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

A measurement of the production of prompt $\Lambda_{\rm c}^{+}$ baryons in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02 $ TeV with the ALICE detector at the LHC is reported. The $\Lambda_{\rm c}^{+}$ and $\overline{\Lambda}_{\rm c}^{-}$ were reconstructed at midrapidity ($|y|<0.5$) via the hadronic decay channel $\Lambda_{\rm c}^{+}\rightarrow {\rm p} {\rm K}_{\rm S}^{0}$ (and charge conjugate) in the transverse momentum and centrality intervals $6<p_{\rm T}<12$ GeV/$c$ and 0-80%. The $\Lambda_{\rm c}^{+}$/D$^0$ ratio, which is sensitive to the charm quark hadronisation mechanisms in the medium, is measured and found to be larger than the ratio measured in minimum-bias pp collisions at $\sqrt{s} = 7$ TeV and in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02 $ TeV. In particular, the values in p-Pb and Pb-Pb collisions differ by about two standard deviations of the combined statistical and systematic uncertainties. The $\Lambda_{\rm c}^{+}$/D$^0$ ratio is also compared with model calculations including different implementations of charm quark hadronisation. The measured ratio is reproduced by models implementing a pure coalescence scenario, while adding a fragmentation contribution leads to an underestimation. The $\Lambda_{\rm c}^{+}$ nuclear modification factor, $R_{\rm AA}$, is also presented. The measured values of the $R_{\rm AA}$ of $\Lambda_{\rm c}^{+}$, D$_{\rm s}$ and non-strange D mesons are compatible within the combined statistical and systematic uncertainties. They show, however, a hint of a hierarchy $(R_{\rm AA}^{{\rm D}^{0}}<R_{\rm AA}^{{\rm D}_{\rm s}}<R_{\rm AA}^{\Lambda_{\rm c}^{+}})$, conceivable with a contribution of recombination mechanisms to charm hadron formation in the medium.


Introduction
Measurements of the production of open-heavy flavour hadrons in heavy-ion collisions provide important information on the properties of the Quark-Gluon Plasma (QGP), the state of strongly-interacting matter formed at the very high temperatures and energy densities reached in heavy-ion collisions [1,2].Several measurements of the production and elliptic flow of D mesons and leptons from the decay of heavyflavour hadrons in Pb-Pb collisions at the LHC and in Au-Au collisions at RHIC [3,4] indicate that charm quarks interact strongly with the medium constituents.In-medium energy loss is studied via the nuclear modification factor, R AA , defined as the ratio of the yield in Pb-Pb collisions and that in pp collisions scaled by the number of binary nucleon-nucleon collisions.A model [5,6] including a significant fraction of low and intermediate transverse momentum (p T ) charm and beauty quarks hadronising via recombination (or coalescence) with light quarks from the medium better describes the experimental results.This mechanism is expected to also affect the production of D + s given the strange-quark rich environment of the created medium.At higher transverse momentum (p T > 7 GeV/c at LHC energies [7]) hadronisation by vacuum fragmentation is expected to be the dominant production mechanism.
In this context, the study of charm baryons is essential to understand charm hadronisation.Models including coalescence predict an enhanced baryon-to-meson ratio at low and intermediate transverse momentum in comparison to that expected in pp collisions.This effect adds to the hadron-mass dependent transverse-momentum shift due to the presence of radial flow in heavy-ion collisions, that is able to explain the observed increase of the baryon-to-meson ratio in the light sector up to about 2 GeV/c [8].The study of non-strange D-mesons, D + s and Λ + c could help to disentangle the role of recombination and radial flow, because of the smaller mass differences than for light-flavour hadrons.
