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Measurement of $D_s^{\pm}$ production asymmetry in $pp$ collisions at $\sqrt{s} =7$ and 8 TeV

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Abstract

The inclusive $D_s^{\pm}$ production asymmetry is measured in $pp$ collisions collected by the LHCb experiment at centre-of-mass energies of $\sqrt{s} =7$ and 8 TeV. Promptly produced $D_s^{\pm}$ mesons are used, which decay as $D_s^{\pm}\to\phi\pi^{\pm}$, with $\phi\to K^+K^-$. The measurement is performed in bins of transverse momentum, $p_{\rm T}$, and rapidity, $y$, covering the range $2.5<p_{\rm T}<25.0$ GeV$/c$ and $2.0<y<4.5$. No kinematic dependence is observed. Evidence of nonzero $D_s^{\pm}$ production asymmetry is found with a significance of 3.3 standard deviations.

Figures and captions

Distribution of $ D ^+_ s $ candidates for the $\sqrt{s} =7$ and 8 TeV data sets as a function of $p_{\mathrm{ T}}$ and $ y$ . The binning scheme used for the $ A_{\rm P}( D ^+_ s )$ measurement is overlaid.

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Invariant mass distribution of the $ D ^+_ s $ candidates in the kinematic range (left) $2.0<y<3.0$ and $2.5< p_{\mathrm{ T}} <4.7 {\mathrm{ Ge V /}c} $, and (right) $3.5<y<4.5$ and $8.5< p_{\mathrm{ T}} <25.0 {\mathrm{ Ge V /}c} $ for the $\sqrt{s} =8$ TeV data set recorded with MagDown . Also shown is the result of the fit, indicating the signal and combinatorial background.

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Results of the LHCb measurement of the $ D ^+_ s $ production asymmetry as a function of $p_{\mathrm{ T}}$ for three different bins of rapidity, compared to the results from Pythia . Both are for the combined $\sqrt{s} =7$ and 8 TeV data sets. The uncertainties on the Pythia predictions are statistical only.

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Results of the LHCb measurement of the $ D ^+_ s $ production asymmetry as a function of $p_{\mathrm{ T}}$ for three different bins of rapidity for the (left) $\sqrt{s} =7\mathrm{ Te V} $ and (right) $8\mathrm{ Te V} $ data sets, split between the magnet polarities Mag Up and MagDown .

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Results of the LHCb measurement of the $ D ^+_ s $ production asymmetry as a function of $p_{\mathrm{ T}}$ for three different bins of rapidity for the (left) $\sqrt{s} =7\mathrm{ Te V} $ and (right) $8\mathrm{ Te V} $ data sets, compared to the results from Pythia . The uncertainties of the Pythia prediction are statistical only.

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Tables and captions

Raw and detection asymmetries in percent, for the 7 and 8 TeV data sets. The detection asymmetries are determined on the data combined from all kinematic bins. The first uncertainty is statistical, the second systematic.

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Values of the $ D ^+_ s $ production asymmetry in percent, including, respectively, the statistical and systematic uncertainties for each of the $ D ^+_ s $ kinematic bins using the combined $\sqrt{s} =7$ and $8\mathrm{ Te V} $ data sets. The statistical and systematic uncertainties include the corresponding contributions from the detection asymmetries, and are therefore correlated between the bins.

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Values of the $ D ^+_ s $ production asymmetry in percent, including, respectively, the statistical and systematic uncertainty for each of the $ D ^+_ s $ kinematic bins using the $\sqrt{s} =7\mathrm{ Te V} $ data set.

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Values of the $ D ^+_ s $ production asymmetry in percent, including, respectively, the statistical and systematic uncertainty for each of the $ D ^+_ s $ kinematic bins using the $\sqrt{s} =8\mathrm{ Te V} $ data set.

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Supplementary Material [file]

Supplementary material full pdf

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This ZIP file contains supplementary material for the publication LHCb-PAPER-2018-010. The files are: supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.eps, *.C : The figures in various formats

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Created on 11 July 2020.