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

Submission summary

 As Contributors: Yu-Hsiang Lien Preprint link: scipost_202107_00061v1 Code repository: https://www.dropbox.com/sh/cqverig41k4pldb/AAAkPGRmau0-XZjNJgPx3Ifta?dl=0 Data repository: https://www.dropbox.com/sh/cqverig41k4pldb/AAAkPGRmau0-XZjNJgPx3Ifta?dl=0 Date submitted: 2021-07-27 13:31 Submitted by: Lien, Yu-Hsiang Submitted to: SciPost Physics Proceedings Proceedings issue: DIS2021 Academic field: Physics Specialties: Nuclear Physics - Experiment Approach: Experimental

Abstract

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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