The transverse momentum (p T) distribution of primary charged particles is measured at midrapidity in minimum-bias p–Pb collisions at √ s NN = 5.02 TeV with the ALICE detector at the LHC in the range ...0.15 < p T < 50 GeV/c. The spectra are compared to the expectation based on binary collision scaling of particle production in pp colli-sions, leading to a nuclear modification factor consistent with unity for p T larger than 2 GeV/c, with a weak indication of a Cronin-like enhancement for p T around 4 GeV/c. The mea-surement is compared to theoretical calculations and to data in Pb–Pb collisions at √ s NN = 2.76 TeV. Measurements of particle production in proton-nucleus colli-sions at high energies enable the study of fundamental proper-ties of Quantum Chromodynamics (QCD) over a broad range of parton fractional momentum x and parton densities (see 1 for a review). They also provide reference measurements for the studies of deconfined matter created in nucleus–nucleus collisions 2. The first measurements of charged-particle production in minimum-bias p–Pb collisions at the LHC at a centre-of-mass energy per nucleon-nucleon pair of √ s NN = 5.02 TeV
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The NA50 segmented target and vertex recognition system Bellaiche, F.; Cheynis, B.; Contardo, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/1997, Letnik:
398, Številka:
2
Journal Article
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The NA50 segmented target and vertex recognition system is described. The segmented target consists of 7 sub-targets of 1–2 mm thickness. The vertex recognition system used to determine the ...sub-target where an interaction has occured is based upon quartz elements which produce Čerenkov light when traversed by charged particles from the interaction. The geometrical arrangement of the quartz elements has been optimized for vertex recognition in
208PbPb collisions at 158 GeV/nucleon. A simple algorithm provides a vertex recognition efficiency of better than 85% for dimuon trigger events collected with a 1 mm sub-target set-up. A method for recognizing interactions of projectile fragments (nuclei and/or groups of nucleons) is presented. The segmented target allows a large target thickness which together with a high beam intensity (≈ 10
7 ions/s) enables high statistics measurements.
The ALICE measurement of K^0_S and {\Lambda} production at mid-rapidity in Pb-Pb collisions at sqrt(sNN) = 2.76 TeV is presented. The transverse momentum (pT) spectra are shown for several collision ...centrality intervals and in the pT range from 0.4 GeV/c (0.6 GeV/c for {\Lambda}) to 12 GeV/c. The pT dependence of the {\Lambda}/K^0_S ratios exhibits maxima in the vicinity of 3 GeV/c, and the positions of the maxima shift towards higher pT with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb-Pb collisions. This baryon excess at intermediate pT is not observed in pp interactions at sqrt(s) = 0.9 TeV and at sqrt(s) = 7 TeV. Qualitatively, the baryon enhancement in heavy-ion collisions is expected from radial flow. However, the measured pT spectra above 2 GeV/c progressively decouple from hydrodynamical-model calculations. For higher values of pT, models that incorporate the influence of the medium on the fragmentation and hadronization processes describe qualitatively the pT dependence of the {\Lambda}/K^0_S ratio.
The production of vector mesons φ, ρ and ω has been measured in Pb–Pb collisions at 158 GeV/c per nucleon incident momentum at the CERN/SPS. The muon spectrometer of experiment NA50 detects φ, ρ and ...ω mesons via their μ+μ− decay channel in the collision center of mass rapidity range 0⩽yCM⩽1. The results reported here show that the relative production of the φ compared to the (ρ+ω) and the φ multiplicity per participant nucleon (Npart) increase with the centrality of the collision. On the other hand, the (ρ+ω) multiplicity per participant does not exhibit any Npart dependence within our errors. The inverse slope parameter as deduced from an exponential fit to the φ transverse mass distribution is 228±10 MeV. Our results are compared with those obtained by experiment NA49 and with theoretical calculations.
Azimuthally anisotropic distributions of D0, D+ and D*+ mesons were studied in the central rapidity region (|y|<0.8) in Pb-Pb collisions at a centre-of-mass energy sqrts(s_NN) = 2.76TeV per ...nucleon-nucleon collision, with the ALICE detector at the LHC. The second Fourier coefficient v2 (commonly denoted elliptic flow) was measured in the centrality class 30-50% as a function of the D meson transverse momentum pt, in the range 2-16GeV/c$. The measured v2 of D mesons is comparable in magnitude to that of light-flavour hadrons. It is positive in the range 2 < pt < 6 GeV/c with 5.7 sigma significance, based on the combination of statistical and systematic uncertainties.
Ψ′ and J/Ψ yields are compared in p-W, p-U and S-U interactions at 200 GeV/nucleon. Their ratio decreases from proton-t to sulphur-induced reactions. It also decreases in sulphur-induced reactions ...from peripheral to central collisions. This result could indicate that the Ψ′ and J/Ψ suppression mechanisms have different origins in p- and S-induced reactions.
We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at \surd s_NN 2.76 TeV, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical ...fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudo-rapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the ALICE data points are between the theoretically predicted values for a hadron gas and a Quark-Gluon Plasma.
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