42 research outputs found
Search for charged Higgs bosons decaying to top and bottom quarks in ppbar collisions
We describe a search for production of a charged Higgs boson, q \bar{q'} ->
H^+, reconstructed in the t\bar{b} final state in the mass range 180 <= M_{H^+}
<= 300 GeV. The search was undertaken at the Fermilab Tevatron collider with a
center-of-mass energy sqrt{s} = 1.96 TeV and uses 0.9 fb^{-1} of data collected
with the D0 detector. We find no evidence for charged Higgs boson production
and set upper limits on the production cross section in the Types I, II and III
two-Higgs-doublet models (2HDMs). An excluded region in the (M_{H^+},tan\beta)
plane for Type I 2HDM is presented.Comment: Submitted to Phys. Rev. Letter
Measurement of Semileptonic Branching Fractions of B Mesons to Narrow D** States
Using the data accumulated in 2002-2004 with the DO detector in
proton-antiproton collisions at the Fermilab Tevatron collider with
centre-of-mass energy 1.96 TeV, the branching fractions of the decays B ->
\bar{D}_1^0(2420) \mu^+ \nu_\mu X and B -> \bar{D}_2^{*0}(2460) \mu^+ \nu_\mu X
and their ratio have been measured: BR(\bar{b}->B) \cdot BR(B-> \bar{D}_1^0
\mu^+ \nu_\mu X) \cdot BR(\bar{D}_1^0 -> D*- pi+) =
(0.087+-0.007(stat)+-0.014(syst))%; BR(\bar{b}->B)\cdot BR(B->D_2^{*0} \mu^+
\nu_\mu X) \cdot BR(\bar{D}_2^{*0} -> D*- \pi^+) =
(0.035+-0.007(stat)+-0.008(syst))%; and (BR(B -> \bar{D}_2^{*0} \mu^+ \nu_\mu
X)BR(D2*0->D*- pi+)) / (BR(B -> \bar{D}_1^{0} \mu^+ \nu_\mu X)\cdot
BR(\bar{D}_1^{0}->D*- \pi^+)) = 0.39+-0.09(stat)+-0.12(syst), where the charge
conjugated states are always implied.Comment: submitted to Phys. Rev. Let
Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top quark pair production cross section with the D0 detector at sqrt(s)=1.96 TeV
We present the first simultaneous measurement of the ratio of branching
fractions, R=B(t->Wb)/B(t->Wq), with q being a d, s, or b quark, and the top
quark pair production cross section sigma_ttbar in the lepton plus jets channel
using 0.9 fb-1 of ppbar collision data at sqrt(s)=1.96 TeV collected with the
D0 detector. We extract R and sigma_ttbar by analyzing samples of events with
0, 1 and >= 2 identified b jets. We measure R = 0.97 +0.09-0.08 (stat+syst) and
sigma_ttbar = 8.18 +0.90-0.84 (stat+syst)} +/-0.50 (lumi) pb, in agreement with
the standard model prediction.Comment: submitted to Phys.Rev.Letter
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 collisions at 1.96 TeV in events
containing a pair of energetic muons. The data correspond to 246 \ipb 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 TeV and 1.27 TeV within several
formalisms. These are the most stringent limits achieved in the dimuon channel
to date.Comment: 8 pages, 3 figures, 1 table. Published in Phys. Rev. Lett. Minor
changes in v2 to match the published versio
Measurement of the forward-backward charge asymmetry and extraction of sin^2Theta^{eff}_W in ppbar -> Z/\gamma^{*}+X -> e+e+X events produced at \sqrt{s}=1.96 TeV
We present a measurement of the forward-backward charge asymmetry ()
in events at a center-of-mass energy
of 1.96 TeV using 1.1 fb of data collected with the D0 detector at the
Fermilab Tevatron collider. is measured as a function of the invariant
mass of the electron-positron pair, and found to be consistent with the
standard model prediction. We use the measurement to extract the
effective weak mixing angle .Comment: 7 Pages, 1 Figure, 3 Tables, Accepted by Phys. Rev. Let
Measurement of the Lifetime Using Semileptonic Decays
We report a measurement of the lifetime in the semileptonic decay
channel (and its charge conjugate), using
approximately 0.4 fb of data collected with the D0 detector during 2002
-- 2004. We have reconstructed 5176 signal events, where the
is identified via the decay , followed by . Using these events, we have measured the lifetime to be
. This is the most precise measurement of the lifetime to date.Comment: To appear in Phys. Rev. Lett., 7 pages, 2 figure
Search for the Rare Decay B0_s -> phi mu^+ mu- with the D0 Detector
We present a search for the flavor-changing neutral current decay B0_s -> phi
mu+ mu- using about 0.45 fb^-1 of data collected in p \bar p collisions at
sqrt{s} =1.96 TeV with the D{\O}detector at the Fermilab Tevatron Collider. We
find an upper limit on the branching ratio of this decay normalized to B0_s ->
J/psi phi of B(B0_s -> phi mu+ mu-)/B(B0_s -> J/psi phi) < 4.4\times 10^{-3} at
the 95% C.L. Using the central value of the world average branching fraction of
B0_s -> J/psi phi, the limit corresponds to B(B0_s -> phi mu+ mu-) < 4.1 \times
10^{-6} at the 95% C.L., the most stringent upper bound to date.Comment: 7 pages, 2 figures, LaTeX, to be submitted to Physical Review Letter
Multivariate searches for single top quark production with the D0 detector
We present a search for electroweak production of single top quarks in the
s-channel (p-pbar -> t bbar + X) and t-channel (p-pbar -> tq bbar + X) modes.
We have analyzed 230 pb^(-1) of data collected with the D0 detector at the
Fermilab Tevatron collider at a center-of-mass energy of sqrt(s) = 1.96 TeV.
Two separate analysis methods are used: neural networks and a cut-based
analysis. No evidence for a single top quark signal is found. We set 95%
confidence level upper limits on the production cross sections using Bayesian
statistics, based on event counts and binned likelihoods formed from the neural
network output. The limits from the neural network (cut-based) analysis are 6.4
pb (10.6 pb) in the s-channel and 5.0 pb (11.3 pb) in the t-channel.Comment: submitted to Phys. Rev. D, Fermilab preprint Fermilab-Pub-06/069-
Search for a heavy resonance decaying into a Z+jet final state in p-pbar collisions at sqrt(s) = 1.96 TeV using the D0 detector
We have searched for a heavy resonance decaying into a Z+jet final state in
p-pbar collisions at a center of mass energy of 1.96 TeV at the Fermilab
Tevatron collider using the D0 detector. No indication for such a resonance was
found in a data sample corresponding to an integrated luminosity of 370/pb. We
set upper limits on the cross section times branching fraction for heavy
resonance production at the 95% C.L. as a function of the resonance mass and
width. The limits are interpreted within the framework of a specific model of
excited quark production.Comment: 8 pages, 5 figures, submitted to Physical Review
Search for sneutrino particles in e + mu final states in ppbar collisions at sqrt{s} =1.96 TeV
We report a search for R-parity violating production and decay of sneutrino
particles in the e+mu final state with 1.04+-0.06 fb-1 of data collected with
the D0 detector at the Fermilab Tevatron Collider in 2002--2006. Good agreement
between the data and the standard model prediction is observed. With no
evidence for new physics, we set limits on the R-parity violating couplings
and as a function of sneutrino mass.Comment: 6 pages, 3 figures, published in Phys. Rev. Let