Observation of enhanced double parton scattering in proton-lead collisions at $\sqrt{s_\mathrm{NN}}=8.16$ TeV

Information

LHCb-PAPER-2020-010
CERN-EP-2020-119
arXiv:2007.06945 [PDF]

(Submitted on 14 Jul 2020)
Phys. Rev. Lett. 125 (2020) 212001
Inspire 1806797

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Abstract

A study of prompt charm-hadron pair production in proton-lead collisions at $\sqrt{s_\mathrm{NN}}= 8.16$ TeV is performed using data corresponding to an integrated luminosity of about 30 nb${}^{-1}$, collected with the LHCb experiment. Production cross-sections for different pairs of charm hadrons are measured and kinematic correlations between the two charm hadrons are investigated. This is the first measurement of associated production of two charm hadrons in proton-lead collisions. The results confirm the predicted enhancement of double parton scattering production in proton-lead collisions compared to the single parton scattering production.

Figures and captions

(Left) Two-dimensional invariant-mass distributions of $(m_1, m_2)$ for $ D ^0 D ^0 $ pairs and the projections on (middle) $m_1$ and (right) $m_2$ with the fit results superimposed. Shown in the projection plots are (points with bars) $ p\mathrm{Pb}$ data, (solid blue) the total fit and its four components.	Fig1a.pdf [15 KiB] HiDef png [236 KiB] Thumbnail [259 KiB] *.C file
	Fig1b.pdf [31 KiB] HiDef png [227 KiB] Thumbnail [169 KiB] *.C file
Two-charm hadron invariant-mass distribution of (red) $ D ^0 D ^0 $ and (blue) $ D ^0 \overline{ D } {}^0 $ pairs in (left) $ p\mathrm{Pb}$ , (right) $\mathrm{Pb}p$ data and (magenta dashed line) Pythia8 simulation. Vertical bars (filled box) are statistical (systematic) uncertainties.	Fig2a.pdf [15 KiB] HiDef png [246 KiB] Thumbnail [190 KiB] *.C file
	Fig2b.pdf [15 KiB] HiDef png [242 KiB] Thumbnail [189 KiB] *.C file
The $\Delta \phi$ distribution for (red) $ D ^0 D ^0 $ and (blue) $ D ^0 \overline{ D } {}^0 $ pairs in (left) $ p\mathrm{Pb}$ , (right) $\mathrm{Pb}p$ data and the (magenta dashed line) Pythia8 simulation, (bottom) with and (top) without the $ p_{\mathrm{T}} ( D ^0 )>2\text{ Ge V /}c $ requirement. Vertical bars (filled box) are statistical (systematic) uncertainties.	Fig3a.pdf [15 KiB] HiDef png [219 KiB] Thumbnail [171 KiB] *.C file
	Fig3b.pdf [15 KiB] HiDef png [215 KiB] Thumbnail [169 KiB] *.C file
	Fig3c.pdf [15 KiB] HiDef png [236 KiB] Thumbnail [185 KiB] *.C file
	Fig3d.pdf [15 KiB] HiDef png [231 KiB] Thumbnail [186 KiB] *.C file
(Left) Two-dimensional invariant-mass distributions of $(m_1, m_2)$ for $ D ^0 D ^0 $ pairs and the projections on (middle) $m_1$ and (right) $m_2$ with the fit results superimposed. Shown in the projection plots are (points with error bars) $\mathrm{Pb}p$ data, (solid blue) the total fit and the four fit components.	Fig4a.pdf [16 KiB] HiDef png [260 KiB] Thumbnail [292 KiB] *.C file
	Fig4b.pdf [32 KiB] HiDef png [249 KiB] Thumbnail [181 KiB] *.C file
(Left) Two-dimensional invariant-mass distributions of $(m_1, m_2)$ for $ D ^0 \overline{ D } {}^0 $ pairs and the projections on (middle) $m_1$ and (right) $m_2$ with the fit results superimposed. Shown in the projection plots are (points with error bars) data data, (solid blue) the total fit and the four fit components. The plots in the top (bottom) row correspond to $ p\mathrm{Pb}$ ( $\mathrm{Pb}p$ ) data.	Fig5a.pdf [16 KiB] HiDef png [240 KiB] Thumbnail [270 KiB] *.C file
	Fig5b.pdf [32 KiB] HiDef png [223 KiB] Thumbnail [172 KiB] *.C file
	Fig5c.pdf [16 KiB] HiDef png [264 KiB] Thumbnail [304 KiB] *.C file
	Fig5d.pdf [33 KiB] HiDef png [234 KiB] Thumbnail [177 KiB] *.C file
(Left) Two-dimensional invariant-mass distributions of $(m_1^ { J \mskip -3mu/\mskip -2mu\psi } , m_2^ D ^0 )$ for $ { J \mskip -3mu/\mskip -2mu\psi } D ^0 $ pairs and the projections on (middle) $m_1^ { J \mskip -3mu/\mskip -2mu\psi } $ and (right) $m_2^ D ^0 $ with the fit results superimposed. Shown in the projection plots are (points with error bars) data data, (solid blue) the total fit and the four fit components. The plots in the top (bottom) row correspond to $ p\mathrm{Pb}$ ( $\mathrm{Pb}p$ ) data.	Fig6a.pdf [19 KiB] HiDef png [380 KiB] Thumbnail [424 KiB] *.C file
	Fig6b.pdf [33 KiB] HiDef png [269 KiB] Thumbnail [208 KiB] *.C file
	Fig6c.pdf [22 KiB] HiDef png [402 KiB] Thumbnail [397 KiB] *.C file
	Fig6d.pdf [33 KiB] HiDef png [287 KiB] Thumbnail [218 KiB] *.C file
Ratios of differential cross-sections in bins of charm hadron rapidity under the $ p_{\mathrm{T}} ( D )>2\text{ Ge V /}c $ requirement. The average over all the pairs listed in Table 5 for each rapidity interval is also presented. The boxes (bars) correspond to systematic (statistical) uncertainties. Points are shifted horizontally to improve visibility.	Fig7.pdf [15 KiB] HiDef png [190 KiB] Thumbnail [143 KiB] *.C file
Animated gif made out of all figures.	PAPER-2020-010.gif Thumbnail

