780 research outputs found
Slepton Oscillation at Large Hadron Collider
Measurement of Lepton-Flavor Violation (LFV) in the minimal SUSY Standard
Model (MSSM) at Large Hadron Collider (LHC) is studied based on a realistic
simulation. We consider the LFV decay of the second-lightest neutralino,
, in the case
where the flavor mixing exists in the right-handed sleptons. We scan the
parameter space of the minimal supergravity model (MSUGRA) and a more generic
model in which we take the Higgsino mass as a free parameter. We find
that the possibility of observing LFV at LHC is higher if is smaller than
the MSUGRA prediction; the LFV search at LHC can cover the parameter range
where the decay can be suppressed by the cancellation among
the diagrams for this case.Comment: 29 pages, 10 figure
Probing Left-handed Slepton Flavor Mixing at Future Lepton Colliders
It has been argued in the literature that the search for the slepton
oscillation phenomenon can be a powerful probe of intergenerational mixing
between sleptons, once sleptons are found at future colliders. In this article
we estimate possible reach of future lepton colliders in probing left-handed
slepton flavor mixing, especially mixing between the first and third
generations, on which constraints imposed by other processes like are very weak. collider is suitable for this purpose, since it
can produce, if kinematically allowed, sleptons of the first generation via
t-channel, in addition to s-channel. Utilizing e^+e^- \to \tau e + 4jets + \E
signal at linear collider with integrated luminosity L=50 fb^{-1}(500
fb^{-1}) it may be possible to reach mixing angle and mass difference GeV for sneutrinos in the first and third generations at the
statistical significance of 5 \sigma.Comment: 27 pages, 6 figures. A new section added. Conclusion unchanged. To
appear in Phys. Rev.
Lepton flavor violation at linear collider experiments in supersymmetric grand unified theories
Lepton flavor violation at linear collider experiments is discussed. We show
that detectable lepton flavor violation could occur through scalar lepton pair
production and decay in the supersymmetric SU(5) grand unified theory in spite
of the stringent present experimental constraints by rare process searches.
Possible cross sections about 40fb for an e+e- collider and 280fb for an e-e-
collider are illustrated.Comment: 12 pages, including 3 figures, REVTeX, eps
A New Parametrization of the Seesaw Mechanism and Applications in Supersymmetric Models
We present a new parametrization of the minimal seesaw model, expressing the
heavy-singlet neutrino Dirac Yukawa couplings and Majorana
masses in terms of effective light-neutrino observables and an
auxiliary Hermitian matrix In the minimal supersymmetric version of the
seesaw model, the latter can be related directly to other low-energy
observables, including processes that violate charged lepton flavour and CP.
This parametrization enables one to respect the stringent constraints on
muon-number violation while studying the possible ranges for other observables
by scanning over the allowed parameter space of the model. Conversely, if any
of the lepton-flavour-violating process is observed, this measurement can be
used directly to constrain and As applications, we
study flavour-violating decays and the electric dipole moments of
leptons in the minimal supersymmetric seesaw model.Comment: Important references adde
Not Even Decoupling Can Save Minimal Supersymmetric SU(5)
We make explicit the statement that Minimal Supersymmetric SU(5) has been
excluded by the Super-Kamiokande search for the process . This exclusion is made by first placing limits on the colored
Higgs triplet mass, by forcing the gauge couplings to unify. We also show that
taking the superpartners of the first two generations to be very heavy in order
to avoid flavor changing neutral currents, the so-called ``decoupling'' idea,
is insufficient to resurrect the Minimal SUSY SU(5). We comment on various
mechanisms to further suppress proton decay in SUSY SU(5). Finally, we address
the contributions to proton decay from gauge boson exchange in the Minimal SUSY
SU(5) and flipped SU(5) models.Comment: 8 pages, 4 figure
Horizontal symmetry in Higgs sector of GUT with U(1)_A symmetry
In a series of papers, we pointed out that an anomalous gauge
symmetry naturally solves various problems in grand unified theories (GUTs) and
that a horizontal gauge symmetry, or , not only realizes the
unification of three generation quarks and leptons in fewer multiplets but also
solves the supersymmetric flavor problem. In this paper, we examine the
possibility that the Higgs sectors of the GUT symmetry and of the horizontal
symmetry are unified, that is, there are some Higgs fields whose vacuum
expectation values (VEVs) break both the GUT gauge symmetry and the horizontal
symmetry at the same time. Although the scale of the VEVs become too large to
suppress the flavor changing neutral current processes sufficiently, the
unification is possible. In addition, for the models, the
gauge anomaly is cancelled in the unified models without introducing additional
fields in contrast with the previous models in which the Higgs sectors are not
unified.Comment: 35 page
Slepton mass-splittings as a signal of LFV at the LHC
Precise measurements of slepton mass-splittings might represent a powerful
tool to probe supersymmetric (SUSY) lepton flavour violation (LFV) at the LHC.
We point out that mass-splittings of the first two generations of sleptons are
especially sensitive to LFV effects involving transitions. If these
mass-splittings are LFV induced, high-energy LFV processes like the neutralino
decay {\nt}_2\to\nt_1\tau^{\pm}\mu^{\mp} as well as low-energy LFV processes
like are unavoidable. We show that precise slepton
mass-splitting measurements and LFV processes both at the high- and low-energy
scales are highly complementary in the attempt to (partially) reconstruct the
flavour sector of the SUSY model at work. The present study represents another
proof of the synergy and interplay existing between the LHC, i.e. the {\em
high-energy frontier}, and high-precision low-energy experiments, i.e. the {\em
high-intensity frontier}.Comment: 11 pages, 5 figures. v2: added discussion on backgrounds, added
references, version to be published on JHE
Searches for Lepton Flavour Violation at a Linear Collider
We investigate the prospects for detection of lepton flavour violation in
sparticle production and decays at a Linear Collider (LC), in models guided by
neutrino oscillation data. We consider both slepton pair production and
sleptons arising from the cascade decays of non-leptonic sparticles. We study
the expected signals when lepton-flavour-violating (LFV) interactions are
induced by renormalization effects in the Constrained Minimal Supersymmetric
extension of the Standard Model (CMSSM), focusing on the subset of the
supersymmetric parameter space that also leads to cosmologically interesting
values of the relic neutralino LSP density. Emphasis is given to the
complementarity between the LC, which is sensitive to mixing in both the left
and right slepton sectors, and the LHC, which is sensitive primarily to mixing
in the right sector. We also emphasize the complementarity between searches for
rare LFV processes at the LC and in low-energy experiments.Comment: 19 pages, 10 figure
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