Measurement of Angular Distributions of Drell-Yan Dimuons in $p + p$ Interactions at 800 GeV/c

TL;DR

This paper measures angular distributions of Drell-Yan dimuons in 800 GeV/c proton-proton interactions, analyzing the underlying mechanisms and testing theoretical relations in high-energy particle physics.

Contribution

It provides the first detailed measurement of angular parameters in $p+p$ Drell-Yan processes at this energy, comparing data with models involving Boer-Mulders functions and QCD effects.

Findings

Angular distributions are similar in $p+p$ and $p+d$ interactions.

Data supports the presence of both Boer-Mulders and QCD mechanisms.

The Lam-Tung relation is tested and found consistent within uncertainties.

Abstract

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range $4.5 < m_{\mu \mu} < 15$ GeV/c$^2$ (excluding the $\Upsilon$ resonance region), $0 < p_T < 4 $ GeV/c, and $0 < x_F < 0.8$. The $p+p$ angular distributions are similar to those of $p+d$, and both data sets are compared with models which attribute the $\cos 2 \phi$ distribution either to the presence of the transverse-momentum-dependent Boer-Mulders structure function $h_1^\perp$ or to QCD effects. The data indicate the presence of both mechanisms. The validity of the Lam-Tung relation in $p+p$ Drell-Yan is also tested.