucleon structure at the 12 GeV Jlab Upgrade using the CLAS12 detector. The focus is on deeply virtual exclusive processes to access the generalized parton distributions, semi-inclusive processes to study transveresx momentum-dependent distributions functions, and inclusive spin structure functions and resonance transition form factors at high Q2 and with high precision

382

The Jlab Upgrade - Nucleon Studies with CLAS12

Energy Technology Data Exchange (ETDEWEB)

An overview is presented on the program to study the nucleon structure at the 12 GeV Jlab Upgrade using the CLAS12 detector. The focus is on deeply virtual exclusive processes to access the generalized parton distributions, semi-inclusive processes to study transveresx momentum-dependent distributions functions, and inclusive spin structure functions and resonance transition form factors at high Q^2 and with high precision.

Volker Burkert

2007-09-05

383

Low x physics, deep inelastic scattering and structure functions

Energy Technology Data Exchange (ETDEWEB)

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 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 ({sigma}{sub pp} - {sigma}{sub pn})/({sigma}{sub pp} + {sigma}{sub 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 Q{sup 2} data from E143 provide a new method to determine the QCD running coupling constant {alpha}{sub 5}. Combining fixed target data from E665 and FNAL and HERA results from H1 and ZEUS, the measurements of the proton structure function F{sub 2}(x,Q{sup 2}) cover the very large kinematic range of 0.3 < Q{sup 2} < 10{sup 4} GeV{sup 2} and 2.10{sup -4} < x < 1. The steep rise of the structure function F{sub 2} with x decreasing is observed at x values below 10{sup -1} and up to Q{sup 2} values of about 1000 GeV{sup 2}. The interpretation of the F{sub 2} 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.

Feltesse, J.

1994-12-31

384

The quark model and the nucleon-nucleon interaction

International Nuclear Information System (INIS)

The quark model and the resonating group method are used to calculate the nucleon-nucleon 3S and 1S phase shifts. The short range part of the N-N interaction is described by quark and gluons exchange between two threequark clusters. For the long range part standard OBE (included only ? and sigma mesons) is used. The form factors of the OBE potential are calculated from the wave function of the three quark clusters using r-dependent quark-meson couplings. This ensures that the mesons couple to the quarks only on the surface region of the nucleons. The calculated phase shifts agree surprisingly well with the data. (orig.)

385

Dans ce mémoire est présentée l'analyse, dans le but de l'extraction des fonctions de structure, d'une partie des données de diffusion profondément inélastique de muons sur cibles fixes d'hydrogène et de detérium obtenues dans l'expérience NMC (New Muon Collaboration) du CERN. Les fonctions de structure, à partir desquelles s'exprime la probabilité de diffusion à un certain angle et une certaine énergie, contiennent de l'information sur la structure interne du nucléon, plus précisément sur la distribution en énergie des quarks à l'intérieur de celui-ci. L'étude de la variation des fonctions de structure avec le degré d'inélasticité de la diffusion permet de tester la validité de la chromodynamique quantique, la théorie de jauge des interactions fortes

Granier, Thierry

386

Search for strongly deformed structures and observation of multiple nucleon alignments in W174

Highly excited states, up to spin 39?, have been established in W174, using the Gammasphere array. Ultimate cranker calculations predict the appearance of triaxial, strongly deformed structures above spin 30? in W174. A new approach was developed for a comprehensive search of the data for such structures, similar to those observed in the Lu and Hf isotopes. No evidence was found for strongly deformed bands in the W isotopes populated in this experiment. Existing rotational structures have been considerably extended, allowing for the observation of both neutron and proton alignments in a number of bands. There is evidence for the i13/2 neutron and possibly both the h9/2 and h11/2 proton crossings. The observed neutron and proton crossing frequencies are in good agreement with predictions of Woods-Saxon cranking calculations using an empirical pair-gap energy, and they lead to an improved understanding of the underlying structure of the bands.

Tandel, S. K.; Knox, A. J.; Parnell-Lampen, C.; Tandel, U. S.; Chowdhury, P.; Carpenter, M. P.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Seweryniak, D.; Wang, X.; Zhu, S.; Hartley, D. J.; Zhang, Jing-Ye

2008-02-01

387

Precision measurement of the neutron spin dependent structure functions

Energy Technology Data Exchange (ETDEWEB)

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.

Kolomensky, Y.G.

1997-02-01

388

Functional Dynamics II : Syntactic Structure

Functional dynamics, introduced in a previous paper, is analyzed, focusing on the formation of a hierarchical rule to determine the dynamics of the functional value. To study the periodic (or non-fixed) solution, the functional dynamics is separated into fixed and non-fixed parts. It is shown that the fixed parts generate a 1-dimensional map by which the dynamics of the functional values of some other parts are determined. Piecewise-linear maps with multiple branches are gen...

Kataoka, N.; Kaneko, K.

1999-01-01

389

Phenomenology of the Electron Structure Function

Advantages of introducing the electron structure function (ESF) in electron induced processes are demonstrated. Contrary to the photon structure function it is directly measured in such processes. At present energies a simultaneous analysis of both the electron and the photon structure functions gives an important test of the experimentally applied methods. Estimates of the ESF at currently measured momenta are given. At very high momenta contributions from $W$ and $Z$ boson...

Slominski, W.; Szwed, J.

2000-01-01

390

Dressing the cloudy bag model: Second-order nucleon-nucleon potential

International Nuclear Information System (INIS)

We calculate the second-order static physical nucleon-nucleon potential resulting from applying a unitary dressing transformation to the trilinear pion-nucleon interaction with cloudy bag model vertex functions. We find that for two physical nucleons separated by any distance greater than twice the bag radius this potential is exactly the usual one-pion exchange potential modified in strength by a factor 1.05 for a bag of radius 0.7 fm

391

Parity violations in high energy nucleon nucleon scattering

International Nuclear Information System (INIS)

It is shown that, using parity violating nucleon wave function effects, large asymmetries in the scattering of polarized nucleons at large energies naturally arise. An immediate consequence of the present model is that the asymmetry at high energy is independent of both target and energy; at moderate energies, by operating in a similar way, one obtains for the asymmetry values of the order of 10-6 and positive, in qualitative agreement with the preliminary experimental results. 7 references

392

International Nuclear Information System (INIS)

The results of a study of heavy-ion induced three-nuclear transfer reactions on 14N, 16O, 17O and 18O, using gas targets and incident energies of about 10 MeV, are reported. Structure calculations, using the nuclear shell model, have been made and energy-levels and multi-nucleon spectroscopic amplitudes, obtained. Theoretical and experimental results have been compared and evaluated. (U.K.)

