Semi-leptonic Decays Of Heavy-flavour Hadrons Research Articles

ATLAS measurements of collective flow of heavy-flavor hadrons in small collision systems

Azimuthal anisotropy of heavy-flavor mesons in small systems has been studied with the ATLAS detector at the LHC. A template fit method is used to subtract non-flow contributions using a simultaneous fit of samples with low and high charged-particle multiplicities. The heavy-flavor flow in p+Pb is studied using multiple probes, including prompt D0 mesons, J/ψ, and muons from semi-leptonic decays of heavy-flavor hadrons. In pp collisions, flow coefficients for muons from heavy-flavor hadron decays, separated into charm- and bottom-hadron origins, are measured. The observed heavy-flavor azimuthal anisotropies in p+Pb and pp collisions are found to be qualitatively similar to those of light hadrons indicating a similar origin for both types of particles.

Dielectron and heavy-quark production in inelastic and high-multiplicity proton–proton collisions at [formula omitted

The measurement of dielectron production is presented as a function of invariant mass and transverse momentum (pT) at midrapidity (|ye|<0.8) in proton–proton (pp) collisions at a centre-of-mass energy of s=13 TeV. The contributions from light-hadron decays are calculated from their measured cross sections in pp collisions at s=7 TeV or 13 TeV. The remaining continuum stems from correlated semileptonic decays of heavy-flavour hadrons. Fitting the data with templates from two different MC event generators, PYTHIA and POWHEG, the charm and beauty cross sections at midrapidity are extracted for the first time at this collision energy: dσcc¯/dy|y=0=974±138(stat.)±140(syst.)±214(BR)μb and dσbb¯/dy|y=0=79±14(stat.)±11(syst.)±5(BR)μb using PYTHIA simulations and dσcc¯/dy|y=0=1417±184(stat.)±204(syst.)±312(BR)μb and dσbb¯/dy|y=0=48±14(stat.)±7(syst.)±3(BR)μb for POWHEG. These values, whose uncertainties are fully correlated between the two generators, are consistent with extrapolations from lower energies. The different results obtained with POWHEG and PYTHIA imply different kinematic correlations of the heavy-quark pairs in these two generators. Furthermore, comparisons of dielectron spectra in inelastic events and in events collected with a trigger on high charged-particle multiplicities are presented in various pT intervals. The differences are consistent with the already measured scaling of light-hadron and open-charm production at high charged-particle multiplicity as a function of pT. Upper limits for the contribution of virtual direct photons are extracted at 90% confidence level and found to be in agreement with pQCD calculations.

Measurement of heavy-flavour production, correlations and jets with ALICE

In this article, recent ALICE measurements of the RAA and v2 of electrons at mid-rapidity (|y|&lt;0.6) and muons at forward rapidity (2.5&lt;y&lt;4), from semi-leptonic decays of heavy-flavour hadrons in Pb–Pb collisions at [see formula in PDF] = 5.02 TeV are shown. The results of D-tagged jet production cross-section in pp collisions at √s =7 TeV are presented. In addition, the azimuthal correlation of D mesons with charged particles in p–Pb collisions at [see formula in PDF] = 5.02 TeV, and electrons from semi-leptonic decays of heavyflavour hadrons with charged particles in p–Pb and Pb–Pb collisions at [see formula in PDF] = 5.02 TeV are reported.

Measurements of heavy-flavour production in p–Pb collisions with ALICE: Quark Matter 2015

The production of open heavy-flavour particles was studied in p–Pb collisions at sNN=5.02 TeV using the ALICE detector. Three separate observables were used: the hadronic decays of D mesons at mid-rapidity, and semileptonic decays of heavy-flavour hadrons to electrons and muons at mid-rapidity and forward rapidity, respectively. The most recent ALICE measurements of the nuclear modification factor, RpPb, of open charm and beauty are reported, along with the centrality and multiplicity dependence of D-meson production in p–Pb collisions.