with a branching ratio (BR) equal to (1.58 ± 0.08)% and K 0 S → π + π − with BR = (69.20 ± 0.05)% [19].The D 0 mesons were reconstructed in the decay channel D 0 → K − π + with BR = (3.93 ± 0.04)% [19].The Λ c and D 0 candidates were reconstructed in the same transverse momentum, rapidity and centrality intervals.The analysis benefits from the tracking and particle identification capabilities of the ALICE central barrel detectors located within a large solenoidal magnet that provides a magnetic field of 0.5 T parallel to the LHC beam axis.A complete description of the ALICE apparatus and its performance can be found in Refs.[17,20].The main detectors used in this analysis include the Inner Tracking System (ITS) [21], the Time Projection Chamber (TPC) [22], the Time-Of-Flight detector (TOF) [23] and the V0 detector [24] located inside the solenoidal magnet, as well as the Zero Degree Calorimeters (ZDC) [17] located in the LHC tunnel at about ±112.5 m from the nominal interaction point and composed of two proton and two neutron calorimeters.
The analysed data sample consists of about 83 ×10 6 Pb-Pb collisions at √ s NN = 5.02 TeV, corresponding to an integrated luminosity of L int ≈ 13.4 µb −1 .The interaction trigger was provided by the coincident signals from the two arrays of the V0 detector, covering the pseudorapidity intervals −3.7 < η < −1.7 and 2.8 < η < 5.1.Background events from beam-gas interactions were removed in the offline analysis using the timing information provided by the V0 and the neutron ZDC.Only events with a primary vertex reconstructed within ±10 cm from the centre of the detector along the beam line were considered for the analysis.Events were selected in the centrality class 0-80%, defined in terms of percentiles of the hadronic Pb-Pb cross section, using the amplitudes of the signals in the V0 arrays [25].
The Λ c candidates were constructed by combining a proton candidate track with a K 0 S candidate identified through its V-shaped neutral decay topology (V 0 ).The charged tracks and the K 0 S candidates were selected as described in Ref. [11] for pp collisions with additional requirements to reduce the larger combinatorial background due to the higher charged-track multiplicity in Pb-Pb with respect to pp collisions.In particular, candidate proton tracks were required to have a hit in the innermost ITS layer and tighter selections on the K 0 S were applied: a maximum distance of closest approach between the V 0 decay tracks of 0.4 cm, a minimum cosine of the V 0 pointing angle to the primary vertex of 0.9998, a minimum p T of the K 0 S candidates of 1 GeV/c, and a cut in the Armenteros-Podolanski space [26] to remove contributions from Λ decays.The identification of protons was based on the specific ionisation energy loss dE/dx in the TPC and on the time of flight measured with the TOF detector, using as a discriminating variable (n σ ) the difference between the measured value and the expected value for the proton mass hypothesis divided by the detector resolution.A |n σ | < 3 selection was applied on the TPC dE/dx and TOF time-of-flight measurements for tracks with p T < 3 GeV/c.For tracks with p T > 3 GeV/c an asymmetric selection was used to limit the contamination from pions in the TPC and from kaons in the TOF and the requirements were −3 < n TPC σ < 2 and −2 < n TOF σ < 3 for the TPC and TOF signals.
Tracks without TOF information were discarded.The Λ c candidates were selected requiring a cosine of the proton emission angle in the Λ c centre-of-mass system with respect to the Λ c momentum direction larger than 0.5.A selection on the signed transverse impact parameter of the proton, i.e. the distance of  closest approach between the proton track and the primary vertex, larger than 0.003 cm was also applied (the sign of the impact parameter is defined as positive when the angle between the Λ c flight line and the momentum vector is smaller than 90 • ).
The D 0 candidates were reconstructed by combining pairs of tracks with the proper charge sign combination and selected in the interval 6 < p T < 12 GeV/c using the same criteria described in Ref. [18] for the interval 6 < p T < 7 GeV/c in the 10% most central Pb-Pb collisions.
After all selections, the acceptance in rapidity for Λ c and D 0 candidates drops steeply to zero for |y| > 0.8 in the p T interval used for the analysis.Therefore, a fiducial acceptance cut |y| < 0.8 was applied as described in Refs.[11] and [18].
