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

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.

 

Phys. Rev. C 104 (2021) 054905
e-Print: arXiv:2011.06079 | PDF | inSPIRE
CERN-EP-2020-218

Figure 2

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.

Figure 3

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.

Figure 6

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.

Figure 7

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

Figure 8

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

Figure 9

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

Figure 10

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.

Figure 11

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|

Figure 12

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).

Figure 13

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.