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New Quark Distributions and Semi-Inclusive Electroproduction on Polarized Nucleons

Aram Kotzinian

TL;DR

The work addresses how to access all six twist-two quark distributions in polarized nucleons by incorporating intrinsic transverse momentum into the quark-parton model and analyzing semi-inclusive DIS. It develops a comprehensive framework for polarized SIDIS cross sections, including the Collins fragmentation effect, and shows how azimuthal and spin asymmetries can probe new distributions such as g1T and h1L^⊥ at leading twist. The study derives explicit cross-section decompositions (C_UP, C_DP, C_SP) and connects them to standard DIS structure functions, highlighting that g2^DIS receives twist-two contributions from g1L and g1T. The results provide a practical path for extracting the new distributions from SIDIS data, with potential application to existing experiments like SMC and future HELP/HERMES measurements.

Abstract

The quark-parton model calculation including the effects of intrinsic transverse momentum and of all six twist-two distribution functions of quarks in polarized nucleons is performed. It is demonstrated that new twist-two quark distribution functions and polarized quark fragmentation functions can be investigated in semi-inclusive DIS at leading order in $Q^2$. The general expression for the cross-section of semi-inclusive DIS of polarized leptons on polarized nucleons in terms of structure functions is also discussed.

New Quark Distributions and Semi-Inclusive Electroproduction on Polarized Nucleons

TL;DR

The work addresses how to access all six twist-two quark distributions in polarized nucleons by incorporating intrinsic transverse momentum into the quark-parton model and analyzing semi-inclusive DIS. It develops a comprehensive framework for polarized SIDIS cross sections, including the Collins fragmentation effect, and shows how azimuthal and spin asymmetries can probe new distributions such as g1T and h1L^⊥ at leading twist. The study derives explicit cross-section decompositions (C_UP, C_DP, C_SP) and connects them to standard DIS structure functions, highlighting that g2^DIS receives twist-two contributions from g1L and g1T. The results provide a practical path for extracting the new distributions from SIDIS data, with potential application to existing experiments like SMC and future HELP/HERMES measurements.

Abstract

The quark-parton model calculation including the effects of intrinsic transverse momentum and of all six twist-two distribution functions of quarks in polarized nucleons is performed. It is demonstrated that new twist-two quark distribution functions and polarized quark fragmentation functions can be investigated in semi-inclusive DIS at leading order in . The general expression for the cross-section of semi-inclusive DIS of polarized leptons on polarized nucleons in terms of structure functions is also discussed.

Paper Structure

This paper contains 10 sections, 58 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Structure functions for polarized SIDIS
  3. Parton model with intrinsic transverse momentum
  4. The initial quark state.
  5. Noncoplanar polarized $l+q\rightarrow l'+q'$ scattering
  6. Polarized quark fragmentation.
  7. Results
  8. Discussion
  9. Examples of the target spin asymmetries.
  10. Conclusions

Figures (3)

  • Figure 1: Lowest order diagram for SIDIS.
  • Figure 2: Lepton and produced hadron momenta in the LGHF.
  • Figure 3: The quark-parton model picture for SIDIS in the BF.