Heavy-quark production and elliptic flow in Au + Au collisions atsNN=62.4GeV

We present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity (|y|< 0.35) in Au+Au collisions at sNN−−−−√=62.4 GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range 1<peT<5 GeV/c. The invariant yield per binary collision is slightly enhanced above the p+p reference in Au+Au 0%–20%, 20%–40%, and 40%–60% centralities at a comparable level. At this low beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The v2 of electrons from heavy-flavor decays is nonzero when averaged between 1.3<peT<2.5 GeV/c for 0%–40% centrality collisions at sNN−−−−√=62.4 GeV. For 20%–40% centrality collisions, the v2 at sNN−−−−√=62.4 GeV is smaller than that for heavy-flavor decays at sNN−−−−√=200 GeV. The v2 of the electrons from heavy-flavor decay at the lower beam energy is also smaller than v2 for pions. Both results indicate that the heavy quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at sNN−−−−√=200 GeV.

Measurement of electrons from semileptonic heavy-flavor hadron decays inppcollisions ats=2.76 TeV

The $p_{\rm T}$-differential production cross section of electrons from semileptonic decays of heavy-flavor hadrons has been measured at mid-rapidity in proton-proton collisions at $\sqrt{s} = 2.76$ TeV in the transverse momentum range 0.5 < $p_{\rm T}$ < 12 GeV/$c$ with the ALICE detector at the LHC. The analysis was performed using minimum bias events and events triggered by the electromagnetic calorimeter. Predictions from perturbative QCD calculations agree with the data within the theoretical and experimental uncertainties.

Measurements of heavy-flavour decay leptons in pp, p-Pb, and Pb-Pb collisions with ALICE

We present measurements of electrons and muons originating from the semi-leptonic decays of heavy-flavour hadrons at central and forward rapidities with ALICE in pp ( = 2.76 and 7 TeV), p-Pb ( = 5.02 TeV), and Pb-Pb ( = 2.76 TeV) collisions. The measured pT-differential production cross sections in pp collisions, the nuclear modification factors in p-Pb and Pb-Pb, and the v2 measurements in Pb-Pb collision are disgusted. In addition, the angular correlation distribution between heavy-flavour decay electrons and charged particles, measured in p-Pb collisions, is shown. The results are compared to their corresponding theoretical predictions.

Measurement of electrons from heavy-flavour decays in Pb-Pb collisions at = 2.76 TeV with ALICE

The measurement of heavy-flavour (charm and beauty) production in ultra-relativistic heavy-ion collisions provides an important contribution to the study of the properties of the hot and dense medium created in such collisions. One approach to measure heavy-flavour production is via electrons from semi-leptonic decays of heavy-flavour hadrons. In this contribution we present the nuclear modification factor (RAA) and the azimuthal anisotropy (v2) of heavy-flavour decay electrons in Pb-Pb collisions at = 2.76 TeV, which are sensitive to the interaction of c and b quarks with the medium. We also present, for the first time, the azimuthal angular correlations of heavy-flavour decay electrons and charged hadrons, Δϕ(HFE,h), in Pb-Pb collisions and the corresponding near-side yield ratio (IAA).

Heavy-flavour decay lepton measurements in pp, p–Pb, and Pb–Pb collisions with ALICE at the LHC

We present the measurements of electrons and muons from the semi-leptonic decays of heavy-flavour hadrons measured in the central and forward rapidity regions with ALICE in pp ( s = 2.76 TeV and 7 TeV), Pb–Pb ( s NN = 2.76 TeV ), and p–Pb ( s NN = 5.02 TeV ) collisions at the LHC. The p T -differential production cross section in pp collisions, the elliptic flow in Pb–Pb collisions, and the nuclear modification factor in Pb–Pb and p–Pb collisions are shown. The results are compared to theoretical predictions.

Investigation of charm and beauty production via semileptonic decays of heavy-flavour hadrons in pp at 7 TeV and Pb–Pb at 2.76 TeV with ALICE

Electron spectra measured with ALICE at mid-rapidity are used to study the production of hadrons carrying a charm or a beauty quark. The production cross section of electrons from heavy-flavour hadron decays is measured in pp collisions at = 7 TeV. Electrons from the beauty decays are identified via the displacement from the interaction vertex. From the electron spectra measured in Pb–Pb collisions, we determine the nuclear modification factor, which is sensitive to the heavy-quark energy loss in a hot strongly interacting medium.