Observation of the Ξb0 baryon
Physical Review Letters 107:10 (2011)
Abstract:
The observation of the bottom, strange baryon Ξb0 through the decay chain Ξb0→Ξc+π-, where Ξc+→Ξ -π+π+, Ξ -→Λπ-, and Λ→pπ-, is reported by using data corresponding to an integrated luminosity of 4.2fb-1 from pp̄ collisions at √s=1.96TeV recorded with the Collider Detector at Fermilab. A signal of 25.3-5.4+5.6 candidates is observed whose probability of arising from a background fluctuation is 3.6×10-12, corresponding to 6.8 Gaussian standard deviations. The Ξb0 mass is measured to be 5787.8±5.0(stat)±1.3(syst)MeV/ c2. In addition, the Ξb- baryon is observed through the process Ξb-→Ξc0π-, where Ξc0→Ξ -π+, Ξ-→Λπ-, and Λ→pπ-. © 2011 American Physical Society.Search for three-jet resonances in pp collisions at √s=7TeV
Physical Review Letters 107:10 (2011)
Abstract:
A search for three-jet hadronic resonance production in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35pb-1. Events with high jet multiplicity and a large scalar sum of jet transverse momenta are analyzed using a signature-based approach. The number of expected standard model background events is found to be in good agreement with the observed events. Limits on the cross section times branching ratio are set in a model of gluino pair production with an R-parity-violating decay to three quarks, and the data rule out such particles within the mass range of 200 to 280GeV/c2. © 2011 American Physical Society.Measurement of the t-channel single top quark production cross section in pp collisions at √s=7TeV
Physical Review Letters 107:9 (2011)
Abstract:
Electroweak production of the top quark is measured for the first time in pp collisions at √s=7TeV, using a data set collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36pb-1. With an event selection optimized for t-channel production, two complementary analyses are performed. The first one exploits the special angular properties of the signal, together with background estimates from the data. The second approach uses a multivariate analysis technique to probe the compatibility with signal topology expected from electroweak top-quark production. The combined measurement of the cross section is 83.6±29.8(stat+syst)±3.3(lumi) pb, consistent with the standard model expectation. © 2011 CERN.Branching fractions for γ(3S)→π0hb and ψ(2S)→πp0hc
Physical Review D - Particles, Fields, Gravitation and Cosmology 84:3 (2011)
Abstract:
Using e+e- collision data corresponding to 5.88×106γ(3S) [25.9×106ψ(2S)] decays and acquired by the CLEO III [CLEO-c] detectors operating at the Cornell Electron Storage Ring, we study the single-pion transitions from γ(3S)[ψ(2S)] to the respective spin-singlet states hb[c]. Utilizing only the momentum of suitably selected transition-π0 candidates, we obtain the upper limit B(γ(3S)→π0h b)<1.2×10-3 at 90% confidence level, and measure B(ψ(2S)→π0hc)=(9.0±1.5±1.3) ×10-4. Signal sensitivities are enhanced by excluding very asymmetric π0→γγ candidates. © 2011 American Physical Society.Measurement of the t t-bar Production Cross Section in pp Collisions at 7 TeV in Lepton + Jets Events Using b-quark Jet Identification
ArXiv 1108.3773 (2011)