Two-hadron semi-inclusive production including subleading twist

TL;DR

Addresses extending the formalism of two-hadron fragmentation functions to subleading twist in semi-inclusive leptoproduction. Develops gauge-invariant quark-quark and quark-gluon-quark correlators, their twist-2 and twist-3 decompositions, and derives the hadronic tensor and cross sections for all polarization configurations. Demonstrates potential to access the transversity distribution with longitudinally polarized targets and to probe the twist-3 distribution e(x) via beam-spin and two-hadron asymmetries, including a partial-wave analysis to separate s- and p-wave contributions. Clarifies gauge-invariance issues, universality considerations, and provides a framework applicable to moderate $Q^2$ experiments.

Abstract

We extend the analysis of two-hadron fragmentation functions to the subleading twist, discussing also the issue of color gauge invariance. Our results can be used anywhere two unpolarized hadrons are semi-inclusively produced in the same fragmentation region, also at moderate values of the hard scale Q. Here, we consider the example of polarized deep-inelastic production of two hadrons and we give a complete list of cross sections and spin asymmetries up to subleading twist. Among the results, we highlight the possibility of extracting the transversity distribution with longitudinally polarized targets and also the twist-3 distribution e(x), which is related to the pion-nucleon sigma term and to the strangeness content of the nucleon.

Figures (5)

• Figure 1: Quark-quark correlation function $\Delta$ for the fragmentation of a quark with momentum $k$ into a pair of hadrons with total momentum $P_h=P_1+P_2$ and relative momentum $R=(P_1-P_2)/2$.
• Figure 2: Link structure for the leading-twist color gauge invariant quark-quark correlator for the fragmentation of a quark into a pair of hadrons.
• Figure 3: Relevant diagrams at leading and subleading twist for the SIDIS of a lepton on a hadronic target with detection of two hadrons in the same current fragmentation region. The shaded blobs understand the contribution of all unsuppressed longitudinal gluons, while the gluon lines represent all possible contributions from transverse gluon fields (see text).
• Figure 4: Kinematics for the SIDIS of the lepton $l$ on a (un)polarized target leading to two hadrons inside the same current jet.
• Figure 5: Description of the angles $\phi_{R}^{}$ and $\phi_{R \perp}^{}$ .