Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

School Climate in the Engineering and Architecture Campus of a Mexican Public University: Students’ Perspectives

El objetivo de esta investigación fue identificar el clima escolar que prevalece en estudiantes de la División Académica de Ingeniería y Arquitectura de una universidad pública mexicana. El estudio nace de la necesidad de atender las recomendaciones de los organismos evaluadores de los programas educativos. Se realizó con un enfoque cuantitativo, de tipo descriptivo y correlacional con diseño no experimental transeccional. Las dimensiones estudiadas del clima escolar fueron: estructura organizacional, funcionalidad, prácticas docentes, clima entre la interacción de pares y satisfacción. Se utilizó un cuestionario con una escala tipo Likert, con una confiabilidad de .880 de coeficiente de Alpha de Cronbach y validez a través de un análisis factorial confirmatorio. Los resultados de la estadística descriptiva señalan el clima escolar favorable en interacción de pares y prácticas docentes; el clima menos favorable fue para estructura. El análisis de varianza ANOVA mostró diferencias estadísticamente significativas entre el clima escolar y los programas educativos, los años que el estudiantado ha permanecido en la universidad, la edad y el ciclo escolar. El análisis de correlación de Pearson reveló correlaciones débiles negativas entre el clima escolar y la edad de estudiantes. The objective of this research was to identify the school climate that prevails in the students of the faculty of Engineering and Architecture in a Mexican public University. This study was conducted in response to a need to take care of the recommendations of the agencies evaluating the educational programs. It was done with a quantitative approach, of a descriptive and correlational type with non-experimental transactional design. The studied dimensions of the school climate were: organization structure, functionality, pedagogical practices, climate between peer interaction and satisfaction. The data were collected using a Likert scale questionnaire, with a reliability of .880 of Cronbach’s Alpha coefficient and validity through confirmatory factorial analysis. The results obtained from the descriptive statistics pointed the favorable school climate in peer interaction and pedagogical practices. Organizational structure, however, was the lowest rated classroom climate dimension. ANOVA results showed significant statistical differences between the school climate and educational programs, the years that the students have remained in the university, the age and the school cycle. Pearson’s correlation analysis revealed weak and negative correlation between school climate and student age

Estudios sociales y administrativos en América Latina

Esta obra contiene la compilación de una serie de investigaciones latinoamericanas en las cuales se presenta los nuevos enfoques investigativos, metodológicos y cientificos. Para la generación de soluciones que contribuyan a la toma de decisiones en variables, sociales, economicas y administrativas en los diferentes contextos organizacionales. Además de estos elementos, en esta obra se presentan nuevas apuestas multidisciplinares cuanti-cualitativas en las cuales se destacan la ingeniería, derecho entre otros.

Compilación de Proyectos de Investigacion de 1984-2002

Instituto Politecnico Nacional. UPIICS

Measurement of an excess in the yield of J/ψ at very low pT in Pb–Pb collisions at √sNN = 2.76 TeV

We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (pT<0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at sNN−−−√ = 2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor (RAA) of J/ψ in the rapidity range 2.5<y<4 reaches about 7 (2) in the pT range 0-0.3 GeV/c in the 70-90% (50-70%) centrality class. The J/ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/ψ is the underlying physics mechanism. If confirmed, the observation of J/ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the Quark-Gluon Plasma

Measurement of transverse energy at midrapidity in Pb–Pb collisions at √sNN = 2.76 TeV

We report the transverse energy (ET) measured with ALICE at midrapidity in Pb-Pb collisions at sNN−−−√ = 2.76 TeV as a function of centrality. The transverse energy was measured using identified single particle tracks. The measurement was cross checked using the electromagnetic calorimeters and the transverse momentum distributions of identified particles previously reported by ALICE. The results are compared to theoretical models as well as to results from other experiments. The mean ET per unit pseudorapidity (η), ⟨dET/dη⟩, in 0-5% central collisions is 1737 ± 6(stat.) ± 97(sys.) GeV. We find a similar centrality dependence of the shape of ⟨dET/dη⟩ as a function of the number of participating nucleons to that seen at lower energies. The growth in ⟨dET/dη⟩ at the LHC sNN−−−√ exceeds extrapolations of low energy data. We observe a nearly linear scaling of ⟨dET/dη⟩ with the number of quark participants. With the canonical assumption of a 1 fm/c formation time, we estimate that the energy density in 0-5% central Pb-Pb collisions at sNN−−−√ = 2.76 TeV is 12.3 ± 1.0 GeV/fm3\xspace and that the energy density at the most central 80 fm2 of the collision is at least 21.5 ± 1.7 GeV/fm3. This is roughly 2.3 times that observed in 0-5% central Au-Au collisions at sNN−−−√ = 200 GeV

Centrality dependence of the charged-particle multiplicity density at midrapidity in Pb–Pb collisions at √sNN = 5.02 TeV

The pseudorapidity density of charged particles (dNch/dη) at mid-rapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of sNN−−−√ = 5.02 TeV. It increases with centrality and reaches a value of 1943±54 in |η|<0.5 for the 5% most central collisions. A rise in dNch/dη as a function of sNN−−−√ for the most central collisions is observed, steeper than that observed in proton-proton collisions and following the trend established by measurements at lower energy. The centrality dependence of dNch/dη as a function of the average number of participant nucleons, ⟨Npart⟩, calculated in a Glauber model, is compared with the previous measurement at lower energy. A constant factor of about 1.2 describes the increase in 2⟨Npart⟩⟨dNch/dη⟩ from sNN−−−√ = 2.76 TeV to sNN−−−√ = 5.02 TeV for all centrality intervals, within the measured range of 0-80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions

Anisotropic flow of charged particles in Pb–Pb collisions at √sNN = 5.02 TeV

We report the first results of elliptic (v2), triangular (v3) and quadrangular flow (v4) of charged particles in Pb-Pb collisions at sNN−−−√=5.02 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurements are performed in the central pseudorapidity region |η|<0.8 and for the transverse momentum range 0.2<pT<5 GeV/c. The anisotropic flow is measured using two-particle correlations with a pseudorapidity gap greater than one unit and with the multi-particle cumulant method. Compared to results from Pb-Pb collisions at sNN−−−√=2.76 TeV, the anisotropic flow coefficients v2, v3 and v4 are found to increase by (3.0±0.6)%, (4.3±1.4)% and (10.2±3.8)%, respectively, in the centrality range 0-50%. This increase can be attributed mostly to an increase of the average transverse momentum between the two energies. The measurements are found to be compatible with hydrodynamic model calculations. This comparison provides a unique opportunity to test the validity of the hydrodynamic picture and the power to further discriminate between various possibilities for the temperature dependence of shear viscosity to entropy density ratio of the produced matter in heavy-ion collisions at the highest energies

Charge-dependent flow and the search for the Chiral Magnetic Wave in Pb–Pb collisions at √sNN = 2.76 TeV

We report on measurements of a charge-dependent flow using a novel three-particle correlator with ALICE in Pb-Pb collisions at the LHC, and discuss the implications for observation of local parity violation and the Chiral Magnetic Wave (CMW) in heavy-ion collisions. Charge-dependent flow is reported for different collision centralities as a function of the event charge asymmetry. While our results are in qualitative agreement with expectations based on the CMW, the nonzero signal observed in higher harmonics correlations indicates a possible significant background contribution. We also present results on a differential correlator, where the flow of positive and negative charges is reported as a function of the mean charge of the particles and their pseudorapidity separation. We argue that this differential correlator is better suited to distinguish the differences in positive and negative charges expected due to the CMW and the background effects, such as local charge conservation coupled with strong radial and anisotropic flow