The inclusive transverse momentum (p T) distributions of primary charged particles are measured in the pseudo-rapidity range | IDT | 30 GeV / c . In peripheral collisions (70a80%), only moderate ...suppression (R A A = 0.6 a 0.7) and a weak p T dependence is observed. The measured nuclear modification factors are compared to other measurements and model calculations.
The elliptic, v 2 , triangular, v 3 , and quadrangular, v 4 , azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions, and (anti-)protons in PbaPb collisions at ...s NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range | IDT | 8 GeV / c . The small p T dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to p T = 8 GeV / c . The magnitude of the (anti-)proton elliptic and triangular flow is larger than that of pions out to at least p T = 8 GeV / c indicating that the particle type dependence persists out to high p T .
The ALICE Collaboration has measured inclusive J / I production in pp collisions at a center-of-mass energy s = 2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges ...| y | < 0.9 and 2.5 < y < 4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L int e = 1.1 nb - 1 and L int mu = 19.9 nb - 1 , and the corresponding signal statistics are N J / I e + e - = 59 +/- 14 and N J / I mu + mu - = 1364 +/- 53 . We present d I J / I / d y for the two rapidity regions under study and, for the forward-y range, d 2 I J / I / d y d p t in the transverse momentum domain 0 < p t < 8 GeV / c . The results are compared with previously published results at s = 7 TeV and with theoretical calculations.
The p T -differential inclusive production cross section of the prompt charm-strange meson D s + in the rapidity range | y | < 0.5 was measured in protonaproton collisions at s = 7 TeV at the LHC ...using the ALICE detector. The analysis was performed on a data sample of 2.98 X 10 8 events collected with a minimum-bias trigger. The corresponding integrated luminosity is L int = 4.8 nb - 1 . Reconstructing the decay D s + a I pi + , with I a K - K + , and its charge conjugate, about 480 D s +/- mesons were counted, after selection cuts, in the transverse momentum range 2 < p T < 12 GeV / c . The results are compared with predictions from models based on perturbative QCD. The ratios of the cross sections of four D meson species (namely D 0 , D + , D a + and D s +) were determined both as a function of p T and integrated over p T after extrapolating to full p T range, together with the strangeness suppression factor in charm fragmentation. The obtained values are found to be compatible within uncertainties with those measured by other experiments in e + e - , ep and pp interactions at various centre-of-mass energies.
AbstractThe ALICE TOF array will be built using the Multigap Resistive Plate Chamber(MRPC) configured as a double stack. Each stack contains 5 gas gaps with width of 250 μm. There has been an intense ...R&D effort to optimise this new detector to withstand the problems connected with the high level of radiation at the LHC. One clear outcome of the R&D is that the growth of the gas avalanche is strongly affected by space charge. The effect of the space charge is a decrease in the rate of change in gain with electric field; this allows more stable operation of this detector. We have measured the gain as a function of the electric field and also measured the ratio of the fast charge to the total charge produced in the gas gap. It is well established that RPCs built with 250 μm gas gap have a much superior performance than 2 mm gaps; we discuss and compare the performance of 250 μm gap MRPCs with 2 mm gap RPCs to show the importance of space-charge limitation of avalanche growth.PACS: 29.40.Cs – 7.77.-n – 52.80.Dy
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 correlations in pp, p–Pb and Pb–Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p–Pb collisions are found to be 5–15% larger than those in pp, while those in Pb–Pb are 35–55% larger than those in p–Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p–Pb as compared to pp collisions at similar multiplicity.
A measurement of the multi-strange I a and ICO a baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic protonaproton collisions at ...a centre-of-mass energy of 7 TeV. The transverse momentum ( p T ) distributions were studied at mid-rapidity ( | y | 6.0 GeV / c . We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of ( ICO a + ICO A= + ) / ( I a + I A= + ) as a function of transverse mass.
The ALICE Collaboration reports the measurement of the relative J / I yield as a function of charged particle pseudorapidity density d N ch / d IDT in pp collisions at s = 7 TeV at the LHC. J / I ...particles are detected for p t > 0 , in the rapidity interval | y | 0 . In the highest multiplicity interval with a d N ch / d IDT ( bin ) a = 24.1 , corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J / I yield by a factor of about 5 at 2.5 < y < 4 (8 at | y | < 0.9 ) is observed.
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb collisions at inline image at the Large Hadron Collider is presented. We observe a growing trend with energy now not only ...for the longitudinal and the outward but also for the sideward pion source radius. The pion homogeneity volume and the decoupling time are significantly larger than those measured at RHIC.
PDF
