50 research outputs found
Parametrizing the Neutrino sector
The original Standard Model has massless neutrinos, but the observation of
neutrino oscillations requires that neutrinos are massive. The simple extension
of adding gauge singlet fermions to the particle spectrum allows normal Yukawa
mass terms for neutrinos. The seesaw mechanism then suggests an explanation for
the observed smallness of the neutrino masses. After reviewing the framework of
the seesaw we suggest a parametrization that directly exhibits the smallness of
the mass ratios in the seesaw for an arbitrary number of singlet fermions and
we present our plans to perform calculations for a process that might be
studied at the LHC.Comment: 8 pages; uses appolb.cls; submitted to the proceedings of "Matter to
the Deepest: Recent Development in Physics of Fundamental Interactions",
Ustron, Poland, 12-18 Sep 201
Gauge dependence of tadpole and mass renormalization for a seesaw extended 2HDM
We study the gauge dependence of the neutrino mass renormalization in a two
Higgs doublet model, that is extended with one singlet seesaw neutrino. This
model gives only one light neutrino a mass at tree level, while the second
light mass is generated at loop level via the interaction with the second Higgs
doublet. At one loop level, one neutrino stays massless. We use multiplicative
renormalization constants to define counterterms. The renormalized mass
parameters are defined as the complex poles of the propagators, using the
complex mass scheme for mass renormalization. With this setup, we analytically
get the expressions for the neutrino mass counterterms and isolate the gauge
dependent part. We show, how relating this gauge dependent part with the
tadpole renormalization leads to gauge independent counterterm definitions,
hence gauge independent bare masses for neutrinos.Comment: 12 pages; v2: added 2 references and corrected 2 typos: indexes in
eq.(3) and on page 9 (the the -> that the
Charged lepton flavor violating processes in the Grimus-Neufeld model
Charged Lepton Flavour Violating (cLFV) decays constrain the relationship
between the neutrino and the scalar sectors of the Grimus-Neufeld model (GNM),
an appealing minimal model of neutrino masses. It turns out, that in the
scenario, where the seesaw scale is lower than the electroweak one, cLFV is
completely defined by the new Yukawa interactions between the additional single
heavy Majorana neutrino, the second Higgs doublet and the lepton doublets.
Therefore, we derive a useful parameterization for the Yukawa couplings which
reproduces by construction the correct PMNS matrix and the correct neutrino
masses for both Normal and Inverted ordering at one-loop level. We embed this
scenario in the spectrum-generator generator to perform
parameter scans. Focusing on the tiny seesaw scale, we show that current
limits provide significant constraints on the scalar sector,
and we evaluate the impact of future cLFV -decay searches for the cases
of discovery or non-discovery. The tiny seesaw scale makes the neutrino sector
and the cLFV processes in the GNM similar to the scotogenic and the
scoto-seesaw models, so we provide constraints for these models as well.Comment: updated to match the published version + misprint in eq.(5.1) fixe