| 1. |
- Abelev, B., et al.
(author)
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Charge correlations using the balance function in Pb-Pb collisions at root s(NN)=2.76 TeV
- 2013
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In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 723:4-5, s. 267-279
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Journal article (peer-reviewed)abstract
- In high-energy heavy-ion collisions, the correlations between the emitted particles can be used as a probe to gain insight into the charge creation mechanisms. In this Letter, we report the first results of such studies using the electric charge balance function in the relative pseudorapidity (Delta eta) and azimuthal angle (Delta phi) in Pb-Pb collisions at root s(NN) = 2.76 TeV with the ALICE detector at the Large Hadron Collider. The width of the balance function decreases with growing centrality (i.e. for more central collisions) in both projections. This centrality dependence is not reproduced by HIJING, while AMPT, a model which incorporates strings and parton rescattering, exhibits qualitative agreement with the measured correlations in Delta phi but fails to describe the correlations in Delta eta. A thermal blast-wave model incorporating local charge conservation and tuned to describe the p(T) spectra and v(2) measurements reported by ALICE, is used to fit the centrality dependence of the width of the balance function and to extract the average separation of balancing charges at freeze-out. The comparison of our results with measurements at lower energies reveals an ordering with root s(NN): the balance functions become narrower with increasing energy for all centralities. This is consistent with the effect of larger radial flow at the LHC energies but also with the late stage creation scenario of balancing charges. However, the relative decrease of the balance function widths in Delta eta and Delta phi, with centrality from the highest SPS to the LHC energy exhibits only small differences. This observation cannot be interpreted solely within the framework where the majority of the charge is produced at a later stage in the evolution of the heavy-ion collision. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 2. |
- Abelev, B., et al.
(author)
-
D-S(+) meson production at central rapidity in proton-proton collisions at root s=7 TeV
- 2012
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 718:2, s. 279-294
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Journal article (peer-reviewed)abstract
- The P-T-differential inclusive production cross section of the prompt charm-strange meson D-s(+) in the rapidity range vertical bar y vertical bar < 0.5 was measured in proton-proton collisions at root s = 7 TeV at the LHC using the ALICE detector. The analysis was performed on a data sample of 2.98 x 10(8) events collected with a minimum-bias trigger. The corresponding integrated luminosity is L-int = 4.8 nb(-1). Reconstructing the decay D-s(+) -> phi pi(+) with phi -> K-K+, and its charge conjugate, about 480 D-s(+/-) mesons were counted, after selection cuts, in the transverse momentum range 2 < P-T < 12 GeV/c. The results are compared with predictions from models based on perturbative QCD. The ratios of the cross sections of four D meson species (namely D-0, D+, D*+ and D-s(+)) were determined both as a function of p(T) and integrated over p(T)after extrapolating to full p(T) range, together with the strangeness suppression factor in charm fragmentation. The obtained values are found to be compatible within uncertainties with those measured by other experiments in e(+)e(-), ep and pp interactions at various centre-of-mass energies. (C) 2012 CERN. Published by Elsevier By. All rights reserved.
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| 3. |
- Abelev, B., et al.
(author)
-
Multiplicity dependence of the average transverse momentum in pp, p-Pb, and Pb-Pb collisions at the LHC
- 2013
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 727:4-5, s. 371-380
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Journal article (peer-reviewed)abstract
- The average transverse momentum (p(T)) versus the charged-particle multiplicity N-ch was measured in p-Pb collisions at a collision energy per nucleon-nucleon root S-NN = 5.02 TeV and in pp collisions at collision energies of root s = 0.9, 2.76, and 7 TeV in the kinematic range 0.15 < p(T) < 10.0 GeV/c and vertical bar eta vertical bar < 0.3 with the ALICE apparatus at the LHC. These data are compared to results in Pb-Pb collisions at root S-NN = 2.76 TeV at similar charged-particle multiplicities. In pp and p-Pb collisions, a strong increase of (p(T)) with N-ch is observed, which is much stronger than that measured in Pb-Pb collisions. For pp collisions, this could be attributed, within a model of hadronizing strings, to multiple-parton interactions and to a final-state color reconnection mechanism. The data in p-Pb and Pb-Pb collisions cannot be described by an incoherent superposition of nucleon-nucleon collisions and pose a challenge to most of the event generators. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 4. |
- Abelev, B., et al.
(author)
-
Multiplicity dependence of pion, kaon, proton and lambda production in p-Pb collisions at root s(NN)=5.02 TeV
- 2014
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In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 728, s. 25-38
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Journal article (peer-reviewed)abstract
- In this Letter, comprehensive results on pi(+/-), K-+/-, K-S(0), p((p) over bar) and A((A) over bar) production at mid-rapidity (0 < y(CMS) < 0.5) in p-Pb collisions at root s(NN) = 5.02 TeV, measured by the ALICE detector at the LHC, are reported. The transverse momentum distributions exhibit a hardening as a function of event multiplicity, which is stronger for heavier particles. This behavior is similar to what has been observed in pp and Pb-Pb collisions at the LHC. The measured pr distributions are compared to d-Au, Au-Au and Pb-Pb results at lower energy and with predictions based on QCD-inspired and hydrodynamic models. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
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| 5. |
- Abelev, B., et al.
