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1

Nucleon structure functions  

International Nuclear Information System (INIS)

In this talk I summarize ideas and plans which have been put forward by members of all collaborations running muon or neutrino experiments at CERN. During our discussions there was general agreement that: i) substantial improvements of structure function measurements in the SPS range are still possible and necessary and ii) it is the responsibility of the present groups and of CERN to provide a ''final'' set of structure functions in the present energy range. (orig.)

2

Influence of temperature on nucleon structure functions  

Science.gov (United States)

A simple statistical approach is performed to calculate the nucleon structure functions F2 and xF3 in the kinematic range 0.05change 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

3

Nucleon Structure Functions and Nuclear DIS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

4

Chiral Symmetry and the Nucleon Structure Functions  

CERN Document Server

The isospin asymmetry of the sea quark distribution as well as the unexpectedly small quark spin fraction of the nucleon are two outstanding discoveries recently made in the physics of deep-inelastic structure functions. We evaluate here the corresponding quark distribution functions within the framework of the chiral quark soliton model, which is an effective quark model of baryons maximally incorporating the most important feature of low energy QCD, i.e. the chiral symmetry and its spontaneous breakdown. It is shown that the model can explain qualitative features of the above-mentioned nucleon structure functions within a single framework, thereby disclosing the importance of chiral symmetry in the physics of high energy deep-inelastic scatterings.

Wakamatsu, M; Wakamatsu, Masashi; Kubota, Takanori

1998-01-01

5

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/

6

A nonextensive statistical model for the nucleon structure function  

International Nuclear Information System (INIS)

We studied an application of nonextensive thermodynamics to describe the structure function of nucleon, in a model where the usual Fermi–Dirac and Bose–Einstein energy distribution were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and two chemical potentials given by the corresponding up (u) and down (d) quark normalizations in the nucleon. (author)

7

Polarized structure functions of the nucleon in the resonance region  

International Nuclear Information System (INIS)

Aspects of the spin structure functions of proton and neutrons at low mentum transfer Q2 and energy transfer ?, i.e. in the region of the nucleon resonances are discussed. Experiments to measure A1p, A2p and A11n structure functions at CEBAF in a Q2 range from 0.15 to 2.0 GeV2, and a W range from threshold to 2.2 GeV are presented

8

Structure functions of the nucleon and their interpretation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The current status of measurements of the nucleon structure functions and their understanding is reviewed. The fixed target experiments E665, CCFR and NMC and the HERA experiments HI and ZEUS are discussed in some detail. The extraction of parton momentum distribution functions from global fits is described, with particular attention paid to much improved information on the gluon momentum distribution. The status of ? s measurements from deep inelastic data is revi...

Cooper-sarkar, Am; Devenish, Rce; Roeck, A.

1998-01-01

9

Spin And Nuclear Effects In Nucleon Structure Function  

International Nuclear Information System (INIS)

Full text: The two experimental results on the structure functions of the nucleon obtained by the European muon collaboration (EMC) from the experiments on deep inelastic scattering of muons on nuclear and scattering of polarized muons on polarized nucleons have become a source of great confusion. From these data the surprising and counter- intuitive results have been obtained indicating that quark distribution in nuclear nucleon is much different than in that free nucleon (so-called nuclear EMC effect) and the total projection of the spin of all quarks and antiquarks in the direction of the spin of the polarized nucleon is close to zero (so-called spin crisis). It is shown that the suppression of soft-gluon emission in the evolution of the nonsinglet structure function of a nucleon within a nucleus describes to a certain extent the EMC effect. High order corrections to the photon polarization degree due to radiative emissions at longitudinal polarized deep inelastic lepton-nucleon scattering are calculated in the framework of the structure-function formalism. We consider the changing of polarization degree of the virtual photon due to the initial state radiation of real photons at longitudinal polarized lepton-nucleon scattering. Usually the photon depolarization factor is taken into account only in low order of perturbative theory. To take into account the radiative correction we used the structure function method for the polarization case. The Born cross section atlarization case. The Born cross section at deep-inelastic lepton-nucleon scattering is modified due to additional real and virtual bosons from either the lepton or quark line. The quarkonic corrections are absorbed into quark structure function, like the gluon radiation, whereas corrections from interference between the lepton and quark line proved to be small. The dominant contribution to the virtual corrections is the vertex corrections and the vacuum polarization. In leading logarithmical approximation, the emitted real photon is collinear with initial (final) lepton. The radiative corrections (RC) change the kinematics of the events. We find that the RC changes the structure of depolarization factor and there is big difference between low and high order at small value of energy fraction of the virtual photon. Therefore, it is necessary to use the expression of photon depolarization factor in high order. It has been shown that the associate production of a J/? meson and a photon at polarized proton-proton collisions can serve as a very clean probe of the gluon polarization. It presents the calculations of the differential cross section for the production with a high transverse momentum of J/? (Jpc = 1--) meson accompanied by the hard photon at the CERN in Large Hadron Collider (LHC) proton-proton (pp) collisions at the energy ?s =14 TeV : p+p = J/?+?+X. In low order J/? meson and photon in the final state with high transverse momenta can only be produced via QCD gluon fusion: g+g = J/?+?. The associated production of a J/? meson and a photon at the LHC energy should not be dominated by fragmentation contributions up to transverse momentum pt values of 50 GeV. This should be due to the fact that quark-antiquark (qq- ) initial states are suppressed at the CERN LHC energy. We use the following cuts: pt?40 GeV. The method to extract the gluon structure function can be based on fitting the J/?-? cross section to the predictions. (authors)

10

A measurement of the ratio of the nucleon structure function in copper and deuterium  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function, F2, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects.

Ashman, J.; Badelek, B.; Baum, Gu?nter; Beaufays, J.; Bee, C. P.; Benchouk, C.; Bird, I. G.; Brown, S. C.; Caputo, M. C.; Cheung, H. W. K.; Chima, J.; Ciborowski, J.; Clifft, R. W.; Coignet, G.; Combley, F.

1993-01-01

11

A measurement of the ratio of the nucleon structure function in copper and deuterium  

International Nuclear Information System (INIS)

Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function, F2, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects. (orig.)

12

Chiral Quark Soliton Model and Nucleon Spin Structure Functions  

CERN Document Server

The chiral quark soliton model (CQSM) is one of the most successful models of baryons at quark level, which maximally incorporates the most important feature of low energy QCD, i.e. the chiral symmetry and its spontaneous breakdown. Basically, it is a relativistic mean-field theory with full account of infinitely many Dirac-sea quarks in a rotational-symmetry-breaking mean field of hedgehog shape. The numerical technique established so far enables us to make a nonperturbative evaluation of Casimir effects (i.e. effects of vacuum-polarized Dirac sea) on a variety of baryon observables. This incompatible feature of the model manifests most clearly in its predictions for parton distribution functions of the nucleon. In this talk, after briefly reviewing several basic features of the CQSM, we plan to demonstrate in various ways that this unique model of baryons provides us with an ideal tool for disentangling nonperturbative aspect of the internal partonic structure of the nucleon, especially the underlying spin ...

Wakamatsu, M

2009-01-01

13

Chiral Symmetry and the Nucleon Spin Structure Functions  

CERN Document Server

We carry out a systematic investigation of twist-two spin dependent structure functions of the nucleon within the framework of the chiral quark soliton model (CQSM) by paying special attention to the role of chiral symmetry of QCD. The importance of chiral symmetry is illustrated through the good reproduction of the recent SLAC data for the neutron spin structure function $g_1^n (x,Q^2)$. We also observe substantial difference between the predictions of the longitudinally polarized distribution functions and those of the transversity distribution functions. That the chiral symmetry may be responsible for this difference is seen in the isospin dependence of the corresponding first moments, i.e. the axial and tensor charges. The CQSM predicts $g_A^{(0)} / g_A^{(3)} \\simeq 0.25$ for the ratio of the isoscalar to isovector axial charges, while $g_T^{(0)} / g_T^{(3)} \\simeq 0.46$ for the ratio of the isoscalar to isovector tensor charges, which should be compared with the prediction $g_A^{(0)} / g_A^{(3)} = g_T^{(...

Wakamatsu, M; Wakamatsu, Masashi; Kubota, Takanori

1999-01-01

14

Chiral Symmetry and the Nucleon Spin Structure Functions  

CERN Document Server

We carry out a systematic investigation of twist-two spin dependent structure functions of the nucleon within the framework of the chiral quark soliton model (CQSM) by paying special attention to the role of chiral symmetry of QCD. We observe a substantial difference between the predictions of the longitudinally polarized distribution functions and the transversity distribution ones. That the chiral symmetry is responsible for this difference can most clearly be seen in the isospin dependence of the corresponding first moments, i.e. the axial and tensor charges. The CQSM predicts $g_A^{(0)} / g_A^{(3)} \\simeq 0.25$ for the ratio of the isoscalar to isovector axial charges, and $g_T^{(0)} / g_T^{(3)} \\simeq 0.46$ for the ratio of the isoscalar to isovector tensor charges, which should be compared with the prediction of the naive (non-chiral) MIT bag model, $g_A^{(0)} / g_A^{(3)} = g_T^{(0)} / g_T^{(3)} = 3 / 5$.

Wakamatsu, M

1998-01-01

15

A measurement of the ratio of the nucleon structure function in copper and deuterium  

Energy Technology Data Exchange (ETDEWEB)

Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function, F[sub 2], is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects. (orig.).

Ashman, J.; Combley, F.; Salmon, D. (Sheffield Univ. (United Kingdom). Dept. of Physics); Badelek, B.; Ciborowski, J.; Gajewski, J.; Rondio, E.; Ropelewski, L. (Warsaw Univ. (Poland). Inst. of Physics); Baum, G.; Caputo, M.C.; Hughes, V.W.; Oppenheim, R.F.; Papavassiliou, V.; Piegaia, R.; Schueler, K.P. (Yale Univ., New Haven, CT (United States). Dept. of Physics); Beaufays, J.; Jacholkowska, A.; Niinikowski, T.; Osborne, A.M.; Rieubland, J.M. (European Organization for Nuclear Research, Geneva (Switzerland)); Bee, C.P.; Brown, S.C.; Court, G.; Francis, D.; Gabathuler, E.; Gamet, R.; Hayman, P.; Holt, J.R.; Jones, T.; Matthews, M.; Wimpenny, S.J. (Liverpool Univ. (United Kingdom). Dept. of Physics); Benchouk, C.; D' Agostini, G.; Montanet, F.; Pietrzyk, B. (Aix-Marseille-2 Univ., 13 - Marseille (France). Faculte des Sciences de Luminy); Bird, I.G.; Dyce, N.; Sloan, T. (Lancaster Univ. (United Kingdom). Dept. of Physics); Cheung, H.W.K.; Gibson, V.; Gillies, J.; Renton, P.; Taylor; European Muon Collaboration

1993-02-01

16

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

17

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.)

18

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

19

Moments of unpolarized nucleon structure functions in chirally improved lattice QCD  

Energy Technology Data Exchange (ETDEWEB)

We present our results for the lowest moments of unpolarized nucleon structure functions at leading twist. We employ lattice quantum chromodynamics using chirally improved fermions in quenched as well as dynamical simulations.

Goeckeler, Meinulf; Maurer, Thilo; Schaefer, Andreas [University of Regensburg (Germany); Lang, Christian B.; Limmer, Markus [University of Graz (Austria)

2008-07-01

20

Moments of unpolarized nucleon structure functions in chirally improved lattice QCD  

International Nuclear Information System (INIS)

We present our results for the lowest moments of unpolarized nucleon structure functions at leading twist. We employ lattice quantum chromodynamics using chirally improved fermions in quenched as well as dynamical simulations

 
 
 
 
21

Structure functions of the nucleon in a covariant scalar spectator model  

CERN Document Server

Nucleon structure functions, as measured in deep-inelastic lepton scattering, are studied within a covariant scalar diquark spectator model. Regarding the nucleon as an approximate two-body bound state of a quark and diquark, the Bethe-Salpeter equation (BSE) for the bound state vertex function is solved in the ladder approximation. The valence quark distribution is discussed in terms of the solutions of the BSE.

Kusaka, K; Thomas, A W; Williams, A G

1996-01-01

22

Structure functions of the nucleon in a covariant scalar spectator model  

International Nuclear Information System (INIS)

Nucleon structure functions, as measured in deep-inelastic lepton scattering, are studied within a covariant scalar diquark spectator model. Regarding the nucleon as an approximate two-body bound state of a quark and diquark, the Bethe-Salpeter equation (BSE) for the bound state vertex function is solved in the ladder approximation. The valence quark distribution is discussed in terms of the solutions of the BSE. 3 refs., 6 figs

23

Study of nuclear effects in nucleon structure functions up to and beyond the kinematic limit  

International Nuclear Information System (INIS)

An experiment on deep inelastic muon-nucleon scattering is proposed in order to study the x-dependence of nucleon structure functions and their ratios over a range of Q2=50-200 GeV2 and x=0.4-2.0. Such measurements performed on a number of nuclei with atomic weights from 2 to 207 provide new information for detailed studies of the European Muon Collaboration effect and test models explaining the x-behaviour of the nucleon structure functions and their ratios. The measurements are decisive for a proof that a quark-parton model of the nucleus describes adequately the nuclear structure probed at high energies. The upgraded high luminosity Bologna-CERN-Dubna-Munich-Saclay Collaboration spectrometer with improved resolution in transferred energy can be used for the measurements. (author)

24

The polarized structure function of the nucleons with a non-extensive statistical quark model  

Energy Technology Data Exchange (ETDEWEB)

We studied an application of nonextensive thermodynamics to describe the polarized structure function of nucleon, in a model where the usual Fermi-Dirac and Bose-Einstein energy distribution, often used in the statistical models, were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and the chemical potentials given by the corresponding up (u) and down (d) quark normalization in the nucleon and by {Delta}u and {Delta}d of the polarized functions.

Trevisan, Luis A. [Departamento de Matematica e Estatistica, Universidade Estadual de Ponta Grossa, 84010-790, Ponta Grossa, PR (Brazil); Mirez, Carlos [Instituto de Ciencia, Engenharia e Tecnologia - ICET, Universidade Federal dos Vales do Jequitinhonha e Mucuri - UFVJM, Campus do Mucuri, Rua do Cruzeiro 01, Jardim Sao Paulo, 39803-371, Teofilo Otoni, Minas Gerais (Brazil)

2013-05-06

25

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

26

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

27

The ratio of the nucleon structure functions Fsup(N)2 for iron and deuterium  

International Nuclear Information System (INIS)

Using the data on deep inelastic muon scattering on iron and deuterium the ratio of the nucleon structure functions F2sup(N)(Fe)/F2sup(N)(D) is presented. The observed x-dependence of this ratio is in disagreement with existing theoretical predictions. (orig.)

28

Test of determination of nucleon structure functions in the hypothesis of scalar di-quark existence  

International Nuclear Information System (INIS)

The authors present the nucleon structure functions that have been obtained in the hypothesis of existence of a scalar di-quark, progressively broken by increasing energy of electromagnetic probe (Stockolm model). Comparisons with other models and experimental results are presented. 20 figs

29

Target mass corrections and twist-3 in the nucleon spin structure functions  

International Nuclear Information System (INIS)

The Nachtmann moment is employed to study the contribution of twist-3 operator to the nucleon spin structure functions. Target mass corrections to the Cornwall-Norton moments of the spin structure functions g1,2 are discussed. It is found that the corrections play a sizeable role to the contribution of the twist-3 d-tilde2 extracted from the Cornwall-Norton moments

30

Nucleon polarised parton distribution functions  

CERN Document Server

An introduction to the present status of spin-dependent parton distribution functions is given. Both, results from lepton scattering experiments and from polarised proton-proton collisions with longitudinal polarisation are included. Particular emphasis is put on recent results for the gluon polarisation, which is a key element in the nucleon spin structure. Very large gluon polarisation scenarios, put forward to explain the small quark spin contribution to the nucleon spin, are now strongly disfavoured.

Mallot, Gerhard K

2009-01-01

31

Nucleon structure functions from ?mu-Fe scattering at the Tevatron  

International Nuclear Information System (INIS)

We present preliminary results for nucleon structure functions measured in high energy neutrino interactions. Included are new results for the Gross-Llewellyn Smith Sum Rule, ?x/1xF3dx = 2.66 ± .03(stat)±.08(syst), the ratio of cross-sections, ?bar?/?? = .511 ± .002(stat) ± .005(syst), and an analysis of the Q2 evolution of xF3. 16 refs., 5 figs

32

Nucleon size and nucleon structure  

International Nuclear Information System (INIS)

Hidden-color basis states of multiquark systems are expressed in terms of states involving color-singlet hadrons. The size of various nucleon form factors is used to separate the interior perturbative region of quarks from the exterior nonperturbative region of hadrons. The distinction between the baryon interior and its exterior appears to be relevant in baryon spectroscopy and in nuclear forces. 26 refs.; 1 figure

33

Spin structure functions of the nucleon at low Q2 and ?  

International Nuclear Information System (INIS)

Phenomenological approaches to describe the spin structure functions an spin sum rules for proton and neutrons at low momentum transfer Q2 and energy transfer ?, i.e. in the region of the nucleon resonances are discussed. Experiments to measure A1p, A2p and N1n structure functions at CEBAF in a Q2 range from 0.15 to 2.0 GeV2, and a W range from threshold to 2.2 GeV are presented

34

Target-mass corrections to the truncated moments of nucleon spin structure functions and quark-hadron duality  

International Nuclear Information System (INIS)

The Cornell-Norton and Nachtmann moments of nucleon spin structure functions are discussed with a nonvanishing nucleon mass. Target-mass corrections to the truncated moments of the structure functions are calculated. Moreover, the corrections to the Bloom-Gilman quark-hadron dualities of g1p and g2p in both the inelastic resonance production region and the elastic one are analyzed

35

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)

36

A two component model describing nucleon structure functions in the low-x region  

Energy Technology Data Exchange (ETDEWEB)

A two component model describing the electromagnetic nucleon structure functions in the low-x region, based on generalized vector dominance and color dipole approaches is briefly described. The model operates with the mesons of rho-family having the mass spectrum of the form m{sub n}{sup 2}=m{sub r}ho{sup 2}(1+2n) and takes into account the nondiagonal transitions in meson-nucleon scattering. The special cut-off factors are introduced in the model, to exclude the gamma-qq-bar-V transitions in the case of narrow qq-bar-pairs. For the color dipole part of the model the well known FKS-parameterization is used.

Bugaev, E.V. [Institute for Nuclear Research of the Russian Academy of Sciences, 7a, 60th October Anniversary prospect, Moscow 117312 (Russian Federation); Mangazeev, B.V. [Irkutsk State University, 1, Karl Marx Street, Irkutsk 664003 (Russian Federation)

2009-12-15

37

Nucleon structure functions at moderate Q$^{2}$ : relativistic constituent quarks and spectator mass spectrum  

CERN Document Server

We present a model description of the nucleon valence structure function applicable over the entire region of the Bjorken variable x, and above moderate values of Q**2 (> 1 GeV**2). We stress the importance of describing the complete spectrum of intermediate states which are spectator to the deep-inelastic collision. At a scale of 1 GeV**2 the relevant degrees of freedom are constituent quarks and pions. The large-x region is then described in terms of scattering from constituent quarks in the nucleon, while the dressing of constituent quarks by pions plays an important role at intermediate x values. The correct small-x behavior, which is necessary for the proper normalization of the valence distributions, is guaranteed by modeling the asymptotic spectator mass spectrum according to Regge phenomenology.

Kulagin, S A; Weigl, T; Weise, W

1995-01-01

38

Nucleon structure functions at moderate Q2: Relativistic constituent quarks and spectator mass spectrum  

International Nuclear Information System (INIS)

We present a model description of the nucleon valence structure function applicable over the entire region of the Bjorken variable x, and above moderate values of Q2 (?1 GeV2). We stress the importance of describing the complete spectrum of intermediate states which are spectator to the deep-inelastic collision. At a scale of 1 GeV2 the relevant degrees of freedom are constituent quarks and pions. The large-x region is then described in terms of scattering from constituent quarks in the nucleon, while the dressing of constituent quarks by pions plays an important role at intermediate x values. The correct small-x behavior, which is necessary for the proper normalization of the valence distributions, is guaranteed by modeling the asymptotic spectator mass spectrum according to Regge phenomenology. (orig.)

39

Old and New Facets of y-Scaling the Universal Features of Nuclear Structure Functions and Nucleon Momentum Distributions  

CERN Document Server

Some systematic general features of y-scaling structure functions, which are essentially independent of detailed dynamics, are pointed out. Their physical interpretation in terms of general characteristics, such as a mean field description and nucleon-nucleon correlations, is given and their relationship to the momentum distributions illustrated. A new scaling variable is proposed which allows a direct expression of the scaling function in term of an integral over the momemtum distributions thereby avoiding explicit consideration of binding corrections.

Degl'Atti, C C; Atti, Claudio Ciofi degli; West, Geoffrey B.

1997-01-01

40

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report lattice-volume independence of low moments of nucleon structure functions from the coarse RIKEN-BNL-Columbia (RBC) and UKQCD joint dynamical (2+1)-flavor domain-wall fermions (DWF) ensembles at the lattice cut off of (a^{-1}\\sim1.7) GeV. The isovector quark momentum fraction, (_{u-d}), and helicity fraction, (_{\\Delta u - \\Delta d}), both fully non-perturbatively renormalized are studied on two spatial volumes of ((\\sim {\\rm 2.7 fm})^3) and ((\\sim {\\rm 1....

Ohta, Shigemi; Rbc, For The; Collaborations, Ukqcd

2009-01-01

 
 
 
 
41

Nucleon form factors and structure functions from N{sub f}=2 Clover fermions  

Energy Technology Data Exchange (ETDEWEB)

We give an update on our ongoing efforts to compute the nucleon's form factors and moments of structure functions using N{sub f}=2 flavours of non-perturbatively improved Clover fermions. We focus on new results obtained on gauge configurations where the pseudo-scalar meson mass is in the range of 170-270 MeV. We compare our results with various estimates obtained from chiral effective theories since we have some overlap with the quark mass region where results from such theories are believed to be applicable. (orig.)

Collins, S.; Goeckeler, M.; Haegler, P. [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)

2010-12-15

42

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

CERN Document Server

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 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 $\\delta_{LT}$ moment, which thus far was not reproducible for proton and neutron simultaneously in chiral perturbation theory. This problem, known as the "$\\delta_{LT}$ puzzle," is not seen in the present calculation.

Lensky, Vadim; Pascalutsa, Vladimir

2014-01-01

43

Asymptotic solutions of the evolution equation for the polarized nucleon structure function g2(?,Q2)  

International Nuclear Information System (INIS)

We show that quark operators of twist 3 contributing to the polarized nucleon structure function g2tw.3(x, Q2) decouple from the evolution equation for the quark-gluon operators of the same twist in two important limits, Nc?? and n?? (Nc is the number of colours and n refers to the n-th moment of g2). The anomalous dimensions for the quark operators turn out to be always the lowest ones in the spectrum. Asymptotic behaviour of g2(x, Q2) in the region 1-xc?? cases are presented. (orig.)

44

Determination of $\\alpha_s$ and the Nucleon Spin Decomposition Using Recent Polarized Structure Function Data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

New data on polarized $\\mu-p$ and $e-p$ scattering permit a first determination of $\\alpha_s$ using the Bjorken sum rule, as well as higher precision in determining the nucleon spin decomposition. Using perturbative QCD calculations to $O(\\alpha_s^4)$ for the non-singlet combination of structure functions, we find $\\alpha_s(2.5 GeV^2) = 0.375^{+0.062}_{-0.081}$, corresponding to $\\alpha_s(M_Z^2) =0.122^{+0.005}_{-0.009}$, and using calculations to $O(\\alpha_s^3)$ for the sin...

Ellis, John; Karliner, Marek

1994-01-01

45

Nucleon electromagnetic structure revisited  

International Nuclear Information System (INIS)

Unitary and analytic ten-resonance model of the nucleon electromagnetic (e.m.) structure with canonical normalizations and QCD (up to the logarithmic correction) asymptotics is constructed on the four-sheeted Riemann surface, which provides a superposition of vector-meson pole and continuum contributions in a very natural way. As a result it describes simultaneously all existing experimental space-like and time-like data on the proton e.m. form factors (ff's) and on the neutron e.m. ff's as well. A crucial factor in the latter achievement is the inclusion of a contribution of the fourth excited state of the ?(770) meson with the parameters m?'''' 2455 ± 53 MeV, ??'''' = 728 ± 2 MeV and (f(1)?''''NN/f?'''') = 0.0549 ± 0.0005, (f(2)?''''NN/f?'''') = -0.0103 ± 0.0001. The pronounced effect of the two-pion continuum on the isovector spectral functions demonstrating a strong enhancement of the left wing of the ?(770) resonance close to two-pion threshold, which was revealed by Hoehler and Pietarinen by means of the nucleon ff unitarity condition more than a quarter of the century ago, is predicted by the model automatically. The model gives large values of the f(1,2)?NN coupling constants, thus indicating the violation of the OZI rule. Since in the framework of the considered model isoscalar ff's above their lowest branch point ts0s0 9m2? are complex functions, the isoscalar spectral function behaviours are predicted as well

46

Determination of nucleon structure functions on the assumption of diquark presence  

International Nuclear Information System (INIS)

In this thesis, we asked for the presence in the nucleons of either scalar or axial vector diquarks. After the introduction of the basis notions on diquarks and their interest in the understanding of various physical problems, we present in the first chapter the theoretical frame in SU(6) symmetry. Chapter 2 and 3 are respectively devoted to the Stockholm and Torino models. We point out to get a very nice fit of the experimental data with models we had to put in a small Q2 dependence in the various quarks distribution functions previously determined. In chapter 4, we used our distribution functions and compared our predictions with experimental results: the ratio of the neutron electromagnetic structure function to that of the proton, the ratio of the longitudinal component to the transverse one for the lepton-nucleon scattering cross-section, so the dileptons production in Drell-Yan process. The conclusion of that study is that the presence of diquarks does not lead, at the moment, to any obvious contradiction with the experimental data; diquarks as constituents are a viable idea, which in certain kinematical regions could be of crucial importance

47

A detailed study of nucleon structure function in nuclei in the valence quark region  

Energy Technology Data Exchange (ETDEWEB)

The so called {open_quotes}EMC effect{close_quotes} discovered during the 1980`s, has caused a big controversy in the community of nuclear and high energy physicists; during the last ten years, five experiments have been performed in different laboratories and several hundreds of papers about the possible interpretation of the modification of the nucleon structure function inside nuclei have been published. However, from the experimental point of view, the main goal of four experiments (EMC, BCDMS, NMC, FNAL) has been to emphasize the region of low x{sub b}, where shadowing effects appear. In the region of valence quarks and nuclear effects (x{sub b} > 0.1 - 0.2) the most reliable data presently available are from the SLAC E139 experiment performed in 1983 with only 80 hours of beam time. New precise data in the valence quark region are necessary to measure separate structure functions F{sub 2}(x{sub b}, Q{sup 2}) and R{sup lt}(x{sub b},Q{sup 2}) = {sigma}{sub l}/{sigma}{sub t}, and to investigate the real A-dependence of the ratio between bound and free-nucleon structure functions which is not completely defined by the SLAC data. Moreover, from the nuclear physics point of view, a measurement on some unexplored nuclei, like {sup 3}He and {sup 48}Ca, would be of great interest. The intermediate scaling region (0.1 < x{sub b} < 0.7) would be accessible at CEBAF if the machine energy will reach 6-8 GeV, as suggested by all the tests performed on the RF cavities. This physics program has been already presented in two letter of intents.

Bianchi, N. [INFN-Laboratori, Nazionali di Frascati (Italy)

1994-04-01

48

Effects of QCD Vacuum and the Instanton Induced-Contributions to the Nucleon Structure Functions  

Science.gov (United States)

The instanton induced cross section in deep inelastic kinematics is a subject which people are tendentious to investigate it. Instanton induced contributions are well defined for the nucleon structure function. The non-perturbative contribution to the quark distributions of structure function, F2(x,Q2), is considered within an instanton model for the QCD vacuum. We find that the structure function may possess numerically large non-perterbative contributions which are related to the violation of chirality and correspond to the correction of parton distribution of the leading twist. It is shown that the instantons give a negative contribution to the structure function at the NLO approximation. A comparison between our results, considering instantaon effect, and the case when we do not take this effect is done. Taking into account the instanton size, ?, via the modified running coupling constant we get to a good agreement between our results at the NLO and NNLO approximations and the available experimental data, specially at the low values of the Bjorken variable x < 0.1 which confirms the validity of our calculations.

