Search for First-Generation Scalar Leptoquarks in $\bm{p \bar{p}}$ collisions at $\sqrt{s}$=1.96 TeV
ArXiv hep-ex/0506074 (2005)
Abstract:
We report on a search for pair production of first-generation scalar leptoquarks ($LQ$) in $p \bar{p}$ collisions at $\sqrt{s}$=1.96 TeV using an integrated luminosity of 203 $pb^{-1}$ collected at the Fermilab Tevatron collider by the CDF experiment. We observe no evidence for $LQ$ production in the topologies arising from $LQ \bar{LQ} \to eqeq$ and $LQ \bar{LQ} \to eq νq$, and derive 95% C.L. upper limits on the $LQ$ production cross section. %as a function of $β$, where $β$ is the branching fraction for $LQ \to eq$. The results are combined with those obtained from a separately reported CDF search in the topology arising from $LQ\bar{LQ} \to νq νq$ and 95% C.L. lower limits on the LQ mass as a function of $β= BR(LQ \to eq) $ are derived. The limits are 236, 205 and 145 GeV/c$^2$ for $β$ = 1, $β$ = 0.5 and $β$ = 0.1, respectively.Measurement of the W+W- production cross section in pp̄ collisions at s=1.96TeV using dilepton events
Physical Review Letters 94:21 (2005)
Abstract:
We present a measurement of the W+W- production cross section using 184pb-1 of pp̄ collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W-→ℓ+νℓ-ν̄, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0-0.8+2.2 events. The resulting W+W- production cross-section measurement of σ(pp̄→W+W-)=14.6-5.1+5.8(stat)-3.0+1.8(syst) ±0.9(lum)pb agrees well with the standard model expectation. © 2005 The American Physical Society.Measurement of charged-particle multiplicities in gluon and quark jets in pp̄ collisions at √s = 1:8 TeV
Physical Review Letters 94:17 (2005)
Abstract:
We report the first largely model independent measurement of charged particle multiplicities in quark and gluon jets, NMeasurements of bottom-antibottom azimuthal production correlations in proton-antiproton collisions at s=1.8TeV
Physical Review D Particles Fields Gravitation and Cosmology 71:9 (2005) 1-39
Abstract:
We have measured the azimuthal angular correlation of bb̄ production, using 86.5pb-1 of data collected by Collider Detector at Fermilab (CDF) in pp̄ collisions at s=1.8TeV during 1994-1995. In high-energy pp̄ collisions, such as at the Tevatron, bb̄ production can be schematically categorized into three mechanisms. The leading-order (LO) process is "flavor creation," where both b and b̄ quarks substantially participate in the hard scattering and result in a distinct back-to-back signal in final state. The "flavor excitation" and the "gluon splitting" processes, which appear at next-leading-order (NLO), are known to make a comparable contribution to total bb̄ cross section, while providing very different opening angle distributions from the LO process. An azimuthal opening angle between bottom and antibottom, Δ, has been used for the correlation measurement to probe the interaction creating bb̄ pairs. The Δ distribution has been obtained from two different methods. One method measures the Δ between bottom hadrons using events with two reconstructed secondary vertex tags. The other method uses bb̄→(J/ ψX)(X′) events, where the charged lepton () is an electron (e) or a muon (μ), to measure Δ between bottom quarks. The bb̄ purity is determined as a function of Δ by fitting the decay length of the J/ψ and the impact parameter of the. Both methods quantify the contribution from higher-order production mechanisms by the fraction of the bb̄ pairs produced in the same azimuthal hemisphere, ftoward. The measured ftoward values are consistent with both parton shower Monte Carlo and NLO QCD predictions. © 2005 The American Physical Society.Measurement of the lifetime difference between Bs mass eigenstates.
Phys Rev Lett 94:10 (2005) 101803