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Measurements of prompt charm production cross-sections in $pp$ collisions at $\sqrt{s}$ = 13 TeV

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Abstract

Production cross-sections of prompt charm mesons are measured with the first data from $pp$ collisions at the LHC at a centre-of-mass energy of $13\,\mathrm{TeV}$. The data sample corresponds to an integrated luminosity of $4.98 \pm 0.19\,\mathrm{pb}^{-1}$ collected by the LHCb experiment. The production cross-sections of $D^{0}$, $D^{+}$, $D_{s}^{+}$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{\mathrm{T}}$, and rapidity, $y$, and cover the range $0 < p_{\mathrm{T}} < 15\,\mathrm{GeV}/c$ and $2.0 < y < 4.5$. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of $1 < p_{\mathrm{T}} < 8\,\mathrm{GeV}/c$ are found to be \begin{equation} \sigma(pp \to D^{0} X) = 2072 \pm 2 \pm 124\,\mu\mathrm{b}\\ \sigma(pp \to D^{+} X) = 834 \pm 2 \pm \phantom{1}78\,\mu\mathrm{b}\\ \sigma(pp \to D_{s}^{+} X) = 353 \pm 9 \pm \phantom{1}76\,\mu\mathrm{b}\\ \sigma(pp \to D^{*+} X) = 784 \pm 4 \pm \phantom{1}87\,\mu\mathrm{b} \end{equation} where the uncertainties are due to statistical and systematic uncertainties, respectively.

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Distributions for selected $ D^{0} \to K^{-} \pi^{+} $ candidates: (left) $ K^{-} \pi^{+} $ invariant mass and (right) $\ln{\chi^2_{\rm IP}}$ for a mass window of $\pm\SI{20}{\mevcc}$ around the nominal $ D^{0}$ mass. The sum of the simultaneous likelihood fits in each $ ( p_{\mathrm{T}} , y )$ bin is shown, with components as indicated in the legends.

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Distributions for selected $ D^{+} \to K^{-} \pi^{+} \pi^{+} $ candidates: (left) $ K^{-} \pi^{+} \pi^{+} $ invariant mass and (right) $\ln{\chi^2_{\rm IP}}$ for a mass window of $\pm\SI{20}{\mevcc}$ around the nominal $ D^{+}$ mass. The sum of the simultaneous likelihood fits in each $ ( p_{\mathrm{T}} , y )$ bin is shown, with components as indicated in the legends.

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Distributions for selected $ D_{ s }^{+} \to ( K^{-} K^{+} )_{\phi}\pi^{+} $ candidates: (left) $ K^{+} K^{-} \pi^{+} $ invariant mass and (right) $\ln{\chi^2_{\rm IP}}$ for a mass window of $\pm\SI{20}{\mevcc}$ around the nominal $ D_{ s }^{+}$ mass. The sum of the simultaneous likelihood fits in each $ ( p_{\mathrm{T}} , y )$ bin is shown, with components as indicated in the legends.

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Distributions for selected $ D^{*+} \to D^{0} \pi^{+} $ candidates, with $ D^{0} \to K^{-} \pi^{+} $ : (left) $\Delta{m} = m( D^{*+} ) - m( D^{0} )$ for a mass window of $\pm\SI{20}{\mevcc}$ around the nominal $ D^{0}$ mass and (right) $\ln{\chi^2_{\rm IP}}$ with an additional mass window of $\pm\SI{3}{\mevcc}$ around the nominal $ D^{*+}$ {}- $ D^{0}$ mass difference. The sum of the simultaneous likelihood fits in each $ ( p_{\mathrm{T}} , y )$ bin is shown, with components as indicated in the legends.

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Measurements and predictions for the absolute prompt (top) $ D^{0}$ , and (bottom) $ D^{+}$ cross-sections at $\sqrt{s} = \SI{13}{\TeV}$ . Each set of measurements and predictions in a given rapidity bin is offset by a multiplicative factor $10^{-m}$, where the factor $m$ is shown on the plots. The boxes indicate the $\pm1\sigma$ uncertainty band on the theory predictions. In cases where this band spans more than two orders of magnitude only its upper edge is indicated.

