Zγ production and limits on anomalous ZZγ and Zγγ couplings in p over(p, ̄) collisions at sqrt(s) = 1.96 TeV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 653:5-6 (2007) 378-386
Abstract:
We present a study of eeγ and μμγ events using 1109 (1009) pb-1 of data in the electron (muon) channel, respectively. These data were collected with the DØ detector at the Fermilab Tevatron p over(p, ̄) collider at sqrt(s) = 1.96 TeV. Having observed 453 (515) candidates in the eeγ (μμγ) final state, we measure the Zγ production cross section for a photon with transverse energy ET > 7 GeV, separation between the photon and leptons Δ Rℓ γ > 0.7, and invariant mass of the di-lepton pair Mℓ ℓ > 30 GeV / c2, to be 4.96 ± 0.30 (stat . + syst .) ± 0.30 (lumi .) pb, in agreement with the Standard Model prediction of 4.74 ± 0.22 pb. This is the most precise Zγ cross section measurement at a hadron collider. We set limits on anomalous trilinear Zγγ and ZZγ gauge boson couplings of - 0.085 < h30γ < 0.084, - 0.0053 < h40γ < 0.0054 and - 0.083 < h30Z < 0.082, - 0.0053 < h40Z < 0.0054 at the 95% C.L. for the form-factor scale Λ = 1.2 TeV.Search for stopped gluinos from pp̄ collisions at s=1.96TeV
Physical Review Letters 99:13 (2007)
Abstract:
Long-lived, heavy particles are predicted in a number of models beyond the standard model of particle physics. We present the first direct search for such particles' decays, occurring up to 100 h after their production and not synchronized with an accelerator bunch crossing. We apply the analysis to the gluino (g), predicted in split supersymmetry, which after hadronization can become charged and lose enough momentum through ionization to come to rest in dense particle detectors. Approximately 410pb-1 of pp̄ collisions at s=1.96TeV collected with the D0 detector during Run II of the Fermilab Tevatron collider are analyzed in search of such "stopped gluinos" decaying into a gluon and a neutralino (χ 10). Limits are placed on the (gluino cross section)×(probability to stop)×[BR(g →gχ 10)] as a function of the gluino and χ 10 masses, for gluino lifetimes from 30μs-100h. © 2007 The American Physical Society.Combined D0 measurements constraining the CP-violating phase and width difference in the Bs0 system
Physical Review D - Particles, Fields, Gravitation and Cosmology 76:5 (2007)
Abstract:
We combine the D0 measurement of the width difference between the light and heavy Bs0 mass eigenstates and of the CP-violating mixing phase determined from the time-dependent angular distributions in the Bs0→J/ψ decays along with the charge asymmetry in semileptonic decays also measured with the D0 detector. With the additional constraint from the world average of the flavor-specific Bs0 lifetime, we obtain ΔΓs≡(ΓL- ΓH)=0.13±0.09ps-1 and | s|=0.70-0.47+0.39 or ΔΓs=-0. 13±0.09ps-1 and | s|=2.44-0.39+0.47. The data sample corresponds to an integrated luminosity of 1.1fb-1 accumulated with the D0 detector at the Fermilab Tevatron Collider. © 2007 The American Physical Society.Search for third-generation scalar leptoquarks in pp at square root s=1.96 TeV.
Phys Rev Lett 99:6 (2007) 061801
Abstract:
We report on a search for charge-1/3 third-generation leptoquarks (LQ) produced in pp collisions at square root s =1.96 TeV using the D0 detector at Fermilab. Third-generation leptoquarks are assumed to be produced in pairs and to decay to a tau neutrino and a b quark with branching fraction B. We place upper limits on sigma(pp --> LQLQ)B2 as a function of the leptoquark mass M(LQ). Assuming B=1, we exclude at the 95% confidence level third-generation scalar leptoquarks with M(LQ)<229 GeV.Search for third-generation scalar leptoquarks in pp̄ collisions at s=1.96TeV
Physical Review Letters 99:6 (2007)