J/ψPolarization inppCollisions ats=7  TeV

Abstract

The ALICE Collaboration has studied J=c production in pp collisions at ffiffi ffi s p ¼ 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=c polarization parameters and were obtained. The study was performed in the kinematic region 2:5 < y < 4, 2 < p t < 8 GeV=c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.

Differential studies of inclusive J/ψ and ψ(2S) production at forward rapidity in Pb-Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

“…In pp collisions at √ s = 7 TeV, J/ψ polarization measurements at mid-rapidity (p t > 10 GeV/c) and forward-rapidity (p t > 2 GeV/c) are compatible with zero [51][52][53]. In Pb-Pb collisions, J/ψ mesons produced from initial parton-parton hard scattering are expected to have the same polarization as in pp collisions and those produced from charm quarks recombination in the medium are expected to be unpolarized.…”

Production of J/ψ and $ \varUpsilon $ mesons in pp collisions at $ \sqrt{s}=8 $ TeV

“…Previous studies [12,13] by the LHCb [42] and ALICE [43] collaborations, in a kinematic range similar to that used in this analysis, and the Υ polarisation has been measured by CMS [44] at large p T and central rapidity. They were both found to be small.…”

Transverse Momentum Dependent Fragmenting Jet Functions with Applications to Quarkonium Production

“…The predicted polarization disagrees with measurements of the J/ψ polarization: while the fitted LDME at large p T predict almost transverse polarization, data suggest effectively no polarization [5,6,7]. This disagreement is partially attributed to the fact that at large p T fragmentation processes, that for some of the four leading production mechanisms appear first time at NNLO,…”