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  • Search for tb resonances in proton-proton collisions at $\sqrt{s}=7$ TeV with the ATLAS detector
    Publication . ATLAS collaboration (3038 authors); Aguilar-Saavedra, Juan Antonio; Amaral, Pedro; Anjos, Nuno; Carvalho, João; Castro, Nuno Filipe; Conde Muiño, Patricia; Do Valle Wemans, André; Fiolhais, Miguel; Gomes, Agostinho; Gonçalo, Ricardo; Jorge, Pedro; Lopes, Lourenco; Machado Miguens, Joana; Maio, Amélia; Maneira, José; Oliveira, Miguel Alfonso; Onofre, António; Palma, Alberto; Pina, João Antonio; Pinto, Belmiro; Santos, Helena; Saraiva, João; Silva, José; Veloso, Filipe; Wolters, Helmut
    This Letter presents a search for tb resonances in 1.04/fb of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape of the tb invariant mass distribution compared to the expected Standard Model backgrounds. The model of a right-handed W'_R with Standard Model-like couplings is chosen as the benchmark model for this search. No statistically significant excess of events is observed in data, and upper limits on the cross section times the branching ratio of W'_R resonances at 95% CL lie in the range 6.1-1.0 pb for W'_R masses ranging from 0.5 to 2.0 TeV. These limits are translated into a lower bound on the allowed right-handed W'_R mass, giving m_{W'_R} > 1.13 TeV at 95% CL.
    2012-05Journal article Open access Show more
  • Measurement of the pseudorapidity and centrality dependence of the transverse energy density in PbPb collisions at $\sqrt{s_{NN}}=2.76$ TeV
    Publication . CMS collaboration (2170 authors); Hollar, Jonathan; Nayak, Aruna; Almeida, Nuno; Bargassa, Pedrame; David Tinoco Mendes, Andre; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Seixas, Joao; Varela, Joao; Vischia, Pietro; Lloret Iglesias, Lara; Musella, Pasquale; Rodrigues Antunes, Joao; Silva, Pedro; Pela, Joao; Leonardo, Nuno
    The transverse energy ET in PbPb collisions at 2.76 TeV nucleon-nucleon center-of-mass energy sqrt(s[NN]) has been measured over a broad range of pseudorapidity eta and collision centrality using the CMS detector at the LHC. The transverse energy density per unit pseudorapidity d(ET)/d(eta) increases faster with collision energy than the charged particle multiplicity. This implies that the mean energy per particle is increasing with collision energy. At all pseudorapidities the transverse energy per participating nucleon increases with the centrality of the collision. The ratio of transverse energy per unit pseudorapidity in peripheral to central collisions varies significantly as the pseudorapidity increases from eta = 0 to abs(eta) = 5.0. For the 5% most central collisions the energy density per unit volume is estimated to be about 14 GeV/fm^3 at a time of 1 fm/c after the collision. This is about 100 times larger than normal nuclear matter density and a factor of 2.6 times higher than the energy density reported at sqrt(s[NN]) = 200 GeV at RHIC.
    2012-05Journal article Open access Show more
  • Search for a light charged Higgs boson in top quark decays in $pp$ collisions at $\sqrt{s}=7$ TeV
    Publication . CMS collaboration (2193 authors); Hollar, Jonathan; Nayak, Aruna; Almeida, Nuno; Bargassa, Pedrame; David Tinoco Mendes, Andre; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Seixas, Joao; Varela, Joao; Vischia, Pietro; Lloret Iglesias, Lara; Musella, Pasquale; Rodrigues Antunes, Joao; Silva, Pedro; Pela, Joao; Leonardo, Nuno
    Results are presented on a search for a light charged Higgs boson that can be produced in the decay of the top quark to charged H and b quark and which, in turn, decays into tau and tau neutrino. The analysed data correspond to an integrated luminosity of about 2 inverse femtobarns recorded in proton-proton collisions at sqrt(s) = 7 TeV by the CMS experiment at the LHC. The search is sensitive to the decays of the top quark pairs t anti-t to charged Higgs W b anti-b and t anti-t to two charged Higgs b anti-b. Various final states have been studied separately, all requiring presence of a tau lepton from charged Higgs decays, missing transverse energy, and multiple jets. Upper limits on the branching fraction B(t to charged Higgs b) in the range of 2-4% are established for charged Higgs boson masses between 80 and 160 GeV, under the assumption that B(charged Higgs to tau anti-tau neutrino) = 1.
