Publicação

Search for pair production of heavy top-like quarks decaying to a high-pT $W$ boson and a $b$ quark in the lepton plus jets final state at $\sqrt{s}$=7 TeV with the ATLAS detector

Detalhes bibliográficos
Resumo:	A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb^-1 of pp collisions at $\sqrt{s}$=7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton+jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t't'bar signal when mt'>=400 GeV. No significant excess of events above the Standard Model expectation is observed and the result of the search is interpreted in the context of fourth-generation and vector-like quark models. Under the assumption of a branching ratio BR(t'->Wb)=1, a fourth-generation t' quark with mass lower than 656 GeV is excluded at 95% confidence level. In addition, in light of the recent discovery of a new boson of mass ~126 GeV at the LHC, upper limits are derived in the two-dimensional plane of BR(t'->Wb) versus BR(t'->Ht), where H is the Standard Model Higgs boson, for vector-like quarks of various masses.
Autores principais:	ATLAS collaboration (2905 authors)
Outros Autores:	Aguilar-Saavedra, Juan Antonio; Amor Dos Santos, Susana Patricia; 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; Galhardo, Bruno; 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
Ano:	2013
País:	Portugal
Tipo de documento:	artigo
Tipo de acesso:	acesso aberto
Instituição associada:	Laboratório de Instrumentação e Física Experimental de Partículas
Idioma:	inglês
Origem:	Laboratório de Instrumentação e Física Experimental de Partículas

Descrição
Resumo:	A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb^-1 of pp collisions at $\sqrt{s}$=7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton+jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t't'bar signal when mt'>=400 GeV. No significant excess of events above the Standard Model expectation is observed and the result of the search is interpreted in the context of fourth-generation and vector-like quark models. Under the assumption of a branching ratio BR(t'->Wb)=1, a fourth-generation t' quark with mass lower than 656 GeV is excluded at 95% confidence level. In addition, in light of the recent discovery of a new boson of mass ~126 GeV at the LHC, upper limits are derived in the two-dimensional plane of BR(t'->Wb) versus BR(t'->Ht), where H is the Standard Model Higgs boson, for vector-like quarks of various masses.