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arXiv · 2607.06821

Collins effect in pion-in-jet production in polarized $pp$ and $ep$ collisions

Carlo Flore·Umberto D'Alesio·Marco Zaccheddu
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Abstract

We study Collins azimuthal asymmetries for pion-in-jet production in polarized proton-proton and lepton-proton collisions. We adopt a hybrid transverse momentum dependent approach, with a collinear configuration for the initial state, and employ the transversity and Collins fragmentation functions extracted from semi-inclusive deep inelastic scattering and $e^+e^-$ annihilation data. After recalling the good description of the STAR data in $pp$ collisions, which supports the universality of the Collins function, we present predictions for Electron-Ion Collider kinematics, both at leading order and by including the quasireal photon exchange in the Weizs\"acker-Williams approximation. This contribution is sizable but does not spoil the dominance of quark-initiated channels. This implies that $\ell p$ processes allow for a clearer access to the transversity distribution, including its sea-quark component.

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Carlo Flore, Umberto D'Alesio, Marco Zaccheddu. 2026-07-07. Collins effect in pion-in-jet production in polarized $pp$ and $ep$ collisions. https://arxiv.org/abs/2607.06821

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