# Prompt charm production in $pp$ collisions at $\sqrt{s}$ = 7 TeV

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## Abstract

Charm production at the LHC in pp collisions at sqrt(s)=7 TeV is studied with the LHCb detector. The decays D0 -> K- pi+, D+ -> K- pi+ pi+, D*+ -> D0(K- pi+) pi+, D_s+ -> phi(K- K+) pi+, Lambda_c+ -> p K- pi+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb^{-1}. Differential cross-sections dsigma/dp_T are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0 < p_T < 8 GeV/c and 2.0 < y < 4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above p_T-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives sigma(c\bar{c})_{p_T < 8 GeV/c, 2.0 < y < 4.5} = 1419 +/- 12 (stat) +/- 116 (syst) +/- 65 (frag) microbarn, where the uncertainties are statistical, systematic, and due to the fragmentation functions.

## Figures and captions

 Mass and $\log_{10}(\mathrm{IP} \chi^2 )$ distributions for selected $D ^0 \rightarrow K ^- \pi ^+$ and $D ^+ \rightarrow K ^- \pi ^+ \pi ^+$ candidates showing \subref{fig:Dz:m:m} the masses of the $D ^0$ candidates, \subref{fig:Dz:m:ip} the $\log_{10}(\mathrm{IP} \chi^2 )$ distribution of $D ^0$ candidates for a mass window of $\pm 16 {\mathrm{ Me V /}c^2}$ (approximately $\pm 2\sigma$) around the fitted $m( K ^- \pi ^+ )$ peak, \subref{fig:Dp:m:m} the masses of the $D ^+$ candidates, and \subref{fig:Dp:m:ip} the $\log_{10}(\mathrm{IP} \chi^2 )$ distribution of $D ^+$ candidates for a mass window of $\pm 11 {\mathrm{ Me V /}c^2}$ (approximately $\pm 2\sigma$) around the fitted $m( K ^- \pi ^+ \pi ^+ )$ peak. Projections of likelihood fits to the full data samples are shown with components as indicated in the legends. \label{fig:Dp:m} Figure[..].pdf [21 KiB] HiDef png [189 KiB] Thumbnail [156 KiB] *.C file Figure[..].pdf [22 KiB] HiDef png [157 KiB] Thumbnail [125 KiB] *.C file Figure[..].pdf [21 KiB] HiDef png [187 KiB] Thumbnail [154 KiB] *.C file Figure[..].pdf [30 KiB] HiDef png [132 KiB] Thumbnail [109 KiB] *.C file Mass and $\log_{10}(\mathrm{IP} \chi^2 )$ distributions for selected $D ^{*+} \rightarrow D ^0 ( K ^- \pi ^+ ) \pi ^+$ candidates showing \subref{fig:Dstarp:m:mkpi} the masses of the $D ^0$ candidates for a window of $\pm 1.6 {\mathrm{ Me V /}c^2}$ (approximately $\pm 2\sigma$) around the fitted $\Delta m$ peak, \subref{fig:Dstarp:m:delm} the differences between the $D ^{*+}$ and $D ^0$ candidate masses for a mass window of $\pm 16 {\mathrm{ Me V /}c^2}$ (approximately $\pm 2\sigma$) around the fitted $m( K ^- \pi ^+ )$ peak, and \subref{fig:Dstarp:m:ip} the $\log_{10}(\mathrm{IP} \chi^2 )$ distribution of the $D ^0$ candidate for a mass signal box of $\pm 16 {\mathrm{ Me V /}c^2}$ around the fitted $m( K ^- \pi ^+ )$ peak and $\pm 1.6 {\mathrm{ Me V /}c^2}$ around the fitted $\Delta m$ peak. Projections of a likelihood fit to the full data sample are shown with components as indicated in the legend. The ` $D ^0$ backgrounds' component is the sum of the secondary, prompt random slow pion, and secondary random slow pion backgrounds. Figure[..].pdf [21 KiB] HiDef png [217 KiB] Thumbnail [172 KiB] *.C file Figure[..].pdf [22 KiB] HiDef png [228 KiB] Thumbnail [163 KiB] *.C file Figure[..].pdf [21 KiB] HiDef png [184 KiB] Thumbnail [147 KiB] *.C file Mass and $\log_{10}(\mathrm{IP} \chi^2 )$ distributions for selected $D ^+_ s \rightarrow \phi ( K ^- K ^+ ) \pi ^+$ and $\Lambda _ c ^+ \rightarrow p K ^- \pi ^+$ candidates showing \subref{fig:Ds:m:m} the masses of the $D ^+_ s$ candidates, \subref{fig:Ds:m:ip} the $\log_{10}(\mathrm{IP} \chi^2 )$ distribution of $D ^+_ s$ candidates for a mass window of $\pm 8 {\mathrm{ Me V /}c^2}$ (approximately $\pm 2\sigma$) around the fitted $m(\phi ( K ^- K ^+ )\pi ^+ )$ peak, \subref{fig:Lcp:m:m} the masses of the $\Lambda _ c ^+$ candidates, and \subref{fig:Lcp:m:ip} the $\log_{10}(\mathrm{IP} \chi^2 )$ distribution of $\Lambda _ c ^+$ candidates for a mass window of $\pm 12 {\mathrm{ Me V /}c^2}$ (approximately $\pm 2\sigma$) around the fitted $m( p K ^- \pi ^+ )$ peak. Projections of likelihood fits to the full data samples are shown with components as indicated in the legends. \label{fig:Lcp:m} Figure[..].pdf [21 KiB] HiDef png [212 KiB] Thumbnail [179 KiB] *.C file Figure[..].pdf [29 KiB] HiDef png [161 KiB] Thumbnail [128 KiB] *.C file Figure[..].pdf [20 KiB] HiDef png [211 KiB] Thumbnail [178 KiB] *.C file Figure[..].pdf [28 KiB] HiDef png [149 KiB] Thumbnail [126 KiB] *.C file Differential cross-sections for \subref{fig:lhcb:Dz:a} $D ^0$ , \subref{fig:lhcb:Dp:b} $D ^+$ , \subref{fig:lhcb:dstar:a} $D ^{*+}$ , and \subref{fig:lhcb:Dsp:b} $D ^+_ s$ meson production compared to theoretical predictions. The cross-sections for different $y$ regions are shown as functions of $p_{\rm T}$ . The $y$ ranges are shown as separate curves and associated sets of points scaled by factors $10^{-m}$, where the exponent $m$ is shown on the plot with the $y$ range. The error bars associated with the data points show the sum in quadrature of the statistical and total systematic uncertainty. The shaded regions show the range of theoretical uncertainties for the GMVFNS prediction. \label{fig:lhcb:Dp} \label{fig:lhcb:dstar} \label{fig:lhcb:Dsp} Figure[..].pdf [29 KiB] HiDef png [681 KiB] Thumbnail [471 KiB] *.C file Figure[..].pdf [27 KiB] HiDef png [604 KiB] Thumbnail [449 KiB] *.C file Figure[..].pdf [26 KiB] HiDef png [594 KiB] Thumbnail [439 KiB] *.C file Figure[..].pdf [27 KiB] HiDef png [597 KiB] Thumbnail [451 KiB] *.C file Differential cross-sections for $\Lambda _ c ^+$ baryon production compared to the theoretical prediction from the GMVFNS scheme. The error bars associated with the data points show the sum in quadrature of the statistical and total systematic uncertainty. The shaded region shows the range of theoretical uncertainty for the theoretical prediction. Figure[..].pdf [14 KiB] HiDef png [198 KiB] Thumbnail [170 KiB] *.C file Animated gif made out of all figures. PAPER-2012-041.gif Thumbnail

