Measurement of $J/\psi$ polarization in $pp$ collisions at $\sqrt{s}=7$ TeV

TL;DR

This study measures the polarization of prompt J/ψ mesons produced in proton-proton collisions at 7 TeV using angular decay analysis, providing insights into quarkonium production mechanisms.

Contribution

It presents the first detailed polarization measurement of prompt J/ψ mesons as a function of transverse momentum and rapidity at 7 TeV.

Findings

Polarization varies with p_T and y.

Results challenge existing production models.

Provides data for refining QCD-based theories.

Abstract

An angular analysis of the decay $J/\psi \rightarrow \mu^{+} \mu^{-}$ is performed to measure the polarization of prompt $J/\psi$ mesons produced in $pp$ collisions at $\sqrt{s}=7\; \mathrm{TeV}$. The dataset corresponds to an integrated luminosity of 0.37 fb$^{-1}$ collected with the LHCb detector. The measurement is presented as a function of transverse momentum, $p_\mathrm{T}$, and rapidity, $y$, of the $J/\psi$ meson, in the kinematic region $2 < p_\mathrm{T} < 15\; \mathrm{GeV}/c$ and $2.0<y<4.5$.