Study of coherent $J/\psi$ production in lead-lead collisions at $\sqrt{s_{NN}}=5$ TeV

Information

LHCb-PAPER-2021-013
CERN-EP-2021-108
arXiv:2107.03223 [PDF]

(Submitted on 07 Jul 2021)
JHEP 07 (2022) 117
Inspire 1877981

Tools

Abstract

Coherent production of $J/\psi$ mesons is studied in ultraperipheral lead-lead collisions at a nucleon-nucleon centre-of-mass energy of 5 TeV, using a data sample collected by the LHCb experiment corresponding to an integrated luminosity of about $10 \mu b^{-1}$. The $J/\psi$ mesons are reconstructed in the dimuon final state and are required to have transverse momentum below 1 GeV. The cross-section within the rapidity range of $2.0 < y < 4.5$ is measured to be $4.45\pm0.24\pm0.18\pm0.58$ mb, where the first uncertainty is statistical, the second systematic and the third originates from the luminosity determination. The cross-section is also measured in $J/\psi$ rapidity intervals. The results are compared to predictions from phenomenological models.

Figures and captions

Illustration of the (left) coherent scatter with the lead nucleus and (right) incoherent interaction with a single nucleon leading to exclusive production of $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ mesons in ultraperipheral heavy-ion collisions. The symbol Pb' represents any final state for the nucleus inelastic scattering in the incoherent process.	Fig1a.pdf [24 KiB] HiDef png [129 KiB] Thumbnail [97 KiB] *.C file
	Fig1b.pdf [24 KiB] HiDef png [137 KiB] Thumbnail [102 KiB] *.C file
The dimuon invariant mass spectrum in the range between $2.7$ and $4.0\mathrm{ Ge V} $. The contribution of $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ (solid purple line) and $\psi {(2S)}$ (solid dark green line) mesons, and non-resonant background (dashed black line) are shown individually along with the sum of all contributions (solid orange line).	Fig2.pdf [23 KiB] HiDef png [204 KiB] Thumbnail [162 KiB] *.C file
The $\log( p_{\mathrm{ T}}^{2} )$ distribution of dimuon candidates in the interval $2.5<y<3.0$, with $ p_{\mathrm{ T}}$ given in GeV, after all requirements have been applied. The solid orange line represents the combined fit to data; the solid blue line shows the coherent contribution; the incoherent component is displayed by the dashed red line; and the dashed green (black) line shows the feed-down (nonresonant) components. \color{red}	Fig3.pdf [357 KiB] HiDef png [198 KiB] Thumbnail [145 KiB] *.C file
Differential cross-section as a function of rapidity for coherent $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ production compared to different phenomenological predictions [1,31,36,37,4]. The measurements are shown as points, where inner and outer error bars represent the statistical and the total uncertainties, respectively.	Fig4.pdf [16 KiB] HiDef png [335 KiB] Thumbnail [211 KiB] *.C file
Animated gif made out of all figures.	PAPER-2021-013.gif Thumbnail

Tables and captions

Total and coherent $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ yields after the invariant mass and the transverse momentum fits, in $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ rapidity intervals.	Table_1.pdf [44 KiB] HiDef png [54 KiB] Thumbnail [28 KiB] tex code
Systematic uncertainties considered for the differential cross-section measurement of coherent $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ production, relative to the central value. Uncertainty ranges correspond to variation over the rapidity intervals. The dominant uncertainty arises from the luminosity determination and is correlated over all intervals.	Table_2.pdf [48 KiB] HiDef png [80 KiB] Thumbnail [35 KiB] tex code
Measured cross-section $\sigma$ with breakdown of statistical, systematic and luminosity uncertainties measured as a function of the $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ rapidity. Note that the cross-sections are not normalised by the $y$ interval width.	Table_3.pdf [44 KiB] HiDef png [58 KiB] Thumbnail [28 KiB] tex code

Supplementary Material [file]

This file is part of LHCb-PAPER-2021-13 The paper and additional information can be found on the CERN document server: https://cds.cern.ch/search?p=LHCb-PAPER-2021-013 and the LHCb public website: https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2021-013.html	Fig5.pdf [14 KiB] HiDef png [99 KiB] Thumbnail [80 KiB] *C file
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