Search results for "p-Pb collisions"
showing 10 items of 20 documents
Jet-like correlations with neutral pion triggers in pp and central Pb–Pb collisions at 2.76 TeV
2016
We present measurements of two-particle correlations with neutral pion trigger particles of transverse momenta 8>pT trig>16 GeV/c and associated charged particles of 0.5>pT assoc>10 GeV/c versus the azimuthal angle difference Δφ at midrapidity in pp and central Pb–Pb collisions at √sNN=2.76 TeV with ALICE. The new measurements exploit associated charged hadrons down to 0.5 GeV/c, which significantly extends our previous measurement that only used charged hadrons above 3 GeV/c. After subtracting the contributions of the flow background, v2 to v5, the per-trigger yields are extracted for |Δφ|>0.7 on the near and for |Δφ−π|>1.1 on the away side. The ratio of per-trigger yields in Pb–Pb to thos…
Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
2014
Measurements of multi-particle azimuthal correlations (cumulants) for charged particles in p-Pb and Pb-Pb collisions are presented. They help address the question of whether there is evidence for global, flow-like, azimuthal correlations in the p-Pb system. Comparisons are made to measurements from the larger Pb-Pb system, where such evidence is established. In particular, the second harmonic two-particle cumulants are found to decrease with multiplicity, characteristic of a dominance of few-particle correlations in p-Pb collisions. However, when a $|\Delta \eta|$ gap is placed to suppress such correlations, the two-particle cumulants begin to rise at high-multiplicity, indicating the prese…
Isolated photon production in proton-nucleus collisions at forward rapidity
2018
We calculate isolated photon production at forward rapidities in proton-nucleus collisions in the Color Glass Condensate framework. Our calculation uses dipole cross sections solved from the running coupling Balitsky-Kovchegov equation with an initial condition fit to deep inelastic scattering data. For comparison, we also update the results for the nuclear modification factor for pion production in the same kinematics. We present predictions for future forward RHIC and LHC measurements at $\sqrt{s_{NN}}=200$ GeV and $\sqrt{s_{NN}}=8$ TeV.
Measurement of visible cross sections in proton-lead collisions at √sNN= 5.02 TeV in van der Meer scans with the ALICE detector
2014
In 2013, the Large Hadron Collider provided proton-lead and lead-proton collisions at the center-of-mass energy per nucleon pair $\sqrt{s_{\rm{NN}}}=5.02$ TeV. Van der Meer scans were performed for both configurations of colliding beams, and the cross section was measured for two reference processes, based on particle detection by the T0 and V0 detectors, with pseudo-rapidity coverage $4.6<\eta< 4.9$, $-3.3<\eta<-3.0$ and $2.8<\eta< 5.1$, $-3.7<\eta<-1.7$, respectively. Given the asymmetric detector acceptance, the cross section was measured separately for the two configurations. The measured visible cross sections are used to calculate the integrated luminosity of the proton-lead and lead-…
Multi-strange baryon production in p-Pb collisions at √sNN = 5.02 TeV
2016
The multi-strange baryon yields in Pb–Pb collisions have been shown to exhibit an enhancement relative to pp reactions. In this work, and production rates have been measured with the ALICE experiment as a function of transverse momentum, pT, in p–Pb collisions at a centre-of-mass energy of √sNN = 5.02 TeV. The results cover the kinematic ranges 0.6 GeV/c < pT < 7.2 GeV/c and 0.8 GeV/c < pT < 5 GeV/c, for and respectively, in the common rapidity interval −0.5 < yCMS < 0. Multi-strange baryons have been identified by reconstructing their weak decays into charged particles. The pT spectra are analysed as a function of event charged-particle multiplicity, which in p–Pb collisions ranges over on…
Centrality dependence of particle production in p−Pb collisions at √sNN = 5.02 TeV
2015
We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at √sNN = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (Npart) or the number of nucleon-nucleon binary collisions (Ncoll) are described. We show that, in contrast to Pb-Pb coll…
Jet-like correlations with neutral pion triggers in pp and central Pb–Pb collisions at 2.76 TeV
2016
Physics letters / B B763, 238 - 250 (2016). doi:10.1016/j.physletb.2016.10.048
D-meson production in p-Pb collisions at √sNN = 5.02 TeV and in pp collisions at √s = 7 TeV
2016
Background: In the context of the investigation of the quark gluon plasma produced in heavy-ion collisions, hadrons containing heavy (charm or beauty) quarks play a special role for the characterization of the hot and dense medium created in the interaction. The measurement of the production of charm and beauty hadrons in proton– proton collisions, besides providing the necessary reference for the studies in heavy-ion reactions, constitutes an important test of perturbative quantum chromodynamics (pQCD) calculations. Heavy-flavor production in proton–nucleus collisions is sensitive to the various effects related to the presence of nuclei in the colliding system, commonly denoted cold-nuclea…
Production of Σ(1385)± and Ξ(1530)0 in p–Pb collisions at √sNN = 5.02 TeV
2017
The transverse momentum distributions of the strange and double-strange hyperon resonances ((1385)±, (1530)0) produced in p–Pb collisions at √sNN = 5.02 TeV were measured in the rapidity range −0.5 < yCMS < 0 for event classes corresponding to different charged-particle multiplicity densities, dNch/dηlab . The mean transverse momentum values are presented as a function ofdNch/dηlab , as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of dNch/dηlab . The equivalent ratios to pions exhibit an increase with dNch/dηlab , depending on their strangeness co…
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…