Fraction of 𝜒𝑐 Decays in Prompt 𝐽/𝜓 Production Measured in 𝑝⁢Pb Collisions at √𝑠NN=8.16  TeV

Abstract

The fraction of χc1 and χc2 decays in the prompt J/ψ yield, Fχc→J/ψ=σχc→J/ψ/σJ/ψ, is measured by the LHCb detector in pPb collisions at sNN=8.16 TeV. The study covers the forward (1.5 <4.0) and backward (-5.0 <20 GeV/c. The Fχc→J/ψ fraction at forward rapidity is compatible with the LHCb measurement performed in pp collisions at s=7 TeV, whereas the result at backward rapidity is 2.4σ larger than in the forward region for 1 <3 GeV/c. The increase of Fχc→J/ψ at low pT,J/ψ at backward rapidity is compatible with the suppression of the ψ(2S) contribution to the prompt J/ψ yield. The lack of in-medium dissociation of χc states observed in this study sets an upper limit of 180 MeV on the free energy available in these pPb collisions to dissociate or inhibit charmonium state formation.