Modification of $\chi_{c1}$(3872) and $\psi$(2$S$) production in $p$Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV

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LHCb-PAPER-2023-026
CERN-EP-2024-033
arXiv:2402.14975 [PDF]

(Submitted on 22 Feb 2024)
PRL
Inspire 2761514

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Abstract

The LHCb collaboration measures production of the exotic hadron $\chi_{c1}$(3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state $\psi$(2$S$) suggests that the exotic $\chi_{c1}$(3872) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify $\chi_{c1}$(3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron.

Figures and captions

Invariant mass spectra of $ { J \mskip -3mu/\mskip -2mu\psi } \pi ^+ \pi ^- $ candidates measured in a) $pp$, b) $p$Pb, and c) Pb$p$ collisions, with fit projections overlaid.	Fig1.pdf [90 KiB] HiDef png [467 KiB] Thumbnail [447 KiB]
Ratio of $\chi _{c1}(3872) $ to $\psi {(2S)} $ cross-sections in the $ { J \mskip -3mu/\mskip -2mu\psi } \pi ^+ \pi ^- $ decay channel, measured in $pp$ [13], $p$Pb, Pb$p$, and PbPb [16] data. The error bars (boxes) represent the statistical (systematic) uncertainties on the ratio.	Fig2.pdf [14 KiB] HiDef png [148 KiB] Thumbnail [121 KiB]
Nuclear modification factor $R_{p \rm Pb}$ for $\chi _{c1}(3872) $ and $\psi {(2S)} $ hadrons [57]. The error bars (boxes) represent the statistical (systematic) uncertainties.	Fig3.pdf [14 KiB] HiDef png [138 KiB] Thumbnail [135 KiB]
Animated gif made out of all figures.	PAPER-2023-026.gif Thumbnail