The Λ c and D 0 raw yields were extracted by fitting the invariant mass distributions of the candidates passing the selection criteria.The fit functions consist of a Gaussian to describe the signal and an exponential to describe the background.In the case of the Λ c , the width of the Gaussian was fixed to the value obtained from Monte Carlo simulations.The stability of the Λ c signal extraction was verified by fitting the invariant mass distribution after the subtraction of the background evaluated with an eventmixing technique and no discrepancy between the two approaches was observed.For the D 0 -meson yield, the contribution of signal candidates with the wrong K-π mass assignment (reflections) to the invariant-mass distribution was taken into account by including an additional term, parameterised from simulations with a double-Gaussian shape, in the fit function [27].
The invariant mass distributions of the selected Λ c and D 0 candidates are shown in Fig. 1.
The prompt Λ + c (D 0 ) production yield was calculated as dN where N raw is the raw yield (sum of particles and antiparticles) in the transverse momentum interval of width ∆p T , f prompt is the fraction of prompt Λ c (D 0 ) in the raw yield, (Acc × ε) is the product of acceptance and reconstruction efficiency for prompt Λ c (D 0 ), BR is the branching ratio of the considered decay mode and N evt is the number of events considered for the analysis.The correction factor for the rapidity coverage c ∆y was computed as the ratio of the generated Λ c (D 0 ) yield in |y| < 0.8 and that in |y| < 0.5.The factor 1/2 takes into account that the raw yield is the sum of particles and antiparticles, while the production yield is reported as their average.
The correction for the detector acceptance and reconstruction efficiency was determined by means of Monte Carlo (MC) simulations.The underlying Pb-Pb events at √ s NN = 5.02 TeV were simulated using the HIJING v1.383 [28] generator and prompt and feed-down Λ c (D 0 ) were added using the PYTHIA v6.421 [29] generator with Perugia 11 tune.The generated particles were transported through the ALICE detector using the GEANT3 [30] package.A realistic detector response was introduced in the simulations to reproduce the performance of the ALICE detector system during data taking.
The p T distributions of the Λ c and D 0 in PYTHIA were corrected in order to obtain more realistic distributions.The same p T -dependent weighting factor, calculated as the ratio of the measured D 0 p T distribution in finer p T bins [18] and the one simulated with PYTHIA, was used for both particles.The Λ c and D 0 reconstruction efficiency in the large centrality class 0-80% was obtained as the weighted average of the efficiencies in smaller centrality classes to take into account the variation of the efficiency and the scaling of the yields of the Λ c baryons and D 0 mesons with centrality.The applied weights were calculated as the product of the R AA of the D 0 and the average number of nucleon-nucleon collisions (< N coll >) in the centrality class considered [18].The (Acc × ε) value is about 6% for prompt and about 9% for feed-down Λ c and about 8% for prompt and about 11% for feed-down D 0 .
The prompt Λ c (D 0 ) fraction, f prompt , was calculated as The contribution of Λ c (D 0 ) from beauty-hadron decays was estimated using the FONLL [31,32] beauty-production cross sections as described in detail in Ref. [33].The fraction of beauty quarks that fragment to beauty hadrons and subsequently decay into Λ c baryons f (b → Λ c ) = 0.073 was taken from Ref. [34].The beauty-hadron decay kinematics were modeled using the EVTGEN [35] package.The (Acc × ε) feed-down term for both particles was calculated from the Monte Carlo simulations described above.The average nuclear overlap function, T AA , was estimated via Glauber model calculations [36,37].In this formalism the nuclear modification factor R AA is then the ratio of the yield in Pb-Pb collisions and the production cross section in pp collisions scaled by T AA .
