WorldWideScience
 
 
1

Review on nucleon structure functions  

Energy Technology Data Exchange (ETDEWEB)

The 1994 preliminary data of the HERA experiments H1 and ZEUS on the proton structure function are presented, together with the final data of the muon fixed target experiments E665 at FNAL and NMC at CERN. Perturbative QCD interpretations and extraction of {alpha}{sub s} at low {chi} are discussed. (author). 55 refs.

Feltesse, J.

1995-12-01

2

Phenomenological study of the nucleon structure functions  

International Nuclear Information System (INIS)

This thesis is devoted to the study of the deep inelastic scattering. Its purpose is the development of phenomenological models describing experimental results on unpolarized (F2) and polarized (g1) nucleon structure functions in the wide range of the kinematical domain. Special attention is paid to the small-x behaviour of F2 and to the link between deep inelastic scattering and photoproduction process. The investigation of the Pomeron in deep inelastic scattering shows that one single Pomeron compatible with the Froissard-Martin limit can account for all the present HERA data. A phenomenological model of the proton structure function is developed, based on a two-component structure including various features expected from both perturbative quantum chromodynamics and non perturbative Regge theory. A link with the photoproduction process is provided. A detailed analysis of the perturbative components, based on the Gribov-Lipatov-Altarelli-Parisi evolution equations is presented. Taking into account the different parton distribution, this approach allows to describe data on proton and neutron structure functions, on deep inelastic neutrino scattering, and to reproduce the gluons distribution extracted by the ZEUS collaboration. The model is applied to the polarized deep inelastic scattering and the axial anomaly effect appearing both in the description of results on the spin dependent structure functions gp,n,d and in the interpretation of the nucleon spin structure is discussed. (J.S.). 260 refs., 34 figs., 8 tabs., 6 appends

1995-01-01

3

Structure functions of the meson-nucleon interaction  

International Nuclear Information System (INIS)

We investigated the structure function of the omega-nucleon interaction by the use of a mesonic picture at low and medium momentum transfer and a quantum-chromodynamical (QCD) description at high momentum transfer. The results are compared with recent calculations for ?- and rho-nucleon interaction form factors in the same model. (orig.)

1984-03-01

4

Measurements of the nucleon structure function F_2 on iron  

International Nuclear Information System (INIS)

The nucleon structure function F_2 has been measured by the European Muon Collaboration at four different energies using an iron scintillator target. Preliminary data are presented for beam energies of 250 and 280 GeV

1980-03-21

5

Towards a lattice calculation of the nucleon structure functions  

International Nuclear Information System (INIS)

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

1995-04-01

6

Towards a lattice calculation of the nucleon structure functions  

CERN Document Server

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

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

1994-01-01

7

Phenomenological study of the nucleon structure functions; Etude phenomenologique des fonctions de structure du nucleon  

Energy Technology Data Exchange (ETDEWEB)

This thesis is devoted to the study of the deep inelastic scattering. Its purpose is the development of phenomenological models describing experimental results on unpolarized (F{sub 2}) and polarized (g{sub 1}) nucleon structure functions in the wide range of the kinematical domain. Special attention is paid to the small-x behaviour of F{sub 2} and to the link between deep inelastic scattering and photoproduction process. The investigation of the Pomeron in deep inelastic scattering shows that one single Pomeron compatible with the Froissard-Martin limit can account for all the present HERA data. A phenomenological model of the proton structure function is developed, based on a two-component structure including various features expected from both perturbative quantum chromodynamics and non perturbative Regge theory. A link with the photoproduction process is provided. A detailed analysis of the perturbative components, based on the Gribov-Lipatov-Altarelli-Parisi evolution equations is presented. Taking into account the different parton distribution, this approach allows to describe data on proton and neutron structure functions, on deep inelastic neutrino scattering, and to reproduce the gluons distribution extracted by the ZEUS collaboration. The model is applied to the polarized deep inelastic scattering and the axial anomaly effect appearing both in the description of results on the spin dependent structure functions g{sup p,n,d} and in the interpretation of the nucleon spin structure is discussed. (J.S.). 260 refs., 34 figs., 8 tabs., 6 appends.

Bertini, M.

1995-05-12

8

Experimental study of structure functions of nucleons and nuclei  

International Nuclear Information System (INIS)

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

1981-09-15

9

Truncated Moment Analysis of Nucleon Structure Functions  

Energy Technology Data Exchange (ETDEWEB)

We employ a novel new approach using "truncated" moments, or integrals of structure functions over restricted regions of x, to study local quark-hadron duality, and the degree to which individual resonance regions are dominated by leading twists. Because truncated moments obey the same Q^2 evolution equations as the leading twist parton distributions, this approach makes possible for the first time a description of resonance region data and the phenomenon of quark-hadron duality directly from QCD.

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

2007-11-16

10

A model for nucleon, pion and kaon structure functions  

International Nuclear Information System (INIS)

The hypothesis that, in the leading twist approximation and to all orders of perturbative QCD, there exists a momentum scale Q"2_0 at which hadrons are pure valence quark (or antiquark) bound states leads to definite predictions on their structure functions. Predictions are made here using a non-relativistic approximation for the bound states. Good agreement with experiment is found for nucleon, pion and kaon structure functions

1980-03-21

11

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 Q"2 and energy transfer ?, i.e. in the region of the nucleon resonances are discussed. Experiments to measure A_1"p, A_2"p and A_1"1"n structure functions at CEBAF in a Q"2 range from 0.15 to 2.0 GeV"2, and a W range from threshold to 2.2 GeV are presented

1994-01-05

12

Nucleon g2 Structure Function and Quark-Gluon Correlations  

International Nuclear Information System (INIS)

We discuss two recently carried out experiments at Jefferson Lab that measured with precision the spin structure function of the nucleon g2, aiming at the determination of the twist-3 matrix element known as d2 for both the proton and the neutron. This matrix element is related to the average Lorentz color force that a quark experiences just at the instant it is struck. It is also interpreted as a measurement of a linear combination of the electric and magnetic 'color polarizability' in the nucleon.

2009-12-17

13

Sum Rules and Moments of the Nucleon Spin Structure Functions  

CERN Document Server

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

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

2005-01-01

14

Nuclear effects in F_3 structure function of nucleon  

CERN Multimedia

We study nuclear effects in the $F^A_3(x)$ structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio $R(x,Q^2)=\\frac{F^A_3(x,Q^2)}{AF^N_3(x, Q^2)}$ and the Gross-Llewellyn Smith(GLS) integral $G(x,Q^2)=\\int_x^1 dx F^A_3(x,Q^2)$ in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data.

Athar, M Sajjad; Vacas, M J Vicente

2007-01-01

15

Nuclear effects in F3 structure function of nucleon  

International Nuclear Information System (INIS)

We study nuclear effects in the F3A(x) structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio R(x,Q2)=(F3A(x,Q2))/(AF3N(x,Q2)) and the Gross-Llewellyn Smith (GLS) integral G(x,Q2)=?x1dxF3A(x,Q2) in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data

2008-10-02

16

Sum Rules and Moments of the Nucleon Spin Structure Functions  

Energy Technology Data Exchange (ETDEWEB)

The nucleon has been used as a laboratory to investigate its own spin structure and Quantum Chromodynamics. New experimental data on nucleon spin structure at low to intermediate momentum transfers combined with existing high momentum transfer data offer a comprehensive picture of the transition region from the confinement regime of the theory to its asymptotic freedom regime. Insight for some aspects of the theory is gained by exploring lower moments of spin structure functions and their corresponding sum rules (i.e. the Gerasimov-Drell-Hearn, Bjorken and Burkhardt-Cottingham). These moments are expressed in terms of an operator product expansion using quark and gluon degrees of freedom at moderately large momentum transfers. The sum rules are verified to a good accuracy assuming that no singular behavior of the structure functions is present at very high excitation energies. The higher twist contributions have been examined through the moments evolution as the momentum transfer varies from higher to lower values. Furthermore, QCD-inspired low energy effective theories, which explicitly include chiral symmetry breaking, are tested at low momentum transfers. The validity of these theories is further examined as the momentum transfer increases to moderate values. It is found that chiral perturbation calculations agree reasonably well with the first moment of the spin structure function g{sub 1} at momentum transfer of 0.1 GeV{sup 2} but fail to reproduce the neutron data in the case of the generalized polarizability {delta}{sub LT}.

Jian-Ping Chen; Alexandre Deur; Zein-Eddine Meziani

2005-08-01

17

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.)

1993-02-01

18

QCD, the Parton Model, and the Nucleon Polarised Structure Functions}  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present talk summarises the 1993 situation in understanding the spin structure of the nucleon via electron and muon polarised deep--inelastic scattering (PDIS). The central question I shall address here is if the data can be interpreted as evidence for polarisation in the ``strange'' nucleon ``sea'', and I conclude that they can not: incidentally, I also find that they can not be constructed as evidence for violation of perturbative QCD (PQCD), either. Talk presented a...

Gensini, Paolo M.

1993-01-01

19

Neutrinos and nucleon structure  

International Nuclear Information System (INIS)

The study of neutrino interactions in matter is yielding a wealth of information on the form factors and structure functions of the nucleon. These data allow tests of models of nucleon structure and of dynamical theories of quarks and gluons. We attempt a critical appraisal of recent facts and their impact on our theoretical understanding. (orig.)

1979-07-04

20

Detailed Measurements of Structure Functions from Nucleons and Nuclei  

CERN Multimedia

The experiment will study deep inelastic muon nucleon scattering in a wide range of Q|2~(1-200 (GeV/c)|2) and x~(0.005-0.75). The main aims of the experiment are: \\item a)~~~~Detailed measurements of the nuclear dependence of the structure function F^2|A, of R~=~@s^L/@s^T and of the cross-section for J/@y production. They will provide a basis for the understanding of the EMC effect: the modification of quark and gluon distributions due to the nuclear environment. \\item b)~~~~A simultaneous high luminosity measurement of the structure function F^2 on hydrogen and deuterium. This will provide substantially improved accuracy in the knowledge of the neutron structure function F^2|n, of F^2|p-F^2|n and F^2|n/F^2|p and their Q|2 dependence. Furthermore, the data will allow a determination of the strong coupling constant @a^s(Q|2) with reduced experimental and theoretical uncertainties as well as of the ratio of the down to up quark distributions in the valence region. Due to the large x range covered by the experim...

2002-01-01

 
 
 
 
21

QCD, the parton model, and the nucleon polarised structure functions  

CERN Multimedia

The present talk summarises the 1993 situation in understanding the spin structure of the nucleon via electron and muon polarised deep-inelastic scattering (PDIS). The central question I shall address here is if the data can be interpreted as evidence for polarisation in the "strange" nucleon "sea", and I conclude that they can not: incidentally, I also find that they can not be constructed as evidence for violation of perturbative QCD (PQCD), either. Talk presented at "Quinto Convegno su Problemi di Fisica Nucleare Teorica", Cortona (Arezzo, Italy), October 1993. To be published in the proceedings: "Perspectives on Theoretical Nuclear Physics (V)", L. Bracci, et al., eds. (ETS Ed., Pisa 1994)

Gensini, P M

1993-01-01

22

Resonance contribution to nucleon structure functions and quark-hadron duality  

International Nuclear Information System (INIS)

The recent measurement of quark-hadron duality by Jefferson Lab. is shortly reviewed. Then, we employ simple constituent quark model to estimate nucleon structure functions in the resonance region. By comparing with moments of the scaling structure functions given by Quantum chromodynamics (QCD) calculations or parameterizations in deep inelastic scattering region, we study the occurrence of Bloom-Gilman quark-hadron duality for the nucleon structure functions F2 or g1. Local duality in elastic region is also analyzed. (author)

2004-03-07

23

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/cm"2 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 F_2(x,Q"2) with a typical precision of 2% over the range 5 < Q"2 < 200 GeV"2/c"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 ?/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

1983-01-01

24

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 to carried out in order to study the x-dependence (where x is the Bjorken variable) of nucleon structure functions and their ratios over a range of squared four-momentum transfers 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 would provide new information for detailed studies of the EMC effect and tests of many models explaining the x behaviour of the nucleon structure functions and their ratios. The measurements will be decisive for the proof that a quark-parton model of the nucleus describes adequately nuclear structure probed at high energies. The upgraded high luminosity spectrometer with improved resolution in transferred energy will be used for the measurements

1985-01-01

25

Target Mass Correction for the Polarized Nucleon Structure Function  

International Nuclear Information System (INIS)

We use the phenomenological valon model to extract polarized parton densities and polarized proton structure function. Since the analytical result at large values of x and low values of Q2 is not in good agreement with available experimental data, we employ target mass correction to increase the reliability of the calculations. New comparison confirms a better agreement with the experimental data. (author)

2009-11-01

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

2006-07-01

27

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

28

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 F"2sup(N)(Fe)/F"2sup(N)(D) is presented. The observed x-dependence of this ratio is in disagreement with existing theoretical predictions. (orig.)

1983-03-31

29

Structure functions of pion and nucleon determined from high mass muon pair production  

International Nuclear Information System (INIS)

Structure functions of quark distribution in nucleon and pion are estimated from the shape of double differential cross section measured in the proton-platinum reaction at 400 GeV/c and in the negative pion-tungsten reaction at 194 GeV/c

1985-01-01

30

Higher-twist corrections to nucleon structure functions from lattice QCD  

International Nuclear Information System (INIS)

A genuinely non-perturbative evaluation of higher-twist contributions to the structure functions of the nucleon, with all mixing effects and renormalon ambiguities taken care of, is presented. Higher-twist corrections turn out to be significant at moderate values of q2

1999-10-01

31

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

Energy Technology Data Exchange (ETDEWEB)

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 g{sub 1,2} are discussed. It is found that the corrections play a sizeable role to the contribution of the twist-3 d-tilde{sub 2} extracted from the Cornwall-Norton moments.

Dong, Y.B. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)], E-mail: dongyb@mail.ihep.ac.cn

2007-09-13

32

Nucleon g-2 Structure Function at Large x and Quark-Gluons Correlations  

International Nuclear Information System (INIS)

We discuss two recently carried out experiments at Jefferson Lab that measured with precision the spin structure function of the nucleon g2, aiming at the determination of the twist-3 matrix element known as d2 for both the proton and the neutron. This matrix element is related to the average Lorentz color force that a quark experiences just at the instant it is struck. It is also interpreted as a measurement of a linear combination of the electric and magnetic 'color polarizability' in the nucleon.

2009-05-26

33

Nucleon $g-2$ Structure Function at Large $x$ and Quark-Gluons Correlations  

Energy Technology Data Exchange (ETDEWEB)

We discuss two recently carried out experiments at Jefferson Lab that measured with precision the spin structure function of the nucleon g2, aiming at the determination of the twist-3 matrix element known as d2 for both the proton and the neutron. This matrix element is related to the average Lorentz color force that a quark experiences just at the instant it is struck. It is also interpreted as a measurement of a linear combination of the electric and magnetic “color polarizability” in the nucleon.

Zein-Eddine Meziani

2009-12-01

34

Nucleon spin structure  

International Nuclear Information System (INIS)

A simple introduction of the discovery of quark and the constituent quark model of nucleon have been given. The contradiction between the quark spin structure of nucleon of the constituent quark model and the measured one in the polarized deep inelastic lepton-nucleon scattering has been explained in detail. It is elucidated that the so-called 'proton spin crisis' is due to quark spin confusion. The incompatibility between the requirement of gauge invariance and canonical quantization for the orbital angular momentum operator of a quark in a nucleon or an electron in an atom has been discussed

2000-03-01

35

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-09-29

36

A Lattice Evaluation of the Deep-Inelastic Structure Functions of the Nucleon  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The lower moments of the unpolarized and polarized deep-inelastic structure functions of the nucleon are calculated on the lattice. The calculation is done with Wilson fermions and for three values of the hopping parameter $\\kappa$, so that we can perform the extrapolation to the chiral limit. Particular emphasis is put on the renormalization of lattice operators. The renormalization constants, which lead us from lattice to continuum operators, are computed perturbatively to...

Go?ckeler, M.; Horsley, R.; Ilgenfritz, E. -m; Oelrich, H.; Perlt, H.; Rakow, P.; Schierholz, G.; Schiller, A.

1995-01-01

37

Structure function measurements in the deep inelastic muon-nucleon scattering  

International Nuclear Information System (INIS)

Measurements of deep inelastic scattering events on a combined copper and deuterium target were performed by the European Muon Collaboration (EMC) using a muon beam at CERN's SPS with energies at 100 GeV and 280 GeV. The data are analysed and compared with a detailed Monte-Carlo simulation and allow the determination of structure functions from both targets. In the light of the present discrepancy between EMC's and BCDMS's structure functions, stringend cuts were applied to the data. The results confirm the EMC structure function measurements on unbound nucleons. The comparison between the copper structure function from this experiment and the NA2 iron structure function shows a trend to lower values at low xBj. (orig.)

1990-01-01

38

Comparison of nucleon structure functions in bubble chamber neutrino experiments with QCD predictions  

International Nuclear Information System (INIS)

Results are presented for nucleon structure functions in the range 0.1 1.5 GeV"2 one obtains ?sub(anti Manti S) = 0.22 +- 0.04 GeV. An attempt was made to fit a simple higher twist parametrisation and a combination of QCD and higher twist to the moments. From a fit to the structure functions values are obtained of ?sub(LO) = 0.23 +- 0.08 GeV in good agreement with the fit to the moments. (orig.)

1982-08-23

39

Spin structure functions of the nucleon at low Q{sup 2} and {nu}  

Energy Technology Data Exchange (ETDEWEB)

Phenomenological approaches to describe the spin structure functions an spin sum rules for proton and neutrons at low momentum transfer Q{sup 2} and energy transfer {nu}, i.e. in the region of the nucleon resonances are discussed. Experiments to measure A{sub 1}{sup p}, A{sub 2}{sup p} and N{sub 1}{sup n} structure functions at CEBAF in a Q{sup 2} range from 0.15 to 2.0 GeV{sup 2}, and a W range from threshold to 2.2 GeV are presented.

Burkert, V.D.

1993-06-30

40

Spin structure functions of the nucleon at low Q"2 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 Q"2 and energy transfer ?, i.e. in the region of the nucleon resonances are discussed. Experiments to measure A_1"p, A_2"p and N_1"n structure functions at CEBAF in a Q"2 range from 0.15 to 2.0 GeV"2, and a W range from threshold to 2.2 GeV are presented

1993-05-17

 
 
 
 
41

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

CERN Document Server

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

Rinat, A S

2006-01-01

42

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

International Nuclear Information System (INIS)

The chi and Q"2 dependences of the nucleon structure functions F_2sup(N)(chi,Q"2) and Rsup(N)(chi,Q"2) have been measured in deep inelastic muon scattering from an iron target in the region 0.04< chi<0.7 and 3.5< Q"2<220 GeV"2. 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 Q"2proportional15 GeV"2. (orig./HSI)

1986-07-14

43

Nucleon form factors and structure functions from Nf = 2 clover fermions  

CERN Multimedia

We give an update on our ongoing efforts to compute the nucleon's form factors and moments of structure functions using Nf=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 will 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.

Collins, S; Hägler, Ph; Hemmert, T; Horsley, R; Nakamura, Y; Nobile, A; Perlt, H; Pleiter, D; Rakow, P E L; Schäfer, A; Schierholz, G; Sternbeck, A; Stüben, H; Winter, F; Zanotti, J M

2010-01-01

44

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.)

1991-01-01

45

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

46

Strangeness content and structure function of the nucleon in a statistical quark model  

CERN Multimedia

The strangeness content of the nucleon is determined from a statistical model using confined quark levels, and is shown to have a good agreement with the corresponding values extracted from experimental data. The quark levels are generated in a Dirac equation that uses a linear confining potential (scalar plus vector). With the requirement that the result for the Gottfried sum rule violation, given by the new muon collaboration (NMC), is well reproduced, we also obtain the difference between the structure functions of the proton and neutron, and the corresponding sea quark contributions. (27 refs).

Trevisan, L A; Tomio, L

1999-01-01

47

Progress towards a lattice determination of (moments of) nucleon structure functions  

International Nuclear Information System (INIS)

Using unimproved and non-perturbatively O(a) improved Wilson fermions, results are given for the three lowest moments of unpolarised nucleon structure functions. Renormalisation, chiral extrapolation and the continuum limit of the matrix elements are briefly discussed. The simulations are performed for both quenched and two flavours of unquenched fermions. No obvious sign of deviation from linearity in the chiral extrapolations are found. (This is most clearly seen in our quenched unimproved data, which extends to lighter quark mass.) Possible quenching effects also seem to be small. The lowest moment thus remains too large, so it seems to be necessary to reach smaller quark masses in numerical simulations

2002-03-01

48

Progress towards a lattice determination of (moments of) nucleon structure functions  

International Nuclear Information System (INIS)

Using unimproved and non-perturbatively O(a) improved Wilson fermions, results are given for the three lowest moments of unpolarised nucleon structure functions. Renormalisation, chiral extrapolation and the continuum limit of the matrix elements are briefly discussed. The simulations are performed for both quenched and two flavours of unquenched fermions. No obvious sign of deviation from linearity in the chiral extrapolations are found. (This is most clearly seen in our quenched unimproved data, which extends to lighter quark mass). Possible quenching effects also seem to be small. The lowest moment thus remains too large, so it seems to be necessary to reach smaller quark masses in numerical simulations. (orig.)

2001-01-01

49

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 Q"2 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

1992-01-01

50

Analysis of nucleon structure functions in CERN bubble chamber neutrino experiments  

International Nuclear Information System (INIS)

The authors present results for the differential cross sections of neutrinos and antineutrinos on nucleons in the energy range E=2-200 GeV, from the BEBC and Gargamelle experiments. The structure functions F2,2xF1 and xF3 have been evaluated as a function of x and q2. Deviations are observed from Bjorken scaling, which are very similar to those found in electron and muon inelastic scattering. For the Callan-Gross ratio, the authors find 2xF1/F2=0.80+-0.12 and the corresponding value for ==0.15+-0.10. The results are consistent with the Gross-Llewellyn-Smith sum rule; the authors measure >=2.5+-0.5 valence quarks per nucleon. Quark and antiquark distributions are given. The Nachtmann moments of F2 and xF3 are quantitatively consistent with the predictions from QCD. The value of the strong interaction parameter is ?=0.74+-0.05 GeV without corrections, and 0.66+-0.05 GeV including ?2sub(s) corrections. The moments of the gluon distribution are found to be positive and indicate an x distribution of gluons which is comparable with that of the valence quarks. (Auth.)

1978-09-18

51

Nuclear effects in F{sub 3} structure function of nucleon  

Energy Technology Data Exchange (ETDEWEB)

We study nuclear effects in the F{sub 3}{sup A}(x) structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio R(x,Q{sup 2})=(F{sub 3}{sup A}(x,Q{sup 2}))/(AF{sub 3}{sup N}(x,Q{sup 2})) and the Gross-Llewellyn Smith (GLS) integral G(x,Q{sup 2})={integral}{sub x}{sup 1}dxF{sub 3}{sup A}(x,Q{sup 2}) in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data.

Athar, M. Sajjad [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India)], E-mail: sajathar@rediffmail.com; Singh, S.K. [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India); Vacas, M.J. Vicente [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, 46100 Burjassot (Valencia) (Spain)

2008-10-02

52

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

International Nuclear Information System (INIS)

The so called open-quotes EMC effectclose 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 xb, where shadowing effects appear. In the region of valence quarks and nuclear effects (xb > 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 F2(xb, Q2) and Rlt(xb,Q2) = ?l/?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 3He and 48Ca, would be of great interest. The intermediate scaling region (0.1 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

1994-04-01

53

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

54

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

International Nuclear Information System (INIS)

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. (physics of elementary particles and fields)

2013-02-15

55

Nucleon-nucleon interaction from meson exchange and nucleonic structure  

International Nuclear Information System (INIS)

We discuss the physics of the Bochum NN potential (Ruhrpot). In contrast to conventional one-boson-exchange models (OBE) we calculate the potential within two phases which are (i) meson exchanges at long distances and (ii) direct NN interactions, coming from the intrinsic nucleon structure, at short distances. The interaction vertices are calculated in a self-consistent way. The most important resonant two- and three-? correlations are included. As the meson exchange is negligible at high Q2 we have several advantages: (i) resonable meson scales, (ii) SU(6) limit for vector mesons, (iii) perturbative QCD asymptotic, (iv) no need for ? mesons, and (v) very good description of the nucleon-nucleon data

1994-05-01

56

Axial structure of the nucleon  

CERN Multimedia

We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.

Bernard, V; Meißner, Ulf G; Elouadrhiri, Latifa; Mei{\\ss}ner, Ulf-G.

2002-01-01

57

Axial structure of the nucleon  

International Nuclear Information System (INIS)

We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton. (author)

2002-01-01

58

Axial structure of the nucleon  

International Nuclear Information System (INIS)

We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton

2002-01-01

59

Nucleon structure using lattice QCD  

Energy Technology Data Exchange (ETDEWEB)

A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.

