80 research outputs found
Neutrino Oscillations from Supersymmetry without R-parity - Its Implications on the Flavor Structure of the Theory
We discuss here some flavor structure aspects of the complete theory of
supersymmetry without R-parity addressed from the perspective of fitting
neutrino oscillation data based on the recent Super-Kamiokande result. The
single-VEV parametrization of supersymmetry without R-parity is first reviewed,
illustrating some important features not generally appreciated. For the flavor
structure discussions, a naive, flavor model independent, analysis is
presented, from which a few interesting things can be learned.Comment: 1+10 pages latex, no figure; Invited talk at NANP 99 conference,
Dubna (Jun 28 - Jul 3) --- submission for the proceeding
Flavor Changing Scalar Interactions
The smallness of fermion masses and mixing angles has recently been been
attributed to approximate global symmetries, one for each fermion type.
The parameters associated with these symmetry breakings are estimated here
directly from observed masses and mixing angles. It turns out that although
flavor changing reaction rates may be acceptably small in electroweak theories
with several scalar doublets without imposing any special symmetries on the
scalars themselves, such theories generically yield too much CP violation in
the neutral kaon mass matrix. Hence in these theories CP must also be a good
approximate symmetry. Such models provide an alternative mechanism for CP
violation and have various interesting phenomenological features.Comment: 18 pages. UTTG-22-92; LBL 33016; UCB 92/3
The Anomalous Magnetic Moment of the Muon and Higgs-Mediated Flavor Changing Neutral Currents
In the two-Higgs doublet extension of the standard model, flavor-changing
neutral couplings arise naturally. In the lepton sector, the largest such
coupling is expected to be $\mu-\tau-\phi#. We consider the effects of this
coupling on the anomalous magnetic moment of the muon. The resulting bound on
the coupling, unlike previous bounds, is independent of the value of other
unknown couplings. It will be significantly improved by the upcoming E821
experiment at Brookhaven National Lab.Comment: 7 pages Latex, 2 figure
Approximate Flavor Symmetries in the Lepton Sector
Approximate flavor symmetries in the quark sector have been used as a handle
on physics beyond the Standard Model. Due to the great interest in neutrino
masses and mixings and the wealth of existing and proposed neutrino experiments
it is important to extend this analysis to the leptonic sector. We show that in
the see-saw mechanism, the neutrino masses and mixing angles do not depend on
the details of the right-handed neutrino flavor symmetry breaking, and are
related by a simple formula. We propose several ans\"{a}tze which relate
different flavor symmetry breaking parameters and find that the MSW solution to
the solar neutrino problem is always easily fit. Further, the oscillation is unlikely to solve the atmospheric neutrino problem
and, if we fix the neutrino mass scale by the MSW solution, the neutrino masses
are found to be too small to close the Universe.Comment: 12 pages (no figures), LBL-3459
Protecting the Primordial Baryon Asymmetry From Erasure by Sphalerons
If the baryon asymmetry of the universe was created at the GUT scale,
sphalerons together with exotic sources of -violation could have erased
it, unless the latter satisfy stringent bounds. We elaborate on how the small
Yukawa coupling of the electron drastically weakens previous estimates of these
bounds.Comment: 41 pp., 4 latex figures included and 3 uuencoded or postscript
figures available by request, UMN-TH-1213-9
On Preserving a B+L Asymmetry Produced in the Early Universe
One of the most efficient mechanisms for producing the baryon asymmetry of
the Universe is the decay of scalar condensates in a SUSY GUT as was first
suggested by Affleck and Dine. We show that given a large enough asymmetry, the
baryon number will be preserved down to low temperatures even if B - L = 0,
because the baryon number carrying scalars form bose condensates that give the
W a mass. We derive the conditions on the condensate needed to suppress
electroweak sphaleron interactions which would otherwise drive the baryon
asymmetry to zero when B - L = 0.Comment: 10 pages, LaTeX, UMN-TH-1240, CfPA-TH-94-13, LBL-3527
Probing flavor changing interactions in hadron collisions
The subprocess in the two-Higgs-doublet model with
flavor-changing scalar couplings is examined at the one loop level. With
perturbative QCD factorization theorem, the corresponding cross sections for
hadron-hadron collisions are computed numerically. The results are applicable
to the whole mass range of the weakly coupled Higgs bosons. In case we could
efficiently exclude the severe backgrounds of the
production signal, probing the flavor-changing top-charm-scalar vertex at
hadron colliders would be very promising and accessible experimentally.Comment: LaTex file, 14 pages, 8 EPS figure
Flavor at the TeV Scale with Extra Dimensions
Theories where the Standard Model fields reside on a 3-brane, with a low
fundamental cut-off and extra dimensions, provide alternative solutions to the
gauge hierarchy problem. However, generating flavor at the TeV scale while
avoiding flavor-changing difficulties appears prohibitively difficult at first
sight. We argue to the contrary that this picture allows us to lower flavor
physics close to the TeV scale. Small Yukawa couplings are generated by
``shining'' badly broken flavor symmetries from distant branes, and flavor and
CP-violating processes are adequately suppressed by these symmetries. We
further show how the extra dimensions avoid four dimensional disasters
associated with light fields charged under flavor. We construct elegant and
realistic theories of flavor based on the maximal U(3)^5 flavor symmetry which
naturally generate the simultaneous hierarchy of masses and mixing angles.
Finally, we introduce a new framework for predictive theories of flavor, where
our 3-brane is embedded within highly symmetrical configurations of
higher-dimensional branes.Comment: 40 pages, 8 figure
at Hadron Colliders
We study the observability for a lepton flavor-changing decay of a Higgs
boson at hadron colliders. Flavor-changing couplings of a Higgs
boson exist at tree level in models with multiple Higgs doublets. The
coupling is particularly motivated by the favorable intepretation of
oscillation. We find that at the Tevatron Run II the unique
signature could serve as the Higgs discovery channel, surpassing
expectations for Higgs boson searches in the SM and in a large parameter region
of the MSSM. The sensitivity will be greatly improved at the LHC, beyond the
coverage at a muon collider Higgs factory.Comment: 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
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