A hypothesis on the R feed-down AA of feed-down Λ c and D 0 is used.For the D 0 , the hypothesis is the same as in other analyses (e.g. in Ref. [18]): the central value is which is justified by the CMS measurement of J/ψ from B-meson decays [38] and by the ALICE and CMS measurements of D mesons [18,39] indicating that prompt charm mesons are more suppressed than non-prompt charm mesons.The ratio is varied in the interval 1 < R feed-down D 0 AA /R The first term is the same as for the D 0 and thus the same hypothesis is adopted.The second term is varied in the range 0.5-1.5 to calculate the systematic uncertainty.The upper limit is determined aposteriori such that R feed-down Λ + c AA < 2 as suggested by the fact that no baryon R AA exceeds this value.The uncertainties on the two terms are added in quadrature.The resulting values of f prompt are about 0.93 and 0.81 for the Λ c and D 0 , respectively.A summary of the systematic uncertainties on the corrected Λ + c and D 0 yields is shown in Tab. 1.The D 0 systematic uncertainties on the particle identification (PID), tracking and cut variation are taken from Ref. [18] and are not discussed in the following.
The systematic uncertainty on the raw-yield extraction for Λ c and D 0 was estimated by repeating the fits several times varying (i) the lower and upper limits of the fit range, (ii) the background fit function and (iii) only in the case of the Λ c , considering the Gaussian mean and width as free parameters in the fit.In addition, a bin-counting method was used, in which the signal yield was obtained by integrating the invariant-mass distribution after subtracting the background estimated from an exponential fit to the sidebands.
For the Λ c , the systematic uncertainty on the tracking efficiency was evaluated by comparing the probability of matching tracks reconstructed in the TPC to ITS hits in data and simulation and by varying the quality cuts to select the tracks used in the analysis.The contribution due to the variation of the quality cuts was evaluated using protons from Λ decays and an inclusive K 0 S sample and by calculating the ratio of the corrected yields obtained using different selection criteria.The uncertainty on the ITS-TPC matching efficiency is defined as the relative difference of the matching efficiency in data and simulations after weighting the relative abundances of primary and secondary particles in the simulations to match those in data.The latter were estimated via fits to the track impact-parameter distributions.The values calculated as a function of track momentum were propagated to the p T -differential uncertainty of the Λ c using a Monte Carlo simulation.A 3% systematic uncertainty on the ITS-TPC matching efficiency of proton tracks was assigned while for the K 0 S the matching is not required.The uncertainty resulting from these studies was added in quadrature to the uncertainty on the track selection.
The systematic uncertainty on the Λ c PID efficiency was evaluated using protons from the decay of Λ baryons.The ratio of the Λ yield measured with PID to that measured without PID was calculated in both data and MC and their difference was used to estimate the systematic uncertainty.Systematic uncertainties on the efficiencies can also arise from possible differences in the distributions and resolutions of selection variables between data and simulation.The systematic effect induced by these imperfections was estimated by repeating the analysis varying the main selection criteria for the candidates.The efficiencies determined from the simulations depend also on the generated p T distributions of the Λ c and the D 0 .The central values of the correction factors were obtained by reweighting the Λ c and D 0 distributions generated by PYTHIA as described above.For the D 0 , the efficiencies calculated with and without the p T weights are compatible and therefore no uncertainty was assigned.For the Λ c , the systematic uncertainty was defined by considering the variation of the efficiencies determined with different generated p T shapes.The new Λ c p T shape was calculated by multiplying the measured D 0 p T distribution with the Λ + c /D 0 ratios predicted by the models [6] and [41].
Finally, the efficiencies in the centrality class 0-80% depend on the centrality weights used to combine the efficiencies in the smaller centrality classes.The stability of the efficiencies against the variation of the centrality weights was tested by recalculating the efficiencies without weighting for N coll and, for the Λ c , using as an alternative centrality weight the product Λ/K 0 S • N coll , where the ratio Λ/K 0 S is taken from Ref. [8].
The systematic uncertainty on the subtraction of feed-down from beauty-hadron decays was estimated by varying (i) the p T -differential cross section of feed-down Λ c (D 0 ) from FONLL calculations within the theoretical uncertainties (see Ref. [11] for details on the Λ c and Ref. [33] for the D 0 ) and (ii) the ratio of prompt and feed-down R AA as described above.