Alexandrou, C.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Constantinou, M.; Hatziyiannakou, K. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Drach, V. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Jansen, K. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Koutsou, G.; Vaquero, A. [The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Leontiou, T. [Frederick Univ, Nicosia (Cyprus). General Dept.

2013-03-15

60

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

 
 
 
 
61

Feasibility of a high precision measurement of nucleon structure functions at LEP  

International Nuclear Information System (INIS)

Recently, the scaling violation analysis of deep inelastic scattering data has proven to be the most direct and powerful method to test QCD and measure ?MS. The feasibility of a deep inelastic scattering experiment for a high precision measurement of the nucleon structure functions F2 in the Q2 region 2 to 80 GeV2 with the LEP electron beam incident on internal hydrogen and deuterium gas jet targets is investigated. The features which allow a high absolute precision are the precise calibration of the LEP beam energy, a point-like target, a luminosity monitor based on Moeller scattering, instantaneous luminosity higher than 4x1031 cm-2s-1 with 8 LEP bunches and a 50% acceptance which will allow us to reach a luminosity of 1038 cm-2 in a year. Using in parasitic mode the LEP electron beam at the energies of 46 GeV (Z-pole), 80 GeV (W pair production threshold) and 120 GeV (possible future improvement of LEP2000?) the structure functions F-pp and F2n could be measured with a precision of 1% over the x range 0.05 to 0.75. The corresponding precision on ?MS has been estimated at the level of 10 MeV, both statistical and systematic. (author) 20 figs., 4 tabs., 39 refs

1992-01-01

62

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.

2010-07-01

63

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

64

Nucleon Structure from Lattice QCD  

Energy Technology Data Exchange (ETDEWEB)

Recent advances in lattice field theory, in computer technology and in chiral perturbation theory have enabled lattice QCD to emerge as a powerful quantitative tool in understanding hadron structure. I describe recent progress in the computation of the nucleon form factors and moments of parton distribution functions, before proceeding to describe lattice studies of the Generalized Parton Distributions (GPDs). In particular, I show how lattice studies of GPDs contribute to building a three-dimensional picture of the proton, I conclude by describing the prospects for studying the structure of resonances from lattice QCD.

David Richards

2007-09-05

65

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

66

Feasibility of a high precision measurement of nucleon structure functions at LEP  

Energy Technology Data Exchange (ETDEWEB)

Recently, the scaling violation analysis of deep inelastic scattering data has proven to be the most direct and powerful method to test QCD and measure {Lambda}{sub MS}. The feasibility of a deep inelastic scattering experiment for a high precision measurement of the nucleon structure functions F{sub 2} in the Q{sup 2} region 2 to 80 GeV{sup 2} with the LEP electron beam incident on internal hydrogen and deuterium gas jet targets is investigated. The features which allow a high absolute precision are the precise calibration of the LEP beam energy, a point-like target, a luminosity monitor based on Moeller scattering, instantaneous luminosity higher than 4x10{sup 31} cm{sup -2}s{sup -1} with 8 LEP bunches and a 50% acceptance which will allow us to reach a luminosity of 10{sup 38} cm{sup -2} in a year. Using in parasitic mode the LEP electron beam at the energies of 46 GeV (Z-pole), 80 GeV (W pair production threshold) and 120 GeV (possible future improvement of LEP2000?) the structure functions F-p{sup p} and F{sub 2}{sup n} could be measured with a precision of 1% over the x range 0.05 to 0.75. The corresponding precision on {Lambda}{sub MS} has been estimated at the level of 10 MeV, both statistical and systematic. (author) 20 figs., 4 tabs., 39 refs.

Galumian, P.; Joseph, C.; Perroud, J.P.; Tran, M.T.; Werlen, M. [Lausanne Univ. (Switzerland). Inst. de Physique Nucleaire

1992-05-01

67

Feasibility of a high precision measurement of nucleon structure functions at LEP  

Energy Technology Data Exchange (ETDEWEB)

Recently, the scaling violation analysis of deep inelastic scattering data has proven to be the most direct and powerful method to test QCD and measure [Lambda][sub MS]. The feasibility of a deep inelastic scattering experiment for a high precision measurement of the nucleon structure functions F[sub 2] in the Q[sup 2] region 2 to 80 GeV[sup 2] with the LEP electron beam incident on internal hydrogen and deuterium gas jet targets is investigated. The features which allow a high absolute precision are the precise calibration of the LEP beam energy, a point-like target, a luminosity monitor based on Moeller scattering, instantaneous luminosity higher than 4x10[sup 31] cm[sup -2]s[sup -1] with 8 LEP bunches and a 50% acceptance which will allow us to reach a luminosity of 10[sup 38] cm[sup -2] in a year. Using in parasitic mode the LEP electron beam at the energies of 46 GeV (Z-pole), 80 GeV (W pair production threshold) and 120 GeV (possible future improvement of LEP2000 ) the structure functions F-p[sup p] and F[sub 2][sup n] could be measured with a precision of 1% over the x range 0.05 to 0.75. The corresponding precision on [Lambda][sub MS] has been estimated at the level of 10 MeV, both statistical and systematic. (author) 20 figs., 4 tabs., 39 refs.

Galumian, P.; Joseph, C.; Perroud, J.P.; Tran, M.T.; Werlen, M. (Lausanne Univ. (Switzerland). Inst. de Physique Nucleaire)

1992-05-01

68

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

69

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

70

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

CERN Document Server

We present analyses on nucleon structure functions at the small Bjorken-$x$ in the framework of holographic QCD. In this study, we improve the description of the target nucleon in the current setup of the holographic model by introducing a soft-wall AdS/QCD model, in which the AdS geometry is smoothly cut off at IR. Combining the improved Pomeron-nucleon coupling and the wave function of the 5D U(1) vector field with the BPST Pomeron exchange kernel, then we obtain the structure functions. Here we focus on the nonperturbative kinematical region, where $10^{-6} \\leq x \\leq 10^{-2}$ and $0.1 \\leq Q^2 \\leq 10$ [GeV$^2$], and show that our calculations for $F_2^p$ and $F_L^p$ are consistent with experimental data of the deep inelastic scattering at HERA. Furthermore, we find that the resulting longitudinal-to-transverse ratio of the structure functions, $F_L^p/F_T^p$, depends on both of $x$ and $Q^2$.

Watanabe, Akira

2013-01-01

71

Prediction for the ultrahigh energy neutrino-nucleon cross section from new structure function data at small x  

International Nuclear Information System (INIS)

New structure function data at small Bjorken x from HERA are used along with next-to-leading order QCD evolution to predict a cross section for charged-current interactions of ultrahigh energy neutrinos with nucleons. This new result is over twice the size of previous estimates and has important implications for cosmic ray experiments now underway as well as for KM3 arrays (cubic kilometer-scale neutrino telescopes) now in the planning stages

1995-02-27

72

Probing nuclear structure with nucleons  

International Nuclear Information System (INIS)

The goal of this lecture is to show how nucleon scattering can be used to probe the structure of target nuclei, and how nucleon scattering observables can be interpreted in terms of nuclear structure using microscopic optical potentials. After a brief overview of the specificities of nucleon-nucleus scattering, and a quick reminder on scattering theory, the main part of this lecture is devoted to the construction of optical potentials in which the target nuclei structure information is folded with an effective interaction. Several examples of such microscopic optical model potentials are given. (author)

2007-09-17

73

Overview of nucleon structure  

CERN Document Server

The quark-gluon properties of the nucleon are probed by a host of recent and planned experiments. These involve elastic, deep-inelastic, semi-inclusive deep-inelastic (SIDIS), and deeply-virtual Compton scattering. A light-front description is naturally applied to interpret all of these processes. The advantages of this approach will be discussed The talk will then focus on the transverse charge and magnetization densities of the nucleons and the use of SIDIS to reveal the non-spherical shape of the nucleon. We find that the central charge density of the neutron is negative, that the magnetization density of the proton extends further in space than the charge distribution, and that the shape of the nucleon, as measured by the spin-dependent density, is not spherical.

Miller, Gerald A

2010-01-01

74

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 Q_2 dependence of the structure functions F"2 and xF"3 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"+_7_0sub(-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 xF"3, F"2, anti q structure functions gives a more reliable determination of the gluon distribution in the nucleon. (orig.)

1983-03-31

75

Overview of nucleon structure studies  

Energy Technology Data Exchange (ETDEWEB)

A brief overview of the recent activity in the measurement of the elastic electromagnetic proton and neutron form factors is presented. It is discussed how the quality of the data has been greatly improved by performing double polarization experiments, and the role of two-photon exchange processes will be highlighted. The spatial information on the quark charge distribibutions in the nucleon resulting from the form factors measurements will be discussed, as well as the steady rate of improvements made in the lattice QCD calculations. It is discussed how generalized parton distributions have emerged as a unifying theme in hadron physics linking the spatial densities extracted from form factors with the quark momentum distribution information residing in quark structure functions. The recent progress in the electromagnetic excitation of the $\\Delta(1232)$ resonance will also briefly be discussed.

Marc Vanderhaeghen

2007-06-08

76

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.)

2009-01-01

77

Measurement of R = ?L/?T and the Separated Longitudinal and Transverse Structure Functions in the Nucleon Resonance Region  

International Nuclear Information System (INIS)

We report on a detailed study of longitudinal strength in the nucleon resonance region, presenting new results from inclusive electron-proton cross sections measured at Jefferson Lab Hall C in the four-momentum transfer range 0.2 2 2. The data have been used to accurately perform over 170 Rosenbluth-type longitudinal/transverse separations. The precision R ?L/?T data are presented here, along with the first separate values of the inelastic structure functions F1 and FL in this regime. The resonance longitudinal component is found to be significant. With the new data, quark-hadron duality is observed above Q2 = 1 GeV2 in the separated structure functions independently

2004-01-01

78

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.

2010-03-01

79

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

CERN Document Server

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.

Bartels, Jochen; Motyka, Leszek

2009-01-01

80

Spin Structure of the Nucleon  

International Nuclear Information System (INIS)

HERMES is a second generation experiment to study the spin structure of the nucleon, in which measurements of the spin dependent properties of semi-inclusive deep-inelastic lepton scattering are emphasized. The first experimental results from measurements of single-spin asymmetries for pions and kaons in deep-inelastic scattering with transverse target polarization are discussed. Longitudinally polarized beam and target data provide information on the flavor decomposition of the polarized quark distributions in the nucleon and a first glimpse of the gluon polarization. Moreover, first preliminary results for the unpolarized ep ? en? + total cross section are presented and compared to Generalized Parton Distribution calculations

2006-02-01

 
 
 
 
81

Constituent quark description of nucleon structure  

International Nuclear Information System (INIS)

Nucleon structure functions are calculated within the constituent quark in the leading order. The results compare well with the experimental data for entire range of kinematics in x and Q2and with the next - to - leading order calculation of GRV

1998-09-01

82

New relations in lepton-nucleon scattering independent of the nucleon structure  

International Nuclear Information System (INIS)

New relations in deep inelastic and (quasi-)elastic scattering of polarized electrons and positrons (?"±-mesons) on non-polarized nucleons have been obtained. They connect cross sections with standard model parameters and are independent of the structure functions and form factors of the nucleon. A well known example is the Paschos-Wolfenstein relation in (?-bar)N-scattering. 6 refs

1989-01-01

83

Nucleon spin structure at very high x  

Energy Technology Data Exchange (ETDEWEB)

Dyson–Schwinger equation treatments of the strong interaction show that the presence and importance of nonpointlike diquark correlations within the nucleon are a natural consequence of dynamical chiral symmetry breaking. Using this foundation, we deduce a collection of simple formulae, expressed in terms of diquark appearance and mixing probabilities, from which one may compute ratios of longitudinal-spin-dependent u- and d-quark parton distribution functions on the domain x?1. A comparison with predictions from other approaches plus a consideration of extant and planned experiments shows that the measurement of nucleon longitudinal spin asymmetries on x?1 can add considerably to our capacity for discriminating between contemporary pictures of nucleon structure.

Roberts, Craig D.; Holt, Roy J. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Schmidt, Sebastian M. [Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich (Germany)

2013-11-25

84

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

85

Quark-hadron duality and truncated moments of nucleon structure functions  

CERN Multimedia

We employ a novel new approach to study local quark-hadron duality using "truncated" moments, or integrals of structure functions over restricted regions of x, to determine the degree to which individual resonance regions are dominated by leading twist. Because truncated moments obey the same Q^2 evolution equations as the leading twist parton distributions, this approach makes possible for the first time a description of resonance region data and the phenomenon of quark-hadron duality directly from QCD.

Psaker, A; Christy, M E; Keppel, C

2008-01-01

86

Nucleon internal structure: a new set of quark, gluon momentum, angular momentum operators and parton distribution functions  

International Nuclear Information System (INIS)

It is unavoidable to deal with the quark and gluon momentum and angular momentum contributions to the nucleon momentum and spin in the study of nucleon internal structure. However we never have the quark and gluon momentum, orbital angular momentum and gluon spin operators which satisfy both the gauge invariance and the canonical momentum and angular momentum commutation relation. The conflicts between the gauge invariance and canonical quantization requirement of these operators are discussed. A new set of quark and gluon momentum, orbital angular momentum and spin operators, which satisfy both the gauge invariance and canonical momentum and angular momentum commutation relation, are proposed. The key point to achieve such a proper decomposition is to separate the gauge field into the pure gauge and the gauge covariant parts. The same conflicts also exist in QED and quantum mechanics and have been solved in the same manner. The impacts of this new decomposition to the nucleon internal structure are discussed. (authors)

2009-12-01

87

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.)

1985-01-01

88

Nucleon Spin Structure Functions g1 and g2 from Polarized Inclusive Scattering  

International Nuclear Information System (INIS)

This paper will present a survey of recent experimental results for the g1 and g2 spin structure functions. Over the past decade, these structure functions (and the virtual photon asymmetries A1 and A2) have been well-measured in the large-Q2 scaling region using inclusive polarized deep-inelastic scattering. New precision results from Jefferson Lab are now becoming available which cover kinematic regions that were previously poorly measured or completely unmeasured. Topics covered will include: recent experiments at Jefferson Lab which have made precise measurements of g1 in the resonance region for both proton and neutron to investigate the Q2 evolution of the GDH sum rule, a new measurement of A1 for the neutron in the large-x region where valence quark dynamics dominate, new precision results for g2 from Jefferson Lab, a review of the g1 results and NLO analyses in the scaling region for the SLAC, HERMES, and SMC data. Finally, a survey of results expected from several new experiments and longer-term experimental programs are discussed

2003-07-30

89

Flavor Structure of the Nucleon Sea  

CERN Document Server

The recent progress on our understanding of the flavor structure of unpolarized and polarized nucleon sea is reviewed. The large flavor asymmetry between the up and down sea quark distributions is now well established. This asymmetry strongly suggests the importance of the mesonic degrees of freedom in the description of the nucleon sea. The strong connection between the flavor structure and the spin structure of the nucleon sea is emphasized. Possible future measurements for testing various theoretical models are also discussed.

Peng, J C

2003-01-01

90

Flavor Structure of the Nucleon Sea  

CERN Document Server

We review the current status and future prospects on the subject of flavor structure of the nucleon sea. The flavor structure of the nucleon sea provides unique information on the non-perturbative aspects of strong interactions allowing stringent tests of various models on the partonic structures of the nucleons as well as lattice QCD calculations. The scope of this review covers the unpolarized, polarized, and the transverse-momentum dependent sea-quark distributions of the nucleons. While the main focus of this review is on the physics motivation and recent progress on the subject of nucleon sea, we also discuss future prospects of addressing some outstanding issues on the flavor structure of the nucleon sea.

Chang, Wen-Chen

2014-01-01

91

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

92

New Results on Nucleon Spin Structure  

Energy Technology Data Exchange (ETDEWEB)

Recent precision spin structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure in the valence quark (high-x) region and improved our understanding of higher-twist effects, spin sum rules and quark-hadron duality. First, results of a precision measurement of the neutron spin asymmetry, A{sub 1}{sup n}, in the high-x region are discussed. The new data shows clearly, for the first time, that A{sub 1}{sup n} becomes positive at high x. They provide crucial input for the global fits to world data to extract polarized parton distribution functions. Preliminary results on A{sub 1}{sup p} and A{sub 1}{sup d} in the high-x region have also become available. The up and down quark spin distributions in the nucleon were extracted. The results for {Delta}d/d disagree with the leading-order pQCD prediction assuming hadron helicity conservation. Then, results of a precision measurement of the g{sub 2}{sup n} structure function to study higher-twist effects are presented. The data show a clear deviation from the lead-twist contribution, indicating a significant higher-twist (twist-3 or higher) effect. The second moment of the spin structure functions and the twist-3 matrix element d{sub 2}{sup n} results were extracted at a high Q{sup 2} of 5 GeV{sup 2} from the measured A{sub 2}{sup n} in the high-x region in combination with existing world data and compared with a Lattice QCD calculation. Results for d{sub 2}{sup n} at low-to-intermediate Q{sup 2} from 0.1 to 0.9 GeV{sup 2} were also extracted from the JLab data. In the same Q{sup 2} range, the Q{sup 2} dependence of the moments of the nucleon spin structure functions was measured, providing a unique bridge linking the quark-gluon picture of the nucleon and the coherent hadronic picture. Sum rules and generalized forward spin polarizabilities were extracted and compared with Chiral Perturbation Theory calculations and phenomenological models. Finally, preliminary results on the resonance spin structure functions in the Q{sup 2} range from 1 to 4 GeV{sup 2} were presented, which, in combination with DIS data, will enable a detailed study of the quark-hadron duality in spin structure functions.

Jian-Ping Chen

2005-09-10

93

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 Q"2 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

1980-01-01

94

Nucleon-nucleon scattering in the functional quantum theory of the non-linear spinor field  

International Nuclear Information System (INIS)

The nucleon-nucleon and nucleon-antinucleon scattering cross sections are calculated in the frame of the functional quantum field theory by means of two different approximation methods: averaging by integration of indefinite integrals and pulse averaging. The results for nucleon-nucleon scattering are compared with experimental data, with calculations using a modified functional scalar product and with results in first order perturbation theory (V-A-coupling). As for elastic nucleon-antinucleon scattering, the S matrix is investigated for crossing symmetry. Scattering of 'nucleons' of different mass results in different cross sections even in the lowest-order approximation. (BJ)

1975-01-01

95

Three Nucleon Forces and Nuclear Structure  

Science.gov (United States)

The author's earlier research with Professor Bruce McKellar, some 30 years ago, led to the Tucson-Melbourne three-nucleon interaction, which is still relevant today. The new significance of three-nucleon forces in determining the structure of atomic nuclei will be discussed. This has led to increased efforts to learn more about the nature of these three-nucleon interactions, both experimentally and theoretically. The recently developed no-core shell model (NCSM) has the ability to test different theoretical models for three-nucleon forces by making direct comparisons of results produced by these forces with experimental data.

Barrett, B. R.

2007-10-01

96

Vertex functions of the nucleon. Pt. 1  

International Nuclear Information System (INIS)

The mesonic structure functions of the nucleon are calculated by a synthesis of a mesonic picture at low- and medium-momentum transfer and a quantum chromodynamical (QCD) description at high-momentum transfer. Coupled integral equations are derived for the form factors via an expansion in the known meson-baryon spectrum at low- and medium-momentum transfer. The equations have been solved self-consistently imposing the QCD constraints at asymptotic momentum transfer. An excellent approximation of the form factors is obtained through a parametrization. At momentum transfer q22/c2 the form factors are to a good approximation given by a monopole form, i.e. ?2->infinite with ?1approx.=1 GeV/c for ?NN, ?N? and ?1approx.=msub(rho) for rhoNN and rhoN? interactions. At high-momentum transfer q2>1 GeV2/c2 the form factors are strongly suppressed compared to the corresponding monopole forms. In this region of momentum transfer mNN differs from mN? (m=?,rho). The strong interaction radii of the nucleon are obtained to r0sup(?NN)=0.46 fm and r0sup(rhoNN)=0.6 fm for ?- and rho-interaction, respectively, indicating upper limits for possible bag radii. (orig./HSI)

1983-11-07

97

Studies of nucleon spin structure at HERMES  

International Nuclear Information System (INIS)

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

2000-10-17

98

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

1998-09-09

99

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

1986-01-01

100

Insight into nucleon structure from generalized parton distributions  

CERN Document Server

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; Dreher, P; Edwards, R; Fleming, G; Hagler, P; Lippert, T; Pochinsky, A V; Renner, D B; Richards, D; Schilling, K; Schroers, W; Hagler, Ph.; Lippert, Th.

2003-01-01

 
 
 
 
101

Axial and Vector Structure Functions for Electron- and Neutrino- Nucleon Scattering Cross Sections at all $Q^2$ using Effective Leading order Parton Distribution Functions  

CERN Multimedia

We construct a model for inelastic neutrino- and electron-nucleon scattering cross sections using effective leading order parton distribution functions with a new scaling variable $\\xi_w$. Non-perturbative effects are well described using the $\\xi_w$ scaling variable, in combination with multiplicative $K$ factors at low $Q^2$.Our model describes all inelastic charged lepton-nucleon scattering (including resonance) data (HERA/NMC/BCDMS/SLAC/JLab) ranging from very high $Q^2$ to very low $Q^2$ and down to the photo-production region. The model describes existing inelastic neutrino-nucleon scattering measurements, and has been developed to be used in analysis of neutrino oscillation experiments in the few GeV region.

Bodek, Arie

2010-01-01

102

Correlation functions, momentum distributions and clustering coefficients for three-nucleon nuclei  

International Nuclear Information System (INIS)

The precise study of structure of three-nucleon systems is carried out for different potentials of nucleon-nucleon interaction. The behaviour of pair correlation functions and momentum distributions is analysed for 3H and 3He nuclei, the cluster properties of these nuclei are also studied. The calculation of main parameters of three-nucleon systems is carried out using the representation without isospin and variational method with Gaussian bases

2009-01-01

103

Radial wave functions of valence nucleons  

International Nuclear Information System (INIS)

The potential for radial-shape determination of the atomic nucleus by the investigation of valence-nucleon wave functions using elastic electron scattering from the high-order multipole distribution of the nuclear magnetization density is examined. (U.K.)

1980-01-01

104

Nucleon resonances and spin structure  

Energy Technology Data Exchange (ETDEWEB)

The inclusive structure function g2 which is extracted from doubly polarized lepton scattering is relatively unknown. But due to its fundamental nature, knowledge of g2 is needed in a wide field of topics, ranging from understanding quark-gluon interactions in QCD confined systems, to calculations of energy levels in QED bound states. We discuss recent results on g2 from the JLab spin structure program and give a perspective on upcoming experiments.

Karl Slifer

2012-04-01

105

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

1992-06-01

106

Chiral symmetry and nucleon structure  

Energy Technology Data Exchange (ETDEWEB)

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.

Holstein, B.R. (Massachusetts Univ., Amherst, MA (United States). Dept. of Physics and Astromony Washington Univ., Seattle, WA (United States). Inst. for Nuclear Theory)

1992-01-01

107

Test of QCD and a measurement of ? from scaling violations in the nucleon structure function F2(x,Q2) at high Q2  

International Nuclear Information System (INIS)

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

1987-01-01

108

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

109

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

2014-02-01

110

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

2008-01-01

111

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

112

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

113

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

114

Spin structure of the nucleon and polarization  

International Nuclear Information System (INIS)

Recent experiments at CERN and SLAC have added new knowledge about the spin structure of the proton and the deuteron. A brief historical background is presented, the status of experiments is discussed, and progress in the understanding of the spin of the nucleon in the context of the quark parton model is summarized

1994-06-15

115

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

1993-01-01

116

Spin structure of the nucleon and polarization  

Energy Technology Data Exchange (ETDEWEB)

Recent experiments at CERN and SLAC have added new knowledge about the spin structure of the proton and the deuteron. A brief historical background is presented, the status of experiments is discussed, and progress in the understanding of the spin of the nucleon in the context of the quark parton model is summarized. (author) 6 refs.

Prescott, Ch.Y. [Stanford Univ., CA (United States). Stanford Linear Accelerator Center

1994-12-31

117

Spin structure of the nucleon and polarization  

Energy Technology Data Exchange (ETDEWEB)

Recent experiments at CERN and SLAC have added new knowledge about the spin structure of the proton and the deuteron. A brief historical background is presented, the status of experiments is discussed, and progress in the understanding of the spin of the nucleon in the context of the quark parton model is summarized.

Prescott, C.Y.