## Tables and captions

 Overview of systematic uncertainties and their values, expressed as relative fractions of the cross-section measurements in percent (%). Uncertainties that are computed bin-by-bin are expressed as ranges giving the minimum to maximum values of the bin uncertainties. The correlated and uncorrelated uncertainties are shown as discussed in the text. Table_1.pdf [47 KiB] HiDef png [79 KiB] Thumbnail [38 KiB] tex code Open charm production cross-sections in the kinematic range $0 < p_{\rm T} < 8 {\mathrm{ Ge V /}c}$ and $2.0 < y < 4.5$ . The computation of the extrapolation factors is described in the text. The first uncertainty is statistical, the second is systematic, and the third is the contribution from the extrapolation factor. Table_2.pdf [53 KiB] HiDef png [77 KiB] Thumbnail [40 KiB] tex code Correlation matrix of the uncertainties of the integrated open charm production cross-sections in the kinematic range $0 < p_{\rm T} < 8 {\mathrm{ Ge V /}c}$ and $2.0 < y < 4.5$ . The first column restates measured values of the integrated cross-sections . Table_3.pdf [51 KiB] HiDef png [55 KiB] Thumbnail [30 KiB] tex code Cross-section ratios for open charm production in the kinematic range $0 < p_{\rm T} < 8 {\mathrm{ Ge V /}c}$ and $2.0 < y < 4.5$ . The numbers in the table are the ratios of the respective row/column. Table_4.pdf [47 KiB] HiDef png [51 KiB] Thumbnail [26 KiB] tex code Bin-integrated production cross-sections in ${\rm \upmu b}$ for prompt $\Lambda _ c ^+$ $+$ c.c. baryons in bins of $y$ integrated over the range $2 < p_{\rm T} < 8 {\mathrm{ Ge V /}c}$. The first uncertainty is statistical, and the second is the total systematic. Table_5.pdf [34 KiB] HiDef png [26 KiB] Thumbnail [14 KiB] tex code Differential production cross-sections , $\mathrm{d}\hspace{-0.1em}\sigma/\mathrm{d} p_{\rm T}$ , in ${\rm \upmu b} /( {\mathrm{Ge V /}c} )$ for prompt $\Lambda _ c ^+$ $+$ c.c. baryons in bins of $p_{\rm T}$ integrated over the rapidity range $2.0 < y < 4.5$ . The first uncertainty is statistical, and the second is the total systematic. Table_6.pdf [35 KiB] HiDef png [140 KiB] Thumbnail [60 KiB] tex code

## Supplementary Material [file]

 This ZIP file contains supplemetary material for the publication LHCb-PAPER-2012-041. The files are: LHCb-PAPER-2012-041-Supplementary.pdf : Description of and results from cross-check analyses. Table_*_XSec.hepdata.txt : Flat text files of the tables of differential cross-sections in LHCb-PAPER-2012-041. These are formatted to ease importing the measurements into the Reactions Database of the Durham HepData Project. LHCb-P[..].pdf [153 KiB] HiDef png [330 KiB] Thumbnail [147 KiB] *C file

Created on 17 August 2019.Citation count from INSPIRE on 23 August 2019.