Mirjalili, A.; Dehghani, M.; M. M., Yazdanpanah

2013-02-01

49

Tests of perturbative QCD using CCFR data for measurements of nucleon structure functions  

International Nuclear Information System (INIS)

We present measurements of nucleon structure functions, F2(x, Q2) and xF3(x, Q2), from the high-statistics, high-energy neutrino-iron scattering experiment at the Fermilab Tevatron. The existing high-statistics xF3 determination by the CDHSW collaboration is compared to our data. The data presented here constitute the first corroboration of the QCD prediction of xF3 evolution at low-x, and yields ? anti M anti S = 210 ± 28 ± 41 MeV, and a determination of the GLS sum rule at Q2 = 3 GeV2, SGLS = ?1x xF3/x dx = 2.50 ± 0.018(stat.) ±0.078 (syst.). Our value of ? anti M anti S yields ?s(Mz) = .111 ± .002 ± .003 ± .003 (scale). Comparison of the neutrino determination of F2(x, Q2) with that obtained from the charged-lepton (e or ?) scattering leads to a precise test of the mean-square charge prediction by the Quark Parton Model. The SLAC-CCFR and BCDMS structure function provide a consistent and precise set of structure functions over a large range of Q2. (orig.)

50

Nucleon structure from lattice QCD  

International Nuclear Information System (INIS)

In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a2) discretization effects.

51

Nucleon structure from lattice QCD  

Energy Technology Data Exchange (ETDEWEB)

In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.

Dinter, Simon

2012-11-13

52

Nucleon isovector structure functions in (2+1)-flavor QCD with domain wall fermions  

CERN Document Server

We report on numerical lattice QCD calculations of some of the low moments of the nucleon structure functions. The calculations are carried out with gauge configurations generated by the RBC and UKQCD collaborations with (2+1)-flavors of dynamical domain wall fermions and the Iwasaki gauge action ($\\beta = 2.13$). The inverse lattice spacing is $a^{-1} = 1.73$ GeV, and two spatial volumes of ((2.7{\\rm fm})^3) and ((1.8 {\\rm fm})^3) are used. The up and down quark masses are varied so the pion mass lies between 0.33 and 0.67 GeV while the strange mass is about 12 % heavier than the physical one. The structure function moments we present include fully non-perturbatively renormalized iso-vector quark momentum fraction, (_{u-d}), helicity fraction, (_{\\Delta u - \\Delta d}), and transversity, (_{\\delta u - \\delta d}), as well as an unrenormalized twist-3 coefficient, (d_1). The ratio of the momentum to helicity fractions, (_{u-d}/_{\\Delta u - \\Delta d}), does not show dependence on the light quark mass and agrees ...

Aoki, Yasumichi; Lin, Huey-Wen; Ohta, Shigemi; Sasaki, Shoichi; Tweedie, Robert; Yamazaki, Takeshi; Zanotti, James

2010-01-01

53

Nucleon isovector structure functions in (2+1)-flavor QCD with domain wall fermions  

International Nuclear Information System (INIS)

We report on numerical lattice QCD calculations of some of the low moments of the nucleon structure functions. The calculations are carried out with gauge configurations generated by the RBC and UKQCD Collaborations with (2+1)-flavors of dynamical domain-wall fermions and the Iwasaki gauge action (?=2.13). The inverse lattice spacing is a-1=1.73 GeV, and two spatial volumes of (2.7 fm)3 and (1.8 fm)3 are used. The up and down quark masses are varied so the pion mass lies between 0.33 and 0.67 GeV, while the strange mass is about 12% heavier than the physical one. The structure function moments we present include the fully nonperturbatively renormalized isovector quark momentum fraction u-d, the helicity fraction ?u-?d, and transversity ?u-?d, as well as an unrenormalized twist-3 coefficient d1. The ratio of the momentum to helicity fractions, u-d/?u-?d, does not show dependence on the light quark mass and agrees well with the value obtained from experiment. Their respective absolute values, fully renormalized, show interesting trends toward their respective experimental values at the lightest quark mass. A prediction for the transversity, 0.7?u-?d1, though yet to be renormalized, supports the perturbative Wandzura-Wilczek relation.

54

Polarized structure function sigma_lt' for kaon electroproduction in the nucleon resonance region  

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.

Rakhsha Nasseripour; B. Raue; Daniel Carman; Pawel Ambrozewicz

2008-02-19

55

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

CERN Document Server

We report lattice-volume independence of low moments of nucleon structure functions from the coarse RIKEN-BNL-Columbia (RBC) and UKQCD joint dynamical (2+1)-flavor domain-wall fermions (DWF) ensembles at the lattice cut off of (a^{-1}\\sim1.7) GeV. The isovector quark momentum fraction, (_{u-d}), and helicity fraction, (_{\\Delta u - \\Delta d}), both fully non-perturbatively renormalized are studied on two spatial volumes of ((\\sim {\\rm 2.7 fm})^3) and ((\\sim {\\rm 1.8 fm})^3). Their naturally renormalized ratio, (_{u-d}/_{\\Delta u - \\Delta d}), is not affected by any finite-size effect. It does not depend strongly on light quark mass and does agree well with the experiment. The respective absolute values, fully non-perturbatively renormalized, do not show any finite-size effect either. They show trending toward the respective experimental values at the lightest up- and down-quark mass. This trending down to the experimental values appears to be a real physical effect driven by lighter quarks. The observations a...

Ohta, Shigemi

2009-01-01

56

Nucleon Spin Structure: Experiment  

Science.gov (United States)

The experimental study of nucleon spin structure is at a transitional stage. Deeply inelastic scattering of leptons has revealed much about quark helicity distributions, and is approaching the limits of what is possible with present experimental facilities. The latest results from semi-inclusive measurements at HERMES will be presented. Precise new complementary data are expected soon from W production at RHIC-Spin. The gluon polarization will also be measured soon at COMPASS and RHIC. Meanwhile, single-spin asymmetries that promise to provide access to the unknown transversity distribution have been observed, and will be discussed. Based on these signals, the first measurements of transversity are underway. Finally, single spin asymmetries have also been recently observed in hard exclusive processes such as deeply virtual Compton scattering. These signals have the potential to provide a new window on both orbital angular momentum of partons, and on correlations between their longitudinal momentum and transverse position.

Miller, Andy

2003-04-01

57

Deep inelastic lepton-nucleon interactions and the structure of the nucleon structure functions, multiplicities and nu , nu total cross sections  

CERN Document Server

Structure functions for nu N and nu N interactions were obtained from the three-quark-boson nucleon model constructed before from the study of deep inelastic eN scattering (see abstr. A54632 of 1971). The results obtained give quantitative relations between eN and nu N, nu N interactions, and explicit expressions for the differential and integral cross sections. With the energy dependence of pion multiplicity for nu N interactions deduced from the experimental data, the calculated total nu N cross sections with no free parameters reproduced both the CERN 1967 propane and the recent Gargamelle results. For nu N interactions, the calculated total cross sections agree also with the Gargamelle data, and a lower pion multiplicity (i.e., about one-half the nu N multiplicity) is predicted. Excluding the effects of intermediate bosons, all have the same 'asymptotic' cross section although the approach to this limit is extremely slow except for sigma /sup nu p/. (27 refs).

Wang, C P

1974-01-01

58

Nucleon structure functions at small x via the Pomeron exchange in AdS space with a soft infrared wall  

Science.gov (United States)

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

59

The Spin Structure of the Nucleon  

CERN Document Server

This article reviews recent results on the spin structure of the nucleon from polarized deep inelastic lepton-nucleon scattering and polarized proton-proton scattering. For a description of the nucleon in terms of parton distribution functions (pdf) the knowledge of three basic distributions is needed: The relatively well known unpolarized pdfs, the helicity distributions and the transversity distributions. The latter two play an essential role in understanding the spin structure of the nucleon. New results on the gluon helicity distribution $\\Delta G(x)$ and the helicity distributions for strange and valence quarks are discussed. A first determination of the up to now unknown transversity distributions $\\Delta_{T}q(x)$ is presented. Finally results from deep virtual Compton scattering, giving access to the orbital angular momentum contribution of quarks to the nucleon spin, are discussed.

Pretz, Jörg

2007-01-01

60

Nucleon-nucleon momentum correlation function for light nuclei  

CERN Document Server

Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics.

Ma, Y G; Chen, J G; Fang, D Q; Guo, W; Liu, G H; Ma, C W; Ma, E J; Shen, W Q; Shi, Y; Su, Q M; Tian, W D; Wang, H W; Wang, K; Wei, Y B; Yan, T Z

2007-01-01

 
 
 
 
61

From Nuclear Structure to Nucleon Structure  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Similarities between nuclear structure study with many-body theory approach and nucleon structure calculations with lattice QCD are pointed out. We will give an example of how to obtain the connected sea partons from a combination of the experimental data, a global fit of parton distribution functions and a lattice calculation. We also present a complete calculation of the quark and glue decomposition of the proton momentum and angular momentum in the quenched approximation....

Liu, Keh-fei

2014-01-01

62

Twist expansion of the nucleon structure functions, F2 and FL, in the DGLAP improved saturation model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ar...

Bartels, Jochen; Golec-biernat, Krzysztof; Motyka, Leszek

2009-01-01

63

Probing Nucleon Spin Structure  

CERN Document Server

One of the important questions in high energy physics is the relation of quark and gluon spin to that of the nucleons which they comprise. Polarization experiments provide a mechanism to probe the spin properties of elementary particles and provide crucial tests of Quantum Chromodynamics (QCD). The theoretical and experimental status of this fundamental question will be reviewed in this paper.

Ramsey, G P

1997-01-01

64

Covariant solutions of the Bethe-Salpeter equation and an application to the nucleon structure function  

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.)

65

Experimental study of the nucleon structure functions and of the gluon distribution from charged-current neutrino and antineutrino interactions  

International Nuclear Information System (INIS)

Inclusive neutrino and antineutrino charged current interactions were studied in the CHARM detector exposed to neutrino and antineutrino Wide Band Beams of the CERN 400 GeV SPS. The x and Q2 dependence of the structure functions F2 and xF3 and of the antiquark momentum distribution q were determined. The data have been interpreted in terms of QCD theory using the Furmanski-Petronzio method. In this way we have determined #betta#sub(LO)=[190+70sub(-40)(stat)+-70 (syst.)] MeV and the structure functions of quarks and gluons without specific assumptions on their analytic dependence. The results agree with previous experiments which relied on model assumptions in the analysis. We conclude that the model independent simultaneous analysis of the xF3, F2, anti q structure functions gives a more reliable determination of the gluon distribution in the nucleon. (orig.)

66

Gerasimov-Drell-Hearn sum rule and behaviour of nucleon polarized structure function at small Q2  

International Nuclear Information System (INIS)

Using Gerasimov-Drell-Hearn sum rule it is shown that neutron polarized structure function achieves the asymptotic value at Q2=2 GeV2. For proton polarized 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 nucleon polarized structure functions are obtained in the interval of x=0,45 + 1 on the basis of available data in the resonance energy region at Q22. It appears that at Q2 =2 + 3Gev2 these integrals have scaling behaviour, and their values agree with the extrapolations to the region of large x made in experimental works

67

Twist expansion of the nucleon structure functions, F2 and FL, in the DGLAP improved saturation model  

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.)

68

Quasielastic electron scattering on a two-nucleon model system: Scaling and cumulant expansion of the structure function  

International Nuclear Information System (INIS)

The structure function S(q,?) for quasielastic electron scattering on a nonrelativistic two-nucleon model system is evaluated numerically. These S values are considered as pseudodata to study sum rules, y scaling, and the cumulant expansion. For the force models considered it is found that the reduced structure function (q/2m)S(q,?) in the limit q?? scales to the longitudinal momentum distribution PL(y) in the target. Except for small y values, this limit, however, is reached only very slowly, which may be due to the strictly nonrelativistic treatment. The cumulant expansion based on low-order cumulants is not useful. We also derive the analytical result that in our potential model S(q,?)=O(?-5.5) for ??? and fixed q. This shows that higher-order cumulants do not exist

69

Nucleon structure from stochastic estimators  

Energy Technology Data Exchange (ETDEWEB)

The structure of the proton and neutron, parameterized by moments of generalized parton distribution functions (GPDs), can be accessed from first principle through the computation of baryon three-point functions with lattice QCD. The numerical effort involved in such computations is sizable and thus an efficient algorithm that extracts most information at given cost is highly desirable. In this work we demonstrate that stochastic estimation techniques can substantially increase the information/cost ratio. We examine the available results at N{sub f}=2 for the nucleon axial coupling gA and iso-vector quark momentum fraction {sub u-d} from various collaborations and compare them to the experimental values. The tension between them is attributed to excited state contributions (ESCs). We furthermore study the impact of ESCs in moments of GPDs through a model fit. This model also deals with the effects of the choice of parameters used in the computation, like the source-sink separation t{sub sink}. We demonstrate that the choice of t{sub sink} by the Regensburg group in previous studies was reasonable and cannot account for discrepancies with the experiment. To reduce the excited state contributions in two-point functions, and consequently three-point functions, we suggest a non-Gaussian quark smearing. This is a linear combination of two Gaussian smearings with one free parameter, which can be tuned to an optimal choice with a fit.

Najjar, Johannes Siegfried Samir

2014-10-01

70

Small- and large-x nucleon spin structure from a global QCD analysis of polarized Parton Distribution Functions  

CERN Document Server

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

71

Structure in nucleon-nucleon system and dinucleon resonance  

International Nuclear Information System (INIS)

An extensive amount of data were obtained from measurements of proton-proton elastic scattering up to 5 GeV/c. Physics learned from these data as well as other related experimental results was summarized. A summary of structure in nucleon-nucleon system is given and dinucleon resonances are considered

72

The structure of the nucleon  

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

Improved QCD sum rule estimates of the higher twist contributions to polarised and unpolarised nucleon structure functions  

CERN Document Server

We re-examine the estimates of the higher twist contributions to the integral of $g_1$, the polarised structure function of the nucleon, based on QCD sum rules. By including corrections both to the perturbative contribution and to the low energy contribution we find that the matrix elements of the relevant operators are more stable to variations of the Borel parameter $M^2$, allowing for a meaningful estimate of the matrix elements. We find that these matrix elements are typically twice as large as previous estimates. However, inserting these new estimates into the recently corrected expressions for the first moments of $g_1$ leads to corrections too small to affect the phenomenological analysis. For the unpolarised case the higher twist corrections to the GLS and Bjorken sum rules are substantial and bring the estimate of $\\Lambda_{QCD}$ from the former into good agreement with that obtained from the $Q^2$ dependence of deep inelastic data.

Ross, Graham G; Ross, Graham G.

1994-01-01

74

A precise determination of the nucleon structure functions in charged-current interactions on an iron target  

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

75

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

76

Nucleon structure from stochastic estimators  

CERN Document Server

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

77

Description of the moments of nucleon structure function data at Q2 >= 30 GeV2 in the composite model  

International Nuclear Information System (INIS)

The moments of nucleon structure functions are found by the formula expressing them through the pion moments. For the calculation of the latter the solutions of the covariant single-- time two-particle equation are used, corresponding to the interaction kernel chosen in the form of the one-gluon exchange amplitude

78

The Bjorken system of equations and nucleon spin structure-function data  

CERN Document Server

The status of the Bjorken sum rule is examined in the light of recent data on the spin structure functions of the deuteron and proton obtained by the SMC group, the neutron by the E142 group and the proton by the E143 group. Combining the new data with that already obtained for the proton by the EMC group and SLAC/YALE collaborations, we show that the Bjorken system of equations is violated at the 2-3 sigma level. We also discuss in detail the role of possible higher-twist contributions and higher-order PQCD corrections.

Ratcliffe, P G

1994-01-01

79

The Weak Structure of the Nucleon  

Directory of Open Access Journals (Sweden)

Full Text Available The weak structure of the nucleon is the non-perturbative response of the nucleon to a weakinteracting probe. Here, I review the existing experimental data at low energy. In particular, the role of fewbody nuclear reactions in constraining the weak response of the nucleon, in vacuum and in nuclear medium, is discussed.

Gazit D.

2010-04-01

80

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.)

 
 
 
 
81

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.)

82

New Measurements of Nucleon Structure Functions from the CCFR/NuTeV Collaboration  

CERN Document Server

We report on the extraction of the structure functions F_2 and Delta xF_3 = xF_3nu-xF_3nubar from CCFR neutrino-Fe and antineutrino-Fe differential cross sections. The extraction is performed in a physics model independent (PMI) way. This first measurement for Delta xF_3, which is useful in testing models of heavy charm production, is higher than current theoretical predictions. The F_2 (PMI) values measured in neutrino and muon scattering are in good agreement with the predictions of Next to Leading Order PDFs (using massive charm production schemes), thus resolving the long-standing discrepancy between the two sets of data.

Bodek, Arie; Adams, T; Alton, A; Arroyo, C G; Avvakumov, S; De Barbaro, L; De Barbaro, P; Bazarko, A O; Bernstein, R H; Bolton, T; Brau, J E; Buchholz, D; Budd, H S; Bugel, L; Conrad, J; Drucker, R B; Fleming, B T; Formaggio, J A; Frey, R; Goldman, J; Goncharov, M; Harris, D A; Johnson, R A; Kim, J H; King, B J; Kinnel, T; Koutsoliotas, S; Lamm, M J; Marsh, W; Mason, D; McFarland, K S

2000-01-01

83

New Measurements of Nucleon Structure Functions from CCFR/NuTeV  

CERN Document Server

We report on the extraction of the structure functions F_2 and Delta xF_3 = xF_3nu-xF_3nub from CCFR neutrino-Fe and antineutrino-Fe differential cross sections. The extraction is performed in a physics model independent (PMI) way. This first measurement for Delta xF_3, which is useful in testing models of heavy charm production, is higher than current theoretical predictions. Within 5% the F_2 (PMI) values measured in neutrino and muon scattering are in agreement with the predictions of Next-to-Leading-Order PDFs (using massive charm production schemes), thus resolving the long-standing discrepancy between the two measurements.

Bodek, Arie; Adams, T; Alton, A; Arroyo, C G; Avvakumov, S; De Barbaro, L; De Barbaro, P; Bazarko, A O; Bernstein, R H; Bolton, T; Brau, J E; Buchholz, D; Budd, H S; Bugel, L; Conrad, J; Drucker, R B; Fleming, B T; Formaggio, J A; Frey, R; Goldman, J; Goncharov, M; Harris, D A; Johnson, R A; Kim, J H; King, B J; Kinnel, T; Koutsoliotas, S; Lamm, M J; Marsh, W; Mason, D; McFarland, K S

2001-01-01

84

Polarized Structure Function $\\sigma_{LT'}$ for $p({\\vec e},e'K^+)\\Lambda$ in the Nucleon Resonance Region  

CERN Document Server

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

Determination of the nucleon structure functions in the study of the inclusive charged current interactions of neutrinos and antineutrinos in iron between 30 and 200 GeV  

International Nuclear Information System (INIS)

In the deep inelastic neutrino scattering experiment of the CERN-Dortmund-Heidelberg-Saclay collaboration realized on the CERN SPS narrow band beam, we have measured 23000 charged current neutrino and 6200 antineutrino interactions. The structure functions of the nucleon have been extracted from the differential cross sections on iron and compared with parton model predictions. The total cross sections and the fraction of momentum carried by the antiquarks in the nucleon have been measured as function of the neutrino energy. The structure functions obtained for different Q2 bins show significant deviations from scale invariance. The data are in agreement with QCD predictions for a value of the scale parameter ? between 300 and 700 MeV

86

Nucleon Spin And Structure Studies With COMPASS  

CERN Document Server

The COMPASS experiment at CERN investigates nucleon structure and spectroscopy with high-intensity muon and hadron beams. Between 2002 and 2004 COMPASS has mainly concentrated on the spin structure of the nucleon via deep-inelastic scattering of polarized muons on polarized nucleons. First results include measurements of the gluon contribution to the nucleon spin via charm production and high-$p_{t}$ pairs, A polarization, vector-meson production, Collins and Sivers asymmetries, inclusive and semi-inclusive deep-inelastic scattering asymmetries and a search for pentaquark states. A short overview of these results is presented.

Platchkov, Stephane

2006-01-01

87

Nucleon Spin And Structure Studies With COMPASS  

Science.gov (United States)

The COMPASS experiment at CERN investigates nucleon structure and spectroscopy with high-intensity muon and hadron beams. Between 2002 and 2004 COMPASS has mainly concentrated on the spin structure of the nucleon via deep-inelastic scattering of polarized muons on polarized nucleons. First results include measurements of the gluon contribution to the nucleon spin via charm production and high-pt pairs, ? polarization, vector-meson production, Collins and Sivers asymmetries, inclusive and semi-inclusive deep-inelastic scattering asymmetries and a search for pentaquark states. A short overview of these results is presented.

Platchkov, Stephane

2006-07-01

88

Structure of the nucleon based on a relativistic 3-body approach to the NJL model  

International Nuclear Information System (INIS)

After a brief review of the relativistic Faddeev approach to the nucleon in the NJL model, some results for the nucleon structure functions and the nuclear matter equation of state are discussed. (author)

89

Resonance structures in nucleon-nucleon scattering at intermediate energies  

International Nuclear Information System (INIS)

Experiments are described which were performed at the Saturne II proton synchrotron (Saclay, France) and which are directly or indirectly related to the conceivable dibaryon resonances. The difference is outlined between production resonances and dibaryon resonances, which can be interpreted as a virtual exchange in an elastic interaction of two dibaryons. The resonances were investigated in elastic as well as inelastic scattering of nucleons on nucleons, in reactions with deuterons, and in the mass spectra of inclusive reactions with light nuclei. The existing two groups of theoretical models differ in that at low resonance masses, long range forces are neglected and the lowest masses of the resonance states even lie below the pion formation threshold, whereas at high masses, long range forces are taken into account. Three very accurate experiments dealing with low resonance masses gave a clearly negative result. This conclusion was confirmed by mass spectra in inclusive reactions. Evidence in favor of the existence of dibaryon interactions obtained during other measurements either gave very weak resonance signals or could be easily explained in terms of conventional meson exchange. In the region of large resonance masses, a number of pp ? d?+ experiments were performed, where the observed structures are unambiguous. In principle, the structures can also be explained in terms of meson-nucleon exchange and formation of Delta, although at high orbital moments

90

About nucleon-nucleon potential: meson exchange currents and relativistic approach of nuclear structure  

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

91

Insight into nucleon structure from generalized parton distributions  

Energy Technology Data Exchange (ETDEWEB)

The lowest three moments of generalized parton distributions are calculated in full QCD and provide new insight into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon.

Negele, J.W.; Brower, R.C.; Dreher, P.; Edwards, R.; Fleming, G.; Haegler, Ph.; Lippert, Th.; Pochinsky, A.V.; Renner, D.B.; Richards, D.; Schilling, K.; Schroers, W

2004-03-01

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

Helicity structure of the Pomeron-nucleon-nucleon vertex using a multiperipheral model  

International Nuclear Information System (INIS)

Using a version of the multiperipheral model, the Pomeron-nucleon-nucleon helicity residue functions are obtained over a wide range of t values. Pions are assumed to be exchanged along the sides of the multiperipheral ladder and all but the lowest helicity-determining loop are replaced by a Pomeron exchange. The helicity-flip-to-nonflip ratios are found to be in good agreement with experiment while the overall normalization is less than experiment. An interesting sign structure is found in the individual flip amplitudes for the exchanged baryons. A review is also given of the current experimental status of the helicity structure of ?N and NN elastic scattering

94

Measurement of the nucleon structure function in the deep inelastic neutrino-iron scattering with a wide-band neutrino beam  

International Nuclear Information System (INIS)

In this thesis the nucleon structure function xF3 is determined from the inclusive measurement of the deep inelastic neutrino nucleon charged current interaction. The data were taken in the CERN wide band neutrino beam using the detector of the CERN-Dortmund-Heidelberg-Saclay collaboration. This detector serves at the same time as target, as hadron energy calorimeter and as muon spectrometer. One major aspect of this work was to study the possibility of using high statistics wide band beam data for structure function analysis. The systematic errors specific to this kind of beam are investigated. To obtain the differential cross sections about 100000 neutrino and 75000 antineutrino events in the energy range 20-200 GeV are analysed. The differential cross sections are normalized to the total cross sections, as measured in the narrow band beam by the same collaboration. The calculated structure function xF3 shows significant deviations from scaling. These scaling violations are compared quantitatively with the predictions of quantum chromodynamics. (orig.)

95

Experimental Study of Nucleon Structure and QCD  

Energy Technology Data Exchange (ETDEWEB)

Overview of Experimental Study of Nucleon Structure and QCD, with focus on the spin structure. Nucleon (spin) Structure provides valuable information on QCD dynamics. A decade of experiments from JLab yields these exciting results: (1) valence spin structure, duality; (2) spin sum rules and polarizabilities; (3) precision measurements of g{sub 2} - high-twist; and (4) first neutron transverse spin results - Collins/Sivers/A{sub LT}. There is a bright future as the 12 GeV Upgrade will greatly enhance our capability: (1) Precision determination of the valence quark spin structure flavor separation; and (2) Precision extraction of transversity/tensor charge/TMDs.

Jian-Ping Chen

2012-03-01

96

Chiral symmetry and nucleon structure  

International Nuclear Information System (INIS)

Recently it has been realized that significant tests of the validity of QCD are available in low energy experiments (E < 500 MeV) by exploiting the property of (broken) chiral symmetry. This technique has been highly developed in The Goldstone boson sector by the work of Gasser and Leutwyler. Application to the nucleon system is much more difficult and is now being carefully developed

97

Meson-Cloud Effects in the Electromagnetic Nucleon Structure  

Science.gov (United States)

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 Poincaré-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; Schweiger, Wolfgang

2014-08-01

98

Meson-cloud effects in the electromagnetic nucleon structure  

CERN Document Server

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

99

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

100

Nuclear structure based on correlated realistic nucleon-nucleon potentials  

International Nuclear Information System (INIS)

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

 
 
 
 
101

Twist expansion of the nucleon structure functions, F{sub 2} and F{sub L}, in the DGLAP improved saturation model  

Energy Technology Data Exchange (ETDEWEB)

Higher twist effects in the deeply inelastic scattering are studied. We start with a short review of the theoretical results on higher twists in QCD. Within the saturation model we perform a twist analysis of the nucleon structure functions F{sub T} and F{sub L} at small value of the Bjorken variable x. The parameters of the model are fitted to the HERA F{sub 2} data, and we derive a prediction for the longitudinal structure function F{sub L}. We conclude that for F{sub L} the higher twist corrections are sizable whereas for F{sub 2}=F{sub T}+F{sub L} there is a nearly complete cancellation of twist-4 corrections in F{sub T} and F{sub L}. We discuss a few consequences for future LHC measurements. (orig.)

Bartels, Jochen [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Golec-Biernat, Krzysztof [Rzeszow Univ. (Poland). Inst. of Physics; Polish Academy of Sciences, Krakow (Poland). Inst. of Nuclear Physics; Motkyka, Leszek [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Uniwersytet Jagiellonski, Krakow (Poland). Inst. Fizyki

2009-11-15

102

Measurement of R = {sigma}{sub L}/{sigma}{sub T} and the Separated Longitudinal and Transverse Structure Functions in the Nucleon Resonance Region  

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

103

Measurement of R = sigma_L / sigma_T and the Separated Longitudinal and Transverse Structure Functions in the Nucleon Resonance Region  

CERN Document Server

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^2 < 5.5 GeV^2. The data have been used to accurately perform over 170 Rosenbluth-type longitudinal / transverse separations. The precision R = sigma_L / sigma_T data are presented here, along with the first separate values of the inelastic structure functions F_1 and F_L in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q^2 = 1 GeV^2 in the separated structure functions independently.

Liang, Y; Ahmidouch, A; Armstrong, C S; Arrington, J; Asaturyan, R; Avery, S; Baker, O K; Beck, D H; Blok, H P; Bochna, C W; Böglin, W; Bosted, P; Bouwhuis, M; Breuer, H; Brown, D S; Brüll, A; Carlini, R D; Cha, J; Chant, N S; Cochran, A; Cole, L; Danagulyan, S; Day, D B; Dunne, J; Dutta, D; Ent, R; Fenker, H C; Fox, B; Gan, L; Gao, H; Garrow, K; Gaskell, D; Gasparian, A; Geesaman, D F; Gilman, R; Gueye, P L J; Harvey, M; Holt, R J; Jiang, X; Jones, M; Keppel, C E; Kinney, E; Lorenzon, W; Lung, A; Mack, D J; Markowitz, P; Martin, J W; McIlhany, K; McKee, D; Meekins, D; Miller, M A; Milner, R G; Mitchell, J H; Mkrtchyan, H G; Müller, B A; Nathan, A; Niculescu, G; Niculescu, I; O'Neill, T G; Papavassiliou, V; Pate, S F; Piercey, R B; Potterveld, D; Ransome, R D; Reinhold, J; Rollinde, E; Rondon, Oscar A; Roos, P; Sarty, A J; Sawafta, R; Schulte, E C; Segbefia, E; Smith, C; Stepanyan, S; Strauch, S; Tadevosyan, V; Tang, L; Tieulent, R; Tvaskis, V; Uzzle, A; Vulcan, W F; Wood, S A; Xiong, F; Yuan, L; Zeier, M; Zihlmann, B; Ziskin, V

2004-01-01

104

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

105

Structure functions and structure function ratio F2n/F2p at small xBj and Q2 in muon-nucleon scattering  

International Nuclear Information System (INIS)

Preliminary results on the measurement of the structure functions F2p(xBj, Q2) and F2d(xBj, Q2) and of the ratio F2n/F2p from experiment E665 are presented. The data were obtained using 465 GeV/c muons scattering off liquid hydrogen and deuterium targets. The dependence of the structure functions on xBj and Q2 is examined in the kinematic range xBj > 8 x 10-4 and Q2 > 0.2 GeV2/c2. The structure function ratio is presented as a function of xBj, for xBj > 10-6

106

Nucleon Spin Structure: Longitudinal and Transverse  

Energy Technology Data Exchange (ETDEWEB)

Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction. The transverse spin structure and the TMDs are the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has played a major role in the worldwide effort to study both the longitudinal and transverse spin structure. Highlights of recent results will be presented. With 12-GeV energy upgrade, JLab will provide the most precise measurements in the valence quark region to close a chapter in longitudinal spin study. JLab will also perform a multi-dimensional mapping of the transverse spin structure and TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space and extracting the u and d quark tensor charges of the nucleon. The precision mapping of TMDs will also allow a detailed study of the quark orbital motion and its dynamics.

