Search results for "Collisions."
showing 10 items of 533 documents
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…
Multi-strange baryon production at mid-rapidity in Pb-Pb collisions at root s(NN)=2.76 TeV
2014
The production of − and − baryons and their anti-particles in Pb–Pb collisions at √sNN = 2.76 TeV has been measured using the ALICE detector. The transverse momentum spectra at mid-rapidity (|y| < 0.5) for charged and hyperons have been studied in the range 0.6 < pT < 8.0 GeV/c and 1.2 < pT < 7.0 GeV/c, respectively, and in several centrality intervals (from the most central 0–10% to the most peripheral 60–80% collisions). These spectra have been compared with the predictions of recent hydrodynamic models. In particular, the Kraków and EPOS models give a satisfactory description of the data, with the latter covering a wider pT range. Mid-rapidity yields, integrated over pT, have been determ…
K∗(892)0 and ϕ(1020) production in Pb-Pb collisions at √sNN =2.76 TeV
2015
The yields of the K∗(892)0 and ϕ(1020) resonances are measured in Pb-Pb collisions at √sNN=2.76 TeV through their hadronic decays using the ALICE detector. The measurements are performed in multiple centrality intervals at mid-rapidity (|y|<0.5) in the transverse-momentum ranges 0.3<pT<5 GeV/c for the K∗(892)0 and 0.5<pT<5 GeV/c for the ϕ(1020). The yields of K∗(892)0 are suppressed in central Pb-Pb collisions with respect to pp and peripheral Pb-Pb collisions (perhaps due to rescattering of its decay products in the hadronic medium), while the longer-lived ϕ(1020) meson is not suppressed. These particles are also used as probes to study the mechanisms of particle production. The shape of t…
Mise en œuvre d’une architecture de gestion de collision pour le déploiement efficace d’un NoC sur multi-FPGA
2015
International audience; Le déploiement d’un NoC (Network On Chip) sur plusieurs FPGA nécessite que des routeurs partagent un même lien de communication entre FPGAs, créant des goulots d’étranglement [1]. Dans ce papier, nous proposons une structure de gestion de collision intégrée entre le NoC et le point d’accès du protocole FPGA. Cette structure est basée sur les algorithmes utilisés dans les réseaux informatiques et adaptée aux NoC [2].
Saturation and forward jets in proton-lead collisions at the LHC
2019
We investigate the forward-jet energy spectrum within the Color Glass Condensate framework at 5 TeV center-of-mass energy. In particular, we focus on the kinematic range covered by the CMS-CASTOR calorimeter. We show that our saturation-model calculations are compatible with the CASTOR measurements and that to optimally reproduce the data, effects of multi-parton interactions need to be included. We predict a significant nuclear suppression - reaching down to 50% at the lowest considered jet energies $E_{\rm jet} \sim 500 \, {\rm GeV}$.
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…
Investigations of Anisotropic Flow Using Multiparticle Azimuthal Correlations in pp, p-Pb, Xe-Xe, and Pb-Pb Collisions at the LHC
2019
Measurements of anisotropic flow coefficients ($v_n$) and their cross-correlations using two- and multi-particle cumulant methods are reported in collisions of pp at $\sqrt{s} = 13$ TeV, p-Pb at $\sqrt{s_{_{\rm NN}}} = 5.02$ TeV, Xe-Xe at $\sqrt{s_{_{\rm NN}}} = 5.44$ TeV, and Pb-Pb at $\sqrt{s_{_{\rm NN}}} = 5.02$ TeV recorded with the ALICE detector. The multiplicity dependence of $v_n$ is studied in a very wide range from 20 to 3000 particles produced in the mid-rapidity region $|��|<0.8$ for the transverse momentum range $0.2 < p_{\rm T} < 3.0$ GeV/$c$. An ordering of the coefficients $v_2 > v_3 > v_4$ is found in pp and p-Pb collisions, similar to that seen in large coll…
First measurement of quarkonium polarization in nuclear collisions at the LHC
2021
The polarization of inclusive J/$\psi$ and $\Upsilon(1{\rm S})$ produced in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV at the LHC is measured with the ALICE detector. The study is carried out by reconstructing the quarkonium through its decay to muon pairs in the rapidity region $2.5<y<4$ and measuring the polar and azimuthal angular distributions of the muons. The polarization parameters $\lambda_{\theta}$, $\lambda_{\phi}$ and $\lambda_{\theta\phi}$ are measured in the helicity and Collins-Soper reference frames, in the transverse momentum interval $2<p_{\rm T}<10$ GeV/$c$ and $p_{\rm T}<15$ GeV/$c$ for the J/$\psi$ and $\Upsilon(1{\rm S})$, respectively. The polarization parameter…
Inclusive cross section and double-helicity asymmetry for π0 production at midrapidity in p+p collisions at √s = 510 GeV
2016
PHENIX measurements are presented for the cross section and double-helicity asymmetry (ALL) in inclusive π0 production at midrapidity from p þ p collisions at ffiffi s p ¼ 510 GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantumchromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The π0ALL results follow an increasingly positive asymmetry trend with pT and ffiffi s p with respect to the predictions and are in ex…
Cross section and longitudinal single-spin asymmetry AL for forward W±→μ±ν production in polarized p+p collisions at √s = 510 GeV
2018
We have measured the cross section and single-spin asymmetries from forward W ± → μ ± ν production in longitudinally polarized p + p collisions at √ s = 510 GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the W bosons provides a natural flavor separation of the participating partons. peerReviewed