Measurement of electrons from semileptonic heavy-flavour hadron decays at midrapidity in pp and Pb–Pb collisions at √sNN = 5.02 TeV

The differential invariant yield as a function of transverse momentum (pT) of electrons from semileptonic heavy-flavour hadron decays was measured at midrapidity in central (0–10%), semi-central (30–50%) and peripheral (60–80%) lead–lead (Pb–Pb) collisions at √sNN = 5.02 TeV in the pT intervals 0.5–26 GeV/c (0–10% and 30–50%) and 0.5–10 GeV/c (60–80%). The production cross section in proton–proton (pp) collisions at √s = 5.02 TeV was measured as well in 0.5 < pT < 10 GeV/c and it lies close to the upper band of perturbative QCD calculation uncertainties up to pT = 5 GeV/c and close to the mean value for larger pT. The modification of the electron yield with respect to what is expected for an incoherent superposition of nucleon–nucleon collisions is evaluated by measuring the nuclear modification factor RAA. The measurement of the RAA in different centrality classes allows in-medium energy loss of charm and beauty quarks to be investigated. The RAA shows a suppression with respect to unity at intermediate pT, which increases while moving towards more central collisions. Moreover, the measured RAA is sensitive to the modification of the parton distribution functions (PDF) in nuclei, like nuclear shadowing, which causes a suppression of the heavy-quark production at low pT in heavy-ion collisions at LHC

HΛ3 and H‾Λ‾3 lifetime measurement in Pb–Pb collisions at √sNN=5.02 TeV via two-body decay

An improved value for the lifetime of the (anti-)hypertriton has been obtained using the data sample of Pb–Pb collisions at √sNN = 5.02 TeV collected by the ALICE experiment at the LHC. The (anti-)hypertriton has been reconstructed via its charged two-body mesonic decay channel and the lifetime has been determined from an exponential fit to the dN/d(ct) spectrum. The measured value, τ = 242+34 −38 (stat.) ± 17 (syst.) ps, is compatible with representative theoretical predictions, thus contributing to the solution of the longstanding hypertriton lifetime puzzle

Measurement of the inclusive isolated photon production cross section in pp collisions at √s=7 TeV

The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of s= 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of | η| &amp;lt; 0.27 in pseudorapidity and a transverse momentum range of 10&amp;lt;pTγ&amp;lt;60GeV/c. The result extends the pT coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller pT. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other. © 2019, CERN for the benefit of the ALICE collaboration

Measurement of prompt D0, D+, D*+, and DS+ production in p–Pb collisions at √sNN = 5.02 TeV

The measurement of the production of prompt D0, D+, D*+, and DS+ mesons in proton–lead (p–Pb) collisions at the centre-of-mass energy per nucleon pair of sNN = 5.02 TeV, with an integrated luminosity of 292 ± 11 μb−1, are reported. Differential production cross sections are measured at mid-rapidity (−0.96 &amp;lt; ycms&amp;lt; 0.04) as a function of transverse momentum (pT) in the intervals 0 &amp;lt; pT&amp;lt; 36 GeV/c for D0, 1 &amp;lt; pT&amp;lt; 36 GeV/c for D+ and D*+, and 2 &amp;lt; pT&amp;lt; 24 GeV/c for D+ mesons. For each species, the nuclear modification factor RpPb is calculated as a function of pT using a proton-proton (pp) ref- erence measured at the same collision energy. The results are compatible with unity in the whole pT range. The average of the non-strange D mesons RpPb is compared with theoretical model predictions that include initial-state effects and parton transport model predictions. The pT dependence of the D0, D+, and D*+ nuclear modification factors is also reported in the interval 1 &amp;lt; pT&amp;lt; 36 GeV/c as a function of the collision centrality, and the central-to-peripheral ratios are computed from the D-meson yields measured in different centrality classes. The results are further compared with charged-particle measurements and a similar trend is observed in all the centrality classes. The ratios of the pT-differential cross sections of D0, D+, D*+, and DS+ mesons are also reported. The DS+ and D+ yields are compared as a function of the charged-particle multiplicity for several pT intervals. No modification in the relative abundances of the four species is observed with respect to pp collisions within the statistical and systematic uncertainties. [Figure not available: see fulltext.]. © 2019, The Author(s)

H-3(Lambda) and (3)((Lambda)over-bar)(H)over-bar lifetime measurement in Pb-Pb collisions at root s(NN)=5.02 TeV via two-body decay

An improved value for the lifetime of the (anti-)hypertriton has been obtained using the data sample of Pb\u2013Pb collisions at 1asNN=5.02 TeV collected by the ALICE experiment at the LHC. The (anti-)hypertriton has been reconstructed via its charged two-body mesonic decay channel and the lifetime has been determined from an exponential fit to the dN/d(ct) spectrum. The measured value, \u3c4=242 1238+34 (stat.) \ub1 17 (syst.) ps, is compatible with representative theoretical predictions, thus contributing to the solution of the longstanding hypertriton lifetime puzzle

Measurement of Lambda(1520) production in pp collisions at root s=7 TeV and p-Pb collisions at root s(NN)=5.02 TeV

The production of the \u39b (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at s=7TeV and in p\u2013Pb collisions at sNN=5.02TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel \u39b (1520) \u2192 pK - and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p\u2013Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (\u3c0, K, KS0, p, \u39b) describes the shape of the \u39b (1520) transverse momentum distribution up to 3.5GeV/c in p\u2013Pb collisions. In the framework of this model, this observation suggests that the \u39b (1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of \u39b (1520) to the yield of the ground state particle \u39b remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p\u2013Pb collisions on the \u39b (1520) yield

Measurement of Upsilon(1S) Elliptic Flow at Forward Rapidity in Pb-Pb Collisions at root s(NN)=5.02 TeV

The first measurement of the \u3b3(1S) elliptic flow coefficient (v2) is performed at forward rapidity (2.5&lt;4) in Pb-Pb collisions at sNN=5.02 TeV with the ALICE detector at the LHC. The results are obtained with the scalar product method and are reported as a function of transverse momentum (pT) up to 15 GeV/c in the 5%-60% centrality interval. The measured \u3b3(1S)v2 is consistent with 0 and with the small positive values predicted by transport models within uncertainties. The v2 coefficient in 2&lt;15 GeV/c is lower than that of inclusive J/\u3c8 mesons in the same pT interval by 2.6 standard deviations. These results, combined with earlier suppression measurements, are in agreement with a scenario in which the \u3b3(1S) production in Pb-Pb collisions at LHC energies is dominated by dissociation limited to the early stage of the collision, whereas in the J/\u3c8 case there is substantial experimental evidence of an additional regeneration component