8 research outputs found

    Search for electroweak production of charginos in final states with two tau leptons in pp collisions at root s=8 TeV

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    Results are presented from a search for the electroweak production of supersymmetric particles in pp collisions in final states with two T leptons. The data sample corresponds to an integrated luminosity between 18.1 fb(-1) and 19.6 fb(-1) depending on the final state of T lepton decays, at root s = 8 TeV, collected by the CMS experiment at the LHC. The observed event yields in the signal regions are consistent with the expected standard model backgrounds. The results are interpreted using simplified models describing the pair production and decays of charginos or T sleptons. For models describing the pair production of the lightest chargino, exclusion regions are obtained in the plane of chargino mass vs. neutralino mass under the following assumptions: the chargino decays into third-generation sleptons, which are taken to be the lightest sleptons, and the sleptons masses lie midway between those of the chargino and the neutralino. Chargino masses below 420 GeV are excluded at a 95% confidence level in the limit of a massless neutralino, and for neutralino masses up to 100 GeV, chargino masses up to 325 GeV are excluded at 95% confidence level. Constraints are also placed on the cross section for pair production of T sleptons as a function of mass, assuming a massless neutralino.Peer reviewe

    Search for associated production of a Z boson with a single top quark and for tZ flavour-changing interactions in pp collisions at root s=8 TeV

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    A search for the production of a single top quark in association with a Z boson is presented, both to identify the expected standard model process and to search for flavour-changing neutral current interactions. The data sample corresponds to an integrated luminosity of 19.7 fb−1 recorded by the CMS experiment at the LHC in proton-proton collisions at s√=8s=8 TeV. Final states with three leptons (electrons or muons) and at least one jet are investigated. An events yield compatible with tZq standard model production is observed, and the corresponding cross section is measured to be σ(pp → tZq → ℓνbℓ+ℓ−q) = 10− 7+ 8 fb with a significance of 2.4 standard deviations. No presence of flavour-changing neutral current production of tZq is observed. Exclusion limits at 95% confidence level on the branching fractions of a top quark decaying to a Z boson and an up or a charm quark are found to be ℬ(t → Zu) < 0.022% and ℬ(t → Zc) < 0.049%

    Search for third-generation scalar leptoquarks and heavy right-handed neutrinos in final states with two tau leptons and two jets in proton-proton collisions at sqrt(s)=13 TeV

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    A search is performed for third-generation scalar leptoquarks and heavy right-handed neutrinos in events containing one electron or muon, one hadronically decaying τ lepton, and at least two jets, using a s=13 TeV pp collision data sample corresponding to an integrated luminosity of 12.9 fb-1collected with the CMS detector at the LHC in 2016. The number of observed events is found to be in agreement with the standard model prediction. A limit is set at 95% confidence level on the product of the leptoquark pair production cross section and β2, where β is the branching fraction of leptoquark decay to a τ lepton and a bottom quark. Assuming β = 1, third-generation leptoquarks with masses below 850 GeV are excluded at 95% confidence level. An additional search based on the same event topology involves heavy right-handed neutrinos, NR, and right-handed W bosons, WR, arising in a left-right symmetric extension of the standard model. In this search, WRbosons are assumed to decay to a tau lepton and NRfollowed by the decay of the NRto a tau lepton and an off-shell WRboson. Assuming the mass of the right-handed neutrino to be half of the mass of the right-handed W boson, WRboson masses below 2.9 TeV are excluded at 95% confidence level. These results improve on the limits from previous searches for third-generation leptoquarks and heavy right-handed neutrinos with τ leptons in the final state.[Figure not available: see fulltext.]

    Search for third-generation scalar leptoquarks and heavy right-handed neutrinos in final states with two tau leptons and two jets in proton-proton collisions at √s=13 TeV

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    A search is performed for third-generation scalar leptoquarks and heavy right-handed neutrinos in events containing one electron or muon, one hadronically decaying τ lepton, and at least two jets, using a s√=13s=13 TeV pp collision data sample corresponding to an integrated luminosity of 12.9 fb-1 collected with the CMS detector at the LHC in 2016. The number of observed events is found to be in agreement with the standard model prediction. A limit is set at 95% confidence level on the product of the leptoquark pair production cross section and β2, where β is the branching fraction of leptoquark decay to a τ lepton and a bottom quark. Assuming β = 1, third-generation leptoquarks with masses below 850 GeV are excluded at 95% confidence level. An additional search based on the same event topology involves heavy right-handed neutrinos, NR, and right-handed W bosons, WR, arising in a left-right symmetric extension of the standard model. In this search, WR bosons are assumed to decay to a tau lepton and NR followed by the decay of the NR to a tau lepton and an off-shell WR boson. Assuming the mass of the right-handed neutrino to be half of the mass of the right-handed W boson, WR boson masses below 2.9 TeV are excluded at 95% confidence level. These results improve on the limits from previous searches for third-generation leptoquarks and heavy right-handed neutrinos with τ leptons in the final state

    Observation of gamma(1S) pair production in proton-proton collisions at root s=8 TeV

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    Search for s channel single top quark production in pp collisions at <tex>\sqrt{s}$</tex>=7 and 8 TeV

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    Search for direct pair production of scalar top quarks in the single- and dilepton channels in proton-proton collisions at root s=8 TeV

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    Search for electroweak production of charginos in final states with two T leptons in pp collisions at root s=8 TeV

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