Fraction of ${\chi }_c$ decays in prompt $J/\psi$ production measured in pPb collisions at $\sqrt{s_{NN}}=8.16$ TeV

Abstract

The fraction of ${\chi }_{c1}$ and ${\chi }_{c2}$ decays in the prompt $J/\psi$ yield, $F_{\chi c}={\sigma }_{{\chi }_c\to J/\psi }/{\sigma }_{J/\psi }$, is measured by the LHCb detector in pPb collisions at $\sqrt{s_{NN}}=8.16$ TeV. The study covers the forward ($1.5<y^{\ast }<4.0$) and backward ($-5.0<y^{\ast }<-2.5$) rapidity regions, where $y^{\ast }$ is the $J/\psi$ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6 $\pm$ 0.3 nb${}^{-1}$ and 20.8 $\pm$ 0.5 nb${}^{-1}$, respectively. The result is presented as a function of the $J/\psi$ transverse momentum $p_{T,J/\psi }$ in the range 1$<p_{T,J/\psi }<20$ GeV/$c$. The $F_{\chi c}$ fraction at forward rapidity is compatible with the LHCb measurement performed in $pp$ collisions at $\sqrt{s}=7$ TeV, whereas the result at backward rapidity is 2.4 $\sigma$ larger than in the forward region for $1<p_{T,J/\psi }<3$ GeV/$c$. The increase of $F_{\chi c}$ at low $p_{T,J/\psi }$ at backward rapidity is compatible with the suppression of the $\psi$(2S) contribution to the prompt $J/\psi$ yield. The lack of in-medium dissociation of ${\chi }_c$ 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.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-028.html (LHCb public pages)

References in corpus (6)

• Prompt and nonprompt J/$\psi$ production and nuclear modification in $p$Pb collisions at $\sqrt{s_{\text{NN}}}=8.16$ TeV
• Measurement of the ratio of prompt ${\chi }_c$ to $J/\psi$ production in $pp$ collisions at $\sqrt{s}=7$ TeV
• Production of the Charmonium States chic_1 and chic_2 in Proton Nucleus Interactions at sqrt{s} = 41.6 GeV
• System Size and Flavour Dependence of Chemical Freeze-out Temperatures in ALICE Data from pp, pPb and PbPb Collisions at LHC Energies
• Constraints on the ${\chi }_{c1}$ versus ${\chi }_{c2}$ polarizations in proton-proton collisions at $\sqrt{s}=$ 8 TeV
• Measurement of the prompt-production cross-section ratio $\sigma ({\chi }_{c2})/\sigma ({\chi }_{c1})$ in $p$Pb collisions at $\sqrt{s_{NN}}$ = 8.16 TeV

Cited by in corpus (3)

• Production of exotic hadrons in $pp$ and nuclear collisions
• Measurement of exclusive $J/\psi$ and $\psi (2S)$ production at $\sqrt{s}=13$ TeV
• Physics with high-luminosity proton-nucleus collisions at the LHC