Professor Daniela Bortoletto

Abstract:

A search for a new heavy gauge boson W′ decaying to an electron or muon, plus a low mass neutrino, is presented. This study uses data corresponding to an integrated luminosity of 5.0 fb-1, collected using the CMS detector in pp collisions at a centre-of-mass energy of 7 TeV at the LHC. Events containing a single electron or muon and missing transverse momentum are analyzed. No significant excess of events above the standard model expectation is found in the transverse mass distribution of the lepton-neutrino system, and upper limits for cross sections above different transverse mass thresholds are presented. W′ Mass exclusion limits at 95% CL for a range of W′ models are determined, including a limit of 2.5 TeV for right-handed W bosons with standard-model-like couplings and limits W′ 2.43-2.63 TeV for left-handed W′ bosons, taking into account their interference with the standard model W boson. Exclusion limits have also been set on Kaluza-Klein WKK states in the framework of split universal extra dimensions. © 2012 SISSA.

Abstract:

A search for microscopic black holes in pp collisions at a center-of-mass energy of 7TeV is presented. The data sample corresponds to an integrated luminosity of 4.7 fb1 recorded by the CMS experiment at the LHC in 2011. Events with large total transverse energy have been analyzed for the presence of multiple energetic jets, leptons, and photons, which are typical signals of evaporating semiclassical and quantum black holes, and string balls. Agreement with the expected standard model backgrounds, which are dominated by QCD multijet production, has been observed for various combined multiplicities of jets and other reconstructed objects in the final state. Model-independent limits are set on new physics processes producing high-multiplicity, energetic final states. In addition, new model-specific indicative limits are set excluding semiclassical and quantum black holes with masses below 3.8 to 5.3TeV and string balls with masses below 4.6 to 4.8TeV . The analysis has a substantially increased sensitivity compared to previous searches.

Abstract:

A search for new physics is performed using isolated same-sign dileptons with at least two b-quark jets in the final state. Results are based on a 4.98 fb-1 sample of protonproton collisions at a centre-of-mass energy of 7TeV collected by the CMS detector. No excess above the standard model background is observed. Upper limits at 95% confidence level are set on the number of events from non-standard-model sources. These limits are used to set constraints on a number of new physics models. Information on acceptance and efficiencies are also provided so that the results can be used to confront additional models in an approximate way. © 2012 SISSA.

Abstract:

A search for quark compositeness using dijet angular distributions from pp collisions at √s = 7 TeV is presented. The search has been carried out using a data sample corresponding to an integrated luminosity of 2.2 fb -1, recorded by the CMS experiment at the LHC. Normalized dijet angular distributions have been measured for dijet invariant masses from 0.4 TeV to above 3TeV and compared with a variety of contact interaction models, including those which take into account the effects of next-to-leading-order QCD corrections. The data are found to be in agreement with the predictions of perturbative QCD, and lower limits are obtained on the contact interaction scale, ranging from 7.5 up to 14.5 TeV at 95% confidence level. © CERN.