Measurement of the $\Upsilon$ polarizations in $pp$ collisions at $\sqrt{s}$=7 and 8TeV

TL;DR

This paper reports measurements of the polarization of $$Upsilon mesons produced in proton-proton collisions at 7 and 8 TeV, finding no significant polarization effects across various kinematic regions.

Contribution

First measurement of $$Upsilon polarization in $pp$ collisions at 7 and 8 TeV across multiple polarization frames.

Findings

No large polarization observed in $$Upsilon states.

Measurements consistent across different frames and energies.

Provides data for testing quarkonium production models.

Abstract

The polarization of the $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(3S) $mesons, produced in $pp$ collisions at centre-of-mass energies $\sqrt{s}$=7 and 8TeV, is measured using data samples collected by the LHCb experiment, corresponding to integrated luminosities of 1 and 2fb$^{-1}$, respectively. The measurements are performed in three polarization frames, using $\Upsilon\to\mu^+\mu^-$ decays in the kinematic region of the transverse momentum $p_{T}(\Upsilon)<30GeV/c$, and rapidity $2.2<y(\Upsilon)<4.5$. No large polarization is observed.