Jian-Ping Chen

2011-02-01

107

Mapping out symmetry violation in nucleon structure  

Energy Technology Data Exchange (ETDEWEB)

This series of slides reviews the information we know today about the structure of the nucleon: form factors, quark content, strangeness content, charge distribution, magnetization distribution, Lamb shift, size, transverse spatial distribution and how we know it and presents what we can expect from future experiments and particularly from two-photon exchange tests.

Arrington, J. [Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, IL 60439 (United States)

2010-07-01

108

Nucleon structure study by virtual Compton scattering  

International Nuclear Information System (INIS)

It is proposed to study nucleon structure by virtual Compton scattering using the Hall A HRS spectrometers. This reaction is planned to be measured in the Roper resonance region and at the highest center of mass energy to observe the beginning of the hard scattering regime. (author) 25 refs.; 8 figs.; 6 tabs

109

Probing the nucleon structure with SIDIS at Jefferson Lab  

Energy Technology Data Exchange (ETDEWEB)

In recent years, measurements of azimuthal moments of polarized hadronic cross sections in hard processes have emerged as a powerful tool to probe nucleon structure. Many experiments worldwide are currently trying to pin down various effects related to nucleon structure through Semi-Inclusive Deep-Inelastic Scattering (SIDIS). Azimuthal distributions of final-state particles in semi-inclusive deep inelastic scattering, in particular, are sensitive to the orbital motion of quarks and play an important role in the study of Transverse Momentum Dependent parton distribution functions (TMDs) of quarks in the nucleon. The CLAS spectrometer, installed in Hall-B at Jefferson Lab, has collected semi-inclusive data using the CEBAF 6 GeV polarized electron beam on polarized solid NH{sub 3} and ND{sub 3} targets. An overview of these measurements is presented.

Pereira, Sergio Anefalos, E-mail: sergio.pereira@lnf.infn.it

2013-01-15

110

Quark-spin structure of the nucleon: 20 years of the JINR-CERN collaboration  

International Nuclear Information System (INIS)

Problem on quark-spin structure of nucleon is discussed. Review of the 20-year cooperation between the JINR and CERN in the area of deep inelastic muon-nucleon scattering is presented. Main attention was paid to precision measurements of scale invariance violations and to nucleon internal spin structure. Cross sections of deep inelastic scattering and structural functions in a quark-parton model are determined. 84 refs., 17 figs., 3 tabs

111

Spin-dependent structure functions of nucleon in the chiral bag model taking into account recoil effects  

International Nuclear Information System (INIS)

Within the chiral bag model (CBM) the spin-dependent structure functions of a polarized proton g1p(x) and polarized neutron g1n(x) are investigated. The results obtained within CBM with a scalar ?qq coupling agree with EMC experimental data rather well. 11 refs.; 1 fig.; 2 tabs

112

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

113

Nuclear structure calculations and modern nucleon-nucleon potentials  

Science.gov (United States)

We study ground-state properties of the doubly magic nuclei 4He, 16O, and 40Ca employing the Goldstone expansion and using as input four different high-quality nucleon-nucleon (NN) potentials. The short-range repulsion of these potentials is renormalized by constructing a smooth low-momentum potential Vlow-k. This is used directly in a Hartree-Fock approach, and corrections up to third order in the Goldstone expansion are evaluated. Comparison of the results shows that they are only slightly dependent on the choice of the NN potential.

Coraggio, L.; Covello, A.; Gargano, A.; Itaco, N.; Kuo, T. T.; Machleidt, R.

2005-01-01

114

Nuclear Structure Calculations and Modern Nucleon-Nucleon Potentials  

CERN Document Server

We study ground-state properties of the doubly magic nuclei 4He, 16O, and 40Ca employing the Goldstone expansion and using as input four different high-quality nucleon-nucleon (NN) potentials. The short-range repulsion of these potentials is renormalized by constructing a smooth low-momentum potential V-low-k. This is used directly in a Hartree-Fock approach and corrections up to third order in the Goldstone expansion are evaluated. Comparison of the results shows that they are only slightly dependent on the choice of the NN potential.

Coraggio, L; Gargano, A; Itaco, N; Kuo, T S; Machleidt, R

2005-01-01

115

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

116

Electromagnetic studies of nucleon and nuclear structure  

International Nuclear Information System (INIS)

Important objectives of the group are the study of subatomic structure through experimental measurements and the interpretation of the data through modeling. The common theme that unifies the studies of strong interactions and hadronic systems is the effort to determine the electromagnetic response as completely as possible. The general approach is coincidence detection of exclusive final states and determination of the dependence on the spin variables using polarized beams and targets and outgoing nucleon polarimetry. Direct reaction and giant resonance studies of electron quasi-elastic scattering on 12C and 16O are reported, as well as work on nuclear structure models and instrumentation development

117

Nuclear Structure Calculations with Modern Nucleon-Nucleon Potentials  

Science.gov (United States)

We have performed shell-model calculations starting from modern nucleon-nucleon potentials VNN. We make use of a new approach to the renormalization of the short-range repulsion of VNN in which a low-momentum potential Vlow-k is derived by integrating out the high-momentum components of VNN down to a cutoff momentum ?. We present some results for nuclei around closed shells which have been obtained starting from the CD-Bonn potential. We have also performed calculations making use of different modern NN potentials. Comparison of the results obtained shows that they are only slightly dependent on the kind of potential used as input. The effects of changes in ? are explored.

Covello, A.; Coraggio, L.; Gargano, A.; Itaco, N.

2005-03-01

118

Structure of the nucleon and nuclei studied by HERMES  

International Nuclear Information System (INIS)

Recent results from studies of inclusive and semi-inclusive deep-inelastic lepton scattering are presented. Data with polarization provide the first measurement of the b1(x, Q2) structure function in the deuteron, a five component flavor decomposition of quark helcity distributions in the nucleon, as well as results pertaining to transverse spin physics and deep virtual Compton scattering. Data from unpolarized targets constrain models of quark hadronization and give a measure of parton energy loss in cold nuclear matter

119

Exploring the Nucleon Structure from First Principles of QCD  

CERN Document Server

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.

Bietenholz, W; Gockeler, M; Horsley, R; Perlt, H; Pleiter, D; Rakow, P E L; Schierholz, G; Schiller, A; Streuer, T; Zanotti, J M

2010-01-01

120

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

 
 
 
 
121

Nucleon structure and properties of dense matter  

International Nuclear Information System (INIS)

We consider the properties of dense matter in a framework of the Skyrme soliton model and the chiral bag model. The influence of the nucleon structure on the equation of state of dense matter is emphasized. We find that in both models the energy per unit volume is proportional to n4/3, n being the baryon number density. We discuss the properties of neutron stars with a derived equation of state. The role of many-body effects is investigated. The effect of including higher order terms in the chiral lagrangian is examined. The phase transition to quark matter is studied. 29 refs., 6 figs. (author)

122

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 processes of intermediate-energy nuclear reactions. The nucleon binding in the photonuclear absorption mechanism is taken into account accordingly. (author)

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

2002-08-01

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

Spin structures of the pion and nucleon  

Directory of Open Access Journals (Sweden)

Full Text Available We present recent studies on the transverse spin densities of the pion and nucleon within the framework of the chiral quark-(soliton model, based on the calculation of the electromagnetic and tensor form factors of the pion and the nucleon. The results for the transverse spin densities of the quark inside a pion are in good agreement with the recent lattice data, while those of the nucleon show similar features to the lattice results. We also present the first results of the transverse spin densities of the strange quark inside a nucleon.

Nam Seung-il

2012-02-01

126

Nucleon wave functions and QCD sum rules  

International Nuclear Information System (INIS)

We use QCD sum rules to study the first few moments of the quark distribution amplitudes of the nucleon, using the same auxiliary operators as Chernyak and Zhitnitsky. We obtain different results for the correlators in the euclidean region, leading in turn to different quantitative results for the quark distribution amplitudes. The asymmetry found by Chernyak and Zhitnitsky is confirmed, but is reduced in magnitude. (orig.)

127

Nucleon structure from lattice QCD - recent achievements and perspectives  

CERN Document Server

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

128

Nucleon structure from lattice QCD – recent achievements and perspectives  

Directory of Open Access Journals (Sweden)

Full Text Available 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 ?-terms, which involve the calculation of disconnected quark loop contributions.

Alexandrou Constantia

2014-06-01

129

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)

130

Nucleon Structure and hyperon form factors from lattice QCD  

International Nuclear Information System (INIS)

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(26), consistent with the Adelaide-JLab Collaboration's result. The hyperon Sigma Collaboration's result. The hyperon Sigma and Xi axial coupling constants are also performed for the first time in a lattice calculation, g#Sigma##Sigma# = 0.441(14) and g#Xi##Xi# = -0.277(11)

131

Recent experimental results from SLAC on the nucleon spin structure  

Energy Technology Data Exchange (ETDEWEB)

Recent precise measurements at SLAC of the spin structure function g{sub 1} for proton using deep inelastic scattering of polarized electrons from a polarized ammonia target are presented. The first moment evaluated at the average experimental Q{sup 2} = 3 (GeV/c){sup 2} is determined, in agreement with previous results but well below the Ellis-Jaffe sum rule prediction. The analysis of this results in term of Quark Parton Model implies that the quarks carry 0.29{+-}0.10 of the nucleon helicity. (author). 16 refs., 3 figs.

Terrien, Y.; E142, E143 Collaborations

1994-10-01

132

Spin and Orbital Angular Momentum Distribution Functions of the Nucleon  

CERN Document Server

A theoretical prediction is given for the spin and orbital angular momentum distribution functions of the nucleon within the framework of an effective quark model of QCD, i.e. the chiral quark soliton model. An outstanding feature of the model is that it predicts fairly small quark spin fraction of the nucleon $\\Delta \\Sigma \\simeq 0.35$, which in turn dictates that the remaining 65% of the nucleon spin is carried by the orbital angular momentum of quarks and antiquarks at the model energy scale of $Q^2 \\simeq 0.3 {GeV}^2$. This large orbital angular momentum necessarily affects the scenario of scale dependence of the nucleon spin contents in a drastic way.

Wakamatsu, M

2000-01-01

133

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

134

Photoproduction of nucleon resonances and their structure  

International Nuclear Information System (INIS)

Review of available data on radiative decay of non-strange nucleon resonators is presented. The radiative decay amplirude values presented by different authors differ appreciably, which testifies to availability of significant systematic errors. Determination of amplitude of electric quadrupole excitation of ?33(1232) isobar and R11(1440) Roper resonance, arousing great interest due to possibilities of studying features of quark interaction in nucleons and search of hydride (quark-gluon) states, is considered in details. 87 refs.; 5 tabs

135

Model independent results for nucleon structure  

Digital Repository Infrastructure Vision for European Research (DRIVER)

I review recent results regarding the nucleon charge and magnetization densities as well as the shape of the nucleon. First, some phenomenolgical considerations that show that the shape of the proton is not round are discussed. Then model independent results regarding the neutron and proton charge density, and the proton magnetization density are presented. Finally, I show how the spin-dependent densities that reveal the shape of the proton can be measured via their relation...

Miller, Gerald A.

2008-01-01

136

Probing nucleon structure on the lattice  

Energy Technology Data Exchange (ETDEWEB)

The QCDSF/UKQCD collaboration has an ongoing program to calculate nucleon matrix elements with two flavours of dynamical O(a) improved Wilson fermions. Here we present recent results on the electromagnetic form factors, the quark momentum fraction left angle x right angle and the first three moments of the nucleon's spin-averaged and spin-dependent generalised parton distributions, including preliminary results with pion masses as low as 320 MeV. (orig.)

Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Department, Inst. fuer Theoretische Physik T39; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)

2006-08-15

137

Taylor-Series Method for Four-Nucleon Wave Functions.  

Science.gov (United States)

Taylor-series method for transforming the infinite or finite well two-nucleon wave functions from individual coordinates to relative and c.m. coordinates, by expanding the single particle shell model wave functions around c.m. of the system, is generalize...

A. Sandulescu, I. Tarnoveanu, M. Rizea

1977-01-01

138

Light flavor sea-quark asymmetry for the spin-dependent distribution functions of the nucleon  

CERN Document Server

The theoretical predictions of the chiral quark soliton model for the unpolarized and longitudinally polarized structure functions of the nucleon are compared with recent high energy data. The theory is shown to explain all the qualitatively noticeable features of the existing experiments, including the light flavor sea-quark asymmetry for the unpolarized distribution functions established by the NMC measurement as well as very small quark spin fraction of the nucleon indicated by the EMC measurement. Another unique feature of the model is that it predicts sizably large isospin asymmetry also for the spin-dependent sea-quark distribution functions.

Wakamatsu, M

2000-01-01

139

Study of excited nucleons and their structure  

Energy Technology Data Exchange (ETDEWEB)

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.

Burkert, Volker D. [JLAB, Newport News, VA (United States)

2014-01-01

140

Studies of the Nucleon Structure at Jefferson Lab  

Science.gov (United States)

The JLab 6 GeV electron beam has been used to study the nucleon's internal structure in the transition from the regime of strongly interacting quarks and gluons to the deep inelastic regime of quasi-free interactions. Elastic and inelastic electron scattering, including the measurement of polarization observables, has led to deeper insight into the complex spatial and spin structure of the nucleon. In this talk, I will discuss results on the electromagnetic nucleon elastic form factors and on nucleon resonance transition form factors of several excited states of the proton. I will also present recent measurements of the spin responses of protons and neutrons in inclusive and exclusive electro production processes. Finally, I will discuss the prospects of probing generalized parton distributions (GPDs) in measurement of processes such as deeply virtual Compton scattering, both with the current 6 GeV machine, as well as at the higher energies available after the JLab 12 GeV upgrade.

Burkert, Volker

2009-10-01

 
 
 
 
141

Hypernuclear structure and hyperon-nucleon interactions  

International Nuclear Information System (INIS)

The hyperon-nucleon G-matrix interactions derived from the Nijmegen and Juelich potentials are shown to have remarkably different spin character which should be reflected in light hypernuclei. Various outputs of the calculations are demonstrated in connection with the recent (?+, K+) data from KEK. A possibility of deducing ? spin-orbit splittings in ?16O and in heavy hypernuclei have been also discussed. (author)

142

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.)

143

Deeply virtual Compton scattering and nucleon structure  

Energy Technology Data Exchange (ETDEWEB)

Deeply Virtual Compton Scattering (DVCS) is the tool of choice to study Generalized Parton Distributions (GPD) in the nucleon. After a general introduction to the subject, a review of experimental results from various facilities is given. Following the first encouraging results, new generation dedicated experiments now allow unprecedented precision and kinematical coverage. Several new results were presented during the conference, showing significant progress in this relatively new field. Prospects for future experiments are presented. The path for the experimental determination of GPDs appears now open.

M. Garcon

2006-11-01

144

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.)

145

Flavor structure of the unpolarized and longitudinally-polarized sea-quark distributions in the nucleon  

CERN Document Server

It is now widely recognized that a key to unravel the nonperturbative chiral-dynamics of QCD hidden in the deep-inelastic-scattering observables is the flavor structure of sea-quark distributions in the nucleon. We analyze the flavor structure of the nucleon sea in both of the unpolarized and longitudinally polarized parton distribution functions (PDFs) within a single theoretical framework of the flavor SU(3) chiral quark soliton model (CQSM), which contains only one adjustable parameter $\\Delta m_s$, the effective mass difference between the strange and nonstrange quarks. A particular attention is paid to a nontrivial correlation between the flavor asymmetry of the unpolarized and longitudinally polarized sea-quark distributions and also to a possible particle-antiparticle asymmetry of the strange quark distributions in the nucleon. We also investigate the charge-symmetry-violation (CSV) effects in the parton distribution functions exactly within the same theretical framework, which is expected to provide u...

Wakamatsu, Masashi

2014-01-01

146

Delineating the polarized and unpolarized partonic structure of the nucleon  

CERN Document Server

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

147

Advanced nucleon electromagnetic structure model and charge proton rms radius  

Science.gov (United States)

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.; Dubni?ková, A. Z.

2013-12-01

148

Electromagnetic structure of the nucleons in the Skyrme model  

International Nuclear Information System (INIS)

The isoscalar electromagnetic structure of the nucleons is studied within the Skyrme model. The form factors are consistent with the assumption of rotating rigid charge distributions. The use of deuteron data to obtain the isoscalar form factor is discussed; available calculations indicate that the isoscalar charge distribution is consistent with the well-known dipole fit. 8 refs.; 3 figs

149

Nuclear structure approach to the nucleon-nucleus optical model  

International Nuclear Information System (INIS)

In the many body theory, several microscopic approaches to the optical model potential have been developed. If the optical potential is defined as a one body potential which is able to reproduce the scattering wave functions, Bell and Squires have shown its identification with the mass operator of the one particle Green function. In section I of this paper, the mass operator is calculated by summing up two classes of diagrams of the perturbation theory: the two particle ladder diagrams which lead to the Brueckner-Hartree-Fock potential and the particle-hole bubble diagrams which take into account two step processes with excitation of the target nucleus. Both contributions to the optical potential are discussed simultaneously with an attempt to compare their relative contributions. In section II the contribution of particle-hole diagrams is considered with some emphasis on the possible choices of the effective nucleon-nucleon interaction. Some results on nucleon-alpha and nucleon-calcium 40 potentials are presented. In section III a generalization of the approach of section II is developed for alpha-nucleus scattering and the complex optical potential is calculated for alpha-40Ca scattering. Section IV is devoted to some general conclusions. (orig.)

150

Nucleon-nucleon interactions  

International Nuclear Information System (INIS)

Nucleon-nucleon interactions are at the heart of nuclear physics, bridging the gap between QCD and the effective interactions appropriate for the shell model. We discuss the current status of NN data sets, partial-wave analyses, and some of the issues that go into the construction of potential models. Our remarks are illustrated by reference to the Argonne v18 potential, one of a number of new potentials that fit elastic nucleon-nucleon data up to 350 MeV with a ?2 per datum near 1. We also discuss the related issues of three-nucleon potentials, two-nucleon charge and current operators, and relativistic effects. We give some examples of calculations that can be made using these realistic descriptions of NN interactions. We conclude with some remarks on how our empirical knowledge of NN interactions may help constrain models at the quark level, and hence models of nucleon structure

151

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

CERN Document Server

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

152

Sum Rules for Nucleon GPDs and Border Function Formulation  

CERN Document Server

The newy developed approach to model nucleon generalized parton distributions (GPDs) H and E$ is based on two types of their representation in terms of double distributions. Within this approach, we re-consider the derivation of GPD sum rules that allow to use border functions H(x,x) and E(x,x) instead of full GPDs H(x,\\xi) and E(x,\\xi) in the integrals producing Compton form factors of deeply virtual Compton scattering. Using factorized DD Ansatz to model GPDs, we discuss the relation between the border functions and underlying parton densities. We find that a substantial contribution to H(x,x) border function comes from the extra term required by new DD representations and related to E(x,\\xi) GPD.

Radyushkin, A V

2013-01-01

153

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.

154

Polarized Structure Functions  

Science.gov (United States)

A review is given of new experimental results that provide information on the spin structure of the nucleon. Inclusive measurements on a longitudinally polarized deuterium target have completed a set of high precision studies of the polarized structure function g1(x) carried out at HERMES. A high luminosity experiment at SLAC on transversely polarized nucleon targets has produced data on the structure function g2(x). Measurements of the double-spin asymmetry for the photoproduction of pairs of oppositely charged high-pT hadron can be interpreted in terms of evidence for a positive gluon polarization. Exploratory measurements of the beam-spin asymmetry in deeply-virtual Compton scattering (at both HERMES and JLab) were successful, implying that this channel can - in principle - be used to study the total angular momentum carried by the quarks. Small single-target spin asymmetries observed at HERMES in semi-inclusive pion production experiments indicate that the only hitherto unmeasured leading order structure function, the transversity spin structure function h1(x), is non-zero.

van der Steenhoven, G.

2003-04-01

155

Transverse spin structure of the nucleon from lattice QCD simulations  

International Nuclear Information System (INIS)

We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72 (2005) 094020], we predict that the Boer-Mulders-function h1perpendicularto, describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks. (orig.)

156

Transverse spin structure of the nucleon from lattice QCD simulations  

Energy Technology Data Exchange (ETDEWEB)

We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72 (2005) 094020], we predict that the Boer-Mulders-function h{sub 1} {sup perpendicular} {sup to}, describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks. (orig.)

Goeckeler, M.; Schaefer, A. [Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik; Haegeler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R.; Zanotti, J.M. [Edinburgh Univ. (United Kingdom). School of Physics; Nakamura, Y.; Pleiter, D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Division, Dept. of Mathematical Sciences; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Stueben, H. [Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (ZIB) (Germany)

2006-12-15

157

Flavor structure of the unpolarized and longitudinally polarized sea-quark distributions in the nucleon  

Science.gov (United States)

It is now widely recognized that a key to unraveling the nonperturbative chiral dynamics of QCD hidden in the deep-inelastic-scattering observables is the flavor structure of sea-quark distributions in the nucleon. We analyze the flavor structure of the nucleon sea in both the unpolarized and longitudinally polarized parton distribution functions within the flavor SU(3) chiral quark-soliton model, which contains only one adjustable parameter, ?ms, the effective mass difference between the strange and nonstrange quarks. Particular attention is paid to a nontrivial correlation between the flavor asymmetry of the unpolarized and longitudinally polarized sea-quark distributions and also to a possible particle-antiparticle asymmetry of the strange-quark distributions in the nucleon. We also investigate the charge-symmetry-violation effects in the parton distribution functions exactly within the same theoretical framework, which is expected to provide us with valuable information on the relative importance of the asymmetry of the strange and antistrange distributions and the charge-symmetry-violation effects in the valence-quark distributions inside the nucleon in the resolution scenario of the so-called NuTeV anomaly in the extraction of the Weinberg angle.

Wakamatsu, M.

2014-08-01

158

The triton binding energy and the nd-scattering lengths with account of a quark nucleon structure  

International Nuclear Information System (INIS)

A simple model for the nucleon-nucleon interaction is suggested which takes into account the quark nucleon structure. Using this model the triton binding energy and the nd-scattering lengths are calculated

159

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

160

Insight into nucleon structure from lattice calculations of moments of parton and generalized parton distributions  

Energy Technology Data Exchange (ETDEWEB)

This talk presents recent calculations in full QCD of the lowest three moments of generalized parton distributions and the insight they provide into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon. In addition, new exploratory calculations in the chiral regime of full QCD are discussed.

J.W. Negele; R.C. Brower; P. Dreher; R. Edwards; G. Fleming; Ph. Hagler; U.M. Heller; Th. Lippert; A.V.Pochinsky; D.B. Renner; D. Richards; K. Schilling; W. Schroers

2004-04-01

 
 
 
 
161

An Overview of the Spin Structure of the Nucleon  

Science.gov (United States)

In the last decade, the spin structure of the nucleon has generated much experimental and theoretical interest in the nuclear physics community. Experimentally, following a series of successful experiments at CERN and SLAC, the HERMES collaboration at DESY continues to make new and exciting discoveries. The experiments underway at BNL (RHIC spin) and CERN (COMPASS experiment) are creating a new frontier of the field. In particular, these experiments will measure directly the gluon polarization in the nucleon for the first time. The polarized experiments at Jefferson Lab are too making unique and significant contributions to the nucleon spin physics. On the theoretical frontier, the formulation of the generalized parton distributions has led to an active investigation of a new class of high-momentum processes such as deeply virtual Compton scattering and exclusive meson production. The new distributions provide interesting information about the quark and gluon orbital motion in a QCD bound state. In this talk, I will review some of recent theoretical and experimental advances and discuss future prospects of the field.

Ji, Xiangdong

2001-10-01

162

Studies of nucleon resonance structure in exclusive meson electroproduction  

International Nuclear Information System (INIS)

Studies of the structure of excited baryons are key factors to the N* program at Jefferson Lab (JLab). 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 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 protons, along with Quantum Chromodynamics (QCD)-based approaches to the theoretical interpretation of these fundamental quantities. This program will afford access to the dynamics of the nonperturbative strong interaction responsible for resonance formation, and will be crucial in understanding the nature of confinement and dynamical chiral symmetry breaking in baryons, and how excited nucleons emerge from QCD. (author)

163

Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction  

Science.gov (United States)

Studies of the structure of excited baryons are key factors to the N* program at Jefferson Lab (JLab). 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 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 protons, along with Quantum Chromodynamics (QCD)-based approaches to the theoretical interpretation of these fundamental quantities. This program will afford access to the dynamics of the nonperturbative strong interaction responsible for resonance formation, and will be crucial in understanding the nature of confinement and dynamical chiral symmetry breaking in baryons, and how excited nucleons emerge from QCD.

Aznauryan, I. G.; Bashir, A.; Braun, V. M.; 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.; Gross, F.; 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.

2013-06-01

164

HERMES measurement of the spin structure of the nucleon  

International Nuclear Information System (INIS)

The HERMES experiment at the DESY Laboratory in Hamburg, Germany is designed to probe the spin structure of the nucleon by using deep inelastic scattering (DIS) of longitudinally polarized positrons on longitudinally and transversely polarized targets. The HERMES spectrometer has the ability to not only identify the scattered DIS positrons but as well the hadrons in coincidence with the scattered positrons, enabling spin decomposition through flavor tagging. This paper presents an overview of the HERMES experiment and gives physics results of analyses performed with the 1995 data. (author)

165

Polarized lepton-nucleon scattering  

International Nuclear Information System (INIS)

Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions

166

Ab initio coupled-cluster approach to nuclear structure with modern nucleon-nucleon interactions  

CERN Document Server

We perform coupled-cluster calculations for the doubly magic nuclei 4He, 16O, 40Ca and 48Ca, for neutron-rich isotopes of oxygen and fluorine, and employ "bare" and secondary renormalized nucleon-nucleon interactions. For the nucleon-nucleon interaction from chiral effective field theory at order next-to-next-to-next-to leading order, we find that the coupled-cluster approximation including triples corrections binds nuclei within 0.4 MeV per nucleon compared to data. We employ interactions from a resolution-scale dependent similarity renormalization group transformations and assess the validity of power counting estimates in medium-mass nuclei. We find that the missing contributions due to three-nucleon forces are consistent with these estimates. For the unitary correlator model potential, we find a slow convergence with respect to increasing the size of the model space. For the G-matrix approach, we find a weak dependence of ground-state energies on the starting energy combined with a rather slow convergence...

Hagen, G; Dean, D J; Hjorth-Jensen, M

2010-01-01

167

Ab initio coupled-cluster approach to nuclear structure with modern nucleon-nucleon interactions  

Science.gov (United States)

We perform coupled-cluster calculations for the doubly magic nuclei He4, O16, Ca40,48, for neutron-rich isotopes of oxygen and fluorine, and employ “bare” and secondary renormalized nucleon-nucleon interactions. For the nucleon-nucleon interaction from chiral effective field theory at order next-to-next-to-next-to leading order, we find that the coupled-cluster approximation including triples corrections binds nuclei within 0.4 MeV per nucleon compared to data. We employ interactions from a resolution-scale dependent similarity renormalization group transformations and assess the validity of power counting estimates in medium-mass nuclei. We find that the missing contributions from three-nucleon forces are consistent with these estimates. For the unitary correlator model potential, we find a slow convergence with respect to increasing the size of the model space. For the G-matrix approach, we find a weak dependence of ground-state energies on the starting energy combined with a rather slow convergence with respect to increasing model spaces. We also analyze the center-of-mass problem and present a practical and efficient solution.

Hagen, G.; Papenbrock, T.; Dean, D. J.; Hjorth-Jensen, M.

2010-09-01

168

Ab Initio Coupled-Cluster Approach to Nuclear Structure with Modern Nucleon-Nucleon Interactions  

Energy Technology Data Exchange (ETDEWEB)

We perform coupled-cluster calculations for the doubly magic nuclei ^{4}He, ^{16}O, and ^{40,48}Ca for neutron-rich isotopes of oxygen and fluorine, and employ "bare" and secondary renormalized nucleon-nucleon interactions. For the nucleon-nucleon interaction from chiral effective field theory at order next-to-next-to-next-to leading order, we find that the coupled-cluster approximation including triples corrections binds nuclei within 0.4 MeV per nucleon compared to data. We employ interactions from a resolution-scale dependent similarity renormalization group transformation and assess the validity of power-counting estimates in medium-mass nuclei. We find that the missing contributions due to three-nucleon forces are consistent with these estimates. For the unitary correlator model potential, we find a slow convergence with respect to increasing the size of the model space. For the G-matrix approach, we find a weak dependence of ground-state energies on the starting energy combined with a rather slow convergence with respect to increasing model spaces. We also analyze the center-of-mass problem and present a practical and efficient solution.