393

Search for strongly deformed structures and observation of multiple nucleon alignments in 174W

International Nuclear Information System (INIS)

Highly excited states, up to spin 39(?/2?), have been established in 174W, using the Gammasphere array. Ultimate cranker calculations predict the appearance of triaxial, strongly deformed structures above spin 30(?/2?) in 174W. A new approach was developed for a comprehensive search of the data for such structures, similar to those observed in the Lu and Hf isotopes. No evidence was found for strongly deformed bands in the W isotopes populated in this experiment. Existing rotational structures have been considerably extended, allowing for the observation of both neutron and proton alignments in a number of bands. There is evidence for the i13/2 neutron and possibly both the h9/2 and h11/2 proton crossings. The observed neutron and proton crossing frequencies are in good agreement with predictions of Woods-Saxon cranking calculations using an empirical pair-gap energy, and they lead to an improved understanding of the underlying structure of the bands

394

The structure and function of cartilage proteoglycans

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.

Roughley, P. J.

2006-01-01

395

The structure and function of cartilage proteoglycans

Directory of Open Access Journals (Sweden)

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.

P J Roughley

2006-11-01

396

Neutrino-pair bremsstrahlung from nucleon-? versus nucleon-nucleon scattering

We study the impact of the nucleon-? P -wave resonances on neutrino-pair bremsstrahlung. Because of the noncentral spin-orbit interaction, these resonances lead to an enhanced contribution to the nucleon spin structure factor for temperatures T ?4 MeV. If the ? -particle fraction is significant and the temperature is in this range, this contribution is competitive with neutron-neutron bremsstrahlung. This may be relevant for neutrino production in core-collapse supernovae or other dense astrophysical environments. Similar enhancements are expected for resonant noncentral nucleon-nucleus interactions.

Sharma, Rishi; Bacca, Sonia; Schwenk, A.

2015-04-01

397

The Two-Nucleon System in Three Dimensions

A recently developed formulation for treating two- and three-nucleon bound states in a three-dimensional formulation based on spin-momentum operators is extended to nucleon-nucleon scattering. Here the nucleon-nucleon t-matrix is represented by six spin-momentum operators accompanied by six scalar functions of momentum vectors. We present the formulation and provide numerical examples for the deuteron and nucleon-nucleon scattering observables. A comparison to results from a standard partial wave decomposition establishes the reliability of this new formulation.

Golak, J; Skibinski, R; Witala, H; Rozpedzik, D; Topolnicki, K; Fachruddin, I; Elster, Ch; Nogga, A

2010-01-01

398

Functional keratin as structural platforms

Wool with up to 95% keratin by weight is a rich and pure source of proteinous biomaterial. As polymeric polyamide it exhibits high functionality through amide, carboxyl, sulfoxide, sulfide, and thiosulfide functions. Solubilized wool was transformed into keratin morphologies with the unique characte...

399

A study of nuclear effect in $F_3$ structure function in the deep inelastic $\

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.

Athar, M Sajjad; Singh, S K; Vacas, M J Vicente

2009-01-01

400

Measurement of the neutron spin structure function---Test of the Bjorken sum rule

International Nuclear Information System (INIS)

As experiment to measure the neutron spin-dependent structure function g1n (x) over a range in x from 0.04 to 0.7 and with Q2 > 1 (GeV/c)2 is presented. The experiment consists of scattering a longitudinally polarized electron beam from the Stanford Linear Accelerator off a polarized 3He target and detecting scattered electrons in two magnetic spectrometers. The experiment will provide a critical test of the Bjorken sum rule and valuable information in understanding the nucleon spin structure and the violation of the Ellis-Jaffe sum rule. 3 figs., 1 tab

401

Measurement of the neutron spin structure function---Test of the Bjorken sum rule

Energy Technology Data Exchange (ETDEWEB)

As experiment to measure the neutron spin-dependent structure function g{sub 1}{sup n} (x) over a range in x from 0.04 to 0.7 and with Q{sup 2} > 1 (GeV/c){sup 2} is presented. The experiment consists of scattering a longitudinally polarized electron beam from the Stanford Linear Accelerator off a polarized {sup 3}He target and detecting scattered electrons in two magnetic spectrometers. The experiment will provide a critical test of the Bjorken sum rule and valuable information in understanding the nucleon spin structure and the violation of the Ellis-Jaffe sum rule. 3 figs., 1 tab.

Petratos, G.G.

1991-08-01

402

Nuclear structure of 26Al studied by two-nucleon transfer reactions 28Si(d,?) and 24Mg(3He,p)

International Nuclear Information System (INIS)

The differential cross sections for the reactions 28Si(d,?)26Al and 24Mg(3He,p)26Al were measured at the incident energies of 33.0 and 27.5 MeV, respectively, in order to investigate the structure of 26Al in connection with the nuclei 28Si and 24Mg. The angular distributions and the relative magnitudes of the cross sections were analyzed by using the distorted-wave Born approximation theory of the two-nucleon transfer reactions. The shapes of the calculated angular distributions reproduced well the experimental data. The transferred angular momenta L extracted from the angular distributions were consistent with the spins and parities already known. A qualitative picture of the structure of the nucleus 26Al from the data of the relative transition strengths of the two-nucleon transfer reactions was attempted using two simple models of nuclear structure, the Nilsson model with pairing correlations and the simple pairing model of a spherical nucleus. In the former the final state was described by a single configuration of two Nilsson quasiparticles and in the latter, by a single configuration of two quasiparticles in a spherical basis. This Nilsson model showed that the two-nucleon transfer strengths for the low-lying states of 26Al supported the idea that there exist states with opposite signs of the deformation parameter in the low-lying states of 2626Al. The simple pairing model predicted well the overall features of the two-nucleon transfer strengths. This success evolved from the assumption that the final states of 26Al were described separately for stripping to 24Mg and pickup from 28Si by using realistic values of the occupation number probabilities for the shell model orbitals of the respective nuclei. These facts suggest also the existence of states with different character in the 26Al nucleus

403

Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS and CLAS12

Energy Technology Data Exchange (ETDEWEB)

The CLAS detector at Jefferson Lab is a unique instrument, which has provided the lion's share of the world's data on meson photo- and electroproduction in the resonance excitation region. The electroexcitation amplitudes for the low-lying resonances P{sub 33}(1232), P{sub 11}(1440), D{sub 13}(1520), and S{sub 11}(1535) were determined over a wide range of Q{sup 2}<5.0GeV{sup 2} in a comprehensive analysis of exclusive single-meson (?{sup +}n,?{sup 0}p) reactions in the electroproduction off protons. Further, CLAS was able to precisely measure ?{sup +}?{sup ?}p electroproduction differential cross sections provided by the nearly full kinematic coverage of the detector. The electrocouplings of the P{sub 11}(1440) and D{sub 13}(1520) excited states are determined from the exclusive-?{sup +}?{sup ?}p reaction. Consistent results on the electrocouplings from two-independent analyses (single- and double-pion electroproduction) have provided compelling evidence for the reliable extraction of the N{sup ?} electrocouplings. Preliminary results on the electrocouplings of the S{sub 31}(1620), S{sub 11}(1650), D{sub 33}(1700), and P{sub 13}(1720) states have recently become available. Theoretical analyses of these results have revealed that there are two major contributions to the resonance structure: a) an internal quark core and b) an external meson-baryon cloud. These CLAS results have had considerable impact on QCD-based studies on N{sup ?} structure and in the search for manifestations of the dynamical masses of the dressed quarks. Future CLAS12 N{sup ?} structure studies at high photon virtualities will considerably extend our capabilities in exploring the nature of confinement in baryons.

