CMS-PAS-HIN-24-001

CMS-PAS-HIN-24-001
Observation of the multiplicity dependence of $ \sigma_{\psi(2S)}/\sigma_{J/\psi} $ in pPb collisions at 8.16 TeV
CMS Collaboration
12 June 2024

Abstract: The ratio of $ \psi(2S) $ and J/$ \psi $ meson production cross sections is measured as a function of the charged-particle multiplicity in pPb collisions at center-of-mass energy per nucleon pair of $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}} = $ 8.16 TeV using the CMS detector. The data corresponds to an integrated luminosity of 175 nb$^{-1}$. Both charmonium states are measured using the dimuon decay channel. The ratio is measured for both prompt and nonprompt $ \psi(2S) $ and J/$ \psi $ mesons separately. A multiplicity-dependent modification of the ratio is observed for prompt mesons. The ratio of the nonprompt $ \psi(2S) $ to J/$ \psi $ cross sections show no dependency on multiplicity. No significant rapidity-dependence is observed within the charmonium rapidity range $ -$2.865 $ < y_{CM} < $ 1.935 and transverse momentum range probed, 3 $ < p_{T} < $ 30 GeV. These measurements constrain hadronization models of heavy quarks in nuclear collisions and support a picture in which co-moving particles may preferentially dissociate weakly-bound charmonia excited states as compared to the ground state during the evolution of the system.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here.

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