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Prompt $\Lambda^+_c$ production in $p\mathrm{Pb}$ collisions at $\sqrt{s_{NN}} = 5.02$ TeV

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Abstract

The production of $\Lambda^+_c$ baryons produced directly at the interacting point is studied in proton-lead collisions collected with the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of $1.58\mathrm{nb}^{-1}$ recorded at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{NN}}=5.02$ TeV. Measurements of the differential cross-section and the forward-backward production ratio are reported for $\Lambda^+_c$ baryons with transverse momenta in the range $2<p_{T}<10$GeV/$c$ and rapidities in the ranges $1.5<y^*<4.0$ and $-4.5<y^*<-2.5$ in the nucleon-nucleon centre-of-mass system. The ratio of cross-sections of $\Lambda^+_c$ baryons and $D^0$ mesons is also reported. The results are compared with next-to-leading order calculations that use nuclear parton distribution functions.

Figures and captions

Distributions of the invariant mass, $m( p K ^- \pi ^+ )$, in the range $2< p_{\mathrm{ T}} <10 {\mathrm{ Ge V /}c} $ for (a) the forward data sample with $1.5<y^*<4.0$ and (b) the backward data sample with $-4.5<y^*<-2.5$. The red dotted line is the inclusive $\Lambda ^+_ c $ candidates, the grey shaded area is the combinatorial background and the blue solid line is the sum of the two.

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Distributions of $\log_{10}\chi^2_{\text{IP}} (\Lambda ^+_ c ) $ in the range $2< p_{\mathrm{ T}} <10 {\mathrm{ Ge V /}c} $ with the fit results overlaid for (a) the forward data sample with $1.5<y^*<4.0$, and (b) the backward data sample with $-4.5<y^*<-2.5$. The solid blue curve is the sum. The red dotted line is the prompt component, the green is the $\Lambda ^+_ c \mathrm{\text{-}from\text{-}} b $ component and the grey shaded area denotes the combinatorial background.

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Double-differential cross-section of prompt $\Lambda ^+_ c $ baryons in $ p\mathrm{Pb} $ collisions in the (a) forward and (b) backward collision samples. The uncertainty represents the quadratic sum of the statistical and the systematic uncertainties.

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Differential cross-section of prompt $\Lambda ^+_ c $ baryons in $ p\mathrm{Pb} $ collisions as a function of (a) $ p_{\mathrm{ T}} $ and (b) $y^{*}$ in the forward and backward samples. The forward and backward differential cross-sections $\mathrm{d}\sigma/\mathrm{d} p_{\mathrm{ T}} $ in the common rapidity region $2.5<|y^*|<4.0$ are scaled by 0.1 to improve the visibility. The box on each point represents the systematic uncertainty and the error bar represents the sum in quadrature of the statistical and the systematic uncertainties.

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(a) Forward-backward production ratios $R_\mathrm{FB}$ as a function of $ p_{\mathrm{ T}} $ integrated over $2.5<|y^*|<4.0$ for $ p_{\mathrm{ T}} $ less than $7 {\mathrm{ Ge V /}c} $ and $2.5<|y^*|<3.5$ for $ p_{\mathrm{ T}} $ greater than $7 {\mathrm{ Ge V /}c} $, and (b) $R_\mathrm{FB}$ as a function of $y^*$ integrated over $2< p_{\mathrm{ T}} <10 {\mathrm{ Ge V /}c} $. The box on each point represents the systematic uncertainty and the error bar represents the sum in quadrature of the statistical and the systematic uncertainties.

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The cross-section ratio $ R_{\Lambda ^+_ c / D ^0 }$ between $\Lambda ^+_ c $ baryons and $ D ^0$ mesons as a function of $ p_{\mathrm{ T}} $ integrated over four different rapidity regions. The box on each point represents the systematic uncertainty and the error bar represents the sum in quadrature of the statistical and the systematic uncertainties. The coloured curves represent HELAC-Onia calculations with nPDF EPS09LO/NLO and nCTEQ15.

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The cross-section ratio $ R_{\Lambda ^+_ c / D ^0 }$ between $\Lambda ^+_ c $ baryons and $ D ^0$ mesons as a function of $y^*$ integrated over $2< p_{\mathrm{ T}} <10 {\mathrm{ Ge V /}c} $. The box on each point represents the systematic uncertainty and the error bar represents the sum in quadrature of the statistical and the systematic uncertainties. The coloured curves show HELAC-Onia calculations incorporating nPDFs EPS09LO/NLO and nCTEQ15. The open circle is the value measured by the ALICE collaboration [21]. The error bar shows the total uncertainty and the grey square the systematic.

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Tables and captions

Systematic and statistical uncertainties for the differential cross-sections. The ranges indicate the variation over the ($ p_{\mathrm{ T}} , y^*$) bins.

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Measured differential cross-section (in $\mathrm{ mb} /( {\mathrm{ Ge V /}c} )$) of prompt $\Lambda ^+_ c $ baryons as a function of $ p_{\mathrm{ T}} $ in $ p\mathrm{Pb} $ forward and backward data in different rapidity regions. The right column shows the results for $ p_{\mathrm{ T}} > 7 {\mathrm{ Ge V /}c} $ and $2.5<|y^*|<3.5$, which are used to compute the $ R_\mathrm{FB} $ values at $ p_{\mathrm{ T}} > 7 {\mathrm{ Ge V /}c} $. The first uncertainties are statistical and the second are systematic.

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Differential cross-section (in $\mathrm{ mb} $) for prompt $\Lambda ^+_ c $ baryons as a function of $|y^{*}|$ in $ p\mathrm{Pb} $ forward and backward data. The first uncertainties are statistical and the second are systematic.

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Forward-backward prompt $\Lambda ^+_ c $ production ratio $ R_\mathrm{FB} $ as a function of $ p_{\mathrm{ T}} $ in the common range $2.5<|y^*|<4.0$. The first uncertainty is statistical and the second is systematic.

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$ R_\mathrm{FB} $ ratio as a function of $|y^*|$ in the range $2< p_{\mathrm{ T}} <10 {\mathrm{ Ge V /}c} $. The first uncertainty is statistical and the second is systematic.

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Production ratio $ R_{\Lambda ^+_ c / D ^0 } $ as a function of $ p_{\mathrm{ T}} $ in the forward and backward rapidity regions. The first uncertainty is statistical and the second is systematic.

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Production ratio $ R_{\Lambda ^+_ c / D ^0 } $ as a function of $y^*$ for $2< p_{\mathrm{ T}} <10 {\mathrm{ Ge V /}c} $. The first uncertainty is statistical and the second is systematic.

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Created on 24 August 2019.Citation count from INSPIRE on 24 August 2019.