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

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Isolated photon cross section in pp collisions at s\sqrt{s} = 8 TeV with the ALICE at LHC

In ultra-relativistic hadronic collisions, direct photons are those photons that are directly produced in elementary processes and act as a valuable tool to test perturbative Quantum Chromodynamics (pQCD) predictions. Since these photons are produced directly from parton–parton hard scatterings, they can be used to constrain the parton distribution functions (PDFs). In leading order pQCD, direct photons are mainly produced via 2→2 processes, namely quark–gluon Compton scattering and quark–antiquark annihilation. These photons together with the fragmentation or bremsstrahlung photons are referred to as the prompt photons [1]. Photons from the 2→2 processes provide clear constraints of the underlying parton kinematics, but making a clean separation between the different types of prompt photons is difficult. Additionally, measurements of direct photons are complicated due to the presence of a large photon background from hadron decays, especially from π 0 and η mesons. A selection called ”isolation criterion”, which is based on a threshold on the contributions of transverse energy/momentum from particles inside a cone around the candidate photon, is applied to suppress the decay and fragmentation photons. This has led to the prescription of ”isolated photons”

Probing the Initial State with Isolated-photon Production and Dijet Invariant Mass Distributions in Small Collision Systems with ALICE

Isolated photons and dijets measurements in small collision systems, i.e., pp and pA, probe the initial state of the collision, providing the opportunity to constrain PDFs, test pQCD predictions, and probe cold nuclear matter effects. In addition, dijet measurements are sensitive to interactions of partons with the medium produced in Pb–Pb collisions that induce modifications in jet properties. Therefore, measurements in small collision systems also offer a baseline for Pb–Pb collision measurements. In this article, we present the measurement of isolated photons and dijets in small collision systems, pp and p–Pb by ALICE. Isolated photons are measured in pp collisions at √ s = 8 and 13 TeV and in p–Pb collisions at √ sNN = 5.02 TeV, down to pT = 10 GeV/c, extending previous measurements at these centre-of-mass energies down to small x ∼ 10−3. The dijet invariant mass is measured in pp and p–Pb collisions at √ sNN = 5.02 TeV within the range from 80 to 150 GeV/c2, probing a region where medium effects are expected to be strong

Prototype Test for Electromagnetic Calorimeter, FOCAL, at CERN-SPS Using Large Dynamic Range Readout Electronics

A silicon–tungsten prototype calorimeter, for the proposed ALICE LS3-upgarde, was fabricated and tested at the CERN-SPS beamline facility in the year 2017. The calorimeter was designed with the help of GEANT4 simulation to perform in a high multiplicity density environment with optimised energy and position resolutions for incident energy up to 200 GeV. There were several tests conducted with different prototype configurations both at laboratory and CERN beamline facilities. The latest prototype in the series consists of 20 layers, each layer consisting of a 6 * 6 array of 1cm2 silicon pad detector, fabricated on a single 300 um thin wafer, and 1 radiation length (XR) thick, 10 cm * 10 cm pure tungsten plates as absorbers. Data was collected for pion, muon, and electron over a wide range of incident energies (20–180 GeV). Because of large energy deposition within the calorimeter by the electromagnetic showers, the readout electronics need to have a large dynamic range. Here, we will discuss the performances of the prototype, experimented at CERN-SPS, using a newly developed readout electronics (ANUINDRA) with a large dynamic range (up to 2.6 pC) and compare the improvements in this regard

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

Nuclear modification factor of light neutral-meson spectra up to high transverse momentum in p–Pb collisions at sNN=8.16 TeV

International audienceNeutral pion (π0) and η meson production cross sections were measured up to unprecedentedly high transverse momenta (pT) in p–Pb collisions at sNN=8.16TeV. The mesons were reconstructed via their two-photon decay channel in the rapidity interval −1.3&lt;y&lt;0.3 in the ranges of 0.4&lt;pT&lt;200 GeV/c and 1.0&lt;pT&lt;50 GeV/c, respectively. The respective nuclear modification factor (RpPb) is presented for pT up to of 200 and 30 GeV/c, where the former was achieved by extending the π0 measurement in pp collisions at s=8TeV using the merged cluster technique. The values of RpPb are below unity for pT&lt;10 GeV/c, while they are consistent with unity for pT&gt;10 GeV/c, leaving essentially no room for final state energy loss. The new data provide strong constraints for nuclear parton distribution and fragmentation functions over a broad kinematic range and are compared to model predictions as well as previous results at sNN=5.02TeV

Production of pions, kaons, (anti-)protons and ϕ\phi mesons in Xe–Xe collisions at sNN\sqrt{s_{\mathrm{NN}}} = 5.44 TeV

The first measurement of the production of pions, kaons, (anti-)protons and $\phi$ mesons at midrapidity in Xe–Xe collisions at $\sqrt{s_{\mathrm{NN}}} = 5.44~\text {TeV}$ is presented. Transverse momentum ($p_{\mathrm{T}}$) spectra and $p_{\mathrm{T}}$-integrated yields are extracted in several centrality intervals bridging from p–Pb to mid-central Pb–Pb collisions in terms of final-state multiplicity. The study of Xe–Xe and Pb–Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe–Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the $\phi$-to-pion ratio with increasing final-state multiplicity

Dielectron production at midrapidity at low transverse momentum in peripheral and semi-peripheral Pb–Pb collisions at √sNN = 5.02 TeV

The first measurement of the e+e− pair production at low lepton pair transverse momentum (pT,ee) and low invariant mass (mee) in non-central Pb−Pb collisions at sNN−−−√=5.02 TeV at the LHC is presented. The dielectron production is studied with the ALICE detector at midrapidity (|ηe|<0.8) as a function of invariant mass (0.4≤mee<2.7 GeV/c2) in the 50−70% and 70−90% centrality classes for pT,ee<0.1 GeV/c, and as a function of pT,ee in three mee intervals in the most peripheral Pb−Pb collisions. Below a pT,ee of 0.1 GeV/c, a clear excess of e+e− pairs is found compared to the expectations from known hadronic sources and predictions of thermal radiation from the medium. The mee excess spectra are reproduced, within uncertainties, by different predictions of the photon−photon production of dielectrons, where the photons originate from the extremely strong electromagnetic fields generated by the highly Lorentz-contracted Pb nuclei. Lowest-order quantum electrodynamic (QED) calculations, as well as a model that takes into account the impact-parameter dependence of the average transverse momentum of the photons, also provide a good description of the pT,ee spectra. The measured ⟨p2T,ee⟩−−−−−√ of the excess pT,ee spectrum in peripheral Pb−Pb collisions is found to be comparable to the values observed previously at RHIC in a similar phase-space region