| 251. |
- Adam, J., et al.
(författare)
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Insight into particle production mechanisms via angular correlations of identified particles in pp collisions at √s=7 TeV
- 2017
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:8
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Tidskriftsartikel (refereegranskat)abstract
- Two-particle angular correlations were measured in pp collisions at s=7 TeV for pions, kaons, protons, and lambdas, for all particle/anti-particle combinations in the pair. Data for mesons exhibit an expected peak dominated by effects associated with mini-jets and are well reproduced by general purpose Monte Carlo generators. However, for baryon–baryon and anti-baryon–anti-baryon pairs, where both particles have the same baryon number, a near-side anti-correlation structure is observed instead of a peak. This effect is interpreted in the context of baryon production mechanisms in the fragmentation process. It currently presents a challenge to Monte Carlo models and its origin remains an open question. © 2017, CERN for the benefit of the ALICE collaboration.
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| 252. |
- Adam, J., et al.
(författare)
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J/ψ suppression at forward rapidity in Pb–Pb collisions at sNN=5.02 TeV
- 2017
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 766, s. 212-224
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Tidskriftsartikel (refereegranskat)abstract
- The inclusive J/ψ production has been studied in Pb–Pb and pp collisions at the centre-of-mass energy per nucleon pair sNN=5.02 TeV, using the ALICE detector at the CERN LHC. The J/ψ meson is reconstructed, in the centre-of-mass rapidity interval 2.5>y<4 and in the transverse-momentum range pT<12 GeV/c, via its decay to a muon pair. In this Letter, we present results on the inclusive J/ψ cross section in pp collisions at s=5.02 TeV and on the nuclear modification factor RAA. The latter is presented as a function of the centrality of the collision and, for central collisions, as a function of the transverse momentum pT of the J/ψ. The measured RAA values indicate a suppression of the J/ψ in nuclear collisions and are then compared to our previous results obtained in Pb–Pb collisions at sNN=2.76 TeV. The ratio of the RAA values at the two energies is also computed and compared to calculations of statistical and dynamical models. The numerical value of the ratio for central events (0–10% centrality) is 1.17±0.04(stat)±0.20(syst). In central events, as a function of pT, a slight increase of RAA with collision energy is visible in the region 2
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| 253. |
- Adam, J., et al.
(författare)
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Jet-like correlations with neutral pion triggers in pp and central Pb–Pb collisions at 2.76 TeV
- 2016
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 763, s. 238-250
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Tidskriftsartikel (refereegranskat)abstract
- 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 those in pp collisions, IAA, is measured on the near and away side for the 0–10% most central Pb–Pb collisions. On the away side, the per-trigger yields in Pb–Pb are strongly suppressed to the level of IAA≈0.6 for pT assoc<3 GeV/c, while with decreasing momenta an enhancement develops reaching about 5 at low pT assoc. On the near side, an enhancement of IAA between 1.2 at the highest to 1.8 at the lowest pT assoc is observed. The data are compared to parton-energy-loss predictions of the JEWEL and AMPT event generators, as well as to a perturbative QCD calculation with medium-modified fragmentation functions. All calculations qualitatively describe the away-side suppression at high pT assoc. Only AMPT captures the enhancement at low pT assoc, both on the near and away side. However, it also underpredicts IAA above 5 GeV/c, in particular on the near-side. © 2016 The Author(s)
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| 254. |
- Adam, J., et al.
(författare)
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K∗(892)0 and φ(1020) meson production at high transverse momentum in pp and Pb-Pb collisions at s NN =2.76 TeV
- 2017
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Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 95:6
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Tidskriftsartikel (refereegranskat)abstract
- The production of K∗(892)0 and φ(1020) mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at sNN=2.76TeV has been analyzed using a high luminosity data sample accumulated in 2011 with the ALICE detector at the Large Hadron Collider (LHC). Transverse momentum (pT) spectra have been measured for K∗(892)0 and φ(1020) mesons via their hadronic decay channels for pT up to 20GeV/c. The measurements in pp collisions have been compared to model calculations and used to determine the nuclear modification factor and particle ratios. The K∗(892)0/K ratio exhibits significant reduction from pp to central Pb-Pb collisions, consistent with the suppression of the K∗(892)0 yield at low pT due to rescattering of its decay products in the hadronic phase. In central Pb-Pb collisions the pT dependent φ(1020)/π and K∗(892)0/π ratios show an enhancement over pp collisions for pT≈3GeV/c, consistent with previous observations of strong radial flow. At high pT, particle ratios in Pb-Pb collisions are similar to those measured in pp collisions. In central Pb-Pb collisions, the production of K∗(892)0 and φ(1020) mesons is suppressed for pT>8GeV/c. This suppression is similar to that of charged pions, kaons, and protons, indicating that the suppression does not depend on particle mass or flavor in the light quark sector. © 2017 CERN.
