Professor Daniela Bortoletto

Abstract:

A search is presented for the standard model Higgs boson produced in association with top quarks using the full Run II proton-antiproton collision data set, corresponding to 9.45fb-1, collected by the Collider Detector at Fermilab. No significant excess over the expected background is observed, and 95% credibility-level upper bounds are placed on the cross section σ(tt̄H→lepton+missing transverse energy+jets). For a Higgs boson mass of 125GeV/c2, we expect to set a limit of 12.6 and observe a limit of 20.5 times the standard model rate. This represents the most sensitive search for a standard model Higgs boson in this channel to date. © 2012 American Physical Society.

Abstract:

Spectra of identified charged hadrons are measured in pp collisions at the LHC for √s = 0.9,2.76, and 7 TeV. Charged pions, kaons, and protons in the transverse-momentum range pT≈0. 1-1. 7 GeV/c and for rapidities {pipe}y{pipe}<1 are identified via their energy loss in the CMS silicon tracker. The average pT increases rapidly with the mass of the hadron and the event charged-particle multiplicity, independently of the center-of-mass energy. The fully corrected pT spectra and integrated yields are compared to various tunes of the Pythia 6 and Pythia 8 event generators. © 2012 CERN for the benefit of the CMS collaboration.

Abstract:

An inclusive search for the standard model Higgs boson using the four-lepton final state in proton-antiproton collisions produced by the Tevatron at √s=1.96TeV is conducted. The data are recorded by the CDF II detector and correspond to an integrated luminosity of 9.7fb -1. Three distinct Higgs decay modes, namely ZZ, WW, and ττ, are simultaneously probed. Nine potential signal events are selected and found to be consistent with the background expectation. We set a 95% credibility limit on the production cross section times the branching ratio and subsequent decay to the four-lepton final state for hypothetical Higgs boson masses between 120GeV/c2 and 300GeV/c2. © 2012 American Physical Society.

Abstract:

A search is presented for charge-asymmetric production of a W' boson that has been proposed to accommodate the forward-backward asymmetry observed in the production of top-antitop quark pairs at the Tevatron. The new heavy W' boson would be produced in association with a top quark and would decay into top and down quarks. The data correspond to an integrated luminosity of 5.0 fb-1 in pp collisions at a center-of-mass energy of 7 TeV, recorded by the CMS detector at the LHC. No significant excess above the standard model expectations is observed, and, from a combination of the electron-plus-jets and muon-plus-jets channels, a 95% confidence level lower limit of 840 GeV/c2 is set on the W' boson mass for a W' boson model with values for coupling constants to top and down quarks gL=0 and gR=2. In addition, a kinematic reconstruction of the W' resonance mass using the inherent charge asymmetry of this model finds no indication of the presence of W' events in the data. © 2012 CERN.