Giuseppe Della Ricca

Measurement of differential top-quark pair production cross sections in pp collisions at sqrt(s) = 7 TeV

Normalised differential top-quark-pair production cross sections are measured in pp collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector using data recorded in 2011 corresponding to an integrated luminosity of 5.0 fb−1. The measurements are performed in the lepton+jets decay channels (e+jets and μ+jets) and the dilepton decay channels (e+e−, μ+μ−, and μ±e∓). The tt differential cross section is measured as a function of kinematic properties of the final-state charged leptons and jets associated to b quarks, as well as those of the top quarks and the tt system. The data are compared with several predictions from perturbative QCD calculations up to approximate next-to-next-to-leading-order precision. No significant deviations from the standard model are observed. Submitted to the European Physical Journal C c

Data quality monitoring for the CMS electromagnetic calorimeter

The detector performance of the CMS electromagnetic calorimeter is monitored using applications based on the CMS Data Quality Monitoring (DQM) framework and running on the High-Level Trigger Farm as well as on local DAQ systems. The monitorable quantities are organized into hierarchical structures based on the physics content. The information produced is accessible by client applications according to their subscription requests. The client applications process the received quantities, according to pre-defined analyses, making the results immediately available, while also storing the results in a database, and in the form of static web pages, for subsequent studies. We describe here the functionalities of the CMS ECAL DQM applications and report about their use in real environments.

Measurements of the Y(1S), Y(2S), and Y(3S) differential cross sections in pp collisions at sqrt(s) = 7 TeV

Differential cross sections as a function of transverse momentum pT are presented for the production of Υ(nS) (n = 1, 2, 3) states decaying into a pair of muons. Data corresponding to an integrated luminosity of 4.9 fb−1 in pp collisions at √ s = 7 TeV were collected with the CMS detector at the LHC. The analysis selects events with dimuon rapidity |y| < 1.2 and dimuon transverse momentum in the range 10 < pT < 100 GeV. The measurements show a transition from an exponential to a powerlaw behavior at pT ≈ 20 GeV for the three Υ states. Above that transition, the Υ(3S) spectrum is significantly harder than that of the Υ(1S) and Υ(2S). The ratios of the Υ(3S) and Υ(2S) differential cross sections to the Υ(1S) cross section show a rise as pT increases at low pT, then become flatter at higher pT. Submitted to Physics Letters B c

Search for supersymmetry in hadronic final states with missing transverse energy using the variables alphaT and b-quark multiplicity in pp collisions at sqrt(s) = 8 TeV

An inclusive search for supersymmetric processes that produce final states with jets and missing transverse energy is performed in pp collisions at a centre-of-mass energy of 8 TeV. The data sample corresponds to an integrated luminosity of 11.7 fb−1 collected by the CMS experiment at the LHC. In this search, a dimensionless kinematic variable, αT, is used to discriminate between events with genuine and misreconstructed missing transverse energy. The search is based on an examination of the number of reconstructed jets per event, the scalar sum of transverse energies of these jets, and the number of these jets identified as originating from bottom quarks. No significant excess of events over the standard model expectation is found. Exclusion limits are set in the parameter space of simplified models, with a special emphasis on both compressed-spectrum scenarios and direct or gluino-induced production of third-generation squarks. For the case of gluino-mediated squark production, gluino masses up to 950–1125 GeV are excluded depending on the assumed model. For the direct pair-production of squarks, masses up to 450 GeV are excluded for a single light first- or second-generation squark, increasing to 600 GeV for bottom squarks.

Performance of the CMS Electromagnetic Calorimeter at the LHC

The CMS Electromagnetic Calorimeter (ECAL) is a high resolution, fine-grained calorimeter devised to measure photons and electrons at the LHC. Built of lead tungstate crystals, it plays a crucial role in the search for new physics as well as in precision measurements of the Standard Model. A preshower detector composed of sandwiches of lead and silicon strips improves π0/γ separation in the forward region. The operation and performance of the ECAL during the 2010 run at the LHC, with pp collisions at √s = 7 TeV will be reviewed, and to some extent for the 2011 running as well. Pure samples of electrons and photons from decays of known resonances have been exploited to improve and verify the trigger efficiency, the reconstruction algorithms, the detector calibration and stability, and the particle identification efficiency. A review of these aspects will be given.

Measurements of charged current lepton universality and |Vus| using tau lepton decays to e- nu-bar_e nu_tau, mu- nu-bar_mu nu_tau, pi- nu_tau, and K- nu_tau

Using 467 fb(-1) of e(+)e(-) annihilation data collected with the BABAR detector, we measure B(tau(-)->mu(-)(nu) over bar (mu)nu(tau))/B(tau(-)-> e(-)(nu) over bar (e)nu(tau)) = (0.9796 +/- 0.0016 +/- 0.0036), B(tau(-)->pi(-)nu(tau))/B(tau(-)-> e(-)nu(e)nu(tau)) = (0.5945 +/- 0.0014 +/- 0.0061), and B(tau(-)-> K-nu(tau))/B(tau(-)-> e(-)nu(e)nu(tau)) = (0.03882 +/- 0.00032 +/- 0.00057), where the uncertainties are statistical and systematic, respectively. From these precision similar to measurements, we test the standard model assumption of mu - e and tau - mu charge current lepton universality and provide determinations of vertical bar V-us vertical bar experimentally independent of the decay of a kaon.

Search for CP violation using T-odd correlations in D0 -> K+K-pi+pi- decays

We search for CP violation in a sample of

Search for B+ -> l+ nu_l recoiling against B- -> D0 l-nu-bar X

4.7\times10^4

Observation of the decay B0-bar -> Lambda_c+ p-bar pi0

Cabibbo-suppressed

The CMS ECAL database services for detector control and monitoring

D^0 \to K^+ K^- \pi^+ \pi^-