Hagen, Gaute [ORNL; Papenbrock, T. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Dean, David Jarvis [ORNL; Hjorth-Jensen, M. [University of Oslo, Norway

2010-01-01

169

Light cone nucleon wave function in the quark-soliton model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The light-cone wave function of the nucleon is calculated in the limit N_c -> infinity in the quark-soliton model inspired by the theory of the instanton vacuum of QCD. The technique of the finite time evolution operator is used in order to derive expressions for all components of the Fock vector describing the nucleon in the infinite momentum frame. It is shown that nucleon wave function for large N_c can be expressed in terms of the wave function of the discrete level in ...

Petrov, V. Yu; Polyakov, M. V.

2003-01-01

170

Pion-nucleon vertex function and the Chew-Low model  

Energy Technology Data Exchange (ETDEWEB)

We provide an interpretation of the cutoff function used in the Chew-Low theory of pion-nucleon scattering. It is shown that this function may be related to the pion-pion interaction which is not explicitly considered in the Chew-Low approach. Using a previously developed model for the pion-nucleon vertex function, we then perform a ''parameter-free'' Chew-Low calculation which predicts the P/sub 33/ resonance quite well.

Nutt, W.T.

1977-09-01

171

Nucleon electromagnetic structure studies in the spacelike and timelike regions  

Energy Technology Data Exchange (ETDEWEB)

The thesis investigates the nucleon structure probed by the electromagnetic interaction. One of the most basic observables, reflecting the electromagnetic structure of the nucleon, are the form factors, which have been studied by means of elastic electron-proton scattering with ever increasing precision for several decades. In the timelike region, corresponding with the proton-antiproton annihilation into a electron-positron pair, the present experimental information is much less accurate. However, in the near future high-precision form factor measurements are planned. About 50 years after the first pioneering measurements of the electromagnetic form factors, polarization experiments stirred up the field since the results were found to be in striking contradiction to the findings of previous form factor investigations from unpolarized measurements. Triggered by the conflicting results, a whole new field studying the influence of two-photon exchange corrections to elastic electron-proton scattering emerged, which appeared as the most likely explanation of the discrepancy. The main part of this thesis deals with theoretical studies of two-photon exchange, which is investigated particularly with regard to form factor measurements in the spacelike as well as in the timelike region. An extraction of the two-photon amplitudes in the spacelike region through a combined analysis using the results of unpolarized cross section measurements and polarization experiments is presented. Furthermore, predictions of the two-photon exchange effects on the e{sup +}p/e{sup -}p cross section ratio are given for several new experiments, which are currently ongoing. The two-photon exchange corrections are also investigated in the timelike region in the process p anti p ? e{sup +}e{sup -} by means of two factorization approaches. These corrections are found to be smaller than those obtained for the spacelike scattering process. The influence of the two-photon exchange corrections on cross section measurements as well as asymmetries, which allow a direct access of the two-photon exchange contribution, is discussed. Furthermore, one of the factorization approaches is applied for investigating the two-boson exchange effects in parity-violating electron-proton scattering. In the last part of the underlying work, the process p anti p??{sup 0}e{sup +}e{sup -} is analyzed with the aim of determining the form factors in the so-called unphysical, timelike region below the two-nucleon production threshold. For this purpose, a phenomenological model is used, which provides a good description of the available data of the real photoproduction process p anti p?>?{sup 0}?.

Guttmann, Julia

2013-07-23

172

Quark structure of the nucleon and angular asymmetry of proton-neutron hard elastic scattering.  

Science.gov (United States)

We investigate an asymmetry in the angular distribution of hard elastic proton-neutron scattering with respect to the 90 degrees center of mass scattering angle and demonstrate that it's magnitude 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 predicts an angular asymmetry opposite to that of experimental observations. We found that the quark wave function based on the diquark picture of the nucleon produces a correct asymmetry. Comparison with the data allowed us to show that the vector diquarks contribute around 10% in the nucleon wave function and they are in negative phase relative to the scalar diquarks. These observations are essential in constraining QCD models of a nucleon. PMID:20366029

Granados, Carlos G; Sargsian, Misak M

2009-11-20

173

Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction  

CERN Document Server

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

174

Last experimental results obtained at SLAC on the nucleon spin structure  

Energy Technology Data Exchange (ETDEWEB)

Recent precise measurements of the spin structure function g{sub 1} 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){sup 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.

Terrien, Y.; E142, E143 Collaborations

1994-10-01

175

Leading nucleons from peripheral processes in lepton deep inelastic scattering and the nucleon structure  

CERN Document Server

The experimental information on nucleon production in lepton deep inelastic scattering (DIS) is rather scarce. Recently there is a growing interest in understanding the mechanism of the production of baryons in DIS, stimulated by recent results on leading protons and neutrons from electron-proton scattering at HERA. I review on different peripheral mechanisms of nucleon (proton or neutron) production in lepton DIS and discuss their role in understanding the spectra of nucleons for both fixed target and collider experiments. In DIS ep to e'Xh, the QCD hardness scale gradually diminishes from the hard scale, Q/sup 2/, in the virtual photon (current) fragmentation region to the soft, hadronic, scale in the proton (target) fragmentation region. This suggests a similarity of the inclusive spectra of leading protons and neutrons, h=p, n, in high energy hadron-proton collisions and in lepton DIS at small Bjorken-x. The semi-inclusive cross section for production of slow protons in charged-current deep inelastic (ant...

Szczurek, A

1999-01-01

176

GPDs and underlying spin structure of the nucleon  

CERN Document Server

It is shown that, based only upon two empirically known facts besides two reasonable theoretical postulates, we are inevitably led to a model-independent conclusion that the quark orbital angular momentum carries nearly half of the total nucleon spin at the low energy scale of nonperturbative QCD. Also shown are explicit model predictions for the forward limit of the unpolarized spin-flip GPDs, which are believed to give valuable information on the distributions of quark angular momentum inside the nucleon.

Wakamatsu, M

2005-01-01

177

Light cone nucleon wave function in the quark-soliton model  

CERN Document Server

The light-cone wave function of the nucleon is calculated in the limit N_c -> infinity in the quark-soliton model inspired by the theory of the instanton vacuum of QCD. The technique of the finite time evolution operator is used in order to derive expressions for all components of the Fock vector describing the nucleon in the infinite momentum frame. It is shown that nucleon wave function for large N_c can be expressed in terms of the wave function of the discrete level in the self-consistent meson field and light cone wave functions of 1,2, etc mesons. The 3-quark components of the nucleon and Delta-resonance are estimated. Wave function of the nucleon appears to be positive in the whole region of x and it has rather small asymmetry. It differs strongly both from Chernyak-Zhitnitsky wave function and the asymptotic one. Large momentum transfer asymptotic of the electromagnetic and axial form factors is discussed.

Petrov, V Yu

2003-01-01

178

Search for three-nucleon force effects on the longitudinal response function of 4He  

International Nuclear Information System (INIS)

A detailed study of the 4He longitudinal response function RL(?,q) is performed at different kinematics, with particular emphasis on the role of three-nucleon forces. The effects reported are the results of an ab initio calculation where the full four-body continuum dynamics is considered via the Lorentz integral transform method. The contributions of the various multipoles to the longitudinal response function are analyzed, and integral properties of the response are discussed as well. The Argonne V18 nucleon-nucleon interaction and two three-nucleon force models (Urbana IX and Tucson-Melbourne') are used. At lower momentum transfers (q?200 MeV/c) three-nucleon forces play an important role. One even finds a dependence of RL on the three-nucleon force model itself, with differences of up to 10%. Thus a Rosenbluth separation of the inclusive electron scattering cross section of 4He at low momentum transfers would be of great value for differentiating among force models.

179

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

180

A study of nucleon spin structure through polarised muon polarised proton deep inelastic scattering  

International Nuclear Information System (INIS)

A measurement has been made of the spin asymmetry in the deep inelastic scattering of longitudinally polarised muons by longitudinally polarised protons at incident energies of 100, 120 and 200 GeV. The kinematic region, x from 0.01 to 0.70 and Q2 from 1.5 to 70 (GeV/c)2, covered by the experiment greatly extends that of the previous measurements. The new results for the asymmetry are found to be very compatible with the earlier results in their region of overlap but lie significantly below the prediction of the favoured model for nucleon spin structure at the time. The present data are compared with more recent models which give good agreement. The proton g1 structure function is deduced and its integral over x evaluated. This is found to be in contradiction with the Ellis-Jaffe sum rule and, holding the Bjorkin sum rule as sacrosanct, implies that the quarks carry only a very small fraction of the nucleon spin. (author)

 
 
 
 
181

Nucleon structure from 2+1f dynamical DWF lattice QCD at nearly physical pion mass  

CERN Document Server

Current status of nucleon structure calculations with joint RBC and UKQCD 2+1-flavor dynamical domain-wall fermions (DWF) lattice QCD is reported: Two ensembles with pion mass of about (m_\\pi=170) MeV and 250 MeV are used. The lattice cutoff is set at about 1.4 GeV, allowing a large spatial volume of about (L=4.6) fm across while maintaining a sufficiently small residual breaking of chiral symmetry with the dislocation-suppressing-determinant-ratio (DSDR) gauge action. We calculate all the isovector form factors and some low moments of isovector structure functions. We confirm the finite-size effect in isovector axialvector-current form factors, in particular the deficit in the axial charge and its scaling in terms of (m_\\pi L), that we reported from our earlier calculation at heavier pion masses.

Ohta, Shigemi

2011-01-01

182

Nucleon spin structure, topological susceptibility and the $\\eta$' singlet axial vector coupling  

CERN Document Server

The observed small value of the first moment of the polarized nucleon spin structure function g_1 may be interpreted, in the Veneziano--Shore approach, as a suppression of the first moment \\chi^\\prime(0) of the QCD topological susceptibility. I give an extension of the Witten--Veneziano argument for the U(1) problem, which yields the O(1/N) correction to the N = \\infty relation \\chi^\\prime(0)/F^2_0 = 1 (where F_0 is the \\eta^\\prime axial vector coupling).The correction, although negative, seems too small to account for the data. I further argue that the (\\eta,\\eta^\\prime)\\rightarrow\\gamma\\gam ma and J/\\psi\\rightarrow (\\eta , \\eta^\\prime)\\gamma decays indicate an enhancement rather than a suppression of F_0. A substantial gluon-like contribution in \\langle 0\\vert\\partial^\\mu j^{(0)}_{\\mu_5} \\vert\\gamma\\gamma \\rangle \\vert_{q^2=0},which could parallel a similar one in the corresponding nucleon matrix element,is suggested.

Grunberg, G

1996-01-01

183

Global Study of Nuclear Structure Functions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the results of a phenomenological study of unpolarized nuclear structure functions for a wide kinematical region of x and Q^2. As a basis of our phenomenology we develop a model which takes into account a number of different nuclear effects including nuclear shadowing, Fermi motion and binding, nuclear pion excess and off-shell correction to bound nucleon structure functions. Within this approach we perform a statistical analysis of available data on the ratio of ...

Kulagin, S. A.; Petti, R.

2004-01-01

184

Flavor Decomposition of Nucleon Structure at a Neutrino Factory  

CERN Document Server

We explore the possibilities for measuring the quark content of the proton and neutron using neutrino beams produced at a muon storage ring. Because of the nature of the beams, small nuclear targets such as hydrogen and deuterium can be considered, as well as polarized targets. The statistics expected from these targets are calculated using nominal muon storage ring intensities, and the resulting statistical errors on the numerous structure functions available are given, for both polarized and unpolarized targets. It is shown that with a relatively small target, the structure functions F_2, xF_3, xg_1 and xg_5 for neutrinos and antineutrinos on protons and deuterium, either unpolarized or polarized, could be determined with excellent precision over most of the accessible kinematic range.

Ball, R D; McFarland, K S; Ball, Richard D.; Harris, Deborah A.; Farland, Kevin S. Mc

2000-01-01

185

The spin structure of nucleons and deep inelastic scatterings  

CERN Document Server

Based on a simple model which is compatible with the idea of the static quark model and the parton model, the polarized structure functions of proton and deuteron, two-spin asymmetries of \\pi ^0 in polarized pp reactions and inelastic J/\\psi productions in polarized lepton-proton collisions are analyzed. In particular, an important role of polarized gluon distributions is pointed out.

Mori, T

1994-01-01

186

Experimental Studies of Quark-Gluon Structure of Nucleons and Nuclei  

International Nuclear Information System (INIS)

The NMSU group has a lengthy history in the study of the nucleon structure and in particular its spin structure in terms of its fundamental constituents. This line of research is continuing in our current involvement in experiments at Brookhaven National Lab and the Thomas Jefferson National Accelerator Facility

187

On the treatment of the nuclear matter problem with phenomenological and realistic nucleon-nucleon interactions in the framework of the Green function  

International Nuclear Information System (INIS)

We performed a self-consistent calculation of the nuclear matter properties within the Green's function scheme. Essential is the self-energy ?(p;epsilon) (effective single-particle potential or mass operator), which determines the properties of the system. Necessary for the calculation of the effective single-particle potential is the knowledge of the scattering matrix (T-matrix) in matter, which plays in the calculation the role of an effective two-body potential. Our calculations were performed for the 'phenomenological' hardcore potential of Hamada-Johnston, the Reid-soft-core potential and the 'realistic' Paris-Nucleon-Nucleon potential. A binding energy of -5.88 MeV per nucleon was obtained. For the Reid-soft-core potential and the Paris potential we found -11 MeV and -12.2 MeV respectively. (orig./HSI)

188

Statistical description of the flavor structure of the nucleon sea  

CERN Document Server

The theoretical foundations of the quantum statistical approach to parton distributions are reviewed together with the phenomenological motivations from a few specific features of Deep Inelastic Scattering data. The chiral properties of QCD lead to strong relations between quarks and antiquarks distributions and automatically account for the flavor and helicity symmetry breaking of the sea. We are able to describe both unpolarized and polarized structure functions in terms of a small number of parameters. The extension to include their transverse momentum dependence will be also briefly considered.

Soffer, Jacques; Buccella, Franco

2014-01-01

189

Lattice investigations of nucleon structure at light quark masses  

Energy Technology Data Exchange (ETDEWEB)

Lattice simulations of hadronic structure are now reaching a level where they are able to not only complement, but also provide guidance to current and forthcoming experimental programmes at, e.g. Jefferson Lab, COMPASS/CERN and FAIR/GSI. By considering new simulations at low quark masses and on large volumes, we review the recent progress that has been made in this exciting area by the QCDSF/UKQCD collaboration. In particular, results obtained close to the physical point for several quantities, including electromagnetic form factors and moments of ordinary parton distribution functions, show some indication of approaching their phenomenological values. (orig.)

Goeckeler, M.; Nakamura, Y.; Schaefer, A. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R.; Zanotti, J.M. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Pleiter, D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Division; Schierholz, G. [Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Stueben, H. [Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (ZIB) (Germany)

2009-12-15

190

Polarized Structure Functions with Neutrino Beams  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We review the potential impact of neutrino data on the determination of the spin structure of the nucleon. We show that a flavour decomposition of the parton structure of the nucleon as required by present-day precision phenomenology could only be achieved at a neutrino factory. We discuss how neutrino scattering data would allow a full resolution of the nucleon spin problem.

Forte, Stefano

2005-01-01

191

Study of two-nucleon wave functions in 3He  

International Nuclear Information System (INIS)

The 3He(p,2p)pn reaction has been studied in a quasi-free scattering arrangement characterized by (anti) p(recoil) = 0 and various excitation or total energies E(recoil) of the unobserved p-n pair. Data were obtained at 250 and 400 MeV at symmetric and asymmetric pairs of angles. The 3He spectral function deduced in the framework of the plane wave impulse approximation is compared to the predictions of Faddeev and variational calculations. Comparisons are also made with p-n relative motion momentum distributions as the overlap between plane waves for the p-n pair and Irving, Irving-Gunn and Khanna wave functions for 3He

192

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.)

193

Is nucleon deformed?  

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

194

Nuclear structure functions at low- in a holographic approach  

Science.gov (United States)

Nuclear effects in deep inelastic scattering at low 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 . 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 and on the mean square distances, related to a parameter , among quarks and gluons in the target. The holographic structure function per nucleon in a nucleus is evaluated showing that a rescaling of the typical nucleon size, and , due to nuclear binding, can be reabsorbed in a -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.

Agozzino, Luca; Castorina, Paolo; Colangelo, Pietro

2014-04-01

195

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

196

Structure of light neutron-rich nuclei through nucleon transfer and knockout reactions  

International Nuclear Information System (INIS)

Changes in shell closures through nucleon transfer and nucleon knockout reactions as spectroscopic probes are discussed. The intruder s-orbital in the ground and excited states of 12Be is studied through the 11Be(d,p) reaction. Signature of the 02+ long-lived state having an s-wave halo-like structure in 12Be is observed. One-neutron knockout from 24O shows a large spectroscopic factor for the s-orbital thereby establishing it as a new doubly magic nucleus at the drip-line.

197

The Jefferson Lab 12 GeV program on nucleon structure  

International Nuclear Information System (INIS)

This talk is intended as a brief overview of the Jefferson Lab program to study the multi-dimensional structure of the nucleon in coordinate and momentum space. The experimental program is extensive and given the available space only selected samples can be discussed. PACS 13.40.Gp – Electromagnetic form factors.

198

Nucleon structure by Lattice QCD computations with twisted mass fermions; Etude de la structure du nucleon par des calculs de QCD sur reseau avec des fermions de masse twistee  

Energy Technology Data Exchange (ETDEWEB)

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)

Harraud, P.A.

2010-11-15

199

Microscopically-constrained Fock energy density functionals from chiral effective field theory. I. Two-nucleon interactions  

CERN Document Server

The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in arXiv:0910.4979 by Gebremariam {\\it et al.} to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions at next-to-next-to-leading-order (N$^2$LO). The structure of the chiral interactions is such that each coupling in the DME Fock functional can be decomposed into a cutoff-dependent coupling {\\it constant} arising from zero-range contact interactions and a cutoff-independent coupling {\\it function} of the density arising from the universal long-range pion exchanges. This motivates a new microscopically-guided Skyrme phenomenology where the density-dependent couplings associated with the underlying pion-exchange interactions...

Gebremariam, B; Duguet, T

2010-01-01

200

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

 
 
 
 
201

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

International Nuclear Information System (INIS)

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*(1535), the parity partner of the nucleon. These results show a stronger deviation from the asymptotic form. (orig.)

202

Local Duality Predictions for x ~ 1 Structure Functions  

CERN Document Server

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

203

Contribution of vector mesons to F2 structure function  

Science.gov (United States)

In recent years we have used meson cloud to investigate polarized and unpolarized nucleon struc- ture functions [1-6]. Here we present the contribution of vector mesons along with their baryon octets and decuplets counterparts to the meson cloud [1]. For the bare nucleon we use a quark- diquark model. Our work has shown that it is necessary for the core nucleon to have a spin-1 diquark component. In this work we will use superposition of spin-0 and spin-1 diquarks as the core nucleon to calculate quark distribution functions. Then, using pQCD, an initial gluon distri- bution is generated inside the core nucleon. The physical nucleon is assumed to be a superposition of the bare nucleon plus the virtual light-cone Fock states of the baryon-meson pairs. The initial distributions are evolved using DGLAP equations. The F2 structure functions calculated from the evolved distributions are compared with NMC and Zeus results along with a CTEQ fits. Also, we will show that the meson cloud is a contributing factor to sea quark asymmetry and one needs both pseuoscalar mesons and vector mesons to account fully for the Gottfried sum-rule violation.

Zamani, F.

204

Spin-dependent Nucleon Structure Studies at MIT/Bates  

Science.gov (United States)

We present preliminary results from recent measurements of the proton, neutron and deuterium electro-magnetic form factors obtained by the BLAST collaboration at the MIT/Bates Linear Accelerator Facility. BLAST (Bates Large Acceptance Spectrometer Toroid) is a large-acceptance multi-purpose detector dedicated to studies of exclusive spin-dependent electron scattering from internal polarized targets. BLAST makes use of stored electron beam currents in excess of 150 mA with a 60-70% polarization. The electron beam is let through a 15 mm diameter, 60 cm long open-ended storage cell which is fed with ultra-pure, high-polarization H1,D1 gas from an Atomic Beam Source. The target polarization can be rapidly reversed between different vector and tensor target states, thus minimizing systematic uncertainties. The target spin can be oriented to any in-plane direction via a set of Helmholtz coils. Target polarizations in the storage cell of up to 80% (vector) and 70% (tensor) have been routinely achieved over a period of several months. Our data on the D?(e?,e'n) reaction off vector polarized deuterium allow for a unique extraction of the neutron charge form factor GEn. At same time, complementary measurements of GMn, T20 and the spin-dependent nucleon momentum distributions in deuterium are obtained via the D?(e?,e'), D?(e?,e'd) and D?(e?,e'p) reactions. In addition, BLAST data on vector polarized hydrogen will provide novel measurements of the GE/GM form-factor ratio on the proton as well as of the spin-dependent electro-excitation of the ?(1232) resonance. Such comprehensive program on few body physics is now well underway and preliminary data will be presented.

Botto, T.

2005-05-01

205

Structure Functions at Low Q2: Target Mass Corrections  

International Nuclear Information System (INIS)

We discuss recent developments in the study of structure functions at low Q2, 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 Q2 in the x -> 1 limit

206

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

207

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.)

208

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

209

The Structure of the Nucleon and its Excited States  

International Nuclear Information System (INIS)

The past year has been an exciting and productive one for particle physics research at Abilene Christian University. The thrust of our experimental investigations is the study of the nucleon and its excited states. Laboratories where these investigations are presently being conducted are the AGS at Brookhaven, Fermilab and LAMPF. Some analysis of the data for experiments at the Petersburg Nuclear Physics Institute (Gatchina, Russia) is still in progress. Scheduling of activities at different laboratories inevitably leads to occasional conflicts. This likelihood is increased by the present budget uncertainties at the laboratories that make long-term scheduling difficult. For the most part, the investigators have been able to avoid such conflicts. Only one experiment received beam time in 1994 (E890 at the AGS). The situation for 1995-1996 also appears manageable at this point. E890 and another AGS experiment (E909) will run through May, 1995. El 178 at LAMPF is presently scheduled for August/September 1995. E866 at Fermilab is scheduled to start in Spring/Summer 1996. Undergraduate student involvement has been a key element in this research contract since its inception. Summer students participated at all of the above laboratories in 1994 and the same is planned in 1995. A transition to greater involvement by graduate students will provide cohesiveness to ACU involvement at a given laboratory and full-time on-site involvement in the longer running experiments at FNAL and BNL. Funds to support a full-time graduate student are requested this year. Finally, collaboration by Russian, Croatian and Bosnian scientists has proven to be mutually beneficial to these experimental programs and to the overall programs at the institutions involved. Past support has been augmented by other grants from government agencies and from the Research Council at Abilene Christian University. Additional funds are requested in this renewal to enable more programmatic support for these efforts, so that long-range plans can be made to carry out the experiments and to perform the analysis

210

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

Science.gov (United States)

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

211

Comparative analysis of the transversities and the longitudinally polarized distribution functions of the nucleon  

CERN Document Server

A first empirical extraction of the transversity distributions for the $u$- and $d$-quarks has been done by Anselmino {\\it et al.} based on the combined global analysis of the measured azimuthal asymmetries in semi-inclusive deep inelastic scatterings and those in $e^+ e^- \\to h_1 h_2 X$ processes. Although with large uncertainties, the determined transversity distributions already appear to reveal a remarkable qualitative difference with the corresponding longitudinally polarized distributions. We point out that this difference contains very important information on internal spin structure of the nucleon.

Wakamatsu, M

2007-01-01

212

Nucleon structure from 2+1 flavor domain wall QCD at nearly physical pion mass  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The RBC and UKQCD collaborations have been investigating hadron physics in numerical lattice quantum chromodynamics (QCD) with (2+1) flavors of dynamical domain wall fermions (DWF) quarks that preserves continuum-like chiral and flavor symmetries. The strange quark mass is adjusted to physical value via reweighting and degenerate up and down quark masses are set as light as possible. In a recent study of nucleon structure we found a strong dependence on pion mass and lattice...

Ohta, Shigemi; Rbc, For The; Collaborations, Ukqcd

2011-01-01

213

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

214

Neutrino charged-current structure functions  

International Nuclear Information System (INIS)

Charged current total cross sections and structure functions were extracted from neutrino and antineutrino data taken with the Fermilab narrow band beam. The cross section results are sigma/sup nu//E = 0.701 +- 0.004 +- 0.025 x 10-38 cm2/GeV and sigma/sup nu-bar//E = 0.350 +- 0.04 +- 0.022 x 10-38 cm2/GeV. The structure functions exhibit scaling violations. A comparison with structure functions obtained in muon scattering experiments indicates a ratio consistent with 18/5 within the systematic errors of both experiments. The structure function function xF3 is used to test the Gross-Llewellyn Smith sum rule. The data is in agreement with the prediction of 3 for the number of valence quarks on the nucleon

215

Transverse spin structure of the nucleon from lattice-QCD simulations.  

Science.gov (United States)

We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based on two flavors of clover-improved Wilson fermions and Wilson gluons. We find significant contributions from certain quark helicity flip generalized parton distributions, leading to strongly distorted densities of transversely polarized quarks in the nucleon. In particular, based on our results and recent arguments by Burkardt [Phys. Rev. D 72, 094020 (2005)], we predict that the Boer-Mulders function h(1/1), describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks. PMID:17677836

Göckeler, M; Hägler, Ph; Horsley, R; Nakamura, Y; Pleiter, D; Rakow, P E L; Schäfer, A; Schierholz, G; Stüben, H; Zanotti, J M

2007-06-01

216

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

Science.gov (United States)

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+? 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.; Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E.

2014-01-01

217

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

CERN Document Server

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

218

What we can learn about nucleon spin structure from recent data  

CERN Document Server

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 have to be large in order to be consistent with either set of experimental data. However, it appears that the discrepancies in the implications of these data cannot be resolved with any simple theoretical arguments. We conclude that more experiments must be performed in order to adequately determine the fraction of spin carried by each of the nucleon constituents.

Goshtasbpour, M; Ramsey, Gordon P

1997-01-01

219

Nucleon structure from 2+1 flavor domain wall QCD at nearly physical pion mass  

CERN Document Server

The RBC and UKQCD collaborations have been investigating hadron physics in numerical lattice quantum chromodynamics (QCD) with (2+1) flavors of dynamical domain wall fermions (DWF) quarks that preserves continuum-like chiral and flavor symmetries. The strange quark mass is adjusted to physical value via reweighting and degenerate up and down quark masses are set as light as possible. In a recent study of nucleon structure we found a strong dependence on pion mass and lattice spatial extent in isovector axialvector-current form factors. This is likely the first credible evidence for the pion cloud surrounding nucleon. Here we report the status of nucleon structure calculations with a new (2+1)-flavor dynamical DWF ensembles with much lighter pion mass of 180 and 250 MeV and a much larger lattice spatial exent of 4.6 fm. A combination of the Iwasaki and dislocation-suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while ke...

Ohta, Shigemi

2011-01-01

220

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

 
 
 
 
221

Polarized deep inelastic scattering at high energies and parity violating structure functions  

CERN Document Server

A comprehensive analysis of deep inelastic scattering of polarized charged leptons on polarized nucleons is presented; weak interaction contributions, both in neutral and charged current processes, are taken into account and the parity violating polarized nucleon structure functions are studied. Possible ways of their measurements and their interpretations in the parton model are discussed.

Anselmino, M; Kalinowski, Jan

1994-01-01

222

Nucleon structure from RBC/UKQCD 2+1 flavor DWF dynamical ensembles at a nearly physical pion mass  

CERN Document Server

We report the status of nucleon structure calculations on the (2+1)-flavor dynamical domain-wall fermions ensembles with pion masses as low as 180 and 250 MeV on a lattice with about 4.6 fm spatial extent. A combination of the Iwasaki+dislocation- suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while keeping the residual mass small. Nucleon source Gaussian smearing has been optimized. Preliminary nucleon mass estimates are 0.98 and 1.05 GeV.

Ohta, Shigemi

2010-01-01

223

Nucleon structure from mixed action calculations using 2+1 flavors of asqtad sea and domain wall valence fermions  

International Nuclear Information System (INIS)

We present high statistics results for the structure of the nucleon from a mixed-action calculation using 2+1 flavors of asqtad sea and domain-wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.

224

Nucleon-nucleon momentum correlation function as a probe of the density distribution of valence neutron in neutron-rich nucleus  

CERN Document Server

Proton-neutron, neutron-neutron and proton-proton momentum correlation functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for $^{15}$C and other C isotopes induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum molecular dynamics (IDQMD) model complemented by the CRAB (correlation after burner) computation code. $^{15}$C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron shell nucleus $^{14}$C. In order to study density dependence of correlation function by removing the isospin effect, the initialized $^{15}$C projectiles are sampled from two kinds of density distribution from RMF model, in which the valence neutron of $^{15}$C is populated on both 1$d$5/2 and 2$s$1/2 states, respectively. The results show that the density distributions of valence neutron significantly influence nucleon-nucleon momentum correlation function at large impact parameter and high incident energy. T...

