Evidence for associated production of a single top quark and W Boson in pp collisions at √s=7 TeV

Evidence is presented for the associated production of a single top quark and W boson in pp collisions at √s=7 TeV with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 4.9 fb -1. The measurement is performed using events with two leptons and a jet originated from a b quark. A multivariate analysis based on kinematic properties is utilized to separate the tt̄ background from the signal. The observed signal has a significance of 4.0σ and corresponds to a cross section of 16-4+5 pb, in agreement with the standard model expectation of 15.6±0.4-1.2+1.0 pb. © 2013 CERN, for the CMS Collaboration Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Measurement of the azimuthal anisotropy of neutral pions in Pb-Pb collisions at √sNN=2.76 TeV

First measurements of the azimuthal anisotropy of neutral pions produced in Pb-Pb collisions at a center-of-mass energy of √sNN=2.76 TeV are presented. The amplitudes of the second Fourier component (v2) of the π0 azimuthal distributions are extracted using an event-plane technique. The values of v2 are studied as a function of the neutral pion transverse momentum (pT) for different classes of collision centrality in the kinematic range 1.6

En memoria de Pedro Vuskovic

Para quienes compartimos con Pedro Vuskovic una experiencia de amistad y colaboración profesional a lo largo de muchos años, la noticia de su fallecimiento en México nos ha provocado un sentimiento de profundo pesar. No sólo por las circunstancias mismas de su muerte, al cabo de una cruel enfermedad que fue minando gradualmente su capacidad física -aunque no la intelectual- sino por la pérdida de un latinoamericano de gran valía, de un maestro formador de numerosas generaciones de jóvenes de nuestro continente, y del compañero de tantas jornadas de lucha intelectual y política. Pedro ingresó a la CEPAL en 1950, prácticamente desde los inicios de la institución. Por espacio de casi 20 años realizó en su seno una brillante labor profesional, habiendo culminado su carrera en ella como Director de la División de Desarrollo. Sus aportes fueron decisivos para la estructuración y difusión del pensamiento cepalino, en una época en la que bullían las inquietudes de una pléyade de talentosos economistas y otros cientistas sociales. Eran los años de la posguerra, los cincuenta y los sesenta, cuando era menester "construir" a América Latina. Y Pedro Vuskovic colocó muchos ladrillos en esa colectiva construcción teórico-política que ha tenido tanta trascendencia para los países de la región. Coetáneamente, fue profesor en los programas de capacitación de la CEPAL y del ILPES, a la vez que impartía clases en la Escuela de Economía y en la de Sociología de la Universidad de Chile, así como en la Escuela de Economía de la Universidad de Concepción. Al retirarse de la CEPAL se incorporó de lleno a la actividad académica, desempeñándose como Director del Instituto de Economía de la Universidad de Chile, para luego pasar a ocupar un lugar de primer plano en la política chilena. En noviembre de 1970 fue designado Ministro de Economía por el Presidente Salvador Allende y en junio de 1972 pasó a ocupar el cargo de Vicepresidente Ejecutivo de la Corporación de Fomento de la Producción, con rango de Ministro, el que desempeñó hasta septiembre de 1973. Cuando las circunstancias políticas lo llevaron al exilio en México, país que lo acogió generosamente, como a tantos otros latinoamericanos que enfrentaban problemas similares, Pedro siguió desarrollando una importante labor académica, primero en el Centro de Investigación y Docencia Económicas, donde dirigió el Instituto de Estudios Económicos de América Latina, y posteriormente en el Centro de Investigaciones Interdisciplinarias en Humanidades de la Universidad Nacional Autónoma de México, donde fue designado Coordinador de un programa de estudios sobre pobreza y alternativas de desarrollo en diversos países de Latinoamérica. Aun cuando será recordado por su importante actuación política, su labor como académico y economista debe ser especialmente destacada. Junto con ser un expositor brillante, metódico e incisivo, que dominaba sus temas con gran sapiencia y amplitud, Pedro sentía un especial regocijo de estar con la juventud, estimularla intelectualmente y ser estimulado por ella. Las muchas generaciones de estudiantes latinoamericanos que tuvieron la fortuna de ser sus alumnos pueden dar testimonio de ello. A su vocación de investigador y maestro, Pedro Vuskovic unía una profunda sensibilidad política y social, que lo llevó a tomar como propia la causa de los pobres y los desamparados de América Latina, cuya situación pudo conocer muy tempranamente en su vida a través de los numerosos trabajos que realizó dentro del ámbito de la CEPAL. Fue tenaz y consecuente en sus ideas y principios, y luchó por ellas en todas las arenas en que estuvo situado --académicas y políticas- hasta el final de su vida. Quienes fuimos sus amigos y colegas recordamos también su bonhomía, sentido del humor y gran calidad humana, rasgos que iban unidos a una lealtad a toda prueba a sus principios valóricos. Nuestra despedida es con emoción; Pedro Vuskovic nos deja un legado de recuerdos y enseñanzas que tendremos siempre presentes. En nombre de sus amigos y colegas, Jacobo Schatan, Ex Director de la División Agrícola Conjunta CEPAL/FAO

