Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Memoria del tercer simposium sobre Historia, sociedad y cultura de México y América Latina

Esta Memoria del Tercer Simposium sobre Historia, Sociedad y Cultura de México y América Latina no sólo reúne 38 trabajos presentados durante el evento celebrado del 9 al 11 de octubre de 2007, sino que es constancia del interés de los investigadores y de las instituciones participantes por abordar temas que preocupan a la sociedad latinoamericana actual.El objetivo principal de este trabajo es doble. En el primer apartado, “Democracia y autoritarismo”, se establecen y comentan sendas definiciones de democracia y autoritarismo que, en principio, se podrían aplicar a cualquier sistema político de la historia de la humanidad. En el segundo apartado, “Aspectos por considerar en estudios de caso sobre cualquier tipo de democracia”, se mencionan algunos tópicos concretos involucrados en la concepción de democracia expuesta en el apartado anterior, con la finalidad de proporcionar elementos de análisis a quienes deseen aplicarlos a estudios de caso

Multiplicity dependence of light (anti-)nuclei production in p–Pb collisions at sNN=5.02 TeV

The measurement of the deuteron and anti-deuteron production in the rapidity range −1 < y < 0 as a function of transverse momentum and event multiplicity in p–Pb collisions at √sNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-of- flight. Their production in p–Pb collisions is compared to pp and Pb–Pb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in Pb–Pb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in p–Pb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window −1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number

Λ3H^3_\Lambda\mathrm{H} and Λˉ3H‾^3_{\bar{\Lambda}}\mathrm{\overline{H}} lifetime measurement in Pb-Pb collisions at sNN=\sqrt{s_{\mathrm{NN}}} = 5.02 TeV via two-body decay

International audienceAn improved value for the lifetime of the (anti-)hypertriton has been obtained using the data sample of Pb–Pb collisions at sNN=5.02 TeV collected by the ALICE experiment at the LHC. The (anti-)hypertriton has been reconstructed via its charged two-body mesonic decay channel and the lifetime has been determined from an exponential fit to the d N /d( ct ) spectrum. The measured value, τ=242−38+34 (stat.) ± 17 (syst.) ps, is compatible with representative theoretical predictions, thus contributing to the solution of the longstanding hypertriton lifetime puzzle

K∗(892)0 and φ(1020) production at midrapidity in pp collisions at √s = 8

The production of K∗(892)0 and ϕ(1020) in pp collisions at s√ = 8 TeV were measured using Run 1 data collected by the ALICE collaboration at the LHC. The pT-differential yields d2N/dydpT in the range 0 < pT < 20 GeV/c for K∗0 and 0.4 < pT < 16 GeV/c for ϕ have been measured at midrapidity |y| < 0.5. Moreover, improved measurements of the K∗(892)0 and ϕ(1020) at s√ = 7 TeV are presented. The collision energy dependence of pT distributions, pT-integrated yields and particle ratios in inelastic pp collisions are examined. The results are also compared with different collision systems. The values of the particle ratios are measured to be similar to those found at other LHC energies. In pp collisions a hardening of the particle spectra is observed with increasing energy, but at the same time it is also observed that the relative particle abundances are independent of the collision energy. The pT-differential yields of K∗0 and ϕ in pp collisions at s√ = 8 TeV are compared with the expectations of different Monte Carlo event generators

Global polarization of ΛΛˉ\Lambda \bar \Lambda hyperons in Pb-Pb collisions at sNN\sqrt {s_{NN}} = 2.76 and 5.02 TeV

International audienceThe global polarization of the $\Lambda$ and $\overline\Lambda$ hyperons is measured for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV recorded with the ALICE at the LHC. The results are reported differentially as a function of collision centrality and hyperon's transverse momentum ($p_{\rm{T}}$) for the range of centrality 5-50%, $0.5 < p_{\rm{T}} <5$ GeV/$c$, and rapidity $|y|<0.5$. The hyperon global polarization averaged for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV is found to be consistent with zero, $\langle P_{\rm{H}}\rangle$ (%) $\approx$ 0.01 $\pm$ 0.06 (stat.) $\pm$ 0.03 (syst.) in the collision centrality range 15-50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at RHIC, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%

Global polarization of Λ and Λ hyperons in Pb-Pb collisions at √ s N N = 2.76 and 5.02 TeV

The global polarization of Λ and Λ hyperons is measured for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV recorded with the ALICE at the Large Hadron Collider (LHC). The results are reported differentially as a function of collision centrality and hyperon’s transverse momentum (pT ) for the range of centrality 5–50%, 0.5 < pT < 5 GeV/c, and rapidity |y| < 0.5. The hyperon global polarization averaged for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV is found to be consistent with zero, ⟨PH⟩(%)≈0.01±0.06(stat.)±0.03(syst.) in the collision centrality range 15–50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at the Relativistic Heavy Ion Collider, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%

Global polarization of Λ and ¯Λ hyperons in Pb–Pb collisions at the LHC

The global polarization of the Λ and Λ¯¯¯¯ hyperons is measured for Pb-Pb collisions at sNN−−−√ = 2.76 and 5.02 TeV recorded with the ALICE at the LHC. The results are reported differentially as a function of collision centrality and hyperon's transverse momentum (pT) for the range of centrality 5-50%, 0.5<pT<5 GeV/c, and rapidity |y|<0.5. The hyperon global polarization averaged for Pb-Pb collisions at sNN−−−√ = 2.76 and 5.02 TeV is found to be consistent with zero, ⟨PH⟩ (%) ≈ 0.01 ± 0.06 (stat.) ± 0.03 (syst.) in the collision centrality range 15-50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at RHIC, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%