1,088 research outputs found
Multiphoton signals of a (96 GeV?) stealth boson
Cascade decays of new scalars into final states with multiple photons and
possibly quarks may lead to distinctive experimental signatures at high-energy
colliders. Such signals are even more striking if the scalars are highly
boosted, as when produced from the decay of a much heavier resonance. We study
this type of events within the framework of the minimal stealth boson model, an
anomaly-free extension of the Standard Model with two
complex scalar singlets. It is shown that, while those signals may have cross
sections that might render them observable with LHC Run 2 data, they have
little experimental coverage. We also establish a connection with a CMS excess
observed in searches for new scalars decaying into diphoton final states near
96 GeV. In particular, we conclude that the predicted multiphoton signatures
are compatible with such excess.Comment: LaTeX 32 pages. Comments added and discussions extended. Final
version in EPJ
A closer look at the possible CMS signal of a new gauge boson
The CMS collaboration has recently reported a 2.8 excess of
events with an invariant mass around 2 TeV. This observation can be explained
in the context of standard model extensions with new gauge bosons ,
and heavy neutrinos coupling (mainly) to the electron. We discuss additional
signals that allow to confirm or discard the and hypotheses.Comment: ReVTeX 5 page
A new bridge between leptonic CP violation and leptogenesis
Flavor effects due to lepton interactions in the early Universe may have
played an important role in the generation of the cosmological baryon asymmetry
through leptogenesis. If the only source of high-energy CP violation comes from
the left-handed leptonic sector, then it is possible to establish a bridge
between flavored leptogenesis and low-energy leptonic CP violation. We explore
this connection taking into account our present knowledge about low-energy
neutrino parameters and the matter-antimatter asymmetry observed in the
Universe. In this framework, we find that leptogenesis favors a hierarchical
light neutrino mass spectrum, while for quasi-degenerate and inverted
hierarchical neutrino masses there is a very narrow allowed window. The
absolute neutrino mass scale turns out to be m < 0.1 eV.Comment: 10 pages, 3 figure
Spontaneous leptonic CP violation and nonzero
We consider a simple extension of the Standard Model by adding two Higgs
triplets and a complex scalar singlet to its particle content. In this
framework, the CP symmetry is spontaneously broken at high energies by the
complex vacuum expectation value of the scalar singlet. Such a breaking leads
to leptonic CP violation at low energies. The model also exhibits an flavour symmetry which, after being spontaneously broken at a high-energy
scale, yields a tribimaximal pattern in the lepton sector. We consider small
perturbations around the tribimaximal vacuum alignment condition in order to
generate nonzero values of , as required by the latest neutrino
oscillation data. It is shown that the value of recently measured
by the Daya Bay Reactor Neutrino Experiment can be accommodated in our
framework together with large Dirac-type CP violation. We also address the
viability of leptogenesis in our model through the out-of-equilibrium decays of
the Higgs triplets. In particular, the CP asymmetries in the triplet decays
into two leptons are computed and it is shown that the effective leptogenesis
and low-energy CP-violating phases are directly linked.Comment: 17 pages; 6 figures; references added and typos corrected. Final
version to appear in PR
Lepton flavour violation in the supersymmetric type-II seesaw mechanism
We summarize the predictions for the radiative decays l_j->l_i \gamma within
the context of the supersymmetric type II seesaw mechanism considering
universal boundary conditions for the soft SUSY breaking terms. The dependence
on the low-energy neutrino parameters is discussed and the deviations from the
analytical results for large analyzed.Comment: 3 pages, 4 figures. To appear in the proceedings of 16th
International Conference on Supersymmetry and the Unification of Fundamental
Interactions (SUSY08), Seoul, Korea, 16-21 Jun 200
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