Phenotypic variation of leptodactylus cupreus caramaschi, são-pedro and feio, 2008 (Anura, Leptodactylidae)

This study describes for the first time the female of Leptodactylus cupreus and provides new information concerning its geographical distribution, male's morphology and bioacustics. Leptodactylus cupreus, a poorly known species from the Brazilian Atlantic Forest, was originally allocated in the L. mystaceus complex of the L. fuscus species group. Based on morphological observations, we infer that L. cupreus should be in fact related to L. mystacinus, a species that, although assigned to the L. fuscus species group, is not assigned to the L. mystaceus complex. Therefore, we comment the phylogenetic relationships concerning L. cupreus, L. mystaceus and L. mystacinus. © 2013 Magnolia Press.

Search for pair production of third-generation leptoquarks and top squarks in pp collisions at √s=7 TeV

Results are presented from a search for the pair production of third-generation scalar and vector leptoquarks, as well as for top squarks in R-parity-violating supersymmetric models. In either scenario, the new, heavy particle decays into a τ lepton and a b quark. The search is based on a data sample of pp collisions at √s=7 TeV, which is collected by the CMS detector at the LHC and corresponds to an integrated luminosity of 4.8 fb -1. The number of observed events is found to be in agreement with the standard model prediction, and exclusion limits on mass parameters are obtained at the 95% confidence level. Vector leptoquarks with masses below 760 GeV are excluded and, if the branching fraction of the scalar leptoquark decay to a τ lepton and a b quark is assumed to be unity, third-generation scalar leptoquarks with masses below 525 GeV are ruled out. Top squarks with masses below 453 GeV are excluded for a typical benchmark scenario, and limits on the coupling between the top squark, τ lepton, and b quark, λ333′ are obtained. These results are the most stringent for these scenarios to date. © 2013 CERN.

Measurement of the υ(1S), υ(2S), and υ(3S) polarizations in pp collisions at √s=7 TeV

The polarizations of the υ(1S), υ(2S), and υ(3S) mesons are measured in proton-proton collisions at √s=7 TeV, using a data sample of υ(nS)→μ+μ- decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb-1. The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters λ™, λφ, and λ, as well as the frame-invariant quantity λ, are presented as a function of the υ(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges |y|<0.6 and 0.6<|y|<1.2. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region. © 2013 CERN.

