Study of coherent charmonium production in ultra-peripheral lead-lead collisions

Information

LHCb-PAPER-2022-012
CERN-EP-2022-108
arXiv:2206.08221 [PDF]

(Submitted on 16 Jun 2022)
JHEP 06 (2023) 146
Inspire 2096906

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Abstract

The cross-sections of exclusive (coherent) photoproduction $J/\psi$ and $\psi(\mathrm{2S})$ mesons in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of $5.02 \mathrm{TeV}$ are measured using a data sample corresponding to an integrated luminosity of $228\pm10 \mathrm{\mu b}^{-1}$, collected by the LHCb experiment in 2018. The differential cross-sections are measured separately as a function of transverse momentum and rapidity in the nucleus-nucleus centre-of-mass frame for $J/\psi$ and $\psi(\mathrm{2S})$ mesons. The integrated cross-sections are measured to be $\sigma^\mathrm{coh}_{J/\psi} = 5.965 \pm 0.059 \pm 0.232 \pm 0.262 \mathrm{mb}$ and $\sigma^\mathrm{coh}_{\psi(\mathrm{2S})} = 0.923 \pm 0.086 \pm 0.028 \pm 0.040 \mathrm{mb}$, where the first listed uncertainty is statistical, the second systematic and the third due to the luminosity determination. The cross-section ratio is measured to be $\sigma^\mathrm{coh}_{\psi(\mathrm{2S})}/\sigma^\mathrm{coh}_{J/\psi} = 0.155 \pm 0.014 \pm 0.003$, where the first uncertainty is statistical and the second is systematic. These results are compatible with theoretical predictions.

Figures and captions

Schematic diagrams for charmonium production in (a) coherent and (b) incoherent UPC heavy-ion collisions. For incoherent production, the pomeron is emitted from a single nucleon, indicated by the blue dot, and the nucleus typically dissociates, indicated by $A^*$.	Fig1.pdf [59 KiB] HiDef png [78 KiB] Thumbnail [70 KiB] *.C file
Dimuon mass distribution for signal candidates in the rapidity range $2.0<y^{*}<4.5$. The data are overlaid with the result of the fit.	Fig2.pdf [29 KiB] HiDef png [1006 KiB] Thumbnail [478 KiB] *.C file
The $\ln( p_{\mathrm{T}} ^{2})$ distribution of dimuon candidates in the $2.0<y^{}<4.5$ range for (left) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ candidates and (right) $\psi {(2S)}$ candidates. The data are overlaid with the result of the fit.	Fig3a.pdf [27 KiB] HiDef png [280 KiB] Thumbnail [225 KiB] *.C file
	Fig3b.pdf [21 KiB] HiDef png [267 KiB] Thumbnail [240 KiB] *.C file
Differential cross-section as a function $y^*$ for coherent (left) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} $ and (right) $\psi {(2S)}$ photoproduction, compared to theoretical predictions.	Fig4a.pdf [205 KiB] HiDef png [1 MiB] Thumbnail [602 KiB] *.C file
	Fig4b.pdf [205 KiB] HiDef png [690 KiB] Thumbnail [356 KiB] *.C file
Differential cross-section as a function of $ p_{\mathrm{T}} ^$ within the rapidity range $2<y^<4.5$ for coherent (left) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} $ and (right) $\psi {(2S)}$ photoproduction compared to theoretical predictions.	Fig5a.pdf [139 KiB] HiDef png [386 KiB] Thumbnail [241 KiB] *.C file
	Fig5b.pdf [135 KiB] HiDef png [364 KiB] Thumbnail [232 KiB] *.C file
Differential cross-section ratio of $\psi {(2S)}$ to $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ coherent photoproduction as a function of $y^*$, compared to theoretical predictions.	Fig6.pdf [140 KiB] HiDef png [408 KiB] Thumbnail [263 KiB] *.C file
Animated gif made out of all figures.	PAPER-2022-012.gif Thumbnail

Tables and captions

Total and coherent $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ and $\psi {(2S)}$ yields from the invariant mass and transverse momentum fits in different rapidity intervals.	Table_1.pdf [67 KiB] HiDef png [80 KiB] Thumbnail [38 KiB] tex code
Total and coherent $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ yields in different $ p_{\mathrm{T}} ^$ intervals within the rapidity range $2.0<y^<4.5$.	Table_2.pdf [67 KiB] HiDef png [159 KiB] Thumbnail [79 KiB] tex code
Total and coherent $\psi {(2S)}$ yields in different $ p_{\mathrm{T}} ^$ intervals within the rapidity range $2.0<y^<4.5$.	Table_3.pdf [68 KiB] HiDef png [117 KiB] Thumbnail [57 KiB] tex code
Summary of the systematic uncertainties.	Table_4.pdf [66 KiB] HiDef png [105 KiB] Thumbnail [46 KiB] tex code
The differential cross-section for coherent $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ production as a function of $y^*$.	Table_5.pdf [62 KiB] HiDef png [81 KiB] Thumbnail [38 KiB] tex code
The differential cross-section of coherent $\psi {(2S)}$ production as a function of $y^*$.	Table_6.pdf [63 KiB] HiDef png [81 KiB] Thumbnail [38 KiB] tex code
The differential cross-section ratio between $\psi {(2S)}$ and $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ coherent production as a function of $y^*$. The uncertainty due to luminosity determination cancels in the ratio.	Table_7.pdf [62 KiB] HiDef png [90 KiB] Thumbnail [43 KiB] tex code
The double differential cross-section of coherent $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ production as a function of $ p_{\mathrm{T}} ^$ in rapidity range $2.0<y^<4.5$.	Table_8.pdf [64 KiB] HiDef png [113 KiB] Thumbnail [40 KiB] tex code
The double differential cross-section of coherent $\psi {(2S)}$ production as a function of $ p_{\mathrm{T}} ^$ in rapidity range $2.0<y^<4.5$.	Table_9.pdf [64 KiB] HiDef png [75 KiB] Thumbnail [34 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [472 KiB]
This ZIP file contains supplemetary material for the publication LHCb-PAPER-2022-012. The files are: Supplementary.tex : An overview of the extra figures and tables Supplementary.pdf : An overview of the extra figures and tables .pdf, .png, *.eps : The figures in variuous formats	Fig1-S.pdf [129 KiB] HiDef png [154 KiB] Thumbnail [161 KiB] *C file
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