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Measurement of Target Spin (in)dependent Asymmetries in Dimuon Production in Pion-Nucleon Collisions at COMPASS

by Yu-Hsiang Lien and Alexandr Chumakov

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Submission summary

Authors (as registered SciPost users): Yu-Hsiang Lien
Submission information
Preprint Link: scipost_202107_00061v1  (pdf)
Code repository:
Data repository:
Date accepted: 2022-05-06
Date submitted: 2021-07-27 13:31
Submitted by: Lien, Yu-Hsiang
Submitted to: SciPost Physics Proceedings
Proceedings issue: 28th Annual Workshop on Deep-Inelastic Scattering (DIS) and Related Subjects (DIS2021)
Ontological classification
Academic field: Physics
  • Nuclear Physics - Experiment
Approach: Experimental


The exploration of the transverse spin structure of the nucleon is one of the main topics of the COMPASS phase-II experiment. In 2015 and 2018 COMPASS performed Drell–Yan (DY) measurements using a 190 GeV π− beam interacting with a transversely polarized NH3 target and unpolarized W target. The azimuthal asymmetries in DY with trans- versely polarized NH3 target are sensitive to various transverse momentum dependent parton distribution functions. Preliminary results on the Sivers asymmetry are consis- tent with the QCD prediction for a sign-change of Sivers functions in DY. The angular coefficients λ, μ and ν that describe the unpolarized part of the DY cross section have been extracted from the data collected with W target. The preliminary results on the angular coefficients indicate the violation of the Lam–Tung relation, consistent with the observation in earlier DY experiments with pion beams.

Published as SciPost Phys. Proc. 8, 028 (2022)

Reports on this Submission

Anonymous Report 1 on 2022-2-28 (Invited Report)


This paper is clear and thorough, giving an excellent description of the COMPASS Drell-Yan measurements on a polarized NH_3 target and an unpolarized W target. The preliminary results indicate a violation of the Lam-Tung relation, consistent with earlier observations. The detail in the paper is sufficient for this journal and can be published without further changes.

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