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 main 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” [Formula: see text]-ranges.
Highlights
Study of spin-dependent azimuthal asymmetries arising in the SIDIS and Drell-Yan cross-sections is a powerful method used to access Transverse Momentum Dependent (TMD) distribution functions of the nucleon
It is interesting to mention that for planned Drell-Yan measurements Sivers asymmetry in the ”high mass”-range is expected to have approximately same statistical accuracy as it’s SIDIS-analogue extracted from COMPASS proton-2010 data (≈ 1%)
Even if Sivers effect in Drell-Yan is a flagship measurement for COMPASS-II, other TSAs and their links with SIDIS ”analogues” from Table. 1 are very important for general TMD Parton Distribution Functions (PDFs)-studies
Summary
1. Introduction Study of spin-dependent azimuthal asymmetries arising in the SIDIS and Drell-Yan cross-sections is a powerful method used to access TMD distribution functions of the nucleon. The general form of the single-polarized (πN ↑) Drell-Yan cross-section (leading order part) in terms of angular variables defined in Collins-Soper and target rest frames (see Fig. 1) can be written in the following model-independent way:[4]
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