Cao, X G; Ma, Y G; Fang, D Q; Zhang, G Q; Guo, W; Chen, J G; Wang, J S; 10.1103/PhysRevC.86.044620

2012-01-01

225

Global Study of Nuclear Structure Functions  

CERN Document Server

We present the results of a global study of unpolarized nuclear structure functions for a wide kinematical region of $x$ and $Q^2$. We develop a model which takes into account a number of different nuclear corrections from nuclear shadowing, Fermi motion and nuclear binding, nuclear pions and off-shell effect in bound nucleon structure functions. Within this approach we perform a statistical analysis of available data on the ratio of the nuclear structure functions $F_2$ for different nuclei in the range from Deuterium to ${}^{207}$Pb. We treat the off-shell effect in the bound nucleon structure functions and, partially, nuclear shadowing effect phenomenologically. To this end we introduce a few general (i.e. same for all nuclei) parameters which are extracted from nuclear data. As a result we obtain an excellent overall agreement between our calculations and data in the entire kinematical region of $x$ and $Q^2$. We discuss a number of applications of our model which include the calculation of the deuteron s...

Kulagin, S A

2006-01-01

226

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

CERN Document Server

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

227

Nucleon structure from 2+1-flavor dynamical DWF lattice QCD at nearly physical pion mass  

CERN Document Server

Domain-wall fermions (DWF) is a lattice discretization for Dirac fields that preserves continuum-like chiral and flavor symmetries that are essential in hadron physics. RIKEN-BNL-Columbia (RBC) and UKQCD Collaborations have been generating sets of realistic 2+1-flavor dynamical lattice quantum chromodynamics (QCD) numerical ensembles with DWF quarks with strange mass set almost exactly at its physical value via reweighing and degenerate up and down mass set as light as practical. In this report the current status of the nucleon-structure calculations using these ensembles are summarized.

Lin, Meifeng

2011-01-01

228

Nucleon structure from 2+1f dynamical DWF lattice QCD at nearly physical pion mass  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Current status of nucleon structure calculations with joint RBC and UKQCD 2+1-flavor dynamical domain-wall fermions (DWF) lattice QCD is reported: Two ensembles with pion mass of about (m_\\pi=170) MeV and 250 MeV are used. The lattice cutoff is set at about 1.4 GeV, allowing a large spatial volume of about (L=4.6) fm across while maintaining a sufficiently small residual breaking of chiral symmetry with the dislocation-suppressing-determinant-ratio (DSDR) gauge action. We ca...

Ohta, Shigemi; Collaboration, For The Rbc; Collaboration, For The Ukqcd

2011-01-01

229

Isospin dependence of nucleon Correlations in ground state nuclei  

CERN Document Server

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

230

Chromosome structure and function  

Energy Technology Data Exchange (ETDEWEB)

This book presents topics in chromosome structure and function. Topics covered include: the structure of interphase chromatin; chromatin structure, gene expression and differentiation; organization of mitotic chromosomes; organization of meiotic chromosomes and synaptonimal complexes; the lampbrush chromsome of animal oocytes; dosage compensation in mammals: x chromosome inactivation; and polytene chromosomes.

Risley, M.S.

1986-01-01

231

Lepton nucleon scattering  

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

232

Lepton nucleon scattering  

Energy Technology Data Exchange (ETDEWEB)

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 Q/sup 2/. In conclusion, all the tests of QCD are tabulated, and the results are evaluated. 32 references, 33 figures, 4 tables. (RWR)

Atwood, W.B.

1979-11-01

233

pp Elastic Scattering at LHC in a Nucleon-Structure Model  

CERN Document Server

We predict pp elastic differential cross sections at LHC at c.m. energy 14 TeV and momentum transfer range |t| = 0 - 10 GeV*2 in a nucleon-structure model. In this model, the nucleon has an outer cloud of quark-antiquark condensed ground state, an inner shell of topological baryonic charge (r ~ 0.44F) probed by the vector meson omega, and a central quark-bag (r ~ 0.2F) containing valence quarks. We also predict elastic differential cross section in the Coulomb-hadronic interference region. Large |t| elastic scattering in this model arises from valence quark-quark scattering, which is taken to be due to the hard-pomeron (BFKL pomeron with next to leading order corrections). We present results of taking into account multiple hard-pomeron exchanges, i.e. unitarity corrections. Finally, we compare our prediction of pp elastic differential cross section at LHC with the predictions of various other models. Precise measurement of pp elastic differential cross section at LHC by the TOTEM group in the |t| region 0 - 5...

Islam, M M; Luddy, R J

2007-01-01

234

Parity doubling structure of nucleon at nonzero density in the holographic mean field theory  

Science.gov (United States)

We develop the holographic mean field 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 nonzero 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 calculate the equation of state between the baryon number density and its corresponding chemical potential. Then, comparing the predicted equation of state with the one obtained in a Walecka type model, we extract the density dependence of the effective nucleon mass. The result shows that the effective mass decreases with increasing density, and that the rate of decreasing is more rapid for a larger percentage of the mass from the chiral symmetry breaking.

He, Bing-Ran; Harada, Masayasu

2013-11-01

235

Purely Functional Structured Programming  

CERN Document Server

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

236

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

237

Nucleon structure functions from measurements of inelastic neutrinoand antineutrino interactions  

International Nuclear Information System (INIS)

This paper presents the final results on charged-current neutrino and antineutrino interactions with nuclei from experiment E-310 at Fermi National Accelerator Laboratory. The data sample, consisting of 21 578 neutrino-induced and 7358 antineutrino-induced events within the fiducial region in the energy range 202 are presented. The emphasis throughout has been to understand the effects on the final results of uncertainties in the systematic corrections required by the data. Comparisons with the results of other neutrino experiments are made

238

Structure function monitor  

Science.gov (United States)

Methods and apparatus for a structure function monitor provide for generation of parameters characterizing a refractive medium. In an embodiment, a structure function monitor acquires images of a pupil plane and an image plane and, from these images, retrieves the phase over an aperture, unwraps the retrieved phase, and analyzes the unwrapped retrieved phase. In an embodiment, analysis yields atmospheric parameters measured at spatial scales from zero to the diameter of a telescope used to collect light from a source.

McGraw, John T. (Placitas, NM); Zimmer, Peter C. (Albuquerque, NM); Ackermann, Mark R. (Albuquerque, NM)

2012-01-24

239

Purely Functional Structured Programming  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Obua, Steven

2010-01-01

240

Gauge invariance, Lorentz covariance and canonical quantization in nucleon structure studies  

CERN Document Server

There are different operators of quark and gluon momenta, orbital angular momenta, and gluon spin in the nucleon structure study. The precise meaning of these operators are studied based on gauge invariance, Lorentz covariance and canonical quantization rule. The advantage and disadvantage of different definitions are analyzed. A gauge invariant canonical decomposition of the total momentum and angular momentum into quark and gluon parts is suggested based on the decomposition of the gauge potential into gauge invariant (covariant) physical part and gauge dependent pure gauge part. Challenges to this proposal are answered. \\keywords{Physical and pure gauge potentials; Gauge invariant canonical quark and gluon momenta, orbital angular momenta and spins; Homogeneous and non-homogeneous Lorentz transformations; Gauge invariant decomposition and gauge invariant extension; Classical and quantum measurements.

Wang, Fan; Sun, W M; Zhang, P M; Wong, C W

2014-01-01

 
 
 
 
241

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

CERN Document Server

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

242

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

CERN Document Server

We present new, high-Q^2 measurements of inclusive electron scattering from high-momentum nucleons in nuclei. This yields an improved extraction 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 extend to the kinematic regime where three-nucleon correlations are expected to dominate and we observe significantly greater strength in this region than previous measurements.

Fomin, N; Asaturyan, R; Benmokhtar, F; Boeglin, W; Bosted, P; Bruell, A; Bukhari, M H S; Chudakov, E; Clasie, B; Connell, S H; Dalton, M M; Daniel, A; Day, D B; Dutta, D; Ent, R; Fassi, L El; 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

2011-01-01

243

Do we expect light flavor sea-quark asymmetry also for the spin-dependent distribution functions of the nucleon?  

CERN Document Server

After taking account of the scale dependence by means of the standard DGLAP evolution equation, the theoretical predictions of the chiral quark soliton model for the unpolarized and longitudinally polarized structure functions of the nucleon are compared with the recent high energy data. The theory is shown to explain all the qualitative features of the experiments, including the NMC data for $F_2^p (x) - F_2^n (x)$, $F_2^n (x) / F_2^p (x)$, the Hermes and NuSea data for $\\bar{d}(x) - \\bar{u}(x)$, the EMC and SMC data for $g_1^p(x)$, $g_1^n(x)$ and $g_1^d(x)$. Among others, flavor asymmetry of the longitudinally polarized sea-quark distributions is a remarkable prediction of this model, i.e., it predicts that $\\Delta \\bar{d}(x) - \\Delta \\bar{u}(x) = C x^{\\alpha} [ (and $\\alpha \\simeq 0.12$) in qualitative consistency with the recent semi-phenomenological analysis by Morii and Yamanishi.

Wakamatsu, M

2000-01-01

244

Nucleon structure from RBC/UKQCD 2+1 flavor DWF dynamical ensembles at a nearly physical pion mass  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report the status of nucleon structure calculations on the (2+1)-flavor dynamical domain-wall fermions ensembles with pion masses as low as 180 and 250 MeV on a lattice with about 4.6 fm spatial extent. A combination of the Iwasaki+dislocation- suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while keeping the residual mass small. Nucleon source Gaussian smearing has been optimized....

Ohta, Shigemi; Rbc, For The; Collaborations, Ukqcd

2010-01-01

245

Chromatin Structure and Function  

CERN Document Server

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

246

Photon structure function revisited  

CERN Document Server

The flux of papers from electron positron colliders containing data on the photon structure function ended naturally around 2005. It is thus timely to review the theoretical basis and confront the predictions with a summary of the experimental results. The discussion will focus on the increase of the structure function with x (for x away from the boundaries) and its rise with log Q**2, both characteristics beeing dramatically different from hadronic structure functions. Comparing the data with a specific QCD prediction a new determination of the QCD coupling coupling constant is presented. The agreement of the experimental observations with the theoretical calculations of the real and virtual photon structure is a striking success of QCD.

Berger, Ch

2014-01-01

247

Treatment of Two Nucleons in Three Dimensions  

CERN Document Server

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

248

Deep-inelastic structure functions in a covariant spectator model  

International Nuclear Information System (INIS)

Deep-inelastic structure functions are studied within a covariant scalar diquark spectator model of the nucleon. Treating the target as a two-body bound state of a quark and a scalar diquark, the Bethe-Salpeter equation (BSE) for the bound state vertex function is solved in the ladder approximation. The valence quark distribution is discussed in terms of the solutions of the BSE. copyright 1997 The American Physical Society

249

Deep Inelastic Structure Functions in a Covariant Spectator Model  

CERN Document Server

Deep-inelastic structure functions are studied within a covariant scalar diquark spectator model of the nucleon. Treating the target as a two-body bound state of a quark and a scalar diquark, the Bethe-Salpeter equation (BSE) for the bound state vertex function is solved in the ladder approximation. The valence quark distribution is discussed in terms of the solutions of the BSE.

Kusaka, K; Thomas, A W; Williams, A G

1997-01-01

250

Nuclear and hadronic structure functions at an advanced hadron facility  

International Nuclear Information System (INIS)

Deep inelastic scattering of charged leptons from nuclei shows the observed structure function per nucleon to be modified in the nuclear medium. The first experimental report of such an effect was made several years ago by the European Muon Collaboration (EMC); hence, the effect is popularly known as the EMC effect. Considerable time and effort have now gone into carrying out accurate, relative structure-function measurements. A rather consistent picture of nuclear effects has emerged that appears to be quite systematic as a function of the nucleon number A, as shown in this paper. Unfortunately, the information obtained from deep-inelastic charged-lepton scattering is insensitive to quark flavor as the contribution of each quark flavor is weighted by the square of its electric charge

251

Structure function of off-mass-shell pions and the calculation of the Sullivan process  

International Nuclear Information System (INIS)

We construct a model for the pion (valence) structure function that fits the experimental data obtained in the study of the Drell-Yan process. The model may also be used to calculate the structure function of off-mass-shell pions. We apply our model in the study of deep-inelastic scattering from off-mass-shell pions found in the nucleon and are thus able to resolve a problem encountered in the standard analysis of such processes. The usual analysis is made using the structure function of on-mass-shell pions and requires the use of a soft ?NN form factor that is inconsistent with standard nuclear physics phenomenology. The use of our off-mass-shell structure functions allows for a fit to the data for nonperturbative aspects of the nucleon ''sea'' with a pion-nucleon form factor of the standard form

252

Spin Structure Functions from Electron Scattering  

International Nuclear Information System (INIS)

The spin structure of the nucleon can play a key testing ground for Quantum Chromo-Dynamics (QCD) at wide kinematic ranges from smaller to large four momentum transfer Q2. The pioneering experiments have confirmed several QCD sum rules at high Q2 where a perturbative picture holds. For a full understanding of QCD at various scales, various measurements were made at intermediate and small Q2 region and their interpretation would be a challenging task due to the non-perturbative nature. Jefferson Lab has been one of the major experimental facilities for the spin structure with its polarized electron beams and various polarized targets. A few QCD sum rules have been compared with the measured spin structure functions g1(x, Q2) and g2(x, Q2) at low Q2 and surprising results have been obtained for the spin polarizabilities, ?0 and (delta)LT . As for the proton spin structure functions, the lack of data for g2(x,Q2) structure functions has been complemented with a new experiment at Jefferson Lab, SANE. The results from SANE will provide a better picture of the proton spin structure at a wide kinematic range in x and Q2.

253

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

254

Moments of generalized parton distribution functions and the nucleon spin contents  

CERN Document Server

It is shown that, based only on two empirically known facts besides two reasonable theoretical postulates, we are inevitably led to a conclusion that the quark orbital angular momentum carries nearly half of the total nucleon spin. We also perform a model analysis to find that the quark spin fraction $\\Delta \\Sigma$ is extremely sensitive to the pion mass, which may resolve the discrepancy between the observation and the prediction of the recent lattice QCD simulation carried out in the heavy pion region.

Wakamatsu, M

2005-01-01

255

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

CERN Document Server

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

256

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.)

257

Isospin dependence of nucleon correlations in ground-state nuclei  

Science.gov (United States)

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.

Charity, R. J.; Dickhoff, W. H.; Sobotka, L. G.; Waldecker, S. J.

2014-02-01

258

Probing the Effective Nucleon-Nucleon Interaction at Band Termination  

Science.gov (United States)

Low-energy nuclear structure is not sensitive enough to resolve the fine details of the nucleon-nucleon (NN) interaction. The insensitivity of the low-energy (infrared) physics to the details of the short-range strong interaction allows for a consistent, free of high-energy (ultraviolet) divergences, formulation of a local theory at the level of the local energy density functional (LEDF) including on the same footing, particle-hole and particle-particle channels. A major difficulty is related to the parameterization of the nuclear LEDF and its density dependence. It is argued that the structural simplicity of terminating or isomeric states offers an invaluable source of information that can be used for fine-tuning of the NN interaction in general and the nuclear LEDF parameters in particular. Practical applications of terminating states at the level of LEDF and nuclear shell-model are discussed.

Satu?a, W.

259

Experimental studies of the quark-gluon structure of nucleons and nuclei and of pion- and proton-nucleus interactions. Progress report, April 1, 1994--March 31, 1997  

Energy Technology Data Exchange (ETDEWEB)

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.

NONE

1996-10-01

260

Experimental studies of the quark-gluon structure of nucleons and nuclei and of pion- and proton-nucleus interactions. Progress report, April 1, 1994--March 31, 1997  

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

 
 
 
 
261

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

262

Chiral perturbation theory with nucleons  

Energy Technology Data Exchange (ETDEWEB)

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, {pi}N scattering and the {sigma}-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.

Meissner, U.G.

1991-09-01

263

Projectile structure effects in multi-nucleon and cluster transfers in 16,18O+164Dy, 208Pb reactions  

Science.gov (United States)

The yield of projectile like fragments (PLFs) has been measured in the reactions of 16,18O with 164Dy and 208Pb targets at energies above the Coulomb barrier. The experimental data are analyzed to ascertain the role of projectile structure on the multi-nucleon and cluster correlations in transfer reactions. The variation of transfer probability with the number of nucleons transferred from the projectile to the target nucleus at the grazing angle has been investigated for both the systems. In the case of 18O induced reactions the cross sections of the two neutron (2n) stripping as well as the 2n- correlated cluster transfer are strongly enhanced as compared to the 16O induced reactions. These results have been discussed on the basis of the possible influence of the valence di-neutrons in the 18O nucleus on multi-particle transfer reactions.

Biswas, D. C.; Roy, Pratap; Gupta, Y. K.; Joshi, B. N.; Nayak, B. K.; Danu, L. S.; John, B. V.; Vind, R. P.; Deshmukh, N.; Mukherjee, S.; Jain, A. K.; Choudhury, R. K.

2012-09-01

264

Excitation function of nucleon and pion elliptic flow in relativistic heavy-ion collisions  

CERN Document Server

Within a relativistic transport (ART) model for heavy-ion collisions, we show that the recently observed characteristic change from out-of-plane to in-plane elliptic flow of protons in mid-central Au+Au collisions as the incident energy increases is consistent with the calculated results using a stiff nuclear equation of state (K=380 MeV). We have also studied the elliptic flow of pions and the transverse momentum dependence of both the nucleon and pion elliptic flow in order to gain further insight about the collision dynamics.

Li, B A; Sustich, A T; Zhang, B; Li, Bao-An; Sustich, Andrew T.; Zhang, Bin

1999-01-01

265

Partonic structure of the Nucleon in QCD and Nuclear Physics: new developments from old ideas  

CERN Document Server

The nucleon is an ideal laboratory to solve QCD in the nonperturbative regime. There are several experimental observations that still lack a rigorous interpretation; they involve the nucleon as a (polarized) target as well as a beam (in collisions and Drell-Yan processes). These data look like big azimuthal and spin asymmetries, related to the transverse polarization and momentum of the nucleon and/or the final detected particles. They suggest internal reaction mechanisms that are suppressed in collinear perturbative QCD but that are "natural" in Nuclear Physics: quark helicity flips, residual final state interactions, etc.. In my talk, I will give a brief survey of the main results and I will flash the most recent developments and measurements.

Radici, M

2005-01-01

266

Measurement of the Strange Quark Contribution to Nucleon Structure Through Parity-Violating Electron Scattering  

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

267

Tests of Duality in the Spin-Structure Function g_1  

Energy Technology Data Exchange (ETDEWEB)

Although quark-hadron duality is well established for the spin-independent structure function, F{sub 2}{sup p}, hardly any information is available on the low Q{sup 2} scaling behavior of spin-structure functions. Recent experiments at Jefferson Lab measured the spin-structure function g1 in the nucleon resonance region for variety of targets. Global and local duality was observed for Q{sup 2} values above {approx} 2 (GeV/c){sup 2}.

Wolfgang Korsch

2006-11-01

268

Three-nucleon transfer reactions and cluster structure in the A = 15 to A = 19 nuclei  

International Nuclear Information System (INIS)

The (6Li,t) and (6Li,3He) reactions were studied on targets of 12C, 13C, 14N, 15N, and 16O at E/sub Li/ approx. = 44 MeV and theta/sub lab/ approx. = 150. A preferential population of final states was exhibited in spectra for the A = 15 to A = 19 nuclei. The strong forward peaking of angular distributions in the 13C(6Li,t)16O and 13C(6Li,3He)16N reactions can be reproduced by DWBA calculations but not by the Hauser-Feshbach model. Such indications of a primarily direct mechanism at forward angles suggest use of these three-nucleon-transfer reactions to identify candidates for 3p-nh states. A comparison with other multinucleon transfer data, e.g., those from (7Li,?) and (7Li,t) reactions on 13C and 15N targets, further tests dominant particle-hole configurations. The relationship between (6Li,t) and (6Li,3He) spectra reveals analog states, notably T = 1, T/sub z/ = 0 levels at high excitation in 16O. Nuclear theory is used to investigate the role of triton clustering in such structure. The 2N + L = 6 band predicted by a folded-potential model of 18O = 15N + t shows an underlying correspondence to the experimental levels in triton-transfer data. Triton spectroscopic factors calculated froiton spectroscopic factors calculated from the SU(3) shell model further suggest the broad influence of clustering phenomena in this mass region. Experimental evidence of systematic behavior in the triton binding energies of proposed p/sup -n/(sd)3 configurations was found

269

What can be learned about meson nucleon interactions and nuclear structure from K+ total cross sections  

International Nuclear Information System (INIS)

K+ total cross sections on deuterium, 6Li, 12C, 28Si and 40Ca have been measured at four momenta in the range of 480--714 MeV/c. This study has revealed important modifications of the free-space K+-nucleon interaction when the nucleon is embedded in a nucleus. Some of the suggested modifications include unconventional nuclear medium effects such as partial quark deconfinement, mass rescaling of nuclear pionic fields or pion excess in nuclei and meson exchange currents

270

Nucleon matrix elements with domain wall fermions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the status of our calculation of the first few moments of the nucleon structure functions. Our calculations are done using domain wall fermions in the quenched approximation with the DBW2 gauge action at 1.3GeV inverse lattice spacing.

Orginos, Konstantinos; Collaboration, Rbc

2002-01-01

271

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.)

272

Unquenched simulations of four-nucleon interactions  

International Nuclear Information System (INIS)

Exploratory simulations of four-nucleon interactions are performed taking into account the dynamical effects of internal nucleon loops. The four-nucleon interactions in the isoscalar and isovector channels are described by Yukawa interactions with auxiliary scalar fields. The nucleon mass and the average field lengths of the scalar fields are determined as a function of nucleon hopping parameter and Yukawa coupling strengths. There are no problems with ''exceptional configurations'' at strong couplings which make quenched simulations unreliable.

273

Method of determining the gluon structure function from the cross section for the inelastic photoproduction of J/psi  

International Nuclear Information System (INIS)

We present a method of determining the gluon structure function of the nucleon and nuclear effects on the function from the total cross section for the inelastic photoproduction of J/psi. The method is very useful for learning more about the behavior of the gluon structure function in the small-x region

274

Nucleon-nucleon wave function with short-range nodes and deuteron photodisintegration $d\\gamma\\to np$ at 2 GeV photon energy  

CERN Document Server

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

275

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

276

On the $Q^2$ dependence of nuclear structure functions  

CERN Document Server

The recent high statistics NMC data on the Tin to Carbon structure function ratio seems to indicate, for the first time, a significant $Q^2$ dependence, especially at small values of Bjorken $x$, $x 1 GeV^2$. Pure leading twist, perturbative QCD--based predictions, which are consistent with the free nucleon data, yield a fairly flat ratio with little or no $Q^2$ dependence. In view of this seeming contradiction, we re-examine the applicability of such a perturbative model to nuclear structure functions in such a kinematical regime. We find that the model is consistent with all data, within experimental errors, without any need for introducing additional higher twist contributions. The model correctly reproduces the $Q^2$ dependence of the Carbon structure function as well. We also critically examine the $Q^2$ dependence of the corresponding spin dependent structure functions.

Indumathi, D

1996-01-01

277

Partially-Quenched Nucleon-Nucleon Scattering  

CERN Document Server

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

278

Single-nucleon experiments  

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

279

Spin and angular momentum in the nucleon  

Energy Technology Data Exchange (ETDEWEB)

Using the covariant spectator theory (CST), we present the results of a valence quark-diquark model calculation of the nucleon structure function f(x) measured in unpolarized deep inelastic scattering (DIS), and the structure functions g1(x) and g2(x) measured in DIS using polarized beams and targets. Parameters of the wave functions are adjusted to fit all the data. The fit fixes both the shape of the wave functions and the relative strength of each component. Two solutions are found that fit f(x) and g1(x), but only one of these gives a good description of g2(x). This fit requires the nucleon CST wave functions contain a large D-wave component (about 35%) and a small P-wave component (about 0.6%). The significance of these results is discussed.

Franz Gross, Gilberto Ramalho, Teresa Pena

2012-05-01

280

External Momentum, Volume Effects, and the Nucleon Magnetic Moment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We analyze the determination of volume effects for correlation functions that depend on an external momentum. As a specific example, we consider finite volume nucleon current correlators, and focus on the nucleon magnetic moment. Because the multipole decomposition relies on SO(3) rotational invariance, the structure of such finite volume corrections is unrelated to infinite volume multipole form factors. One can deduce volume corrections to the magnetic moment only when a z...

Tiburzi, B. C.

2007-01-01

 
 
 
 
281

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

Directory of Open Access Journals (Sweden)

Full Text Available We summarize our recent work in which we develope the holographic mean field approach to study the dense baryonic matter in a bottom-up holographic QCD model including baryons and scalar mesons in addition to vector mesons. We first show that, at zero density, the rate of the chiral invariant mass of nucleon is controlled by the ratio of the infrared boundary values of two baryon fields included in the model. Then, at non-zero density, we find that the chiral condensate decreases with the increasing density indicating the partial restoration of the chiral symmetry. Our result shows that the more amount of the proton mass comes from the chiral symmetry breaking, the faster the effective nucleon mass decrease with density.

He Bing-Ran

2014-06-01

282

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

Science.gov (United States)

We summarize our recent work in which we develope the holographic mean field approach to study the dense baryonic matter in a bottom-up holographic QCD model including baryons and scalar mesons in addition to vector mesons. We first show that, at zero density, the rate of the chiral invariant mass of nucleon is controlled by the ratio of the infrared boundary values of two baryon fields included in the model. Then, at non-zero density, we find that the chiral condensate decreases with the increasing density indicating the partial restoration of the chiral symmetry. Our result shows that the more amount of the proton mass comes from the chiral symmetry breaking, the faster the effective nucleon mass decrease with density.

He, Bing-Ran; Harada, Masayasu

2014-06-01

283

Neutron yields from structural metals during bombardment by heavy ions with 2.5 MeV/nucleon energy  

Science.gov (United States)

Neutron yields during irradiation of structural metals and polymer film by argon, krypton, and xenon ions with 2.4 and 2.5 MeV/nucleon energies are measured on the CYTRACK and DC-110 cyclotrons. The angular distributions of neutrons from the target are measured. The LISE++ is used for extrapolating the data obtained to other ions, their energy, and to other targets. The program was tested on experimental data found in the literature. As a result of comparison, it is established that the calculation results coincide with the experimental data within a coefficient of two.

Gikal, B. N.; Mironov, V. I.; Teterev, Yu. G.; Shchegolev, V. Yu.

2014-03-01

284

Nucleon structure with pion mass down to 149 MeV  

CERN Document Server

We present isovector nucleon observables: the axial, tensor, and scalar charges and the Dirac radius. Using the BMW clover-improved Wilson action and pion masses as low as 149 MeV, we achieve good control over chiral extrapolation to the physical point. Our analysis is done using three different source-sink separations in order to identify excited-state effects, and we make use of the summation method to reduce their size.

Green, Jeremy; Krieg, Stefan; Negele, John; Pochinsky, Andrew; Syritsyn, Sergey

2012-01-01

285

Nucleon distribution in the triton  

International Nuclear Information System (INIS)

The triton bound state energy and wave function are derived from the pole of the solution of the inhomogeneous integral equation for the Faddeev component. In the present method, we can avoid a spurious or an unphysical solution. The Argonne v14 and the Paris potentials are adopted as a realistic two-nucleon local interaction. The three-nucleon force is not taken into account in the calculation. The nucleon distribution in the triton is investigated. (author)

286

Microscopic investigation of the structure characteristics and wave functions of the five-body hypernucleus He?5  

Directory of Open Access Journals (Sweden)

Full Text Available The Parentage Scheme of Summarization to the N-body symmetrized basis construction [1], necessary for the description of the structural characteristics and decay reactions of the hypernuclear and nuclear systems with arbitrary amount of particles, is applied to the solution of five-body problem in hypernuclear physics. Hypernucleus He?5 as a system of four nucleons and one hyperon is investigated by the use of the Hyperspherical Function Method in momentum space. The dependence of the structure characteristics and wave functions on the types of nucleon-nucleon and hyperon-nucleon interaction potentials is studied. Mean square ? ? H3 and ?? ? distances and the binding energies for the He4 and He?5 are obtained.

Margolin Lia Leon

2014-03-01

287

Microscopic investigation of the structure characteristics and wave functions of the five-body hypernucleus He?5  

Science.gov (United States)

The Parentage Scheme of Summarization to the N-body symmetrized basis construction [1], necessary for the description of the structural characteristics and decay reactions of the hypernuclear and nuclear systems with arbitrary amount of particles, is applied to the solution of five-body problem in hypernuclear physics. Hypernucleus He?5 as a system of four nucleons and one hyperon is investigated by the use of the Hyperspherical Function Method in momentum space. The dependence of the structure characteristics and wave functions on the types of nucleon-nucleon and hyperon-nucleon interaction potentials is studied. Mean square ? - H3 and ?- ? distances and the binding energies for the He4 and He?5 are obtained.

