143 research outputs found
Supersymmetric effects in top quark decay into polarized W-boson
We investigate the one-loop supersymmetric QCD (SUSY-QCD) and electroweak
(SUSY-EW) corrections to the top quark decay into a b-quark and a longitudinal
or transverse W-boson. The corrections are presented in terms of the
longitudinal ratio \Gamma(t-->W_L b)/\Gamma(t--> W b) and the transverse ratio
\Gamma(t-->W_- b)/\Gamma(t--> W b). In most of the parameter space, both
SUSY-QCD and SUSY-EW corrections to these ratios are found to be less than 1%
in magnitude and they tend to have opposite signs. The corrections to the total
width \Gamma(t-->W b) are also presented for comparison with the existing
results in the literature. We find that our SUSY-EW corrections to the total
width differ significantly from previous studies: the previous studies give a
large correction of more than 10% in magnitude for a large part of the
parameter space while our results reach only few percent at most.Comment: Version in PRD (explanation and refs added
Supersymmetric Electroweak Corrections to Charged Higgs Boson Production in Association with a Top Quark at Hadron Colliders
We calculate the and supersymmetric electroweak corrections to the cross section
for the charged Higgs boson production in association with a top quark at the
Tevatron and the LHC. These corrections arise from the quantum effects which
are induced by potentially large Yukawa couplings from the Higgs sector and the
chargino-top(bottom)-sbottom(stop) couplings,
neutralino-top(bottom)-stop(sbottom) couplings and charged Higgs-stop-sbottom
couplings. They can decrease or increase the cross section depending on
but are not very sensitive to the mass of the charged Higgs boson
for high . At low the corrections decrease the total
cross sections significantly, which exceed -12% for below
at both the Tevatron and the LHC, but for the
corrections can become very small at the LHC. For high
these corrections can decrease or increase the total cross sections, and the
magnitude of the corrections are at most a few percent at both the Tevatron and
the LHC.Comment: 28 pages including 4 eps figure
Angular Distributions of Drell-Yan Lepton Pairs at the Tevatron: Order Corrections and Monte Carlo Studies
We investigate the angular distribution of the lepton pair in the process , where the
virtual photon is produced at high transverse momentum. The angular
distribution of the leptons is very sensitive to possible nonperturbative
effects, such as a nontrivial vacuum structure of QCD, and offers a good chance
to test such effects. We present complete calculations
of the decay lepton distributions in the lepton pair rest frame. An order
Monte Carlo study of the lepton angular distributions,
with acceptance cuts and energy resolution smearing applied to the leptons, is
also presented.Comment: 26 pages (Revtex) plus 9 (uuencoded) postscript figures available as
a compressed tar file at
ftp://phenom.physics.wisc.edu/pub/preprints/madph-94-857-figs.tar.
Higgs-boson production associated with a bottom quark at hadron colliders with SUSY-QCD corrections
The Higgs boson production p p (p\bar p) -> b h +X via b g -> b h at the LHC,
which may be an important channel for testing the bottom quark Yukawa coupling,
is subject to large supersymmetric quantum corrections. In this work the
one-loop SUSY-QCD corrections to this process are evaluated and are found to be
quite sizable in some parameter space. We also study the behavior of the
corrections in the limit of heavy SUSY masses and find the remnant effects of
SUSY-QCD. These remnant effects, which are left over in the Higgs sector by the
heavy sparticles, are found to be so sizable (for a light CP-odd Higgs and
large \tan\beta) that they might be observable in the future LHC experiment.
The exploration of such remnant effects is important for probing SUSY,
especially in case that the sparticles are too heavy (above TeV) to be directly
discovered at the LHC.Comment: Results for the Tevatron adde
Probing Topcolor-Assisted Technicolor from Top-Charm Associated Production at LHC
We propose to probe the topcolor-assisted technicolor (TC2) model from the
top-charm associated productions at the LHC, which are highly suppressed in the
Standard Model. Due to the flavor-changing couplings of the top quark with the
scalars (top-pions and top-Higgs) in TC2 model, the top-charm associated
productions can occur via both the s-channel and t-channel parton processes by
exchanging a scalar field at the LHC. We examined these processes through Monte
Carlo simulation and found that they can reach the observable level at the LHC
in quite a large part of the parameter space of the TC2 model.Comment: Version to appear in PRD (Rapid Communication
The fully differential single-top-quark cross section in next-to-leading order QCD
We present a new next-to-leading order calculation for fully differential
single-top-quark final states. The calculation is performed using phase space
slicing and dipole subtraction methods. The results of the methods are found to
be in agreement. The dipole subtraction method calculation retains the full
spin dependence of the final state particles. We show a few numerical results
to illustrate the utility and consistency of the resulting computer
implementations.Comment: 37 pages, latex, 2 ps figure
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
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