Study of the mass and spin-parity of the Higgs boson candidate via its decays to Z boson pairs

A study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of 17.3 fb-1, collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used. The measured mass in the ZZ channel, where both Z bosons decay to e or μ pairs, is 126.2±0.6(stat) ±0.2(syst) GeV. The angular distributions of the lepton pairs in this channel are sensitive to the spin-parity of the boson. Under the assumption of spin 0, the present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis. © 2013 CERN. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Search for pair-produced dijet resonances in four-jet final states in pp collisions at √s=7 TeV

A search for the pair production of a heavy, narrow resonance decaying into two jets has been performed using events collected in √s=7 TeV pp collisions with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 5.0 fb-1. Events are selected with at least four jets and two dijet combinations with similar dijet mass. No resonances are found in the dijet mass spectrum. The upper limit at 95% confidence level on the product of the resonance pair production cross section, the branching fractions into dijets, and the acceptance varies from 0.22 to 0.005 pb, for resonance masses between 250 and 1200 GeV. Pair-produced colorons decaying into qq̄ are excluded for coloron masses between 250 and 740 GeV. © 2013 CERN. citation, and DOI.

Measurement of associated production of vector bosons and top quark-antiquark pairs in pp collisions at √s=7 TeV

The first measurement of vector-boson production associated with a top quark-antiquark pair in proton-proton collisions at √s=7 TeV is presented. The results are based on a data set corresponding to an integrated luminosity of 5.0 fb-1, recorded by the CMS detector at the LHC in 2011. The measurement is performed in two independent channels through a trilepton analysis of tt̄Z events and a same-sign dilepton analysis of tt̄V (V=W or Z) events. In the trilepton channel a direct measurement of the tt̄Z cross section σtt̄Z=0.28-0.11+0.14 (stat)-0.03+0.06 (syst) pb is obtained. In the dilepton channel a measurement of the tt̄V cross section yields σtt̄V=0.43-0.15+0.17 (stat)-0.07+0.09 (syst) pb. These measurements have a significance, respectively, of 3.3 and 3.0 standard deviations from the background hypotheses and are compatible, within uncertainties, with the corresponding next-to-leading order predictions of 0.137-0.016+0.012 and 0.306-0.053+0.031 pb. © 2013 CERN. Published by the American Physical Society.

Inclusive search for supersymmetry using razor variables in pp collisions at √s=7 TeV

An inclusive search is presented for new heavy particle pairs produced in √s=7 TeV proton-proton collisions at the LHC using 4.7±0.1 fb -1 of integrated luminosity. The selected events are analyzed in the 2D razor space of MR, an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the missing transverse energy. The third-generation sector is probed using the event heavy-flavor content. The search is sensitive to generic supersymmetry models with minimal assumptions about the superpartner decay chains. No excess is observed in the number of events beyond that predicted by the standard model. Exclusion limits are derived in the CMSSM framework as well as for simplified models. Within the CMSSM parameter space considered, gluino masses up to 800 GeV and squark masses up to 1.35 TeV are excluded at 95% confidence level depending on the model parameters. The direct production of pairs of top or bottom squarks is excluded for masses as high as 400 GeV. © 2013 CERN.

Measurement of the Bs0→μ+μ- branching fraction and search for B0→μ+μ- with the CMS experiment

Results are presented from a search for the rare decays Bs0→μ+μ- and B0→μ+μ - in pp collisions at √s=7 and 8 TeV, with data samples corresponding to integrated luminosities of 5 and 20 fb-1, respectively, collected by the CMS experiment at the LHC. An unbinned maximum-likelihood fit to the dimuon invariant mass distribution gives a branching fraction B(Bs0→μ+μ-)=(3.0-0.9+1.0) ×10-9, where the uncertainty includes both statistical and systematic contributions. An excess of Bs0→μ+μ- events with respect to background is observed with a significance of 4.3 standard deviations. For the decay B0→μ+μ- an upper limit of B(B0→μ+μ-)<1.1×10 -9 at the 95% confidence level is determined. Both results are in agreement with the expectations from the standard model. © 2013 CERN. Published by the American Physical Society under the terms of the.

Ciudad y municipio de San Pedro Sula, Honduras: síntesis del informe final del estudio de caso

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Gestión urbana en San Pedro Sula, Honduras: la perspectiva del municipio

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A figura humana fragmentada na pintura: Tiradentes esquartejado em Pedro Américo e Adriana Varejão

Pós-graduação em Artes - IA