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| 255. |
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| 256. |
- Adam, J., et al.
(författare)
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Measurement of azimuthal correlations of D mesons with charged particles in pp collisions at √s=7 TeV and p–Pb collisions at √sNN=5.02 TeV
- 2017
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:4
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Tidskriftsartikel (refereegranskat)abstract
- The azimuthal correlations of D mesons with charged particles were measured with the ALICE apparatus in pp collisions at s=7TeV and p–Pb collisions at sNN=5.02TeV at the Large Hadron Collider. D 0, D +, and D ∗ + mesons and their charge conjugates with transverse momentum 30.3GeV/c. The yield of charged particles in the correlation peak induced by the jet containing the D meson and the peak width are compatible within uncertainties in the two collision systems. The data are described within uncertainties by Monte-Carlo simulations based on PYTHIA, POWHEG, and EPOS 3 event generators. © 2017, CERN for the benefit of the ALICE collaboration.
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| 257. |
- Adam, J., et al.
(författare)
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Measurement of charged jet production cross sections and nuclear modification in p-Pb collisions at root s(NN)=5.02 TeV
- 2015
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 749, s. 68-81
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Tidskriftsartikel (refereegranskat)abstract
- Charged jet production cross sections in p-Pb collisions at root s(NN) = 5.02 TeV measured with the ALICE detector at the LHC are presented. Using the anti-k(T) algorithm, jets have been reconstructed in the central rapidity region from charged particles with resolution parameters R = 0.2 and R = 0.4. The reconstructed jets have been corrected for detector effects and the underlying event background. To calculate the nuclear modification factor, R-pPb, of charged jets in p-Pb collisions, a pp reference was constructed by scaling previously measured charged jet spectra at root s = 7 TeV. In the transverse momentum range 20 <= p(T, chjet) <= 120 GeV/c, R-pPb is found to be consistent with unity, indicating the absence of strong nuclear matter effects on jet production. Major modifications to the radial jet structure are probed via the ratio of jet production cross sections reconstructed with the two different resolution parameters. This ratio is found to be similar to the measurement in pp collisions at root s = 7 TeV and to the expectations from PYTHIA pp simulations and NLO pQCD calculations at root s(NN) = 5.02 TeV. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.
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| 258. |
- Adam, J., et al.
(författare)
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Measurement of charm and beauty production at central rapidity versus charged-particle multiplicity in proton-proton collisions at root s=7 TeV
- 2015
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- Prompt D meson and non-prompt J/psi yields are studied as a function of the multiplicity of charged particles produced in inelastic proton-proton collisions at a centre-of-mass energy of root s = 7 TeV. The results are reported as a ratio between yields in a given multiplicity interval normalised to the multiplicity-integrated ones (relative yields). They are shown as a function of the multiplicity of charged particles normalised to the average value for inelastic collisions (relative charged-particle multiplicity). D-0, D+ and D*+ mesons are measured in five p(T) intervals from 1 GeV/c to 20 GeV/c and for |y| < 0.5 via their hadronic decays. The D-meson relative yield is found to increase with increasing charged-particle multiplicity. For events with multiplicity six times higher than the average multiplicity of inelastic collisions, a yield enhancement of a factor about 15 relative to the multiplicity-integrated yield in inelastic collisions is observed. The yield enhancement is independent of transverse momentum within the uncertainties of the measurement. The D-0-meson relative yield is also measured as a function of the relative multiplicity at forward pseudo-rapidity. The non-prompt J/psi, i.e. the B hadron, contribution to the inclusive J/psi production is measured in the di-electron decay channel at central rapidity. It is evaluated for p(T) > 1.3 GeV/c and |y| < 0.9, and extrapolated to p(T) > 0. The fraction of non-prompt J/psi the inclusive J/psi yields shows no dependence on the charged-particle multiplicity at central rapidity. Charm and beauty hadron relative yields exhibit a similar increase with increasing charged-particle multiplicity. The measurements are compared to PYTHIA 8, EPOS 3 and percolation calculations.
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| 259. |
- Adam, J., et al.
(författare)
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Measurement of D-meson production versus multiplicity in p-Pb collisions at √sNN=5.02 TeV
- 2016
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2016:8
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of prompt D-meson production as a function of multiplicity in p-Pb collisions at sNN=5.02 TeV with the ALICE detector at the LHC is reported. D0, D+ and D∗+ mesons are reconstructed via their hadronic decay channels in the centre-of-mass rapidity range −0.96 < ycms< 0.04 and transverse momentum interval 1
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| 260. |
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