共查询到20条相似文献,搜索用时 31 毫秒
1.
Mazouz M Camsonne A Camacho CM Ferdi C Gavalian G Kuchina E Amarian M Aniol KA Beaumel M Benaoum H Bertin P Brossard M Chen JP Chudakov E Craver B Cusanno F de Jager CW Deur A Feuerbach R Fieschi JM Frullani S Garçon M Garibaldi F Gayou O Gilman R Gomez J Gueye P Guichon PA Guillon B Hansen O Hayes D Higinbotham D Holmstrom T Hyde CE Ibrahim H Igarashi R Jiang X Jo HS Kaufman LJ Kelleher A Kolarkar A Kumbartzki G Laveissiere G Lerose JJ Lindgren R Liyanage N Lu HJ Margaziotis DJ Meziani ZE 《Physical review letters》2007,99(24):242501
The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced. 相似文献
2.
K. Goeke V. Guzey M. Siddikov 《The European Physical Journal C - Particles and Fields》2008,56(2):203-219
Within the framework of the color glass condensate model, we evaluate quark and gluon generalized parton distributions (GPDs)
and the cross section of deeply virtual Compton scattering (DVCS) in the small-xB region. We demonstrate that the DVCS cross section becomes independent of energy in the limit of very small xB, which clearly indicates saturation of the DVCS cross section. Our predictions for the GPDs and the DVCS cross section at
high energies can be tested at the future Electron–Ion Collider and in ultra-peripheral nucleus–nucleus collisions at the
LHC.
PACS 12.38.Mh; 13.60.Fz; 13.85.Fb; 24.85.+p; 25.20.Dc 相似文献
3.
D. Sokhan 《Physics of Particles and Nuclei》2014,45(1):170-172
Generalised Parton Distributions (GPDs) offer an insight into the three-dimensional structure of the nucleon and its internal dynamics, relating the longitudinal momentum of quarks to their transverse position. A very effective means of accessing GPDs is via measurements of cross-sections and polarisation-asymmetries in Deeply Virtual Compton Scattering (DVCS). In particular, the beam-spin asymmetry (BSA) in DVCS from the neutron is especially sensitive to angular momentum of the up- and down-quarks, and its measurement therefore has potential to shed important light on the puzzle of nucleon spin. We present a preliminary extraction of BSA from a recent experiment using a 6 GeV electron beam and the CLAS detector at Jefferson Laboratory and introduce the Central Neutron Detector to be integrated with CLAS12 for the exclusive measurement of neutron DVCS at 11 GeV, made possible by the Jefferson Lab upgrade. 相似文献
4.
5.
Spin structure is one of the fundamental subjects in the study of nucleon structure.Recently it is found that Generalized Parton Distributions(GPDs) are related to the total angular momentum carried by partons,which offers a possible solution to the spin puzzle in the first time.We get access to certain GPDs by looking at the azimuthal angle asymmetries attributed to the interference between Deeply Virtual Compton Scattering (DVCS) and Bethe-Heilter processes in HERMES experiment.By measuring the asymmetry with respect to transverse target polarization from proton target,a model-dependent constraint on J_u vs J_d is obtained.Another worldwide unique channel is nuclear DVCS.The preliminary results on asymmetries with respect to beam spin and beam charge are reported. 相似文献
6.
In this paper, we discuss the feasibility of measuring deeply virtual Compton scattering (DVCS) on nuclei in a collider setting, as for example, the planned high-luminosity Electron-Ion Collider (EIC). We demonstrate that employing our recent model for nuclear generalized parton distributions (nGPDs), the one-photon unpolarized DVCS cross section as well as the azimuthal and spin asymmetry are of the same size as in the proton case. This will allow for an experimental extraction of nuclear GPDs with high precision, shedding new light not only on nuclear shadowing at small xBj but also on the interplay of shadowing and nuclear enhancement at
.Received: 8 September 2003, Revised: 24 November 2003, Published online: 15 January 2004 相似文献
7.
The two leading twist, quark helicity conserving generalized parton distributions (GPDs) of 3He, accessible, for example, in coherent deeply virtual Compton scattering (DVCS), are calculated in impulse approximation (IA). Their sum, at low momentum transfer, is found to be largely dominated by the neutron contribution, so that 3He is very promising for the extraction of the neutron information. Anyway, such an extraction could be not trivial. A technique, able to take into account the nuclear effects included in the IA analysis in the extraction procedure, even at moderate values of the momentum transfer, is proposed. Coherent DVCS arises therefore as a crucial experiment to access, for the first time, the neutron GPDs and the orbital angular momentum of the partons in the neutron. 相似文献
8.