The production yields of Λ c and D 0 also have a global systematic uncertainty due to the branching ratio.

Results
The yield of prompt The measured Λ + c /D 0 ratio is shown in Fig. 2. The systematic uncertainty of the Λ + c -baryon production arising from the tracking efficiency was treated as fully correlated to that of the D 0 meson.The contribution to the feed-down uncertainty related to heavy-quark energy loss and that originating from the FONLL uncertainty on the feed-down Λ + c and D 0 cross sections were treated as fully correlated when propagated to the ratio.All the other sources of uncertainty were considered as uncorrelated.In the left panel of Fig. 2, the Λ + c /D 0 ratio measured in Pb-Pb collisions is compared with the results obtained by the ALICE Collaboration in minimum-bias pp and p-Pb collisions at √ s = 7 TeV and √ s NN = 5.02 TeV [11], respectively.The ratio measured in Pb-Pb collisions is higher than that measured in pp and p-Pb collisions.In particular, the values in p-Pb and Pb-Pb collisions differ by about two standard deviations of the combined statistical and systematic uncertainties.
The Λ + c /D 0 ratio in Pb-Pb collisions is compared with theoretical model calculations in the right panel of Fig. 2. The Catania model [7] provides two different treatments of hadronisation.In one case, charm quarks hadronise via coalescence only.In the other case, a coalescence plus vacuum fragmentation modelling of hadronisation is considered: at increasing p T the coalescence probability decreases and eventually vacuum fragmentation takes over.For D 0 mesons, the shape of the fragmentation function is tuned assuring that the experimental results on D-meson production in pp collisions are well described by a fragmentation hadronisation mechanism.Data from e + e − collisions are used to fix the shape of the fragmentation functions for Λ + c .The coalescence mechanism is treated as a three-quark process and implemented through the Wigner formalism.The momentum spectrum of hadrons formed by coalescence is obtained from the quark phase-space distributions and the hadron wave function.The width parameters of the hadron wave functions are calculated from the charge radius of the hadrons according to the quark model.The hadron wave function normalisation is determined by requiring a total recombination probability for charm quarks equal to unity for zero-momentum heavy quarks.Moreover, the contributions from the first excited states for D and Λ c hadrons were included in the calculations.The experimental results are described by the model calculation including coalescence only.The curve obtained by modelling charm hadronisation via vacuum fragmentation plus coalescence, which describes the Λ + c /D 0 ratio measured in Au-Au collisions at RHIC energy [43], significantly underestimates the measurement in Pb-Pb collisions at the LHC.The Shao-Song model [15,16] implements coalescence by assuming that quarks combination takes place mainly for quarks which have a given fraction of momentum of the hadron and, thus, it does not consider Wigner formalism to describe the spatial and momentum distribution of quarks in a hadron.It can not directly predict the absolute magnitude of the Λ + c /D 0 ratio because the relative production of single-charm baryons and single-charm mesons R BM is treated as a parameter of the model.The curve obtained by considering R BM = 0.425, which is the value needed to describe the results in pp and p-Pb collisions, underestimates the Λ + c /D 0 ratio measured in Pb-Pb collisions.An R BM = 1.2 is needed to achieve a better description of the experimental results in Pb-Pb collisions.However, the hadronisation mechanism via quark coalescence included in the model is responsible of the p T dependence of the Λ + c /D 0 ratio, which needs to be verified by comparing to a measurement at lower p T .The R AA of prompt Λ + c was obtained by considering as reference the Λ + c cross section measured in p-Pb collisions at √ s NN = 5.02 TeV [11] scaled by 1/A (A = 208) and corrected for the different rapidity coverage of the p-Pb measurement.The cross section measured in p-Pb was scaled in each p T interval to |y| < 0.5 using a correction factor obtained with FONLL calculations [31,32].The correction factor was determined from the ratios of the cross sections calculated with FONLL in the rapidity intervals |y| < 0.5 and −0.96 < y < 0.04.Since FONLL does not provide predictions for Λ + c baryons, the