    2012-05Journal article Open access Show more
  • An Ultra-Low Background PMT for Liquid Xenon Detectors
    Publication . Akerib, D.S. et al. (64 authors); de Viveiros, L.; Lindote, A.; Lopes, M.I.; Neves, F.; Silva, C.; Solovov, V.N.
    Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6cm diameter R8778 PMT, used in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes: ^2^3^8U, ^2^3^2Th, ^4^0K, and ^6^0Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4^2^3^8U/<0.3^2^3^2Th/<8.3^4^0K/2.0+/-0.2 ^6^0Co mBq/PMT. This represents a large reduction, equal to a change of x124^2^3^8U/x19^2^3^2Th/x18^4^0K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5-6.4cm diameter). ^6^0Co measurements are comparable between the PMTs, but can be significantly reduced in future R11410 MOD units through further material selection. Assuming PMT activity equal to the measured 90% upper limits, Monte Carlo estimates indicate that replacement of R8778 PMTs with R11410 MOD PMTs will change LUX PMT electron recoil background contributions by a factor of x125 after further material selection for ^6^0Co reduction, and nuclear recoil backgrounds by a factor of x136. The strong reduction in backgrounds below the measured R8778 levels makes the R11410 MOD a very competitive technology for use in large-scale liquid xenon detectors.
    2012-05Journal article Open access Show more
  • Search for new physics with same-sign isolated dilepton events with jets and missing transverse energy
    Publication . CMS collaboration (2210 authors); Hollar, Jonathan; Nayak, Aruna; Almeida, Nuno; Bargassa, Pedrame; David Tinoco Mendes, Andre; Faccioli, Pietro; Fernandes, Miguel; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Seixas, Joao; Varela, Joao; Vischia, Pietro; Lloret Iglesias, Lara; Musella, Pasquale; Rodrigues Antunes, Joao; Silva, Pedro; Pela, Joao; Leonardo, Nuno
    A search for new physics is performed in events with two same-sign isolated leptons, hadronic jets, and missing transverse energy in the final state. The analysis is based on a data sample corresponding to an integrated luminosity of 4.98 inverse femtobarns produced in pp collisions at a center-of-mass energy of 7 TeV collected by the CMS experiment at the LHC. This constitutes a factor of 140 increase in integrated luminosity over previously published results. The observed yields agree with the standard model predictions and thus no evidence for new physics is found. The observations are used to set upper limits on possible new physics contributions and to constrain supersymmetric models. To facilitate the interpretation of the data in a broader range of new physics scenarios, information on the event selection, detector response, and efficiencies is provided.
