129 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
CP violating polarizations in semileptonic heavy meson decays
We study the -violating lepton transverse polarization () in
three body semileptonic heavy meson decays to pseudoscalar mesons and to vector
mesons. We calculate these polarizations in the heavy quark effective limit,
which simplifies the expressions considerably. After examining constraints from
conserving (including ) and violating
processes, we find that in decays, of the muon in multi-Higgs
doublet models can be of order , while of the can even
approach unity. In contrast, in decays is at most 1.5\%. We
discuss possibilities for detection of at current and future
factories. We also show that in decays to vector mesons, unlike in
decays to pseudoscalars, can get contributions from left-right models.
Unfortunately, in that case is proportional to - mixing,
and is thus small.Comment: 32pp plain LATEX, 3 figs (by EMAIL request), TRI-PP-94-1
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
CP Violation In Single Top Production And Decay Via p p-bar -> t b-bar +X -> W^+ b b-bar +X Within The MSSM: A Possible Application For Measuring \arg(A_t) At Hadron Colliders
CP-nonconserving effects in the reaction p p-bar -> t b-bar +X -> W^+ b b-bar
+X, driven by the supersymmetric CP-odd phase of the stop trilinear soft
breaking term, \arg(A_t), are studied. We discuss the CP-nonconserving effects
in both production and the associated decay amplitudes of the top. We find
that, within a plausible low energy scenario of the MSSM and keeping the
neutron electric dipole moment below its current limit, a CP-violating
cross-section asymmetry as large as 2-3% can arise if some of the parameters
lie in a favorable range. A partial rate asymmetry originating only in the top
decay t -> W^+ b is found to be, in general, below the 0.1% level which is
somewhat smaller than previous claims. For a low \tan\beta of order one the
decay asymmetry can reach at the most ~0.3%. This (few) percent level overall
CP-violating signal in p p-bar -> t b-bar +X -> W^+ b b-bar +X might be within
the reach of the future 2(4) TeV pp-bar Tevatron collider that may be able to
produce ~10000(~30000) such tb-bar events with an integrated luminosity of 30
fb^{-1}. In particular, it may be used to place an upper bound on \arg(A_t) if
indeed \arg(\mu) -> 0, as implied from the present experimental limit on the
neutron electric dipole moment. The partial rate asymmetry in the top decay
(~few \times 10^{-3}) may also be within the reach of the LHC with ~10^7 pairs
of tt-bar produced, provided detector systematics are sufficiently small. We
also show that if the GUT-scale universality of the soft breaking trilinear
terms is relaxed, then the phases associated with \arg A_u and \arg A_d can
take values up to ~few \times 10^{-1} even with squarks and gluino masses of
several hundred GeV's without contradicting the experimental limit on the
neutron electric dipole moment.Comment: 39 pages, plain latex, 20 figures embadded in the text using epsfi
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
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
Electron and Neutron Electric Dipole Moments in the Focus Point Scenario of SUGRA Model
We estimate the electron and neutron electric dipole moments in the focus
point scenario of the minimal SUGRA model corresponding to large sfermion
masses and moderate to large . There is a viable region of moderate
fine-tuning in the parameter space, around , where the
experimental limits on these electric dipole moments can be satisfied without
assuming unnaturally small phase angles. But the fine-tuning constraints become
more severe for .Comment: 16 pages, LaTeX, 4 postscript figures. Very minor changes made in
only a few sentences for clarification. Final version to appear in Phys. Rev.
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
Superstring Theory and CP- Violating Phases: Can They Be Related?
We investigate the possibility of large CP- violating phases in the soft
breaking terms derived in superstring models. The bounds on the electric dipole
moments (EDM's) of the electron and neutron are satisfied through cancellations
occuring because of the structure of the string models. Three general classes
of four-dimensional string models are considered: (i) orbifold
compactifications of perturbative heterotic string theory, (ii) scenarios based
on Ho\v{r}ava-Witten theory, and (iii) Type I string models (Type IIB
orientifolds). Nonuniversal phases of the gaugino mass parameters greatly
facilitate the necessary cancellations among the various contributions to the
EDM's; in the overall modulus limit, the gaugino masses are universal at tree
level in both the perturbative heterotic models and the Ho\v{r}ava-Witten
scenarios, which severely restricts the allowed regions of parameter space.
Nonuniversal gaugino masses do arise at one-loop in the heterotic orbifold
models, providing for corners of parameter space with phases
consistent with the phenomenological bounds. However, there is a possibility of
nonuniversal gaugino masses at tree level in the Type I models, depending on
the details of the embedding of the SM into the D- brane sectors. We find that
in a minimal model with a particular embedding of the Standard Model gauge
group into two D- brane sectors, viable large phase solutions can be obtained
over a wide range of parameter space.Comment: 28 pages, 6 figures; corrected bug in the code and a few typos,
results qualitatively unchange
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
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