Professor Daniela Bortoletto

Abstract:

The angular distributions and the differential branching fraction of the decay B0→K*(892)0μ+μ- are studied using a data sample corresponding to an integrated luminosity of 5.2fb-1 collected with the CMS detector at the LHC in pp collisions at s=7TeV. From more than 400 signal decays, the forward-backward asymmetry of the muons, the K*(892)0 longitudinal polarization fraction, and the differential branching fraction are determined as a function of the square of the dimuon invariant mass. The measurements are in good agreement with standard model predictions. © 2013 CERN.

Abstract:

The Υ(1S), Υ(2S), and Υ(3S) production cross sections are measured using a data sample corresponding to an integrated luminosity of 35.8±1.4pb-1 of proton-proton collisions at s=7TeV, collected with the CMS detector at the LHC. The Υ resonances are identified through their decays to dimuons. Integrated over the Υ transverse momentum range pTΥ<50GeV/c and rapidity range |yΥ|<2.4, and assuming unpolarized Υ production, the products of the Υ production cross sections and dimuon branching fractions areσ(pp→Υ(1S)X)B(Υ(1S)→μ+μ-)=(8.55 0.05-0.50+0.56±0.34)nb,σ(pp→Υ(2S)X)B(Υ(2S) →μ+μ-)=(2.21±0.03-0.14+0.16±0.09)nb,σ(pp→Υ(3S)X)B(Υ(3S)→μ+μ-)=(1.11±0.02-0.08+0. 10±0.04)nb, where the first uncertainty is statistical, the second is systematic, and the third is from the uncertainty in the integrated luminosity. The differential cross sections in bins of transverse momentum and rapidity, and the cross section ratios are presented. Cross section measurements performed within a restricted muon kinematic range and not corrected for acceptance are also provided. These latter measurements are independent of Υ polarization assumptions. The results are compared to theoretical predictions and previous measurements. © 2013 CERN.

Abstract:

The results of a search for the bottomonium counterpart, denoted as Xb, of the exotic charmonium state X(3872) is presented. The analysis is based on a sample of pp collisions at s=8 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 20.7 fb-1. The search looks for the exclusive decay channel Xb→Υ{hooked}(1S)π+π- followed by Υ{hooked}(1S)→μ+μ-. No evidence for an Xb signal is observed. Upper limits are set at the 95% confidence level on the ratio of the inclusive production cross sections times the branching fractions to Υ{hooked}(1S)π+π- of the Xb and the Υ{hooked}(2S). The upper limits on the ratio are in the range 0.9-5.4% for Xb masses between 10 and 11 GeV. These are the first upper limits on the production of a possible Xb at a hadron collider. © 2013 CERN.

Abstract:

A search for anomalous production of events with three or more isolated leptons and bottom-quark jets produced in pp collisions at √s=8 TeV is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 19.5 fb-1 collected by the CMS experiment at the LHC in 2012. No excess above the standard model expectations is observed. The results are interpreted in the context of supersymmetric models with signatures that have low missing transverse energy arising from light top-squark pair production with R-parity-violating decays of the lightest supersymmetric particle. In two models with different R-parity-violating couplings, top squarks are excluded below masses of 1020 GeV and 820 GeV when the lightest supersymmetric particle has a mass of 200 GeV. © 2013 CERN.