1994-09-01

118

Structure functions and structure function ratio F_2"n/F_2"p at small x_B_j and Q"2 in muon-nucleon scattering  

International Nuclear Information System (INIS)

Preliminary results on the measurement of the structure functions F_2"p(x_B_j, Q"2) and F_2"d(x_B_j, Q_2) and of the ratio F_2"n/F_2"p 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 x_B_j and Q"2 is examined in the kinematic range x_B_j > 8 x 10"-"4 and Q"2 > 0.2 GeV"2/c"2. The structure function ratio is presented as a function of x_B_j, for x_B_j > 10"-"6

1994-06-06

119

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

1996-09-01

120

The nucleon wave function in light-front dynamics  

CERN Document Server

The general spin structure of the relativistic nucleon wave function in the $3q$-model is found. It contains 16 spin components, in contrast to 8 ones known previously, since in a many-body system the parity conservation does not reduce the number of the components. The explicitly covariant form of the wave function automatically takes into account the relativistic spin rotations, without introducing any Melosh rotation matrices. It also reduces the calculations to the standard routine of the Dirac matrices and of the trace techniques. In examples of the proton magnetic moment and of the axial nucleon form factor, with a particular wave function, we reproduce the results of the standard approach. Calculations beyond the standard assumptions give different results.

Karmanov, V A

1998-01-01

 
 
 
 
121

The nucleon spin structure in a simple quark model  

CERN Multimedia

We investigate the spin structure of the nucleon in an extended Jaffe-Lipkin quark model. In addition to the conventional $3q$ structure, different $(3q)(Q\\bar{Q})$ admixtures in the nucleon wavefunction are also taken into account. The contributions to the nucleon spin from various components of the nucleon wavefunction are discussed. The effect due to the Melosh-Wigner rotation is also studied.

Ma, B Q; Yang Jian Jun; Ma, Bo-Qiang; Schmidt, Ivan; Yang, Jian-Jun

2000-01-01

122

Structure and spin of the nucleon  

Science.gov (United States)

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, H.

2014-03-01

123

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

124

Nucleon Structure and Generalized Parton Distributions  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses a selected part of the experimental program dedicated to the study of Generalized Parton Distributions, a recently introduced concept which provides a comprehensive framework for investigations of the partonic structure of the nucleon. Particular emphasis is put on the Deeply Virtual Compton Scattering program performed at the Jefferson Laboratory. The short and long term future of this program is also discussed in the context of the several experimental efforts aiming at a complete and exhaustive mapping of Generalized Parton Distributions.

Eric Voutier

2006-06-28

125

Nucleon structure as a background for determination of fundamental parameters  

International Nuclear Information System (INIS)

We consider deep inelastic, (quasi-) elastic lepton-nucleon scattering and investigate the possibilities of eliminating or suppressing theoretical uncertainties induced by nucleon structure in measuring the Standard Model parameters or in searching for new physics. On the basis of rather general hypothesis about nucleon structure we have obtained new relations between cross sections and neutral current parameters which are independent of the nucleon structure. We also investigate a dependence of the QCD ?-parameter extracted from the data on unknown large scale nucleon structure and propose a modification of the conventional QCD predictions which are weakly dependent of this uncertainty factor. (author). 9 refs, 1 tab

1992-01-01

126

Nucleon structure as a background for determination of fundamental parameters  

International Nuclear Information System (INIS)

We consider deep inelastic (quasi)elastic lepton-nucleon scattering and investigate the possibilities of eliminating or suppressing theoretical uncertainties induced by the nucleon structure in measuring the standard model parameters or in searching for new physics. On the basis of rather general assumptions about nucleon structure we have obtained new relations between cross sections and neutral current parameters which are weakly dependent on the nucleon structure. We also investigate the dependence of the QCD ? parameter extracted from the data on the unknown large-scale nucleon structure and propose a modification of the conventional QCD predictions in which the dependence on this uncertainty factor is suppressed

1993-07-01

127

A measurement of the nucleon structure function from muon-carbon deep inelastic scattering at high Q"2  

International Nuclear Information System (INIS)

Deep inelastic scattering cross sections have been measured with the CERN SPS muon beam at incident energies of 120 and 200 GeV. Approximately 100 000 events at each energy are used to obtain the structure function F_2(x,Q"2) in the kinematic region 0.3 < k < 0.7 and 25 GeV"2 < Q"2 < 200 GeV"2. (orig.)

1981-09-10

128

Scaling function, spectral function, and nucleon momentum distribution in nuclei  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The link between the scaling function extracted from the analysis of (e,e') cross sections and the spectral function/momentum distribution in nuclei is revisited. Several descriptions of the spectral function based on the independent particle model are employed, together with the inclusion of nucleon correlations, and effects of the energy dependence arising from the width of the hole states are investigated. Although some of these approaches provide rough overall agreement with data, they ar...

Antonov, A. N.; Ivanov, M. V.; Caballero, J. A.; Barbaro, M. B.; Udias, J. M.; Moya Guerra, E.; Donnelly, T. William

2011-01-01

129

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

1993-01-01

130

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

131

Internal Spin Structure of the Nucleon in Polarized Deep Inelastic Muon-Nucleon Scattering  

International Nuclear Information System (INIS)

We present the study of the internal spin structure of the nucleon in spin-dependent deep inelastic scattering of muons on nucleons. The data were taken by the NA47 experiment of the Spin Muon Collaboration (SMC) on the high energy muon beam at CERN. The experiment used the polarized proton and deuteron targets. The structure function g1p(x) and g1d(x) were determined from the asymmetries of the spin-dependent event rates in the range of 0.0032>=10 GeV2. Using the first moments of these structure functions an agreement with the Bjorken sum rule prediction was found within one standard deviation. The first moments of g1(x), for both proton and deuteron, are smaller than the Ellis-Jaffe sum rule prediction. This disagreement can be interpreted in terms of negative polarization of the strange sea in the nucleon. The singlet part of the axial current matrix element can be interpreted as an overall spin carried by quarks in the nucleon. Its value is significantly smaller than nucleon spin. Semi-inclusive asymmetries of yields of positive and negative hadrons produced on both targets were also measured and analysed in term of quark-parton model, together with inclusive asymmetries. From this analysis the quark spin distributions were determined, separately for valence u and d quarks and for non-strange sea quarks. Valence u quarks are positively polarized and their polarization increases with x. Valence d quarks are negatively polarized and their polarization does not exhibit any x-dependence. The non-strange sea is unpolarized in the whole measured range of x. The first moments of the valance quark spin distributions were found consistent with the values obtained from weak decay constants F and D and their second moments are consistent with lattice QCD calculations. In the QCD analysis of the world data the first moment of the gluon spin distribution was found with a large error. Also, a search for a non-perturbative anomaly at high x was done on the world data and the result was consistent with null. An extensive discussion of the SMC results and a comparison with results of SLAC experiment is presented. The new experiment of the COMPASS Collaboration, approved and being currently in preparation at CERN, was presented. The main physics issues of the muon part of this experiment, which are the gluon polarization and a continuation of the physics program of the SMC, were discussed. (author)

1998-01-01

132

Exploring the nucleon structure from first principles of QCD  

International Nuclear Information System (INIS)

Quantum Chromodynamics (QCD) is generally assumed to be the fundamental theory underlying nuclear physics. In recent years there is progress towards investigating the nucleon structure from first principles of QCD. Although this structure is best revealed in Deep Inelastic Scattering, a consistent analysis has to be performed in a fully non-perturbative scheme. The only known method for this purpose are lattice simulations. We first sketch the ideas of Monte Carlo simulations in lattice gauge theory. Then we comment in particular on the issues of chiral symmetry and operator mixing. Finally we present our results for the Bjorken variable of a single quark, and for the second Nachtmann moment of the nucleon structure functions. (orig.)

2010-01-01

133

Excited state contamination in nucleon structure calculations  

CERN Multimedia

Among the sources of systematic error in nucleon structure calculations is contamination from unwanted excited states. In order to measure this systematic error, we vary the operator insertion time and source-sink separation independently. We compute observables for three source-sink separations between 0.93 fm and 1.39 fm using clover-improved Wilson fermions and pion masses as low as 150 MeV. We explore the use of a two-state model fit to subtract off the contribution from excited states.

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

2011-01-01

134

Nucleon structure study by virtual compton scattering  

Energy Technology Data Exchange (ETDEWEB)

We propose to study nucleon structure by Virtual Compton Scattering using the reaction p(e,e`p){gamma} 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 {pi}{sup 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.

Berthot, J.; Bertin, P.Y.; Breton, V.; Fonvielle, H.; Hyde-Wright, C.; Quemener, G.; Ravel, O. [Clermont-Ferrand-2 Univ., 63 - Aubiere (France). Lab. de Physique Corpusculaire; Audit, G.; Cavata, C.; D`Hose, N.; Ducret, J.E.; Gousset, T.; Guichon, P.A.M.; Kerhouas, S.; Lhuillier, D.; Marchand, C.; Marchand, D.; Martino, J.; Mougey, J.; Roche, J.; Vernin, P. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee; Ryckbosch, D.; Van de Vyver, R.; Van Hoorebeke, L.; Vanderhaegen, M. [Ghent Rijksuniversiteit (Belgium); Braghieri, A.; Pedroni, P. [Pavia Univ. (Italy); Boeglin, W.U.; Boehm, R.; Distler, M.; Edelhoff, R.; Friedrich, J.; Geiges, R.; Jennewein, P.; Kahrau, M.; Korn, M.; Kramer, H.; Krygier, K.W.; Kunde, V.; Liesenfeld, A.; Merle, K.; Neuhausen, R.; Offermann, E.A.J.M.; Pospischil, T.; Rosner, G.; Sauer, P.; Schmieden, H.; Schardt, S.; Tamas, G.; Wagner, A.; Walcher, T.; Wolf, S. [Mainz Univ. (Germany). Inst. fuer Kernphysik

1995-12-31

135

Nucleon wave function from lattice QCD  

International Nuclear Information System (INIS)

In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)

2008-01-01

136

Nucleon wave function from lattice QCD  

Energy Technology Data Exchange (ETDEWEB)

In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)

Warkentin, Nikolaus

2008-04-15

137

Polarized Structure Function $\\sigma_{LT'}$ for $p({\\vec e},e'K^+)\\Lambda$ 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.

Nasseripour, Rakhsha; Raue, Brian; Ambrozewicz, Pawel; Carman, Daniel; Amaryan, Moscov; Amaryan, Moskov; Anciant, Eric; Anghinolfi, Marco; Asavapibhop, Burin; Asryan, Gegham; Audit, Gerard; Auger, Thierry; Avagyan, Harutyun; Baghdasaryan, Hovhannes; Baillie, Nathan; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Ball, J.P.; Ball, Jacques; Baltzell, Nathan; Barrow, Steve; Battaglieri, Marco; Beard, Kevin; Bedlinskiy, Ivan; Bektasoglu, Mehmet; Bellis, Matthew; Benmouna, Nawal; Berman, Barry; Biselli, Angela; Blaszczyk, Lukasz; Bonner, Billy; Bouchigny, Sylvain; Boyarinov, Sergey; Bradford, Robert; Branford, Derek; Briscoe, William; Brooks, William; Burkert, Volker; Butuceanu, Cornel; Calarco, John; Careccia, Sharon; Casey, Liam; Cetina, Catalina; Chen, Shifeng; Cheng, Lu; Cole, Philip; Collins, Patrick; Coltharp, Philip; Cords, Dieter; Corvisiero, Pietro; Crabb, Donald; Crede, Volker; Dale, Daniel; Dashyan, Natalya; De Masi, Rita; De Vita, Raffaella; De Sanctis, Enzo; Degtiarenko, Pavel; Dennis, Lawrence; Deur, Alexandre; Dhuga, Kalvir; Dickson, Richard; Djalali, Chaden; Dodge, Gail; Doughty, David; Dragovitsch, Peter; Dugger, Michael; Dytman, Steven; Dzyubak, Oleksandr; Egiyan, Hovanes; Egiyan, Kim; Elfassi, Lamiaa; Elouadrhiri, Latifa; Eugenio, Paul; Fatemi, Renee; Fedotov, Gleb; Feldman, Gerald; Feuerbach, Robert; Forest, Tony; Fradi, Ahmed; Funsten, Herbert; Garcon, Michel; Gavalian, Gagik; Gevorgyan, Nerses; Gilfoyle, Gerard; Giovanetti, Kevin; Girard, Pascal; Girod, Francois-Xavier; Goetz, John; Gothe, Ralf; Gothe, Ralf; Griffioen, Keith; Guidal, Michel; Guillo, Matthieu; Guler, Nevzat; Guo, Lei; Gyurjyan, Vardan; Hafidi, Kawtar; Hakobyan, Hayk; Hanretty, Charles; Hardie, John; Heddle, David; Hersman, F.; Hicks, Kenneth; Hleiqawi, Ishaq; Holtrop, Maurik; Hu, Jicun; Hyde, Charles; Ilieva, Yordanka; Ireland, David; Ishkhanov, Boris; Isupov, Evgeny; Ito, Mark; Jenkins, David; Jo, Hyon-Suk; Johnstone, John; Joo, Kyungseon; Juengst, Henry; Kalantarians, Narbe; Kellie, James; Khandaker, Mahbubul; Kim, Kui; Kim, Kyungmo; Kim, Wooyoung; Klein, Andreas; Klein, Franz; Kossov, Mikhail; Krahn, Zebulun; Kramer, Laird; Kubarovsky, Valery; Kuhn, Joachim; Kuhn, Sebastian; Kuleshov, Sergey; Kuznetsov, Viacheslav; Lachniet, Jeff; Laget, Jean; Langheinrich, Jorn; Lawrence, David; Livingston, Kenneth; Lu, Haiyun; Lukashin, Konstantin; MacCormick, Marion; Manak, Joseph; Markov, Nikolai; Mattione, Paul; McAleer, Simeon; McKinnon, Bryan; McNabb, John; Mecking, Bernhard; Mestayer, Mac; Meyer, Curtis; Mibe, Tsutomu; Mikhaylov, Konstantin; Minehart, Ralph; Mirazita, Marco; Miskimen, Rory; Mokeev, Viktor; Moreno, Brahim; Moriya, Kei; Morrow, Steven; Moteabbed, Maryam; Mueller, James; Munevar Espitia, Edwin; Mutchler, Gordon; Nadel-Turonski, Pawel; Niccolai, Silvia; Niculescu, Gabriel; Niculescu, Maria-Ioana; Niczyporuk, Bogdan; Niroula, Megh; Niyazov, Rustam; Nozar, Mina; Osipenko, Mikhail; Ostrovidov, Alexander; Park, Kijun; Pasyuk, Evgueni; Paterson, Craig; Pereira, Sergio; Peterson, Gerald; Philips, Sasha; Pierce, Joshua; Pivnyuk, Nikolay; Pocanic, Dinko; Pogorelko, Oleg; Pozdnyakov, Sergey; Preedom, Barry; Price, John; Procureur, Sebastien; Prok, Yelena; Protopopescu, Dan; Qin, Liming; Riccardi, Gregory; Ricco, Giovanni; Ripani, Marco; Ritchie, Barry; Rosner, Guenther; Rossi, Patrizia; Rubin, Philip; Sabatie, Franck; Salamanca, Julian; Salgado, Carlos; Santoro, Joseph; Sapunenko, Vladimir; Sayre, Donald; Schumacher, Reinhard; Serov, Vladimir; Shafi, Aziz; Sharabian, Youri; Sharov, Dmitri; Shvedunov, Nikolay; Simionatto, Sebastio; Skabelin, Alexander; Smith, Elton; Smith, Lee; Sober, Daniel; Sokhan, Daria; Stavinsky, Aleksey; Stepanyan, Samuel; Stepanyan, Stepan; Stokes, Burnham; Stoler, Paul; Strakovski, Igor; Strauch, Steffen; Taiuti, Mauro; Taylor, Shawn; Tedeschi, David; Thoma, Ulrike; Thompson, Richard; Tkabladze, Avtandil; Tkachenko, Svyatoslav; Ungaro, Maurizio; Vineyard, Michael; Vlassov, Alexander; Wang,

2008-06-01

138

The Flavor Structure of the Nucleon Sea  

CERN Document Server

We discuss two topics related to the flavor structure of the nucleon sea. The first is on the identification of light-quark intrinsic sea from the comparison between recent data and the intrinsic sea model by Brodsky et al. Good agreement between the theory and data allows a separation of the intrinsic from the extrinsic sea components. The magnitudes of the up, down, and strange intrinsic seas have been extracted. We then discuss the flavor structure and the Bjorken-x dependence of the connected sea (CS) and disconnected sea (DS). We show that recent data together with input from lattice QCD allow a separation of the CS from the DS components of the light quark sea.

Peng, J C; Cheng, H Y; Liu, K F

2014-01-01

139

Vector resonances and electromagnetic nucleon structure  

International Nuclear Information System (INIS)

Motivated by new, precise magnetic proton form factor data in the timelike region, a hybrid vector meson dominance (hVMD) formalism is employed to investigate the significance of excited vector meson resonances on electromagnetic nucleon structure. We find that the rho (1700), omega (1600), and two previously unobserved states are required to reproduce the local structure seen in the new LEAR data just above the pp-bar threshold. We also investigate sensitivity to the phi meson. The model dependence of our result is tested by introducing an alternative model which couples the isoscalar vector meson states to a hypothetical vector glueball resonance. We obtain nearly identical results from both models, except for GnE(q2) in the spacelike region which is very sensitive to the glueball mass and the effective phi NN coupling

1995-02-01

140

Vector resonances and electromagnetic nucleon structure  

International Nuclear Information System (INIS)

Motivated by new, precise magnetic proton form factor data in the timelike reigon, a hybrid vector meson dominance (hVMD) formalism is employed to investigate the significance of excited vector meson rsonances on electromagnetic nucleon structure. We find that the ?(1700), ?(1600), and two previously unobserved states are required to reproduce the local structure seen in the new LEAR data just above the p bar p threshold. We also investigate sensitivity to the ? meson. The model dependence of our result is tested by introducing an alternative model which couples the isoscalar vector meson states to a hypothetical vector glueball resonance. We obtain nearly identical results from both models, except for GEn(q2) in the spacelike region which is very sensitive to the glueball mass and the effective ?NN coupling

1995-02-01

 
 
 
 
141

Non-perturbative structure of the polarized nucleon sea  

CERN Multimedia

We investigate the flavour and quark-antiquark structure of the polarized nucleon by calculating the parton distribution functions of the nucleon sea using the meson cloud model. We find that the SU(2) flavor symmetry in the light antiquark sea and quark-antiquark symmetry in the strange quark sea are broken, {\\it i.e.} $\\Delta\\ubar < \\Delta \\dbar$ and $\\Delta s < \\Delta \\sbar$. The polarization of the strange sea is found to be positive, which is in contradiction to previous analyses. We predict a much larger quark-antiquark asymmetry in the polarized strange quark sea than that in the unpolarized strange quark sea. Our results for both polarized light quark sea and polarized strange quark sea are in good agreement with the recent HERMES data.

Cao, F G; Cao, Fu-Guang

2003-01-01

142

Structure and spin of the nucleon  

Directory of Open Access Journals (Sweden)

Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL. TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC, FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.

Avakian H.

2014-03-01

143

Studying the Nucleon Structure with Spin  

International Nuclear Information System (INIS)

The BLAST (Bates Large Acceptance Spectrometer Toroid) collaboration is finalizing the analysis of a systematic study of the spin-dependent, electromagnetic interaction on hydrogen and deuterium. The experiment utilized: the highly polarized electron beam of the MIT-Bates Linear Accelerator Center stored in the South Hall Ring; an internal gas target of isotopically pure and highly polarized hydrogen or deuterium provided by an atomic beam source; and the symmetric, general purpose BLAST spectrometer. By making simultaneous measurements of many reaction channels for different combinations of beam helicity and target polarization BLAST is providing new, precise measurements for the nucleon and deuteron elastic form factors as well as studying the structure of deuterium and pion production from hydrogen and deuterium. A brief overview of the experiment will be presented together with a selection results

2007-10-26

144

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

145

Understanding nucleon structure using lattice simulations. Recent progress on three different structural observables  

International Nuclear Information System (INIS)

This review focuses on the discussion of three key results of nucleon structure calculations on the lattice. These three results are the quark contribution to the nucleon spin, Jq, the nucleon-? transition form factors, and the nucleon axial coupling, gA. The importance for phenomenology and experiment is discussed and the requirements for future simulations are pointed out. (orig.)

2007-01-01

146

Nucleon Excited State Wave Functions from Lattice QCD  

CERN Document Server

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

Roberts, Dale S; Leinweber, Derek B

2013-01-01

147

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)

2010-01-01

148

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 167 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 ...

Collaboration, The Jefferson Lab Hall C. E. -.; :; Liang, Y.; Tvaskis, V.; Christy, M. E.; Ahmidouch, A.; Armstrong, C. S.; Arrington, J.; Asaturyan, R.; Avery, S.; Baker, O. K.; Beck, D. H.; Blok, H. P.; Bochna, C. W.; Boeglin, W.

2004-01-01

149

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 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)

2007-06-11

150

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(2G), consistent with the Adelaide-JLab Collaboration's result. The hyperon ? and ? axial coupling constants are also performed for the first time in a lattice calculation, g?? = 0.441(14) and g?? -0.277(11)

2007-06-11

151

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

Science.gov (United States)

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 ? e?Xh, the QCD hardness scale gradually diminishes from the hard scale, Q2, 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-?. The semi-inclusive cross section for production of slow protons in charged-current deep inelastic (anti)neutrino scattering on protons and neutrons is discussed. The standard hadronization models based upon the color neutralization mechanism appear to underestimate the rate of slow proton production on hydrogen. The presence of the virtual mesons (pions) in the nucleon leads to an additional mechanism for proton production, referred to as spectator process. The results of the calculations are compared with the CERN bubble chamber (BEBC) data. I discuss the structure of deep-inelastic events induced by the pione-xchange at HERA kinematics. Most of the event characteristics do not provide a possibility to distinguish the ordinary DIS fragmentation events from those induced by the pion-exchange mechanism. The only exception is the energy distribution of outgoing neutrons. The pion cloud model predicts energy distribution of neutrons which differs significantly from the standard hadronization models which can in principle be verified experimentally. A detailed analysis of semi-exclusive diffractive processes in ep DIS at HERA, with the diffractive final states in the forward direction is presented. The contributions of the subleading f 0; ?,a 2, ? reggeons and the pion exchanges to the diffractive structure function with the forward proton or neutron are estimated. It is found that the ( a2, ?) reggeons are entirely responsible for the forward neutron production at ? IP Deck mechanism. The significance of this reaction for the processes measured at HERA is discussed. In the DIS production of leading protons DIS off neutral pions must be supplemented by a contribution from isoscalar reggeon ( f0) exchange extrapolated down to moderate values of ? L. I comment on the ? and Q2 dependence of leading proton production as a probe of a universal pattern of the ?, Q2 evolution of the nucleon and meson (reggeon) structure functions at small ?.

Szczurek, A.

152

Nucleon structure function at small ?  

International Nuclear Information System (INIS)

This is a status report on the behaviour of deeply inelastic scattering in the low x region, where a new physics to be expected. It is bound to be theoretical review, since there is no data available at truely small values of x, say x -3. New data from HERA are anticipated and I am viewing on this talk as summary of the theoretical situation in the region of small x, as is just before this new area of physics will be studied experimentally. This is an extended version of the talk which was presented at EP-HEP 91 Conference. (orig.)

1991-08-01

153

Correlated overlap functions and nucleon removal reactions from 16 O  

International Nuclear Information System (INIS)

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

1999-12-09

154

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

1976-01-01

155

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

156

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

157

Probing nucleon structure on the lattice  

International Nuclear Information System (INIS)

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.)

2006-01-01

158

Travels With Tony-Nucleon Structure Through Our Ages  

CERN Multimedia

Nucleon structure is currently understood from a unified light-front, infinite-momentum-frame framework. The specific examples of the neutron transverse charge distribution and the shape of the proton are discussed here.

Miller, Gerald A

2010-01-01

159

Probing nucleon strangeness structure with $\\phi$ electroproduction  

CERN Document Server

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

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

1999-01-01

160

Generalized vector-meson dominance and the electromagnetic structure of the nucleon  

International Nuclear Information System (INIS)

We follow our recent model to synthesize meson-dynamics and asymptotic QCD predictions to calculate the electromagnetic structure functions of the nucleon. The requirement that the photon couples asymptotically as a single field leads to a generalization of the vector-meson dominance model. The resulting structure functions (space like region) are in quantitative agreement with experiments. (orig.)

1984-07-05

 
 
 
 
161

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

162

Tests of QCD and non-asymptotically-free theories of the strong interaction by an analysis of the nucleon structure functions xF_3, F_2 and anti q  

International Nuclear Information System (INIS)

The scaling violations of the structure functions F_2, xF_3, and anti q, as measured in deep-inelastic neutrino-nucleon scattering at high hadron mass W, have been compared with the predictions of QCD and other candidate field theories of strong interactions. Non-asympotically free theories with scalar and vector gluons are incompatible with the data. This leaves QCD as the only field theory that gives a consistent description of all the observed scaling violations. The data do not, however, permit a sensitive test of the existence of the gluon self-coupling. (orig.)

