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

Abstract

We have studied J/psi production in pp collisions at $\sqrt{s}=7$ TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/$ψ$ polarization parameters $λ_θ$ and $λ_ϕ$ were obtained. The study was performed in the kinematic region 2.5<y<4, 2<$p_{\rm T}$<8 GeV/$c$, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.

15 pages, 3 captioned figures, 1 table, authors from page 10, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/3503