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

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Abstract

Production of prompt $\Lambda ^+_ c $ baryons is studied in proton-lead and lead-proton collisions collected with the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of $1.58\pm0.02\,nb^{-1} $ recorded at a nucleon-nucleon centre-of-mass energy of $\sqrt{ s_{ {NN}}}=5.02\mathrm{\,TeV} $. Measurements of the differential cross-section and the forward-backward production ratio are reported using $\Lambda ^+_ c $ candidates with transverse momenta in the range $2-10 {\mathrm{\,GeV\!/}c} $ and rapidities in the ranges of $1.5-4.0$ and $-4.5- -2.5$ 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 theoretical calculations using nuclear parton distribution functions.

Figures and captions

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

mass_pA.pdf [28 KiB]
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mass_Ap.pdf [28 KiB]
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Distributions of $\log_{10}\chi^2_{\text{IP}} (\Lambda ^+_ c ) $ distribution with the fit results overlaid for (a) the forward data sample with $2 < p_{\mathrm{ T}} < 10 {\mathrm{\,GeV\!/}c} $ and $1.5 < y^* < 4.0$, and (b) the backward data sample with $2 < p_{\mathrm{ T}} < 10 {\mathrm{\,GeV\!/}c} $ and $-4.5 < y^* < -2.5$. 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 while the grey shaded area denotes the combinatorial background.

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ipchi2_Ap.pdf [23 KiB]
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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 error bars represent the quadratic sum of the statistical and the systematic uncertainties.

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cpt1.pdf [18 KiB]
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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 sample. The error bars represent the quadratic sum of the statistical and the systematic uncertainties.

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cy.pdf [14 KiB]
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Forward-backward production ratios $R_\mathrm{FB}$ as functions of (a) $ p_{\mathrm{ T}} $ integrated over $2.5<y^*<4$ and (b) $y^*$ integrated over $2< p_{\mathrm{ T}} <10 {\mathrm{\,GeV\!/}c} $. The error bars represent the quadratic sum of the statistical and the systematic uncertainties.

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rfb_y.pdf [15 KiB]
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Production ratio $ R_{\Lambda ^+_ c / D ^0 }$ between $\Lambda ^+_ c $ baryons to $ D ^0$ mesons as a function of $ p_{\mathrm{ T}} $ integrated over four different rapidity regions. The error bars represent the quadratic sum of the statistical and the systematic uncertainties.

lc2d0_pt.pdf [32 KiB]
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Production 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{\,GeV\!/}c} $. The error bars represent the quadratic sum of the statistical and the systematic uncertainties.

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Animated gif made out of all figures.

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Tables and captions

Summary of systematic and statistic uncertainties for differential cross-sections. The ranges indicate the variations between bins.

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Measured differential cross-sections (in units of $\mathrm{ \,mb} /( {\mathrm{\,GeV\!/}c} )$) of prompt $\Lambda ^+_ c $ baryons as functions 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{\,GeV\!/}c} $ and $2.5<|y^*|<3.5$, which are used to compute the $ R_\mathrm{FB} $ values at $ p_{\mathrm{ T}} > 7 {\mathrm{\,GeV\!/}c} $. The first uncertainties are statistical and the second are systematic.

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Differential cross-sections (in units of $\mathrm{ \,mb} $) for prompt $\Lambda ^+_ c $ baryons as functions 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 $|y^*|$ range between 2.5 and 4. The first uncertainty is statistical and the second is systematic.

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

Table_8.pdf [42 KiB]
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Table_8.pdf

Measured differential cross-sections (in units of $\mathrm{ \,mb} /( {\mathrm{\,GeV\!/}c} )$) of prompt $\Lambda ^+_ c $ baryons as functions 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{\,GeV\!/}c} $ and $2.5<|y^*|<3.5$, which are used to compute the $ R_\mathrm{FB} $ values at $ p_{\mathrm{ T}} > 7 {\mathrm{\,GeV\!/}c} $. The first uncertainties are statistical and the second are systematic.

Table_3.pdf [45 KiB]
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Table_3.pdf

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

Table_4.pdf [45 KiB]
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Table_4.pdf

Forward-backward prompt $\Lambda ^+_ c $ production ratio $ R_\mathrm{FB} $ as a function of $ p_{\mathrm{ T}} $ in the common $|y^*|$ range between 2.5 and 4. The first uncertainty is statistical and the second is systematic.

Table_5.pdf [35 KiB]
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Table_5.pdf

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

Table_6.pdf [41 KiB]
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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.

Table_7.pdf [44 KiB]
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Table_7.pdf

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

Table_8.pdf [42 KiB]
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Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.