Azimuthal angle dependence of di-jet production in unpolarized hadron scattering

TL;DR

This paper investigates how the azimuthal angle between di-jets in unpolarized hadron collisions depends on the Boer-Mulders functions, revealing a color factor enhancement that affects the asymmetry's sign at RHIC.

Contribution

It demonstrates the azimuthal dependence of di-jet production due to Boer-Mulders functions and identifies a color factor enhancement in quark-quark processes affecting asymmetry predictions.

Findings

Azimuthal dependence manifests as a cos δφ term for identical quark or quark-antiquark jets.

Color factor enhancement increases the gluonic cross-section for J_q+J_q production.

Predicted asymmetry sign reversal at RHIC due to color factor effects.

Abstract

We study the azimuthal angular dependence of back-to-back di-jet production in unpolarized hadron scattering $H_A+H_B \to J_1 + J_2 +X$, arising from the product of two Boer-Mulders functions, which describe the transverse spin distribution of quarks inside an unpolarized hadron. We find that when the di-jet is of two identical quarks ($J_q+J_q$) or a quark-antiquark pair ($J_q+J_{\bar{q}}$), there is a $\cos \delta \phi$ angular dependence of the di-jet, with $\delta \phi=\phi_1-\phi_2$, and $\phi_1$ and $\phi_2$ are the azimuthal angles of the two individual jets. In the case of $J_q+J_q$ production, we find that there is a color factor enhancement in the gluonic cross-section, compared with the result from the standard generalized parton model. We estimate the $\cos \delta \phi$ asymmetry of di-jet production at RHIC, showing that the color factor enhancement in the angular dependent of $J_q+J_q$ production will reverse the sign of the asymmetry.