1982-01-01

163

The Spin structure of the nucleon  

International Nuclear Information System (INIS)

We present the final results of the spin asymmetries A1 and the spin structure functions g1 of the proton and the deuteron from the SMC. In the region x 1. The usual method employs inclusive scattering events and includes a large radiative background at low x, while the new method minimises the radiative background by selecting events with at least one hadron as well as a muon in the final state. Using these data and other presently available data we performed a next-to-leading order QCD analysis of the spin structure function g1. We present results for the first moments of the proton, deuteron and neutron structure functions, and determine singlet and non-singlet parton distributions. We also test the Bjorken sum rule and find agreement with the theoretical prediction at the level of 10%

1999-03-01

164

Understanding nucleon structure using lattice simulations. Recent progress on three different structural observables  

Energy Technology Data Exchange (ETDEWEB)

This review focuses on the discussion of three key results of nucleon structure calculations on the lattice. These three results are the quark contribution to the nucleon spin, J{sub q}, the nucleon-{delta} transition form factors, and the nucleon axial coupling, g{sub A}. The importance for phenomenology and experiment is discussed and the requirements for future simulations are pointed out. (orig.)

Schroers, W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

2007-01-15

165

Spin-Isospin Structure and Pion Condensation in Nucleon Matter  

CERN Document Server

We report variational calculations of symmetric nuclear matter and pure neutron matter, using the new Argonne v18 two-nucleon and Urbana IX three-nucleon interactions. At the equilibrium density of 0.16 fm^-3 the two-nucleon densities in symmetric nuclear matter are found to exhibit a short-range spin-isospin structure similar to that found in light nuclei. We also find that both symmetric nuclear matter and pure neutron matter undergo transitions to phases with pion condensation at densities of 0.32 fm^-3 and 0.2 fm^-3, respectively. Neither transtion occurs with the Urbana v14 two-nucleon interaction, while only the transition in neutron matter occurs with the Argonne v14 two-nucleon interaction. The three-nucleon interaction is required for the transition to occur in symmetric nuclear matter, whereas the the transition in pure neutron matter occurs even in its absence. The behavior of the isovector spin-longitudinal response and the pion excess in the vicinity of the transition, and the model dependence of...

Akmal, A; Akmal, Arya; Pandharipande, Vijay R.

1997-01-01

166

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

167

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.)

1996-01-01

168

Experimental determination of the pion and nucleon structure functions by measuring high-mass muon pairs produced by pions of 200 and 280 GeV/c on a platinum target  

International Nuclear Information System (INIS)

We measured the production of massive muon pairs on a platinum target by pions of 200 and 280 GeV/c. The following number of dimuon events have been collected for M > 4 GeV/c"2. (a) ?"- of 200 GeV/c: approx. 5900 events; (b) ?"+ of 200 GeV/c: approx. 2200 events; (c) ?"- of 280 GeV/c: approx. 5700 events. These data were analysed in terms of the Drell-Yan model in order to obtain the pion and nucleon structure functions, which are parametrised with expressions of the form xsup(?)(1 - x)sup(?). Our results are compared to the structure functions obtained in other experiments. (orig.)

1979-07-04

169

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

International Nuclear Information System (INIS)

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

2007-09-01

170

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

CERN Multimedia

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

171

The spin structure of the nucleon  

Energy Technology Data Exchange (ETDEWEB)

The nucleon is a spin 1/2 particle. This spin can be decomposed into the contributions of its constituents: 1/2 equals 1/2*{delta}{sigma} + {delta}g + L{sub q} + L{sub g} where the first term is the contribution from the spin of the quarks, the second term is the contribution from the spin of the gluons and L{sub q} and L{sub g} are the orbital momentum of the quark and the gluon respectively. The {delta}{sigma} contribution of the spin of quarks can be studied through polarized deep inelastic scattering (DIS). We introduce DIS and the so-called parton model and then turn to the case of polarized DIS in the inclusive and semi-inclusive cases. We also discuss how a third parton distribution, called transversity, appears together with the unpolarized and the longitudinally polarized (or helicity) ones. We show how the longitudinally polarized gluon distribution can be measured. Then we focus on the SMC and COMPASS experiments performed at CERN. SMC confirmed a previous result by showing that the contribution of the spin of the quark to the spin of the nucleon was small. SMC also performed a measurement on the deuterium in order to test, for the first time, the Bjorker sum rules, which is a fundamental prediction of quantum chromodynamics. The COMPASS experiment started collecting data in 2002. Its main objectives are the gluon polarization {delta}g/g and the so-called transversity. (A.C.)

Le Goff, J.M

2005-02-15

172

Nucleon structure studies through exclusive reactions with an EIC at JLab  

Science.gov (United States)

Hadrons in QCD are relativistic many-body systems, with a fluctuating number of elementary quark/gluon constituents and a very rich structure of the wave function, with distinct components in different kinematic regions. The 12 GeV energy upgrade at Jefferson Lab will allow a detailed study of the valence quark component. With an EIC at Jefferson Lab we enter the region where the many-body nature of hadrons, coupling to vacuum excitations, etc., become manifest. In this talk I will discuss the exciting prospects of studying the landscape of nucleon structure using exclusive reactions, and in particular the gluon and sea quark imaging of the nucleon. )

Horn, Tanja

2010-02-01

173

Fundamental nucleon-nucleon interaction: probing exotic nuclear structure using GEANIE at LANCE/WNR  

Energy Technology Data Exchange (ETDEWEB)

The initial goal of this project was to study the in-medium nucleon-nucleon interaction by testing the fundamental theory of nuclear structure, the shell model, for nuclei between {sup 8}Zr and {sup 100}Sn. The shell model predicts that nuclei with ''magic'' (2,8,20,28,40,50, and 82) numbers of protons or neutrons form closed shells in the same fashion as noble gas atoms [may49]. A ''doubly magic'' nucleus with a closed shell of both protons and neutrons has an extremely simple structure and is therefore ideal for studying the nucleon-nucleon interaction. The shell model predicts that doubly magic nuclei will be spherical and that they will have large first-excited-state energies ({approx} 1 to 3 MeV). Although the first four doubly-magic nuclei exhibit this behavior, the N = Z = 40 nucleus, {sup 80}Zr, has a very low first-excited-state energy (290 keV) and appears to be highly deformed. This breakdown is attributed to the small size of the shell gap at N = Z = 40. If this description is accurate, then the N = Z = 50 doubly magic nucleus, {sup 100}Sn, will exhibit ''normal'' closed-shell behavior. The unique insight provided by doubly-magic nuclei from {sup 80}Zr to {sup 100}Sn has made them the focus of tremendous interest in the nuclear structure community. However, doubly-magic nuclei heavier than {sup 56}Ni become increasingly difficult to form due to the coulomb repulsion between the protons which favors the formation of neutron-rich nuclei. The coulomb repulsion creates a ''proton drip-line'' beyond which the addition of any additional bound protons is energetically impossible. The drip line renders the traditional experimental technique used in their formation, the heavy-ion reaction, less than ideal as a method of forming doubly-magic nuclei beyond {sup 80}Zr. The result has been a lack of an new spectroscopic information on doubly magic nuclei in more than a decade [lis87]. Furthermore, uncertainties in reaction dynamics modeling made it difficult for the nuclear science community to predict the cross section or forming these highly-neutron deficient nuclei. Therefore, we decided to try a new approach to forming highly-neutron deficient nuclei with the hope of both gaining spectroscopic information for nuclei near {sup 100}Sn, and also gaining insight into reaction dynamics at high (E{sub x} > 200 MeV) incident nucleon energy.

Bernstein, L

2000-02-25

174

Calculating structure functions on the lattice  

International Nuclear Information System (INIS)

We describe the methods used to calculate the nucleon structure functions from quenched lattice QCD, and present some results for moments of the polarized and unpolarized structure functions. (author)

1996-06-01

175

Advanced nucleon electromagnetic structure model and charge proton rms radius  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-12-15

176

Hyperspherical Harmonics Technique for the Electromagnetic Structure of Nucleon  

Science.gov (United States)

We demonstrate that it is possible to find the experimentally observed structure of both proton and neutron, consistently with the baryon mass spectrum, using a single quark potential model. The hyperspherical harmonics expansion technique was used to obtain accurately the symmetric and mixed symmetric states of the nucleon.

Nag, R.; Sanyal, S.; Mukherjee, S. N.

1990-01-01

177

Hyperspherical harmonics technique for the electromagnetic structure of nucleon  

International Nuclear Information System (INIS)

We demonstrate that it is possible to find the experimentally observed structure of both proton and neutron, consistently with the baryon mass spectrum, using a single quark potential model. The hyperspherical harmonics expansion technique was used to obtain accurately the symmetric and mixed symmetric states of the nucleon. (author)

1990-01-01

178

Twist-3 polarized structure functions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We review the nucleon's twist-3 polarized structure functions from the viewpoint of gauge invariant, nonlocal light-cone operators in QCD. We discuss a systematic treatment of the polarized structure functions and the corresponding parton distribution functions. We emphasize unique features of higher twist distributions, and the role of the QCD equations of motion to derive their anomalous dimensions for Q^2-evolution.

Kodaira, Jiro; Tanaka, Kazuhiro

1999-01-01

179

Measurement of the polarization of strange quarks in the nucleon and determination of quark fragmentation functions into hadrons  

International Nuclear Information System (INIS)

Understanding the nucleon structure is currently one of the main challenges encountered in nuclear physics. The present work represents a contribution to the study of the nucleon structure and deals, in particular, with the study of the role of strange quarks in the nucleon. The latter can be investigated by determining the strange quark distribution in the nucleon as well as the contribution of the spins of strange quarks to the nucleon spin. This work first presents a measurement of the nucleon spin performed via Deeply Inelastic Scattering (DIS) of a muon beam off polarized proton and deuterium targets. The result is found to be strongly dependent on the quark fragmentation functions into hadrons (FFs), which define the probability that a quark of a given flavour fragments into a final state hadron. The FFs are poorly known, in particular, the FF of strange quark into kaons, which play an important role in the determination of the nucleon spin. In deep inelastic scattering process, the access to the FFs is provided by the hadron multiplicities which, in turn, define the average number of hadrons produced per DIS event. Pion and kaon multiplicities have been extracted versus different kinematic variables, using DIS data collected by deeply inelastic scattering of a 160 GeV/c muons off a deuterium target. A first Leading Order (LO) extraction of the fragmentation functions has then been performed using the measured pion and kaon multiplicities. (author)

2011-01-01

180

Spin structure functions  

Energy Technology Data Exchange (ETDEWEB)

Spin-dependent observables have been a powerful tool to probe the internal structure of the nucleon and to understand the dynamics of the strong interaction. Experiments involving spin degrees of freedom have often brought out surprises and puzzles. The so-called "spin crisis" in the 1980s revealed the limitation of naive quark-parton models and led to intensive worldwide efforts, both experimental and theoretical, to understand the nucleon spin structure. With high intensity and high polarization of both the electron beam and targets, Jefferson Lab has the world's highest polarized luminosity and the best figure-of-merit for precision spin structure measurements. It has made a strong impact in this subfield of research. This chapter will highlight Jefferson Lab's unique contributions in the measurements of valence quark spin distributions, in the moments of spin structure functions at low to intermediate Q2, and in the transverse spin structure.

Jian-ping Chen, Alexandre Deur, Sebastian Kuhn, Zein-eddine Meziani

2011-06-01

 
 
 
 
181

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

1996-04-29

182

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 empl...

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

2010-01-01

183

Sum Rules for Nucleon GPDs and Border Function Formulation  

Energy Technology Data Exchange (ETDEWEB)

Recently developed new 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 found that 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, Anatoly V. [JLAB, Old Dominion U., JINR

2013-09-01

184

Transverse spin structure of the nucleon from lattice QCD simulations  

CERN Multimedia

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 $h_1^\\perp$, describing correlations of transverse quark spin and intrinsic transverse momentum of quarks, is large and negative for both up and down quarks.

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

2006-01-01

185

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

186

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.)

2006-01-01

187

Gauge invariance, canonical quantization and Poincaré covariance in nucleon structure  

Science.gov (United States)

There are different quark and gluon momentum, spin and orbital angular momentum operators used in the study of nucleon structure. We analyze the physical contents of these operators and propose a new set of operators based on gauge invariance principle, canonical quantization rule and Poincaré covariance. Atomic structure is a simpler testing ground of these operators and has been analyzed together. These new operators are the gauge invariant version of the gauge non-invariant canonical version used in physics since the establishment of quantum mechanics and reduce to the familiar canonical ones in Coulomb gauge.

Wang, Fan; Sun, W. M.; Chen, X. S.; Zhang, P. M.

2014-04-01

188

Muon-nucleon, deep inelastic scattering: determination of the ratio R = sigma sub(L)/sigma sub(T) and comparison of structure functions to QCD predictions  

International Nuclear Information System (INIS)

Using the structure functions F2 measured in E.M.C., we have extracted the following values for the QCD scale parameter ?, at next to leading order: hydrogen target: ?sub(MS) = 139(+170-100)MeV; iron target: ?sub(MS) = 170(+160-100)MeV we have performed a study of the 1/Q2 effects on the Q2 domain covered by SLAC and E.M.C. We have extracted the ratio R = sigma sub(L)/sigma sub(T) for various chi bins and compared it with other experimental values and theoretical predictions. The mean value = 0+-.15 was found and is compatible with zero

1982-01-01

189

Chiral symmetry breaking and electromagnetic structure of the nucleon  

CERN Document Server

The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and are related to the charge radii of the baryons. We have calculated the charge radii of octet baryons in the framework of chiral constituent quark model with the inclusion of the spin-spin generated configuration mixing. This model is quite successful in predicting the low energy hadron matrix elements. The results obtained in the case of charge radii are also comparable to the latest experimental studies and show improvement over some theoretical interpretations.

Dahiya, Harleen

2010-01-01

190

Chiral symmetry breaking and electromagnetic structure of the nucleon  

International Nuclear Information System (INIS)

The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and are related to the charge radii of the baryons. We have calculated the charge radii of octet baryons in the framework of chiral constituent quark model with the inclusion of the spin-spin generated configuration mixing. This model is quite successful in predicting the low energy hadron matrix elements. The results obtained in the case of charge radii are also comparable to the latest experimental studies and show improvement over some theoretical interpretations.

2010-12-28

191

Phenomenological delineation of the quark-gluon structure from nucleon electromagnetic form factors  

International Nuclear Information System (INIS)

We investigate a synthesis of topological chiral models with the vector meson dominance idea, with applications to nucleon and pion electromagnetic form factors. We suggest that the large tensor coupling of the rho-meson to the nucleon, about twice that given by the vector dominance model, is an indicator of quark-gluon substructure of the nucleon at distances < or approx.1/2fm. Nucleon and pion form factors are fit within this model, which implies that the ?-ray coupling is about 50% directly to the intrinsic quark structure of the nucleon or pion, and the other 50% is indirect, through vector mesons. (orig.)

1986-06-23

192

Polarized lepton-nucleon scattering  

Energy Technology Data Exchange (ETDEWEB)

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.

Hughes, E.

1994-02-01

193

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

1993-08-06

194

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

CERN Multimedia

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

195

A Haplousterotic Model for the Nucleon Wave Function  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We review the consequences of the sensitivity of the relation between the moments of a model for the nucleon quark distribution amplitude and the coefficients of its polynomial expansion. Criteria for a simpler approach to constructing a model for the quark distribution amplitude are formulated. We describe how such a simpler (or "haplousterotic") model for the quark distribution amplitude of the nucleon is obtained from the QCD sum-rule moments of COZ.

Eckardt, Robert; Hansper, J. Org; Gari, Manfred F.

1996-01-01

196

Nucleon-nucleon interactions  

Energy Technology Data Exchange (ETDEWEB)

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 {ital 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 {ital v}{sub 18} potential, one of a number of new potentials that fit elastic nucleon-nucleon data up to 350 MeV with a {Chi}{sup 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 {ital NN} interactions. We conclude with some remarks on how our empirical knowledge of {ital NN} interactions may help constrain models at the quark level, and hence models of nucleon structure.

Wiringa, R.B.

1996-12-31

197

The meson polarized distribution function and mass dependence of the nucleon parton densities  

CERN Document Server

The polarized distribution functions of mesons, including pion, kaon and eta, using the proton structure function, are calculated. We are looking for a relationship between the polarized distribution of mesons and the polarized structure of nucleons. We show that the meson polarized parton distributions leads to zero total spin for the concerned mesons, considering the orbital angular momentum of quarks and gluons inside the meson. Two separate Monte Carlo algorithms are applied to compute the polarized parton distributions of the kaon. Via the mass dependence of quark distributions, the distribution function of the eta meson is obtained. A new method by which the polarized sea quark distributions of protons are evolved separately -- which cannot be performed easily using the standard solution of DGLAP equations -- is introduced. The mass dependence of these distributions is obtained, using the renormalization group equation which makes their evolutions more precise. Comparison between the evolved distributio...

Mirjalili, A

2014-01-01

198

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

199

Flavor Structure of the Nucleon Sea from Lattice QCD  

CERN Multimedia

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

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

2014-01-01

200

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

 
 
 
 
201

What the lattice can tell us about nucleon structure  

International Nuclear Information System (INIS)

This review focuses on the current status of lattice calculations of three observables which are both phenomenologically and experimentally relevant and have been scrutinized recently. These three observables are the nucleon electromagnetic form factors, the momentum fraction, u-d, and the nucleon axial coupling, gA

2006-03-01

202

What the lattice can tell us about nucleon structure  

International Nuclear Information System (INIS)

This review focuses on the current status of lattice calculations of three observables which are both phenomenologically and experimentally relevant and have been scrutinized recently. These three observables are the nucleon electromagnetic form factors, the momentum fraction, left angle x right angle u-d, and the nucleon axial coupling, gA. (orig.)

2005-01-01

203

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

International Nuclear Information System (INIS)

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

2002-01-01

204

Investigation of the nucleon electromagnetic structure by polarization effects in e"+e"->NantiN processes  

International Nuclear Information System (INIS)

Polarization effects in e"+e"-->NantiN processes are investigated form various aspects. The sensitivity in a behaviour of the vector polarization components of the nucleon is demonstrated graphically by using two recent formulations of the unitary and analytic VMD model of the nucleon electromagnetic structure. 14 refs.; 4 figs

1992-01-01

205

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

CERN Document Server

A detailed study of the 4He longitudinal response function R_L(\\omega,q) is performed at different kinematics, with particular emphasis on the role of three-nucleon forces. The effects shown 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 in addition. The Argonne V18 nucleon-nucleon interaction and two different three-nucleon force models (Urbana IX, Tucson-Melbourne') are used. At lower momentum transfer (q<= 200$ MeV/c) three-nucleon forces play an important role. One even finds a dependence of R_L on the three-nucleon force model itself with differences up to 10%. Thus a Rosenbluth separation of the inclusive electron scattering cross section of 4He at low momentum transfer would be of high value in view of a discrimination between different three-nucleon force ...

Bacca, Sonia; Leidemann, Winfried; Orlandini, Giuseppina

2009-01-01

206

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

207

Chiral Magnetism of the Nucleon  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the quark mass expansion of the magnetic moments of the nucleon in a chiral effective field theory including nucleons, pions and delta resonances as explicit degrees of freedom. We point out that the usual powercounting applied so far to this problem misses important quark mass structures generated via an intermediate isovector M1 nucleon-delta transition. We propose a modified powercounting and compare the resulting chiral extrapolation function to available (quenc...

Hemmert, Thomas R.; Weise, Wolfram

2002-01-01

208

The role of nucleon structure in finite nuclei  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The quark-meson coupling model, based on a mean field description of non-overlapping nucleon bags bound by the self-consistent exchange of $\\sigma$, $\\omega$ and $\\rho$ mesons, is extended to investigate the properties of finite nuclei. Using the Born-Oppenheimer approximation to describe the interacting quark-meson system, we derive the effective equation of motion for the nucleon, as well as the self-consistent equations for the meson mean fields. The model is first applie...

Guichon, P. A. M.; Saito, K.; Rodionov, E.; Thomas, A. W.

1995-01-01

209

New measurements on the nucleon structure with MAMI  

International Nuclear Information System (INIS)

The Institut fuer Kernphysik in Mainz is operating the microtron MAMI producing a high-quality continuous beam of electrons with an endpoint energy of 1.5-1.6 GeV for hadron and nuclear physics. The spectrometer facility has been used to measure the proton elastic form factors with unprecedented sub-percent precision, being sensitive for the first time to detailed structures in the form factor as currently under debate. Since 2008 the magnetic spectrometer Kaos is used in the facility for kaon spectroscopy addressing some important issues in the field of elementary kaon photoelectro-production. The Crystal Ball and TAPS set-up was equipped with a frozen-spin polarized target to perform new high-precision, high-statistics measurements of neutral meson production and polarization observables on the nucleon. At the A4 experimental set-up new measurements of the parity violating asymmetry in elastic electron scattering were performed, leading to an improved determination of the strange quark contributions to the vector form factors of the proton. To conclude, the electron accelerator MAMI represents a unique research tool for precision measurements with the electroweak probe that is now also covering the strangeness sector.

2010-03-15

210

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.

2009-12-01

211

Studies of the transverse structure of the nucleon at JLab  

Energy Technology Data Exchange (ETDEWEB)

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

Mirazita, Marco [INFN, Frascati (Italy)

2014-03-01

212

Nuclear energy density functional from chiral two- and three-nucleon interactions  

CERN Multimedia

An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading order chiral three-nucleon interaction with its parameters $c_E, c_D$ and $c_{1,3,4}$ fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions $F_\

Holt, J W; Weise, W

2011-01-01

213

On the Dirac Structure of the Nucleon Self-energy in Nuclear Matter  

CERN Document Server

The relativistic structure of the self-energy of a nucleon in nuclear matter is investigated including the imaginary and real components which arise from the terms of first and second order in the NN interaction. A parameterized form of Brueckner $G$ matrix is used for the NN interaction. The effects of the terms beyond the DBHF approximation on quasiparticle energies and the optical potential for nucleon-nucleus scattering are discussed.

Trasobares, A; Ramos, A; Müther, H

1998-01-01

214

Nucleon structure in terms of OPE with non-perturbative Wilson coefficients  

International Nuclear Information System (INIS)

Lattice calculations could boost our understanding of Deep Inelastic Scattering by evaluating moments of the Nucleon Structure Functions. To this end we study the product of electromagnetic currents between quark states. The Operator Product Expansion (OPE) decomposes it into matrix elements of local operators (depending on the quark momenta) and Wilson coefficients (as functions of the larger photon momenta). For consistency with the matrix elements, we evaluate a set of Wilson coefficients non-perturbatively, based on propagators for numerous momentum sources, on a 243 x 48 lattice. The use of overlap quarks suppresses unwanted operator mixing and lattice artifacts. Results for the leading Wilson coefficients are extracted by means of Singular Value Decomposition. (orig.)

2008-07-14

215

Nucleon structure in terms of OPE with non-perturbative Wilson coefficients  

Energy Technology Data Exchange (ETDEWEB)

Lattice calculations could boost our understanding of Deep Inelastic Scattering by evaluating moments of the Nucleon Structure Functions. To this end we study the product of electromagnetic currents between quark states. The Operator Product Expansion (OPE) decomposes it into matrix elements of local operators (depending on the quark momenta) and Wilson coefficients (as functions of the larger photon momenta). For consistency with the matrix elements, we evaluate a set of Wilson coefficients non-perturbatively, based on propagators for numerous momentum sources, on a 24{sup 3} x 48 lattice. The use of overlap quarks suppresses unwanted operator mixing and lattice artifacts. Results for the leading Wilson coefficients are extracted by means of Singular Value Decomposition. (orig.)

Bietenholz, W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC]|[Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik; Cundy, N.; Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik; Horsley, R.; Zanotti, J.M. [Edinburgh Univ. (United Kingdom). School of Physics; Perlt, H.; Schiller, A. [Leipzig Univ. (Germany). Inst. fuer Theoretische Physik; Pleiter, D.; Schierholz, G. [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

2008-10-15

216

Structure and Flow of the Nucleon Eigenstates in Lattice QCD  

CERN Document Server

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

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

2013-01-01

217

Do nucleons that are bound in nuclei change their structure?  

Energy Technology Data Exchange (ETDEWEB)

Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. Recent measurements at both Mainz and Jefferson Lab of the proton recoil polarization in the {sup 4}He({rvec e},e'{rvec p}){sup 3}H reaction up to Q{sup 2} = 2.6 (GeV/c){sup 2} are presented. The measured ratio of polarization-transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation, indicating that the treatment of final-state interactions is under control. A recently approved follow-up experiment at a Q{sup 2} of 0.8 (GeV/c){sup 2} and 1.3 (GeV/c){sup 2} with unprecedented precision will provide one of the most stringent tests of the applicability of these calculations.

Steffen Strauch

2004-01-11

218

Shell structure and few-nucleon removal in intranuclear cascade  

CERN Document Server

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

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

2014-01-01

219

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

2004-01-01

220

Nucleon physics  

International Nuclear Information System (INIS)

This book is an introduction to the interactions of nucleons with special regards to their contribution to nuclear forces. After a general description of the nuclear structure as a configuration of many nucleons the properties and interactions of nucleons are described with an excursion to the fundamental processes governing them. Then nuclear energy levels are considered. Thereafter nuclear energy-level transitions are described in the framework of the governing elementary processes. Finally nuclear reactions are considered in this framework. This book is suited as a supplement to a textbook in nuclear physics for students, who want to get a deeper insight in the fundamental processes in nuclei. (HSI)

1981-01-01

 
 
 
 
221

Simple function forms and nucleon-nucleus total cross sections  

CERN Multimedia

Total cross sections for neutron scattering with energies between 10 and 600 MeV and from nine nuclei spanning the mass range from 6Li to 238U have been analyzed using a simple function of three parameters. The values of those parameters with which neutron total cross section data are replicated vary smoothly with energy and target mass and may themselves be represented by functions of energy and mass.

