271 research outputs found
Flavour always matters in scalar triplet leptogenesis
We present a flavour-covariant formalism for scalar triplet leptogenesis,
which takes into account the effects of the different lepton flavours in a
consistent way. Our main finding is that flavour effects can never be neglected
in scalar triplet leptogenesis, even in the temperature regime where all
charged lepton Yukawa interactions are out of equilibrium. This is at variance
with the standard leptogenesis scenario with heavy Majorana neutrinos. In
particular, the so-called single flavour approximation leads to predictions for
the baryon asymmetry of the universe that can differ by a large amount from the
flavour-covariant computation in all temperature regimes. We investigate
numerically the impact of flavour effects and spectator processes on the
generated baryon asymmetry, and find that the region of triplet parameter space
allowed by successsful leptogenesis is significantly enlarged.Comment: 43 pages, 15 figures; comments and references added, cosmetic changes
in Figs. 6 to 8, results unaffected. Version to appear in JHE
A light neutralino in hybrid models of supersymmetry breaking
We show that in gauge mediation models where heavy messenger masses are
provided by the adjoint Higgs field of an underlying SU(5) theory, a
generalized gauge mediation spectrum arises with the characteristic feature of
having a neutralino LSP much lighter than in the standard gauge or gravity
mediation schemes. This naturally fits in a hybrid scenario where gravity
mediation, while subdominant with respect to gauge mediation, provides mu and
Bmu parameters of the appropriate size for electroweak symmetry breaking.Comment: 32 pages. v2: revised discussions of the generation of Bmu and of the
dark matter constraint; numerous small redactional changes; remarks and
references adde
Flavour violation in supersymmetric SO(10) unification with a type II seesaw mechanism
We study flavour violation in a supersymmetric SO(10) implementation of the
type II seesaw mechanism, which provides a predictive realization of triplet
leptogenesis. The experimental upper bounds on lepton flavour violating
processes have a significant impact on the leptogenesis dynamics, in particular
they exclude the strong washout regime. Requiring successful leptogenesis then
constrains the otherwise largely unknown overall size of flavour-violating
observables, thus yielding testable predictions. In particular, the branching
ratio for mu -> e gamma lies within the reach of the MEG experiment if the
superpartner spectrum is accessible at the LHC, and the supersymmetric
contribution to epsilon_K can account for a significant part of the
experimental value. We show that this scenario can be realized in a consistent
SO(10) model achieving gauge symmetry breaking and doublet-triplet splitting in
agreement with the proton decay bounds, improving on the MSSM prediction for
alpha_3(m_Z), and reproducing the measured quark and lepton masses.Comment: 40 pages, 10 figures. Accepted for publication in JHE
Flavour Changing Neutral Currents and Inverted Sfermion Mass Hierarchy
We study the contraints on non-flavour-blind soft supersymmetry breaking
terms coming from flavour and CP violating processes in the presence of
hierarchical Yukawa couplings, and quantify how much these constraints are
weakened in the regions of the MSSM parameter space characterized by heavy
gauginos and multi-TeV sfermion masses, respectively. We also study the
inverted sfermion mass hierarchy scenario in the context of D-term
supersymmetry breaking, and show that generic hierarchical Yukawa couplings
with arbitrary phases require first generation squarks in the few 10 TeV range.Comment: 9 pages, 6 figures. Talk given at the XLth Rencontres de Moriond on
Electroweak Interactions and Unified Theories, La Thuile, Aosta Valley,
Italy, 5-12 March 2005. V3: one reference correcte
A Comment on Self-Tuning and Vanishing Cosmological Constant in the Brane World
In this note we elaborate on various five dimensional contributions to the
effective 4D cosmological constant in brane systems. In solutions with
vanishing 5D cosmological constant we describe a non-local mechanism of
cancellation of vacuum energy between the brane and the singularities. We
comment on a hidden fine tuning which is implied by this observation.Comment: 7 pages, Latex, final version to appear in Phys. Lett.
Poly(amidoamine)s synthesis, characterisation and interaction with BSA
Cationic poly(amidoamine)s (PAAs) were synthesised and characterised by NMR and gel permeation chromatography. Their thermal properties were investigated using thermogravimetric analysis and differential scanning calorimetry. Although poly(amidoamine)s have been used as endosomolytic polymers for protein intracellular delivery, the interaction of the polymers with the proteins still need to be investigated. BSA was used as a model protein and complexation with the different poly(amidoamine) s was investigated using gel retardation assays, fluorescence spectroscopy and high sensitivity differential scanning calorimetry. Our results indicate that the thermal stability of BSA was affected upon interaction and complexation with the poly(amidoamine)s, however these interactions did not seem to modify the structure of the protein. Polymer flexibility seemed to favour polymer/protein complexation and promoted thermal stability
Leptogenesis in SO(10) models with a left-right symmetric seesaw mechanism
We study leptogenesis in supersymmetric SO(10) models with a left-right
symmetric seesaw mechanism, including flavour effects and the contribution of
the next-to-lightest right-handed neutrino. Assuming M_D = M_u and hierarchical
light neutrino masses, we find that successful leptogenesis is possible for 4
out of the 8 right-handed neutrino mass spectra that are compatible with the
observed neutrino data. An accurate description of charged fermion masses
appears to be an important ingredient in the analysis.Comment: Submitted for the SUSY07 proceedings, 4 pages, 9 figure
- …