Papers by Евгений Мартынов
Journal of High Energy Physics, 2016
The production of J/ψ and ψ(2S) was studied with the ALICE detector in Pb-Pb collisions at the LH... more The production of J/ψ and ψ(2S) was studied with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity (2.5 < y < 4) down to zero transverse momentum (p t ) in the dimuon decay channel. Inclusive J/ψ yields were extracted in different centrality classes and the centrality dependence of the average p t is presented. The J/ψ suppression, quantified with the nuclear modification factor (R AA ), was measured as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower collision energy and theoretical models indicate that the J/ψ production is the result of an interplay between color screening and recombination mechanisms in a deconfined partonic medium, or at its hadronization. Results on the ψ(2S) suppression are provided via the ratio of ψ(2S) over J/ψ measured in pp and Pb-Pb collisions.
The ALICE collaboration at the LHC reports measurement of the inclusive production cross section ... more The ALICE collaboration at the LHC reports measurement of the inclusive production cross section of electrons from semi-leptonic decays of beauty hadrons with rapidity |y| < 0.8 and transverse momentum 1 < p T < 10 GeV/c, in pp collisions at √ s = 2.76 TeV. Electrons not originating from semielectronic decay of beauty hadrons are suppressed using the impact parameter of the corresponding tracks. The production cross section of beauty decay electrons is compared to the result obtained with an alternative method which uses the distribution of the azimuthal angle between heavy-flavour decay electrons and charged hadrons. Perturbative QCD predictions agree with the measured cross section within the experimental and theoretical uncertainties. The integrated visible cross section, σ b→e = 3.47 ± 0.40(stat) +1.12 -1.33 (sys) ± 0.07(norm) µb, was extrapolated to full phase space using Fixed Order plus Next-to-Leading Log (FONLL) calculations to obtain the total b b production cross section, σ b b = 130 ± 15.1(stat) +42.1 -49.8 (sys) +3.4 -3.1 (extr) ± 2.5(norm) ± 4.4(BR) µb.
Physics Letters B, 2014
Transverse momentum spectra of π ± , K ± and p(p) up to p T = 20 GeV/c at mid-rapidity in pp, per... more Transverse momentum spectra of π ± , K ± and p(p) up to p T = 20 GeV/c at mid-rapidity in pp, peripheral (60-80%) and central (0-5%) Pb-Pb collisions at √ s NN = 2.76 TeV have been measured using the ALICE detector at the Large Hadron Collider. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at p T ≈ 3 GeV/c in central Pb-Pb collisions. Below the peak, p T < 3 GeV/c, both ratios are in good agreement with hydrodynamical calculations, suggesting that the peak itself is dominantly the result of radial flow rather than anomalous hadronization processes. For p T > 10 GeV/c particle ratios in pp and Pb-Pb collisions are in agreement and the nuclear modification factors for π ± , K ± and p(p) indicate that, within the systematic and statistical uncertainties, the suppression is the same. This suggests that the chemical composition of leading particles from jets in the medium is similar to that of vacuum jets.
Journal of High Energy Physics, 2012
The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at $ ... more The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at $ \sqrt{s}=7 $ TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5.6 nb−1. The fraction of J/ψ from the decay of long-lived beauty hadrons was determined for J/ψ candidates with transverse momentum p t > 1.3 GeV/c and rapidity |y| < 0.9. The cross section for prompt J/ψ mesons, i.e. directly produced J/ψ and prompt decays of heavier charmonium states such as the ψ(2S) and χc resonances, is σprompt J/ψ (p t > 1.3 GeV/c, |y| < 0.9) = 8.3 ± 0.8 (stat.) ± 1.1 (syst.) $ _{-1.4}^{+1.5 } $ (syst. pol.) μb. The cross section for the production of b-hadrons decaying to J/ψ with p t > 1.3 GeV/c and |y| < 0.9 is $ {\sigma_{{{J \left/ {{\psi \leftarrow {{\mathrm{h}}_{\mathrm{B}}}}} \right.}}}} $ (p t > 1.3 GeV/c, |y| < 0.9) = 1.46 ± 0.38 (stat.) $ _{-0.32}^{+0.26 } $ (syst.) μb. The results are compared to QCD model predictio...
Journal of High Energy Physics, 2013
We present the measurements of particle pair yields per trigger particle obtained from di-hadron ... more We present the measurements of particle pair yields per trigger particle obtained from di-hadron azimuthal correlations in pp collisions at $ \sqrt{s} $ = 0.9, 2.76, and 7 TeV recorded with the ALICE detector. The yields are studied as a function of the charged particle multiplicity. Taken together with the single particle yields the pair yields provide information about parton fragmentation at low transverse momenta, as well as on the contribution of multiple parton interactions to particle production. Data are compared to calculations using the PYTHIA6, PYTHIA8, and PHOJET event generators.
