251 research outputs found
Charged Lepton Flavour and CP Violations: Theoretical Impact of Present and Future Experiments
We shortly review and emphasize how l_j -> l_i gamma experiments and the
searches for lepton e.d.m. are constraining New Physics model building. They
are pure signals of new phenomena around the TeV scale since the SM
contributions are definitely negligible. It is quite remarkable that they also
give effective tests of the LFV & CPV in seesaw couplings and in grand-unified
theories. In particular, the limits on d_e nicely complement the proton decay
bounds in selecting O(10) models.Comment: 6 pages, 3 figures, Proceedings of Neutrino 04 (College de France,
Paris
Sleptonarium (Constraints on the CP and Flavour Pattern of Scalar Lepton Masses)
The constraints on the flavour and CP structure of scalar lepton mass
matrices are systematically collected. The display of the resulting upper
bounds on the lepton -slepton misalignment parameters is designed for an easy
inspection of very large classes of models and the formula are arranged so as
to suggest useful approximations. Interferences among the different
contributions to lepton flavour violating transitions and lepton electric and
magnetic dipole moments of generic character can either tighten or loose the
bounds. A combined analysis of all rare leptonic transitions can disentangle
the different contributions to yield hints on several phenomenological issues.
The possible impact of these results on the study of the slepton misalignment
originated in the seesaw mechanism and grand-unified theories is emphasized
since the planned experiments are getting close to the precision required in
such tests.Comment: 29 pages, 13 figures; v3: corrected misprints in appendix
Looking for a charge asymmetry in cosmic rays
We combine the data from PAMELA and FERMI-LAT cosmic ray experiments by
introducing a simple sum rule. This allows to investigate whether the lepton
excess observed by these experiments is charge symmetric or not. We also show
how the data can be used to predict the positron fraction at energies yet to be
explored by the AMS-02 experiment.Comment: Contribution to the proceedings of DISCRETE 2010, 5 pages, 2 figure
Dark matter from evaporating Black Holes
Light primordial black holes (PBHs) are an ideal particle factory: they emit all existing particles – of the Standard Model (SM) or beyond it – whose mass is smaller than the PBHs Hawking temperature. Evaporation of PBHs is thus an interesting mechanism for Dark Matter (DM) production. We review the status of the art of this possibility, analyzing in particular the effects of the DM particle spin, for both Schwarzschild and Kerr PBHs
Phenomenological Consequences of Soft Leptogenesis
Soft supersymmetry breaking terms involving heavy singlet sneutrinos can be
the dominant source of leptogenesis. The relevant range of parameters is
different from standard leptogenesis: a lighter Majorana mass, M < 10^9 GeV
(allowing a solution of the gravitino problem), and smaller Yukawa couplings,
Y_N < 10^{-4}. We investigate whether the various couplings of the singlet
sneutrinos, which are constrained by the requirement of successful `soft
leptogenesis', can have observable phenomenological consequences. Specifically,
we calculate the contributions of the relevant soft supersymmetric breaking
terms to the electric dipole moments of the charged leptons and to lepton
flavor violating decays. Our result is that these contributions are small.Comment: 11 pages, 1 figure; v2: an additional contribution is considered
(modifying: fig. 1, eq. 10-13, 22) and a reference added. Conclusions
unchange
Yukawa coupling and anomalous magnetic moment of the muon: an update for the LHC era
We study the interplay between a soft muon Yukawa coupling generated
radiatively with the trilinear A-terms of the minimal supersymmetric standard
model (MSSM) and the anomalous magnetic moment of the muon. In the absence of a
tree-level muon Yukawa coupling the lightest smuon mass is predicted to be in
the range between 750 GeV and 2700 GeV at 2 sigma, if the bino mass M_1 is
below 1 TeV. Therefore, a detection of a smuon (in conjunction with a sub-TeV
bino) at the LHC would directly imply a non-zero muon Yukawa coupling in the
MSSM superpotential. Inclusion of slepton flavor mixing could in principle
lower the mass of one smuon-like slepton below 750 GeV. However, the
experimental bounds on radiative lepton decays instead strengthen the lower
mass bound, with larger effects for smaller M_1, We also extend the analysis to
the electron case and find that a light selectron close to the current
experimental search limit may prove the MSSM electron Yukawa coupling to be
non-zero.Comment: 6 pages, 2 figures, references added, version accepted for
publication in PR
Detecting the Cold Spot as a Void with the Non-Diagonal Two-Point Function
The anomaly in the Cosmic Microwave Background known as the "Cold Spot" could
be due to the existence of an anomalously large spherical (few hundreds Mpc/h
radius) underdense region, called a "Void" for short. Such a structure would
have an impact on the CMB also at high multipoles l through Lensing. This would
then represent a unique signature of a Void. Modeling such an underdensity with
an LTB metric, we show that the Lensing effect leads to a large signal in the
non-diagonal two-point function, centered in the direction of the Cold Spot,
such that the Planck satellite will be able to confirm or rule out the Void
explanation for the Cold Spot, for any Void radius with a Signal-to-Noise ratio
of at least O(10).Comment: v1: 6 pages, 2 figures; v2: 6 pages, 2 figures, text improved, to
appear on JCA
New Physics summary
We introduce the various contributions to the New Physics Session by identifying four main areas: Higgs-like signatures, supersymmetry, exotica and lepton flavour violation searches
Probing New Physics through mu-e Universality in K->lnu
The recent NA48/2 improvement on R_K=Gamma(K->e nu_e)/Gamma(K->mu nu_mu)
emphasizes the role of K_l2 decays in probing the mu-e universality.
Supersymmetric (SUSY) extensions of the Standard Model can exhibit mu-e
non-universal contributions. Their origin is twofold: those deriving from
lepton flavor conserving couplings are subdominant with respect to those
arising from lepton flavor violating (LFV) sources. We show that mu-e
non-universality in K_l2 is quite effective in constraining relevant regions of
SUSY models with LFV (for instance, supergravities with a see-saw mechanism for
neutrino masses). A comparison with analogous bounds coming from tau LFV decays
proves the relevance of the measurement of R_K to probe LFV in SUSY.Comment: v2: 5 pages, 1 figure. Comments and 2 references adde
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