Qian X Allada K Dutta C Huang J Katich J Wang Y Zhang Y Aniol K Annand JR Averett T Benmokhtar F Bertozzi W Bradshaw PC Bosted P Camsonne A Canan M Cates GD Chen C Chen JP Chen W Chirapatpimol K Chudakov E Cisbani E Cornejo JC Cusanno F Dalton MM Deconinck W de Jager CW De Leo R Deng X Deur A Ding H Dolph PA Dutta D El Fassi L Frullani S Gao H Garibaldi F Gaskell D Gilad S Gilman R Glamazdin O Golge S Guo L Hamilton D Hansen O Higinbotham DW Holmstrom T Huang M Ibrahim HF Iodice M Jiang X Jin G 《Physical review letters》2011,107(7):072003
We report the first measurement of target single spin asymmetries in the semi-inclusive (3)He(e,e'π(±))X reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.16 < x < 0.35 with 1.4 < Q(2) < 2.7 GeV(2). The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The π(±) Collins moments for (3)He are consistent with zero, except for the π(+) moment at x = 0.35, which deviates from zero by 2.3σ. While the π(-) Sivers moments are consistent with zero, the π(+) Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to (3)He, and are largely consistent with the predictions of phenomenological fits and quark model calculations. 相似文献
9.
van Buuren LD Szczerba D Alarcon R Boersma DJ van den Brand JF Bulten HJ Ent R Ferro-Luzzi M Harvey M Heimberg P Higinbotham DW Klous S Kolster H Lang J Militsyn BL Nikolenko D Norum BE Passchier I Poolman HR Rachek I Simani MC Six E de Vries H Zhou ZL 《Physical review letters》2002,89(1):012001
We report on measurements of the cross section and provide first data on spin correlation parameters A(TT') and A(TL') in inclusive scattering of longitudinally polarized electrons from nuclear-polarized hydrogen. Polarized electrons were injected into an electron storage ring operated at a beam energy of 720 MeV. Polarized hydrogen was produced by an atomic beam source and injected into an open-ended cylindrical cell, located in the electron storage ring. The four-momentum transfer squared ranged from Q2 = 0.2 GeV(2)/c(2) at the elastic scattering peak to Q2 = 0.11 GeV(2)/c(2) at the Delta(1232) resonance. The data provide a stringent test of pion electroproduction models. 相似文献
10.
Recently, coherent deeply virtual Compton scattering (DVCS) off 3He nuclei has been proposed to access the neutron generalized parton distributions (GPDs). In impulse approximation (IA) studies, it has been shown, in particular, that the sum of the two leading twist, quark helicity conserving GPDs of 3He, H and E, at low momentum transfer, is dominated by the neutron contribution, so that 3He is very promising for the extraction of the neutron information. Nevertheless, such an extraction could be not trivial. A technique, able to take into account the nuclear effects included in the IA analysis in the extraction procedure, has been therefore developed. In this work, the IA calculation of the spin dependent GPD \({\tilde H}\) of 3He is presented for the first time. This quantity is found to be largely dominated, at low momentum transfer, by the neutron contribution, which could be extracted using arguments similar to the ones previously proposed for the other GPDs. The known forward limit of the IA calculation of \({\tilde H}\) , yielding the polarized parton distributions of 3He, is correctly recovered. The knowledge of the GPDs H, E and \({\tilde H}\) of 3He will allow now the evaluation of the cross section asymmetries which are relevant for coherent DVCS off 3He at Jefferson Lab kinematics, an important step towards the planning of possible experiments. 相似文献
11.
D. V. Kiptily M. V. Polyakov 《The European Physical Journal C - Particles and Fields》2004,37(1):105-114
The genuine twist-3 quark-gluon (
) contributions to the generalized parton distributions (GPDs) are estimated in the model of the instanton vacuum. These twist-3 effects are found to be parametrically suppressed relative to the kinematical twist-3 ones due to the small packing fraction of the instanton vacuum. We derived exact sum rules for the twist-3 GPDs.Received: 21 April 2004, Published online: 6 August 2004 相似文献
12.
We discuss a new leading-order parameterization of generalized parton distributions of the proton, which is based on the idea
of duality. In its minimal version, the parameterization is defined by the usual quark singlet parton distributions and the
form factors of the energy-momentum tensor. We demonstrate that our parameterization describes very well the absolute value,
the Q2-dependence and the W-dependence of HERA data on the total DVCS cross section and contains no free parameters in the HERA
kinematics. The parameterization suits the low-xBj region especially well, which allows us to advocate it as a better alternative to the frequently used double distribution
parameterization of the GPDs.
PACS 13.60.-r, 12.38.Lg 相似文献
13.
14.
