1,009 research outputs found
Compatibility of various approaches to heavy-quark fragmentation
We find that the definition of the heavy-quark fragmentation function given
by Jaffe and Randall differs by a factor of the longitudinal-momentum fraction
z from the standard Collins-Soper definition. Once this factor is taken into
account, the explicit calculation of Braaten et al. is found to be in agreement
with the general analysis of Jaffe and Randall. We also examine the model of
Peterson et al. for heavy-quark fragmentation and find that the quoted values
of the width and of the value of at the maximum are in error. The corrected
values are in agreement with the analysis of Jaffe and Randall.Comment: 4 pages late
CP Violation and Dark Matter
A brief review is given of the effects of CP violation on the direct
detection of neutralinos in dark matter detectors. We first summarize the
current developments using the cancellation mechanism which allows for the
existence of large CP violating phases consistent with experimental limits on
the electron and on the neutron electric dipole moments in a broad class of
SUSY, string and D brane models. We then discuss their effects on the
scattering of neutralinos from quarks and on the event rates. It is found that
while CP effects on the event rates can be enormous such effects are reduced
significantly with the imposition of the EDM constraints. However, even with
the inclusion of the EDM constraints the effects are still very significant and
should be included in a precision prediction of event rates in any SUSY, string
or D brane model.Comment: Based on an invited talk at the conference "Sources and Detection of
Dark Matter in the Universe", at Marina del Rey, CA, Feb. 23-25, 2000; 12
pages, Latex including 2 figure
On the EDM Cancellations in D-brane models
We analyze the possibility of simultaneous electron, neutron, and mercury
electric dipole moment (EDM) cancellations in the mSUGRA and D--brane models.
We find that the mercury EDM constraint practically rules out the cancellation
scenario in D-brane models whereas in the context of mSUGRA it is still allowed
with some fine-tuning.Comment: 10 pages, to appear in Phys. Rev. Let
Global fits to neutrino oscillation data
I summarize the determination of neutrino oscillation parameters within the
three-flavor framework from world neutrino oscillation data with date of May
2006, including the first results from the MINOS long-baseline experiment. It
is illustrated how the determination of the leading "solar" and "atmospheric"
parameters, as well as the bound on emerge from an interplay of
various complementary data sets. Furthermore, I discuss possible implications
of sub-leading three-flavor effects in present atmospheric neutrino data
induced by and for the bound on
and non-maximal values of , emphasizing, however, that these
effects are not statistically significant at present. Finally, in view of the
upcoming MiniBooNE results I briefly comment on the problem to reconcile the
LSND signal.Comment: 5 pages, 5 figures, talk presented at the SNOW2006 workshop,
Stockholm, 2-6 May 200
Grand Unification Scale CP Violating Phases And The Electric Dipole Moment
The question of CP violating phases in supersymmetry and electric dipole
moments (EDMs) is considered within the framework of supergravity grand
unification (GUT) models with a light (1 TeV) mass
spectrum. In the minimal model, the nearness of the t-quark Landau pole
automatically suppresses the t-quark cubic soft breaking phase at the
electroweak scale. However, current EDM data require the quadratic soft
breaking phase to be small at the electroweak scale unless tan is small
(tan3), and the EDM data combined with the requirement
of electroweak symmetry breaking require this phase to be both large and highly
fine tuned at the GUT scale unless tan is small. Non minimal models are
also examined, and generally show the same behavior.Comment: 28 pages, latex, 15 figure
Supersymmetric CP Violation in in Minimal Supergravity Model
Direct CP asymmetries and the CP violating normal polarization of lepton in
inclusive decay B \to X_s l^+ l^- are investigated in minimal supergravity
model with CP violating phases. The contributions coming from exchanging
neutral Higgs bosons are included. It is shown that the direct CP violation in
branching ratio, A_{CP}^1, is of {\cal{O}}(10^{-3}) for l=e, \mu, \tau. The CP
violating normal polarization for l=\mu can reach 0.5 percent when tan\beta is
large (say, 36). For l=\tau and in the case of large \tan\beta, the direct CP
violation in backward-forward asymmetry, A_{CP}^2, can reach one percent, the
normal polarization of \tau can be as large as a few percent, and both are
sensitive to the two CP violating phases, \phi_\mu and \phi_{A_0}, and
consequently it could be possible to observe them (in particular, the normal
polarization of \tau) in the future B factories.Comment: 14 pages, latex, 5 figure
and processes with polarized muons and supersymmetric grand unified theories
and processes are
analyzed in detail with polarized muons in supersymmetric grand unified
theories. We first present Dalitz plot distribution for decay based on effective Lagrangian with general
lepton-flavor-violating couplings and define various P- and T-odd asymmetries.
We calculate branching ratios and asymmetries in supersymmetric SU(5) and
SO(10) models taking into account complex soft supersymmetry breaking terms.
Imposing constraints from experimental bounds on the electron, neutron and
atomic electric dipole moments, we find that the T-odd asymmetry for can be 15% in the SU(5) case. P-odd asymmetry with respect
to muon polarization for varies from -20% to -100%
for the SO(10) model while it is in the SU(5) case. We also show that
the P-odd asymmetries in and the ratio of
and branching
fractions are useful to distinguish different models.Comment: 52 pages, 15 figure
Weak Isospin Violations in Charged and Neutral Higgs Couplings from SUSY Loop Corrections
Supersymmetric QCD and supersymmetric electroweak loop corrections to the
violations of weak isospin to Yukawa couplings are investigated. Specifically
it involves an analysis of the supersymmetric loop corrections to the Higgs
couplings to the third generation quarks and leptons. Here we analyze the SUSY
loop corrections to the charged Higgs couplings which are then compared with
the supersymmetric loop corrections to the neutral Higgs couplings previously
computed. It is found that the weak isospin violations can be quite
significant, i.e, as much as 40-50% or more of the total loop correction to the
Yukawa coupling. The effects of CP phases are also studied and it is found that
these effects can either enhance or suppress the weak isospin violations. We
also investigate the weak isospin violation effects on the branching ratio
and show that the effects
are sensitive to CP phases. Thus an accurate measurement of this branching
ratio along with the branching ratio of the neutral Higgs boson decays can
provide a measure of weak isospin violation along with providing a clue to the
presence of supersymmetry.Comment: 20 pages, 9 figure
A new limit on the permanent electric dipole moment of ^{199}Hg
We present the first results of a new search for a permanent electric dipole
moment of the ^{199}Hg atom using a UV laser. Our measurements give d(Hg)= -
(1.06 +/- 0.49 +/- 0.40) 10^{-28} e cm. We interpret the result as an upper
limit |d(Hg)| < 2.1 10^{-28} e cm (95% C.L.), which sets new constraints on
theta_{QCD}, chromo-EDMs of the quarks, and CP violation in Supersymmetric
models.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Mixing of the CP Even and the CP Odd Higgs Bosons and the EDM Constraints
The mixing among the CP even and the CP odd neutral Higgs bosons of MSSM by
one loop induced effects in the presence of CP phases is investigated using
three different mechanisms to satisfy the EDM constraints, i.e., a fine tuning
of phases, a heavy sparticle spectrum, and the cancellation mechanism. It is
shown that if a mixing effect among the CP even and the CP odd Higgs bosons is
observed experimentally, then it is only the cancellation mechanism that can
survive under the naturalness constraint.Comment: 14 pages, Latex and 4figures. A new paragraph is added and few more
references. One figure is modified. To appear in Phys. Rev.
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