Dihadron interference fragmentation functions in proton-proton collisions

TL;DR

This work develops a leading-twist, dihadron framework to probe nucleon spin structure in proton-proton collisions using interference fragmentation functions (IFF). In a single-pair final state with one transversely polarized proton, the single-spin asymmetry probes the convolution $f_1 \otimes h_1 \otimes H_1^{<{ )}}$, accessible through a $\sin(\phi_{S_B}-\phi_{R_C})$ modulation. In the two-pair case, unpolarized pp collisions yield azimuthal modulations $\cos(\phi_{R_C}-\phi_{R_D})$ and $\cos(2\phi_{R_C}-2\phi_{R_D})$, enabling simultaneous extraction of $H_1^{<{ )}}$ from each jet and, via $f_1 \otimes f_1$, access to gluon linear polarization through $\delta \hat{G}^{{<{ )}} }[]$; the formalism thus supports a potential global analysis of $h_1$ and IFF across $e^+e^-$, SIDIS, and hadronic processes. The results point to clean experimental tests at RHIC and future facilities, with implications for understanding hadronization and spin dynamics without TMD complications.

Abstract

We study the production of hadron pairs in proton-proton collisions, selecting pairs with large total transverse momentum with respect to the beam, and small relative transverse momentum, i.e., belonging to a single jet with large transverse momentum. We describe the process in terms of dihadron fragmentation functions. We consider the production of one pair in polarized collisions (with one transversely polarized proton) and the production of two pairs in unpolarized collisions. In the first case, we discuss how to observe the quark transversity distribution in connection with a specific class of dihadron fragmentation functions, named interference fragmentation functions. In the second case, we suggest how to determine the latter and also how to observe linearly polarized gluons.

Figures (1)

• Figure 1: Description of the kinematics for the proton-proton annihilation into a single pair in a jet.