Cole, P.L. [Idaho State University, Department of Physics, Pocatello, Idaho 83209-8106 (United States); Burkert, V.D. [Jefferson Lab., 12000 Jefferson Ave., Newport News, VA 23606 (United States); Gothe, R.W. [University of South Carolina, Department of Physics, Columbia, South Carolina 29208 (United States); Mokeev, V.I. [Jefferson Lab., 12000 Jefferson Ave., Newport News, VA 23606 (United States); Skobeltsyn Nuclear Physics Institute, Moscow State University, 119899 Moscow (Russian Federation)

2012-12-15

404

Energy Technology Data Exchange (ETDEWEB)

The resonance structure of nuclear reaction cross sections in the overlapping resonances region can be described on the basis of a resonance part of the reaction T-matrix by means of a direct resolvent (R/E) calculation and matrix elements (ME) simulation of residual interaction by the random matrix method. Such approach is applied for calculating total cross sections of sigmasub(tot) (E) of /sup 12/C(pn)/sup 12/N reactions at the Esub(p)=15-25 MeV and /sup 12/C(np)/sup 12/B reaction at Esub(n) Esub(n)=15-25 MeV. The calculation is performed at the following approximations: 1. The dependence on energy of average values ME real parts has not been taken into account. 2. The dependence of ME imaginary parts on bombarding nucleon energy has been simulated by increase of their average values by 0.01 MeV with each calculation step sigmasub(tot)(E) (the step has been chosen to be equal 0.2 MeV). 3. The contribution of intermediate pentaquasiparticle configurations has not been taken into account. 4. The basis for the resolvent calculation has been limited (to save calculation time) by states set with maximum number of 10. The calculated sigmasub(tot)(E) has been compared with the experimental data. Satisfactory agreement between theoretical and experimental excitation functions of investigated reactions allows to hope for prospective development of the proposed approach. In contrast to the Hause-Feshbach statistic method the proposed approach makes possible at rather low energies to take into consideration structural properties of individual nuclei determined by single- part levels as well as internucleon interactions giving contribution to ME.

Ol' khovskij, V.S.; Chinarov, V.A. (AN Ukrainskoj SSR, Kiev. Inst. Yadernykh Issledovanij)

1981-11-01

405

International Nuclear Information System (INIS)

The resonance structure of nuclear reaction cross sections in the overlapping resonances region can be described on the basis of a resonance part of the reaction T-matrix by means of a direct resolvent (R/E) calculation and matrix elements (ME) simulation of residual interaction by the random matrix method. Such approach is applied for calculating total cross sections of ?sub(tot) (E) of 12C(pn)12N reactions at the Esub(p)=15-25 MeV and 12C(np)12B reaction at Esub(n) Esub(n)=15-25 MeV. The calculation is performed at the following approximations: 1. The dependence on energy of average values ME real parts has not been taken into account. 2. The dependence of ME imaginary parts on bombarding nucleon energy has been simulated by increase of their average values by 0.01 MeV with each calculation step ?sub(tot)(E) (the step has been chosen to be equal 0.2 MeV). 3. The contribution of intermediate pentaquasiparticle configurations has not been taken into account. 4. The basis for the resolvent calculation has been limited (to save calculation time) by states set with maximum number of 10. The calculated ?sub(tot)(E) has been compared with the experimental data. Satisfactory agreement between theoretical and experimental excitation functions of investigated reactions allows to hope for prospective development of the proposed approach. In contrast to the Hause-Feshbach statistic method the proposed approach makes possible at ratproposed approach makes possible at rather low energies to take into consideration structural properties of individual nuclei determined by single- part levels as well as internucleon interactions giving contribution to ME

406

Photon Structure Function in Supersymmetric QCD Revisited

We investigate the virtual photon structure function in the supersymmetric QCD (SQCD), where we have squarks and gluinos in addition to the quarks and gluons. Taking into account the heavy particle mass effects to the leading order in QCD and SQCD we evaluate the photon structure function and numerically study its behavior for the QCD and SQCD cases.

Sahara, Ryo; Kitadono, Yoshio

2011-01-01

407

Photon structure function in supersymmetric QCD revisited

International Nuclear Information System (INIS)

We investigate the virtual photon structure function in the supersymmetric QCD (SQCD), where we have squarks and gluinos in addition to the quarks and gluons. Taking into account the heavy particle mass effects to the leading order in QCD and SQCD we evaluate the photon structure function and numerically study its behavior for the QCD and SQCD cases.

408

Photon structure function in supersymmetric QCD revisited

Energy Technology Data Exchange (ETDEWEB)

We investigate the virtual photon structure function in the supersymmetric QCD (SQCD), where we have squarks and gluinos in addition to the quarks and gluons. Taking into account the heavy particle mass effects to the leading order in QCD and SQCD we evaluate the photon structure function and numerically study its behavior for the QCD and SQCD cases.

Sahara, Ryo, E-mail: sahara@scphys.kyoto-u.ac.jp [Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa, Kyoto 606-8502 (Japan); Uematsu, Tsuneo, E-mail: uematsu@scphys.kyoto-u.ac.jp [Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa, Kyoto 606-8502 (Japan); Kitadono, Yoshio, E-mail: kitadono@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Taipei, Taiwan (China)

2012-02-07

409

Strangeness in proton and properties of nucleons in nuclear matter revisited

The properties of the nucleons in nuclear medium have been investigated in the context of the flux tube model incorporating strangeness $(s\\bar{s})$ contribution to proton structure in conformity with the experimental indication. Proton is described as a pentaquark system with strange quark contribution whereas neutron is described in three quark configuration. The Quasi particle model of diquark is used to describe the structures of the nucleons. Modifications of the properties like swelling, mass, incompressibility, ratio of the structure functions ($\\frac{F_{2}^{n}(x)}{F_{2}^{p}(x)}$), Gottfried Sum rule for nucleons in nuclear medium have been studied and significant effects have been observed. It has been suggested that the change of the size degree of freedom of the nucleon in the nuclear medium plays an important role in describing the properties in medium. The results are discussed in detail and compared with existing experimental and theoretical predictions. Some interesting observations are made.

