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 [1,36,4,41,42]. The measurements are shown as points, where inner and outer error bars represent the statistical and the total uncertainties, respectively. This includes the uncertainty on the luminosity and is therefore highly correlated.	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 [15 KiB] HiDef png [110 KiB] Thumbnail [85 KiB] *C file
	Fig6.pdf [15 KiB] HiDef png [193 KiB] Thumbnail [125 KiB] *C file
	Fig7.pdf [15 KiB] HiDef png [253 KiB] Thumbnail [162 KiB] *C file
	Fig8.pdf [14 KiB] HiDef png [130 KiB] Thumbnail [100 KiB] *C file
	Fig9.pdf [14 KiB] HiDef png [134 KiB] Thumbnail [103 KiB] *C file
	LHCb-P[..].pdf [220 KiB] HiDef png [460 KiB] Thumbnail [223 KiB] *C file