945 research outputs found
Search for right-handed W bosons in top quark decay
This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.72.011104.We present a measurement of the fraction f(+) of right-handed W bosons produced in top quark decays, based on a candidate sample of tt-bar events in the lepton+jets decay mode. These data correspond to an integrated luminosity of 230 pb(−1), collected by the D0 detector at the Fermilab Tevatron pp-bar Collider at s√=1.96 TeV. We use a constrained fit to reconstruct the kinematics of the tt-bar and decay products, which allows for the measurement of the leptonic decay angle θ∗ for each event. By comparing the cosθ∗ distribution from the data with those for the expected background and signal for various values of f(+), we find f(+(=0.00±0.13(stat)±0.07(syst). This measurement is consistent with the standard model prediction of f(+)=3.6×10(−4)
The Layer 0 Inner Silicon Detector of the D0 Experiment
This paper describes the design, fabrication, installation and performance of
the new inner layer called Layer 0 (L0) that was inserted in the existing Run
IIa Silicon Micro-Strip Tracker (SMT) of the D0 experiment at the Fermilab
Tevatron collider. L0 provides tracking information from two layers of sensors,
which are mounted with center lines at a radial distance of 16.1 mm and 17.6 mm
respectively from the beam axis. The sensors and readout electronics are
mounted on a specially designed and fabricated carbon fiber structure that
includes cooling for sensor and readout electronics. The structure has a thin
polyimide circuit bonded to it so that the circuit couples electrically to the
carbon fiber allowing the support structure to be used both for detector
grounding and a low impedance connection between the remotely mounted hybrids
and the sensors.Comment: 28 pages, 9 figure
Direct limits on the B-s(0) oscillation frequency
We report results of a study of the B-s(0) oscillation frequency using a large sample of B-s(0) semileptonic decays corresponding to approximately 1 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2006. The amplitude method gives a lower limit on the B-s(0) oscillation frequency at 14.8 ps(-1) at the 95% C.L. At Delta m(s)=19 ps(-1), the amplitude deviates from the hypothesis A=0 (1) by 2.5 (1.6) standard deviations, corresponding to a two-sided C.L. of 1% (10%). A likelihood scan over the oscillation frequency, Delta m(s), gives a most probable value of 19 ps(-1) and a range of 17 <Delta m(s)< 21 ps(-1) at the 90% C.L., assuming Gaussian uncertainties. This is the first direct two-sided bound measured by a single experiment. If Delta m(s) lies above 22 ps(-1), then the probability that it would produce a likelihood minimum similar to the one observed in the interval 16-22 ps(-1) is (5.0 +/- 0.3)%
Search for supersymmetry via associated production of charginos and neutralinos in final states with three leptons
A search for associated production of charginos and neutralinos is performed using data recorded with the D0 detector at a p (p) over bar center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. This analysis considers final states with missing transverse energy and three charged leptons, of which at least two are electrons or muons. No evidence for supersymmetry is found in a data set corresponding to an integrated luminosity of 320 pb(-1). Limits on the product of the production cross section and leptonic branching fraction are set. For the minimal supergravity model, a chargino lower mass limit of 117 GeV at the 95% C.L. is derived in regions of parameter space with enhanced leptonic branching fractions
Search for randall-sundrum gravitons in dilepton and diphoton final states
We report the first direct search for the Kaluza-Klein (KK) modes of Randall-Sundrum gravitons using dielectron, dimuon, and diphoton events observed with the D0 detector operating at the Fermilab Tevatron p (p) over bar Collider at root s = 1: 96 TeV. No evidence for resonant production of gravitons has been found in the data corresponding to an integrated luminosity of approximate to 260 pb(-1). Lower limits on the mass of the first KK mode at the 95% C. L. have been set between 250 and 785 GeV, depending on its coupling to standard model particles
