Collins asymmetries for pion-in-jet production in polarized ell p collisions at the EIC
Pith reviewed 2026-05-08 18:06 UTC · model grok-4.3
The pith
Collins asymmetries for pion-in-jet production offer clearer access to transversity at the EIC
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Collins asymmetries in lepton-proton processes allow for a much clearer access to the transversity distribution, including its sea-quark component. Although the Weizsäcker-Williams quasireal photon exchange contributes across the kinematical range, it does not spoil the dominance of quark-initiated channels, leaving gluon counterparts with only a marginal role.
What carries the argument
The Collins azimuthal asymmetry for pion-in-jet production in a simplified TMD framework with transversity distributions and Collins fragmentation functions.
Load-bearing premise
Transversity and Collins fragmentation functions extracted from SIDIS and e+e- annihilation can be directly applied to lepton-proton collisions assuming TMD factorization and Collins universality.
What would settle it
Observation of Collins asymmetries in EIC data that significantly differ from those predicted using SIDIS and e+e- inputs would challenge the assumption of direct applicability and universality.
Figures
read the original abstract
We study Collins azimuthal asymmetries for pion-in-jet production in polarized lepton-proton collisions, extending previous analyses of polarized $pp$ scattering to a complementary and theoretically simpler process. We keep adopting a simplified transverse momentum dependent (TMD) approach, with a collinear configuration for the initial state, and employ the transversity and Collins fragmentation functions as extracted from semi-inclusive deep inelastic scattering and $e^+ e^-$ annihilation processes. We then compute azimuthal asymmetries for the Electron-Ion Collider (EIC) kinematics, both within a leading order (LO) approach and by including quasireal photon exchange in the Weizs\"acker-Williams approximation. Although this contribution is relevant in the whole kinematical range explored, it does not spoil the dominance of quark-initiated channels, leaving only a marginal role to their gluon counterparts. In this respect, Collins asymmetries in lepton-proton processes allow for a much clearer access to the transversity distribution, including its sea-quark component. As we will argue, a comparison with future EIC data could represent a further step in testing the hypothesis of the universality of the Collins function as well as of the TMD factorization for this class of processes.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper computes Collins azimuthal asymmetries for pion-in-jet production in polarized lepton-proton collisions at the EIC using a simplified TMD framework with collinear initial state. It inserts transversity and Collins functions previously extracted from SIDIS and e+e- annihilation, evaluates the asymmetries at leading order and with Weizsäcker-Williams quasireal photon exchange for EIC kinematics, and reports that quark-initiated channels dominate while gluon contributions remain marginal. This leads to the claim of clearer access to transversity, including its sea-quark component, with future EIC data comparison positioned as a test of TMD factorization and Collins universality.
Significance. If the reported dominance holds under the stated inputs, the work supplies concrete, falsifiable predictions for a process that is theoretically simpler than polarized pp scattering and could provide complementary constraints on transversity with reduced gluon contamination. The explicit numerical demonstration that the WW term, while relevant across the kinematics, does not alter the quark dominance is a clear strength of the analysis.
minor comments (1)
- Abstract: the phrase 'as we will argue' for clearer access to the sea-quark component of transversity should be accompanied by an explicit pointer to the section or figure containing the supporting numerical comparison of quark versus gluon channels.
Simulated Author's Rebuttal
We thank the referee for the careful reading of our manuscript and the positive overall assessment. We appreciate the recognition that our work supplies concrete predictions for a theoretically simpler process than polarized pp scattering and that the explicit demonstration of quark dominance (even with the Weizsäcker-Williams contribution) is a strength. We address the report below.
Circularity Check
No significant circularity; derivation uses independent prior extractions
full rationale
The paper inserts transversity and Collins functions previously extracted from SIDIS and e+e- data into a standard TMD framework (collinear initial state, LO hard scattering plus WW photons) to compute EIC asymmetries. The reported dominance of quark channels and clearer access to transversity (including sea) is a numerical outcome of that insertion, not a definitional equivalence or self-fit. No equations reduce the target prediction to the input parametrizations by construction, no uniqueness theorem is invoked from self-citation, and no ansatz is smuggled. The calculation is self-contained against external benchmarks from other processes; any future data comparison is presented as a test rather than an internal verification.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Universality of the Collins fragmentation function across processes
- domain assumption Validity of TMD factorization for this class of processes
discussion (0)
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