Deb, P K

2004-01-01

222

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

223

Nucleon EM Form Factors and its Spin Structure  

International Nuclear Information System (INIS)

The powerpoint presentation highlights the very active experimental program on nucleon form factors and spin factors, which is attributed to the development of a polarized beam (> 100 ?A, > 75%). Other points noted in the summary include: GEp: precise data set up to Q2 = 5.6 (GeV/c)2 charge FF differs from magnetization FF - Q2 = 9 (GeV/c)2 planned; GEn: 3 successful experiments, precise data anticipated - higher Q2 possible and approved; GMn: Q2 3He(e,e') - high Q2 data from 2H(e,e',n)/2H(e,e'p) in analysis; A1n: first accurate measurements at intermediate x-values; and need active theory support (radiative corrections, lattice QCD, relativistic wf, etc.)

2003-04-04

224

Study of two-nucleon wave functions in 3He  

International Nuclear Information System (INIS)

The reaction 3He(p,2p)pn has been studied at 250 and 400 MeV in a quasifree scattering arrangement characterized by P(recoil) = 0 and various excitation or total energies E(recoil) of the unobserved p-n pair. 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 calculated as the overlap between plane waves for the p-n pair and Irving, Irving-Gunn, and Khanna wave functions for 3He

1983-05-30

225

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

1982-01-01

226

Nucleon structure in the chiral regime with domain wall fermions on an improved staggered sea  

International Nuclear Information System (INIS)

Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The twist two matrix elements are calculated using a mixed action of domain wall valence quarks and asqtad staggered sea quarks and are renormalized perturbatively. Several observables are extrapolated to the physical limit using chiral perturbation theory. Results are compared with experimental moments of quark distributions and electromagnetic form factors and phenomenologically determined generalized form factors, and the implications on the transverse structure and spin content of the nucleon are discussed. (orig.)

2006-07-23

227

Nucleon structure in the chiral regime with domain wall fermions on an improved staggered sea  

Energy Technology Data Exchange (ETDEWEB)

Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The twist two matrix elements are calculated using a mixed action of domain wall valence quarks and asqtad staggered sea quarks and are renormalized perturbatively. Several observables are extrapolated to the physical limit using chiral perturbation theory. Results are compared with experimental moments of quark distributions and electromagnetic form factors and phenomenologically determined generalized form factors, and the implications on the transverse structure and spin content of the nucleon are discussed. (orig.)

Edwards, R.G.; Richards, D.G. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Fleming, G. [Yale Univ., New Haven, CT (United States). Sloane Physics Laboratory; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Negele, J.W.; Pochinsky, A.V. [Massachusetts Institute of Technology, Cambridge, MA (United States). Center for Theoretical Physics; Orginos, K. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)]|[College of William and Mary, Williamsburg, VA (United States). Dept. of Physics; Renner, D.B. [Arizona Univ., Tucson, AZ (United States). Dept. of Physics; Schroers, W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

2006-10-15

228

Nucleon structure in the chiral regime with domain wall fermions on an improved staggered sea  

Energy Technology Data Exchange (ETDEWEB)

Moments of unpolarized, helicity, and transversity distributions, electromagnetic form factors, and generalized form factors of the nucleon are presented from a preliminary analysis of lattice results using pion masses down to 359 MeV. The twist two matrix elements are calculated using a mixed action of domain wall valence quarks and asqtad staggered sea quarks and are renormalized perturbatively. Several observables are extrapolated to the physical limit using chiral perturbation theory. Results are compared with experimental moments of quark distributions and electromagnetic form factors and phenomenologically determined generalized form factors, and the implications on the transverse structure and spin content of the nucleon are discussed.

R.G. Edwards; G. Fleming; Ph. Hagler; J.W. Negele; K. Orginos; A.V. Pochinsky; D.B. Renner; D.G. Richards; W. Schroers

2006-07-23

229

Nuclear energy density functional from chiral pion-nucleon dynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We calculate the nuclear energy density functional relevant for N=Z even-even nuclei in the systematic framework of chiral perturbation theory. The calculation includes the one-pion exchange Fock diagram and the iterated one-pion exchange Hartree and Fock diagrams. From these few leading order contributions in the small momentum expansion one obtains already a very good equation of state of isospin symmetric nuclear matter. We find that in the region below nuclear matter sat...

Kaiser, N.; Fritsch, S.; Weise, W.

2002-01-01

230

Nuclear energy density functional from chiral pion-nucleon dynamics revisited  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from $1\\pi$-exchange, iterated $1\\pi$-exchange, and irreducible $2\\pi$-exchange with intermediate $\\Delta$-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass $M^*(\\rho)$ entering the energy density ...

Kaiser, N.; Weise, W.

2009-01-01

231

The advanced nucleon electromagnetic structure model and prediction of hyperon electromagnetic form factors  

Energy Technology Data Exchange (ETDEWEB)

The advanced Unitary and Analytic model of electromagnetic structure of nucleons is applied for sophisticated prediction of hyperon electromagnetic form factors in space-like and time-like regions simultaneously. The static parameters of hyperons are predicted and compared with chiral perturbation theory calculations.

Bartoš, E., E-mail: erik.bartos@savba.sk [Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 84511 Bratislava (Slovakia); Dubni?ka, S., E-mail: stanislav.dubnicka@savba.sk [Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 84511 Bratislava (Slovakia); Dubni?ková, A.-Z., E-mail: dubnicka@fmph.uniba.sk [FMPI Comenius University, Mlynská dolina, 84248 Bratislava (Slovakia)

2013-12-15

232

Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces  

Energy Technology Data Exchange (ETDEWEB)

A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading-order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value A({rho}{sub 0}) {approx_equal} 26.5 MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar coupling terms and in the relevant density range one finds agreement with phenomenological Skyrme forces. The specific isospin and density dependences arising from the chiral two- and three-nucleon interactions can be explored and tested in neutron-rich systems. (orig.)

Kaiser, N. [Technische Universitaet Muenchen, Physik Department T39, Garching (Germany)

2012-03-15

233

Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces  

International Nuclear Information System (INIS)

A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading-order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value A(?0) ? 26.5 MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar coupling terms and in the relevant density range one finds agreement with phenomenological Skyrme forces. The specific isospin and density dependences arising from the chiral two- and three-nucleon interactions can be explored and tested in neutron-rich systems. (orig.)

2012-03-01

234

Magnetic electron scattering and valence nucleon radial wave functions  

International Nuclear Information System (INIS)

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

1982-01-01

235

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

CERN Multimedia

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 $N^\\star(1535)$, the parity partner of the nucleon. These results show a stronger deviation from the asymptotic form.

Warkentin, N; Göckeler, M; Kaltenbrunner, T; Schäfer, A; Schierholz, G; Nakamura, Y; Pleiter, D; Horsley, R; Zanotti, J M; Rakow, P E L; Stüben, H

2008-01-01

236

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

237

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.)

2008-07-14

238

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

239

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

240

Nuclear energy density functional from chiral pion-nucleon dynamics revisited  

CERN Document Server

We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from $1\\pi$-exchange, iterated $1\\pi$-exchange, and irreducible $2\\pi$-exchange with intermediate $\\Delta$-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass $M^*(\\rho)$ entering the energy density functional is identical to the one of Fermi-liquid theory when employing the improved density-matrix expansion. The strength $F_\

Kaiser, N

2009-01-01

 
 
 
 
241

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

1995-01-01

242

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

243

Structure functions and quark distributions in nuclens and nuclei  

International Nuclear Information System (INIS)

The data obtaned in the course of studying quark distribution in nucleons and nuclei are discussed. The results of measuring the R(x, Q"2) parameter which is determined through the relation of structure functions are considered. The experiments on studying nuclear effects in nucleon structure functions are analyzed. It is pointed out that the EMC effect, lepton-nucleus and hadron-nucleus interactions indicate the existence in nuclei of multiquark states. The data on structure functions determined from deep inelastic muon and neutrino scattering on nuclei are given

1985-07-00

244

Structure Functions at Low Q^2: Target Mass Corrections  

Energy Technology Data Exchange (ETDEWEB)

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

Wally Melnitchouk

2007-05-30

245

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

1979-07-20

246

Studies of partonic transverse momentum and spin structure of the nucleon  

Energy Technology Data Exchange (ETDEWEB)

The investigation of the partonic degrees of freedom beyond collinear approximation (3D description) has been gained increasing interest in the last decade. The Thomas Jefferson National Laboratory, after the CEBAF upgrade to 12 GeV, will become the most complete facility for the investigation of the hadron structure in the valence region by scattering of polarized electron off various polarized nucleon targets. A compendium of the planned experiments is here presented.

Contalbrigo, Marco M. [INFN, Ferrara, Italy

2014-06-01

247

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

248

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

Energy Technology Data Exchange (ETDEWEB)

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments {sub u-d}/{sub {Delta} u - {Delta} d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is about 1.6 GeV and the spatial volume is about (3.0 fm){sup 3}. Even with preliminary statistics of 25-30 gauge configurations, the ratios g{sub A}/g{sub V} and {sub u-d}/{sub {Delta} u - {Delta} d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d{sub 1}, though yet to be renormalized, appears small in both sets.

Huey-Wen Lin; Shigemi Ohta

2006-07-23

249

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

Energy Technology Data Exchange (ETDEWEB)

We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments {sub u-d}/{sub {Delta}u-{Delta}d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is a{sup -1} {approx} 1.6GeV and the spatial volume is about (3.0fm){sup 3}. Even with preliminary statistics of 25-30 gauge configurations, the ratios g{sub A}/g{sub V} and {sub u-d}/{sub {Delta}u-{Delta}d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d{sub 1}, though yet to be renormalized, appears small in both sets.

LIN H.-W.; OHTA, S.

2006-10-02

250

Vector and tensor polarizations in e{sup +}e{sup ?}?pp{sup ¯} by advanced nucleon electromagnetic structure model  

Energy Technology Data Exchange (ETDEWEB)

Recently an advanced nucleon electromagnetic structure model has been developed and in this paper predictions of vector and tensor polarizations in e{sup +}e{sup ?}?pp{sup ¯} process by this model are presented.

Dubnickova, Anna Zuzana [Dept. of Theoretical Physics, Comenius University, Bratislava (Slovakia); Dubnicka, Stanislav; Adamuscin, Cyril [Institute of Physics, Slovak Academy of Sciences, Bratislava (Slovakia)

2013-12-15

251

Isovector part of nuclear energy density functional from chiral two- and three-nucleon forces  

CERN Multimedia

A recent calculation of the nuclear energy density functional from chiral two- and three-nucleon forces is extended to the isovector terms pertaining to different proton and neutron densities. An improved density-matrix expansion is adapted to the situation of small isospin-asymmetries and used to calculate in the Hartree-Fock approximation the density-dependent strength functions associated with the isovector terms. The two-body interaction comprises of long-range multi-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition, the leading order chiral three-nucleon interaction is employed with its parameters fixed in computations of nuclear few-body systems. With this input one finds for the asymmetry energy of nuclear matter the value $A(\\rho_0) \\simeq 26.5\\,$MeV, compatible with existing semi-empirical determinations. The strength functions of the isovector surface and spin-orbit coupling terms come out much smaller than those of the analogous isoscalar...

Kaiser, N

2012-01-01

252

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

1979-11-01

253

Progress in resolving charge symmetry violation in nucleon structure  

CERN Document Server

Recent work unambiguously resolves the level of charge symmetry violation in moments of parton distributions using 2+1-flavor lattice QCD. We introduce the methods used for that analysis by applying them to determine the strong contribution to the proton-neutron mass difference. We also summarize related work which reveals that the fraction of baryon spin which is carried by the quarks is in fact structure-dependent rather than universal across the baryon octet.

Young, R D; Thomas, A W

2013-01-01

254

Polarized structure functions up to collider energies  

International Nuclear Information System (INIS)

A new set of spin-dependent structure functions for quarks and gluons inside a polarized nucleon is presented. This is the only available set which satisfies all the sum rules and analytic requirements and is valid in the kinematic range 10-5?x?0.9 and 5?Q2?5x108 GeV2, the effects of heavier flavours being taken into account. (orig.)

1987-01-08

255

Nuclear structure with accurate chiral perturbation theory nucleon-nucleon potential: Application to 6Li and 10B  

Energy Technology Data Exchange (ETDEWEB)

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

Navratil, P; Caurier, E

2003-10-14

256

Distribution Functions of the Nucleon and Pion in the Valence Region  

CERN Multimedia

We provide an experimental and theoretical perspective on the behavior of unpolarized distribution functions for the nucleon and pion on the valence-quark domain; namely, Bjorken-x \\gtrsim 0.4. This domain is key to much of hadron physics; e.g., a hadron is defined by its flavor content and that is a valence-quark property. Furthermore, its accurate parametrization is crucial to the provision of reliable input for large collider experiments. We focus on experimental extractions of distribution functions via electron and muon inelastic scattering, and from Drell-Yan interactions; and on theoretical treatments that emphasize an explanation of the distribution functions, providing an overview of major contemporary approaches and issues. Valence-quark physics is a compelling subject, which probes at the heart of our understanding of the Standard Model. There are numerous outstanding and unresolved challenges, which experiment and theory must confront. In connection with experiment, we explain that an upgraded Jef...

Holt, Roy J

2010-01-01

257

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

CERN Document Server

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

Bekzhanov, A V; Burov, V V

2014-01-01

258

The form factors of the nucleons  

International Nuclear Information System (INIS)

The study of the electromagnetic form factors of the nucleons are of fundamental importance in understanding nucleon structure. The form factors contain all the information about the deviation from pointlike structure of the charge and magnetization current distributions of the nucleons. The hope is that measurements at sufficiently large momentum transfers can provide a microscopic understanding of the nucleon wave functions in terms of their constituent quark amplitudes. Recent measurements of the electric G_E(Q"2) and magnetic G_M(Q"2) form factors of the nucleons are reviewed and compared to theoretical calculations based on non-perturbative QCD sum rules, diquark, relativistic constituent quark, and vector meson dominance (VMD) models. A short summary of ongoing and future measurements is also presented

1993-07-05

259

Nucleon and nucleon-pair momentum distributions in A ?12 nuclei  

Science.gov (United States)

Background: Momentum distributions of individual nucleons and nucleon pairs reflect features of the short-range structure of nuclei and provide useful insights into various reactions on nuclei, such as (e,e'p) and (e,e'pp/pn) electrodisintegration processes or neutrino-nucleus interaction experiments. Purpose: To provide the nuclear physics community with the results (available online) of a systematic study of single-nucleon momentum distributions and nucleon-pair and nucleon-cluster momentum distributions for A ?12 nuclei. Method: The realistic Argonne v18 two-nucleon and Urbana X three-nucleon potentials are used to generate accurate variational Monte Carlo wave functions for the A ?12 nuclei; quantum Monte Carlo methods are used to calculate the momentum distributions. Results: Single-nucleon distributions are given, broken down into proton and neutron components and spin-up and spin-down components where appropriate. Nucleon-pair momentum distributions are given either in pair spin and isospin ST projection or for pp, pn, and nn pairs. Nucleon-cluster momentum distributions include dp in 3He, tp and dd in 4He, ?d in 6Li, ?t in 7Li, and ?? in 8Be. Conclusions: The momentum distributions exhibit common characteristic shapes, with tensor correlations (or lack thereof) playing a dominant role in the 1.5-3 fm-1 range, while spin-isospin correlations dominate at higher momenta.

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

2014-02-01

260

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

 
 
 
 
261

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

Energy Technology Data Exchange (ETDEWEB)

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. (orig.)

Anselmino, M. (Dipt. di Fisica Teorica, Univ. di Torino and Ist. Nazionale di Fisica Nucleare, Sezione di Torino (Italy)); Gambino, P. (Dept. of Physics, New York Univ., NY (United States)); Kalinowski, J. (Univ. of Warsaw, Inst. of Theoretical Physics, Warsaw (Poland))

1994-10-01

262

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

CERN Multimedia

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

263

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

264

Hadron Structure from Lattice QCD  

Energy Technology Data Exchange (ETDEWEB)

The structure of neutrons, protons, and other strongly interacting particles is now being calculated in full, unquenched lattice QCD with quark masses entering the chiral regime. This talk describes selected examples, including the nucleon axial charge, structure functions, electromagnetic form factors, the origin of the nucleon spin, the transverse structure of the nucleon, and the nucleon to Delta transition form factor.

Robert Edwards; David Richards

2006-02-01

265

Moments of Spin Structure Functions: Sum Rules and Polarizabilities  

CERN Document Server

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

Chen, Jian-ping

2010-01-01

266

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Fomin, N.; Arrington, J.; 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.

2011-01-01

267

Nucleon quark distributions in a covariant quark-diquark model  

CERN Multimedia

Spin-dependent and spin-independent quark light-cone momentum distributions and structure functions are calculated for the nucleon. We utilize a modified Nambu-Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. We find excellent agreement between our model results and empirical data.

Cloet, I C; Thomas, A W

2005-01-01

268

Structure functions of nuclei in the pion exchange model  

International Nuclear Information System (INIS)

A detailed derivation is presented of the fact that the deep inelastic structure function of a nucleus may be expressed directly in terms of the empirical structure functions of the constituent nucleons and mesons and the wave function of the nuclear bound state. The assumptions made are specified. The pion exchange model provides a unified quantitative description for all x of nuclear effects observed in deep inelastic scattering of charged and neutral leptons from nuclei

1985-01-01

269

The ground and excited states structure of a few-nucleon system in Gaussian representation  

International Nuclear Information System (INIS)

Complete text of publication follows. For three- and four-body bound systems with strong interaction, cluster and 'halo'-type effects are studied. The energy spectrum and wave functions of three- and four-nucleon systems are calculated with high precision for various NN-interaction potentials of different form with the use of the Gaussian representation of the variational method. The Efimov effect region is studied. Realistic NN-interaction potentials are considered for complete study of the nuclei T, "3He, and "4He properties (1). Convergence of the method with respect to the basis dimension extension is analyzed. Procedures are proposed to optimize the variational basis in order to achieve high precision in calculations with minimum number of the basis components. Nucleon density distributions, formfactors, momentum distributions, and pair correlation functions are calculated with high accuracy both for the ground and possible excited states. Degree of clusterization of the ground and excited states is analyzed. The 'halo' effect is shown to take place in the systems of three and four strongly interacting particles in the excited states near the threshold. The above effect manifests itself in the density distribution as a long-range peripheral part of less intensity in comparison with the central core. In respective formfactors of the excited states, a specific additional dip of a finite value is revealed at small momentum transfers related to the long-range region. (author)

2000-05-15

270

Lattice Operators for Moments of the Structure Functions and their Transformation under the Hypercubic Group  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For lattice operators that are relevant to the calculation of moments of nucleon structure functions we investigate the transformation properties under the hypercubic group. We give explicit bases of irreducible subspaces for tensors of rank up to 4.

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

1996-01-01

271

Extraction of neutron structure from tagged structure functions  

CERN Document Server

We present work in a model used to describe semi-inclusive deep inelastic scattering off the deuteron. The model uses the virtual nucleon approximation to describe the interaction of the photon with the bound neutron and the generalized eikonal approximation is applied to calculate the final-state interaction diagram. Comparison with data taken at Jefferson Lab shows good agreement in the covered range of kinematics and points at a largely suppressed off-shell rescattering amplitude. The $W$ and $Q^2$ dependences of the total cross section and slope factor of the interaction of DIS products, $X$, off the spectator nucleon are extracted. Starting from the JLab data and our model calculations, we outline and apply an extrapolation method to obtain the neutron structure function $F_{2N}$ at high Bjorken $x$.

Cosyn, Wim

2011-01-01

272

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

273

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 Q"2. In conclusion, all the tests of QCD are tabulated, and the results are evaluated. 32 references, 33 figures, 4 tables

1979-01-01

274

Nucleon models  

International Nuclear Information System (INIS)

Theoretical models for the structure of the nucleons and the hyperons are constructed for the purpose of obtaining an understanding of the dynamics that gives rise to their complex spectra. The most modest goal is to explain the ground state energies and the corresponding static observables - magnetic moments and rms radii. More ambitious models attempt in addition to explain the dynamic observables as, e.g., the electromagnetic form factors, which requires that not only overall features are understood, but that at least some parts of the short-range dynamics are understood as well. The rich structure of the baryon spectrum, with 5 known successive flavor generations [the nucleons (up and down quarks), the strange, the charmed and the bottom hyperons] makes the construction of a realistic nucleon model a complex task. Naturally, if it were possible, one would like to take the Lagrangian density of quantum chromodynamics as the starting point. This is formed of quark and gluon field operators. While the mass scale of the baryons is 1 GeV, that of the light u and d quarks and the gluons is essentially 0 (mu congruent 5 MeV, md congruent 8 MeV, mgluon = 0). That baryons with masses of the order of 1 GeV or more can be formed of such light constituents is a consequence of the very strong gluon exchange interaction at low energies. The topics covered in this report are: Chiral Symmetry; The Chiral Bag Model; Chiral Meson Theory; The Skyrmion; Currents and Form Factors; The Skyrme Model and the Chiral Bag Model; Extensions of the Model; Explicit Vector Meson Fields; The Hyperons; The Hyperon Spectrum; The Hyperon Magnetic Moments; Exotics; The Limits of the Bound State Model; and The End of the Nucleon Models

1996-01-01

275

Nucleon-nucleon data  

Energy Technology Data Exchange (ETDEWEB)

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work completes the determination of the nucleon-nucleon (NN) scattering amplitudes from 485 to 800 MeV. The data set is completed by the publication of two papers. These new data have a precision better than 1% and an absolute accuracy about 1%, which is generally an order of magnitude better than previous data. The NN data set is now complete and consistent. The set of spin-dependent NN-scattering amplitudes is now well determined up to 800 MeV.

McNaughton, M.W. [Los Alamos National Lab., NM (United States); Gulmez, E.; Whitten, C.A. [Univ. of California, Los Angeles, CA (United States)] [and others

1997-10-01

276

Sea and gluon spin structure function measurements at RHIC  

Energy Technology Data Exchange (ETDEWEB)

The first polarized collider where one collides 250-GeV/c beams of 70% polarized protons at high luminosity is under construction. This will allow a determination of the nucleon spin-dependent structure functions over a large range in x and a collection of sufficient W and Z events to investigate extremely interesting spin-related phenomena.

Yokosawa, A.

1995-02-01

277

Microscopic relativistic nucleon-nucleus inelastic scattering  

Energy Technology Data Exchange (ETDEWEB)

We formulate a microscopic relativistic treatment of nucleon-nucleus inelastic scattering. Both the continuum and bound state single nucleon wave functions are obtained by solving the Dirac equation with scalar and timelike vector potentials. The interaction which drives the transition is expressed in terms of invariant combinations of Dirac matrices. The structure of the resulting amplitudes is presented, and certain of their features, such as selection rules, are discussed.

Shepard, J.R.; Rost, E.; Piekarewicz, J.

1984-11-01

278

New method for extracting neutron structure functions from nuclear data  

CERN Document Server

We propose a new method for extracting neutron structure functions from inclusive structure functions of nuclei. Unlike earlier approaches, the new method is applicable to both spin-averaged and spin-dependent structure functions. We test the reliability of the method on unpolarized F_2 and polarized g_1 structure functions of the deuteron in both the nucleon resonance and deep inelastic regions. The new method is able to reproduce known input functions of almost arbitrary shape to very good accuracy with only several iterations.

Kahn, Yonatan; Kulagin, S A

2008-01-01

279

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

1984-01-01

280

Electromagnetic Polarisabilities of the Nucleon.  

Science.gov (United States)

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...

A. M. Harun ar Rashid

1982-01-01

 
 
 
 
281

Nucleon-nucleon force and the quark degrees of freedom  

International Nuclear Information System (INIS)

This review gives a detailed overview of the current status of our understanding of the nucleon-nucleon forces. The authors review the known long-range meson exchange forces and explain how these forces originate from an underlying quark model constrained by chiral symmetry, a symmetry that is very well satisfied in low-energy nuclear phenomena. These effective meson exchange forces describe the large-impact-parameter nucleon-nucleon scattering. The authors show how the small-impact-parameter nucleon-nucleon scattering can be explained by the quark structure of the nucleons and why this quark model is successful in reproducing the energy dependence of the ''measured'' S- and P-wave nucleon-nucleon phase shifts

1988-01-01

282

The partonic structure of the nucleon from generalized transverse momentum-dependent parton distributions  

CERN Document Server

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

Pasquini, B

2013-01-01

283

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

284

Treatment of Two Nucleons in Three Dimensions  

Directory of Open Access Journals (Sweden)

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

Glöckle W.

