Search for production of heavy particles decaying to top quarks and invisible particles in pp collisions at √s = 1.96 TeV.
Phys Rev Lett 106:19 (2011) 191801
Abstract:
We present a search for a new particle T' decaying to top quark via T' → t + X, where X is an invisible particle. In a data sample with 4.8 fb(-1) of integrated luminosity collected by the CDF II detector at Fermilab in pp collisions with √s = 1.96 TeV, we search for pair production of T' in the lepton + jets channel, pp → tt + X + X → ℓνbqq'b + X + X. We interpret our results primarily in terms of a model where T' are exotic fourth generation quarks and X are dark matter particles. Current direct and indirect bounds on such exotic quarks restrict their masses to be between 300 and 600 GeV/c2, the dark matter particle mass being anywhere below m(T'). The data are consistent with standard model expectations, and we set 95% confidence level limits on the generic production of T'T' → tt + X + X. For the dark matter model we exclude T' at 95% confidence level up to m(T') = 360 GeV/c2 for m(X) ≤ 100 GeV/c2.Measurements of direct CP violating asymmetries in charmless decays of strange bottom mesons and bottom baryons.
Phys Rev Lett 106:18 (2011) 181802
Abstract:
We report measurements of direct CP-violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using a data sample corresponding to 1 fb(-1) of integrated luminosity, we obtain the first measurements of direct CP violation in bottom strange mesons, A(CP)(B(s)(0)→K(-)π(+))=+0.39±0.15(stat)±0.08(syst), and bottom baryons, A(CP)(Λ(b)(0)→pπ(-))=+0.03±0.17(stat)±0.05(syst) and A(CP)(Λ(b)(0)→pK(-))=+0.37±0.17(stat)±0.03(syst). In addition, we measure CP violation in B(0)→K(+)π(-) decays with 3.5σ significance, A(CP)(B(0)→K(+)π(-))=-0.086±0.023(stat)±0.009(syst), in agreement with the current world average. Measurements of branching fractions of B(s)(0)→K(+)K(-) and B(0)→π(+)π(-) decays are also updated.Invariant mass distribution of jet pairs produced in association with a W boson in pp collisions at sqrt[s]=1.96 TeV.
Phys Rev Lett 106:17 (2011) 171801
Abstract:
We report a study of the invariant mass distribution of jet pairs produced in association with a W boson using data collected with the CDF detector which correspond to an integrated luminosity of 4.3 fb(-1). The observed distribution has an excess in the 120-160 GeV/c(2) mass range which is not described by current theoretical predictions within the statistical and systematic uncertainties. In this Letter, we report studies of the properties of this excess.Measurement of the top quark mass in the lepton+jets channel using the lepton transverse momentum
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 698:5 (2011) 371-379
Abstract:
This Letter reports a measurement of the top quark mass, Mtop, in data from pp- collisions at s=1.96 TeV corresponding to 2.7 fb-1 of integrated luminosity at the Fermilab Tevatron using the CDF II detector. Events with the lepton+jets topology are selected. An unbinned likelihood is constructed based on the dependence of the lepton transverse momentum, PT, on Mtop. A maximum likelihood fit to the data yields a measured mass Mtop=176.9±8.0stat±2.7syst GeV/c2. In this measurement, the contribution by the jet energy scale uncertainty to the systematic error is negligible. The result provides an important consistency test for other Mtop measurements where explicit use of the jet energy is made for deriving the top quark mass. © 2011 Elsevier B.V.Measurement of the forward-backward asymmetry in the B→K(*) μ+μ- decay and first observation of the Bs0→μ+μ- decay
Physical Review Letters 106:16 (2011)