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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

Submission summary

As Contributors: Yu-Hsiang Lien
Preprint link: scipost_202107_00061v1
Code repository:
Data repository:
Date submitted: 2021-07-27 13:31
Submitted by: Lien, Yu-Hsiang
Submitted to: SciPost Physics Proceedings
Proceedings issue: DIS2021
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.

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Submission scipost_202107_00061v1 on 27 July 2021

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