Chandar, A; Chakrabarti, B

2013-01-01

410

Twist-2 Generalized TMDs and the Spin/Orbital Structure of the Nucleon

Generalized transverse-momentum dependent parton distributions (GTMDs) encode the most general parton structure of hadrons. Here we focus on two twist-2 GTMDs which are denoted by $F_{1,4}$ and $G_{1,1}$ in parts of the literature. As already shown previously, both GTMDs have a close relation to orbital angular momentum of partons inside a hadron. However, recently even the mere existence of $F_{1,4}$ and $G_{1,1}$ has been doubted. We explain why this claim does not hold. We support our model-independent considerations by calculating the two GTMDs in the scalar diquark model and in the quark-target model, where we also explicitly check the relation to orbital angular momentum. In addition, we compute $F_{1,4}$ and $G_{1,1}$ at large transverse momentum in perturbative Quantum Chromodynamics and show that they are nonzero.

Kanazawa, K; Metz, A; Pasquini, B; Schlegel, M

2014-01-01

411

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

412

Metabolic networks: enzyme function and metabolite structure.

Metabolism is one of the most complex cellular processes. Connections between biochemical reactions via substrate and product metabolites create complex metabolic networks that may be analyzed using network theory, stoichiometric analysis, and information on protein structure/function and metabolite properties. These frameworks take into consideration different aspects of enzyme chemistry, enzyme structure and metabolite structure, and demonstrate the impact of metabolic biochemistry on the systemic properties of metabolism. The integration of these approaches and the systematic classification of enzyme function and the chemical structure of metabolites will enhance our understanding of metabolism, and could improve our ability to predict enzyme function and novel metabolic pathways. PMID:15193309

Hatzimanikatis, Vassily; Li, Chunhui; Ionita, Justin A; Broadbelt, Linda J

2004-06-01

413

The General Structure of Matter

General Classification of Matter; Prequarks and Number of Quarks; Structure of Nucleons; Generation of Quark Masses; Seas and Sizes of Nucleons; Contributions of Nucleons Seas to the Structure Functions; Higgs Bosons; Bosons of the Strong and Superstrong Interactions; The Nature of Gluons, Super QCD, The Energies of Baryons and Mesons; The Sizes of Baryons and Mesons; The Confinement Constant at the Top Quark Scale, The Formation and Evolution of Galaxies; The Formatio...

Souza, Mario Everaldo

2002-01-01

414

The LIGNUM functional-structural tree model

The aim of this thesis was to construct a single tree model that builds a bridge between traditional process based tree models and detailed, three-dimensional architectural tree models. The result of the thesis, the functional-structural tree model LIGNUM, integrates both the functional and the structural aspects of woody arborescent plants in a single generic modelling framework. The thesis consists of five articles and the summary part. The first article presents the model structure of...

Perttunen, Jari

2009-01-01

415

First measurement of the gluon polarisation in the nucleon using D mesons at COMPASS

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...

von Hodenberg, Martin

2005-01-01

416

Structure of the breathing mode of the nucleon from high-energy p-p scattering

International Nuclear Information System (INIS)

Spectra of p-p and ?-p scattering at beam momenta between 6 and 30 GeV/c have been reanalyzed. These show strong excitation of N* resonances, the strongest one corresponding to the 'scalar' P11 excitation (breathing mode) at m0=1400±10 MeV with ?=200±20 MeV. The result of a strong scalar excitation is supported by a large longitudinal amplitude S1/2 extracted from e-p scattering. From exclusive data on p+p?pp?+?-, a large 2?-N decay branch for the P11 resonance of B2?=75±20% has been extracted.The differential cross sections were described in a double-folding approach, assuming multigluon exchange as the dominant part of the effective interaction between the constituents of projectile and target. First, the parameters of the interaction were fitted to elastic scattering; then, with this interaction, the inelastic cross sections were described in the distorted wave Born approximation (DWBA). A good description of the data requires a surface peaked transition density, quite different from that of a pure radial mode. In contrast, the electron scattering amplitude S1/2 is quite well described by a breathing mode transition density with radial node. This large difference between charge and matter transition densities suggests that in p-p scattering the coupling to the multigluon field is much more important than the coupling to the valence quarks. A multigluon (or sea-quark) s. A multigluon (or sea-quark) transition density is derived, which also shows breathing, indicating a rather complex multiquark structure of N and N* including additional multigluon (or q2nq2n) creation out of the ground state vacuum

417

The E142 SLAC experiment: measurement of the neutron gn1(x) spin structure function

International Nuclear Information System (INIS)

This thesis describes the E142 experiment which has been carried out at the Stanford Linear Accelerator (SLAC), USA, from October to December 1992. This experiment of polarized inelastic scattering of a 22.6 GeV electron beam on a polarized helium 3 target has allowed the first measurement of the neutron gn1(x) spin structure function. The knowledge of this structure function gives informations on the nucleon spin structure. On the other hand, the gn1(x) structure function integral value on the 02 mean value of 2 GeV2 after some extrapolations. This value is at about two standard deviations away from the theoretical predictions of the Ellis-Jaffe rule. Thanks to the existing experimental results for the proton (E143 experiment), the Bjorken sum rule has been precisely tested and is perfectly compatible with the theoretical value. The results have allowed to estimate the nucleon spin fraction carried by the quarks. (J.S.). 86 refs., 58 figs., 13 tabs

418

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)

419

International Nuclear Information System (INIS)

Recently measured energy dependences of fission cross sections of lead isotopes 204,206-208Pb at incident nucleon energies up to 180 MeV were analyzed. Regularities were established of the fission cross-section variation with the mass number of isotopes pointing to incomplete dumping of shell effects even at nucleon energies 150-180 MeV. The fission cross sections of lead isotopes, assumed as spherical nuclei, are compared with those of deformed nuclei. The experimental data are compared with calculations by the code TALYS

420

Changes in gastrointestinal tract function and structure in functional dyspepsia.

Functional dyspepsia is an extremely common disorder of gastrointestinal function. The disorder is thought to be heterogeneous, with different pathophysiological mechanisms underlying varied symptom patterns. A diversity of changes in gastrointestinal tract function and structure has been described in functional dyspepsia. These involve alterations in the stomach, such as impaired accommodation, delayed gastric emptying and hypersensitivity, and alterations in the duodenum, such as increased sensitivity to duodenal acid and/or lipids and low-grade inflammation. In this Review, we summarize all these abnormalities in an attempt to provide an integrated overview of the pathophysiological mechanisms in functional dyspepsia. PMID:23318268

Vanheel, Hanne; Farré, Ricard

2013-03-01

421

International Nuclear Information System (INIS)

We discover an inner structure of QED while the gauge potential is decomposed into two orthogonal components. Based on this, the Lagrangian of the electron-photon system is expanded to a new form and by the general method of field theory, the gauge invariant spin and orbital angular momentum operators of the electron and photon are naturally obtained from Noether's theorem. Our method, which can be generalized to the non-Abelian systems to investigate the inner structure of QCD, provides a new perspective to look on the nucleon spin crisis and opens a window into a strict and systematic resolution of this long-standing problem.