average of the correction factors obtained for D 0 , D + and bare charm quarks, which was found to be 1.024 ± 0.008, was used.The choice of using the p-Pb cross section to obtain the reference for the R AA was motivated by the fact that it was measured up to p T = 12 GeV/c, while the measurement in pp collisions at √ s = 7 TeV in |y| < 0.5 only reaches p T = 8 GeV/c.In addition, the Λ + c nuclear modification factor measured in p-Pb collisions is consistent with unity for p T > 2 GeV/c [11].The Λ + c reference cross section in 6 < p T < 12 GeV/c was obtained by combining the results in the transverse momentum intervals 6 < p T < 8 GeV/c and 8 < p T < 12 GeV/c.The uncertainties were propagated treating the statistical and the systematic uncertainties on the yield extraction as uncorrelated and the other sources of systematic uncertainty as correlated in p T .The Λ + c R AA also has a 3.75% uncertainty due to the normalisation of the Λ + c p-Pb cross section at √ s NN = 5.02 TeV [11] and a 2.4% uncertainty on the average nuclear overlap function T AA , which were added in quadrature.In the left panel of Fig. 3, the R AA of prompt Λ + c is compared with Catania model calculations [7].The three curves are obtained by considering different treatments of the hadronisation mechanisms in pp and Pb-Pb collisions.The short-dashed curve represents the Λ + c R AA as obtained by including both vacuum fragmentation and quark coalescence for charm hadronisation in Pb-Pb and only fragmentation in pp collisions.The longdashed curve includes only coalescence in Pb-Pb and fragmentation plus coalescence in pp collisions.The solid curve is obtained by considering fragmentation plus coalescence in both collision systems.The limited precision and the large p T interval of this first measurement prevent us to draw a firm conclusion on which combination of the hadronisation mechanisms in the two collision systems better describes the result.Moreover, the comparison between the different scenarios obtained from the Catania model demonstrates that it is crucial to also understand the Λ + c production mechanism in pp collisions to interpret the R AA measurement.The right panel of Fig. 3 shows the R AA of prompt Λ + c baryons measured in the 0-80% centrality class (that is dominated by the 0-10% production given the scaling of the yields with N coll • R AA ) compared with the average nuclear modification factors of non-strange D mesons, D + s mesons, and charged particles measured in the 0-10% centrality class [18].The R AA of charged particles is smaller than that of D mesons by more than 2σ of the combined statistical and systematic uncertainties up to p T = 8 GeV/c, while they are compatible within 1σ for p T > 10 GeV/c.The R AA values of D + s mesons are larger than those of non-strange D mesons, but the two measurements are compatible within one standard deviation of the combined uncertainties [18].A hint of a larger Λ + c R AA with respect to non-strange D mesons is observed, although the results are compared for different centrality classes.A D 0 R AA = 0.27 ± 0.01(stat.)± 0.04(syst.)was measured in 6 < p T < 12 GeV/c in the 0-80% centrality class.The D 0 R AA has also a 3.5% uncertainty arising from the normalisation of the cross section measured in pp collisions at √ s = 7 TeV, and a 2.4% uncertainty on the average nuclear overlap function T AA .The p T -differential cross section of prompt D 0 mesons with |y| < 0.5 in Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV ALICE Collaboration pp collisions at √ s = 5.02 TeV, used as reference for the nuclear modification factor, was obtained by scaling the measurement at √ s = 7 TeV [44] to √ s = 5.02 TeV using FONLL calculations [31,32].The scaling was applied to the D 0 cross section obtained in 6 < p T < 12 GeV/c by combining the results in the p T intervals of the measurement at √ s = 7 TeV.The statistical and the systematic uncertainties on the yield extraction were propagated as uncorrelated.The other contributions to the systematic uncertainty were considered as fully correlated among the p T intervals.A difference of about 1.7σ is obtained when comparing the Λ + c R AA with that of the D 0 in 6 < p T < 12 GeV/c and 0-80% centrality interval.This observation is qualitatively in agreement with a scenario where a significant fraction of charm quarks hadronise via coalescence with light quarks from the medium leading to an enhanced baryon production with respect to that of mesons.