(author)
-
Neutral pion and eta meson production in proton-proton collisions at root s=0.9 TeV and root s=7 TeV
- 2012
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 717:1-3, s. 162-172
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Journal article (peer-reviewed)abstract
- The first measurements of the invariant differential cross sections of inclusive pi(0) and eta meson production at mid-rapidity in proton-proton collisions root s = 0.9 TeV and root s = 7 TeV are reported. The pi(0) measurement covers the ranges 0.4 < p(T) < 7 GeV/c and 0.3 < p(T) < 25 GeV/c for these two energies, respectively. The production of eta mesons was measured at root s = 7 TeV in the range 0.4 < p(T) < 15 GeV/c. Next-to-Leading Order perturbative QCD calculations, which are consistent with the pi(0) spectrum at root s = 0.9 TeV, overestimate those of pi(0) and eta mesons at root s = 7 TeV, but agree with the measured eta/pi(0) ratio at root s = 7 TeV. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 6. |
- Abelev, B., et al.
(author)
-
Inclusive J/psi production in pp collisions at root s=2.76 TeV
- 2012
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 718:2, s. 295-306
-
Journal article (peer-reviewed)abstract
- The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center-of-mass energy root s = 2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges vertical bar y vertical bar < 0.9 and 2.5 < y <4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L-int(e) = 1.1 nb(-1) and L-int(mu) = 19.9 nb(-1), and the corresponding signal statistics are N-J/psi(e+e-) = 59 +/- 14 and N-J/psi(mu+mu-) = 1364 +/- 53. We present d sigma(J/psi)/dy for the two rapidity regions under study and, for the forward-y range, d(2)sigma(J/psi)/dydp(t) in the transverse momentum domain 0 < p(t) < 8 GeV/c. The results are compared with previously published results at root s = 7 TeV and with theoretical calculations. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 7. |
- Abelev, B., et al.
(author)
-
J/psi production as a function of charged particle multiplicity in pp collisions at root s=7 TeV
- 2012
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 712:3, s. 165-175
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Journal article (peer-reviewed)abstract
- The ALICE Collaboration reports the measurement of the relative J/psi yield as a function of charged particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 7 TeV at the LHC. J/psi particles are detected for p(t) > 0, in the rapidity interval vertical bar y vertical bar < 0.9 via decay into e(+)e(-), and in the interval 2.5 < y < 4.0 via decay into mu(+)/mu(-) pairs. An approximately linear increase of the J/psi yields normalized to their event average (dN(J/psi)/dy)/(dN(J/psi)/dy) with (dN(ch)/c eta)/(dN(ch)/d eta) is observed in both rapidity ranges, where dN(ch)/d eta is measured within vertical bar eta vertical bar < 1 and p(t) > 0. In the highest multiplicity interval with (dN(ch)/d eta)(bin)) = 24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/psi yield by a factor of about 5 at 2.5 < y <4 (8 at vertical bar y vertical bar < 0.9) is observed. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 8. |
- Abelev, B., et al.
(author)
-
(KsKs0)-K-0 correlations in pp collisions at root s=7 TeV from the LHC ALICE experiment
- 2012
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 717:1-3, s. 151-161
-
Journal article (peer-reviewed)abstract
- Identical neutral kaon pair correlations are measured in root s = 7 TeV pp collisions in the ALICE experiment. One-dimensional (KsKs0)-K-0 correlation functions in terms of the invariant momentum difference of kaon pairs are formed in two multiplicity and two transverse momentum ranges. The femtoscopic parameters for the radius and correlation strength of the kaon source are extracted. The fit includes quantum statistics and final-state interactions of the a(0)/f(0) resonance. (KsKs0)-K-0 correlations show an increase in radius for increasing multiplicity and a slight decrease in radius for increasing transverse mass, mT, as seen in pi pi correlations in pp collisions and in heavy-ion collisions. Transverse mass scaling is observed between the (KsKs0)-K-0 and pi pi radii. Also, the first observation is made of the decay of the f(2)'(1525) meson into the (KsKs0)-K-0 channel in pp collisions. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 9. |
- Abelev, B., et al.
(author)
-
Light vector meson production in pp collisions at root s=7 TeV ALICE Collaboration
- 2012
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 710:4-5, s. 557-568
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Journal article (peer-reviewed)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 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (eta, rho, omega, eta', phi) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for omega and phi are sigma(omega)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 5.28 +/- 0.54(stat) +/- 0.49(syst) mb and sigma(phi)(1 < p(t) < 5 GeV/c. 2.5 < y < 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.
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| 10. |
- Abelev, B., et al.
(author)
-
Measurement of electrons from beauty hadron decays in pp collisions at root s=7 TeV
- 2013
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 721:1-3, s. 13-23
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Journal article (peer-reviewed)abstract
- The production cross section of electrons from semileptonic decays of beauty hadrons was measured at mid-rapidity (vertical bar y vertical bar < 0.8) in, the transverse momentum range 1 < p(T) < 8 GeV/c with the ALICE experiment at the CERN LHC in pp collisions at a center of mass energy root s = 7 TeV using an integrated luminosity of 2.2 nb(-1). Electrons from beauty hadron decays were selected based on the displacement of the decay vertex from the collision vertex. A perturbative QCD calculation agrees with the measurement within uncertainties. The data were extrapolated to the full phase space to determine the total cross section for the production of beauty quark-antiquark pairs. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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