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] HiDef png [434 KiB] Thumbnail [102 KiB] *.C file
	mass_Ap.pdf [28 KiB] HiDef png [707 KiB] Thumbnail [139 KiB] *.C file
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.	ipchi2_pA.pdf [23 KiB] HiDef png [379 KiB] Thumbnail [103 KiB] *.C file
	ipchi2_Ap.pdf [23 KiB] HiDef png [471 KiB] Thumbnail [117 KiB] *.C file
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.	cpt0.pdf [19 KiB] HiDef png [198 KiB] Thumbnail [70 KiB] *.C file
	cpt1.pdf [18 KiB] HiDef png [193 KiB] Thumbnail [69 KiB] *.C file
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.	cpt2.pdf [17 KiB] HiDef png [195 KiB] Thumbnail [76 KiB] *.C file
	cy.pdf [14 KiB] HiDef png [131 KiB] Thumbnail [52 KiB] *.C file
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.	rfb_pt.pdf [16 KiB] HiDef png [728 KiB] Thumbnail [114 KiB] *.C file
	rfb_y.pdf [15 KiB] HiDef png [595 KiB] Thumbnail [98 KiB] *.C file
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] HiDef png [322 KiB] Thumbnail [100 KiB] *.C file
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.	lc2d0_y.pdf [19 KiB] HiDef png [178 KiB] Thumbnail [49 KiB] *.C file
Animated gif made out of all figures.	CONF-2017-005.gif Thumbnail

Tables and captions

Summary of systematic and statistic uncertainties for differential cross-sections. The ranges indicate the variations between bins.	Table_1.pdf [67 KiB] HiDef png [121 KiB] Thumbnail [19 KiB] tex code
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] HiDef png [158 KiB] Thumbnail [26 KiB] tex code
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] HiDef png [189 KiB] Thumbnail [33 KiB] tex code
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] HiDef png [170 KiB] Thumbnail [29 KiB] tex code
$ 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] HiDef png [82 KiB] Thumbnail [14 KiB] tex code
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] HiDef png [261 KiB] Thumbnail [45 KiB] tex code
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] HiDef png [196 KiB] Thumbnail [33 KiB] tex code
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] HiDef png [158 KiB] Thumbnail [26 KiB] tex code
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] HiDef png [189 KiB] Thumbnail [33 KiB] tex code
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] HiDef png [170 KiB] Thumbnail [29 KiB] tex code
$ 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] HiDef png [82 KiB] Thumbnail [14 KiB] tex code
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] HiDef png [261 KiB] Thumbnail [45 KiB] tex code
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] HiDef png [196 KiB] Thumbnail [33 KiB] tex code