Beam Spin Asymmetries of $\pi^+\pi^0$ Dihadrons from SIDIS at CLAS12

TL;DR

This paper reports the first empirical evidence of nonzero spin-dependent dihadron fragmentation functions in SIDIS at CLAS12, using measurements of beam spin asymmetries of $ ext{π}^+ ext{π}^0$ dihadrons to explore nucleon structure and hadronization.

Contribution

It introduces new measurements of beam spin asymmetries for $ ext{π}^+ ext{π}^0$ dihadrons, extending the understanding of dihadron fragmentation functions and their dependence on parton transverse spin.

Findings

First empirical evidence of nonzero $G_1^ot$ in dihadrons.

Extended measurements to $ ext{π}^+ ext{π}^0$ and $ ext{π}^- ext{π}^0$ dihadrons.

Differences in DiFFs between $ ext{π}^+ ext{π}^-$ and $ ext{π}^+ ext{π}^0$ production.

Abstract

Spin asymmetries provide a wide range of insights into nucleon structure and hadronization. Recent measurements of beam spin asymmetries of $\pi^+\pi^-$ dihadrons from Semi-Inclusive Deep Inelastic Scattering (SIDIS) at CLAS12 provide the first empirical evidence of a nonzero $G_1^\perp$, the parton helicity-dependent Dihadron Fragmentation Function (DiFF) encoding spin-momentum correlations in hadronization. These measurements have been extended to aid in the characterization of $H_1^\perp$ and $H_1^\sphericalangle$, the DiFFs dependent on parton transverse spin, via a multidimensional partial wave analysis, giving access to the dependence on the interference of dihadrons of particular polarizations. Reconstruction of $\pi^0$s allows for further extension of these measurements to $\pi^+\pi^0$ and $\pi^-\pi^0$ dihadrons. The DiFFs describing $\pi^+\pi^-$ production differ from those describing $\pi^+\pi^0$ and $\pi^-\pi^0$ production, which involve different quark flavors along with a strong suppression of the exclusive diffractive contribution. This presentation will focus on beam spin asymmetries for $\pi^+\pi^0$ dihadrons, compared to those from $\pi^+\pi^-$ dihadrons, which will help shed light on a more comprehensive picture of dihadron fragmentation.