Moments of the neutrong2structure function at intermediateQ2

Abstract

We present new experimental results for the 3 He spin structure function g 2 in the resonance region at Q 2 values between 1.2 and 3.0 (GeV/c) 2 . Spin dependent moments of the neutron were extracted. Our main result, the inelastic contribution to the neutron d 2 matrix element, was found to be small at Q 2 = 2.4 (GeV/c) 2 and in agreement with the lattice QCD calculation. The Burkhardt-Cottingham sum rule for 3 He and the neutron was tested with the measured data and using the Wandzura-Wilczek relation for the low x unmeasured region.

Iterative Monte Carlo analysis of spin-dependent parton distributions

“…The inclusive polarized DIS experiments used in this analysis measured cross section asymmetries for lepton scattering from a stationary target with various combinations of target and lepton spin, with the latter always aligned or antialigned with the direction of the lepton beam. While some experiments also measured absolute cross section differences [17][18][19], here we only use the polarization asymmetries.…”

“…In Eqs. (19) and (20) the Q 2 dependence of the twist-3 function D is generated perturbatively [37,38], and in our analysis we use the large-N c approximation to describe the evolution of the moments D(N, Q 2 ) of the twist-3 functions in Mellin space,…”

“…18(b) and listed in Table V. In the case of the SLAC E155x experiment, the d 2 values are extrapolated from the measured region to x = 0 and x = 1, while in the Jefferson Lab experiments only the truncated moments over the measured regions are reported. With the exception of the E06-014 data [18], which partially extend into the DIS region, the truncated moments for the Jefferson Lab experiments [19,91,92] are restricted entirely to the nucleon resonance region.…”

“…In fixed-target deep-inelastic scattering (DIS) experiments, new high-precision data from Jefferson Lab on polarized protons [12][13][14][15], deuterons [15,16] and 3 He nuclei [17][18][19] are yielding a wealth of information on nucleon spin structure at lower energies. As well as improving the constraints on the large-x behavior of polarized PDFs, the new results are also providing new insights into nonperturbative quark-gluon interaction effects through higher twist contributions.…”

Accessing the nucleon transverse structure in inclusive deep inelastic scattering

“…is also interesting because the pure twist-3 part can be related to quark-gluon-quark local matrix elements, see [15], and interpreted as the average color force experienced by the struck quark as it exits the nucleon [50]; for experimental measurements of d 2 , see, e.g., Refs. [51][52][53][54][55]. For both the d 1 and d 2 moments, the transversity contribution is a background to the extraction of the pure twist-3 piece.…”