2010-04-01

285

Nucleon spin summary  

CERN Multimedia

This talk summarises the discussions during the conference on the spin structure of the nucleon held at Erice; July 1995. The summary focuses on where we have come, where we are now, and the emerging questions that direct where we go next in the quest to understand the nucleon spin.

Close, Francis Edwin

1995-01-01

286

Calculation of ? structure function  

International Nuclear Information System (INIS)

The calculation of structure function of ? particle is carried out at three energies, namely 0.957, 1.005 and 1.065 GeV in the range of Q2 =0.1 to 0.3 (GeV/c)2 by using the Rosenbluth separation technique in ? electroproduction. The functional dependency of form factor and structure function to the Q2 is investigated via separated cross sections ? L and ? T

2004-04-27

287

Nucleon Electromagnetic Form Factors  

International Nuclear Information System (INIS)

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

2004-09-01

288

Nucleon Electromagnetic Form Factors  

Energy Technology Data Exchange (ETDEWEB)

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

Kees de Jager

2004-08-01

289

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

290

Neutron structure functions  

International Nuclear Information System (INIS)

Neutron structure functions can be extracted from proton and deuteron data and a representation of the deuteron structure. This procedure does not require DIS approximations or quark structure assumptions. We find that the results depend critically on properly accounting for the Q2 dependence of proton and deuteron data. We interpolate the data to fixed Q2, and extract the ratio of neutron to proton structure functions. The extracted ratio decreases with increasing x, up to x ? 0.9, while there are no data available to constrain the behavior at larger x

2009-02-02

291

Neutron structure functions.  

Energy Technology Data Exchange (ETDEWEB)

Neutron structure functions can be extracted from proton and deuteron data and a representation of the deuteron structure. This procedure does not require DIS approximations or quark structure assumptions. We find that the results depend critically on properly accounting for the Q{sup 2} dependence of proton and deuteron data. We interpolate the data to fixed Q{sup 2}, and extract the ratio of neutron to proton structure functions. The extracted ratio decreases with increasing x, up to x {approx} 0.9, while there are no data available to constrain the behavior at larger x.

Arrington, J.; Coester, F.; Holt, R. J.; Lee, T.-S. H.; Physics

2009-01-01

292

Neutron Structure Functions  

CERN Document Server

Neutron structure functions can be extracted from proton and deuteron data and a representation of the deuteron structure. This procedure does not require DIS approximations or quark structure assumptions. We find that the results depend critically on properly accounting for the Q^2 dependence of proton and deuteron data. We interpolate the data to fixed Q^2, and extract the ratio of neutron to proton structure functions. The extracted ratio decreases with increasing x, up to x \\approx 0.9, while there are no data available to constrain the behavior at larger x.

Arrington, J; Holt, R J; Lee, T -S H

2008-01-01

293

Study of nuclear structure and the nucleon-nucleon interaction in quasielastic scattering of electrons by 3He  

International Nuclear Information System (INIS)

We describe the technique and present the results of a study of the reaction 3He (e,e'p) for primary energies E/sub i/ = 806 and 643 MeV and electron scattering angles theta/sub e/ = 31 and 280 with energy resolution 4 and 2.6 MeV, respectively. The angular distributions (theta/sub p/ = 47.5--72.50 and 54--720) and momentum distributions (q/sub R/ = +- 100 MeV/c) of protons for two-particle and three-particle disintegration of 3He are compared with model and exact calculations with use of various wave functions of the 3He ground state. It is shown that the angular and momentum distributions obtained are best described by a model calculation with use of the Irving wave function and the exact calculation with the Yamaguchi potential and the Tabakin parameters

1982-04-01

294

EM vs Weak Structure Functions in DIS processes  

CERN Multimedia

We obatin the ratio $F_i^A/F_i^{D}$(i=2,3, A=Be, C, Fe, Pb; D=Deuteron) in the case of weak and electromagnetic nuclear structure functions. For this, relativistic nuclear spectral function which incorporate the effects of Fermi motion, binding and nucleon correlations is used. We also consider the pion and rho meson cloud contributions and shadowing and antishadowing effects.

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

2013-01-01

295

Deuteron spin structure functions in the resonance and DIS regions  

CERN Document Server

We derive relations between spin-dependent nuclear and nucleon g_1 and g_2 structure functions, valid at all Q^2, and in both the resonance and deep inelastic regions. We apply the formalism to the specific case of the deuteron, which is often used as a source of neutron structure information, and compare the size of the nuclear corrections calculated using exact kinematics and using approximations applicable at large Q^2.

Kulagin, S A

2007-01-01

296

Deuteron Spin Structure Functions in the Resonance and DIS Regions  

Energy Technology Data Exchange (ETDEWEB)

We derive relations between spin-dependent nuclear and nucleon g_1 and g_2 structure functions, valid at all Q^2, and in both the resonance and deep inelastic regions. We apply the formalism to the specific case of the deuteron, which is often used as a source of neutron structure information, and compare the size of the nuclear corrections calculated using exact kinematics and using approximations applicable at large Q^2.

S. Kulagin; W. Melnitchouk

2007-10-03

297

L-dependence in the 6Li induced three nucleon transfer excitation function  

International Nuclear Information System (INIS)

The three nucleon transfer reactions induced by 6Li on 12C were studied from 5 to 9 MeV/n. The bell-shaped energy variation is used to select cluster states of progressively higher angular momentum. A modification to the Brink semi-classical model equations is proposed in order to reproduce the observed features

1980-01-01

298

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

299

Formation of a necklike structure in 35Cl+12C and 197Au reactions at 43 MeV/nucleon  

International Nuclear Information System (INIS)

The experimental signature of the formation of a necklike structure, with a velocity between that of the projectilelike emitter and that of the targetlike emitter, is investigated with the same beam and experimental setup for targets lighter and heavier than the projectile. The reactions are 35Cl on 12C and on 197Au at 43 MeV/nucleon. Particle velocity distributions are compared with two-source statistical simulations and the presence of a necklike structure is inferred from the data. In the second part of the paper, dynamical model simulations with the formation of a necklike structure are presented for the 35Cl+12C system at 43 MeV/nucleon. copyright 1997 The American Physical Society

1997-04-01

300

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

 
 
 
 
301

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

302

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

International Nuclear Information System (INIS)

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

1980-11-03

303

Wave functions of few nucleon systems related to deuteron induced reactions  

International Nuclear Information System (INIS)

The authors have solved the Faddeev equation for triton with realistic two nucleon potentials; the Argonne (AV), the super soft core (TRS) and the Paris (PARIS) potentials, together with the Tucson-Melbourne (TM) three-nucleon potential. They found a linear relationship between the ratio C/sub 2//C/sub o/ for the asymptotic normalization constants of /sup 3/H ? d + n and the binding energy of triton. The 26 channel calculation for AV + TM (TRS + TM, PARIS + TM) with the dipole ?NN form factor with the cutoff momentum of 700MeV/c for TM yields 8.33 (8.41,8.24) MeV for the binding energy of triton and C/sub 2//C/sub o/ = 0.0439 (0.0426,0.0435)

1986-01-01

304

Solidification of nucleon system and ?0 condensation  

International Nuclear Information System (INIS)

Solidification and ?0 condensation in nuclear medium are studied in a unified way by adopting the pion-nucleon P-wave interaction. It is shown that the one-dimensional localization with an alternating-layer-spin [ALS] structure is realized as the first-order effect of the strong OPEP-tensor force and the ?0 condensed field comes into existence owing to the source function provided by the [ALS] structure. This new phase shows up in remarkable localization and the resulting spin-density periodicity. The energy gain from the Fermi gas is obtained due to the condensation energy overwhelming the increase of nucleon kinetic energy caused by localization. (author)

1977-09-10

305

The nucleon-nucleon collision profile and cross section fluctuations  

Science.gov (United States)

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

Rybczy?ski, Maciej; W?odarczyk, Zbigniew

2014-01-01

306

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

307

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

Directory of Open Access Journals (Sweden)

Full Text Available We summarize our recent work dealing with the construction of the nucleon-nucleon potential and associated electromagnetic currents up to one loop in chiral e?ective ?eld theory (?EFT. The magnetic dipole operators derived from these currents are then used in hybrid calculations of static properties and low-energy radiative capture processes in few-body nuclei. A preliminary set of results are presented for the magnetic moments of the deuteron and trinucleons and thermal neutron captures on p, d, and 3He.

Schiavilla R.

2010-04-01

308

A nuclear structure approach to the nucleon-nucleus optical potential at low energy  

International Nuclear Information System (INIS)

An antisymmetrized microscopic calculation of the optical potential for nucleon-"4"0Ca elastic scattering is derived. RPA correlations taken into account in the one-particle mass operator are shown to bring a correction to the first order real potential at low energies and to lead to an imaginary potential. Both are calculated for incident nucleon energies between 10 and 50 MeV. Their general properties are studied in great details and after comparison with empirical imaginary potentials the reliability of such an approach is discussed according to the value of the incident energy

1981-01-01

309

Evaluation of Migdal jump in momentum distribution of nucleons in nuclear matter in terms of nuclear response function  

International Nuclear Information System (INIS)

Renormalization factor Z0 of the single-particle Green function in nuclear matter, which is equal to the jump in momentum distribution of nucleons (so-called Migdal jump), is evaluated by using a dispersion relation for the mass operator ?. Within realistic for nuclear physics approximations, an exact many-body theory relation for ? is transformed to a form which makes it possible to evaluate Z0 in terms of the nuclear response function. It is shown that the spin-isospin mode of the response function produces a dominant contribution to Z0. Properties of this mode are governed by the Landau-Migdal amplitude g'0, as well as by the tensor one-pion and ?-meson exchange amplitudes. Within realistic assumptions for form of these amplitudes, one succeeds in approximate reproducing of the experimental value of Z0 = 0.8, which is known in the self-consistent Finite Fermi Systems theory

1999-08-01

310

Parton and valon distributions in the nucleon  

Energy Technology Data Exchange (ETDEWEB)

Structure functions of the nucleon are analyzed in the valon model in which a nucleon is assumed to be a bound state of three valence quark clusters (valons). At high Q/sup 2/ the structure of the valons is described by leading-order results in the perturbative quantum chromodynamics. From the experimental data on deep-inelastic scattering off protons and neutrons, the flavor-dependent valon distributions in the nucleon are determined. Predictions for the parton distributions are then made for high Q/sup 2/ without guesses concerning the quark and gluon distributions at low Q/sup 2/. The sea-quark and gluon distributions are found to have a sharp peak at very small x. Convenient parametrization is provided which interpolates between different numbers of flavors.

Hwa, R.C.; Sajjad Zahir, M.

1981-06-01

311

Lattice DIS Structure Functions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the computation, in lattice QCD, of the renormalization constants and mixing coefficients of operators that measure the first two moments of DIS Structure Functions. These calculations have been performed using the Sheikholeslami-Wohlert O(a) improved ``clover'' action, which is known to reduce the systematic error associated with the finiteness of the lattice spacing a. Due to the complexities of the computations, we have developed, using the computer languages S...

Capitani, Stefano

1996-01-01

312

Parton promenade into the nucleon  

CERN Document Server

Generalized parton distributions (GPDs) offer a comprehensive picture of the nucleon structure and dynamics and provide a link between microscopic and macroscopic properties of the nucleon. These quantities, which can be interpreted as the transverse distribution of partons carrying a certain longitudinal momentum fraction of the nucleon can be accessed in deep exclusive processes. This lecture reviews the main features of the nucleon structure as obtained from elastic and inelastic lepton scatterings and unified in the context of the GPDs framework. Particular emphasis is put on the experimental methods to access these distributions and the today experimental status.

Voutier, E

2009-01-01

313

Tests of Duality in the Spin-Structure Function g1  

International Nuclear Information System (INIS)

Although quark-hadron duality is well established for the spin-independent structure function, F2p, hardly any information is available on the low Q2 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 Q2 values above ? 2 (GeV/c)2

2006-11-17

314

Clustering aspects in nuclear structure functions  

International Nuclear Information System (INIS)

For understanding an anomalous nuclear effect experimentally observed for the beryllium-9 nucleus at the Thomas Jefferson National Accelerator Facility, clustering aspects are studied in structure functions of deep inelastic lepton-nucleus scattering by using momentum distributions calculated in antisymmetrized (or fermionic) molecular dynamics (AMD) and also in a simple shell model for comparison. According to AMD, the 9Be nucleus consists of two ?-like clusters with a surrounding neutron. The clustering produces high-momentum components in nuclear wave functions, which affects nuclear modifications of the structure functions. We investigated whether clustering features could appear in the structure function F2 of 9Be along with studies for other light nuclei. We found that nuclear modifications of F2 are similar in both AMD and shell models within our simple convolution description although there are slight differences in 9Be. It indicates that the anomalous 9Be result should be explained by a different mechanism from the nuclear binding and Fermi motion. If nuclear-modification slopes d(F2A/F2D)/dx are shown by the maximum local densities, the 9Be anomaly can be explained by the AMD picture, namely by the clustering structure, whereas it certainly cannot be described in the simple shell model. This fact suggests that the large nuclear modification in 9Be should be explained by large densities in the clusters. For example, internal nucleon structure could be modified in the high-density clusters. The clustering aspect of nuclear structure functions is an unexplored topic which is interesting for future investigations.

2011-03-01

315

A thermal model for the strangeness in nucleon  

International Nuclear Information System (INIS)

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

1996-04-15

316

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)

1995-01-01

317

Relativistic nucleon  

International Nuclear Information System (INIS)

It is noted that the pion and vector meson fields of the relativistic nucleon behave in different ways. The contribution of the vector meson field increases with increasing energy and becomes dominating at ?>or approx. 10"2(? is the Lorentz factor). This leads to the growth of the transverse size for the nucleon. As a result, the character of peripheral and central collision changes (the former is determined by vector exchange). The cross section of ? and ? production increases. A significant contribution to the spin effect is expected. The opinion is expressed that the indicated growth of the transverse size of the nucleon leads to increasing the total cross section of nucleon interaction at high energy. 9 refs.; 3 figs.; 1 tab

1990-01-01

318

Spin and angular momentum in the nucleon  

CERN Document Server

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.

Gross, Franz; Pena, M T

2012-01-01

319

Lattice DIS Structure Functions  

CERN Multimedia

We present the computation, in lattice QCD, of the renormalization constants and mixing coefficients of operators that measure the first two moments of DIS Structure Functions. These calculations have been performed using the Sheikholeslami-Wohlert O(a) improved ``clover'' action, which is known to reduce the systematic error associated with the finiteness of the lattice spacing a. Due to the complexities of the computations, we have developed, using the computer languages Schoonschip and Form, general codes that are able to automatically carry out all the analytic lattice manipulations.

Capitani, S

1996-01-01

320

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

 
 
 
 
321

Coupling of unpaired nucleons and collective band level structure in odd-odd nuclei  

International Nuclear Information System (INIS)

The phenomenological approximation can be used for calculation energies of collective bands in odd-odd nuclei based on conflicting state of unpaired nucleons. The rule of decoupled particle as a spectator have been deduced. This mean that the energy spacing of collective bands in odd-odd nuclei are similar for energy spacing of collective bands based on state of coupled particle in adjacent odd nuclei. 44 refs.; 8 figs.; 2 tabs

1989-01-01

322

Coupled channels Marchenko inversion for nucleon-nucleon potentials  

International Nuclear Information System (INIS)

Marchenko inversion is used to determine local energy independent but channel dependent potential matrices from optimum sets of experimental phase shifts. 3SD1 and 3PF2 channels of nucleon-nucleon systems contain in their off-diagonal potential matrices explicitly the tensor force for T = 0 and 1 isospin. We obtain, together with single channels, complete sets of quantitative nucleon-nucleon potential results which are ready for application in nuclear structure and reaction analyses. The historic coupled channels inversion result of Newton and Fulton is revisited. (orig.)

1993-05-17

323

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

International Nuclear Information System (INIS)

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

1988-01-01

324

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

325

Hard probes of short-range nucleon-nucleon correlations  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-10-01

326

Semiphenomenological nucleon-nucleon potentials  

International Nuclear Information System (INIS)

A review is given of some of the properties of semiphenomenological nucleon-nucleon potentials. Special attention is paid to how they compare with low energy pp-polarization data and with phase shift analyses. Shown is that for all potentials holds, that the long and intermediate range parts of the I=1 tensorpotential are too strong, and of the I=1 spin-orbit potential are much too weak. (orig.)

1984-03-26

327

Do nucleon-nucleon collisions dominate nucleus-nucleus interactions  

International Nuclear Information System (INIS)

The 20Ne + 181Ta reaction cross section leading to products with A > 40 is compared with the nucleon-nucleon cross section as a function of projectile energy. No evidence for transparency in composite projectile-nucleus collisions is seen. 1 figure

1980-09-01

328

The nucleon-nucleon interaction  

International Nuclear Information System (INIS)

This book is based upon lectures given at the Niels Bohr Institute and NORDITA. In a general discussion of the interaction the authors detail the argument connecting the range of the nucleon-nucleon force and the mass of the exchanged meson, based on the uncertainty principle. The discussion of low-energy phenomena is begun with the neutron-proton system. The electromagnetic properties of the deuteron and its interaction with radiation are discussed. Proton-proton scattering and some results from scattering theory including the derivaton of the Lippman-Schwinger equation and the Low equation are considered. Modifications of the Lippmann-Schwinger equation necessitated by the kinematic requirements of relativity are considered. One-boson exchange contributions to the nucleon-nucleon interaction are discussed. The two-pion exchange interaction is considered. Finally the authors describe in some detail the results of calculations of NN phase shifts which incorporate essentially all of the techniques used in constructing field theoretic models of the nucleon-nucleon interaction which are described in this book. (B.R.H.)

1976-01-01

329

Investigation of the residues produced in 16O + 156Gd reaction at energies ? 4.3-6.1 MeV/nucleon: measurement of excitation functions  

International Nuclear Information System (INIS)

The excitation functions (EFs) of the various evaporation residues produced in the 16O + 156Gd system have been studied in the energy range ? 4.3-6.1 MeV/nucleon by using activation technique. The measured excitation of the evaporation residues have been compared with statistical model based computer codes PACE-2

2008-12-22

330

Spin structure functions: a window into the structure of hadrons  

International Nuclear Information System (INIS)

A large program of spin structure measurements is underway in Jefferson Lab's Hall B. Of particular interest is the first moment of the spin structure function g1, which goes through a rapid transition from the photon point (Q2 = 0), where it is constrained by the Gerasimov-Drell-Hearn sum rule, to the deep inelastic limit where it is sensitive to the nucleon spin fraction carried by quarks. One can then study the transition from hadronic to quark degrees of freedom over the whole range of Q2. It is also interesting to look for the onset of quark-hadron duality in spin structure functions. We use longitudinally polarized electrons with energies from 1.6 to 5.7 GeV incident upon polarized NH3 and ND3 targets to investigate proton and deuteron spin observables in and above the resonance region. We present the GDH and Bjorken integrals using the 1.6 and 5.7 GeV data and comment on the validity of local quark-hadron duality over the wide kinematical range (0.05 ? Q2 ? 4.5 GeV2 and W < 3.2)

2005-01-01

331

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

332

Sum rule measurements of the spin-dependent compton amplitude (nucleon spin structure at Q{sup 2} = 0)  

Energy Technology Data Exchange (ETDEWEB)

Energy weighted integrals of the difference in helicity-dependent photo-production cross sections ({sigma}{sub {1/2}} - {sigma}{sub 3/2}) provide information on the nucleon`s Spin-dependent Polarizability ({gamma}), and on the spin-dependent part of the asymptotic forward Compton amplitude through the Drell-Hearn-Gerasimov (DHG) sum rule. (The latter forms the Q{sup 2}=0 limit of recent spin-asymmetry experiments in deep-inelastic lepton-scattering.) There are no direct measurements of {sigma}{sub {1/2}} or {sigma}{sub 3/2}, for either the proton or the neutron. Estimates from current {pi}-photo-production multipole analyses, particularly for the proton-neutron difference, are in good agreement with relativistic-l-loop Chiral calculations ({chi}PT) for {gamma} but predict large deviations from the DHG sum rule. Either (a) both the 2-loop corrections to the Spin-Polarizability are large and the existing multipoles are wrong, or (b) modifications to the Drell-Hearn-Gerasimov sum rule are required to fully describe the isospin structure of the nucleon. The helicity-dependent photo-reaction amplitudes, for both the proton and the neutron, will be measured at LEGS from pion-threshold to 470 MeV. In these double-polarization experiments, circularly polarized photons from LEGS will be used with SPHICE, a new frozen-spin target consisting of {rvec H} {center_dot} {rvec D} in the solid phase. Reaction channels will be identified in SASY, a large detector array covering about 80% of 4{pi}. A high degree of symmetry in both target and detector will be used to minimize systematic uncertainties.

Babusci, D.; Giordano, G. [Laboratori Nationali di Frascati-INFN, Rome (Italy); Baghaei, H.; Cichocki, A. [Univ. of Virginia, Charlottesville, VA (United States); Blecher, M. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States); Breuer, M.; Commeaux, C.; Didelez, J.P. [IN2P3, Orsay (France); Caracappa, A. [Brookhaven National Lab., Upton, NY (United States); Fan, Q. [Syracuse Univ., NY (United States)] [and others

1995-12-31

333

DNA: Structure and function  

DEFF Research Database (Denmark)

This chapter discusses the structure and function of DNA. DNA occupies a critical role in cells, because it is the source of all intrinsic genetic information. Chemically, DNA is a very stable molecule, a characteristic important for a macromolecule that may have to persist in an intact form for a long period of time before its information is accessed by the cell. Although DNA plays a critical role as an informational storage molecule, it is by no means as unexciting as a computer tape or disk drive. The structure of the DNA described by Watson and Crick in 1953 is a right handed helix of two individual antiparallel DNA strands. Hydrogen bonds provide specificity that allows pairing between the complementary bases (A.T and G.C) in opposite strands. Base stacking occurs near the center of the DNA helix and provides a great deal of stability to the helix (in addition to hydrogen bonding). The sugar and phosphate groups form a â??backboneâ? on the outside of the helix. There are about 10 base pairs (bp) per turn ofthe double helix.

Sinden, Richard R.; E. Pearson, Christopher

1998-01-01

334

Semiphenomenological synthesis of meson and quark dynamics and the E.M. structure of the nucleon  

International Nuclear Information System (INIS)

We show that an extended vector dominance model which incorporates quark dynamics at large Q"2 via perturbative QCD gives an excellent description of existing data on elastic electron-proton/neutron cross-sections. Results of a simultaneous fit of the nucleon form factors Gsub(M,) sub(E)sup(p,) sup(n) to the cross-sections are given. Information is obtained about the QCD-scale parameter ?sub(QCD), as well as on the range of applicability of perturbative QCD calculations. Constraints on the hadronic wavefunctions are also obtained. (orig.)

1985-12-01

335

Nuclear medium modification of the F2 structure function  

CERN Document Server

We study the nuclear effects in the electromagnetic structure function $F_{2}(x, Q^2)$ in nuclei in the deep inelastic lepton nucleus scattering process by taking into account Fermi motion, binding, pion and rho meson cloud contributions. Calculations have been done in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations for nuclear matter. The ratios $R_{F2}^A(x,Q^2)=\\frac{2F_2^A(x,Q^2)}{AF_{2}^{Deut}(x,Q^2)}$ are obtained and compared with the recent JLAB results for light nuclei that show a non trivial A dependence.

Athar, M Sajjad; Vacas, M J Vicente

2009-01-01

336

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

337

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

338

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

1989-09-11

339

Determination of the pion structure function from muon-pair production  

International Nuclear Information System (INIS)

Data on muon-pair production by pions are used to determine the momentum distribution for valence quarks in the pion. The shape of a nucleon structure function is also obtained and is compared with a calculation based on existing data

1979-04-09

340

Target mass correction on the {sup 3}He polarized structure function  

Energy Technology Data Exchange (ETDEWEB)

Target mass correction (TMC) is employed to amend the polarized helium structure functions, {sup 3}He. The structure function can be obtained via the convolution of the light cone momentum distribution with the polarized structure of the proton and neutron. The calculation of the polarized structure function of the nucleon is based on the constituent quark model. The analytical result for {sup 3}He polarized structure function at low values of Q{sup 2} is not in good agreement with the available experimental data. The reliability of calculations is increased using TMC effect. New comparison confirms a better agreement with the experimental data. (orig.)

Mirjalili, A. [Yazd University, Physics Department, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of); Yazdanpanah, M.M. [Kerman Shahid Bahonar University, Physics Department, Kerman (Iran, Islamic Republic of)

2012-05-15

 
 
 
 
341

Spin structure of the nucleon: QCD evolution, lattice results and models  

CERN Document Server

The question how the spin of the nucleon is distributed among its quark and gluon constituents is still a subject of intense investigations. Lattice QCD has progressed to provide information about spin fractions and orbital angular momentum contributions for up- and down-quarks in the proton, at a typical scale \\mu^2~4 GeV^2. On the other hand, chiral quark models have traditionally been used for orientation at low momentum scales. In the comparison of such model calculations with experiment or lattice QCD, fixing the model scale and the treatment of scale evolution are essential. In this paper, we present a refined model calculation and a QCD evolution of lattice results up to next-to-next-to-leading order. We compare this approach with the Myhrer-Thomas scenario for resolving the proton spin puzzle.

