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  • Search for new phenomena in events with at least three photons collected in $pp$ collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector
    Publication . ATLAS collaboration (2866 authors); Aguilar-Saavedra, Juan Antonio; Amor Dos Santos, Susana Patricia; Anjos, Nuno; Araque, Juan Pedro; Cantrill, Robert; Carvalho, João; Castro, Nuno Filipe; Conde Muiño, Patricia; Da Cunha Sargedas De Sousa, Mario Jose; Fiolhais, Miguel; Galhardo, Bruno; Gomes, Agostinho; Gonçalo, Ricardo; Jorge, Pedro; Lopes, Lourenco; Machado Miguens, Joana; Maio, Amélia; Maneira, José; Onofre, António; Palma, Alberto; Pedro, Rute; Pina, João Antonio; Santos, Helena; Saraiva, João; Silva, José; Tavares Delgado, Ademar; Veloso, Filipe; Wolters, Helmut
    Results of a search for new phenomena in events with at least three photons are reported. Data from proton–proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb$^{-1}$ , were collected with the ATLAS detector at the LHC. The observed data are well described by the Standard Model. Limits at the 95 % confidence level on new phenomena are presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay $Z\rightarrow 3\gamma $ , as well as di-photon and tri-photon resonance searches. For a Standard Model Higgs boson decaying to four photons via a pair of intermediate pseudoscalar particles (a), limits are found to be $\sigma \times {\text{ BR }}(h \rightarrow aa) \times {\text{ BR }}(a \rightarrow \gamma \gamma )^{2} < 10^{-3} \sigma _{\text {SM}}$ for 10 GeV $< m_{a} <$ 62 GeV. Limits are also presented for Higgs boson-like scalars (H) for $m_{H} > $ 125 GeV, and for a $Z'$ decaying to three photons via $Z' \rightarrow a+\gamma \rightarrow 3\gamma $ . Additionally, the observed limit on the branching ratio of the Z boson decay to three photons is found to be BR $(Z \rightarrow 3\gamma ) < 2.2 \times 10^{-6}$ , a result five times stronger than the previous result from LEP.
    2016-04-16Journal article Open access Show more
  • A Promoção da Fluência da Leitura Através das Obras Literárias
    Publication . Cláudia Manuela Moreira Ribeiro Sampaio
    2016-04-16Master thesis Open access Show more