422

Energy Technology Data Exchange (ETDEWEB)

Two-particle correlation functions were measured for the emission of protons, deuterons, tritons, {alpha}, and lithium fragment at small relative momenta in {sup 40}Ar-induced reactions on {sup 197}Au at 25 MeV/nucleon. Based on three-body trajectory calculations the emission time scales for the particles were extracted from p-d, d-d, t-t, and lithium-lithium correlation functions.The mean emission time was found to decrease with increasing sum of the kinetic energies of the particle in a correlated pairs, indicating the emission of more energetic particles at earlier stages of the reaction than at later stages. The time scale for the emission of lithium fragments emission suggests that sequential binary disassembly occurs in {sup 40}Ar+{sup 197}Au reaction at MeV/nucleon. The mean emission temperatures of 3.5{sup +1.3}{sub -0.8} and 3.6{+-}0.4 MeV were also extracted from the relative populations of the excited and ground states of the respective emitted nuclides {sup 8}Be and {sup 4}He. (orig.).

He Zhiyong [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Duan Limin [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Jin Genming [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Li Zuyu [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Wu Heyu [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Zhang Baoguo [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Wen Wanxin [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Qi Yujin [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Luo Qingzheng [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.; Dai Guangxi [Chinese Acad. of Sci., Lanzhou (China). Inst. of Modern Phys.

1997-07-07

423

International Nuclear Information System (INIS)

Two-particle correlation functions were measured for the emission of protons, deuterons, tritons, ?, and lithium fragment at small relative momenta in 40Ar-induced reactions on 197Au at 25 MeV/nucleon. Based on three-body trajectory calculations the emission time scales for the particles were extracted from p-d, d-d, t-t, and lithium-lithium correlation functions.The mean emission time was found to decrease with increasing sum of the kinetic energies of the particle in a correlated pairs, indicating the emission of more energetic particles at earlier stages of the reaction than at later stages. The time scale for the emission of lithium fragments emission suggests that sequential binary disassembly occurs in 40Ar+197Au reaction at MeV/nucleon. The mean emission temperatures of 3.5+1.3-0.8 and 3.6±0.4 MeV were also extracted from the relative populations of the excited and ground states of the respective emitted nuclides 8Be and 4He. (orig.)

424

Lepton Scattering Cross Section and Nuclear Structure Function of 4He and 12C Nuclei

Directory of Open Access Journals (Sweden)

Full Text Available This paper is an effort to extract the structure function, the EMC ratio, and the lepton scattering cross section in the convolution nuclear theory framework for 4He and 12C nuclei. We suppose that, in conventional approach, based on harmonic oscillator model, one could consider for a nucleus shell different hw parameters which are associated with the square root of the mean radius of the nucleus shells. We use GRV free nucleon structure function, which has good agreement with the proton and neutron structure function, extracted from experimental results. In addition, the lepton scattering cross sections of 4He and 12C nuclei are calculated in energy higher than 1 GeV. The extracted results show good agreement with experimental data.

Mir Hamid Musavi

2013-10-01

425

Third-order QCD corrections to the charged-current structure function F3

International Nuclear Information System (INIS)

We compute the coefficient function for the charge-averaged W±-exchange structure function F3 in deep-inelastic scattering (DIS) to the third order in massless perturbative QCD. Our new three-loop contribution to this quantity forms, at not too small values of the Bjorken variable x, the dominant part of the next-to-next-to-next-to-leading order corrections. It thus facilitates improved determinations of the strong coupling ?s and of 1/Q2 power corrections from scaling violations measured in neutrino-nucleon DIS. The expansion of F3 in powers of ?s is stable at all values of x relevant to measurements at high scales Q2. At small x the third-order coefficient function is dominated by diagrams with the colour structure dabcdabc not present at lower orders. At large x the coefficient function for F3 is identical to that of F1 up to terms vanishing for x?1. (orig.)

426

Metallothioneins: new functional and structural insights.

In the past few years, tissue-specific mammalian metallothioneins (i. e. metallothionein-3 and metallothionein-4) have been discovered that possess distinct functional properties. Other recent developments include an insight into the role of the widely expressed mammalian metallothionein-1 and metallothionein-2 isoforms in zinc homeostasis and apoptosis. The three-dimensional structure of the evolutionary distant sea urchin Cd(7)-metallothionein A, which contains two metal-thiolate clusters, supports previous conclusions regarding the functional importance of this structural motif. Despite correlated efforts involving techniques of structural biochemistry and molecular biology, the primary function of metallothioneins remains enigmatic. PMID:10742189

Vasák, M; Hasler, D W

2000-04-01

427

Nucleon nucleon potential using Dirac constraint dynamics

International Nuclear Information System (INIS)

The relativistic potential concept is fostered for the description of nucleon-nucleon (NN) interactions and scattering for energies 0 Lab ? 3 GeV. It proves useful to confirm and predict nuclear properties and reactions with the implicit knowledge having the best possible agreement with experimental NN data. Medium energy NN scattering, as is accepted for low energy nuclear physics in general, is determined from proton, nucleon and meson degrees of freedom in the long range soft interaction sector, the quark gluon degrees of freedom govern the short distance hard processes. The identification and parameterization, of the combined long and short range NN domains, is the topic of this thesis. The formalism for two coupled Dirac equations, within constraint instant form dynamics, is used to study the NN interaction. The comprehensive review, of the important theoretical tools and associated mathematics, rests essentially on the work of Crater and Van Alstine. The reduction of the coupled Dirac equations into Schroedinger type equations is given. Explicitly energy dependent coupled channel potentials, for use in partial wave Schroedinger like equations, with nonlinear and complicated derivative terms, result. We developed the necessary numerics and study np and pp scattering phase shifts for energies 0 to 3 GeV and the deuteron bound state. The interactions are inspired by meson exchange of ?, ?, ?, ? and ? mesons for which we adjust coupling constantr which we adjust coupling constants. This yields, in the first instant, high quality fits to the Arndt phase shifts 0 to 300 MeV. Second, the potentials show a universal, independent from angular momentum, core potential which is generated with the relativistic meson exchange dynamics. Extrapolations towards higher energies, up to TLab equal 3 GeV, allow to separate a QCD dominated short range zone as well as inelastic nucleon excitation mechanism contributing to meson production. A local or nonlocal optical model, in addition to the meson exchange Dirac potential, produces agreement between theoretical and phase shifts data. The optical model potentials reflect a short lived complex multi hadronic intermediate structure formation of which the optical model parameters give a consistent picture. For future work, the here presented phenomenological access encourages a more microscopic and detailed use of QCD, including explicit ?(3, 3) pair formation and some obviously predominant other pair mechanism. (orig.)

