Beam-Target Double-Spin AsymmetryALTin Charged Pion Production from Deep Inelastic Scattering on a Transversely PolarizedHe3Target at

J. Huang¹,

K. Allada²,

C. Dutta³

et al.

Abstract

We report the first measurement of the double-spin asymmetry A{LT} for charged pion electroproduction in semi-inclusive deep-inelastic electron scattering on a transversely polarized {3}He target. The kinematics focused on the valence quark region, 0.16<x<0.35 with 1.4<Q{2}<2.7 GeV{2}. The corresponding neutron A{LT} asymmetries were extracted from the measured {3}He asymmetries and proton over {3}He cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g{1T}{q} and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for π{-} production on {3}He and the neutron, while our π{+} asymmetries are consistent with zero.

Three-dimensional imaging of the nucleon and semi-inclusive high-energy reactions

“…The Hall A Collaboration has measured [81][82][83][84] the Collins and Sivers asymmetries for π ± and K ± , and cos(φ h − φ s ) LT for π ± and sin(3φ h − φ s ) UT . These measurements are all summarized in Table 5.…”

“…Here, we will just briefly summarize the main data available and then try to sort out the available TMD parameterizations. For SIDIS, measurements have been made by the HERMES Collaboration [66][67][68][69][70] at DESY, the COM-PASS Collaboration [71][72][73][74][75][76][77][78] at CERN, CLAS [79,80], and the Hall A Collaboration [81][82][83][84] at Jefferson Laboratory (JLab). We list these SIDIS experiments in Table 5 and briefly summarize the results as follows.…”

“…(2) Sivers function: All the data available from HER-MES [67][68][69], COMPASS [71-74, 76, 77], and JLab Hall A [81,82,84] on the Sivers asymmetries in SIDIS for pions and kaons have been used for parameterization. The Sivers function is usually parameterized [96,[101][102][103][104][105][106] in the form of the number density f q (x, k ⊥ ) multiplied by an x-dependent factor N q (x) and a k ⊥ -dependent factor h(k ⊥ ), i.e.,…”

The extraction of the spin structure function, g2 (and g1) at low Bjorken x

“…The spin structure function g 1 (and g 2 ) is extracted from the measured asymmetries of the scattering cross section as the beam or target spin is reversed. It should be noted that g 1 (and g 2 ) can also be extracted from differences of polarized cross section [27]. These asymmetries are measured with longitudinally polarized beams and longitudinally (A � ) and transversely (A ⊥ ) polarized targets …”

“…Partons can be any particles with no internal structure and must be interacting in order to prevent the nucleon from falling apart. To calculate the hadronic tensor, we sum over scattering on partons 27) where x F P is the longitudinal momentum carried by a parton, f (x F ) is the parton density and ω µν is the hadron tensor for a single quark. Taking into consideration the contribution of the anti quark…”