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Measurements and predictions for the absolute prompt (top) $ D_{ s }^{+}$ , and (bottom) $ D^{*+}$ cross-sections at $\sqrt{s} = \SI{13}{\TeV}$ . Each set of measurements and predictions in a given rapidity bin is offset by a multiplicative factor $10^{-m}$, where the factor $m$ is shown on the plots. The boxes indicate the $\pm1\sigma$ uncertainty band on the theory predictions. In cases where this band spans more than two orders of magnitude only its upper edge is indicated.

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Measurements and predictions of the prompt $ D^{0}$ , $ D^{+}$ , $ D_{ s }^{+}$ , and $ D^{*+}$ cross-section ratios. The dash-dotted lines indicate the unit ratio for each of the rapidity intervals and the dashed lines indicate a ratio of two. Each set of measurements and predictions in a given rapidity bin is offset by an additive constant $m$, which is shown on the plot. No prediction is available for the $ D_{ s }^{+}$ ratio.

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Ratios of cross-section-times-branching-fraction measurements of (top) $ D^{+}$ , (middle) $ D_{ s }^{+}$ , and (bottom) $ D^{*+}$ mesons with respect to the $ D^{0}$ measurements. The bands indicate the corresponding ratios computed using measurements from $ e^{+} e^{-} $ collider experiments [40,41,42]. The ratios are given as a function of $ p_{\mathrm{T}}$ and different symbols indicate different ranges in $ y$ . The notation $\sigma( D \to f )$ is shorthand for $\sigma(D)\times\mathcal{B} ( D \to f )$ .

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Integrated cross-sections (black diamonds), their average (black circle and blue band) and theory predictions (red squares) [1,2] are shown (left) based on the $ D^{0}$ and $ D^{+}$ for $0 < p_{\mathrm{T}} < \SI{8}{\gevc}$ and (right) for measurements based on all four mesons for $1 < p_{\mathrm{T}} < \SI{8}{\gevc}$. The "absolute" predictions are based on calculations of the \SI{13}{\TeV} cross-section, while the "scaled" predictions are based on calculations of the $13$ to \SI{7}{\TeV} ratio multiplied with the LHCb measurement at \SI{7}{\TeV} [16].

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Ratios of cross-section-times-branching-fraction measurements of (top) $ D^{*+}$ , and (middle) $ D_{ s }^{+}$ mesons with respect to $ D^{+}$ cross-sections, and (bottom) $ D_{ s }^{+}$ over $ D^{*+}$ mesons. The bands indicate the corresponding ratios computed using measurements from $ e^{+} e^{-} $ collider experiments [40,41,42]. The ratios are given as a function of $ p_{\mathrm{T}}$ and different symbols indicate different ranges in $ y$ . The notation $\sigma( D \to f )$ is shorthand for $\sigma(D)\times\mathcal{B} ( D \to f )$ .

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Tables and captions

Prompt signal yields in the fully selected dataset, summed over all ( $ p_{\mathrm{T}}$ , $ y$ ) bins in which a measurement is made.

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Systematic uncertainties expressed as 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. Ranges for the correlations between $ p_{\mathrm{T}}$ - $ y$ bins and between modes are also given, expressed in percent.

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Prompt charm production cross-sections in the kinematic ranges given. The computation of the extrapolation factors is described in the text. The first uncertainty on the cross-section is statistical, and the second is systematic and includes the contribution from the extrapolation factor. No extrapolation factor is given for $ D^{+} _{( s )}$ as a measurement is available in every bin of the integrated phase space.

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Ratios of integrated cross-section-times-branching-fraction measurements in the kinematic range $1 < p_{\mathrm{T}} < \SI{8}{\gevc}$ and $2 < y < 4.5$. The first uncertainty on the ratio is statistical and the second is systematic. The notation $\sigma( D \to f )$ is shorthand for $\sigma(D)\times\mathcal{B} ( D \to f )$ .

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Supplementary Material [file]

Supplementary material full pdf

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This ZIP file contains supplemetary material for the publication LHCb-PAPER-2014-041. The files are: supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.jpg, *.eps : The figures in various formats

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Created on 11 December 2018.Citation count from INSPIRE on 18 December 2018.