428

Preasymptotic effects in nucleon-nucleon large-angle scattering

International Nuclear Information System (INIS)

The preasymptotic behaviour of nucleon-nucleon elastic amplitudes has been studied in the limit of a high-energy quasipotential large-angle scattering. The assumption that the interaction is charge-independent makes it possible to describe both reactions of elastic pp- and pn-scattering at a time using the same parameters. The corresponding helical amplitudes are obtained, with taking account of the correction terms of the first and second orders with respect to l/p, where p is the momentum of colliding particles in the center-of-mass system. The preasymptotic effects in the nucleon-nucleon large-angle scattering considered are typical for that range of energies and momentum transfers where the dynamics of scattering is already defined by the interaction of hadron point components at small distances, but at the same time the effects connected with the hadron structure as a whole, i.e., with large distances, are essential. By the order of magnitude they are such that the account made of them in analyzing and interpreting the experimental data available at present with respect to nucleon-nucleon larle-angle scattering is undoubtedly necessary

429

International Nuclear Information System (INIS)

This report outlines the progress made in the past 15 months toward completion of a long-term pion-nucleon partial wave analysis in collaboration with R.E. Cuthosky at Carnegie-Mellon University. The report details other theoretical work done during this time period, including work on the Table of Particle Properties, 1982

430

International Nuclear Information System (INIS)

This report details progress toward completion of a long-term pion-nucleon partial wave analysis, summarizing results and conclusions to date. The report also discussed progress in using partial wave and resonance parameter results to test dynamical models of the baryon and in better understanding interquark forces within baryons

431

Energy Technology Data Exchange (ETDEWEB)

This report details progress toward completion of a long-term pion-nucleon partial wave analysis, summarizing results and conclusions to date. The report also discussed progress in using partial wave and resonance parameter results to test dynamical models of the baryon and in better understanding interquark forces within baryons.

Hendrick, R.E.

1981-01-10

432

Energy Technology Data Exchange (ETDEWEB)

This report outlines the progress made in the past 15 months toward completion of a long-term pion-nucleon partial wave analysis in collaboration with R.E. Cuthosky at Carnegie-Mellon University. The report details other theoretical work done during this time period, including work on the Table of Particle Properties, 1982.

1982-08-31

433

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

434

Electronic structure tuning of diamondoids through functionalization

We investigated the changes in electronic structures induced by chemical functionalization of the five smallest diamondoids using valence photoelectron spectroscopy. Through the variation of three parameters, namely functional group (thiol, hydroxy, and amino), host cluster size (adamantane, diamantane, triamantane, [121]tetramantane, and [1(2,3)4]pentamantane), and functionalization site (apical and medial) we are able to determine to what degree these affect the electronic structures of the overall systems. We show that unlike, for example, in the case of halobenzenes, the ionization potential does not show a linear dependence on the electronegativity of the functional group. Instead, a linear correlation exists between the HOMO-1 ionization potential and the functional group electronegativity. This is due to localization of the HOMO on the functional group and the HOMO-1 on the diamondoid cage. Density functional theory supports our interpretations.

Rander, Torbjörn; Staiger, Matthias; Richter, Robert; Zimmermann, Tobias; Landt, Lasse; Wolter, David; Dahl, Jeremy E.; Carlson, Robert M. K.; Tkachenko, Boryslav A.; Fokina, Natalie A.; Schreiner, Peter R.; Möller, Thomas; Bostedt, Christoph

2013-01-01

435

Determination of the gluon distribution in the nucleon from deep inelastic neutrino scattering

International Nuclear Information System (INIS)

The observed scaling violations of the nucleon structure functions F2 and anti q have been analysed in the framework of perturbative QCD to determine the shape and magnitude of the gluon distribution. The data are in good agreement with leading order QCD, and the simultaneous use of F2 and anti q structure functions permits, for the first time, a reliable determination of the gluon structure function. (orig.)

436

International Nuclear Information System (INIS)

In CTa collisions at 4.2 GeV/c per nucleon we analyze the characteristics of protons with momentum p> or =0.7 GeV/c and certain properties of ?- mesons as functions of the cumulative variable ?0. We observe emission of protons with values of the variable ?0>1, and in the region ?0approx.1 the dependence of the proton characteristics and also the ?--meson accompaniment as a function of ?0 changes qualitatively. The experimental results are compared with the predictions of the cascade model. The model satisfactorily describes the average characteristics of particles accompanying the emission of the cumulative proton, but in the cumulative region ( ?0> or approx. =1) it does not agree with the experimental average characteristics of the protons having the largest value of ?0 in an event

437

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

438

The three-dimensional nucleon structure is central to many theoretical and experimental activities, and research in this field has seen many advances in the last two decades, addressing fundamental questions such as the orbital motion of quarks and gluons inside the nucleons, their spatial distribution, and the correlation between spin and intrinsic motion. A real three-dimensional imaging of the nucleon as a composite object, both in momentum and coordinate space, is slowly emerging. This book presents lectures and seminars from the Enrico Fermi School: Three-Dimensional Partonic Structure of the Nucleon, held in Varenna, Italy, in June and July 2011. The topics covered include: partonic distributions, fragmentation functions and factorization in QCD; theory of transverse momentum dependent partonic distributions (TMDs) and generalized partonic distributions (GPDs); experimental methods in studies of hard scattering processes; extraction of TMDs and GPDs from data; analysis tools for azimuthal asymmetries; ...

Avakian, H; Hasch, D; Schweitzer, P

2012-01-01

439

Measurement of the deuteron elastic structure functions at large momentum transfers

Energy Technology Data Exchange (ETDEWEB)

The cross section for elastic electron-deuteron scattering has been measured using the Hall A Facility of Jefferson Laboratory. Scattered electrons and recoiling deuterons were detected in coincidence in the two 4 GeV/c High Resolution Spectrometers (HRS) of Hall A. The deuteron elastic structure functions A(Q{sup 2}) and B(Q{sup 2}) have been extracted from these data. Results for the measurement of A(Q{sup 2}) in the range of 0.7 ? Q{sup 2} ? 6.0 (GeV/c){sup 2} are reported. Results for the magnetic structure function, B(Q{sup 2}), are presented in the range of 0.7 ? Q{sup 2} ? 1.35 (GeV/c){sup 2}. The results for both structure functions are compared to predictions of meson-nucleon based models, both with and without the inclusion of meson-exchange currents. The A(Q{sup 2}) results are compared to predictions of the dimensional scaling quark model and perturbative quantum chromodynamics. The results can provide insights into the transition from meson-nucleon to quark-gluon descriptions of the nuclear two-body system.