Margolin, Lia Leon

2014-03-01

288

Nucleon decay  

International Nuclear Information System (INIS)

The significance of the nucleon decay in grand unified theories is described. Experimental methods and large existing apparatus are briefly described. Last limits are given for separate decay modes, and possible developments of experiments are discussed. 5 refs

289

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

CERN Document Server

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

290

Flavor asymmetry of the polarized nucleon sea  

CERN Document Server

We discuss the flavor asymmetry of polarized light antiquarks in the nucleon, $\\Delta\\bar{u}-\\Delta\\bar{d}$. We present a determination of this quantity based on two global QCD analyses of experimental data, DSSV08 and NNPDFpol1.1, in which sea-quark parton distribution functions are determined respectively either from semi-inclusive deep-inelastic scattering or W-boson production data. The latter have become available only very recently, and their effect on the polarized flavor asymmetry is presented here for the first time. We find that the flavor asymmetry of polarized antiquarks in the nucleon is definitely positive, and has almost the same absolute size as its unpolarized counterpart. We compare this result with various theoretical models of the nucleon structure in order to test their validity. We show that some of them are clearly disfavored.

Nocera, Emanuele Roberto

2014-01-01

291

Optimized Chiral Nucleon-Nucleon Interaction at Next-to-Next-to-Leading Order  

Energy Technology Data Exchange (ETDEWEB)

We optimize the nucleon-nucleon interaction from chiral effective field theory at next-to-next-toleading order (NNLO). The resulting new chiral force NNLOopt yields 2 1 per degree of freedom for laboratory energies below approximately 125 MeV. In the A 3, 4 nucleon systems, the contributions of three-nucleon forces are smaller than for previous parametrizations of chiral interactions. We use NNLOopt to study properties of key nuclei and neutron matter, and we demonstrate that many aspects of nuclear structure can be understood in terms of this nucleon-nucleon interaction, without explicitly invoking three-nucleon forces.

Nazarewicz, Witold [ORNL; Hagen, Gaute [ORNL; Papenbrock, T. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Sarich, J. [Argonne National Laboratory (ANL); Wild, S. [Argonne National Laboratory (ANL); Baardsen, G. [University of Oslo, Norway; Hjorth-Jensen, Morten [ORNL; Jansen, G. R. [UTK/ORNL; Machleidt, R. [University of Idaho

2013-01-01

292

Can one directly test the scalar-vector Lorentz structure of the nucleon- and antinucleon-nucleus potential?  

International Nuclear Information System (INIS)

Quantum hadrodynamics in mean-field approximation describes the effective nucleon-nucleus potential (about -50 MeV deep) as resulting from a strong repulsive vector (about 400 MeV) and a strong attractive scalar (about -450 MeV) contribution. This scalar-vector Lorentz structure implies a significant lowering of the threshold for pp-bar photoproduction on a nucleus by about 850 MeV as compared with the free case since charge conjugation reverses the sign of the vector potential contribution in the equation of motion for the p-bar states. We discuss the possibility of measurable signatures of the scalar-vector structure of the nucleon-nucleus potential for the pp-bar photoproduction. The pp-bar photoproduction cross section is calculated for the target nucleus 208Pb near threshold. We indicate the increased cross section for emission of charged pions as a consequence of the subsequent p-bar annihilation within the nucleus. The inclusive cross section for ?-induced pp-bar creation and the resulting increase of charged pion production are probably too small as compared with the expected background to be measurable. (author)

293

Gluon Virtuality and Heavy Sea Quark Contributions to the Spin-Dependent $g_{1}$ Structure Function  

CERN Document Server

We analyze the quark mass dependence of photon gluon fusion in polarized deep inelastic scattering for both the intrinsic and extrinsic gluon distributions of the nucleon. We calculate the effective number of flavors for each of the heavy and light quark photon gluon fusion contributions to the first moment of the spin-dependent structure function $g_1(x)$.

Bass, S; Schmidt, I; Bass, Steven; Brodsky, Stanley J.; Schmidt, Ivan

1999-01-01

294

Structure and Function  

CERN Document Server

Describes how the understanding of structure - property relationships may be used to interpret known compounds and how to design novel molecules and materials with the desired properties. This book covers the theoretical background, experimental techniques and applications of structure-property correlations

Comba, Peter

2010-01-01

295

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

296

The structure of functions  

CERN Document Server

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

297

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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)^3. Despite t...

Lin, Huey-wen; Ohta, Shigemi

2006-01-01

298

Polarized gluons in the nucleon  

CERN Document Server

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

299

Spatial Variation of Nuclear Structure Functions and Heavy Quark Production  

Science.gov (United States)

We explore how nuclear modifications to the free nucleon structure functions (also known as shadowing) affect heavy quark production in collisions at different impact parameters. We assume that the nuclear modifications arise from a density dependent effect such as gluon recombination and are thus proportional to the local density. We calculate the dependence of charm and bottom quark production on impact parameter and show that density dependent modifications can lead to significant reductions in the heavy quark production cross sections in central relative to peripheral interactions.

Emel'Yanov, V.; Khodinov, A.; Klein, S. R.; Vogt, R.

1998-08-01

300

Structure function results from ZEUS  

International Nuclear Information System (INIS)

This contribution presents recent ZEUS results on proton structure functions at HERA. The inclusive phi(1020)-meson cross section was measured, and it was used to determine the s-quark content of the proton. The structure function F2 was extracted using initial-state radiative events. Neutral and charged current cross sections were used to extract the structure function xF3 and measure the mass of the W boson, respectively. A NLO QCD fit to ZEUS data and fixed target cross sections was employed to determine the parton density functions of the quarks and of the gluon inside the proton

 
 
 
 
301

Proton structure functions at HERA  

Science.gov (United States)

The "proton structure" is a wide field. Discussed are predominantly the precision measurements of the proton structure functions at HERA and some of their implications for the LHC measurements. In addition, a discussion of what a proton structure function represents is provided. Finally, a connection to nuclear physics is attempted. This contribution is an updated reprint of a contribution to "Deep Inelastic Scattering 2012".1

Abt, Iris

2014-05-01

302

Nucleon - Nucleon Interactions at Short Distances  

CERN Document Server

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

303

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

304

A Simple Approach to Study the Isospin Effect in Mass Splitting of Three-Nucleon Systems by Using Hyperspherical Functions  

International Nuclear Information System (INIS)

In this work, the binding energy and wavefunctions of three-nucleon systems are obtained by using hyperspherical harmonic approach. We have used a mathematical modification method to obtain the eigenvalues and eigenfunctions of Schrödinger equation for three-nucleon systems in calculation. Next, we have used a simple approach to obtain the difference between binding energy of 3H and 3He where gives us mass splitting of three-nucleon systems. We have compared our results with the other works and experimental values. (nuclear physics)

305

Nucleons in nuclei, however  

International Nuclear Information System (INIS)

The topics presented at the 1989 Joliot-Curie Lectures are reported. Two main subjects were retained: a simplified description of the N-body motion of particles in the quasi-particle configuration; study of the dynamics of nuclear components which are not described by nucleons in their ground state. The following themes were presented: quasiparticles and the Green functions, relativistic aspects of the quasiparticle concept, the dimensions of nucleons in the nuclei and the EMC effect, quarks and gluons in the nuclei, the delta in the nuclei, the strangeness, quasiparticles far from the Fermi sea, diffusion of electrons, stellar evolution and nucleosynthesis

306

Fragmentation and nucleon structure in semi-inclusive deep-inelastic scattering at the HERMES experiment  

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.

307

Deformed nucleons and deltas  

International Nuclear Information System (INIS)

Some of the history behind the form of the wavefunctions of the nucleon and the delta in models of hadron structure is briefly reviewed. The possibility of D-state admixture and its magnitude is analyzed. Moreover the dynamical origin of such admixture and its observable consequences are investigated. Finally comments are given about some recent data analysis. 19 refs.; 1 table

308

Recent developments in nucleon spin structure with focus on h1L#perpendicular# and pretzelosity h1Tperpendicular  

International Nuclear Information System (INIS)

The leading twist transverse momentum dependent parton distribution functions h1L#perpendicular# and h1Tperpendicular, which is sometimes called ''pretzelosity,'' are studied. For h1L#perpendicular# we consider a ''Wandzura-Wilczek-type'' approximation, which follows from QCD equations of motion upon the neglect of pure twist-3 terms and allows to express it in terms of transversity. On the basis of available data from HERMES we test the practical usefulness of this approximation and discuss how it can be further tested by future CLAS and COMPASS data. We review the theoretical properties of pretzelosity and observe an interesting relation valid in a large class of relativistic models: The difference between helicity and transversity distributions, which is often said to be a 'measure of relativistic effects' in the nucleon, is nothing but the transverse moment of pretzelosity. We discuss preliminary deuteron target data from COMPASS on the single spin asymmetry (SSA) in semi-incl

309

Towards a fully self-consistent spectral function of the nucleon in nuclear matter  

CERN Document Server

We present a calculation of nuclear matter which goes beyond the usual quasi-particle approximation in that it includes part of the off-shell dependence of the self-energy in the self-consistent solution of the single-particle spectrum. The spectral function is separated in contributions for energies above and below the chemical potential. For holes we approximate the spectral function for energies below the chemical potential by a energies above the chemical potential. For particles a similar procedure is followed. The approximated spectral function is consistently used at all levels of the calculation. Results for a model calculation are presented, the main conclusion is that although several observables are affected by the inclusion of the continuum contributions the physical consistency of the model does not improve with the improved self-consistency of the solution method. This in contrast to expectations based on the crucial role of self-consistency in the proofs of conservation laws.

De Jong, F

1997-01-01

310

The nucleon source spectrum generating the muon component and expected coupling function for an inclined meson telescope  

International Nuclear Information System (INIS)

In the analysis of data from ground-based muon telescopes the nucleon spectrum in the upper atmosphere has to be known better than can be found from existing direct measurements. Therefore an indirect determination of this spectrum has been made. In a test of the reliability of the approach the author has been able to reproduce muon spectra within experimental limits in at least the 0.2-50 GeV/c interval and at 0-600 to the zenith direction, at different atmospheric depths and geomagnetic latitudes. A calculation of the muon pressure coefficient for a standard cube gave - 0.16% mb-1 for high latitudes. In order to get some information on the angular distribution of the nucleons the applicability of the Gross transformation has been reexamined. For that purpose a fundamental study of a three-dimensional cascade has also been made. In a very simplified model it is assumed that the nucleons are isotropically produced in the LS. A linear cascade does not reflect the nucleon transport from one direction to another. Thus an exponential law for the nucleons in the atmosphere will not be obtained. The nucleon spectrum is discussed mainly in terms of the attenuation mean free path Lsub(N): In order to meet the rather stringent condition imposed by the muon spectra as a whole it was necessary to put Lsub(N)=160 gcm-2 in the upper atmosphere. (Auth.)

311

Exploring Three Nucleon Forces in Lattice QCD  

CERN Document Server

We study the three nucleon force in Nf=2 dynamical clover fermion lattice QCD, utilizing the Nambu-Bethe-Salpeter wave function of the three nucleon system. Since parity-odd two nucleon potentials are not available in lattice QCD at this moment, we develop a new formulation to extract the genuine three nucleon force which requires only the information of parity-even two nucleon potentials. In order to handle the extremely expensive calculation cost, we consider a specific three-dimensional coordinate configuration for the three nucleons. We find that the linear setup is advantageous, where nucleons are aligned linearly with equal spacings. The lattice calculation is performed with 16^3 x 32 configurations at \\beta=1.95, m_\\pi=1.13 GeV generated by CP-PACS Collaboration, and the result of the three nucleon force in triton channel is presented.

Doi, Takumi

2011-01-01

312

On study of resonance cross section structure of nucleon and deuteron interactions with light nuclei at the range of moderately overlapping resonance  

International Nuclear Information System (INIS)

A new approach is developed for description of resonance cross section structure of nucleon and deuteron interactions with light nuclei at the range of moderately overlapping resonances. It is based on data of one-particle state energy and modelling of the resonance widths and energy shifts by random matrix method. A comparison is given for calculation results with an experiment

313

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

314

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

CERN Document Server

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

315

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

316

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.)

317

Nucleon wave functions from lattice gauge theories: Renormalisation of baryonic operators  

International Nuclear Information System (INIS)

We study the 3-quark operators which govern the short-distance and light-cone properties of the proton's wave function. In particular we obtain expressions for the matrix elements of these operators in a continuum renormalisation scheme in terms of those measured on a lattice. These matrix elements, which are not calculable in perturbative QCD, are required for the predictions of hard exclusive processes and in the calculation of the proton's lifetime in grand unified theories. (orig.)

318

Collisions of protons with light nuclei shed new light on nucleon structure  

CERN Document Server

The high rates of multi-parton interactions at the LHC can provide a unique opportunity to study the multi-parton structure of the hadron. To this purpose high energy collisions of protons with nuclei are particularly suitable. The rates of multi-parton interactions depend in fact both on the partonic multiplicities and on the distributions of partons in transverse space, which produce different effects on the cross section in pA collisions, as a function of the atomic mass number A. Differently with respect to the case of multi-parton interactions in pp collisions, the possibility of changing the atomic mass number provides thus an additional handle to distinguish the diverse contributions. Some relevant features of double parton interactions in pD collisions have been discussed in a previous paper. In the present paper we show how the effects of double and triple correlation terms of the multi-parton structure can be disentangled, by comparing the rates of multiple parton interactions in collisions of proto...

Treleani, Daniele

2012-01-01

319

EMS effect and QCD evolution of three-quark picture of a nucleon  

International Nuclear Information System (INIS)

EMC effect is investigated using QCD approach based on effect of nucleon swelling in nucleus and three-quark structure of nucleon. A model, taking account of exchange of color objects (valent quarks, gluons, quark-antiquark sea interactions) and resulting in increase of nuclear nucleon size in the range of Bjorken variable values 0.25?x?0.65, is briefly described. Comparison of experimental data for dependences of deuterium and iron structure functions (SF) (as well as their R ratios) on transferred momentum square and fixed values of x variable is carried out. The calculated values for SF (D) and SF (Fe) and available experimental data are compared. It is noted that the suggested approach permitted to trace the effects of nucleon swelling in nuclei and to show different character of valon distribution in nucleons and nuclei

320

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

 
 
 
 
321

Functional Insights from Structural Genomics  

Energy Technology Data Exchange (ETDEWEB)

Structural genomics efforts have produced structural information, either directly or by modeling, for thousands of proteins over the past few years. While many of these proteins have known functions, a large percentage of them have not been characterized at the functional level. The structural information has provided valuable functional insights on some of these proteins, through careful structural analyses, serendipity, and structure-guided functional screening. Some of the success stories based on structures solved at the Northeast Structural Genomics Consortium (NESG) are reported here. These include a novel methyl salicylate esterase with important role in plant innate immunity, a novel RNA methyltransferase (H. influenzae yggJ (HI0303)), a novel spermidine/spermine N-acetyltransferase (B. subtilis PaiA), a novel methyltransferase or AdoMet binding protein (A. fulgidus AF{_}0241), an ATP:cob(I)alamin adenosyltransferase (B. subtilis YvqK), a novel carboxysome pore (E. coli EutN), a proline racemase homolog with a disrupted active site (B. melitensis BME11586), an FMN-dependent enzyme (S. pneumoniae SP{_}1951), and a 12-stranded {beta}-barrel with a novel fold (V. parahaemolyticus VPA1032).

Forouhar,F.; Kuzin, A.; Seetharaman, J.; Lee, I.; Zhou, W.; Abashidze, M.; Chen, Y.; Montelione, G.; Tong, L.; et al

2007-01-01

322

Deuteron spin structure functions in the resonance and deep inelastic scattering regions  

Energy Technology Data Exchange (ETDEWEB)

We derive relations between spin-dependent nuclear and nucleon g1 and g2 structure functions within the nuclear impulse approximation, which are 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.A. Kulagin; W. Melnitchouk

2008-01-01

323

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

324

High energy nucleon incident optical potential by relativistic impulse approximation  

International Nuclear Information System (INIS)

The optical potentials by relativistic impulse approximation (RIA) are utilized for the high energy nucleon incidence. The nucleon-nucleon scattering amplitudes are derived from the phase shift and parametrized as a function of the incident nucleon energy. The optical potential by RIA reproduces the experimental data. (author)

325

Polarizabilities of nucleons  

International Nuclear Information System (INIS)

The polarizabilities of the proton were accurately measured using low energy Compton scattering. The results do not agree very well with predictions from dispersion relations and resonance sum models. In particular the magnetic polarizability appears to be unexpectedly small. The discrepancy can be explained phenomenologically using t-channel exchanges. A dynamical treatment is preferable. The O(4,2) group model for nucleons provides such an approach because it is based on a dynamical model of internal structure and gives the correct form factors and structure functions of the proton. In order to determine the polarizabilities in this model, it was necessary to develop a perturbation theory for infinite component wave equations. The small magnetic polarizability arises naturally in this theory due to a large, negative diamagnetic contribution. For relativistic systems, it is shown that the diamagnetic part of the polarizability is associated with virtual pair production of one of the composite particles of the system. Although this effect is small for atoms, it can be large for hadrons. A prediction is given for the neutron polarizabilities. The theory also applies for its relativistic hydrogen atom and a pion model

326

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

327

Hadron Structure Function in Flux Tube Model  

Science.gov (United States)

The quark distribution functions of the meson (q-bar{q} system) and the nucleon (both q-diquark system and symmetric Y shape system) are calculated using the yo-yo mode of the classical string model. The valence quark distributions of the proton are consistent with intermediate value of q-diquark and symmetric Y shape calculation. Using the Weizsäcker-Williams approximation, the gluon distribution function is obtained from the Poynting vector of the flux tube which has the same energy-momentum relation as the string.

Kokubo, A.; Maruyama, M.; Takagi, F.

328

The EMC effect and high momentum nucleons in nuclei  

International Nuclear Information System (INIS)

Recent developments in understanding the influence of the nucleus on deep-inelastic structure functions, the EMC effect, are reviewed. A new data base which expresses ratios of structure functions in terms of the Bjorken variable xA = AQ2/(2MA q0) is presented. Information about two-nucleon short-range correlations (SRC) from experiments is also discussed and the remarkable linear relation between SRC and the EMC effect is reviewed. A convolution model that relates the underlying source of the EMC effect to modification of either the mean-field nucleons or SRC nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data. (author)

329

Unquenched simulations of four-nucleon interactions  

Energy Technology Data Exchange (ETDEWEB)

Exploratory simulations of four-nucleon interactions are performed taking into account the dynamical effects of internal nucleon loops. The four-nucleon interactions in the isoscalar and isovector channels are described by Yukawa interactions with auxiliary scalar fields. The nucleon mass and the average field lengths of the scalar fields are determined as a function of nucleon hopping parameter and Yukawa coupling strengths. There are no problems with ''exceptional configurations'' at strong couplings which make quenched simulations unreliable.

Montvay, I.

2012-10-15

330

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

331

Hyperon-nucleon versus nucleon-nucleon interactions  

International Nuclear Information System (INIS)

The present status of our knowledge on the baryon-baryon interaction is reviewed. It is demonstrated that our understanding of nucleon-nucleon forces has substantially improved in the last decade, due to many promising advances in the theoretical description and, of course, due to the vast amount of data on nucleon-nucleon scattering. This survey is concluded with commenting on some present proposals for measuring YN scattering. (orig./HSI)

332

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

333

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.)

334

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

335

Theory of diffractive structure functions  

International Nuclear Information System (INIS)

We discuss the connection between the dipole approach and the DIS structure functions. Particular emphasis is given to DIS diffraction. We report on current work on the NLO photon impact factor. As an application of the dipole approach in DIS diffraction, we discuss the diffractive production of jets and of charm. (author)

336

Are there charmed quarks in the nucleon? (Leptoproduction test)  

CERN Document Server

A simple relation between structure functions for deep inelastic leptoproduction off any nuclear target is presented to test for charmed quarks in the nucleon. In the case of SU(3)*SU(3) current symmetry, a similar relation for isoscalar nuclear targets is obtained. Existing CERN neutrino data are not accurate enough to draw any definite conclusions. (20 refs).

Novoseller, D

1974-01-01

337

New results from deep inelastic muon-nucleon scattering  

International Nuclear Information System (INIS)

New results obtained by three distinct muon-nucleon scattering experiments are reviewed. They concern the F2 structure function measurements, the open and hidden charm production from multimuon events, and the evidence for forward jets and forward protons/antiprotons production from hadronic final states

338

Nucleon-nucleon momentum correlation function as a probe of the density distribution of valence neutron in neutron-rich nucleus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Proton-neutron, neutron-neutron and proton-proton momentum correlation functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for $^{15}$C and other C isotopes induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum molecular dynamics (IDQMD) model complemented by the CRAB (correlation after burner) computation code. $^{15}$C is a prime exotic nucleus candidate due to the weakly bound valence neutron...

Cao, X. G.; Cai, X. Z.; Ma, Y. G.; Fang, D. Q.; Zhang, G. Q.; Guo, W.; Chen, J. G.; Wang, J. S.

2012-01-01

339

Density-dependent nucleon-nucleon interaction from UIX three-nucleon force  

CERN Document Server

A density-dependent two-nucleon potential has been derived in the formalism of correlated basis function. The effects of 3-particle interactions has been included by integrating out the degrees of freedom of the third nucleon. The potential can be easily employed in nuclear matter calculations. It yields results in agreement with those obtained from the underlying three-body potential. The use of the density dependent potential allowed us to study the effects of three-nucleon interactions in symmetric nuclear matter within the Auxiliary Field Diffusion Monte Carlo (AFDMC) computational scheme.

Lovato, Alessandro; Fantoni, Stefano; Illarionov, Alexey Yu; Schmidt, Kevin E; 10.1088/1742-6596/336/1/012016

2012-01-01

340

Nucleon-alpha potentials  

International Nuclear Information System (INIS)

The nucleon-alpha potential is calculated using a microscopic model with antisymmetrization effects included from Brink and Boeker, Soper and Serber nucleon-nucleon interactions. The energy dependence of the potentials is also derived

 
 
 
 
341

The Two-Nucleon System in Three Dimensions  

CERN Document Server

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

342

Proton structure functions at HERA  

International Nuclear Information System (INIS)

The electron-proton collider HERA, like an electron-mycroscope, explores the structure of the proton down to 10-16 cm and up to the situation of very high parton densities. The proton energy was upgraded from 820 to 920 GeV in the Fall of '98 and the luminosity has also substantially improved, with another factor of 3 upgrade expected to follow this year. Inclusive proton structure functions have been studied with incident e+ and e- of 27 GeV in the neutral (NC) and charged (CC) current interactions as functions of the squared four-momentum transfer, Q2, and of the fractional proton momentum carried by partons, x. The structure function F2, as well as the ?-Z0 interference term xF3, have been measured in a range of Q2 and 1/x that extends by orders of magnitude that reached by fixed target experiments. The DGLAP evolution equations [1] allow for a perturbative NLO QCD fit of the measured non-perturbative structure functions in the available kinematic range: ?S and the gluon density at low x are fitted at the same time with good precision. The longitudinal structure function, FL, can be determined within the DGLAP formalism. With CC, the electroweak unification has been tested; at high x, a first flavor decomposition of the light quarks is achieved. The contribution to F2 of the charm quark has been measured and results to be relevant. Bounds on the radius of quarks and on compositeness are derived from the data at the highest Q2, 1002?40,000 GeV2

343

Proton structure functions at HERA  

Science.gov (United States)

The electron-proton collider HERA, like an electron-mycroscope, explores the structure of the proton down to 10-16 cm and up to the situation of very high parton densities. The proton energy was upgraded from 820 to 920 GeV in the Fall of '98 and the luminosity has also substantially improved, with another factor of 3 upgrade expected to follow this year. Inclusive proton structure functions have been studied with incident e+ and e- of 27 GeV in the neutral (NC) and charged (CC) current interactions as functions of the squared four-momentum transfer, Q2, and of the fractional proton momentum carried by partons, x. The structure function F2, as well as the ?-Z0 interference term xF3, have been measured in a range of Q2 and 1/x that extends by orders of magnitude that reached by fixed target experiments. The DGLAP evolution equations [1] allow for a perturbative NLO QCD fit of the measured non-perturbative structure functions in the available kinematic range: ?S and the gluon density at low x are fitted at the same time with good precision. The longitudinal structure function, FL, can be determined within the DGLAP formalism. With CC, the electroweak unification has been tested; at high x, a first flavor decomposition of the light quarks is achieved. The contribution to F2 of the charm quark has been measured and results to be relevant. Bounds on the radius of quarks and on compositeness are derived from the data at the highest Q2, 100

Stella, Bruno

2001-10-01

344

Neutrino-pair bremsstrahlung from nucleon-$\\alpha$ versus nucleon-nucleon scattering  

CERN Document Server

We study the impact of the nucleon-$\\alpha$ P-wave resonances on neutrino-pair bremsstrahlung. Because of the non-central spin-orbit interaction, these resonances lead to an enhanced contribution to the nucleon spin structure factor for temperatures $T \\lesssim 4$ MeV. If the $\\alpha$-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 non-central nucleon-nucleus interactions.

Sharma, Rishi; Schwenk, Achim

2014-01-01

345

Three-Nucleon Forces Revisited - Some Historical Thoughts  

CERN Document Server

Historic steps in the emergence, the derivation and the use of three-nucleon forces, genuine and effective, for calculations of few-nucleon systems and of the structure of heavier nuclei are recalled. The research focus is on few-nucleon systems. The need of three-nucleon forces for a successful description of some data and the remaining puzzles of other data, not explainable despite the inclusion of three-nucleon forces, are discussed.

Sauer, Peter U

2013-01-01

346

Comparing Some Nucleon-Nucleon Potentials  

CERN Document Server

The aim is to compare a few Nucleon-Nucleon (NN) potentials especially Reid68, Reid68-Day, Reid93, UrbanaV14, ArgonneV18, Nijmegen 93, Nijmegen I, Nijmegen II. Although these potentials have some likenesses and are almost phenomenological, they include in general different structures and its own characteristics. The potentials are constructed in a manner that fit the NN scattering data or phase shifts and are compared in this way. A high-quality scale of a potential is that it fits the data with $\\chi^{2}/N_{data} \\approx 1$, describes well deuteron properties or gives satisfactory results in nuclear structure calculations. However, these scales have some failures. Here, we first compare many potentials by confronting with data. Then, we try to compare the potential forms by considering the potential structures directly and therefore regarding their substantial basis somehow. On the other hand, since the potentials are written in different schema, it is necessary to write the potentials in a unique schema to ...

Naghdi, M

2013-01-01

347

Characteristic features of the asymptotics of the structure functions of light nuclei  

International Nuclear Information System (INIS)

A detailed study of the structure functions of the 6He and 6Li nuclei is carried out within a three-particle model using the variational method with a Gaussian basis. The density distributions of halo nucleons are studied and compared with the calculated distributions of extra nucleons in 10Be and 10C treated within a four-particle model. Common and distinct features of the calculated charge form factors of the above nuclei are explained. For the three-particle 6He and 6Li nuclei, a detailed analytical and numerical study of the asymptotics of the density distributions of constituting particles is carried out. The problem of the asymptotics of form factors is analyzed. The variational method with optimized Gaussian bases is shown to have high accuracy enough to analyze the asymptotics of structure functions of the nuclei both in the coordinate and momentum representations.

348

Sensitivity to properties of the phi-meson in the nucleon structure in the chiral soliton model  

Energy Technology Data Exchange (ETDEWEB)

The influence of the {phi}-meson on the nucleon properties in the chiral soliton model is discussed. Properties of the {phi}-meson and its photo- and electroproduction are of fundamental interest to CEBAF and its possible future extension. The quark model assigns {phi} an s{bar s} structure, thus forbidding the radiative decay {phi}{yields}{pi}{sup 0}{gamma}. Experimentally it is also found to be suppressed, yielding a branching fraction of 1.3{times}10{sup {minus}3}. However, {phi}{yields}{rho}{pi} and {phi}{yields}{pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} are not suppressed at all. Thus, it is possible to incorporate the widths of these decays into the framework of the chiral soliton model, by making use of a specific model for the compliance with OZI rule. Such a model is for example, the {omega}-{phi} mixing model. Consequence of this in the context of a chiral soliton model, which builds on the {pi}{rho}{omega}a{sub 1}(f{sub 1}) meson effective Lagrangian, is the context of this report.

Mukhopadhyay, N.C.; Zhang, L. [Rensselaer Polytechnic Inst., Troy, NY (United States)

1994-04-01

349

Etude de la structure interne du nucleon en diffusion profondement inelastique de muons sur cibles fixes.  

CERN Document Server

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

350

Statistical error analysis for phenomenological nucleon-nucleon potentials  

Science.gov (United States)

Nucleon-nucleon potentials are common in nuclear physics and are determined from a finite number of experimental data with limited precision sampling the scattering process. We study the statistical assumptions implicit in the standard least-squares ?2 fitting procedure and apply, along with more conventional tests, a tail-sensitive quantile-quantile test as a simple and confident tool to verify the normality of residuals. We show that the fulfillment of normality tests is linked to a judicious and consistent selection of a nucleon-nucleon database. These considerations prove crucial to a proper statistical error analysis and uncertainty propagation. We illustrate these issues by analyzing about 8000 proton-proton and neutron-proton scattering published data. This enables the construction of potentials meeting all statistical requirements necessary for statistical uncertainty estimates in nuclear structure calculations.

