$\mathrm{Λ_{c}^{+}}$ production in pp and in p-Pb collisions at $\sqrt{s_{\rm {NN}}} = 5.02$ TeV

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The production cross section of prompt $\mathrm{\Lambda_{c}^{+}}$ charmed baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p-Pb) collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_\mathrm{NN}} = 5.02$ TeV. The $\mathrm{\Lambda_{c}^{+}}$ and $\rm {\overline{\Lambda}{}_c^-}$ baryons were reconstructed in the hadronic decay channels $\rm \Lambda_{c}^{+} \rightarrow p K^{-}\pi^{+}$ and $\rm \Lambda_{c}^{+}\to p K^{0}_{S}$ and respective charge conjugates. The measured differential cross sections as a function of transverse momentum ($p_{\rm T}$) and the $p_{\rm T}$-integrated $\mathrm{\Lambda_{c}^{+}}$ production cross section in pp and in p-Pb collisions are presented. The $\mathrm{\Lambda_{c}^{+}}$ nuclear modification factor ($R_\mathrm{pPb}$), calculated from the cross sections in pp and in p-Pb collisions, is presented and compared with the $R_\mathrm{pPb}$ of D mesons. The $\mathrm {\Lambda_{c}^{+}}/\mathrm {D^0}$ ratio is also presented and compared with the light-flavour baryon-to-meson ratios p$/\pi$ and $\Lambda /\mathrm {K^0_S}$, and measurements from other LHC experiments. The results are compared to predictions from model calculations and Monte Carlo event generators.

 

Submitted to: PRC
e-Print: arXiv:2011.06079 | PDF | inSPIRE
CERN-EP-2020-218

Figure 2

< p>Product of detector acceptance and efficiency for \Lc baryons in pp collisions at $\sqrt{s}=5.02~\TeV$, as a function of \pt. From left to right: \LctopKpi and \LctopKzS. The solid lines correspond to the $(A\times\varepsilon)$ for prompt \Lc, while the dotted lines represent $(A \times \epsilon)$ for \Lc baryons originating from beauty-hadron decays. The statistical uncertainties are smaller than the marker size. < /p>

Figure 3

< p>Product of detector acceptance and efficiency for \Lc baryons in \pPb collisions at \sqrtsNNfive, as a function of \pt. From left to right: \LctopKpi, \LctopKzS with the STD technique, and \LctopKzS with the MVA technique. The solid lines correspond to the $(A\times\varepsilon)$ for prompt \Lc, while the dotted lines represent $(A \times \epsilon)$ for \Lc baryons originating from beauty-hadron decays. The statistical uncertainties are smaller than the marker size. < /p>

Figure 6

< p>Comparison between the \pt-differential production cross section of prompt \Lcplus baryons in \pp collisions at $\sqrt{s}=7~\tev$~ and \sqrtsfive. The ratio between the cross sections is shown in the lower panel The statistical uncertainties are shown as vertical bars and the systematic uncertainties are shown as boxes.< /p>

Figure 7

< p>\pt-differential prompt \Lcplus-baryon production cross section in \pPb collisions at \sqrtsNNfive in the interval $1 < /p>

Figure 8

< p>The nuclear modification factor \RpPb of prompt \Lcplus baryons in \pPb collisions at \sqrtsNNfive as a function of \pt, compared to the \RpPb of D mesons~ (average of \DZero, \Dplus, and \Dstar in the range $1 < /p>

Figure 9

< p>The \LcD ratio as a function of \pt measured in pp collisions at \sqrtsfive and in \pPb collisions at \sqrtsNNfive.< /p>

Figure 10

< p>The \LcD ratio measured in pp collisions at \sqrtsfive, compared to theoretical predictions. The measurement is compared with predictions from MC generators (PYTHIA 8~, HERWIG 7~, POWHEG~), GM-VFNS~, a statistical hadronisation model~ (`SH model' in the legend) and a model which implements hadronisation via coalescence and fragmentation~. See text for model details.< /p>

Figure 11

< p>Left: The \LcD ratio measured in pp collisions at \sqrtsfive, compared to the measurement at \sqrtsseven~. PYTHIA 8 predictions are shown at both energies, for the Monash tune (solid lines) and with the Mode 2 CR tune (dotted lines). Right: the \LcD ratio at \sqrtsfive compared with the measurement by the CMS Collaboration at $|y| < /p>

Figure 12

< p>The \LcD ratio measured in \pPb collisions at \sqrtsNNfive, compared with the measurement at forward and backward rapidity~ by the LHCb collaboration. The measurements are shown as a function of \pt (left) and as a function of $y$ (right).< /p>

Figure 13

< p>The baryon-to-meson ratios in the light-flavour and charm sector; p/$\pi$ in pp collisions at $\sqrts = 5.02~\tev$ and $7~\tev$ and \pPb collisions at $\sqrtsNN = 5.02~\tev$~ (left), $\Lambda/\Kzs$ in pp collisions at $\sqrts = 7~\tev$ and \pPb collisions at $\sqrtsNN = 5.02~\tev$~ (middle), and \LcD in \pp collisions at $\sqrts = 5.02~\tev$ and \pPb collisions at $\sqrtsNN = 5.02~\tev$ (right). The data are compared to predictions from PYTHIA 8~. See text for model details.< /p>