Kathy McCormick

1999-08-01

440

Four RNA families with functional transient structures.

Protein-coding and non-coding RNA transcripts perform a wide variety of cellular functions in diverse organisms. Several of their functional roles are expressed and modulated via RNA structure. A given transcript, however, can have more than a single functional RNA structure throughout its life, a fact which has been previously overlooked. Transient RNA structures, for example, are only present during specific time intervals and cellular conditions. We here introduce four RNA families with transient RNA structures that play distinct and diverse functional roles. Moreover, we show that these transient RNA structures are structurally well-defined and evolutionarily conserved. Since Rfam annotates one structure for each family, there is either no annotation for these transient structures or no such family. Thus, our alignments either significantly update and extend the existing Rfam families or introduce a new RNA family to Rfam. For each of the four RNA families, we compile a multiple-sequence alignment based on experimentally verified transient and dominant (dominant in terms of either the thermodynamic stability and/or attention received so far) RNA secondary structures using a combination of automated search via covariance model and manual curation. The first alignment is the Trp operon leader which regulates the operon transcription in response to tryptophan abundance through alternative structures. The second alignment is the HDV ribozyme which we extend to the 5' flanking sequence. This flanking sequence is involved in the regulation of the transcript's self-cleavage activity. The third alignment is the 5' UTR of the maturation protein from Levivirus which contains a transient structure that temporarily postpones the formation of the final inhibitory structure to allow translation of maturation protein. The fourth and last alignment is the SAM riboswitch which regulates the downstream gene expression by assuming alternative structures upon binding of SAM. All transient and dominant structures are mapped to our new alignments introduced here. PMID:25751035

Zhu, Jing Yun A; Meyer, Irmtraud M

2015-01-01

441

RANGELAND COMMUNITIES: STRUCTURE, FUNCTION, AND CLASSIFICATION

Determining the vegetational attributes of rangelands is critical to their management. Yet incorporating vegetation structure, function, and classification into a single chapter is an ambitious goal and an attempt to blur the boundaries between classical community ecology that characterize patterns...

442

Snake Jaws: Connecting Structure and Function

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.

WGBH Educational Foundation

2010-12-14

443

A NEW METHOD FOR EXTRACTING SPIN-DEPENDENT NEUTRON STRUCTURE FUNCTIONS FROM NUCLEAR DATA

Energy Technology Data Exchange (ETDEWEB)

High-energy electrons are currently the best probes of the internal structure of nucleons (protons and neutrons). By collecting data on electrons scattering off light nuclei, such as deuterium and helium, one can extract structure functions (SFs), which encode information about the quarks that make up the nucleon. Spin-dependent SFs, which depend on the relative polarization of the electron beam and the target nucleus, encode quark spins. Proton SFs can be measured directly from electron-proton scattering, but those of the neutron must be extracted from proton data and deuterium or helium-3 data because free neutron targets do not exist. At present, there is no reliable method for accurately determining spin-dependent neutron SFs in the low-momentum-transfer regime, where nucleon resonances are prominent and the functions are not smooth. The focus of this study was to develop a new method for extracting spin-dependent neutron SFs from nuclear data. An approximate convolution formula for nuclear SFs reduces the problem to an integral equation, for which a recursive solution method was designed. The method was then applied to recent data from proton and deuterium scattering experiments to perform a preliminary extraction of spin-dependent neutron SFs in the resonance region. The extraction method was found to reliably converge for arbitrary test functions, and the validity of the extraction from data was verifi ed using a Bjorken integral, which relates integrals of SFs to a known quantity. This new information on neutron structure could be used to assess quark-hadron duality for the neutron, which requires detailed knowledge of SFs in all kinematic regimes.

Kahn, Y.F.; Melnitchouk, W.

2009-01-01

444

Sensitivity Analysis for Functional Structural Plant Modelling

Global sensitivity analysis has a key role to play in the design and parameterization of functional-structural plant growth models (FSPM) which combine the description of plant structural development (organogenesis and geometry) and functional growth (biomass accumulation and allocation). Models of this type generally describe many interacting processes, count a large number of parameters, and their computational cost can be important. The general objective of this thesis is to develop a prop...

Wu, Qiongli

2012-01-01

445

Structural and Functional Brain Abnormalities in Schizophrenia

Schizophrenia is associated with changes in the structure and functioning of a number of key brain systems, including prefrontal and medial temporal lobe regions involved in working memory and declarative memory, respectively. Imaging techniques provide an unparalleled window into these changes, allowing repeated assessments across pre- and post-onset stages of the disorder and in relation to critical periods of brain development. Here we review recent directions in structural and functional ...

Karlsgodt, Katherine H.; Sun, Daqiang; Cannon, Tyrone D.

2010-01-01

446

A Cook Book of Structure Functions

The structure function is a useful quantity to characterize wavefront distortions. We derive expressions for the structure functions of the averaged wavefront phase and slopes. The expressions are valid within the inertial range of atmospheric turbulence, and are meant to serve as engineering formulae when reconstructing profiles of the atmospheric turbulence, specifically in the context of atmospheric profiling instruments (e.g. SLODAR and S-DIMM+) and multi-conjugate adaptive optical systems.

Kellerer, Aglae

2015-01-01

447

International Nuclear Information System (INIS)

A new method to extract asymmetries and spin-dependent structure functions is proposed. The method is based on the exact formulae for differences of cross-sections for deep inelastic scattering of polarized leptons on polarized nucleons with spins parallel and antiparallel to each other. A special likelihood procedure taking into account dynamical variations of beam and target polarizations as well as peculiarities of data taking and processing, has been developed

448

Moments of the Proton F2 Structure Function at Low Q2

The Q^2 dependence of inclusive electron-proton scattering F_2 structure function data in both the nucleon resonance region and the deep inelastic region, at momentum transfers below 5 (GeV/c)^2, is investigated. Moments of F_2 are constructed, down to momentum transfers of Q^2 ~ 0.1 (GeV/c)^2. The second moment is only slowly varying with Q^2 down to Q^2 ~ 1 (GeV/c)^2, which is a reflection of duality. Below Q^2 of 1 (GeV/c)^2, the Q^2 dependence of the moments is predomina...

Armstrong, C. S.; Ent, R.; Keppel, C. E.; Liuti, S.; Niculescu, G.; Niculescu, I.

2001-01-01

449

Direct observation of quark-hadron duality in the free neutron F_2 structure function

Using data from the recent BONuS experiment at Jefferson Lab, which utilized a novel 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 F_2 structure function. The data are used to reconstruct the lowest few (N=2, 4 and 6) moments of F_2 in the three prominent nucleon resonance regions, as well as the moments integrated over the entire resonance reg...

