Sneha Malde

Abstract:

We present a measurement of the top quark mass with tt̄ dilepton events produced in pp̄ collisions at the Fermilab Tevatron (s=1.96TeV) and collected by the CDF II detector. A sample of 328 events with a charged electron or muon and an isolated track, corresponding to an integrated luminosity of 2.9fb-1, are selected as tt̄ candidates. To account for the unconstrained event kinematics, we scan over the phase space of the azimuthal angles (ν1,ν2) of neutrinos and reconstruct the top quark mass for each ν1, ν2 pair by minimizing a χ2 function in the tt̄ dilepton hypothesis. We assign χ2-dependent weights to the solutions in order to build a preferred mass for each event. Preferred mass distributions (templates) are built from simulated tt̄ and background events, and parametrized in order to provide continuous probability density functions. A likelihood fit to the mass distribution in data as a weighted sum of signal and background probability density functions gives a top quark mass of 165.5-3.3+3.4(stat)±3. 1(syst)GeV/c2. © 2009 The American Physical Society.

Abstract:

We report a measurement of the top quark mass, mt, obtained from pp̄ collisions at s=1.96TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9fb-1. We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, where the matrix element is modified by using effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of mt and a parameter JES (jet energy scale) that determines in situ the calibration of the jet energies. We use a neural network discriminant to distinguish signal from background events. We also apply a cut on the peak value of each event likelihood curve to reduce the contribution of background and badly reconstructed events. Using the 318 events that pass all selection criteria, we find mt=172.7±1.8(stat+JES) ±1.2(syst)GeV/c2. © 2009 The American Physical Society.

Abstract:

We present a measurement of the top quark mass in the all hadronic channel (tt̄→bb̄q1q̄2q3q̄4) using 943pb-1 of pp̄ collisions at s=1.96TeV collected at the CDF II detector at Fermilab (CDF). We apply the standard model production and decay matrix element (ME) to tt̄ candidate events. We calculate per-event probability densities according to the ME calculation and construct template models of signal and background. The scale of the jet energy is calibrated using additional templates formed with the invariant mass of pairs of jets. These templates form an overall likelihood function that depends on the top quark mass and on the jet energy scale (JES). We estimate both by maximizing this function. Given 72 observed events, we measure a top quark mass of 171.1±3.7(stat+JES)±2.1(syst)GeV/c2. The combined uncertainty on the top quark mass is 4.3GeV/c2. © 2009 The American Physical Society.

Abstract:

We report on a search for inclusive production of squarks and gluinos in pp[over ] collisions at sqrt[s]=1.96 TeV, in events with large missing transverse energy and multiple jets of hadrons in the final state. The study uses a CDF Run II data sample corresponding to 2 fb(-1) of integrated luminosity. The data are in good agreement with the standard model predictions, giving no evidence for any squark or gluino component. In an R-parity conserving minimal supergravity scenario with A(0)=0, mu<0, and tanbeta=5, 95% C.L. upper limits on the production cross sections in the range between 0.1 and 1 pb are obtained, depending on the squark and gluino masses considered. For gluino masses below 280 GeV/c(2), arbitrarily large squark masses are excluded at the 95% C.L., while for mass degenerate gluinos and squarks, masses below 392 GeV/c(2) are excluded at the 95% C.L.

Abstract:

We report on a search for inclusive production of squarks and gluinos in pp̄ collisions at s=1.96TeV, in events with large missing transverse energy and multiple jets of hadrons in the final state. The study uses a CDF Run II data sample corresponding to 2fb-1 of integrated luminosity. The data are in good agreement with the standard model predictions, giving no evidence for any squark or gluino component. In an R-parity conserving minimal supergravity scenario with A0=0, μ<0, and tan β=5, 95 C.L. upper limits on the production cross sections in the range between 0.1 and 1 pb are obtained, depending on the squark and gluino masses considered. For gluino masses below 280GeV/c2, arbitrarily large squark masses are excluded at the 95 C.L., while for mass degenerate gluinos and squarks, masses below 392GeV/c2 are excluded at the 95 C.L. © 2009 The American Physical Society.