Azimuthal distributions of pions inside a jet in hadronic collisions

TL;DR

This paper investigates azimuthal distributions of pions within jets in hadronic collisions using a TMD approach, identifying asymmetries linked to spin effects and proposing tests for process dependence of the Sivers function.

Contribution

It introduces a method to isolate Collins and Sivers asymmetries in jet fragmentation, incorporating spin and intrinsic motion effects within a factorization framework.

Findings

Identification of leading-twist azimuthal asymmetries

Proposal to test process dependence of the Sivers function

Method to isolate Collins and Sivers contributions

Abstract

Using a generalized parton model approach including spin and intrinsic parton motion effects, and assuming the validity of factorization for large pT jet production in hadronic collisions, we study the azimuthal distribution around the jet axis of leading pions, produced in the jet fragmentation process. We identify the observable leading-twist azimuthal asymmetries, which are generated by all the physically allowed combinations of transverse momentum dependent (TMD) parton distribution and fragmentation functions. In particular, we show how one can isolate the Collins and Sivers contributions, and suggest a test of the process dependence of the Sivers function by considering the effect of color-gauge invariant initial and final state interactions.