Tables and captions

The effective cross-section $\sigma_{\mathrm{eff}, p\mathrm{Pb}}$ (in $\text{ b} $) measured using $ { J \mskip -3mu/\mskip -2mu\psi } D ^0 $ and $ D ^0 D ^0 $ pair production in $p$-Pb data and the extrapolated values from $pp$ data [80].	Table_1.pdf [60 KiB] HiDef png [35 KiB] Thumbnail [16 KiB] tex code
Total cross-sections of charm pair production (in $\text{ mb}$ ) in $ p\mathrm{Pb}$ and $\mathrm{Pb}p$ data for the $ p_{\mathrm{T}} $ requirement on the charm hadron, $ p_{\mathrm{T}} >0\text{ Ge V /}c $ for $ { J \mskip -3mu/\mskip -2mu\psi } , D ^0 $ and $ p_{\mathrm{T}} >2\text{ Ge V /}c $ for $ D ^+ , D ^+_ s $. The rapidity range is for each charm hadron in the pair. The first uncertainty is statistical and the second is systematic. The prediction of SPS $ { J \mskip -3mu/\mskip -2mu\psi } D ^0 $ production calculated using the weighted EPPS16 nuclear PDF [92,93,94,95] is also listed for comparison, where the first uncertainty is from uncertainties of scales, feed-down contribution and model parameters, and the second due to nuclear PDF uncertainties.	Table_2.pdf [70 KiB] HiDef png [123 KiB] Thumbnail [59 KiB] tex code
Total production cross-sections (in $\text{ mb}$ ) of open charm pairs involving the $ D ^0 $ meson in $ p\mathrm{Pb}$ and $\mathrm{Pb}p$ data with the $ p_{\mathrm{T}} ( D ^0 )>2\text{ Ge V /}c $ requirement. The rapidity range is for each charm hadron in the pair. The first uncertainty is statistical and the second is systematic. Predictions for the $ D ^0 D ^0 $ and $ D ^0 \overline{ D } {}^0 $ cross-sections from Ref. [24] are given in the last two rows of the Table.	Table_3.pdf [69 KiB] HiDef png [124 KiB] Thumbnail [65 KiB] tex code
Total cross-sections (in $\text{ mb}$ ) in $ p\mathrm{Pb}$ and $\mathrm{Pb}p$ data for full rapidity acceptance without any $ p_{\mathrm{T}} (H_c)$ requirement. The first uncertainty is statistical and the second is systematic.	Table_4.pdf [59 KiB] HiDef png [57 KiB] Thumbnail [29 KiB] tex code
Ratios of differential cross-sections in bins of charm hadron rapidity for charm $ p_{\mathrm{T}} (H_c)>2\text{ Ge V /}c $. The average over all the pairs in each rapidity interval is also presented.	Table_5.pdf [67 KiB] HiDef png [79 KiB] Thumbnail [34 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [275 KiB]
This ZIP file contains supplementary material for the publication LHCb-PAPER-2020-010. The files are: Supplementary.pdf : An overview of the extra figures .pdf, .png, *.eps : The figures in various formats	FigS1a.pdf [15 KiB] HiDef png [158 KiB] Thumbnail [139 KiB] *C file
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