Physics Letters B, 2012
A measurement of the multi-strange Ξ -and Ω -baryons and their antiparticles by the ALICE experim... more A measurement of the multi-strange Ξ -and Ω -baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for proton-proton collisions at centre of mass energy of 7 TeV. The transverse momentum (p t ) distributions were studied at mid-rapidity (|y| < 0.5) in the range of 0.6 < p t < 8.5 GeV/c for Ξ -and Ξ + baryons, and in the range of 0.8 < p t < 5 GeV/c for Ω -and Ω + . Baryons and anti-baryons were measured as separate particles and we find that the baryon to antibaryon ratio of both particle species is consistent with unity over the entire range of the measurement. The statistical precision of the current LHC data has allowed us to measure a difference between the mean p t of Ξ -(Ξ + ) and Ω -(Ω + ). Particle yields, mean p t , and the spectra in the intermediate p t range are not well described by the PYTHIA Perugia 2011 tune Monte Carlo event generator, which has been tuned to reproduce the early LHC data. The discrepancy is largest for Ω -(Ω + ). This PYTHIA tune approaches the p t spectra of Ξ -and Ξ + baryons below p t < 0.85 GeV/c and describes the Ξ -and Ξ + spectra above p t > 6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Ω -+Ω + )/ (Ξ -+Ξ + ) as a function of transverse mass.
Light vector meson production in pp collisions at s=7 TeV
Physics Letters B, 2012
ABSTRACT The ALICE experiment has measured low-mass dimuon production in pp collisions at root s ... more ABSTRACT The ALICE experiment has measured low-mass dimuon production in pp collisions at root s = 7 TeV in the dimuon rapidity region 2.5 &amp;lt; y &amp;lt; 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (eta, rho, omega, eta&amp;#39;, phi) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for omega and phi are sigma(omega)(1 &amp;lt; p(t) &amp;lt; 5 GeV/c. 2.5 &amp;lt; y &amp;lt; 4) = 5.28 +/- 0.54(stat) +/- 0.49(syst) mb and sigma(phi)(1 &amp;lt; p(t) &amp;lt; 5 GeV/c. 2.5 &amp;lt; y &amp;lt; 4) = 0.940 +/- 0.084(stat) +/- 0.076(syst) mb. The differential cross sections d(2)sigma/dy dp(t) are extracted as a function of p(t) for omega and phi. The ratio between the rho and omega cross section is obtained. Results for the phi are compared with other measurements at the same energy and with predictions by models. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
Physical Review Letters, 2012
Physical Review Letters, 2013
Physical Review Letters, 2012
The yield of charged particles associated with high-p t trigger particles (8 < p t < 15 GeV=c) is... more The yield of charged particles associated with high-p t trigger particles (8 < p t < 15 GeV=c) is measured with the ALICE detector in Pb-Pb collisions at ffiffiffiffiffiffiffiffi s NN p ¼ 2:76 TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jetlike correlation peaks in azimuthal dihadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta p t > 3 GeV=c on the away side drops to about 60% of that observed in pp collisions, while on the near side a moderate enhancement of 20%-30% is found.
Physical Review Letters, 2012
The ALICE Collaboration has studied J=c production in pp collisions at ffiffi ffi s p ¼ 7 TeV at ... more The ALICE Collaboration has studied J=c production in pp collisions at ffiffi ffi s p ¼ 7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J=c polarization parameters and were obtained. The study was performed in the kinematic region 2:5 < y < 4, 2 < p t < 8 GeV=c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.
Physical Review Letters, 2013
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Physical Review E, 2013
We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capil... more We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.
The European Physical Journal C, 2013
Differential cross sections of charged particles in inelastic pp collisions as a function of p T ... more Differential cross sections of charged particles in inelastic pp collisions as a function of p T have been measured at √ s = 0.9, 2.76 and 7 TeV at the LHC. The p T spectra are compared to NLO-pQCD calculations. Though the differential cross section for an individual √ s cannot be described by NLO-pQCD, the relative increase of cross section with √ s is in agreement with NLO-pQCD. Based on these measurements and observations, procedures are discussed to construct pp reference spectra at √ s = 2.76 and 5.02 TeV up to p T = 50 GeV/c as required for the calculation of the nuclear modification factor in nucleus-nucleus and protonnucleus collisions.
Physical Review Letters, 2012
Centrality dependence of high-$p_{\rm T}$ D meson suppression in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV
The nuclear modification factor, $R_{\rm AA}$, of the prompt charmed mesons ${\rm D^0}$, ${\rm D^... more The nuclear modification factor, $R_{\rm AA}$, of the prompt charmed mesons ${\rm D^0}$, ${\rm D^+}$ and ${\rm D^{*+}}$, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy $\sqrt{s_{\rm NN}} = 2.76$ TeV in two transverse momentum intervals, $5<p_{\rm T}<8$ GeV/$c$ and $8<p_{\rm T}<16$ GeV/$c$, and in six collision centrality classes. The $R_{\rm AA}$ shows a maximum suppression of a factor of 5-6 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the $R_{\rm AA}$ of non-prompt ${\rm J}/\psi$ from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions
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Papers by Евгений Мартынов