Search for heavy toplike quarks using lepton plus jets events in 1.96 TeV pp̄ collisions
Physical Review Letters 100:16 (2008)
Abstract:
We present the results of a search for pair production of a new heavy toplike quark t′ decaying to a W boson and another quark using the Collider Detector at FermilabII detector in runII of the Tevatron pp̄ collider. Using a data sample corresponding to 760pb-1 of integrated luminosity, we fit the observed spectrum of total transverse energy and reconstructed t′ quark mass to a combination of standard model processes and t′ pair production. We see no evidence for t′t̄′ production, and we infer a lower limit of 256GeV/c2 on the mass of the t′ at 95% C.L. assuming standard strong couplings for the t′. © 2008 The American Physical Society.Measurement of ratios of fragmentation fractions for bottom hadrons in pp̄ collisions at s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 77:7 (2008)
Abstract:
This paper describes the first measurement of b-quark fragmentation fractions into bottom hadrons in Run II of the Tevatron Collider at Fermilab. The result is based on a 360pb-1 sample of data collected with the CDF II detector in pp̄ collisions at s=1.96TeV. Semileptonic decays of B̄0, B-, and B̄s0 mesons, as well as Λb0 baryons, are reconstructed. For an effective bottom hadron pT threshold of 7GeV/c, the fragmentation fractions are measured to be fu/fd=1.054±0.018(stat)-0.045+0.025(sys)±0. 058(B), fs/(fu+fd)=0.160±0.005(stat)-0.010+0.011(sys)-0.034+0.057(B), and fΛb/(fu+fd)=0.281±0.012(stat)-0.056+0.058(sys)-0.087+0.128(B), where the uncertainty B is due to uncertainties on measured branching ratios. The value of fs/(fu+fd) agrees within one standard deviation with previous CDF measurements and the world average of this quantity, which is dominated by LEP measurements. However, the ratio fΛb/(fu+fd) is approximately twice the value previously measured at LEP. The approximately 2σ discrepancy is examined in terms of kinematic differences between the two production environments. © 2008 The American Physical Society.Measurement of the forward-backward charge asymmetry in top-quark pair production.
Phys Rev Lett 100:14 (2008) 142002
Abstract:
We present the first measurement of the integrated forward-backward charge asymmetry in top-quark-top-antiquark pair (tt) production in proton-antiproton (pp) collisions in the lepton+jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming tt + X production and decay, a sample of 0.9 fb(-1) of data, collected by the D0 experiment at the Fermilab Tevatron Collider, is used to measure the asymmetry for different jet multiplicities. The result is also used to set upper limits on tt+X production via a Z' resonance.Measurement of the forward-backward charge asymmetry in top-quark pair production
Physical Review Letters 100:14 (2008)
Abstract:
We present the first measurement of the integrated forward-backward charge asymmetry in top-quark "top-antiquark pair (tt) production in proton-antiproton (pp) collisions in the lepton+jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming tt+X production and decay, a sample of 0.9 fb-1 of data, collected by the D0 experiment at the Fermilab Tevatron Collider, is used to measure the asymmetry for different jet multiplicities. The result is also used to set upper limits on tt+X production via a Z resonance. © 2008 The American Physical Society.Search for ZZ and Zgamma* production in pp[over ] collisions at square root s=1.96 TeV and limits on anomalous ZZZ and ZZgamma* couplings.
Phys Rev Lett 100:13 (2008) 131801