Compact Muon Solenoid
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| CMS-PAS-HIN-19-005 | ||
| Evidence for $\chi_{c1}\text{(3872)}$ in PbPb collisions and studies of its prompt production at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}=$ 5.02 TeV | ||
| CMS Collaboration | ||
| November 2019 | ||
| Abstract: The first evidence for $\chi_{c1}\text{(3872)}$ in relativistic heavy ion collisions is reported. Prompt $\chi_{c1}\text{(3872)}$ production is studied in PbPb collisions at a center-of-mass energy of ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV per nucleon pair, using the decay chain $\chi_{c1}\text{(3872)} \rightarrow {\rm J}/\psi\pi^+\pi^-\rightarrow \mu^+\mu^-\pi^+\pi^-$. The data were recorded by the CMS detector in 2018 and correspond to an integrated luminosity of 1.7 $\pm$ 0.1 nb$^{-1}$. The measurement is performed in a kinematic range in which the $\chi_{c1}\text{(3872)}$ candidates have a transverse momentum 15 $ < p_{\mathrm{T}} < $ 50 GeV/$c$ and rapidity $|y| < $ 1.6. The statistical significance of the $\chi_{c1}\text{(3872)}$ signal is in excess of 3 standard deviations. The production and survival of the prompt $\chi_{c1}\text{(3872)}$ in the quark-gluon plasma is expected to depend upon its internal structure. The ratio of the $\chi_{c1}\text{(3872)}$ and $\psi\text{(2S)}$ yields is found to be $R = $ 1.10 $\pm$ 0.51(stat) $\pm$ 0.53 (syst). This results is compared to the similar ratio measured in pp collisions at $\sqrt{s} = $ 7 and 8 TeV. An indication of larger $R$ in PbPb collisions with respect to the pp reference is reported. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
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These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here.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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Compact Muon Solenoid LHC, CERN |
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