Search for long-lived particles that decay into final states containing two electrons or two muons in proton-proton collisions at √s=8TeV
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AuthorKhachatryan, Vladimir; Brochero Cifuentes, Javier Andrés; Cabrillo Bartolomé, José Iban; Calderón Tazón, Alicia; Duarte Campderros, Jorge; Fernández García, Marcos; Gómez Gramuglio, Gervasio; Graziano, Alberto; López Virto, María Amparo; Marco de Lucas, Jesús; Marco de Lucas, Rafael José; Martínez Rivero, Celso; Matorras Weinig, Francisco; Muñoz Sánchez, Francisca Javiela; Piedra Gómez, Jonatan; Rodrigo Anoro, Teresa; Rodríguez Marrero, Ana Yaiza; Ruiz Jimeno, Alberto; Scodellaro, Luca; [et al.]
A search is performed for long-lived particles that decay into final states that include a pair of electrons or a pair of muons. The experimental signature is a distinctive topology consisting of a pair of charged leptons originating from a displaced secondary vertex. Events corresponding to an integrated luminosity of 19.6 (20.5) fb−1 in the electron (muon) channel were collected with the CMS detector at the CERN LHC in proton-proton collisions at √s=8 TeV. No significant excess is observed above standard model expectations. Upper limits on the product of the cross section and branching fraction of such a signal are presented as a function of the long-lived particle’s mean proper decay length. The limits are presented in an approximately model-independent way, allowing them to be applied to a wide class of models yielding the above topology. Over much of the investigated parameter space, the limits obtained are the most stringent to date. In the specific case of a model in which a Higgs boson in the mass range 125–1000 GeV/c2 decays into a pair of long-lived neutral bosons in the mass range 20–350 GeV/c2, each of which can then decay to dileptons, the upper limits obtained are typically in the range 0.2–10 fb for mean proper decay lengths of the long-lived particles in the range 0.01–100 cm. In the case of the lowest Higgs mass considered (125 GeV/c2), the limits are in the range 2–50 fb. These limits are sensitive to Higgs boson branching fractions as low as 10−4.