Accelerator Neutrinos

Abstract:

This study reports the first measurement of the azimuthal decorrelation between jets with pseudorapidity separation up to five units. The data were accumulated using the D0 detector during the 1992–1993 collider run of the Fermilab Tevatron at √s=1.8 TeV. These results are compared to next-to-leading order (NLO) QCD predictions and to two leading-log approximations (LLA) where the leading-log terms are resummed to all orders in αS. The final state jets as predicted by NLO QCD show less azimuthal decorrelation than the data. The parton showering LLA Monte Carlo HERWIG describes the data well; an analytical LLA prediction based on Balitsky-Fadin-Kuraev-Lipatov resummation shows more decorrelation than the data. © 1996 The American Physical Society.

Abstract:

We present a measurement of the forward-backward charge asymmetry of the process pp¯ → Z0/γ + X, Z0/γ → e+e− at Mee > MZ using 110 pb−1 of data at √ s = 1.8 TeV collected at the Collider Detector at Fermilab. The measured charge asymmetries are 0.43 ± 0.10 in the invariant mass region Mee > 105 GeV/c2, and 0.070 ± 0.016 in the region 75 < Mee < 105 GeV/c2. These results are consistent with the standard model values of 0.528 ± 0.009 and 0.052 ± 0.002, respectively. © 1996 The American Physical Society.

Abstract:

The properties of high-mass multijet events produced at the Fermilab proton-antiproton collider are compared with leading order QCD matrix element predictions, QCD parton shower Monte Carlo predictions, and the predictions from a model in which events are distributed uniformly over the available multibody phase space. Multijet distributions corresponding to ([Formula presented]) variables that span the [Formula presented]-body parameter space are found to be well described by the QCD calculations for inclusive three-jet, four-jet, and five-jet events. The agreement between data, QCD matrix element calculations, and QCD parton shower Monte Carlo predictions suggests that 2→2 scattering plus gluon radiation provides a good first approximation to the full LO QCD matrix element for events with three, four, or even five jets in the final state. © 1996 The American Physical Society.

Abstract:

A study of the particle multiplicity between jets with large rapidity separation has been performed using the D0 detector at the Fermilab Tevatron pp^¯ Collider operating at √s = 1.8 TeV. A significant excess of low-multiplicity events is observed above the expectation for color-exchange processes. The measured fractional excess is 1.07±0.10(stat)^+0.25−0.13(syst)%, which is consistent with a strongly interacting color-singlet (colorless) exchange process and cannot be explained by electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on the fraction of dijet events with color-singlet exchange, independent of the rapidity gap survival probability. © 1996 The American Physical Society.

Abstract:

The lifetimes of the B- and B−0 mesons are measured using the partially reconstructed semileptonic decays B−→D1-v−X, where D is either a D0 or D*+ meson. The data were collected by the CDF detector at the Fermilab Tevatron collider during 1992-1993 and correspond to 19.3 pb−1 of p−p collisions at s = 1.8 TeV. We measure the decay length distributions and find the lifetimes to be τ(B−) = 1.56±0.13±0.06 ps and τ(B−0) = 1.54±0.08±0.06 ps, and the ratio of lifetimes to be τ(B−)/τ(B−0) = 1.01±0.11±0.02, where the first uncertainties are statistical and the second are systematic. © 1996 The American Physical Society.