Polarized Drell-Yan at COMPASS-II: Transverse Spin Physics Program

TL;DR

The paper discusses the upcoming polarized Drell-Yan measurements at COMPASS-II, aiming to test TMD PDFs universality and connect SIDIS and Drell-Yan spin asymmetries, enhancing understanding of nucleon spin structure.

Contribution

It presents the experimental plan for polarized Drell-Yan at COMPASS-II and its significance in testing TMD PDFs and linking SIDIS and Drell-Yan results.

Findings

Preparation of polarized Drell-Yan measurements at COMPASS-II.

Expected to test TMD PDFs universality.

Linking SIDIS and Drell-Yan spin asymmetries.

Abstract

Successful realization of polarized Drell-Yan physics program is one of the main goals of the second stage of the COMPASS experiment. Drell-Yan measurements with high energy (190 GeV/c) pion beam and transversely polarized NH3 target have been initiated by a pilot-run in the October 2014 and will be followed by 140 days of data taking in 2015. In the past twelve years COMPASS experiment performed series of SIDIS measurements with high energy muon beam and transversely polarized deuteron and proton targets. Results obtained for Sivers effect and other target transverse spin dependent and unpolarized azimuthal asymmetries in SIDIS serve as an important input for general understanding of spin-structure of the nucleon and are being used in numerous theoretical and phenomenological studies being carried out in the field of transvers-spin physics. Measurement of the Sivers and all other azimuthal effects in polarized Drell-Yan at COMPASS will reveal another side of the spin-puzzle providing a link between SIDIS and Drell-Yan branches. This will be a unique possibility to test universality and key-features of transverse momentum dependent distribution functions (TMD PDFs) using essentially same experimental setup and exploring same kinematic domain. In this review man physics aspects of future COMPASS polarized Drell-Yan measurement of azimuthal transverse spin asymmetries will be presented, giving a particular emphasis on the link with very recent COMPASS results obtained for SIDIS transverse spin asymmetries from four "Drell-Yan" $Q^2$-ranges.