Search results for "Pb–Pb collisions"
showing 8 items of 18 documents
Pseudorapidity dependence of the anisotropic flow of charged particles in Pb–Pb collisions at √sNN = 2.76 TeV
2016
We present measurements of the elliptic (v2), triangular (v3) and quadrangular (v4) anisotropic azimuthal flow over a wide range of pseudorapidities (−3.5 <η<5). The measurements are performed with Pb–Pb collisions at √sNN=2.76TeVusing the ALICE detector at the Large Hadron Collider (LHC). The flow harmonics are obtained using two-and four-particle correlations from nine different centrality intervals covering central to peripheral collisions. We find that the shape of vn(η)is largely independent of centrality for the flow harmonics n =2–4, however the higher harmonics fall off more steeply with increasing |η|. We assess the validity of extended longitudinal scaling of v2by comparing to low…
Linear and non-linear flow mode in Pb–Pb collisions at √sNN = 2.76 TeV
2017
The second and the third order anisotropic flow, V2 and V3, are mostly determined by the corresponding initial spatial anisotropy coefficients, ε2 and ε3, in the initial density distribution. In addition to their dependence on the same order initial anisotropy coefficient, higher order anisotropic flow, Vn(n>3), can also have a significant contribution from lower order initial anisotropy coefficients, which leads to mode-coupling effects. In this Letter we investigate the linear and non-linear modes in higher order anisotropic flow Vn for n=4, 5, 6 with the ALICE detector at the Large Hadron Collider. The measurements are done for particles in the pseudorapidity range |n| < 0.8 and the tran…
Centrality dependence of the pseudorapidity density distribution for charged particles in Pb–Pb collisions at √sNN = 5.02 TeV
2017
We present the charged-particle pseudorapidity density in Pb–Pb collisions at √sNN = 5.02 TeV in centrality classes measured by ALICE. The measurement covers a wide pseudorapidity range from −3.5 to 5, which is sufficient for reliable estimates of the total number of charged particles produced in the collisions. For the most central (0–5%) collisions we find 21 400 ± 1 300, while for the most peripheral (80–90%) we find 230 ± 38. This corresponds to an increase of (27 ± 4)% over the results at √sNN = 2.76 TeV previously reported by ALICE. The energy dependence of the total number of charged particles produced in heavy-ion collisions is found to obey a modified power-law like behaviour. The …
Measurement of deuteron spectra and elliptic flow in Pb–Pb collisions at √sNN = 2.76 TeV at the LHC
2017
The transverse momentum (pT) spectra and elliptic flow coefficient (v2) of deuterons and anti-deuterons at mid-rapidity (|y| 1.8 GeV/c within the experimental uncertainties. The measurement of the coalescence parameter B2 is performed, showing a pT dependence in contrast with the simplest coalescence model, which fails to reproduce also the measured v2 coefficient. In addition, the coalescence parameter B2 and the elliptic flow coefficient in the 20–40% centrality interval are compared with the AMPT model which is able, in its version without string melting, to reproduce the measured v2(pT) and the B2(pT) trend. peerReviewed
Measurement of the production of high-pT electrons from heavy-flavour hadron decays in Pb–Pb collisions at √sNN = 2.76 TeV
2017
Electrons from heavy-flavour hadron decays (charm and beauty) were measured with the ALICE detector in Pb–Pb collisions at a centre-of-mass of energy √sNN = 2.76 TeV. The transverse momentum (pT) differential production yields at mid-rapidity were used to calculate the nuclear modification factor RAA in the interval 3 < pT < 18 GeV/c. The RAA shows a strong suppression compared to binary scaling of pp collisions at the same energy (up to a factor of 4) in the 10% most central Pb–Pb collisions. There is a centrality trend of suppression, and a weaker suppression (down to a factor of 2) in semi-peripheral (50–80%) collisions is observed. The suppression of electrons in this broad pT interval …
Freeze-out radii extracted from three-pion cumulants in pp, p–Pb and Pb–Pb collisions at the LHC
2014
In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose-Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correl…
Analysis of the apparent nuclear modification in peripheral Pb–Pb collisions at 5.02 TeV
2019
Charged-particle spectra at midrapidity are measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair √sNN = 5.02 TeV and presented in centrality classes ranging from most central (0–5%) to most peripheral (95–100%) collisions. Possible medium effects are quantified using the nuclear modification factor (RAA) by comparing the measured spectra with those from proton–proton collisions, scaled by the number of independent nucleon–nucleon collisions obtained from a Glauber model. At large transverse momenta (8<pT <20GeV/c), the average RAA is found to increase from about 0.15 in 0–5% central to a maximum value of about 0.8 in 75–85% peripheral collisions, beyond which i…
ϕ-Meson production at forward rapidity in p–Pb collisions at √sNN = 5.02 TeV and in pp collisions at √s = 2.76 TeV
2017
The first study of φ-meson production in p–Pb collisions at forward and backward rapidity, at a nucleon– nucleon centre-of-mass energy √sNN = 5.02 TeV, has been performed with the ALICE apparatus at the LHC. The φ-mesons have been identified in the dimuon decay channel in the transverse momentum (pT) range 1 < pT < 7 GeV/c, both in the p-going (2.03 < y < 3.53) and the Pb-going (−4.46 < y < −2.96) directions — where y stands for the rapidity in the nucleon–nucleon centre-of-mass — the integrated luminosity amounting to 5.01 ± 0.19 nb−1 and 5.81 ± 0.20 nb−1, respectively, for the two data samples. Differential cross sections as a function of transverse momentum and rapidity are presented. Th…