| 1. |
- Abelev, B., et al.
(författare)
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Heavy flavour decay muon production at forward rapidity in proton-proton collisions at root s=7 TeV
- 2012
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 708:3-5, s. 265-275
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Tidskriftsartikel (refereegranskat)abstract
- The production of muons from heavy flavour decays is measured at forward rapidity in proton-proton collisions at root s = 7 TeV collected with the ALICE experiment at the LHC. The analysis is carried out on a data sample corresponding to an integrated luminosity L-int = 16.5 nb(-1). The transverse momentum and rapidity differential production cross sections of muons from heavy flavour decays are measured in the rapidity range 2.5 < y <4, over the transverse momentum range 2 < p(t) < 12 GeV/c. The results are compared to predictions based on perturbative QCD calculations. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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| 2. |
- Abelev, B., et al.
(författare)
-
Measurement of event background fluctuations for charged particle jet reconstruction in Pb-Pb collisions at root s(NN)=2.76 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :3
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Tidskriftsartikel (refereegranskat)abstract
- The effect of event background fluctuations on charged particle jet reconstruction in Pb-Pb collisions at root s(NN) = 2.76 TeV has been measured with the ALICE experiment. The main sources of non-statistical fluctuations are characterized based purely on experimental data with an unbiased method, as well as by using single high p(t) particles and simulated jets embedded into real Pb-Pb events and reconstructed with the anti-k(t) jet finder. The influence of a low transverse momentum cut-off on particles used in the jet reconstruction is quantified by varying the minimum track p(t) between 0.15 GeV/c and 2 GeV/c. For embedded jets reconstructed from charged particles with p(t) > 0.15 GeV/c, the uncertainty in the reconstructed jet transverse momentum due to the heavy-ion background is measured to be 11.3 GeV/c (standard deviation) for the 10% most central Pb-Pb collisions, slightly larger than the value of 11.0 GeV/c measured using the unbiased method. For a higher particle transverse momentum threshold of 2 GeV/c, which will generate a stronger bias towards hard fragmentation in the jet finding process, the standard deviation of the fluctuations in the reconstructed jet transverse momentum is reduced to 4.8-5.0 GeV/c for the 10% most central events. A non-Gaussian tail of the momentum uncertainty is observed and its impact on the reconstructed jet spectrum is evaluated for varying particle momentum thresholds, by folding the measured fluctuations with steeply falling spectra.
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| 3. |
- Abelev, B., et al.
(författare)
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J/psi Polarization in pp Collisions at root s=7 TeV
- 2012
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Ingår i: Physical Review Letters. - 1079-7114. ; 108:8
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE Collaboration has studied J/psi production in pp collisions at root s = 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/psi polarization parameters lambda(theta) and lambda(phi) 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.
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| 4. |
- Abelev, B., et al.
(författare)
-
Light vector meson production in pp collisions at root s=7 TeV ALICE Collaboration
- 2012
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Ingår i: 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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Tidskriftsartikel (refereegranskat)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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| 5. |
- Abelev, B., et al.
(författare)
-
Measurement of charm production at central rapidity in proton-proton collisions at root s=7 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :1
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Tidskriftsartikel (refereegranskat)abstract
- The p(t)-differential inclusive production cross sections of the prompt charmed mesons D-0, D+, and D*(+) in the rapidity range vertical bar y vertical bar < 0.5 were measured in proton-proton collisions at root s = 7 TeV at the LHC using the ALICE detector. Reconstructing the decays D-0 -> K-pi(+), D+ -> K-pi(+)pi(+), D*(+) -> D-0 pi(+), and their charge conjugates, about 8,400 D-0, 2,900 D+, and 2,600 D*(+) mesons with 1 < p(t) < 24 GeV/c were counted, after selection cuts, in a data sample of 3.14 x 10(8) events collected with a minimum-bias trigger (integrated luminosity L-int = 5 nb(-1)). The results are described within uncertainties by predictions based on perturbative QCD.
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| 6. |
- Abelev, B., et al.
(författare)
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Neutral pion and eta meson production in proton-proton collisions at root s=0.9 TeV and root s=7 TeV
- 2012
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Ingår i: 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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Tidskriftsartikel (refereegranskat)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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| 7. |
- Gómez-Barea, Alberto, et al.
(författare)
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Analytical solutions of sharp interface models with nth order kinetics.
- 2012
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 183, s. 408-421
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Tidskriftsartikel (refereegranskat)abstract
- When a reaction occurs in a narrow layer of a porous particle, it is practical to simplify the calculation ofthe reaction rate by assuming global kinetic parameters based on the surface of the reaction front. Theassumption of such simplified situation allows formulation of a sharp interface model (SIM). Though,there are three difficulties for the application of a SIM in reactor simulations: (1) No analytical solutionis available for general SIM with nth order kinetics with respect to gas reactant. For reactor model simulation,with a variety of particles and operating conditions, a numerical model is still necessary to beapplied, leading to numerical difficulties and time consumption; (2) The global surface kinetic coefficientis not a priori known. The reason is that this coefficient depends not only on the intrinsic reactivity, butalso on physical factors such as the size and density of the solid, as well as operation conditions of thereactor like gas reactant concentration and temperature, varying during conversion of the particle; (3)The SIM is applicable when chemical reaction is rapid compared to intraparticle diffusion because in thissituation the reaction occurs within a narrow region compared to the size of the particle. However, noquantitative criteria has been developed to delimit the conditions for application of SIM. In the presentwork these questions are answered. Char conversion (combustion and gasification) is taken as reference,but most conclusions are applicable to isothermal non-catalytic gas–solid irreversible reactions with asingle gaseous reactant.b
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