121 research outputs found
Heavy quark polarizations of in the general two Higgs doublet model
The polarizations of the heavy quark ( or ) in the process have been calculated in the general two Higgs doublet model.
The CP violating normal polarization of the top quark can reach 8%, and for the bottom quark, while it is zero in the standard model. The
longitudinal and transverse polarizations of the bottom quark can be
significantly different from those in SM and consequently could aslo be used as
the probe of the new physics.Comment: 12 pages, discussion on statistic significance added, version to
appear in PR
T-violation in decay in a general two-Higgs doublet model
We calculate the transverse muon polarization in the process
arising from the Yukawa couplings of charged Higgs boson in a general two-Higgs
doublet model where spontaneous violation of CP is presentComment: 6 pages, latex, accepted for publication in Phys. Rev.
Light Charged Higgs Boson and Supersymmetry
A possible discovery of a relatively light charged Higgs boson H^+ in near
future experiments, with a mass M_{H+} ~< 110 GeV, together with the present
LEP2 direct limits on the chargino and neutral Higgs sectors, would disfavour
the minimal supersymmetric standard model as well as its frequently discussed
next-to-minimal supersymmetric extension. We show that a supersymmetric origin
can naturally be ascribed to the existence of such a light charged Higgs scalar
within the context of the recently introduced minimal nonminimal supersymmetric
standard model.Comment: 12 pages, LaTeX file, one reference adde
Transverse Tau Polarization in Decays of the Top and Bottom Quarks in the Weinberg Model of CP Non-conservation
We show that the transverse polarization asymmetry of the -lepton in
the decay is extremely sensitive to CP violating
phases arising from the charged Higgs exchange in the Weinberg model of CP
non-conservation. Qualitatively, the polarization asymmetries are enhanced over
rate or energy asymmetries by a factor of . Thus for optimal values of the parameters the method requires top pairs to be observable rather than needed for rate or energy
asymmetries. We also examine polarization in b decays via and find that it can also be very effective in constraining the CP
violation parameters of the extended Higgs sector.Comment: 11,1 figure, SLAC-PUB-608
Tests of the Standard Model Using Muon Polarization Asymmetries in Kaon Decays
We have examined the physics and the experimental feasibility of studying
various kaon decay processes in which the polarization of a muon in the final
state is measured. Valuable information on CP violation, the quark mixing (CKM)
matrix, and new physics can be obtained from such measurements. We have
considered muon polarization in K_L to mu+ mu- and K to pi mu+ mu- decays.
Although the effects are small, or difficult to measure because of the small
branching ratios involved, these studies could provide clean measurements of
the CKM parameters. The experimental difficulty appears comparable to the
observation of K to pi nu barnu. New sources of physics, involving non-standard
CP violation, could produce effects observable in these measurements. Limits
from new results on the neutron and electron electric dipole moment, and
epsilon-prime over epsilon in neutral kaon decays, do not eliminate certain
models that could contribute to the signal. A detailed examination of muon
polarization out of the decay plane in KMU3 and radiative KMU2 decays also
appears to be of interest. With current kaon beams and detector techniques, it
is possible to measure the T-violating polarization for KMU3 with uncertainties
approaching 0.0001. This level of sensitivity would provide an interesting
probe of new physics.Comment: 24 pages, 3 figures, To be published in the International Journal of
Modern Physics
Penguins leaving the pole: bound-state effects in B decaying to K* + photon
Applying perturbative QCD methods recently seen to give a good description of
the two body hadronic decays of the B meson, we address the question of
bound-state effects on the decay B into K* + gamma. Consistent with most
analyses, we demonstrate that gluonic penguins, with photonic bremsstrahlung
off a quark, change the decay rate by only a few percent. However, explicit
off-shell b-quark effects normally discarded are found to be large in
amplitude, although in the standard model accidents of phase minimize the
effect on the rate. Using an asymptotic distribution amplitude for the K* and
just the standard model, we can obtain a branching ratio of a few times
