Transverse spin structure of the nucleon through target single-spin asymmetry in semi-inclusive deep-inelastic (e, e’ $ \pi^{\pm}_{}$ ) reaction at Jefferson Lab

Abstract

Jefferson Lab (JLab) 12 GeV energy upgrade provides a golden opportunity to perform precision studies of the transverse spin and transverse-momentum-dependent structure in the valence quark region for both the proton and the neutron. In this paper, we focus our discussion on a recently approved experiment on the neutron as an example of the precision studies planned at JLab. The new experiment will perform precision measurements of target Single Spin Asymmetries (SSA) from semi-inclusive electro-production of charged pions from a 40-cm long transversely polarized 3 He target in Deep-Inelastic-Scattering kinematics using 11 and 8.8 GeV electron beams. This new coincidence experiment in Hall A will employ a newly proposed solenoid spectrometer (SoLID). The large acceptance spectrometer and the high polarized luminosity will provide precise 4-D (x, z, P T and Q 2 ) data on the Collins, Sivers, and pretzelosity asymmetries for the neutron through the azimuthal angular dependence. The full 2π azimuthal angular coverage in the lab is essential in controlling the systematic uncertainties. The results from this experiment, when combined with the proton Collins asymmetry measurement and the Collins fragmentation function determined from the e + e − collision data, will allow for a quark flavor separation in order to achieve a determination of the tensor charge of the d quark to a 10% accuracy. The extracted Sivers and pretzelosity asymmetries will provide important information to understand the correlations between the quark orbital angular momentum and the nucleon spin and between the quark spin and nucleon spin.

Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass

“…They have become the focus of planned experiments to search for physics beyond the familiar weak interactions of the Standard Model sought in the decay of ultracold neutrons [10]. The computation of the tensor charge is particularly timely since new experiments using polarized 3 He=Proton at Jefferson lab aim at increasing the experimental accuracy of its measurement by an order of magnitude [11]. In addition, experiments at the LHC are expected to increase the limits to contributions arising from tensor and scalar interactions by an order of magnitude making these observables interesting probes of new physics originating at the TeV scale.…”

Novel QCD Phenomena at the LHC: The Ridge, Digluon-Initiated Subprocesses, Direct Reactions, Non-Universal Antishadowing, and Forward Higgs Production

“…[42] The S -and P-wave proton wavefunctions also appear in the calculation of the Pauli form factor quarkby-quark. Thus one can correlate the Sivers asymmetry for each struck quark with the anomalous magnetic moment of the proton carried by that quark, [48] leading to the prediction that the Sivers effect is larger for positive pions as seen by the HERMES experiment at DESY, [49] the COMPASS experiment [50][51][52] at CERN, and CLAS at Jefferson Laboratory [53,54] The physics of the "lensing dynamics" or Wilson-line physics [55] underlying the Sivers effect involves nonperturbative quark-quark interactions at small momentum transfer, not the hard scale Q 2 of the virtuality of the photon. It would interesting to see if the strength of the soft initial-or final-state scattering can be predicted using the effective confining potential of QCD from light-front holographic QCD.…”

How classical gluon fields generate odd azimuthal harmonics for the two-gluon correlation function in high-energy collisions

“…The situation is not dissimilar to the single transverse spin asymmetry (STSA) which is observed in the scattering of the transversely polarized protons on the unpolarized ones and in semi-inclusive deep inelastic scattering (SIDIS) on a transversely polarized proton [67][68][69][70][71][72][73].…”