A study of prompt charmhadron pair production in protonlead 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 crosssections 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 protonlead collisions. The results confirm the predicted enhancement of double parton scattering production in protonlead collisions compared to the single parton scattering production.
(Left) Twodimensional invariantmass 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 

Twocharm hadron invariantmass 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) Twodimensional invariantmass 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) Twodimensional invariantmass 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) Twodimensional invariantmass 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 crosssections 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. 
PAPER2020010.gif Thumbnail 
The effective crosssection $\sigma_{\mathrm{eff}, p\mathrm{Pb}}$ (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 crosssections 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, feeddown 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 crosssections (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 $ crosssections 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 crosssections (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 crosssections 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 full pdf 
supple[..].pdf [275 KiB] 

This ZIP file contains supplementary material for the publication LHCbPAPER2020010. 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 

FigS1b.pdf [15 KiB] HiDef png [165 KiB] Thumbnail [145 KiB] *C file 

FigS2.pdf [16 KiB] HiDef png [184 KiB] Thumbnail [162 KiB] *C file 

FigS3a.pdf [15 KiB] HiDef png [220 KiB] Thumbnail [170 KiB] *C file 

FigS3b.pdf [14 KiB] HiDef png [215 KiB] Thumbnail [169 KiB] *C file 

FigS4a.pdf [15 KiB] HiDef png [213 KiB] Thumbnail [164 KiB] *C file 

FigS4b.pdf [15 KiB] HiDef png [213 KiB] Thumbnail [163 KiB] *C file 

FigS5a.pdf [14 KiB] HiDef png [176 KiB] Thumbnail [133 KiB] *C file 

FigS5b.pdf [15 KiB] HiDef png [204 KiB] Thumbnail [159 KiB] *C file 

FigS6.pdf [15 KiB] HiDef png [201 KiB] Thumbnail [180 KiB] *C file 
Created on 20 February 2021.