Navarro Pérez, R.; Amaro, J. E.; Ruiz Arriola, E.

2014-06-01

351

Statistical Error analysis of Nucleon-Nucleon phenomenological potentials  

CERN Document Server

Nucleon-Nucleon potentials are commonplace in nuclear physics and are determined from a finite number of experimental data with limited precision sampling the scattering process. We study the statistical assumptions implicit in the standard least squares fitting procedure and apply, along with more conventional tests, a tail sensitive quantile-quantile test as a simple and confident tool to verify the normality of residuals. We show that the fulfilment of normality tests is linked to a judicious and consistent selection of a nucleon-nucleon database. These considerations prove crucial to a proper statistical error analysis and uncertainty propagation. We illustrate these issues by analyzing about 8000 proton-proton and neutron-proton scattering published data. This enables the construction of potentials meeting all statistical requirements necessary for statistical uncertainty estimates in nuclear structure calculations.

Perez, R Navarro; Arriola, E Ruiz

2014-01-01

352

CREATINE KINASE: STRUCTURE AND FUNCTION  

Directory of Open Access Journals (Sweden)

Full Text Available TEIXEIRA, A. M.; BORGES, G. F. Creatine kinase: structure and function. Brazilian Journal of Biomotricity. v. 6, n. 2, p. 53-65, 2012. Found in all vertebrates, creatine kinase (CK is a member of the phosphagen kinase family and catalyzes the reversible phosphotransfer between the ATP/ADP and Creatine/Phosphocreatine systems. CK is highly expressed in excitable tissues that require large energy fluxes and plays a significant role in the energy homeostasis of these tissue cells. The creatine kinase reaction was first identified in 1934 by K Lohman in the muscle tissue and it has undergone intensive investigation for over 80 years. The enzyme is of clinical importance and its levels are routinely used as an indicator of acute myocardial infarction. There are four major CK isoforms, which are named according to their tissue distribution or subcellular localization: two tissue (muscle or brain cytosolic and two mitochondrial, which form dimers and octamers, respectively. In this paper we will include a brief summary of the history of the detection of creatine kinases isoforms, their main structural features, physical and catalitic properties and multiple functions such as an energy buffering function, metabolic regulatory functions and the energy transport function.

Grasiely F. Borges

2012-06-01

353

Cell Structure and Function Lessons  

Science.gov (United States)

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.

Waldron, Ingrid

354

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

CERN Document Server

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 the quark-parton level.

Kumano, S

1993-01-01

355

On the electron structure function  

International Nuclear Information System (INIS)

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 corrections to the naive evolution procedure are found. Phenomenological applications at present and future momentum scales are discussed. (author)

356

A study of nuclear structure using heavy-ion induced three-nucleon transfer reactions on 15N, 16O, 17O and 18O  

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.)

357

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

CERN Document Server

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

358

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)

359

Nuclear Dependence in Weak Structure Functions and the Determination of Weak Mixing Angle  

CERN Document Server

We have studied nuclear medium effects in the weak structure functions $F^A_2(x)$ and $F^A_3(x)$ and in the extraction of weak mixing angle using Paschos Wolfenstein(PW) relation. We have modified the PW relation for nonisoscalar nuclear target. We have incorporated the medium effects like Pauli blocking, Fermi motion, nuclear binding energy, nucleon correlations, pion $\\&$ rho cloud contributions, and shadowing and antishadowing effects.

Athar, M Sajjad; Simo, I Ruiz; Vacas, M J Vicente

2013-01-01

360

Perturbative QCD study of the polarized structure function g1 at Next-to-Leading-Order  

International Nuclear Information System (INIS)

A NLO perturbative study of all available data on polarized structure function g1(x,Q2) is presented. It is first explained how the Q2 evolution was performed using the DGLAP equations, which used with the present data, allow to constrain the behaviour of polarized parton distributions. Implications of such a study are discussed and important quantities are derived such as an estimation of the quark and gluon polarizations in the nucleon. (author)

 
 
 
 
361

Polarized Structure Functions in the Valence Quark and Resonance Regions and the GDH Sum  

Digital Repository Infrastructure Vision for European Research (DRIVER)

I present in this paper the neutron spin physics program in Hall A at Jefferson Laboratory using a polarized helium-3 target. The program encompasses several completed experiments, in which, valuable spin observables (spin dependent structure functions) were measured in order to learn about how the nucleon spin arises from the behavior of the constituents. These experiments also offer a ground for testing our understanding of the strong regime of quantum chromodynamics (QCD)...

Meziani, Z. -e

2003-01-01

362

Production cross sections of dimuons and experimental analysis of hadronic structure functions  

International Nuclear Information System (INIS)

Analysis, by spectrometry (spectrometer Lezard NA3), of the particle structure (nucleons, mesons) and determination of a multiplicative factor (nearly 2) for the Drell-Yan cross section. Description of the experimental apparatus, production of dimuons on hydrogen and heavy nuclei (platinum), exploration of the nucleon (by inelastic diffusion of leptons, especially neutrinos, and use of the parton model), utilization of the Drell-Yan mechanism describing the production of a continuous spectrum of muons pairs (with experimental test), study of the effects (and subsequent corrections) of the quantum chromodynamics on the amplitude of the strong coupling and on the evolution of the hadronic structure observed as a function of the sensor energy, and at last, after presenting how data are processed analysis of the hadronic structure appearing during the pair production of muons of great masses (4.2< M??<8,5 GeV)

363

Shell-structure influence on the multinucleon transfer in nucleon transfer matrix elements  

International Nuclear Information System (INIS)

ed wave functions of the spherical potential well. The numerical values of squares of proton transfer matrix elements found in this work are nearly in coincidence with that presented in [4]. There is a difference between curves of dependencies of the matrix elements under discussion on the relative distance between centres of nuclei when this distance is smaller than sum of nuclei radii. (author)

364

Nucleon properties in nuclear medium  

International Nuclear Information System (INIS)

The modifications of the nucleon structure due to the presence of an external baryon medium are investigated. To that end the Nambu-Jona-Lasinio model is used to evaluate the pion decay constant and the pion and sigma masses at finite density. Those meson properties serve to fix the parameters of the linear chiral sigma model, which is then solved in a variational projected mean field approach in order to obtain nucleon properties. The proton radius shows an increase of 19% and the nucleon mass a decrease of 17% if the medium reaches nuclear matter density. The magnetic moments and axial vector coupling constant are less modified whereas the pion nucleon coupling constant stays practically constant at increasing medium density. All form factors show remarkable reduction at finite transfer momenta. (author). 20 refs, 8 figs, 1 tab

365

Structure in K--nucleon total cross sections below 1.1 GeV/c  

International Nuclear Information System (INIS)

Total cross sections of K-p and K-d have been measured between 410 and 1070 MeV/c with high statistical precision. In addition to the well known ? (1520), ? (1820), and ? (1769), we confirmed the presence of the ? (1692) and the ? (1670). We have also observed several structures which could be Y* resonances: ? (1646), ? (1735), ? (1583), ? (1608), ? (1633), and ? (1715)

366

New model for nucleon generalized parton distributions  

Energy Technology Data Exchange (ETDEWEB)

We describe a new type of models for nucleon generalized parton distributions (GPDs) H and E. They are heavily based on the fact nucleon GPDs require to use two forms of double distribution (DD) representations. The outcome of the new treatment is that the usual DD+D-term construction should be amended by an extra term, {xi} E{sub +}{sup 1} (x,{xi}) which has the DD structure {alpha}/{beta} e({beta},{alpha}, with e({beta},{alpha}) being the DD that generates GPD E(x,{xi}). We found that this function, unlike the D-term, has support in the whole -1 <= x <= 1 region. Furthermore, it does not vanish at the border points |x|={xi}.

Radyushkin, Anatoly V. [JLAB, Newport News, VA (United States)

2014-01-01

367

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 26Al. 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

368

Strangeness in proton and properties of nucleons in nuclear matter revisited  

CERN Document Server

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

369

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.)

370

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

371

Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS and CLAS12  

International Nuclear Information System (INIS)

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 P33(1232), P11(1440), D13(1520), and S11(1535) were determined over a wide range of Q22 in a comprehensive analysis of exclusive single-meson (?+n,?0p) reactions in the electroproduction off protons. Further, CLAS was able to precisely measure ?+??p electroproduction differential cross sections provided by the nearly full kinematic coverage of the detector. The electrocouplings of the P11(1440) and D13(1520) excited states are determined from the exclusive-?+??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? electrocouplings. Preliminary results on the electrocouplings of the S31(1620), S11(1650), D33(1700), and P13(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? structure and in the search for manifestations of the dynamical masses of the dressed quarks. Future CLAS12 N? structure studies at high photon virtualities will considerably extend our capabilities in exploring the nature of confinement in baryons

372

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{sub 2} < 5.0 GeV{sub 2} in a comprehensive analysis of exclusive single-meson ( {pi}{sup +} n, {pi}{sup 0} p) reactions in the electroproduction off protons. Further, we were able to precisely measure {pi}{sup +}{pi}{sup -}p electroproduction differential cross sections provided by the nearly full kinematic coverage of the CLAS detector. And, for the first time, the electrocouplings of the P{sub 11} (1440), D{sub 13} (1520) excited states are determined from the exclusive-{pi}{sup +}{pi}{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* electrocouplings. And 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, which decay preferentially to the N{pi} {pi} final 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* structure and in the search for manifestations of the dynamical masses of the dressed quarks. Future CLAS12 N* structure studies at high photon virtualities will considerably extend our capabilities in exploring the nature of confinement in baryons.

Philip L. Cole, Volker D. Burkert, Ralf W. Gothe, Victor I. Mokeev

2012-12-01

373

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

374

Compton scattering, vector-meson photoproduction, and the partonic structure of the nucleon  

Science.gov (United States)

At moderate and large momentum transfer, high energy vector-meson photoproduction and Compton scattering can be consistently explained by mechanisms based on interactions and exchanges of constituent quarks and gluons. This opens an original window to the partonic structure of hadronic matter by emphasizing the role of quark correlations, quark exchange as implemented through saturating Regge trajectories, and nonperturbative effects in the gluon propagator, which provides us with a bridge to lattice calculations. Compton scattering is directly related to vector-meson photoproduction and enlarges the data set.

Cano, F.; Laget, J. M.

2002-04-01

375

Compton scattering, vector meson photoproduction and the partonic structure of the nucleon  

CERN Document Server

At moderate and large momentum transfer, high energy vector meson photoproduction and Compton scattering can be consistently explained by mechanisms based on interactions and exchanges of constituent quarks and gluons. This opens an original window on the partonic structure of hadronic matter by emphasizing the role of quark correlations, quark exchange as implemented through saturating Regge trajectories and non-perturbative effects in the gluon propagator, which provides us with a bridge with lattice calculations. Compton scattering is directly related to vector meson photoproduction and enlarges the data set.

Cano, F

2002-01-01

376

Measuring spin-dependent structure functions at CEBAF  

Energy Technology Data Exchange (ETDEWEB)

The author analyses whether CEBAF with a 10 GeV beam could contribute significantly to the understanding of spin-dependent deep-inelastic scattering as well as semi-inclusive reactions. The main advantage of CEBAF is the much better attainable statistics, its great disadvantage its comparably low energy, which limits the accessible x-range to about 0.15 to 0.7. Within these constraints CEBAF could provide (1) high precision data which would be very valuable to understand the Q{sup 2} dependence of the spin-dependent structure functions g{sub 1}(x) and G{sub 2}(x) and (2) the by far most precise determination of the third moments of g{sub 1}(x) and g{sub 2}(x) the latter of which the author argues to be related to a fundamental property of the nucleon.

Schaefer, A. [Universitaet Frankfurt (Germany)

1994-04-01

377

Measuring spin-dependent structure functions at CEBAF  

International Nuclear Information System (INIS)

The author analyses whether CEBAF with a 10 GeV beam could contribute significantly to the understanding of spin-dependent deep-inelastic scattering as well as semi-inclusive reactions. The main advantage of CEBAF is the much better attainable statistics, its great disadvantage its comparably low energy, which limits the accessible x-range to about 0.15 to 0.7. Within these constraints CEBAF could provide (1) high precision data which would be very valuable to understand the Q2 dependence of the spin-dependent structure functions g1(x) and G2(x) and (2) the by far most precise determination of the third moments of g1(x) and g2(x) the latter of which the author argues to be related to a fundamental property of the nucleon

378

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

CERN Document Server

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

379

Strange quark and the electromagnetic structure of the nucleon: the first results from the G0 experiment  

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)

380

Supramolecular Structure and Function 9  

CERN Document Server

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

 
 
 
 
381

Study on the resonance structure of the cross section of nucleon-nucleus interaction in matrix element simulation of residual interaction by the random matrix method  

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

382

Polarized structure functions in the valence quark and resonance regions and the GDH sum  

International Nuclear Information System (INIS)

I present in this paper the neutron spin physics program in Hall A at Jefferson Laboratory using a polarized 3He target. The program encompasses several completed experiments, in which, valuable spin observables (spin dependent structure functions) were measured in order to learn about how the nucleon spin arises from the behavior of the constituents. These experiments also offer a ground for testing our understanding of the strong regime of quantum chromodynamics (QCD) the theory of strong interactions through the determination of moments of these structure functions

383

Measurement of inclusive spin structure functions of the deuteron  

International Nuclear Information System (INIS)

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer [Q2=0.27-1.3 (GeV/c)2] and final hadronic state mass in the nucleon resonance region (W=1.08-2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target (15ND3) and detected the scattered electrons with the CEBAF large acceptance spectrometer. From our data, we extract the longitudinal double spin asymmetry Aparallel and the spin structure function g1d. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function g1d and study its approach to both the deep inelastic limit at large Q2 and to the Gerasimov-Drell-Hearn sum rule at the real photon limit (Q2?0). We find that the first moment varies rapidly in the Q2 range of our experiment and crosses zero at Q2 between 0.5 and 0.8 (GeV/c)2, indicating the importance of the ? resonance at these momentum transfers

384

Measurement of inclusive spin structure functions of the deuteron  

Science.gov (United States)

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer [Q2=0.27 1.3 (GeV/c)2] and final hadronic state mass in the nucleon resonance region (W=1.08 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target (15ND3) and detected the scattered electrons with the CEBAF large acceptance spectrometer. From our data, we extract the longitudinal double spin asymmetry A|| and the spin structure function gd1. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function gd1 and study its approach to both the deep inelastic limit at large Q2 and to the Gerasimov-Drell-Hearn sum rule at the real photon limit (Q2?0). We find that the first moment varies rapidly in the Q2 range of our experiment and crosses zero at Q2 between 0.5 and 0.8 (GeV/c)2, indicating the importance of the ? resonance at these momentum transfers.

Yun, J.; Kuhn, S. E.; Dodge, G. E.; Forest, T. A.; Taiuti, M.; Adams, G. S.; Amaryan, M. J.; Anciant, E.; Anghinolfi, M.; Asavapibhop, B.; Asryan, G.; Audit, G.; Auger, T.; Avakian, H.; Barrow, S.; Battaglieri, M.; Beard, K.; Bektasoglu, M.; Bertozzi, W.; Bianchi, N.; Biselli, A. S.; Boiarinov, S.; Bosted, P.; Bouchigny, S.; Bradford, R.; Branford, D.; Brooks, W. K.; Bueltmann, S.; Burkert, V. D.; Butuceanu, C.; Calarco, J. R.; Carman, D. S.; Carnahan, B.; Cetina, C.; Ciciani, L.; Cole, P. L.; Coleman, A.; Connelly, J.; Cords, D.; Corvisiero, P.; Crabb, D.; Crannell, H.; Cummings, J.; Sanctis, E. De; Vita, R. De; Degtyarenko, P. V.; Demirchyan, R. A.; Denizli, H.; Dennis, L. C.; Dharmawardane, K. V.; Djalali, C.; Domingo, J.; Doughty, D.; Dragovitsch, P.; Dugger, M.; Dytman, S.; Eckhause, M.; Efremenko, Y. V.; Egiyan, H.; Egiyan, K. S.; Elouadrhiri, L.; Empl, A.; Farhi, L.; Fatemi, R.; Feuerbach, R. J.; Ficenec, J.; Fissum, K.; Freyberger, A.; Frolov, V.; Funsten, H.; Gaff, S. J.; Gai, M.; Gavalian, G.; Gavrilov, V. B.; Gilad, S.; Gilfoyle, G. P.; Giovanetti, K. L.; Girard, P.; Golovatch, E.; Gordon, C. I.; Griffioen, K. A.; Guidal, M.; Guillo, M.; Guo, L.; Gyurjyan, V.; Hadjidakis, C.; Hancock, D.; Hardie, J.; Heddle, D.; Heimberg, P.; Hersman, F. W.; Hicks, K.; Hicks, R. S.; Holtrop, M.; Hu, J.; Hyde-Wright, C. E.; Ito, M. M.; Jenkins, D.; Joo, K.; Keith, C.; Kelley, J. H.; Khandaker, M.; Kim, K. Y.; Kim, K.; Kim, W.; Klein, A.; Klein, F. J.; Klimenko, A. V.; Klusman, M.; Kossov, M.; Kramer, L. H.; Kuang, Y.; Kuhn, J.; Lachniet, J.; Laget, J. M.; Lawrence, D.; Leksin, G. A.; Loukachine, K.; Major, R. W.; Manak, J. J.; Marchand, C.; McAleer, S.; McNabb, J. W.; McCarthy, J.; Mecking, B. A.; Mestayer, M. D.; Meyer, C. A.; Minehart, R.; Mirazita, M.; Miskimen, R.; Mokeev, V.; Morrow, S.; Muccifora, V.; Mueller, J.; Murphy, L. Y.; Mutchler, G. S.; Napolitano, J.; Nelson, S. O.; Niccolai, S.; Niculescu, G.; Niczyporuk, B.; Niyazov, R. A.; Nozar, M.; O'Rielly, G. V.; Ohandjanyan, M. S.; Opper, A.; Ossipenko, M.; Park, K.; Patois, Y.; Peterson, G. A.; Philips, S.; Pivnyuk, N.; Pocanic, D.; Pogorelko, O.; Polli, E.; Preedom, B. M.; Price, J. W.; Protopopescu, D.; Qin, L. M.; Raue, B. A.; Riccardi, G.; Ricco, G.; Ripani, M.; Ritchie, B. G.; Rock, S.; Ronchetti, F.; Rossi, P.; Rowntree, D.; Rubin, P. D.; Sabourov, K.; Salgado, C. W.; Sapunenko, V.; Sargsyan, M.; Schumacher, R. A.; Serov, V. S.; Sharabian, Y. G.; Shaw, J.; Shuvalov, S. M.; Simionatto, S.; Skabelin, A.; Smith, E. S.; Smith, L. C.; Smith, T.; Sober, D. I.; Sorrell, L.; Spraker, M.; Stepanyan, S.; Stoler, P.; Taylor, S.; Tedeschi, D.; Thoma, U.; Thompson, R.; Todor, L.; Tung, T. Y.; Tur, C.; Vineyard, M. F.; Vlassov, A.; Wang, K.; Weinstein, L. B.; Weller, H.; Welsh, R.; Weygand, D. P.; Whisnant, S.; Witkowski, M.; Wolin, E.; Wood, M. H.; Yegneswaran, A.; Zhang, B.; Zhao, J.; Zhou, Z.

2003-05-01

385

NN ? NN ?: the new frontier in nucleon-nucleon interactions  

International Nuclear Information System (INIS)

The torch in nucleon-nucleon scattering has been passed to experimental and theoretical studies of pion production. Comparing two unitary models shows that most of the structures predicted for spin observables in NN ? NN? are model independent and roughly in agreement with the data. The contribution of rho- exchange is small, indicating the reaction is largely ''peripheral''. The energy dependence of these isobar models is smooth. The largely unstudied reactions producing neutral and negatively-charged pions show richer structure than positively-charged pion production. 6 refs

386

The nucleon-nucleon interaction and the role of the [42] orbital six-quark symmetry  

International Nuclear Information System (INIS)

The short-range part of the nucleon-nucleon interaction is treated in the one-quark and gluon-exchange approximation. The S-wave phase shifts are calculated using the resonating group method. The nucleon-nucleon, ?? and hidden color channels are taken into account. The spatial symmetry [42] is slightly preferred over the fully orbital symmetric state by the larger probability (89%) with which it is contained asymptotically in the nucleon-nucleon channel and by the quark-quark interaction. The orbital [42] symmetry requires a node in the relative S-wave function between the two nucleons. This yields a hard-core phase shift for the singlet and triplet S-waves. (orig.)

387

The triton with long-range chiral N3LO three nucleon forces  

CERN Document Server

Long-range contributions to the three-nucleon force that have been recently worked out in chiral effective field theory at next-to-next-to-next-to-leading order are for the first time included in the triton and the doublet nucleon-deuteron scattering length calculations. The strengths of the two short-range terms available at this order in the chiral expansion are determined from the triton binding energy and the neutron-deuteron doublet scattering length. The structure of the resulting three-nucleon force is explored and effects for the two-nucleon correlation function in the triton are investigated. Expectation values of the individual contributions to the three-nucleon force in the triton are found to be in the range from a few 100 keV to about 1 MeV. Our study demonstrates that the very complicated operator structure of the novel chiral three-nucleon forces can be successively implemented in three-nucleon Faddeev calculations.

Skibinski, R; Topolnicki, K; Witala, H; Epelbaum, E; Gloeckle, W; Krebs, H; Nogga, A; Kamada, H

2011-01-01

388

Triton with long-range chiral N3LO three-nucleon forces  

International Nuclear Information System (INIS)

Long-range contributions to the three-nucleon force that have recently been worked out in chiral effective-field theory at next-to-next-to-next-to-leading order are, for the first time, included in the triton and the doublet nucleon-deuteron scattering length calculations. The strengths of the two short-range terms available at this order in the chiral expansion are determined from the triton binding energy and the neutron-deuteron doublet scattering length. The structure of the resulting three-nucleon force is explored and effects for the two-nucleon correlation function in the triton are investigated. Expectation values of the individual contributions to the three-nucleon force in the triton are found to be in the range of a few hundred kilo-electron volts to about 1 MeV. Our study demonstrates that the very complicated operator structure of the novel chiral three-nucleon forces can be successively implemented in three-nucleon Faddeev calculations.

389

Universality of nucleon–nucleon short-range correlations and nucleon momentum distributions  

International Nuclear Information System (INIS)

By analyzing recent microscopic many-body calculations of few-nucleon systems and complex nuclei performed by different groups in terms of realistic nucleon–nucleon (NN) interactions, it is shown that NN short-range correlations (SRCs) have a universal character, in that the correlation hole that they produce in nuclei appears to be almost A-independent and similar to the correlation hole in the deuteron. The correlation hole creates high-momentum components, missing in a mean-field (MF) description and exhibiting several scaling properties and a peculiar spin–isospin structure. In particular, the momentum distribution of a pair of nucleons in spin–isospin state (ST) = (10), depending upon the pair relative (krel) and center-of-mass (c.m.) (Kc.m.) momenta, as well as upon the angle ? between them, exhibits a remarkable property: in the region krel?2 fm-1 and Kc.m.?1 fm-1, the relative and c.m. motions are decoupled and the two-nucleon momentum distribution factorizes into the deuteron momentum distribution and an A-dependent momentum distribution describing the c.m. motion of the pair in the medium. The impact of these and other properties of one- and two-nucleon momentum distributions on various nuclear phenomena, on ab initio calculations in terms of low-momentum interactions, as well as on ongoing experimental investigations of SRCs, are briefly commented. (author)

390

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

International Nuclear Information System (INIS)

We derive density-dependent corrections to the in-medium nucleon-nucleon interaction from the leading-order chiral three-nucleon force arising at next-to-next to leading order (N2LO) in the chiral expansion. We consider first a medium of isospin symmetric nuclear matter with density ? and subsequently generalize to a medium with a small isospin asymmetry. At leading order there are six distinct one-loop diagrams contributing to the in-medium nucleon-nucleon interaction, which we combine with the low-momentum potential Vlow-k to obtain an effective density-dependent interaction. We suggest that these results should be useful for nuclear structure calculations of medium- and heavy-mass nuclei, where a direct implementation of the three-nucleon force is computationally prohibitive. We apply these results also to a study of the Fermi liquid parameters of symmetric nuclear matter that characterize the interaction of quasi-particles on the Fermi surface.

391

Nucleon-Nucleon Interactions on the Lattice  

CERN Document Server

We consider the nucleon-nucleon potential in quenched and partially-quenched QCD. The leading one-meson exchange contribution to the potential is found to fall off exponentially at long-distances, in contrast with the Yukawa-type behaviour found in QCD. This unphysical component of the two-nucleon potential has important implications for the extraction of nuclear properties from lattice simulations.

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

2002-01-01

392

Structures and Functions of Oligosaccharins  

Energy Technology Data Exchange (ETDEWEB)

We have made considerable progress during the 2.5 year funding period just ending in our studies of the structures and functions of oligosaccharide signal molecules (oligosaccharins). We have emphasized studies of the enzymes that solubilize, process, and degrade oligosaccharins and of the proteins that inhibit those enzymes. We have been especially interested in elucidating how oligosaccharins and their processing enzymes participate in determining the outcome of challenges to plants by pathogenic microbes. We have studied, to a lesser extent, the roles of oligosaccharins in plant growth and development. Abstracts of papers describing results acquired with support from this grant that have been published, submitted, or in preparation are presented to summarize the progress made during the last two and one half years. The report highlights the most important contributions made in our oiigosaccharin research during this time period, and the corresponding abstract is referenced. Results of work in progress are described primarily in conjunction with our application for continued support.

Albersheim, Peter

1995-12-01

393

On the electromagnetic polarisabilities of the nucleon  

International Nuclear Information System (INIS)

The dynamic electric and magnetic polarisabilities of the nucleon are calculated taking the photon-nucleon resonance vertex-function ambiguity parameters into account. The annihilation channel in the Compton scattering amplitude is also evaluated from the chiral effective Lagrangian. It is found that the electric and magnetic polarisabilities of the proton are of the same order of magnitude. (author)

394

Dilepton production in nucleon-nucleon interactions  

International Nuclear Information System (INIS)

Starting from a realistic one-boson-exchange model fitted to the amplitudes of elastic nucleon-nucleon scattering and the process NN?N? we perform a fully relativistic and gauge-invariant calculation for the dilepton production in nucleon-nucleon collisions, including the important effect of propagating the ?-resonance. We compare the results of our calculations with the latest experimental data on dilepton production. We also show how to implement various electromagnetic form factors for the hadrons in our calculations without losing gauge invariance and discuss their influence on dilepton spectra. ((orig.))

395

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

Science.gov (United States)

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

396

Homing endonuclease structure and function.  

Science.gov (United States)

Homing endonucleases are encoded by open reading frames that are embedded within group I, group II and archael introns, as well as inteins (intervening sequences that are spliced and excised post-translationally). These enzymes initiate transfer of those elements (and themselves) by generating strand breaks in cognate alleles that lack the intervening sequence, as well as in additional ectopic sites that broaden the range of intron and intein mobility. Homing endonucleases can be divided into several unique families that are remarkable in several respects: they display extremely high DNA-binding specificities which arise from long DNA target sites (14-40 bp), they are tolerant of a variety of sequence variations in these sites, and they display disparate DNA cleavage mechanisms. A significant number of homing endonucleases also act as maturases (highly specific cofactors for the RNA splicing reactions of their cognate introns). Of the known homing group I endonuclease families, two (HNH and His-Cys box enzymes) appear to be diverged from a common ancestral nuclease. While crystal structures of several representatives of the LAGLIDADG endonuclease family have been determined, only structures of single members of the HNH (I-HmuI), His-Cys box (I-PpoI) and GIY-YIG (I-TevI) families have been elucidated. These studies provide an important source of information for structure-function relationships in those families, and are the centerpiece of this review. Finally, homing endonucleases are significant targets for redesign and selection experiments, in hopes of generating novel DNA binding and cutting reagents for a variety of genomic applications. PMID:16336743

Stoddard, Barry L

2005-02-01

397

Chiral Symmetry and the Nucleon-Nucleon Interaction  

CERN Document Server

The main progress in the field of nucleon-nucleon (NN) potentials, which we have seen in recent years, is the construction of some very quantitative (high-quality/high-precision) NN potentials. These potentials will serve as excellent input for microscopic nuclear structure calculations and will allow for a systematic investigation of off-shell effects. After this enormous quantitative work, it is now time to re-think the NN problem in fundamental terms. We need a derivation of the nuclear force which observes Lorentz invariance and the symmetries of QCD.