Altenbuchinger, M; Weise, W; Henley, E M

2010-01-01

342

Correlation effects in single-particle overlap functions and one-nucleon removal reactions  

CERN Multimedia

Single-particle overlap functions and spectroscopic factors are calculated on the basis of the one-body density matrices (ODM) obtained for the nucleus $^{16}O$ employing different approaches to account for the effects of correlations. The calculations use the relationship between the overlap functions related to bound states of the (A-1)-particle system and the ODM for the ground state of the A-particle system. The resulting bound-state overlap functions are compared and tested in the description of the experimental data from (p,d) reactions for which the shape of the overlap function is important.

Gaidarov, M K; Dimitrova, S S; Stoitsov, M V; Antonov, A N; Van Neck, D; Müther, H

1999-01-01

343

Finite meson size effects in nucleon-nucleon phase shifts  

International Nuclear Information System (INIS)

A realistic quark model of the nucleon is used to determine the interaction between two nucleons. A scalar potential is utilized to confine the quarks and to determine the quark wave function by solving a Dirac equation. Chiral symmetry suggests that confined quarks are surrounded by a pion cloud. A local pion quark interaction is used to determine the energy of such a pion cloud with parameters chosen to reproduce the pion-nucleon coupling found in one-boson exchange potentials. For a finite pion size, the cloud energy is finite. The pion cloud energy is included in variational non-relativistic quark model determination of the nucleon mass. A stable nucleon of the right size and mass comes out of this calculation. The form factors for the one-boson exchange potential are calculated taking finite meson size into account. The OBEP is combined with a non-relativistic quark model of the nucleon to provide input into a resonating group theory to calculate the two nucleon phase shifts. The two nucleon "1S_0 phase shifts calculated agree well with experiment. The net effect of finite meson size in this model is a slightly smaller phase shift. (author)

1985-06-01

344

How well do we know the neutron structure function?  

Energy Technology Data Exchange (ETDEWEB)

We present a detailed analysis of the uncertainty in the neutron F{sub 2}n structure function extracted from inclusive deuteron and proton deep-inelastic scattering data. The analysis includes experimental uncertainties as well as uncertainties associated with the deuteron wave function, nuclear smearing, and nucleon off-shell corrections. Consistently accounting for the Q{sup 2} dependence of the data and calculations, and restricting the nuclear corrections to microscopic models of the deuteron, we find significantly smaller uncertainty in the extracted F{sub 2}n/F{sub 2}p ratio than in previous analyses. In addition to yielding an improved extraction of the neutron structure function, this analysis also provides an important baseline that will allow future, model-independent extractions of neutron structure to be used to examine nuclear medium effects in the the deuteron.

J. Arrington, J. G. Rubin, W. Melnitchouk

2012-06-01

345

How well do we know the neutron structure function?  

Science.gov (United States)

We present a detailed analysis of the uncertainty in the neutron F(2n) structure function extracted from inclusive deuteron and proton deep-inelastic scattering data. The analysis includes experimental uncertainties as well as uncertainties associated with the deuteron wave function, nuclear smearing, and nucleon off-shell corrections. Correctly accounting for the Q(2) dependence of the data and calculations and restricting the nuclear corrections to microscopic models of the deuteron, we find a significantly smaller uncertainty in the extracted F(2n)/F(2p) ratio than in previous analyses. In addition to yielding an improved extraction of the neutron structure function, this analysis also provides an important baseline that can be compared to future, model-independent extractions of neutron structure to examine nuclear medium effects in the deuteron. PMID:23004587

Arrington, J; Rubin, J G; Melnitchouk, W

2012-06-22

346

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

347

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.

2013-01-01

348

Structure functions at low Q^2: higher twists and target mass effects  

Energy Technology Data Exchange (ETDEWEB)

We review the physics of structure functions at low Q{sup 2}, focusing on the phenomenon of quark-hadron duality and the resonance-scaling transition, both phenomenologically and in the context of quark models. We also present a new implementation of target mass corrections to nucleon structure functions which, unlike existing treatments, has the correct kinematic threshold behavior at finite Q{sup 2} in the x -> 1 limit.

Wally Melnitchouk

2006-05-22

349

Spin structure functions at low Q2 from JLAB data  

International Nuclear Information System (INIS)

Spin structure functions of the nucleon in the region of large x and small to moderate Q2 continue to be of high current interest. Among the topics one can study in this kinematic regime are the Q2 evolution of the first moment of g1 and the behavior of the virtual photon asymmetry A1 at large x. A large experimental program to measure these observables for the proton and deuteron has been concluded at Jefferson Lab Hall B. We will present the results of the 1.6 and 5.7 GeV data. (author)

2007-01-01

350

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

351

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

352

Proposal to measure spin-structure functions and semi-exclusive asymmetries for the proton and neutron at HERA  

Energy Technology Data Exchange (ETDEWEB)

Nucleon spin physics will be studied in the HERMES experiment, that will use polarized internal targets of essentially pure atomic H, D, and {sup 3}He in the HERA electron storage ring at DESY. A series of measurements of spin-dependent properties of the nucleon and few-body nuclei will be made; the spin structure function g{sub 1}(x) of the proton and neutron will be measured to test the Bjorken sum rule and study the fraction of the nucleon spin carried by quarks; the spin structure function g{sub 2}W, sensitive to quark-gluon correlations, and the structure functions b{sub 1}(x), and {Delta}(x), sensitive to nuclear binding effects, will be measured; and, using the particle identification capability of the HERMES detector, pions will be detected in coincidence with the scattered electrons. The coincident hadron measurements represent the most important extension that can be made at this time to the existing measurements on the nucleon spin structure functions because they provide information about the flavor-dependence of the quark spin distribution in the nucleon. Argonne is providing the Cerenkov counter to be used for particle identification and developing the drifilm coating technique for the ultrathin target cell required for this experiment. The HERMES collaboration intends to use polarized targets with the highest available figures of merit, and the Argonne laser-driven source offers the most promise for a significant advance in present-day targets.

Jackson, H.E.; Hansen, J.O.; Jones, C.E. [and others

1995-08-01

353

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

354

Deuteron A(Q"2) structure function and the neutron electric form factor  

International Nuclear Information System (INIS)

We present new measurements of the deuteron A(Q"2) structure function in the momentum transfer region between 1 and 18 fm"-"2. The accuracy of the data ranges from 2% to 6%. We investigate the sensitivity of A(Q"2) to the nucleon-nucleon interaction and to the neutron electric form factor G_E"n. Our analysis shows that below 20 fm"-"2 G_E"n can be inferred from these data with a significantly improved accuracy. The model dependence of this analysis is discussed

1989-07-02

355

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

356

High energy nucleon incident optical potential by relativistic impulse approximation  

Energy Technology Data Exchange (ETDEWEB)

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)

Shigyo, Nobuhiro; Nakamura, Kazuo; Kitsuki, Hirohiko; Ishibashi, Kenji [Kyushu Univ., Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka (Japan)

2000-03-01

357

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

Energy Technology Data Exchange (ETDEWEB)

Multiplicities for the semi-inclusive production of each charge state of {pi}{sup {+-}} and K{sup {+-}} mesons in deep-inelastic scattering are presented as a function of the kinematic quantities x, Q{sup 2}, z and P{sub h} {sub perpendicular} {sub to}. The multiplicities were extracted from data collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams on a hydrogen or deuterium gas target. These results for identified hadrons constitute the most precise measurement to date, and will significantly enhance our understanding of the proton structure, as well as the fragmentation process in deep-inelastic scattering. Furthermore, the 3D binning at an unprecedented level of precision provides a handle to help disentangle the transverse momentum structure of both. The high level of precision coupled with an intermediate energy regime requires a careful study of the complex interaction between the experimental systematics, theoretical uncertainties, and the applicability of the factorization theorem within the standard framework of leading-twist collinear QCD. This is illustrated by the extraction of the valence quark ratio d{sub {nu}}/u{sub {nu}} at leading-order in {alpha}{sub s}. These results show a strong z-dependence below z {approx} 0.30, which could be interpreted as evidence for factorization breaking. This evidence weakens somewhat when isospin invariance of the fragmentation functions is assumed to be broken. Additionally, the multiplicities for the semi-inclusive production of {pi}{sup 0} mesons in deep-inelastic scattering are presented as a function of z. These multiplicities were extracted from the same data sample as used for the charged meson results. The neutral pion multiplicity is the same as the average charged pion multiplicity, up to z {approx} 0.70. This is consistent with isospin invariance below z {approx} 0.70. The results at high values of z show strong signs of isospin symmetry breaking.

Jossten, Sylvester Johannes

2013-10-15

358

Sum rule measurements of the spin-dependent compton amplitude (nucleon spin structure at Q"2 = 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 Q"2=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

1995-01-01

359

A-dependence of weak nuclear structure functions  

CERN Multimedia

Effect of nuclear medium on the weak structure functions $F_2^A(x,Q^2)$ and $F_3^A(x,Q^2)$ have been studied using charged current (anti)neutrino deep inelastic scattering on various nuclear targets. Relativistic nuclear spectral function which incorporate Fermi motion, binding and nucleon correlations are used for the calculations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, $F_i^A/F_i^{proton}$ and $F_i^A/F_i^{deuteron}$(i=2,3, A=$^{12}C$, $^{16}O$, $CH$ and $H_{2}O$) are obtained.

Haider, H; Athar, M Sajjad

2013-01-01

360

The EMC Effect and High Momentum Nucleons in Nuclei  

Energy Technology Data Exchange (ETDEWEB)

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 x{sub A}=AQ{sup 2}/(2M{sub A}q{sub 0}) is presented. Information about two-nucleon short-range correlations from experiments is also discussed and the remarkable linear relation between short-range correlations 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 the short-range correlated nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data.

Hen, Or; Higinbotham, Douglas; Miller, Gerald A; Piasetzky, Eliazer; Weinstein, Lawrence

2013-07-01

 
 
 
 
361

The EMC Effect and High Momentum Nucleons in Nuclei  

CERN Document Server

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 $x_A=AQ^2/(2M_A q_0)$ is presented. Information about two-nucleon short-range correlations from experiments is also discussed and the remarkable linear relation between short-range correlations and teh 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 the short-range correlated nucleons is presented. It is shown that both approaches are equally successful in describing the current EMC data.

Hen, O; Miller, G A; Piasetzky, E; Weinstein, L B

2013-01-01

362

Structured Functional Principal Component Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Motivated by modern observational studies, we introduce a class of functional models that expands nested and crossed designs. These models account for the natural inheritance of correlation structure from sampling design in studies where the fundamental sampling unit is a function or image. Inference is based on functional quadratics and their relationship with the underlying covariance structure of the latent processes. A computationally fast and scalable estimation procedu...

Shou, Haochang; Zipunnikov, Vadim; Crainiceanu, Ciprian M.; Greven, Sonja

2013-01-01

363

Quasi-elastic electron scattering and nucleon-nucleon correlations  

International Nuclear Information System (INIS)

In this contribution we briefly review some recent results, illustrating the possibilities of obtaining information on short-range corelations (SRC) by the quasi-elastic (QE) electron scattering, where the reaction mechanism is expected to be governed mainly by one-body electromagnetic nucleon currents and multi-nucleon final states can be excited. The paper is organized as follows: In Sec. 2 the results of recent experiments on inclusive 4He(e,e') and exclusive 4He(e,e'p)3H reactions performed at Saclay with the aim of checking the one-body nature of the reaction mechanism, are presented; in Sec. 3, the y-scaling analysis of SLAC inclusive cross sections for complex nuclei and the extraction of the nucleon momentum distribution will be illustrated; in Sec. 4 the effects of SRC on the QE response function is analyzed in terms of different models of the nucleon Spectral Function. (orig.)

1991-09-23

364

Quasi-elastic electron scattering and nucleon-nucleon correlations  

Energy Technology Data Exchange (ETDEWEB)

In this contribution we briefly review some recent results, illustrating the possibilities of obtaining information on short-range corelations (SRC) by the quasi-elastic (QE) electron scattering, where the reaction mechanism is expected to be governed mainly by one-body electromagnetic nucleon currents and multi-nucleon final states can be excited. The paper is organized as follows: In Sec. 2 the results of recent experiments on inclusive {sup 4}He(e,e') and exclusive {sup 4}He(e,e'p){sup 3}H reactions performed at Saclay with the aim of checking the one-body nature of the reaction mechanism, are presented; in Sec. 3, the y-scaling analysis of SLAC inclusive cross sections for complex nuclei and the extraction of the nucleon momentum distribution will be illustrated; in Sec. 4 the effects of SRC on the QE response function is analyzed in terms of different models of the nucleon Spectral Function. (orig.).

Marchand, C.; Bernheim, M.; Gerard, A.; Lakehal-Ayat, L.; Legoff, J.M.; Magnon, A.; Morgenstern, J.; Picard, J.; Reffay-Pikeroen, D.; Turk-Chieze, S.; Vernin, P.; Zghiche, A. (DSM/SEPN, CEN-Saclay, 91 - Gif-sur-Yvette (France)); Salme, G.; Simula, S. (INFN, Sezione di Sanita, Rome (Italy)); Brussel, M.K. (Dept. of Physics, Illinois Univ., Urbana, IL (USA)); Capitani, G.P.; De Sanctis, E. (Lab. Nazionali di Frascati, INFN (Italy)); Frullani, S.; Garibaldi, F. (Lab. di Fisica, ISS, Rome (Italy) INFN, Sezione di Sanita, Rome (Italy)); Jackson, H.E. (Argonne National Lab., IL (USA)); Meziani, Z.E. (Dept. of Physics, Stanford Univ., CA (USA))

1991-09-01

365

Neutron structure function and inclusive deep inelastic scattering from 3H and 3He at large Bjorken x  

International Nuclear Information System (INIS)

A detailed study of inclusive deep inelastic scattering (DIS) from mirror A=3 nuclei at large values of the Bjorken variable x is presented. The main purpose is to estimate the theoretical uncertainties in the extraction of the neutron DIS structure function from such nuclear measurements. On the one hand, within models in which no modification of the bound nucleon structure functions is taken into account, we have investigated the possible uncertainties arising from (i) charge symmetry breaking terms in the nucleon-nucleon interaction, (ii) finite Q2 effects neglected in the Bjorken limit, (iii) the role of different prescriptions for the nucleon spectral function normalization providing baryon number conservation, and (iv) the differences between the virtual-nucleon and light-cone formalisms. Although these effects have not yet been considered in existing analyses, our conclusion is that all these effects cancel at the level of ?1% for x < or approx. 0.75, in overall agreement with previous findings. On the other hand, we have considered several models in which the modification of the bound nucleon structure functions is accounted for to describe the EMC effect in DIS scattering from nuclei. It turns out that within these models the cancellation of nuclear effects is expected to occur only at a level of ?3%, leading to an accuracy of ?12% in the extraction of the neutron to proton structure function ratio at x?0.7-0.8. Another consequence of considering a broad range of models of the EMC effect is that the previously suggested iteration procedure does not improve the accuracy of the extraction of the neutron to proton structure function ratio

2002-08-01

366

The effect of including tensor forces in nucleon-nucleon interaction on three-nucleon binding energy  

International Nuclear Information System (INIS)

Separable two-body interactions are used in considering the three-nucleon problem. The nucleon-nucleon potentials are taken to include attraction and repulsion as well as tensor forces. The separable approximation is used in order to investigate the effect of the tensor forces. The separable expansion is introduced in the three-nucleon problem, by which the Faddeev equations are reduced to a well-behaved set of coupled integral equations. Numerical calculations are carried out for the obtained integral equations using potential functions of the Yamaguchi, Gaussian, Takabin, Mongan and Reid forms. The present calculated values of the binding energies of the 3H and 3He nuclei are in good agreement with the experimental values. The effect of including the tensor forces in the nucleon-nucleon interactions is found to improve the three-nucleon binding energy by about 4.490% to 8.324%. 37 refs., 2 tabs. (author)

1986-01-01

367

Two-nucleon knockout and nucleon-nucleon correlations  

International Nuclear Information System (INIS)

Resolution of discrete final states in the 16O(e, e'pp)14C and 16O(e, e'pn)14N reactions may provide an interesting tool to disentangle the contributions of correlations and two-body currents. Reaction calculations are here presented based on a direct knockout framework where final-state interaction and one- and two-body currents are included. The two-nucleon overlap functions are obtained for pp knockout from a calculation of the two-proton spectral function, which consistently includes both long-range and short-range correlations, for pn knockout in the framework of the coupled cluster method and include short-range as well as tensor correlations. The calculated cross sections indicate that the relative importance of correlation effects as compared with the contributions of two-body currents depends on the final state of the residual nucleus. This opens up good perspectives for a complete study of pp and pn correlations in two-nucleon knockout reactions. (author)

1999-05-10

368

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

2001-07-01

369

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

370

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

371

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

Science.gov (United States)

A density-dependent two-nucleon potential has been derived within the formalism of correlated basis function. The effects of three-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. Using the density dependent potential, we have carried out a study of the effects of three-nucleon interactions in symmetric nuclear matter within the Auxiliary Field Diffusion Monte Carlo (AFDMC) computational scheme.

Lovato, Alessandro; Benhar, Omar; Fantoni, Stefano; Illarionov, Alexey Yu; Schmidt, Kevin E.

2011-12-01

372

The Jefferson Lab 12 GeV program on nucleon structure  

Energy Technology Data Exchange (ETDEWEB)

This slide-show presents the experiments planned at JLab with their 12 GeV upgrade. Experiments reported address: the use of hadron spectra as probes of QCD; the transverse structure of hadrons; the longitudinal structure of hadrons; the 3-dimensional structure of hadrons; hadrons and cold nuclear matter; and low-energy tests of the Standard Model and fundamental symmetries.

Burkert, Volker D. [JLAB

2013-10-01

373

Effect due to compositeness of nucleons in deep inelastic lepton nucleus scattering  

CERN Multimedia

The off-shell behaviors of bound nucleons in deep inelastic lepton nucleus scattering are discussed in two scenarios with the basic constituents chosen to be baryon-mesons and quark-gluons respectively in light-cone formalism. It is found that when taking into account the effect due to internal quark structure of nucleons, the derived scaling variable for bound nucleons and the calculated nuclear structure functions are different from those in considering the baryon-mesons as the effective elementary constituents. This implies that the pure baryon-meson descriptions of nuclei give the inaccurate off-shell behavior of the bound nucleon structure function, thereby the quark-gluons seem to be the most appropriate degrees of freedom for nuclear descriptions. It is also shown that the EMC effect cannot be explained by nuclear binding effect from a sound theoretical basis.

Ma, B Q

1992-01-01

374

Three-Nucleon Forces Revisited - Some Historical Thoughts  

CERN Multimedia

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

375

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

376

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

377

Hard Pomeron enhancement of ultrahigh-energy neutrino-nucleon cross sections  

International Nuclear Information System (INIS)

An unknown small-x behavior of nucleon structure functions gives appreciable uncertainties to high-energy neutrino-nucleon cross sections. We construct structure functions using at small x a Regge description inspired by Donnachie and Landshoff with soft and hard Pomerons, and employing at larger x the perturbative QCD expressions. Smooth interpolation between the two regimes for each Q2 is provided with the help of simple polynomial functions. To obtain low-x neutrino-nucleon structure functions F2?N,?-barN(x,Q2) and the singlet part of F3?N,?-barN(x,Q2) from the Donnachie-Landshoff function F2ep(x,Q2), we use the Q2-dependent ratios R2(Q2) and R3(Q2) derived from perturbative QCD calculations. The nonsinglet part of F3 at low x, which is very small, is taken as a power-law extrapolation of the perturbative function at larger x. This procedure gives a full set of smooth neutrino-nucleon structure functions in the whole range of x and Q2 at interest. Using these structure functions, we calculate the neutrino-nucleon cross sections and compare them with some other cross sections known in the literature. Our cross sections turn out to be the highest among them at the highest energies, which is explained by the contribution of the hard Pomeron

2002-05-01

378

Nuclear Structure Functions at Low-$x$ in a Holographic Approach  

CERN Document Server

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 $F_2(x,Q^2)$. 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 $z_0$ and on the mean square distances, related to a parameter $Q^\\prime$, 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, $z_0$ and $Q^\\prime$, due to nuclear binding, can be reabsorbed in a $Q^2$-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 favourably compare with the experimental data.

Agozzino, L; Colangelo, P

2014-01-01

379

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

380

Chiral invariant renormalization of the pion-nucleon interaction  

International Nuclear Information System (INIS)

The leading divergences of the generating functional for Green functions of quark currents between one-nucleon states are calculated with heat kernel techniques. The results allow for a chiral invariant renormalization of all two-nucleon Green functions of the pion-nucleon system to O(p"3) in the low-energy expansion. (author)

1994-01-01

 
 
 
 
381

Spectrin: structure, function and disease.  

Science.gov (United States)

Spectrin is a large, cytoskeletal, and heterodimeric protein composed of modular structure of ? and ? subunits, it typically contains 106 contiguous amino acid sequence motifs called "spectrin repeats". Spectrin is crucial for maintaining the stability and structure of the cell membrane and the shape of a cell. Moreover, it contributes to diverse cell functions such as cell adhesion, cell spreading, and the cell cycle. Mutations of spectrin lead to various human diseases such as hereditary hemolytic anemia, type 5 spinocerebellar ataxia, cancer, as well as others. This review focuses on recent advances in determining the structure and function of spectrin as well as its role in disease. PMID:24302288

Zhang, Rui; Zhang, ChenYu; Zhao, Qi; Li, DongHai

2013-12-01

382

Polarized proton structure function in NLO approximation by using Bernstein polynomials  

International Nuclear Information System (INIS)

A next-to-leading order QCD analysis of proton structure in polarized deep inelastic lepton-nucleon scattering is present within the framework of the valon model. In this work, we calculated polarized valon distribution in NLO. The Bernstein polynomial method is used to compare QCD prediction to the g1? of available experimental data and direct fits for unknown parameters in the polarized valon distributions at the NLO approximation were performed. Using the obtained results of unpolarized proton structure function in next-to-leading, we computed here the ratio of structure function g1? / F1? as a function of ?. This ratio is very good in agreement with experimental data

2003-08-25

383

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

384

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

385

Nucleon Strangeness and Unitarity  

CERN Document Server

The strange-quark vector current form factors of the nucleon are analyzed within the framework of dispersion relations. Particular attention is paid to contributions made by $K\\bar{K}$ intermediate states to the form factor spectral functions. It is shown that, when the $K\\bar{K}\\to N\\bar{N}$ amplitude is evaluated in the Born approximation, the $K\\bar{K}$ contributions are identical to those arising from a one-loop calculation and entail a serious violation of unitarity. The mean square strangeness radius and magnetic moment are evaluated by imposing unitarity bounds on the kaon-nucleon partial wave amplitudes. The impact of including the kaon's form factor in the dispersion integrals is also evaluated.

Musolf, M J; Drechsel, D

1997-01-01

386

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

387

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 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.)

2004-01-01

388

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)

1976-09-27

389

Do gluons carry half of the nucleon momentum?  

CERN Document Server

We examine the conventional picture that gluons carry about half of the nucleon momentum in the asymptotic limit. We reveal that this large fraction is due to an unsuitable definition of the gluon momentum in an interacting theory. If defined in a gauge-invariant and consistent way, the asymptotic gluon momentum fraction is computed to be only about one fifth. This result suggests that the asymptotic limit of the nucleon spin structure should also be reexamined. Possible experimental test of our finding is discussed in terms of novel parton distribution functions.

Chen Xiang Song; Lü, Xiao-Fu; Wang, Fan; Goldman, T

2009-01-01

390

Nucleon form factors, generalized parton distributions and quark angular momentum  

International Nuclear Information System (INIS)

We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale ?=2 GeV to be Juv=0.230+0.009-0.024 and Jdv=-0.004+0.010-0.016.

2013-01-01

391

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

CERN Document Server

The complicated structure of the nucleon has been studied with great success in deep-inelastic lepton-nucleon scattering (DIS) experiments at CERN, SLAC and DESY. As a result the unpolarised structure functions have been measured accurately over a wide kinematic range. From these measurements it is possible to determine the gluon density in the nucleon with good accuracy via a so-called QCD fit. In the case of the spin structure of the nucleon the situation is different. Even after decades of experimental and theoretical efforts it remains to be understood how the spin of the nucleon of 1/2 in units of h-bar is to be accounted for in terms of contributions from the quarks and gluons inside the nucleon. Of particular interest is the question whether the polarised gluon density can explain the unexpected smallness of the quark contribution to the nucleon spin. The QCD fit, which worked well in the unpolarised case, yields a polarised gluon density Delta G which is only badly constrained. This is due to the fact...

von Hodenberg, Martin

2005-01-01

392

Strangeness and meson-nucleon sigma terms  

International Nuclear Information System (INIS)

The chiral constituent quark model (?CQM) has been extended to calculate the flavor structure of the nucleon through the meson-nucleon sigma terms which have large contributions from the quark sea and are greatly affected by chiral symmetry breaking and SU(3) symmetry breaking. The hidden strangeness component in the nucleon has also been investigated and its significant contribution is found to be consistent with the recent available experimental observations.