    2012-05Journal article Open access Show more
  • Measurement of the W boson polarization in top quark decays with the ATLAS detector
    Publication . ATLAS collaboration (2868 authors); Aguilar-Saavedra, Juan Antonio; Anjos, Nuno; Cantrill, Robert; Carvalho, João; Castro, Nuno Filipe; Conde Muiño, Patricia; Da Cunha Sargedas De Sousa, Mario Jose; Do Valle Wemans, André; Fiolhais, Miguel; Gomes, Agostinho; Gonçalo, Ricardo; Jorge, Pedro; Lopes, Lourenco; Machado Miguens, Joana; Maio, Amélia; Maneira, José; Oliveira, Miguel Alfonso; Onofre, António; Palma, Alberto; Pina, João Antonio; Pinto, Belmiro; Santos, Helena; Saraiva, João; Silva, José; Veloso, Filipe; Wolters, Helmut
    This paper presents measurements of the polarization of W bosons in top quark decays, derived from ttbar events with missing transverse momentum, one charged lepton and at least four jets, or two charged leptons and at least two jets. Data from pp collisions at a centre-of-mass energy of 7 TeV were collected with the ATLAS experiment at the LHC and correspond to an integrated luminosity of 1.04 fb^-1. The measured fractions of longitudinally, left- and right-handed polarization are F_0=0.67+/-0.07, F_L=0.32+/-0.04 and F_R=0.01+/-0.05, in agreement with the Standard Model predictions. As the polarization of the W bosons in top quark decays is sensitive to the Wtb vertex Lorentz structure and couplings, the measurements were used to set limits on anomalous contributions to the Wtb couplings.
    2012-05Journal article Open access Show more
  • SURVEYS ON VERNACULAR ARCHITECTURE. THEIR SIGNIFICANCE IN 20TH CENTURY ARCHITECTURAL CULTURE. Conference Proceedings
    Publication . AAVV
    A survey on vernacular architecture, entitled Inquérito à Arquitectura Regional Portuguesa [Survey on Regional Architecture in Portugal] was promoted by the Architects’ Union between 1955 and 1960. It benefited from official government support and was conducted by some of the main modern architects. It come out as a two volume book – Popular Architecture in Portugal– published in 1961 and reprinted in 1979, 1988 and 2004. Taken from the outset as being able to provide “the basis for an honest, active and healthy regionalism” (Keil do Amaral, 1947), the Survey, and the book it prompted, had great influence on Portuguese architectural culture. As it was accomplished in an historical turning point, when some of the principles of Modern Movement were being critically reviewed both nationally and internationally, the Survey’s outcomes encouraged modern architects to recover national history and tradition. Moreover, the Portuguese Survey on vernacular architecture constitutes a remarkable register of the ancient rural country at the exact moment it was about to disappear. This fact would also guarantee its importance to other fields of study, such as anthropology, history, and photography. In association with an ongoing research project Popular Architecture in Portugal. A critical look, this conference aims to discuss the background, conditions, methodologies, published results, effects and the significance of such kind of surveys in the 20th century architecture and architectural thought, and be able to understand the Portuguese case in the international cultural context.
    2012-05Conference object Open access Show more
  • Our Project: the 'Popular Architecture in Portugal' A Critical Look. Intercalar Results of a Research Project
    Publication . MAIA, Maria Helena; CARDOSO, Alexandra; LEAL, Joana Cunha
    The research project we are developing is centered on the critical study of Popular Architecture in Portugal volume, published in 1961 by the Architects’ Union. This subject was chosen not only for the importance of the survey on which it is based for the history of Portuguese architectural culture, but also because we consider that the critical discussion prompted by the survey maintains its relevance unaltered, now that the debates on vernacular and regionalism have re-entered the agenda of professional debates. Even so, Popular Architecture in Portugal is not being study in isolation, in and for itself. Instead, we chose to study it within a pondered framework, dialoguing with theoretical elements underlying the expressiveness of some modern architectural erudite languages. Within this framework, Pedro Vieira de Almeida (2010) brought in two complementary key analytical variants of this project. He considered them as “parameters in sordina”: Firstly, the notion of the generic importance for architectural expression of greater or lesser degree of thickness of the walls, shaping what might be called a poetics of thin walls on the one hand, and a poetics of thick walls on the other. Secondly, the notion of transition-space’s architectural expressiveness key significance. This paper aims to present the current state of our research project, bringing its core working lines and results into discussion.
    2012-05Conference object Open access Show more
  • Maritimidade e continentalidade: o Portugal híbrido
    Publication . Manuelito, Ana Cláudia
    2012-05Journal article Open access Show more
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