Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in pp-bar collisions at a center-of-mass energy sqrt(s)=1.96 TeV. The ...analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb-1. Azimuthal correlations are stronger at larger transverse momenta. These are well-described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where soft effects are significant.
Using the exclusive decay B^0_s -> J/psi (mu+mu-) phi(K+K-), we report the most precise single measurement of the B^0_s lifetime. The data sample corresponds to an integrated luminosity of ...approximately 220 pb-1 collected with the DO detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B^0_s lifetime, \tau(B^0_s) = 1.444 +0.098/-0.090 stat +/- 0.020 sys ps. We also report a measurement for the lifetime of the B^0 meson using the exclusive decay B^0 -> J/psi (mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining \tau(B^0) = 1.473 +0.052/-0.050 stat +/- 0.023 sys ps, and the ratio of lifetimes, \tau(B^0_s)/\tau(B^0) = 0.980 +0.075/-0.070 stat +/- 0.003 sys.
We examine properties of $t\overline{t}$ candidate events in lepton + jets final states to establish the helicities of W bosons in $t\rightarrow$W+b$ decays. Our analysis is based on a direct ...calculation of a probability density for each event to correspond to a $t\overline{t}$ final state, as a function of the helicity of the $W$ boson. Using the 125 events/pb of data collected by the D0 experiment at the Fermilab Tevatron $p\overline{p}$ Collider at $\sqrt{s}$=1.8 TeV, we obtain a longitudinal helicity fraction $F_0$=0.56$\pm$0.31, consistent with the prediction of $F_0$=0.70 from the standard model.
A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of ...(s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.
A search for pair production of doubly-charged Higgs bosons in the process p pbar to H++H-- to mu+mu+mu-mu- is performed with the D0 Run II detector at the Fermilab Tevatron. The analysis is based on ...a sample of inclusive di-muon data collected at an energy of sqrt{s}=1.96 TeV, corresponding to an integrated luminosity of 113 pb-1. In the absence of a signal, 95 % confidence level mass limits of M(H++L)>118.4 GeV/c2 and M(H++R)>98.2 GeV/c2 are set for left-handed and right-handed doubly-charged Higgs bosons, respectively, assuming 100% branching into muon pair
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