scholarly journals Extraction of ALUsin(ϕ) moments from the hard exclusive π+ channel in a wide range of kinematics with CLAS

2020 ◽  
Vol 1643 (1) ◽  
pp. 012187
Author(s):  
Stefan Diehl ◽  
Kyungseon Joo
Keyword(s):  
Spin Asymmetry ◽  
Smooth Transition ◽  
Parton Distributions ◽  
Generalized Parton Distributions ◽  
Transition Distribution ◽  
Clear Sign ◽  
Sign Change ◽  
Wide Range ◽  
Large Acceptance ◽  
Beam Spin Asymmetry

Abstract The beam-spin asymmetry (BSA) has been measured for the hard exclusive e p → e n π+ reaction over a wide range of kinematics in the deep inelastic regime. The measurements were performed with the CEBAF Large Acceptance Spectrometer (CLAS) using a 5.5 GeV polarized electron beam at Jefferson Lab (JLAB). The ϕ dependence of the BSA as well as the −t, Q 2 and xB dependence of the extracted ALU sin(ϕ) moment will be presented. For ALU sin(ϕ) a clear sign change can be observed between pions emitted in forward and backward direction with a smooth transition around 90° in CM. The results will be discussed in the context of formalisms depending on generalized parton distributions (GPDs) and transition distribution amplitudes (TDAs), which can be used to describe complementary kinematic regimes.

CONCEPTUAL ISSUES CONCERNING GENERALIZED PARTON DISTRIBUTIONS

2013 ◽  
Vol 22 (02) ◽  
pp. 1330002 ◽  
Author(s):  
CHUENG-RYONG JI ◽  
BERNARD L. G. BAKKER
Keyword(s):  
Spin Asymmetry ◽  
Solvable Model ◽  
Deeply Virtual Compton Scattering ◽  
Exact Result ◽  
Theoretical Framework ◽  
Single Spin Asymmetry ◽  
Crossover Point ◽  
Parton Distributions ◽  
Single Spin ◽  
Generalized Parton Distributions

We review the interface between the current theoretical framework based on generalized parton distributions (GPDs) and experimental measurements of deeply virtual Compton scattering (DVCS) observables. We find that the present theoretical framework needs to be extended to cover the current and future DVCS experiments. The current formulation is based on the quantum chromodynamics factorization of the handbag diagrams, relying on handbag dominance. Our examination reveals that the handbag diagrams by themselves do not satisfy electromagnetic gauge invariance. Our numerical estimates of the DVCS amplitudes in a solvable model indicate that the handbag contribution is not sufficient to saturate the exact result. Assuming the extraction of GPDs is made, we analyzed the crossover point in GPDs, important for the single spin asymmetry seen in DVCS experiments. We found that the inclusion of the higher Fock states is essential to explain the available data of single spin asymmetry.

scholarly journals EXCLUSIVE π+ PRODUCTION AT HERMES

2005 ◽  
Vol 20 (02n03) ◽  
pp. 593-595 ◽  
Author(s):  
◽  
CYNTHIA HADJIDAKIS
Keyword(s):  
Cross Section ◽  
Spin Asymmetry ◽  
Positron Beam ◽  
Hydrogen Gas ◽  
Parton Distributions ◽  
Single Spin ◽  
Exclusive Production ◽  
Polarized Target ◽  
Generalized Parton Distributions ◽  
Gas Target

Hard exclusive production in deep inelastic lepton scattering provides access to the unknown Generalized Parton Distributions (GPDs) of the nucleon. At HERMES, the unpolarized total cross section for hard exclusive π+ production have been measured with a 27.6 GeV positron beam on an internal hydrogen gas target. First preliminary results for 1.5<Q2<10.5 GeV 2 and for 0.02<x<0.8 are presented and compared to GPD calculations. Forthcoming measurement for the single-spin asymmetry using a transversally polarized target is also reported.

QUARK ORBITAL ANGULAR MOMENTUM AND GENERALIZED PARTON DISTRIBUTIONS

2003 ◽  
Vol 18 (08) ◽  
pp. 1303-1309 ◽  
Author(s):  
XIANGDONG JI
Keyword(s):  
Angular Momentum ◽  
Quantum Chromodynamics ◽  
Orbital Angular Momentum ◽  
Parton Distributions ◽  
Generalized Parton Distributions ◽  
Quark Orbital Angular Momentum

In this talk, I review the merit of introducing and measuring the quark orbital angular momentum contribution to the spin of the nucleon in the context of quantum chromodynamics.

scholarly journals Moments of nucleon generalized parton distributions in lattice QCD

2003 ◽  
Vol 68 (3) ◽  
Author(s):  
Ph. Hägler ◽  
J. W. Negele ◽  
D. B. Renner ◽  
W. Schroers ◽  
Th. Lippert ◽  
...  
Keyword(s):  
Lattice Qcd ◽  
Parton Distributions ◽  
Generalized Parton Distributions
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