735 research outputs found
Measurement of the B0_s semileptonic branching ratio to an orbitally excited D_s** state, Br(B0_s -> Ds1(2536) mu nu)
In a data sample of approximately 1.3 fb-1 collected with the D0 detector
between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been
observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via
the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the
branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D*
K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely
from B0_s, an extraction of the semileptonic branching ratio Br(B0_s ->
D_s1(2536) mu nu X) is made.Comment: 7 pages, 2 figures, LaTeX, version with minor changes as accepted by
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 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
Search for right-handed W bosons in top quark decay
We present a measurement of the fraction f+ of right-handed W bosons produced
in top quark decays, based on a candidate sample of events in the
lepton+jets decay mode. These data correspond to an integrated luminosity of
230pb^-1, collected by the DO detector at the Fermilab Tevatron
Collider at sqrt(s)=1.96 TeV. We use a constrained fit to reconstruct the
kinematics of the and decay products, which allows for the
measurement of the leptonic decay angle for each event. By comparing
the 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+=3.6x10^-4.Comment: Submitted to Physical Review D Rapid Communications 7 pages, 3
figure
Measurement of the Lifetime Difference in the B_s^0 System
We present a study of the decay B_s^0 -> J/psi phi We obtain the CP-odd
fraction in the final state at time zero, R_perp = 0.16 +/- 0.10 (stat) +/-
0.02 (syst), the average lifetime of the (B_s, B_sbar) system, tau (B_s^0)
=1.39^{+0.13}_{-0.16} (stat) ^{+0.01}_{-0.02} (syst) ps, and the relative width
difference between the heavy and light mass eigenstates, Delta Gamma/Gamma =
(Gamma_L - Gamma_H)/Gamma =0.24^{+0.28}_{-0.38} (stat) ^{+0.03}_{-0.04} (syst).
With the additional constraint from the world average of the B_s^0$lifetime
measurements using semileptonic decays, we find tau (B_s^0)= 1.39 +/- 0.06 ~ps
and Delta Gamma/\Gamma = 0.25^{+0.14}_{-0.15}. For the ratio of the B_s^0 and
B^0 lifetimes we obtain tau(B_s^0)/tau(B^0)} = 0.91 +/- 0.09 (stat) +/- 0.003
(syst).Comment: submitted to Phys. Rev. Lett. FERMILAB-PUB-05-324-
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 of the B_c meson in the semileptonic decay channel
Using approximately 1.3 fb-1 of data collected by the D0 detector between
2002 and 2006, we measure the lifetime of the B_c meson in the B_c -> J/psi mu
nu X final state. A simultaneous unbinned likelihood fit to the J/\psi+mu
invariant mass and lifetime distributions yields a signal of 881 +/- 80 (stat)
candidates and a lifetime measurement of \tau(B_c) = 0.448 +0.038 -0.036 (stat)
+/- 0.032 (syst) ps.Comment: 7 pages, 2 figures, submitted to Phys. Rev. Let
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
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
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