Horn T Aniol K Arrington J Barrett B Beise EJ Blok HP Boeglin W Brash EJ Breuer H Chang CC Christy ME Ent R Gaskell D Gibson E Holt RJ Huber GM Jin S Jones MK Keppel CE Kim W King PM Kovaltchouk V Liu J Lolos GJ Mack DJ Margaziotis DJ Markowitz P Matsumura A Meekins D Miyoshi T Mkrtchyan H Niculescu I Okayasu Y Pentchev L Perdrisat C Potterveld D Punjabi V Reimer P Reinhold J Roche J Roos PG Sarty A Smith GR Tadevosyan V Tang LG Tvaskis V Vidakovic S Volmer J Vulcan W Warren G Wood SA Xu C 《Physical review letters》2006,97(19):192001
The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F(pi)) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F(pi) is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction. 相似文献
15.
M. Guidal 《The European Physical Journal A - Hadrons and Nuclei》2008,37(3):319-332
We have developed a fitting code based on the leading-twist handbag Deep Virtual Compton Scattering (DVCS) amplitude in order
to extract Generalized Parton Distribution (GPD) information from DVCS observables in the valence region. In a first stage,
with simulations and pseudo-data, we show that the full GPD information can be recovered from experimental data if enough
observables are measured. If only some of these observables are measured, valuable information can still be extracted, with
certain observables being particularly sensitive to certain GPDs. In a second stage, we make a practical application of this
code to the recent DVCS Jefferson Lab Hall-A data from which we can extract numerical constraints for the two H GPD Compton form factors.
An erratum to this article can be found at 相似文献
16.
M. McDermott R. Sandapen G. Shaw 《The European Physical Journal C - Particles and Fields》2002,22(4):655-666
An analysis of Deeply Virtual Compton Scattering (DVCS) is made within the colour dipole model. We compare and contrast two
models for the dipole cross-section which have been successful in describing structure function data. Both models agree with
the available cross section data on DVCS from HERA. We give predictions for various azimuthal angle asymmetries in HERA kinematics
and for the DVCS cross section in the THERA region.
Received: 22 July 2001 / Revised version: 5 November 2001 / Published online: 14 December 2001 相似文献
17.
Dohrmann F Ahmidouch A Armstrong CS Arrington J Asaturyan R Avery S Bailey K Bitao H Breuer H Brown DS Carlini R Cha J Chant N Christy E Cochran A Cole L Crowder J Danagoulian S Elaasar M Ent R Fenker H Fujii Y Gan L Garrow K Geesaman DF Gueye P Hafidi K Hinton W Juengst H Keppel C Liang Y Liu JH Lung A Mack D Markowitz P Mitchell J Miyoshi T Mkrtchyan H Mtingwa SK Mueller B Niculescu G Niculescu I Potterveld D Raue BA Reimer PE Reinhold J Roche J Sarsour M Sato Y Segel RE Semenov A Stepanyan S 《Physical review letters》2004,93(24):242501
The (3,4)(Lambda)H and (4)(Lambda)H hypernuclear bound states have been observed for the first time in kaon electroproduction on (3,4)He targets. The production cross sections have been determined at Q(2)=0.35 GeV2 and W=1.91 GeV. For either hypernucleus the nuclear form factor is determined by comparing the angular distribution of the (3,4)He(e,e(')K+)(3,4)(Lambda)H processes to the elementary cross section 1H(e,e K+)Lambda on the free proton, measured during the same experiment. 相似文献
18.
M. Vanderhaeghen 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):429-432
We discuss how generalized parton distributions (GPDs) enter in a variety of hard exclusive processes such as deeply virtual Compton scattering (DVCS) and hard meson electroproduction reactions on the nucleon. We show some key observables which are sensitive to the various hadron structure aspects of the GPDs, and discuss their experimental status.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.60.Fz Elastic and Compton scattering - 13.60.Le Meson production - 12.38.Bx Perturbative calculations 相似文献
19.
Ulmer PE Aniol KA Arenhövel H Chen JP Chudakov E Crovelli D Finn JM Fissum KG Gayou O Gomez J Hansen JO De Jager CW Jeschonnek S Jones MK Kuss M LeRose JJ Liang M Lindgren RA Malov S Meekins D Michaels R Mitchell J Perdrisat CF Punjabi V Roché R Sabatie F Saha A Suleiman R Todor L Wojtsekhowski BB 《Physical review letters》2002,89(6):062301
The 2H(e,e(')p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (x(Bj)=0.964) at a four-momentum transfer squared, Q(2)=0.665 (GeV/c) (2) (omega=0.368 GeV, W=2.057 GeV), and for recoil momenta up to 550 MeV/c. The measured cross section deviates by 1-2sigma from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations. 相似文献