π-N Drell-Yan Process in TMD Factorization

Xiaoyu Wang,Zhun Lu

doi:10.1155/2019/6734293

Xiaoyu Wang, Zhun Lu

Open Access

https://doi.org/10.1155/2019/6734293

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Abstract

This article presents the review of the current understanding on the pion-nucleon Drell-Yan process from the point of view of the TMD factorization. Using the evolution formalism for the unpolarized and polarized TMD distributions developed recently, we provide the theoretical expression of the relevant physical observables, namely, the unpolarized cross section, the Sivers asymmetry, and the cos⁡2ϕ asymmetry contributed by the double Boer-Mulders effects. The corresponding phenomenology, particularly at the kinematical configuration of the COMPASS πN Drell-Yan facility, is displayed numerically.

Highlights

After the first observation of the μ+μ− lepton pairs produced in pN collisions [1], the process was interpreted that a quark and an antiquark from each initial hadron annihilate into a virtual photon, which in turn decays into a lepton pair [2]
A new pion-induced Drell-Yan program with polarized target was proposed [10] at the COMPASS of CERN, and the first data using a high-intensity π beam of 190 GeV colliding on a NH3 target has already come out [11]
We find from the plots that, in the transverse momentum dependent (TMD) formalism, the cos 2φ azimuthal asymmetry in the unpolarized π−p Drell-Yan process contributed by the Boer-Mulders functions is around several percent

Summary

Introduction

After the first observation of the μ+μ− lepton pairs produced in pN collisions [1], the process was interpreted that a quark and an antiquark from each initial hadron annihilate into a virtual photon, which in turn decays into a lepton pair [2]. It has been explained from the viewpoints of higher-twist effect [50,51,52,53], the noncoplanarity effect [30, 54], and the QCD radiative effects at higher order [55, 56] Another promising origin [57] for the violation of the LamTung relation at low transverse momentum is the convolution of the two Boer-Mulders functions [58] from each hadron.

The TMD Evolution of the Distribution Functions

Physical Observables in πN Drell-Yan Process within TMD Factorization

Numerical Estimate for the TMD Distributions

Numerical Estimate for the Physical Observables in π-N Drell-Yan Process

Summary and Prospects