Machleidt, R

1998-01-01

398

Study of nucleon-nucleon and hyperon-nucleon interaction  

International Nuclear Information System (INIS)

In this paper we review recent investigations of nucleon-nucleon and hyperon-nucleon interactions employing a non-relativistic quark cluster model. We concentrate mainly on the short and medium-range behavior of the baryon-baryon interaction based on the one-gluon and meson exchange potentials. The chiral quark model based on pion and sigma exchange between quarks is also discussed. We also review a study of the deuteron and its electromagnetic properties in a quark model with exchange currents. (author)

399

Study of nucleon-nucleon and hyperon-nucleon interaction  

Energy Technology Data Exchange (ETDEWEB)

In this paper we review recent investigations of nucleon-nucleon and hyperon-nucleon interactions employing a non-relativistic quark cluster model. We concentrate mainly on the short and medium-range behavior of the baryon-baryon interaction based on the one-gluon and meson exchange potentials. The chiral quark model based on pion and sigma exchange between quarks is also discussed. We also review a study of the deuteron and its electromagnetic properties in a quark model with exchange currents. (author)

Shimizu, Kiyotaka [Department of Physics, Sophia University, Tokyo (Japan); Takeuchi, Sachiko [Japan College of Social Work, Kiyose (Japan); Buchmann, A.J. [Institute for Theoretical Physics, University of Tuebinge (Germany)

2000-04-01

400

Conflicting coupling of the unpaired nucleons and the structure of collective bands in odd-odd nuclei  

CERN Document Server

Conflicting coupling of unpaired nucleons in the odd-odd nuclei is discussed. A very simple explanation is suggested for the damping of the energy spacing of the lowest levels in the rotational bands in the odd-odd nuclei in the case of a "conflicting" coupling of the odd proton and neutron comparative to those of the bands based on the state of the strongly-coupled particle in the neighbouring odd nuclei entering the "conflicting" configuration.

Levon, A I

2011-01-01

 
 
 
 
401

Three-Nucleon Forces  

CERN Document Server

The role of three-nucleon forces in ab initio calculations of nuclear systems is investigated. The difference between genuine and induced many-nucleon forces is emphasized. Induced forces arise in the process of solving the nuclear many-body problem as technical intermediaries towards calculationally converged results. Genuine forces make up the Hamiltonian; they represent the chosen underlying dynamics. The hierarchy of contributions arising from two-, three- and many-nucleon forces is discussed. Signals for the need of the inclusion of genuine three-nucleon forces are studied in nuclear systems, technically best under control, especially in three-nucleon and four-nucleon systems. Genuine three-nucleon forces are important for details in the decription of some observables. Their contributions to observables are small on the scale set by two-nucleon forces.

Sauer, Peter U

2014-01-01

402

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

403

Nucleon decay experiments  

International Nuclear Information System (INIS)

The paper reviews recent experimental results on nucleon stability. The presently running experiments on nucleon decay that are considered,include: the Kolar Gold field, IMB, HPW and Kamioka experiments. The results of these experiments are discussed and compared. Future nucleon decay experiments are described. Neutron-antineutron oscillations in nuclei are also examined. (U.K.)

404

Medium effects on nucleon properties  

International Nuclear Information System (INIS)

The modifications of the nucleon structure due to the presence of an external baryon medium are investigated in a chiral nonlinear quark-meson theory. To this end the Nambu-Jona-Lasinio approach is used to evaluate the pion decay constant and the pion and sigma masses at finite density. Those meson properties serve to fix the parameters of the linear chiral sigma model, which is then solved in a variational projected mean field approach in order to obtain nucleon properties. The proton radius shows an increase of 22% and the nucleon mass a decrease of 17% if the medium reaches nuclear matter density. The axial vector coupling constant is reduced by about 10% and the electric form factors show remarkable changes at q?1 GeV/c. (orig.)

405

Measurements of parity-violating asymmetries in electron-deuteron scattering in the nucleon resonance region.  

Science.gov (United States)

We report on parity-violating asymmetries in the nucleon resonance region measured using inclusive inelastic scattering of 5-6 GeV longitudinally polarized electrons off an unpolarized deuterium target. These results are the first parity-violating asymmetry data in the resonance region beyond the ?(1232). They provide a verification of quark-hadron duality-the equivalence of the quark- and hadron-based pictures of the nucleon-at the (10-15)% level in this electroweak observable, which is dominated by contributions from the nucleon electroweak ?Z interference structure functions. In addition, the results provide constraints on nucleon resonance models relevant for calculating background corrections to elastic parity-violating electron scattering measurements. PMID:24016222

Wang, D; Pan, K; Subedi, R; Deng, X; Ahmed, Z; Allada, K; Aniol, K A; Armstrong, D S; Arrington, J; Bellini, V; Beminiwattha, R; Benesch, J; Benmokhtar, F; Camsonne, A; Canan, M; Cates, G D; Chen, J-P; Chudakov, E; Cisbani, E; Dalton, M M; de Jager, C W; De Leo, R; Deconinck, W; Deur, A; Dutta, C; El Fassi, L; Flay, D; Franklin, G B; Friend, M; Frullani, S; Garibaldi, F; Giusa, A; Glamazdin, A; Golge, S; Grimm, K; Hafidi, K; Hansen, O; Higinbotham, D W; Holmes, R; Holmstrom, T; Holt, R J; Huang, J; Hyde, C E; Jen, C M; Jones, D; Kang, H; King, P; Kowalski, S; Kumar, K S; Lee, J H; LeRose, J J; Liyanage, N; Long, E; McNulty, D; Margaziotis, D J; Meddi, F; Meekins, D G; Mercado, L; Meziani, Z-E; Michaels, R; Mihovilovic, M; Muangma, N; Myers, K E; Nanda, S; Narayan, A; Nelyubin, V; Nuruzzaman; Oh, Y; Parno, D; Paschke, K D; Phillips, S K; Qian, X; Qiang, Y; Quinn, B; Rakhman, A; Reimer, P E; Rider, K; Riordan, S; Roche, J; Rubin, J; Russo, G; Saenboonruang, K; Saha, A; Sawatzky, B; Shahinyan, A; Silwal, R; Sirca, S; Souder, P A; Suleiman, R; Sulkosky, V; Sutera, C M; Tobias, W A; Urciuoli, G M; Waidyawansa, B; Wojtsekhowski, B; Ye, L; Zhao, B; Zheng, X

2013-08-23

406

?N sigma term and chiral-odd twist-3 distribution function e(x) of the nucleon in the chiral quark soliton model  

Science.gov (United States)

The isosinglet combination of the chiral-odd twist-3 distribution function eu(x)+ed(x) of the nucleon has the outstanding properties that its first moment is proportional to the well-known ?N sigma term and that it contains a ?-function singularity at x=0. These two features are inseparably connected in that the above sum rule would be violated if there is no such singularity in eu(x)+ed(x). Very recently, we found that the physical origin of this ?-function singularity can be traced back to the long-range quark-quark correlation of scalar type, which signals the spontaneous chiral symmetry breaking of the QCD vacuum. The main purpose of the present paper is to give complete theoretical predictions for the chiral-odd twist-3 distribution function ea(x) of each flavor a on the basis of the chiral quark soliton model, without recourse to the derivative-expansion-type approximation. These theoretical predictions are then compared with the empirical information extracted from the CLAS data of the semi-inclusive DIS processes by assuming the Collins mechanism only. A good agreement with the CLAS data is indicative of a sizable violation of the ?N sigma-term sum rule or, equivalently, the existence of a ?-function singularity in eu(x)+ed(x).

Ohnishi, Y.; Wakamatsu, M.

2004-06-01

407

Polarization phenomena in nucleon-nucleon scattering at intermediate and high energies including the present status of dibaryons  

Energy Technology Data Exchange (ETDEWEB)

We review experimental results concerning polarization phenomena in nucleon-nucleon scattering in which both the elastic scattering and hadron-production reaction are included. We also present summary of S = 0 dibaryon resonances and candidates by reviewing experimental data in the nucleon-nucleon system, ..gamma..d channel, ..pi..d elastic scattering, pp ..-->.. ..pi..d channel, deuteron break-up reactions, and narrow structures in missing-mass spectra. 93 refs., 26 figs.

Yokosawa, A.

1985-01-01

408

Universality of nucleon-nucleon short-range correlations and nucleon momentum distributions  

CERN Document Server

By analyzing recent microscopic many-body calculations of few-nucleon systems and complex nuclei performed by different groups in terms of realistic nucleon-nucleon (NN) interactions, it is shown that NN short-range correlations (SRCs) have a universal character, in that the correlation hole that they produce in nuclei appears to be almost A-independent and similar to the correlation hole in the deuteron. The correlation hole creates high-momentum components, missing in a mean-field (MF) description and exhibiting several scaling properties and a peculiar spin-isospin structure. In particular, the momentum distribution of a pair of nucleons in spin-isospin state $(ST)=(10)$, depending upon the pair relative ($k_{rel}$) and center-of-mass (c.m.) ($K_{c.m.}$) momenta, as well as upon the angle $\\Theta$ between them, exhibits a remarkable property: in the region $k_{rel}\\gtrsim 2\\,fm^{-1}$ and $K_{c.m.}\\lesssim 1\\,fm^{-1} $, the relative and c.m. motions are decoupled and the two-nucleon momentum distribution fa...

Alvioli, Massimiliano; Kaptari, Leonid P; Mezzetti, Chiara Benedetta; Morita, Hiko

2013-01-01

409

Effective constraint algebras with structure functions  

CERN Document Server

This article presents the result that fluctuations and higher moments of a state do not imply quantum corrections in structure functions of constrained systems. Consequences for canonical quantum gravity, whose structure functions encode space-time structure, are discussed. In particular, deformed algebras found in models of loop quantum gravity provide reliable information even in the Planck regime.

Bojowald, Martin

2014-01-01

410

One-nucleon transfer reactions induced by secondary beam of 11Be: study of the nuclear structure of the exotic nuclei 11Be and 10Li  

International Nuclear Information System (INIS)

The structure of the neutron rich light nuclei 11Be and 10Li has been investigated by means of one nucleon transfer reactions. The experiments have been carried out at GANIL in inverse kinematics using 11Be secondary beams. The 11Be(p,d)10Be reaction bas been studied at 35.3 MeV/u. The 10Be ejectiles were analyzed by the spectrometer SPEG, and coincident deuterons were detected in the position sensitive silicon detector CHARISSA. Transfer cross sections to 0+1 and 2+1, states in 10Be were measured up to ?CM = 16 deg. and compared to DWBA and CRC predictions. The effects of neutron-cure couplings on reaction form factors have been studied by solving coupled equations in the framework of a vibrational model. It is shown that the rate of core excitation 10Be2+ in the 11Begs wave function is overestimated by a standard analysis with form factors given by the usual Separation Energy prescription. The former model predicts a rate of core excitation of 16% and leads to theoretical cross sections which are in good agreement with the experimental data. The aim of the 11Be(d,3He)10Li experiment, realized at 37 MeV/u, was to measure the distribution of the 2s neutron strength in the unbound nucleus 10Li. The energy spectrum was deduced from the 3He energy and angle measured by the silicon strip detector array MUST. An asymmetric peak is clearly observed near the threshold, with a maximum at -Sn = 130 keV. This constitutes a direct proof of the inversion of 2s and 1p1/2 shells in 10Li, which was until now a controversial question in spite of many experimental efforts. On the other band the analysis of the 11Be(d,t)10Be reaction studied in the same experiment confirms the results obtained in the 11Be(p,d)10Be reaction concerning the 11Begs structure. This work shows the interest and feasibility of studies of the shell properties of exotic nuclei using transfer reactions induced by radioactive beams and constitutes the beginning of a program devoted to this kind of experiment. (author)

411

Nucleon-nucleon cross sections via stochastic processes in phase space: One-dimensional scattering  

Science.gov (United States)

One-dimensional nucleon-nucleon scattering is simulated by Monte Carlo techniques in the quasiclassical approximation of the Wigner representation. Nucleons are represented by minimum wave packets of approximate nucleon radii, their linear dispersion offset by intrinsic harmonic oscillation, inducing phase space spin in the nucleon Wigner function. A representative set of points evolve in four-dimensional phase space in deterministic classical and stochastic quantum momentum jumps. In the extended space, the inter-nucleon one-pion exchange potential is defined locally by the point coordinates. By the geometric analogy, cross sections are computed from collision distances considered as impact parameters. Results from the parameter free one-dimensional simulation show reasonable agreement with empirical data in the energy range 0.01 GeV to 5 GeV.

John, Sarah

2007-07-01

412

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

413

Pi N sigma-term and chiral-odd twist-3 distribution function e(x) of the nucleon in the chiral quark soliton model  

CERN Document Server

The isosinglet combination of the chiral-odd twist-3 distribution function $e^u(x)+e^d(x)$ of the nucleon has outstanding properties that its first moment is proportional to the well-known $\\pi N$ sigma-term and that it contains a $\\delta$-function singularity at $x=0$. These two features are inseparably connected in that the above sum rule would be violated, if there is no such a singularity in $e^u(x)+e^d(x)$. Very recently, we found that the physical origin of this $\\delta$-function singularity can be traced back to the long-range quark-quark correlation of scalar type, which signals the spontaneous chiral symmetry breaking of the QCD vacuum. The main purpose of the present paper is to give complete theoretical predictions for the chiral-odd twist-3 distribution function $e^a(x)$ of each flavor $a$ on the basis of the chiral quark soliton model, without recourse to the derivative expansion type approximation. These theoretical predictions are then compared with the empirical information extracted from the ...

Ohnishi, Y

2003-01-01

414

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

415

The form factors of the nucleons  

Energy Technology Data Exchange (ETDEWEB)

The author demonstrates that a relativistic constituent quark model can give nucleon form factors that agree well with recent, accurate measurements. The relativistic features of the model and the specific form of the wave function are essential for the result.

Schlumpf, F.

1994-05-01

416

The form factors of the nucleons  

CERN Document Server

We demonstrate that a relativistic constituent quark model can give nucleon form factors that agree well with recent, accurate measurements. The relativistic features of the model and the specific form of the wave function are essential for the result.

Schlumpf, F

1995-01-01

417

The form factors of the nucleons  

International Nuclear Information System (INIS)

The author demonstrates that a relativistic constituent quark model can give nucleon form factors that agree well with recent, accurate measurements. The relativistic features of the model and the specific form of the wave function are essential for the result

418

The (p, n) reaction and the nucleon-nucleon force  

International Nuclear Information System (INIS)

The (p, n) charge exchange reaction is a powerful tool of nuclear structure physics, with spectroscopic characteristics that are closely related to the free interaction between nucleons. At proton energies in the range of 150-500 MeV, the interaction probes the spin dynamics in the charge exchange process and is particularly sensitive to nuclear pionic fields. At low energies, say less than 50 MeV bombarding energy, the reaction also probes the isovector density. An outstanding success of the reaction as a structural probe is the elucidation of the Gamow-Teller strength function in the nuclear excitation spectrum. However, the total strength found falls short of sum rule predictions by about 40%. Explanations of this quenching have been advanced along two lines, based on subnuclear degrees of freedom or on configuration mixing into high continuum states. Detailed theoretical arguments support the importance of configuration mixing. The subnuclear degrees of freedom may be comparable, but a decisive test is lacking. (author)

419

Sign-symmetry of temperature structure functions  

CERN Document Server

New scalar structure functions with different sign-symmetry properties are defined. These structure functions possess different scaling exponents even when their order is the same. Their scaling properties are investigated for second and third orders, using data from high-Reynolds-number atmospheric boundary layer. It is only when structure functions with disparate sign-symmetry properties are compared can the extended self-similarity detect two different scaling ranges that may exist, as in the example of convective turbulence.

Aivalis, K G; Schumacher, J; Sreenivasan, K R; Aivalis, Konstantinos G.; Kurien, Susan; Schumacher, Joerg; Sreenivasan, Katepalli R.

2004-01-01

420

Sign-symmetry of temperature structure functions.  

Science.gov (United States)

New scalar structure functions with different sign-symmetry properties are defined. These structure functions possess different scaling exponents even when their order is the same. Their scaling properties are investigated for second and third orders, using data from high-Reynolds-number atmospheric boundary layer. It is only when structure functions with disparate sign-symmetry properties are compared can the extended self-similarity detect two different scaling ranges that may exist, as in the example of convective turbulence. PMID:15244734

Aivalis, Konstantinos G; Kurien, Susan; Schumacher, Jörg; Sreenivasan, Katepalli R

2004-06-01

 
 
 
 
421

Kinematically complete analysis of the CLAS data on the proton structure function F2 in a Regge-dual model  

Science.gov (United States)

The recently measured inclusive electron-proton cross section in the nucleon resonance region, performed with the CLAS detector at the Thomas Jefferson Laboratory, has provided new data for the nucleon structure function F2 with previously unavailable precision. In this paper we propose a description of these experimental data based on a Regge-dual model for F2. The basic inputs in the model are nonlinear complex Regge trajectories producing both isobar resonances and a smooth background. The model is tested against the experimental data, and the Q2 dependence of the moments is calculated. The fitted model for the structure function (inclusive cross section) is a limiting case of the more general scattering amplitude equally applicable to deeply virtual Compton scattering. The connection between the two is discussed.

Fiore, R.; Flachi, A.; Jenkovszky, L. L.; Lengyel, A. I.; Magas, V. K.

2004-01-01

422

Graphs of three-body wave functions  

International Nuclear Information System (INIS)

Plots of numerical solutions of the Faddeev equations in configuration space are presented for both bound and scattering three-body systems. Comparisons of the Faddeev amplitudes with the total wave functions are made for various nucleon-nucleon interactions. We find that the Faddeev amplitude is a much smoother function than the total wave function, and that for a repulsive interaction the structure of the Faddeev amplitude is much different than the structure of the total wave function. (orig.)

423

Short-Range Nucleon-Nucleon Correlations  

CERN Document Server

Valence-shell nucleon knock-out experiments, such as 12C(e,e'p)11B, measure less strength then is predicted by independent particle shell model calculations. The theoretical solution to this problem is to include the correlations between the nucleons in the nucleus in the calculations. Motivated by these results, many electron scattering experiments have tried to directly observe these correlations in order to gain new insight into the short-range part of the nucleon-nucleon potential. Unfortunately, many competing mechanisms can cause the same observable final-state as an initial-state correlation, making truly isolating the signal extremely challenging. This paper reviews the recent experimental evidence for short-range correlations, as well as explores the possibility that such correlations are responsible for the EMC effect in the 0.3 < xB < 0.7 deep inelastic scattering ratios.

Higinbotham, Douglas W

2010-01-01

424

Spin structure functions of the proton and the neutron at low to moderate Q^2  

Science.gov (United States)

The physics program with CLAS at the Jefferson Lab has collected a large amount of data on the spin structure functions of the nucleon by using polarized electron beam directed on polarized NH3 and ND3 targets. In these experiments, the virtual photon asymmetry A1 and the spin structure function g1 were measured with an unprecedented precision in a large kinematic range of 0.01 GeV^2 gluon degrees of freedom. Therefore, it will be possible to put limits on quark-hadron duality, test pQCD predictions for the quark polarization at large x, perform more precise calculations of higher-twist matrix elements in the framework of the Operator Product Expansion and get a glimpse of A1 at high x. In addition, using available proton and deuteron data together and utilizing a new unfolding technique, the spin structure functions for the neutron in the resonance region are extracted.

Guler, Nevzat

2013-04-01

425

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

426

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.)

427

Using Drell-Yan Processes to Probe Nucleon and Meson Structure Functions  

CERN Document Server

We investigate how Drell-Yan processes can be used to measure the magnitude of flavor symmetry violation in the proton sea. We examine the utility of the following beams: protons, charged pions, and charged kaons. In each case we present an approximate expression for the Drell-Yan asymmetry. Using currently available parton distributions, we locate those kinematic regions which provide the greatest information on the quantity $\\bar{d}^p(x) - \\bar{u}^p(x)$. If sufficiently intense $K^+$ beams were available, they could provide an efficient measurement of this quantity. Finally we present and discuss sets of sum rules for the Drell-Yan processes.

Bhalerao, R S

1998-01-01

428

Structure and functional properties of colloidal systems  

CERN Document Server

Presents the connections between structure and functional aspects in colloid and interface science. This title describes techniques to functionalize colloids, characterization methods, the physical fundamentals of structure formation, diffusion dynamics, transport properties in equilibrium, and the physical fundamentals of nonequilibrium systems.

Hidalgo-Alvarez, Roque

2009-01-01

429

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/

430

Nucleon in Nuclear Matter  

Directory of Open Access Journals (Sweden)

Full Text Available The modification of the properties of nucleon in nuclear medium has been investigated in the context of flux tube model. A nucleon has been described as diquark-quark system connected by flux tube and quasi particle diquark model has been used to describe the diquak constituting the nucleon. The modification of incompressiblity, the Roper resonance etc in the nuclear medium have been investigated. The results are compared with recent experimental and theoretical predictions. Some interesting observations are made.

Aparajita Bhattacharya

2011-02-01

431

What Causes Transverse Single-Spin Asymmetries in Lepton-Nucleon and in Nucleon-Nucleon Scattering?  

Science.gov (United States)

Transverse single-spin asymmetries are among the most intriguing observables in hadronic physics. Though such asymmetries were already measured for the first time about four decades ago, their origin is still under debate. Here we consider transverse single-spin asymmetries in semi-inclusive lepton-nucleon scattering, in nucleon-nucleon scattering, and in inclusive lepton-nucleon scattering. It is argued that the single-spin asymmetries for those three processes may be simultaneously described in perturbative QCD, where the re-scattering of the active partons plays a crucial role. A comparison of single-spin asymmetries in different reactions can also shed light on the universality of transverse momentum dependent parton correlation functions. In particular, we discuss what existing data tells us about the predicted process dependence of the Sivers function.

Metz, Andreas; Pitonyak, Daniel; Schäfer, Andreas; Schlegel, Marc; Vogelsang, Werner; Zhou, Jian

2014-01-01

432

A study of two nucleon W- matrices  

International Nuclear Information System (INIS)

The free two nucleon W-matrices are studied for a number of two nucleon channels, including coupled channels, and over a range of lab. energies to 250 MeV. For realistic interactions these W-matrices are shown to be simple, smooth and real functions of (half-on-shell) momenta. The free two nucleon t-matrices are expanded in separable form by the W-matrices and the (fully-off-shell) remainder matrices left thereby should have negligible effect in any (low energy) few body calculation. 9 refs., 3 tabs., 5 figs

433

Orbital angular momentum in the nucleons  

CERN Document Server

In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular momentum and its extraction from experimental data. We summarize the present situation and discuss recent developments in this field.

Lorcé, Cédric

2014-01-01

434

Improved chiral nucleon-nucleon potential up to next-to-next-to-next-to-leading order  

CERN Document Server

We present improved nucleon-nucleon potentials derived in chiral effective field theory up to next-to-next-to-next-to-leading order. We argue that the nonlocal momentum-space regulator employed in the two-nucleon potentials of Refs. [E. Epelbaum, W. Gloeckle, U.-G. Mei{\\ss}ner, Nucl. Phys. A747 (2005) 362], [D.R. Entem, R. Machleidt, Phys. Rev. C68 (2003) 041001] is not the most efficient choice, in particular since it affects the long-range part of the interaction. We are able to significantly reduce finite-cutoff artefacts by using an appropriate regularization in coordinate space which maintains the analytic structure of the amplitude. The new potentials do not require the additional spectral function regularization employed in Ref. [E. Epelbaum, W. Gloeckle, U.-G. Mei{\\ss}ner, Nucl. Phys. A747 (2005) 362] to cut off the short-range components of the two-pion exchange and make use of the low-energy constants c_i and d_i determined from pion-nucleon scattering without any fine tuning. We discuss in detail t...

Epelbaum, E; Meißner, U -G

2014-01-01

435

Electromagnetic and weak form factors of nucleon and charged quasielastic scatterings of neutrino (antineutrino) and nucleon  

CERN Document Server

The study of electromagnetic and weak form factors of nucleon (charged quasielastic scatterings of neutrino (antineutrino) and nucleon) done in $70^\\prime s$ and published in Chinese journals is reviewed. In the approach of the study antiquark components are introduced to the wave functions of nucleon and the study shows that the antiquark components of nucleon play an essential role in the EM and weak form factors of nucleon. The SU(6) symmetric wave functions of baryons in the rest frame ( s-wave in the rest frame) have been constructed. In these wave functions there are both quark and antiquark components. Using Lorentz transformations these wave functions are boosted to moving frame. In terms of effective Lagrangian these wave functions are used to study the EM and weak form factors of nucleon and $p \\rightarrow \\Delta$. The ratio $\\mu_p G^p_E/G^p_M$, $G^n_E$, $G^n_M$, $G^*_M$, $E1+$ and $S1+$ of $p \\rightarrow \\Delta$ are predicted. The axial-vector form factors of nucleon is predicted to be $G_A(q^2)/G_...

Li, Bing An

2014-01-01

436

PROCEEDINGS OF RIKEN BNL RESEARCH CENTER, RIKEN WINTER SCHOOL, QUARK GLUON STRUCTURE OF THE NUCLEON AND QCD, MARCH 29-31, 2002.  

Energy Technology Data Exchange (ETDEWEB)

The RIKEN School on ''Quark-Gluon Structure of the Nucleon and QCD'' was held from March 29th through 31st at the Nishina Memorial Hall of RIKEN, Wako, Saitama, Japan, sponsored by RIKEN (the Institute of Physical and Chemical Research). The school was the second of a new series with a broad perspective of hadron and nuclear physics. The purpose of the school was to offer young researchers an opportunity to learn theoretical aspects of hadron physics based on QCD and related experimental programs being or to be carried out by Japanese groups. We had 3 theoretical courses, each consisting of 3 one-hour lectures, and 6 experimental courses, each consisting of a one-hour lecture.

EN YO,H.; SAITO,N.; SHIBATA,T.A.; YAZAKI,K.; BUNCE,G.

2002-03-29

437

Spin-Dependent Structure Functions in Nuclear Matter and the Polarized EMC Effect  

International Nuclear Information System (INIS)

An excellent description of both spin-independent and spin-dependent quark distributions and structure functions has been obtained with a modified Nambu-Jona-Lasinio model, which is free of unphysical thresholds for nucleon decay into quarks--hence incorporating an important aspect of confinement. We utilize this model to investigate nuclear medium modifications to structure functions and find that we are readily able to reproduce both nuclear matter saturation and the experimental F2NA/F2N ratio, that is, the European Muon Collaboration (EMC) effect. Applying this framework to determine g1pA, we find that the ratio g1pA/g1p differs significantly from unity, with the quenching caused by the nuclear medium being about twice that of the spin-independent case. This represents an exciting result, which, if confirmed experimentally, will reveal much about the quark structure of nuclear matter

438

On the polarization of the nucleon sea in the meson cloud model  

CERN Document Server

It is pointed out that the meson cloud model predicts a substantial polarization of the sea quarks of the nucleon due to interference of $\\pi$ and gives an explanation of a strong increase in the structure function $g_1$ with isospin I=1 at small $x$.

Boreskov, K G

1999-01-01

439

Investigation of the neutron structure function via semi-inclusive deep inelastic electron scattering off the deuteron  

CERN Document Server

The production of slow nucleons in semi-inclusive deep inelastic electron scattering off the deuteron is investigated in the region $x \\gsim 0.3$ for kinematical conditions accessible at $HERA$. Within the spectator mechanism the semi-inclusive cross section exhibits a scaling property, which can be used as a model-independent test of the dominance of the spectator mechanism itself, providing in this way an interesting tool to investigate the neutron structure function. The possibility of extracting model-independent information on the neutron to proton structure function ratio from semi-inclusive experiments is also illustrated.

Simula, S

1996-01-01

440

Small-x structure functions from NMC  

International Nuclear Information System (INIS)

The NMC measurements of the proton and deuteron structure functions for 0.006 2 2 and of the neutron-to-proton structure function ratio down to x = 0.0008 are presented. The data agree very well with the earlier results of the BCDMS, SLAC (reanalysed) and EMC NA28 experiments, but disagree with the reanalysed results of the EMC NA2. A parametrization of the low-x structure function F2, incorporating vector meson dominance dynamics and the QCD-improved parton model, valid at arbitrary Q2 and reproducing well the data, is also presented. (Author)

 
 
 
 
441

Determination of the neutron spin structure function  

International Nuclear Information System (INIS)

New measurements of the neutron spin structure function, g1(x), made at SLAC are reported, using longitudinally polarized electrons on a polarized 3He target. The spin structure function of the neutron has been determined from x=0.03 to x=0.6 at an average Q2 of 2 (GeV/c)2, by measuring the asymmetry in deep inelastic scattering of polarized electrons from polarized 3He at energies from 19 to 26 GeV. The integral over the spin structure function has been calculated. (author) 16 refs., 3 figs., 1 tab

442

Transverse Spin Structure of the Nucleon through Target Single Spin Asymmetry in Semi-Inclusive Deep-Inelastic $(e,e^\\prime \\pi^\\pm)$ Reaction at Jefferson Lab  

Energy Technology Data Exchange (ETDEWEB)

Jefferson Lab (JLab) 12 GeV energy upgrade provides a golden opportunity to perform precision studies of the transverse spin and transverse-momentum-dependent structure in the valence quark region for both the proton and the neutron. In this paper, we focus our discussion on a recently approved experiment on the neutron as an example of the precision studies planned at JLab. The new experiment will perform precision measurements of target Single Spin Asymmetries (SSA) from semi-inclusive electro-