Search for large extra spatial dimensions in dimuon production with the D0 detector
We present the results of a search for the effects of large extra spatial dimensions in p (p) over bar collisions at root s = 1: 96 TeV in events containing a pair of energetic muons. The data correspond to 246 pb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. Good agreement with the expected background was found, yielding no evidence for large extra dimensions. We set 95% C. L. lower limits on the fundamental Planck scale between 0.85 and 1.27 TeV within several formalisms. These are the most stringent limits achieved in the dimuon channel to date
Search for resonant second generation slepton production at the Fermilab Tevatron
We present a search for supersymmetry in the R-parity violating resonant production and decay of smuons and muon sneutrinos in the channels mu ->chi(0)(1)mu, mu ->chi(0)(2,3,4)mu, and nu(mu)->chi(+/-)(1,2)mu. We analyzed 0.38 fb(-1) of integrated luminosity collected between April 2002 and August 2004 with the D0 detector at the Fermilab Tevatron Collider. The observed number of events is in agreement with the standard model expectation, and we calculate 95% C.L. limits on the slepton production cross section times branching fraction to gaugino plus muon, as a function of slepton and gaugino masses. In the framework of minimal supergravity, we set limits on the coupling parameter lambda(')(211), extending significantly previous results obtained in Run I of the Tevatron and at the CERN LEP collider
Measurement of semileptonic branching fractions of B mesons to narrow D-** states
Using the data accumulated in 2002-2004 with the D0 detector in proton-antiproton collisions at the Fermilab Tevatron collider with a center-of-mass energy of 1.96 TeV, the branching fractions of the decays B ->(D) over bar (0)(1)(2420)mu(+)nu(mu)X and B ->(D) over bar (*0)(2)(2460)mu(+)nu(mu)X and their ratio have been measured: B (b) over bar -> B)xB(B -> (D) over bar (0)(1)mu(+)nu(mu)X)xB((D) over bar (0)(1)-> D(*-)pi(+))=[0.087 +/- 0.007(stat)+/- 0.014(syst)]%; B((b) over bar -> B)xB(B ->(D) over bar (*0)(2)mu(+)nu(mu)X)xB((D) over bar (*0)(2)-> D(*-)pi(+))=[0.035 +/- 0.007(stat)+/- 0.008(syst)]% and [B(B ->(D) over bar (*0)(2)mu(+)nu(mu)X)xB((D) over bar (*0)(2)-> D(*-)pi(+))]/[B(B ->(D) over bar (0)(1)mu(+)nu(mu)X)xB((D) over bar (0)(1)-> D(*-)pi(+))]=0.39 +/- 0.09(stat)+/- 0.12(syst), where the charge conjugated states are always implied
Measurement of Dijet Angular Distributions at CDF
We have used 106 pb^-1 of data collected in proton-antiproton collisions at
sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular
distributions in events with two jets in the final state. The angular
distributions agree with next to leading order (NLO) predictions of Quantum
Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at
95% confidence level (CL) a model of quark substructure in which only up and
down quarks are composite and the contact interaction scale is Lambda_ud(+) <
1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are
composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6
TeV.Comment: 16 pages, 2 figures, 2 tables, LaTex, using epsf.sty. Submitted to
Physical Review Letters on September 17, 1996. Postscript file of full paper
available at http://www-cdf.fnal.gov/physics/pub96/cdf3773_dijet_angle_prl.p
Search for charged Higgs decays of the top quark using hadronic tau decays
We present the result of a search for charged Higgs decays of the top quark,
produced in collisions at 1.8 TeV. When the charged
Higgs is heavy and decays to a tau lepton, which subsequently decays
hadronically, the resulting events have a unique signature: large missing
transverse energy and the low-charged-multiplicity tau. Data collected in the
period 1992-1993 at the Collider Detector at Fermilab, corresponding to
18.70.7~pb, exclude new regions of combined top quark and charged
Higgs mass, in extensions to the standard model with two Higgs doublets.Comment: uuencoded, gzipped tar file of LaTeX and 6 Postscript figures; 11 pp;
submitted to Phys. Rev.
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