449 research outputs found
Charge Breaking Minima in the Broken R-parity Minimal Supersymmetric Standard Model
We reconsider the possible presence of charge and colour breaking minima in
the scalar potential of the minimal supersymmetric standard model (MSSM) and
its minimal generalization with R-parity explicitly broken by bilinear terms
(RMSSM). First we generalize some results previously derived for the MSSM case.
Next we investigate how robust is the MSSM against its RMSSM extension. We
examine the constraints on the RMSSM parameter space that follow from the
required absence of charge breaking minima in the scalar potential. We point
out the possibility of generating non--zero vacuum expectation values for the
charged Higgs field which is not present in the MSSM. However, given the
smallness of neutrino masses indicated by neutrino oscillation data, we show
that the RMSSM represents only a slight perturbation of the MSSM and is thus as
safe (or unsafe) as the MSSM itself from unwanted minima in the scalar
potential.Comment: Latex 16 pages, 2 figure
Phenomenology of LFV at low-energies and at the LHC: strategies to probe the SUSY seesaw
We study the impact of a type-I SUSY seesaw concerning lepton flavour
violation (LFV) at low-energies and at the LHC. At the LHC, decays, in combination with other
observables, render feasible the reconstruction of the masses of the
intermediate sleptons, and hence the study of mass
differences. If interpreted as being due to the violation of lepton flavour,
high-energy observables, such as large slepton mass splittings and flavour
violating neutralino and slepton decays, are expected to be accompanied by
low-energy manifestations of LFV such as radiative and three-body lepton
decays. We discuss how to devise strategies based in the interplay of slepton
mass splittings as might be observed at the LHC and low-energy LFV observables
to derive important information on the underlying mechanism of LFV.Comment: 6 pages, 4 figures. To appear in the proceedings of the 11th
International Workshop on Tau Lepton Physics (TAU2010), Manchester, UK, 13-17
September 201
Thermal leptogenesis in extended supersymmetric seesaw
We consider an extended supersymmetric SO(10) seesaw model with only doublet
Higgs scalars, in which neutrino masses are suppressed by the scale of D-parity
violation. Leptogenesis can occur at the TeV scale through the decay of a
singlet Sigma, thereby avoiding the gravitino crisis. Washout of the asymmetry
can be effectively suppressed by the absence of direct couplings of Sigma to
leptons.Comment: 4 pages, 5 figure
Supersymmetric type-III seesaw: lepton flavour violating decays and dark matter
We study a supersymmetric version of the seesaw mechanism type-III. The model
consists of the MSSM particle content plus three copies of 24 superfields. The
fermionic part of the SU(2) triplet contained in the 24 is responsible for the
type-III seesaw, which is used to explain the observed neutrino masses and
mixings. Complete copies of 24 are introduced to maintain gauge coupling
unification. These additional states change the beta functions of the gauge
couplings above the seesaw scale. Using mSUGRA boundary conditions we calculate
the resulting supersymmetric mass spectra at the electro-weak scale using full
2-loop renormalization group equations. We show that the resulting spectrum can
be quite different compared to the usual mSUGRA spectrum. We discuss how this
might be used to obtain information on the seesaw scale from mass measurements.
Constraints on the model space due to limits on lepton flavour violating decays
are discussed. The main constraints come from the bounds on the decay mu to e
and gamma but there are also regions where the decay tau to mu and gamma gives
stronger constraints. We also calculate the regions allowed by the dark matter
constraint. For the sake of completeness, we compare our results with those for
the supersymmetric seesaw type-II and, to some extent, with type-I.Comment: 32 pages, 16 eps figures. One ref. added; small changes in tex
Lepton flavour violation: physics potential of a Linear Collider
We revisit the potential of a Linear Collider concerning the study of lepton
flavour violation, in view of new LHC bounds and of the (very) recent
developments in lepton physics. Working in the framework of a type I
supersymmetric seesaw, we evaluate the prospects of observing seesaw-induced
lepton flavour violating final states of the type e \mu + missing energy,
arising from e+ e- and e- e- collisions. In both cases we address the potential
background from standard model and supersymmetric charged currents. We also
explore the possibility of electron and positron beam polarisation. The
statistical significance of the signal, even in the absence of kinematical
and/or detector cuts, renders the observation of such flavour violating events
feasible over large regions of the parameter space. We further consider the
\mu-\mu- + E^T_miss final state in the e- e- beam option finding that, due to a
very suppressed background, this process turns out to be a truly clear probe of
a supersymmetric seesaw, assuming the latter to be the unique source of lepton
flavour violation.Comment: 30 pages, 48 figure
Potential of a Linear Collider for Lepton Flavour Violation studies in the SUSY seesaw
We study the potential of an e+- e- Linear Collider for charged lepton
flavour violation studies in a supersymmetric framework where neutrino masses
and mixings are explained by a type-I seesaw. Focusing on e-mu flavour
transitions, we evaluate the background from standard model and supersymmetric
charged currents to the e mu + missing E_T signal. We study the energy
dependence of both signal and background, and the effect of beam polarisation
in increasing the signal over background significance. Finally, we consider the
mu- mu- + missing E_T final state in e- e- collisions that, despite being
signal suppressed by requiring two e-mu flavour transitions, is found to be a
clear signature of charged lepton flavour violation due to a very reduced
standard model background.Comment: 8 pages, 5 figures. To appear in the proceedings of "DISCRETE 2012 -
3rd Symposium on Prospects in the Physics of Discrete Symmetries", Lisbon,
Portugal, 3-7 December 201
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