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.

2015-01-01

450

Local duality in spin structure functions g1(p) and g1(d)

International Nuclear Information System (INIS)

Inclusive double spin asymmetries obtained by scattering polarized electrons off polarized protons and deuterons have been analyzed to address the issue of quark hadron duality in the polarized spin structure functions gp 1 and gd 1. A polarized electron beam, solid polarized NH3 and ND3 targets and the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B were used to collect the data. The resulting gp 1 and gd 1 were averaged over the nucleon resonance energy region (M < W <2.00 Gev), and three lowest lying resonances individually for tests of global and local duality

451

Measurement of the neutron F2 structure function via spectator tagging with CLAS

We report on the first measurement of the F2 structure function of the neutron from semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to < 100 MeV and their angles to < 100 degrees relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F2n data collected cover the nucleon resonance a...

Baillie, N.; Tkachenko, S.; Zhang, J.; Bosted, P.; Bultmann, S.; Christy, M. E.; Fenker, H.; Griffioen, K. A.; Keppel, C. E.; Kuhn, S. E.; Melnitchouk, W.; Tvaskis, V.; Adhikari, K. P.; Adikaram, D.; Aghasyan, M.

2011-01-01

452

Measurement of the charm structure function and its role in scale noninvariance

International Nuclear Information System (INIS)

From a sample of 20072 dimuon final states, a first determination of the structure function F2(cc-bar) for diffractive charmed-quark pair production by 209-GeV muons is obtained. F2(cc-bar) has a ? dependence similar to that of the photon-gluon fusion model, but its Q2 dependence peaks at lower Q2. Diffractive charm production accounts for approx.1/3 of the scale noninvariance observed in muon-nucleon scattering at low values of the Bjorken x variable, x/sub B/

453

2004 Structural, Function and Evolutionary Genomics

Energy Technology Data Exchange (ETDEWEB)

This Gordon conference will cover the areas of structural, functional and evolutionary genomics. It will take a systematic approach to genomics, examining the evolution of proteins, protein functional sites, protein-protein interactions, regulatory networks, and metabolic networks. Emphasis will be placed on what we can learn from comparative genomics and entire genomes and proteomes.

Douglas L. Brutlag Nancy Ryan Gray

2005-03-23

454

Nucleon properties inside compressed nuclear matter

Our model calculations performed in the frame of the Bag Model (BM) approach show the modifications of nucleon mass, nucleon radius and a Parton Distribution Function (PDF) in Nuclear Matter (NM) above the saturation point. They originated from the pressure correction to the nucleon rest energy. Similar correction leads to conservation of a nuclear longitudinal momenta - essential in the explanation of the EMC effect at the saturation point of NM. Presented finite pressure corrections are generalization of the Hugenholtz-van Hove theorem valid for finite nucleon sizes inside NM.

Rozynek, Jacek

2014-01-01

455

Charge-dependent three-nucleon potential

International Nuclear Information System (INIS)

The charge-dependent three-nucleon potential due to simultaneous photon and pion exchange was derived. The intermediate state of the three-nucleon system was considered to consist of a ?(1236) resonance. The contribution of this charge-dependent three-nucleon potential to the charge asymmetric energy of 3He-3H is then evaluated using a reasonable trial wave function for a three- nucleon bound system. This contribution turns out to be small but makes the charge asymmetric energy of 3He-3H slightly larger. (orig.)

456

The quark model and the nature of the repulsive core of the nucleon-nucleon interaction

International Nuclear Information System (INIS)

The nature of the repulsive core of the nucleon-nucleon is studied in the quark model. The resonating group equation for nucleon-nucleon scattering is solved with the colour Fermi-Breit interaction including further a linear or quadratic confinement potential. It is shown that the colour magnetic interaction which is adjusted to the ?-nucleon mass splitting favours the orbital symmetry and disfavours the completely symmetric orbital state. For the important orbital symmetry the relative S wave function between the two nucleons has to have a node. In the framework of the resonating group including the NN, ?? and the hidden colour (CC) channels it is shown that this node produces a 3S and 1S phase shift which is identical to a hard core phase shift with a hard core radius ?0 between 0.3 and 0.6 fm depending on the assumed root mean square radius of the quark part of the nucleon. (orig./HSI)

457

Quark Correlations in Nucleons and Nuclei

A dynamical quark model of hadron and nucleus structure is proposed. In the frame of the model, called the Strongly Correlated Quark Model, quarks and nucleons inside nuclei are arranged in a crystal--like structure.

Musulmanbekov, G.

2003-01-01

458

The melanins: robust functionality through structural disorder

International Nuclear Information System (INIS)

Full text: The melanins are a class of functional macromolecule found throughout the biosphere. In humans they are mainly responsible for photo-protection and pigmentation. They have a remarkable set of physio-chemical properties; for example, in the condensed solid state they are electrical conductors and photoconductors. In my talk I will discuss the structure-property-function relationships of these unique bio-macromolecules. I will present spectroscopic evidence, quantum chemical simulations and solid state measurements which all show that melanins may be a unique example of a biological system where function is derived from chemical and structural disorder. Copyright (2005) Australian Institute of Physics

459

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)

460

A higher-dimensional model of the nucleon-nucleon central potential

Based on a theory of extra dimensional confinement of quantum particles [E. R. Hedin, Physics Essays, 2012, 25(2): 177], a simple model of a nucleon-nucleon (NN) central potential is derived which quantitatively reproduces the radial profile of other models, without adjusting any free parameters. It is postulated that a higher-dimensional simple harmonic oscillator confining potential localizes particles into three-dimensional (3D) space, but allows for an evanescent penetration of the particles into two higher spatial dimensions. Producing an effect identical with the relativistic quantum phenomenon of zitterbewegung, the higher-dimensional oscillations of amplitude ?/( mc) can be alternatively viewed as a localized curvature of 3D space back and forth into the higher dimensions. The overall spatial curvature is proportional to the particle's extra-dimensional ground state wave function in the higher-dimensional harmonic confining potential well. Minimizing the overlapping curvature (proportional to the energy) of two particles in proximity to each other, subject to the constraint that for the two particles to occupy the same spatial location one of them must be excited into the 1 st excited state of the harmonic potential well, gives the desired NN potential. Specifying only the nucleon masses, the resulting potential well and repulsive core reproduces the radial profile of several published NN central potential models. In addition, the predicted height of the repulsive core, when used to estimate the maximum neutron star mass, matches well with the best estimates from relativistic theory incorporating standard nuclear matter equations of state. Nucleon spin, Coulomb interactions, and internal nucleon structure are not considered in the theory as presented in this article.

Hedin, Eric R.

2014-04-01