47,026 research outputs found
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 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 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
Relative rates of B meson decays into psi(2S) and J/psi mesons
We report on a study of the relative rates of B meson decays into psi(2S) and
J/psi mesons using 1.3 fb^-1 of pbar p collisions at sqrt(s) = 1.96 TeV
recorded by the D0 detector operating at the Fermilab Tevatron Collider. We
observe the channels B^0_s -> psi(2S)phi, B^0_s -> J/psi phi, B^+/- -> psi(2S)
K^+/-, and B^+/- -> J/psi K^+/- and we measure the relative branching fractions
for these channels to be B(B^0_s -> psi(2S)phi)/B(B^0_s -> J/psi phi) = 0.55
+/- 0.11 (stat) +/- 0.07 (syst) +/- 0.06 (B), B(B^+/- -> psi(2S) K^+/-)/B(B^+/-
-> J/psi K^+/-) = 0.65 +/- 0.04 (stat) +/- 0.03 (syst) +/- 0.07 (B) where the
final error corresponds to the uncertainty in the J/psi and psi(2S) branching
ratio into two muons.Comment: Published in Phys. Rev. D - Rapid Communicatio
Study of double parton interactions in diphoton + dijet events in collisions at TeV
We use a sample of diphoton + dijet events to measure the effective cross
section of double parton interactions, which is found to be mb. The sample was
collected by the D0 detector at the Fermilab Tevatron collider in
collisions at TeV and corresponds to an integrated luminosity
of 8.7 fb.Comment: 14 pages, submitted to Phys. Rev.
Precise measurement of the top quark mass from lepton+jets events at D0
We measure the mass of the top quark using top quark pair candidate events in
the lepton+jets channel from data corresponding to 1 fb-1 of integrated
luminosity collected by the D0 experiment at the Fermilab Tevatron collider. We
use a likelihood technique that reduces the jet energy scale uncertainty by
combining an in-situ jet energy calibration with the independent constraint on
the jet energy scale (JES) from the calibration derived using photon+jets and
dijet samples. We find the mass of the top quark to be
171.5+-1.8(stat.+JES)+-1.1(syst.) GeV.Comment: submitted to Phys. Rev. Letter
Measurement of the forward-backward asymmetry in the distribution of leptons in events in the lepton+jets channel
We present measurements of the forward-backward asymmetry in the angular
distribution of leptons from decays of top quarks and antiquarks produced in
proton-antiproton collisions. We consider the final state containing a lepton
and at least three jets. The entire sample of data collected by the D0
experiment during Run II of the Fermilab Tevatron Collider, corresponding to
9.7 inverse fb of integrated luminosity, is used. The asymmetry measured for
reconstructed leptons is %. When corrected for efficiency and resolution
effects within the lepton rapidity coverage of , the asymmetry is
found to be %.
Combination with the asymmetry measured in the dilepton final state yields
%. We examine the
dependence of on the transverse momentum and rapidity of the lepton.
The results are in agreement with predictions from the next-to-leading-order
QCD generator \mcatnlo, which predicts an asymmetry of % for
.Comment: submitted to Phys. Rev.
A Measurement of the K0 Charge Radius and a CP Violating Asymmetry Together with a Search for CP Violating E1 Direct Photon Emission in the Rare Decay KL->pi+pi-e+e-
Using the complete KTeV data set of 5241 candidate KL->pi+pi-e+e- decays
(including an estimated background of 204+-14 events), we have measured the
coupling gCR=0.163+- 0.014(stat)+-0.023(syst) of the CP conserving charge
radius process and from it determined a K0 charge radius of
(K0)=(-0.077+-0.007(stat)+-0.011(syst)) fm**2. We have also determined a
first experimental upper limit of 0.04 (90% CL) for the ratio |g_{E1}|/|g_{M1}|
of the coupling for the E1 direct photon emission process relative to the
coupling for M1 direct photon emission process. We also report the measurement
of its associated vector form factor |gM1`|(1+
(a_1/a_2)/(M(rho)**2-M(K)**2)+2M(K)E(gamma*)) where |gM1`|=(1.11+-
0.12(stat)+-0.08(syst) and a_1/a_2 = (-0.744+-0.027(stat)0.032(syst))
GeV**2/c**2. In addition, a measurement of the manifestly CP violating
asymmetry of magnitude (13.6+- 1.4+-(stat)+-1.5(syst))% in the CP and T odd
angle phi between the decay planes of the e+e- and pi+pi- pairs in the KL
center of mass system is reported
Measurement of the ppbar to ttbar production cross section at sqrt(s)=1.96 TeV in the fully hadronic decay channel
A measurement of the top quark pair production cross section in proton
anti-proton collisions at an interaction energy of sqrt(s)=1.96 TeV is
presented. This analysis uses 405 pb-1 of data collected with the D0 detector
at the Fermilab Tevatron Collider. Fully hadronic ttbar decays with final
states of six or more jets are separated from the multijet background using
secondary vertex tagging and a neural network. The ttbar cross section is
measured as sigma(ttbar)=4.5 -1.9 +2.0 (stat) -1.1 +1.4 (syst) +/- 0.3 (lumi)
pb for a top quark mass of m(t) = 175 GeV/c^2.Comment: 10 pages, 10 figures, submitted to Phys. Rev.
Direct Measurement of the Top Quark Mass at D0
We determine the top quark mass m_t using t-tbar pairs produced in the D0
detector by \sqrt{s} = 1.8 TeV p-pbar collisions in a 125 pb^-1 exposure at the
Fermilab Tevatron. We make a two constraint fit to m_t in t-tbar -> b W^+bbar
W^- final states with one W boson decaying to q-qbar and the other to e-nu or
mu-nu. Likelihood fits to the data yield m_t(l+jets) = 173.3 +- 5.6 (stat) +-
5.5 (syst) GeV/c^2. When this result is combined with an analysis of events in
which both W bosons decay into leptons, we obtain m_t = 172.1 +- 5.2 (stat) +-
4.9 (syst) GeV/c^2. An alternate analysis, using three constraint fits to fixed
top quark masses, gives m_t(l+jets) = 176.0 +- 7.9 (stat) +- 4.8 (syst)
GeV/C^2, consistent with the above result. Studies of kinematic distributions
of the top quark candidates are also presented.Comment: 43 pages, 53 figures, 33 tables. RevTeX. Submitted to Phys. Rev.
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