2011-10-21

393

Strangeness and meson-nucleon sigma terms  

CERN Document Server

The chiral constituent quark model ($\\chi$CQM) has been extended to calculate the flavor structure of the nucleon through the meson-nucleon sigma terms which have large contributions from the quark sea and are greatly affected by chiral symmetry breaking and SU(3) symmetry breaking. The hidden strangeness component in the nucleon has also been investigated and its significant contribution is found to be consistent with the recent available experimental observations.

Dahiya, Harleen

2011-01-01

394

Longitudinal heavy quark structure function  

Energy Technology Data Exchange (ETDEWEB)

In this paper we study the heavy-quark contribution to the proton non-singlet structure functions F{sub L}{sup NS}(x,Q{sup 2}). In this way we use very recently results for massive operator matrix elements, which contribute to the heavy flavor Wilson coefficients in unpolarized deeply inelastic scattering in the region Q{sup 2}>>m{sup 2}. The method of QCD analysis of non-singlet structure function, based on their Jacobi polynomials reconstruction from perturbative QCD predictions for the Mellin moments, is also described.

Khorramian, Ali N. [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of); School of Particles and Accelerators, IPM - Institute for Studies in Theoretical Physics and Mathematics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: khorramiana@theory.ipm.ac.ir; Atashbar Tehrani, S. [Physics Department, Semnan University, Semnan (Iran, Islamic Republic of); School of Particles and Accelerators, IPM - Institute for Studies in Theoretical Physics and Mathematics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: atashbar@ipm.ir; Mirjalili, A. [Physics Department, Yazd University, Yazd (Iran, Islamic Republic of); School of Particles and Accelerators, IPM - Institute for Studies in Theoretical Physics and Mathematics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: mirjalili@ipm.ir

2009-01-15

395

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

1995-07-01

396

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

397

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

398

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)

2005-01-01

399

Hadronic fluctuations and quark-antiquark asymmetry in the nucleon  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We derive the nucleon non-perturbative sea-quark distributions coming from a composite model involving quarks and hadronic degrees of freedom. The model predicts a definite structured quark-antiquark asymmetry in the nucleon sea.

Christiansen, H. R.; Magnin, J.

1998-01-01

400

SU(3) symmetry breaking chiral quark model and the spin structure of the nucleon  

International Nuclear Information System (INIS)

The chiral quark model, suggested by Eichten, Hindchliffe and Quigg, and extended by Cheng and Li, can explain many unexpected proton flavor and spin structures reasonably well. The SU(3) values of f_3/f_8 and ?_3/?_8 given in Cheng and Li's description are, however, inconsistent with the experimental data. Taking SU(3)-symmetry-breaking effect into account and extending the SU(3) calculation, we found that not only the above inconsistency can be removed but also better agreement obtained between many other theoretical predictions and experimental results. A consequence of this breaking is that the strange sea would be slightly negatively polarized, ? s ? -(0.05 - 0.06), and the total quark spin would contribute about one half of the proton spin, ? ? ? 0.45 - 0.47. (author). 20 refs, 3 tabs

1996-01-01

 
 
 
 
401

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)

2002-05-01

402

Parametrising the proton structure function  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We show that simple parametrisations at small x of the proton structure function work so well in limited regions of the $(x,Q^2)$ plane because they are approximately "self-consistent" solutions of the QCD evolution equation. For a class of them, we predict their $Q^2$ dependence and compare the result with experimental data.

Jenkovszky, L. L.; Lengyel, A.; Paccanoni, F.

1998-01-01

403

Diffractive structure functions in nuclei  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We calculate proton and nuclear diffractive structure functions in the IPsat (Kowalski-Teaney) dipole model. This parametrization has previously been shown to provide good agreement with inclusive F_2 measurements and exclusive vector meson measurements at HERA. We discuss how the impact parameter dependence crucially affects our analysis, in particular for small beta.

Lappi, T.; Kowalski, H.; Marquet, C.; Venugopalan, R.

2009-01-01

404

A Covariant model for the nucleon and the Delta  

International Nuclear Information System (INIS)

The covariant spectator formalism is used to model the nucleon and the ? (1232) as a system of three constituent quarks with their own electromagnetic structure. The definition of the 'fixed-axis' polarization states for the diquark emitted from the initial state vertex and absorbed into the final state vertex is discussed. The helicity sum over those states is evaluated and seen to be covariant. Using this approach, all four electromagnetic form factors of the nucleon, together with the magnetic form factor, GM*, for the ? N ? ? transition, can be described using manifestly covariant nucleon and ? wave functions with zero orbital angular momentum L, but a successful description of GM* near Q2=0 requires the addition of a pion cloud term not included in the class of valence quark models considered here. We also show that the pure S$-wave model

2008-06-01

405

Spin observables in nucleon-nucleus scattering  

International Nuclear Information System (INIS)

The curse of inelastic nucleon scattering and charge exchange has always been the enormous complexity of the nucleon-nucleon (N-N) interaction. This complexity, however, can also be viewed as the ultimate promise of nucleons as probes of nuclear structure. Given an adequate theoretical basis, inelastic nucleon scattering is capable of providing information not obtainable with other probes. Recently a revolution of experimental technique has taken place that makes it desirable to re-examine the question of what physics is ultimately obtainable from inelastic nucleon scattering. It is now feasible to perform complete polarization transfer (PT) experiments for inelastic proton scattering with high efficiency and excellent energy resolution. Programs to measure PT obsevables are underway at several laboratories, and results are beginning to appear. Objectives of this presentation are to examine how such experiments are done, and what physics is presently obtained and may ultimately be learned from them

1982-03-27

406

Twist-3 effects for polarized virtual photon structure function $g_2^\\gamma$  

CERN Multimedia

We investigate twist-3 effects in the polarized virtual photon. The structure function $g_2^\\gamma$, which exists only for the virtual photon target and can be measured in future polarized $e^+ e^-$ collider experiments, receives both twist-2 and twist-3 contributions. The twist-3 part is analyzed in pure QED interaction as well as in LO QCD. We find the twist-3 contribution is appreciable for the photon in contrast to the nucleon case.

Sasaki, K

2003-01-01

407

Perturbative QCD study of the polarized structure function g_1 at Next-to-Leading-Order  

International Nuclear Information System (INIS)

A NLO perturbative study of all available data on polarized structure function g_1(x,Q"2) is presented. It is first explained how the Q"2 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)

1998-01-01

408

Quark-Hadron Duality in Spin Structure Functions g1p and g1d  

Digital Repository Infrastructure Vision for European Research (DRIVER)

New measurements of the spin structure functions of the proton and deuteron g1p(x,Q2) and g1d(x,Q2) in the nucleon resonance region are compared with extrapolations of target-mass-corrected next-to-leading-order (NLO) QCD fits to higher energy data. Averaged over the entire resonance region (W1.7 GeV2. This global duality appears to result from cancellations among the prominent lo...

Bosted, P. E.; Dharmawardane, K. V.; Dodge, G. E.; Forest, T. A.; Kuhn, S. E.; Al, Y. Prok Et

2006-01-01

409

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

CERN Multimedia

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

410

?N: determination of structure functions  

International Nuclear Information System (INIS)

Since the 1980 conference a large number of results on structure functions have been reported from neutrino experiments. New data are available from ? and anti ? scattering on protons and neutrons. Measurements of the cross section ratios sigmasup(?n)/sigmasup(?p) as function of energy and scaling variables x and y allow the extraction of differences between the u- and d-quark momentum distributions. Final results on structure functions from ? experiments on isoscalar targets exhibit clearly scaling violations. QCD fits to the data yield values of the scale breaking parameter ? = 0.1-0.2 GeV. From a new measurement of the Q"2 evolution of the antiquarks together with F_2 data the gluon x distribution has been extracted. The discrepancies in the measurement of the total cross section are still unresolved. (orig.)

1981-08-29

411

Bound-state quark and gluon contributions to structure functions in QCD  

International Nuclear Information System (INIS)

One can distinguish two types of contributions to the quark and gluon structure functions of hadrons in quantum chromodynamics: ''intrinsic'' contributions, which are due to the direct scattering on the bound-state constituents, and ''extrinsic'' contributions, which are derived from particles created in the collision. In this talk, I discussed several aspects of deep inelastic structure functions in which the bound-state structure of the proton plays a crucial role: the properties of the intrinsic gluon distribution associated with the proton bound-state wavefunction; the separation of the quark structure function of the proton onto intrinsic ''bound-valence'' and extrinsic ''non-valence'' components which takes into account the Pauli principle; the properties and identification of intrinsic heavy quark structure functions; and a theory of shadowing and anti-shadowing of nuclear structure functions, directly related to quark-nucleon interactions and the gluon saturation phenomenon. 49 refs., 5 figs

1990-05-14

412

Nucleon properties inside compressed nuclear matter  

CERN Document Server

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

Rozynek, Jacek

2014-01-01

413

Partitioning of the nucleon spin  

International Nuclear Information System (INIS)

The purpose of the present study is to understand the partitioning of the nucleon spin among its constituents using the chiral quark model with configuration mixing which provides an excellent fit to spin distribution functions, quark distribution functions, octet and decuplet magnetic moments including the Coleman-Glashow sum rule

2003-12-01

414

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

415

Non-empirical energy density functional for the nuclear structure  

International Nuclear Information System (INIS)

The energy density functional (EDF) formalism is the tool of choice for large-scale low-energy nuclear structure calculations both for stable experimentally known nuclei whose properties are accurately reproduced and systems that are only theoretically predicted. We highlight in the present dissertation the capability of EDF methods to tackle exotic phenomena appearing at the very limits of stability, that is the formation of nuclear halos. We devise a new quantitative and model-independent method that characterizes the existence and properties of halos in medium- to heavy-mass nuclei, and quantifies the impact of pairing correlations and the choice of the energy functional on the formation of such systems. These results are found to be limited by the predictive power of currently-used EDFs that rely on fitting to known experimental data. In the second part of this dissertation, we initiate the construction of non-empirical EDFs that make use of the new paradigm for vacuum nucleon-nucleon interactions set by so-called low-momentum interactions generated through the application of renormalization group techniques. These soft-core vacuum potentials are used as a step-stone of a long-term strategy which connects modern many-body techniques and EDF methods. We provide guidelines for designing several non-empirical models that include in-medium many-body effects at various levels of approximation, and can be handled in state-of-the art nuclear structure codes. In the present work, the first step is initiated through the adjustment of an operator representation of low-momentum vacuum interactions using a custom-designed parallel evolutionary algorithm. The first results highlight the possibility to grasp most of the relevant physics for low-energy nuclear structure using this numerically convenient Gaussian vertex. (author)

2008-01-01

416

Sum rule measurements of the spin-dependent compton amplitude (nucleon spin structure at Q(sup 2) = 0).  

Science.gov (United States)

Energy weighted integrals of the difference in helicity-dependent photo-production cross sections ((sigma)(sub (1/2)) - (sigma)(sub 3/2)) provide information on the nucleon's Spin-dependent Polarizability ((gamma)), and on the spin-dependent part of the a...

D. Babusci G. Giordano H. Baghaei A. Cichocki M. Blecher

1995-01-01

417

Pion-nucleon partial wave analysis and study of baryon structure. Progress report, June 1, 1979-May 31, 1981  

International Nuclear Information System (INIS)

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

1981-01-01

418

The problem of the mean free path of bound nucleons  

International Nuclear Information System (INIS)

The neat-free-path (MFP) of bound nucleons is one of the classic problems in nuclear structure theory. Although it has often been asserted that the MFP is long, theoretical estimates and empirical evidence consistently show that the MFP of low-energy nucleons is less than two nucleon diameters (2-3 fm) and far shorter than the several nuclear diameters (>30 fm) needed to establish nucleons in intra-nuclear orbits. Such results indicate that the nucleon states known from nuclear spectroscopy must be explained by a version of the independent-particle model which does not require the free orbiting of nucleons within nuclei

1990-08-20

419

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)

1982-01-01

420

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

 
 
 
 
421

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

422

SLAC measurement of the neutron spin structure function  

Energy Technology Data Exchange (ETDEWEB)

A measurement of the nucleon spin asymmetries from deep inelastic scattering of polarized electrons by polarized [sup 3]He has been performed. The neutron spin structure function g[sub 1][sup n] is extracted and used to test the Bjorken sum rule. The neutron integral assuming a simple Regge theory extrapolation at low x is [integral][sub 0][sup 1]g[sub 1][sup n](x)dx = [minus]0.022 [plus minus] 0.011. Combined with the EMC proton results, the Bjorken sum rule predicts a neutron integral of [integral][sub 0][sup 1]g[sub 1][sup n](x)dx = [minus]0.065 [plus minus] 0.018.

Hughes, E.

1993-04-01

423

Malaria adhesins: structure and function.  

Science.gov (United States)

The malaria parasite Plasmodium utilizes specialized proteins for adherence to cellular receptors in its mosquito vector and human host. Adherence is critical for parasite development, host cell traversal and invasion, and protection from vector and host immune mechanisms. These vital roles have identified several adhesins as vaccine candidates. A deficiency in current adhesin-based vaccines is induction of antibodies targeting non-conserved, non-functional and decoy epitopes due to the use of full length proteins or binding domains. To alleviate the elicitation of non-inhibitory antibodies, conserved functional regions of proteins must be identified and exploited. Structural biology provides the tools necessary to achieve this goal, and has succeeded in defining biologically functional receptor binding and oligomerization interfaces for a number of promising malaria vaccine candidates. We describe here the current knowledge of Plasmodium adhesin structure and function, and how it has illuminated elements of parasite biology and defined interactions at the host/vector and parasite interface. PMID:24506585

Malpede, Brian M; Tolia, Niraj H

2014-05-01

424

Polarized target for nucleon-nucleon experiments at Saturne II  

Energy Technology Data Exchange (ETDEWEB)

Continuous improvements of SATURNE polarized target resulted in a flexible and reliable facility for spin physics. For polarized neutron target, two cartridges loaded with {sup 6}{ital LiD} and {sup 6}{ital LiH} are set in the refrigerator and can be quickly inserted in the beam. The polarized proton target is a 70 cm{sup 3} cartridge loaded with Pentanol-2, a promising material according to the results obtained. Angular distribution as a function of a kinematically conjugate angle and coplanarity in nucleon-nucleon scattering is shown for different targets. {copyright} {ital 1995 American Institute of Physics.}

Ball, J. [Laboratoire National SATURNE, CNRS/IN2P3, CEA/DSM (France); Benda, B.; Chaumette, P. [CEA/DAPNIA, CE-Saclay, 91191 Gif-sur-Yvette Cedex (France); Combet, M. [Laboratoire National SATURNE, CNRS/IN2P3, CEA/DSM (France); Deregel, J.; Durand, G.; Gaudron, C. [CEA/DAPNIA, CE-Saclay, 91191 Gif-sur-Yvette Cedex (France); Janout, Z. [Laboratory of Nuclear Problems, JINR, Dubna, Moscow Region 141980 (Russia)]|[Present address: Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Brehova 7, 11519 Prague 1 (Czech Republic); Kasprzyk, T.E. [ANL-HEP, 9700 South Cass Ave., Argonne, Illinois 60439 (United States); Khachaturov, B.A. [Laboratory of Nuclear Problems, JINR, Dubna, Moscow Region 141980 (Russia); Lehar, F.; de Lesquen, A. [CEA/DAPNIA, CE-Saclay, 91191 Gif-sur-Yvette Cedex (France); Matafonov, V.N. [Laboratory of Nuclear Problems, JINR, Dubna, Moscow Region 141980 (Russia); Sans, J. [Laboratoire National SATURNE, CNRS/IN2P3, CEA/DSM (France); Usov, Y.A. [Laboratory of Nuclear Problems, JINR, Dubna, Moscow Region 141980 (Russia)

1995-09-01

425

Polarized target for nucleon-nucleon experiments at Saturne II  

International Nuclear Information System (INIS)

Continuous improvements of SATURNE polarized target resulted in a flexible and reliable facility for spin physics. For polarized neutron target, two cartridges loaded with 6LiD and 6LiH are set in the refrigerator and can be quickly inserted in the beam. The polarized proton target is a 70 cm3 cartridge loaded with Pentanol-2, a promising material according to the results obtained. Angular distribution as a function of a kinematically conjugate angle and coplanarity in nucleon-nucleon scattering is shown for different targets. copyright 1995 American Institute of Physics

1995-09-01

426

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

427

Skyrmions and the nucleon-nucleon interaction  

Energy Technology Data Exchange (ETDEWEB)

We present the standard procedure to obtain nucleon-nucleon (NN) potential from the Skyrme model, as well as our analysis of the scalar term of this potential, which is known not to accomplish for the intermediate attraction present in phenomenological potentials. (author) 5 refs., 1 tab.; isabela and mane at axpfep1.if.usp.br

Cavalcante, I.P.; Robilotta, M.R. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica

1997-12-31

428

Model ambiguities in the neutron structure function extracted from combined data on deuteron and proton  

International Nuclear Information System (INIS)

Two theoretical approaches to extract the neutron structure functions from combined experimental data on the proton and deuteron are considered. It is shown that the consideration only of the Fermi motion of nucleons in the deuteron in the light cone kinematics gives wrong results at large x (x > 0.7). The meson exchange corrections and binding effects in the deuteron must be taken into account. A new treatment of the experimental neutron structure function obtained from BCDMS-collaboration data is given. (author). 18 refs, 4 figs, 2 tabs

1991-01-01

429

New measurements of proton polarized structure functions in charged current processes at DESY HERA  

Energy Technology Data Exchange (ETDEWEB)

Predictions for longitudinal spin asymmetries which single out new polarized nucleon structure functions in deeply inelastic charged current interactions at DESY HERA energies are given, exploiting their interpretation in terms of polarized quark distributions. These asymmetries turn out to be large and allow a measurement of the new polarized structure functions g{sub 1}{sup W} and g{sub 5}{sup W}, which would add valuable tests and information on the spin content of quarks inside a polarized proton. We also show that single-spin asymmetries in neutral current interactions are very small. {copyright} {ital 1997} {ital The American Physical Society}

Anselmino, M. [Dipartimento di Fisica Teorica, Universita di Torino and INFN, Sezione di Torino, Via P. Giuria 1, 10125 Torino (Italy); Gambino, P. [Max Planck Institut fuer Physik, Werner Heisenberg Institut, Foehringer Ring 6, D80805 Muenchen (Germany); Kalinowski, J. [Warsaw University, Institute of Theoretical Physics, Ul. Hoza 69, 00681 Warsaw (Poland)

1997-05-01

430

New proton polarized structure functions in charged current processes at HERA  

CERN Multimedia

Estimates for longitudinal spin asymmetries which single out new polarized nucleon structure functions in deeply inelastic charged current interactions at HERA energies are given, exploiting their interpretation in terms of polarized quark distributions. These asymmetries turn out to be large and allow a measurement of the new polarized structure functions $g_1^{W}$ and $g_5^{W}$, which would add valuable tests and information on the spin content of quarks inside a polarized proton. We also show that single spin asymmetries in neutral current interactions are very small.

Anselmino, M; Kalinowski, Jan

1997-01-01

431

Strange Quarks in the Nucleon Sea: Result from HAPPEX II.  

Science.gov (United States)

The structure of the nucleon is of fundamental interest. Almost all the non-dark-matter mass in the Universe is contained within the nucleon. The nucleon is unique among systems of ordinary matter in that most of its mass is not due to the masses of its c...

K. A. Aniol

2007-01-01

432

Structure of A=10-13 nuclei with two- plus three-nucleon interactions from chiral effective field theory  

CERN Document Server

Properties of finite nuclei are evaluated with two-nucleon (NN) and three-nucleon (NNN) interactions derived within chiral effective field theory (EFT). The nuclear Hamiltonian is fixed by properties of the A=2 system, except for two low-energy constants (LECs) that parameterize the short range NNN interaction. We constrain those two LECs by a fit to the A=3 system binding energy and investigate sensitivity of 4He, 6Li, 10,11B and 12,13C properties to the variation of the constrained LECs. We identify a preferred choice that gives globally the best description. We demonstrate that the NNN interaction terms significantly improve the binding energies and spectra of mid-p-shell nuclei not just with the preferred choice of the LECs but even within a wide range of the constrained LECs. At the same time, we find that a very high quality description of these nuclei requires further improvements to the chiral Hamiltonian.

Navrátil, P; Nogga, A; Ormand, W E; Vary, J P

2007-01-01

433

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

434

Soudan 2 nucleon decay experiment  

International Nuclear Information System (INIS)

The Soudan 2 nucleon decay experiment consists of a 1.1 Kton fine grained iron tracking calorimeter. It has a very isotropic detection structure which along with its flexible trigger will allow detection of multiparticle and neutrino proton decay modes. The detector has now entered its construction stage

1986-04-16

435

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

436

Structure Function Measurement at HERA  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Bernardi, Gregorio

1996-01-01

437

Extraction of Neutron Structure Functions from (Semi)InclusiveDeuteron Data  

Science.gov (United States)

Structure functions parameterize fundamental information about the internal structure of the nucleon, and in the deep-inelastic region are given in terms of the longitudinal momentum distributions of the nucleons' quark and gluon constituents. Compared to the copious amount of proton structure function data, there is considerably less for the neutron, which is mainly derived from deuteron data. Extracting neutron structure functions from the deuteron results in ambiguities from the necessary nuclear corrections. Such ambiguities can be confronted using free neutron and proton and inclusive deuteron data. The Barely Off-shell Neutron Structure experiment (BoNuS) ran in experimental Hall B at Jefferson Lab in 2005 and provided a virtually free neutron target for the first time. Extraction of the free neutron structure functions has been performed via global fits to both the BoNuS and deuteron inclusive data, utilizing an existing fit to the free proton, within the framework of the weak binding approximation and utilizing various nuclear potentials. We will report on the results of this fitting effort and the consistency between neutron information from BoNuS and the impulse approximation.

Kalantarians, Narbe

2013-04-01

438

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

International Nuclear Information System (INIS)

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, ?d channel, ?d elastic scattering, pp ? ?d channel, deuteron break-up reactions, and narrow structures in missing-mass spectra. 93 refs., 26 figs

1985-08-26

439

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

440

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

 
 
 
 
441

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

442

Nucleon scattering and reactions  

Energy Technology Data Exchange (ETDEWEB)

Recent advances in the fundamental calculation of the nucleon optical potential from the nucleon-nucleon interaction and the nuclear density distributions are reviewed, with particular attention to the understanding of the anomaly in the real part of the potential around the Fermi energy. Some data that pose a challenge to theories of the nucleon-nucleon interaction are examined, together with detailed systematics of nuclear RMS charge radii. The application of optical model and distorted wave theory to analyse neutron elastic and inelastic scattering is described.

Hodgson, P.E.

1983-01-01

443

Proton and neutron polarized targets for nucleon-nucleon experiments at SATURNE II  

Energy Technology Data Exchange (ETDEWEB)

A SATURNE polarized target has been used for nucleon-nucleon elastic scattering and transmission experiments for 15 years. The polarized proton target is a 70 cm{sup 3} cartridge loaded with Pentanol-2. For polarized neutron target, two cartridges loaded with {sup 6}LiD and {sup 6}LiH are set in the refrigerator and can be quickly inserted in the beam. First experiments using {sup 6}Li products in quasielastic pp or pn analyzing power measurements are compared with the same observables measured in a free nucleon-nucleon scattering using polarized proton targets. Angular distribution as a function of a kinematically conjugate angle and coplanarity in nucleon-nucleon scattering is shown for different targets. (author). 15 refs.; Submitted to Nuclear Instruments and Methods (NL).

Ball, J.; Combet, M.; Sans, J.L. [Laboratoire National Saturne, Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France); Benda, B.; Chaumette, P.; Deregel, J.; Durand, G.; Dzyubak, A.P.; Gaudron, C.; Lehar, F. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee; Janout, Z.; Khachaturov, B.A. [Joint Inst. for Nuclear Research, Dubna (Russian Federation). Lab. of Nuclear Problems] [and others

1996-12-31

444

Soudan nucleon decay program  

International Nuclear Information System (INIS)

The Soudan nucleon decay program is being carried out in the Soudan iron mine in northeastern Minnesota, at a depth of 2000 m of water equivalent. A 30-ton prototype experiment, Soudan 1, has been built and is now being operated by a University of Minnesota - Argonne National Laboratory collaboration. The detector is a block of iron-loaded concrete instrumented with 3456 gas proportional tubes. It can detect nucleon decay at the 2 x 1030 year level, and will measure cosmic-ray induced backgrounds. Soudan 1 is also obtaining data on very high energy cosmic-ray interactions. Monte-Carlo predictions of perform