Summary
The measurement of the production of prompt Λ + c baryons in the 0-80% most central Pb-Pb collisions at √ s NN = 5.02 TeV was presented.The result was obtained at midrapidity, |y| < 0.5, in the 6 < p T < 12 GeV/c transverse momentum interval.The Λ + c /D 0 ratio is larger than the ratio measured in pp and p-Pb collisions at √ s = 7 TeV and √ s NN = 5.02 TeV [11], respectively.The Λ + c /D 0 ratio measured in Pb-Pb collisions is described by a model calculation implementing only charm quark hadronisation via quark coalescence and it is underestimated when also vacuum fragmentation is included.The comparison of the Λ + c nuclear modification factor with non-strange D and D + s meson results, which were measured in 0-10% most central Pb-Pb collisions, suggests a hint of a hierarchy, conceivable in a scenario where charm quark hadronisation can occur via coalescence processes, thus enhancing the Λ + c -baryon and D + smeson production with respect to non-strange D mesons.However, the limited precision of this first measurement prevents us from drawing a firm conclusion.
A higher precision for a Λ + c -baryon production measurement with finer granularity in p T and centrality will be achieved with future datasets to be collected during LHC Run 2 and, in particular, during the LHC Run 3 and 4, following the major upgrade of the ALICE apparatus [45,46].
The ALICE Collaboration would like to thank all its engineers and technicians for their invaluable contributions to the construction of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex.The ALICE Collaboration gratefully acknowledges the resources and support provided by all Grid centres and the Worldwide LHC Computing Grid (WLCG) collaboration.The ALICE Collaboration acknowledges the following funding agencies for their support in building and running the ALICE detector: A.

Figure 1 :
Figure 1: Invariant-mass distributions for the Λ c (left) and D 0 (right) candidates in the momentum interval 6 < p T < 12 GeV/c and for the 0-80% centrality class.The dashed curves represent the fit to the background, while the solid curves represent the total fit function.
estimate the systematic uncertainty.Since no measurements of beauty-baryon production in nucleus-nucleus collisions are available, for the Λ c the central hypothesis was taken from model calculations which predict R feed-down Λ + c AA /R prompt Λ + c AA = 2 when considering c and b quark fragmentation and energy loss in the medium [40].The ratio R feed-down Λ + c AA /R prompt Λ + c AA was decomposed into two terms to estimate the uncertainty on the assumption:

Figure 2 :
Figure 2: Λ + c /D 0 ratio as a function of p T in 0-80% most central Pb-Pb collisions compared with the measurements in pp and p-Pb collisions [11] (left), and model calculations [7] (right).Statistical and systematic uncertainties are presented as vertical bars and boxes, respectively.

Figure 3 :
Figure 3: R AA of prompt Λ + c compared with model calculations [7, 15, 16] (left), and the non-strange D mesons, D + s , and charged particle R AA in 0-10% most central Pb-Pb collisions for p T > 1 GeV/c [18,42] (right).Statistical, systematic and normalisation uncertainties are presented as vertical bars, empty boxes and shaded boxes around unity, respectively.
I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences and Nationalstiftung für Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and Fundac ¸ão de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil; Ministry of Science & Technology of China (MSTC), National Natural Science Foundation of China (NSFC) and Ministry of Education of China (MOEC) , China; Ministry of Science and Education, Croatia; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Cubaenergía, Cuba; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research -Natural Sciences, the Carlsberg Foundation and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat à l'Energie Atomique (CEA) and Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Sci-Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV ALICE Collaboration Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV ALICE Collaboration A The ALICE Collaboration Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV ALICE Collaboration Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV ALICE Collaboration

Table 1 :
Systematic uncertainties on the corrected yields.When the uncertainty was found to be < 1%, it was considered negligible (negl. in the table).