[Show abstract][Hide abstract] ABSTRACT: Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top quark (the top squark) and the Higgs boson (Higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7 fb-1 of proton-proton collision data at s=8 TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the top squark mass below 360 to 410 GeV, depending on the Higgsino mass.
[Show abstract][Hide abstract] ABSTRACT: Results are presented from a search for the production of a heavy gauge boson
W' decaying into a top and a bottom quark, using a data set collected by the
CMS experiment at sqrt(s)=8 TeV and corresponding to an integrated luminosity
of 19.5 inverse femtobarns. Various models of W'-boson production are studied
by allowing for an arbitrary combination of left- and right-handed couplings.
The analysis is based on the detection of events with a lepton (e, mu), jets,
and missing transverse energy in the final state. No evidence for W'-boson
production is found and 95% confidence level upper limits on the production
cross section times branching fraction are obtained. For W' bosons with purely
right-handed couplings, and for those with left-handed couplings assuming no
interference effects, the observed 95% confidence level limit is M(W')>2.05
TeV. For W' bosons with purely left-handed couplings, including interference
effects, the observed 95% confidence level limit is M(W')>1.84 TeV. The results
presented in this paper are the most stringent limits published to date.
[Show abstract][Hide abstract] ABSTRACT: The production of jets associated to bottom quarks is measured for the first
time in PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon
pair. Jet spectra are reported in the transverse momentum (pt) range of 80-250
GeV, and within pseudorapidity abs(eta < 2). The nuclear modification factor
(R[AA]) calculated from these spectra shows a strong suppression in the b-jet
yield in PbPb collisions relative to the yield observed in pp collisions at the
same energy. The suppression persists to the largest values of pt studied, and
is centrality dependent. The R[AA] is about 0.4 in the most central events,
similar to previous observations for inclusive jets. This implies that jet
quenching does not have a strong dependence on parton mass and flavor in the
jet pt range studied.
[Show abstract][Hide abstract] ABSTRACT: A search for flavor-changing neutral currents in top-quark decays t to Zq is
performed in events produced from the decay chain t t-bar to Zq+Wb, where both
vector bosons decay leptonically, producing a final state with three leptons
(electrons or muons). A dataset collected with the CMS detector at the LHC is
used, corresponding to an integrated luminosity of 19.7 inverse femtobarns of
proton-proton collisions at a center-of-mass energy of 8 TeV. No excess is seen
in the observed number of events relative to the standard model prediction;
thus no evidence for flavor-changing neutral currents in top-quark decays is
found. A combination with a previous search at 7 TeV excludes a t to Zq
branching fraction greater than 0.05% at the 95% confidence level.