1,722,835 research outputs found
Elliptic flow: a brief review
No full textOne of the fundamental questions in the field of subatomic physics is the question of what happens to matter at extreme densities and temperatures as may have existed in the first microseconds after the Big Bang and exists, perhaps, in the core of dense neutron stars. The aim of heavy-ion physics is to collide nuclei at very high energies and thereby create such a state of matter in the laboratory. The experimental program began in the 1990s with collisions made available at the Brookhaven Alternating Gradient Synchrotron (AGS) and the CERN Super Proton Synchrotron (SPS), and continued at the Brookhaven Relativistic Heavy-Ion Collider (RHIC) with the maximum centerof- mass energies of p sNN = 4.75, 17.2 and 200 GeV, respectively. Collisions of heavy ions at the unprecedented energy of 2.76 TeV recently became available at the LHC collider at CERN. In this review, I give a brief introduction to the physics of ultrarelativistic heavy-ion collisions and discuss the current status of elliptic flow measurements
Erratum to: Production of π0 and η mesons up to high transverse momentum in pp collisions at 2.76 TeV: Erratum to: Eur. Phys. J. C (2017) 77:339DOI 10.1140/epjc/s10052-017-4890-x
No full textIn the original version of this article unfortunately the copyright holder in the PDF was wrong. The original article has been corrected
Neutral pion production at midrapidity in pp and Pb–Pb collisions at √ sNN TeV
No full textInvariant yields of neutral pions at midrapidity in the transverse momentum range (Formula presented.)c measured in Pb–Pb collisions at (Formula presented.) TeV are presented for six centrality classes. The pp reference spectrum was measured in the range (Formula presented.)c at the same center-of-mass energy. The nuclear modification factor, (Formula presented.), shows a suppression of neutral pions in central Pb–Pb collisions by a factor of up to about (Formula presented.) for (Formula presented.) ≲(Formula presented.)c. The presented measurements are compared with results at lower center-of-mass energies and with theoretical calculations
Suppression of ψ(2S) production in p-Pb collisions at √sNN = 5.02 TeV
No full textAbstract: The ALICE Collaboration has studied the inclusive production of the charmonium state ψ(2S) in proton-lead (p-Pb) collisions at the nucleon-nucleon centre of mass energy (formula presented.) = 5.02 TeV at the CERN LHC. The measurement was performed at forward (2.03 < ycms< 3.53) and backward (−4.46 < ycms< −2.96) centre of mass rapidities, studying the decays into muon pairs. In this paper, we present the inclusive production cross sections σψ(2S), both integrated and as a function of the transverse momentum pT, for the two ycms domains. The results are compared to those obtained for the 1S vector state (J/ψ), by showing the ratios between the production cross sections, as well as the double ratios [σψ(2S)/σJ/ψ ]pPb/[σψ(2S)/σJ/ψ]pp between p-Pb and proton-proton collisions. Finally, the nuclear modification factor for inclusive ψ(2S) is evaluated and compared to the measurement of the same quantity for J/ψ and to theoretical models including parton shadowing and coherent energy loss mechanisms. The results show a significantly larger suppression of the ψ(2S) compared to that measured for J/ψ and to models. These observations represent a clear indication for sizeable final state effects on ψ(2S) production.[Figure not available: see fulltext
Studying the relative bottom contribution via heavy-quark decay electron measurements in STAR
No full textWe report measurements of the azimuthal angular correlation distribution of heavy-quark decay electrons and open charmed mesons in pp collisions at GeV in the STAR experiment at RHIC. This measurement in combination with current theoretical model calculations allows to extract the relative bottom contribution to the heavy-quark decay electrons, which is important for the interpretation of the observed strong suppression of the high-p T electron yield in central Au+Au collisions
Measurement of D ± and D 0 production in deep inelastic scattering using a lifetime tag at HERA
No full textThe production of D ±- and D 0-mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb−1. The measurements cover the kinematic range
High-pT physics in sTAR
No full textRecent results of the STAR collaboration related to high transverse momentum phenomena are reviewed, which profit greatly from increased statistical reach from the large data sample collected in 2004 and improvement of particle identification at high pT . Dijet structures are observed even in central Au+Au collisions. At sufficiently high momentum a fragmentation pattern as in elementary collisions is observed, however the probability of observing a dijet partner hadron is strongly reduced. Beyond pT = 6 GeV/c all hadron species measured show a similar suppression. At lower pT interesting modifications are seen. A jet-correlated enhancement of long range in pseudorapidity is observed close to a trigger hadron. On the opposite side of the trigger a broad correlation structure is visible with an enhanced yield, which for certain kinematic conditions exhibits a double peak in central Au+Au collisions, whose origin is still under discussion. First results in d+Au collisions demonstrating the potential of photon physics in STAR are also presented
Heavy flavours
No full textThe XXII. InternationalWorkshop on Deep-Inelastic Scattering and Related Subjects (DIS 2014) was held in April 2014 in Warsaw, Poland. This contribution summarises some of the highlights on Heavy Flavours presented at this conference, focussing on recent results on ‘Charm and beauty production’, ‘Heavy quarks as a probe of hot and dense strongly interacting matter’, ‘Rare decays, Mixing and New Physics searches’ and ‘Spectroscopy and Quarkonia’
Measurement of azimuthal hadron asymmetries in semi-inclusive deep inelastic scattering off unpolarised nucleons
No full textSpin-averaged asymmetries in the azimuthal distributions of positive and negative hadrons produced in deep inelastic scattering were measured using the CERN SPS longitudinally polarised muon beam at 160GeV/c and a 6LiD target. The amplitudes of the three azimuthal modulations cos φh, cos 2φh and sin φh were obtained binning the data separately in each of the relevant kinematic variables x, z or pTh and binning in a three-dimensional grid of these three variables. The amplitudes of the cos φh and cos 2φh modulations show strong kinematic dependencies both for positive and negative hadrons
- …
