191 research outputs found
Search for Rare and Forbidden Dilepton Decays of the D+, Ds, and D0 Charmed Mesons
We report the results of a search for flavor-changing neutral current,
lepton-flavor violating, and lepton-number violating decays of D+, Ds, and D0
mesons (and their antiparticles) into modes containing muons and electrons.
Using data from Fermilab charm hadroproduction experiment E791, we examine the
pi,l,l and K,l,l decay modes of D+ and Ds and the l+l- decay modes of D0. No
evidence for any of these decays is found. Therefore, we present
branching-fraction upper limits at 90% confidence level for the 24 decay modes
examined. Eight of these modes have no previously reported limits, and fourteen
are reported with significant improvements over previously published results.Comment: 12 pages, 3 figures, LaTeX, elsart.cls, epsf.sty, amsmath.sty
Submitted to Physics Letters
Measurement of the form-factor ratios for D+ --> K* l nu
The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in
the decay D+ --> K* l nu, K* -->K-pi+ have been measured using data from charm
hadroproduction experiment E791 at Fermilab. From 3034 (595) signal
(background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09,
r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33
+-0.29. The values of the form factor ratios rv and r2 measured for the muon
channel are combined with the values of rv and r2 that we have measured in the
electron channel. The combined E791 results for the muon and electron channels
are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.Comment: 9 pages + 3 figures ; submitted to PL
Differential cross sections, charge production asymmetry, and spin-density matrix elements for D*(2010) produced in 500 GeV/c pi^- nucleon interactions
We report differential cross sections for the production of D*(2010) produced
in 500 GeV/c pi^- nucleon interactions from experiment E791 at Fermilab, as
functions of Feynman-x (x_F) and transverse momentum squared (p_T^2). We also
report the D* +/- charge asymmetry and spin-density matrix elements as
functions of these variables. Investigation of the spin-density matrix elements
shows no evidence of polarization. The average values of the spin alignment are
\eta= 0.01 +- 0.02 and -0.01 +- 0.02 for leading and non-leading particles,
respectively.Comment: LaTeX2e (elsart.cls). 13 pages, 6 figures (eps files). Submitted to
Physics Letters
f(R) Quantum Cosmology
We have quantized a flat cosmological model in the context of the metric f(R)
models, using the causal Bohmian quantum theory. The equations are solved and
then we have obtained how the quantum corrections influence the classical
equations.Comment: 6 figures. to appear in General Relativity and Cosmology, 200
Search for W' bosons decaying to an electron and a neutrino with the D0 detector
This Letter describes the search for a new heavy charged gauge boson W'
decaying into an electron and a neutrino. The data were collected with the D0
detector at the Fermilab Tevatron proton-antiproton Collider at a
center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity
of about 1 inverse femtobarn. Lacking any significant excess in the data in
comparison with known processes, an upper limit is set on the production cross
section times branching fraction, and a W' boson with mass below 1.00 TeV can
be excluded at the 95% C.L., assuming standard-model-like couplings to
fermions. This result significantly improves upon previous limits, and is the
most stringent to date.Comment: submitted to Phys. Rev. Let
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
Measurement of three-jet differential cross sections d sigma-3jet / d M-3jet in p anti-p collisions at sqrt(s)=1.96 TeV
We present the first measurement of the inclusive three-jet differential
cross section as a function of the invariant mass of the three jets with the
largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96
TeV. The measurement is made in different rapidity regions and for different
jet transverse momentum requirements and is based on a data set corresponding
to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at
the Fermilab Tevatron Collider. The results are used to test the three-jet
matrix elements in perturbative QCD calculations at next-to-leading order in
the strong coupling constant. The data allow discrimination between
parametrizations of the parton distribution functions of the proton.Comment: 10 pages, 4 figures, 2 tables, submitted to Phys. Lett. B, corrected
chi2 values for NNPD
Search for pair production of the scalar top quark in muon+tau final states
We present a search for the pair production of scalar top quarks
(), the lightest supersymmetric partners of the top quarks, in
collisions at a center-of-mass energy of 1.96 TeV, using data
corresponding to an integrated luminosity of {7.3 } collected with the
\dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is
assumed to decay into a quark, a charged lepton, and a scalar neutrino
(). We investigate final states arising from and
. With no significant excess of events observed above the
background expected from the standard model, we set exclusion limits on this
production process in the (,) plane.Comment: Submitted to Phys. Lett.
Measurement of spin correlation in ttbar production using dilepton final states
We measure the correlation between the spin of the top quark and the spin of
the anti-top quark in (ttbar -> W+ W- b bbar -> l+ nu b l- nubar bbar) final
states produced in ppbar collisions at a center of mass energy sqrt(s)=1.96
TeV, where l is an electron or muon. The data correspond to an integrated
luminosity of 5.4 fb-1 and were collected with the D0 detector at the Fermilab
Tevatron collider. The correlation is extracted from the angles of the two
leptons in the t and tbar rest frames, yielding a correlation strength C=
0.10^{+0.45}_{-0.45}, in agreement with the NLO QCD prediction within two
standard deviations, but also in agreement with the no correlation hypothesis.Comment: 10 pages, 3 figures, submitted to PL
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