10^{-5}, consistent with the observed rate.Comment: 12 pages. U. of MD PP \#94-129; DOE/ER/40762-033; WM-94-104. LaTeX,
One figure, available by fax or pos
The transition in softly broken supersymmetry
We study the effect of supersymmetric contributions to the effective quark
transition , including leading order QCD effects. We apply
the discussion to the decay . Even though one-particle
irreducible contributions could play a role, numerical cancelations make the
amplitude for the two-photon emission strongly correlated to the
amplitude which is sharply constrained by experiment. A quite general statement
follows: as long as non-standard physics effects appear only in the matching of
the Wilson coefficients of the standard effective operator basis, the
deviations from the standard model expectations of the decay rates induced by
are bound to follow closely the corresponding deviations
on . Effects of new physics are therefore bound to be small.Comment: Latex2e, RevTex, 22 pages, 8 eps figures, comments and references
adde
Analysis of Neutral Higgs-Boson Contributions to the Decays B_s -> l^+l^- and B -> K l^+l^-
We report on a calculation of Higgs-boson contributions to the decays B_s ->
l^+l^- and B -> K l^+l^- (l=e, mu) which are governed by the effective
Hamiltonian describing b -> s l^+ l^-. Compact formulae for the Wilson
coefficients are provided in the context of the type-II two-Higgs-doublet model
(2HDM) and supersymmetry (SUSY) with minimal flavour violation, focusing on the
case of large tan(beta). We derive, in a model-independent way, constraints on
Higgs-boson-mediated interactions, using present experimental results on rare B
decays including b -> s gamma, B_s -> mu^+ mu^-, and B -> K^(*) mu^+ mu^-. In
particular, we assess the impact of possible scalar and pseudoscalar
interactions transcending the standard model (SM) on the branching ratio of B_s
-> mu^+ mu^- and the forward-backward (FB) asymmetry of mu^- in B -> K mu^+
mu^- decay. We find that the average FB asymmetry, which is unobservably small
within the SM, and therefore a potentially valuable tool to search for new
physics, is predicted to be no greater than 4% for a nominal branching ratio of
about 6x10^{-7}. Moreover, striking effects on the decay spectrum of B -> K
mu^+ mu^- are already ruled out by experimental data on the B_s -> mu^+ mu^-
branching fraction. In addition, we study the constraints on the parameter
space of the 2HDM and SUSY with minimal flavour violation. While the type-II
2HDM does not give any sizable contributions to the above decay modes, we find
that SUSY contributions obeying the constraint on b -> s gamma can affect
significantly the branching ratio of B_s -> mu^+ mu^-. We also comment on
previous calculations contained in the literature.Comment: 29 pages, REVTeX, 8 figures. Minor corrections in Eqs. (5.4), (5.11)
and (6.3) of the published versio
A Resolution to the Supersymmetric CP Problem with Large Soft Phases via D-branes
We examine the soft supersymmetry breaking parameters that result from
various ways of embedding the Standard Model (SM) on D-branes within the Type I
string picture, allowing the gaugino masses and to have large CP-
violating phases. One embedding naturally provides the relations among soft
parameters to satisfy the electron and neutron electric dipole moment
constraints even with large phases, while with other embeddings large phases
are not allowed. The string models provide some motivation for large phases in
the soft breaking parameters. The results generally suggest how low energy data
might teach us about Planck scale physics.Comment: 11 pages, 2 eps figures; revised references and updated tex
New two-loop contribution to electric dipole moment in supersymmetric theories
We calculate a new type of two-loop contributions to the electric dipole
moments of the electron and neutron in supersymmetric theories. The new
contributions are originated from the potential CP violation in the trilinear
couplings of the Higgs bosons to the scalar-top or the scalar-bottom quarks.
These couplings were previously very weakly constrained. The electric dipole
moments are induced through a mechanism analogous to that due to Barr and Zee.
We find observable effects for a sizeable portion of the parameter space
related to the third generation scalar-quarks in the minimal supersymmetric
standard model which cannot be excluded by earlier considerations.Comment: Erratum appended in the paper: EDM predictions are by a factor 2
larger than those given in the published versio
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