Search results for "Standard Model"
showing 10 items of 1206 documents
Low-scale seesaw models versusNeff
2014
We consider the contribution of the extra sterile states in generic low-scale seesaw models to extra radiation, parametrized by ${N}_{\text{eff}}$. We find that the value of ${N}_{\text{eff}}$ is roughly independent of the seesaw scale within a wide range. We explore the full parameter space in the case of two extra sterile states and find that these models are strongly constrained by cosmological data for any value of the seesaw scale below $\mathcal{O}(100\text{ }\text{ }\mathrm{MeV})$.
The Minimal 3 + 2 Neutrino Model vs. Higgs Decays
2016
Abstract The minimal 3+2 neutrino model is a Type-I seesaw model with two Weyl fermions, singlets under the Standard Model. Apart from light neutrino masses and mixings, this model can be fully described by four additional parameters. In this work, we study the minimal 3+2 neutrino model in scenarios where the singlets have masses at the GeV scale. This can lead to Higgs decays into heavy neutrinos, which could be observable as displaced vertices at the LHC.
Neutrino Physics at the Turn of the Millenium
1999
Recent solar & atmospheric nu-data strongly indicate need for physics beyond the Standard Model. I review the ways of reconciling them in terms of 3-nu oscillations. Though not implied by data, bi-maximal nu-mixing models emerge as a possibility. SUSY with broken R-parity provides an attractive way to incorporate it, opening the possibility of testing nu-anomalies at high- energy colliders such as the LHC or at the upcoming long-baseline or nu- factory experiments. Reconciling, in addition, the LSND hint requires a fourth, light sterile neutrino, nus. The simplest are the most symmetric scenarios, in which 2 of the 4 neutrinos are maximally-mixed and lie at the LSND scale, while the oth…
ELECTROWEAK THEORY AND THE NEUTRINO-MASS AND NEUTRINO-OSCILLATION QUESTIONS
2007
It is shown that both conjectures of neutrino mass and neutrino oscillation can be made really well-grounded within the Standard Model provided that one adopts a recent new version of the electroweak scheme spontaneously giving also a fundamental explanation for the so-called "maximal parity-violation" effect. A crucial role is played by the prediction of two distinct, scalar and pseudoscalar, replicas of (electron, muon, and tau) lepton numbers that could fully account for an actual non-coincidence between neutrino mass-eigenstates and gauge-eigenstates.
Neutrino masses and mixing in A(4) models with three Higgs doublets
2013
We study neutrino masses and mixing in the context of flavor models with A(4) symmetry, three scalar doublets in the triplet representation, and three lepton families. We show that there is no representation assignment that yields a dimension-5 mass operator consistent with experiment. We then consider a type-I seesaw with three heavy right-handed neutrinos, explaining in detail why it fails, and allowing us to show that agreement with the present neutrino oscillation data can be recovered with the inclusion of dimension-3 heavy neutrino mass terms that break softly the A(4) symmetry.
Leptogenesis with conservation of B–L
2012
Abstract We study leptogenesis in the decay of heavy Standard Model singlet fermions which carry lepton number, in a framework without Majorana masses above the electroweak scale. Based on M. C. Gonzalez-Garcia, J. Racker, N. Rius, JHEP 11 (2009) 079.
The Seesaw Scale vs Cosmology
2015
We will study the simplest extension of the Standard Model that can account for neutrino masses: the Type-I seesaw. The model introduces a New Physics scale, M, which is often assumed to be much larger than the electroweak scale. However, it is presently unconstrained and the light neutrino masses and mixing can be generated for any value of M above O(eV). Paying special attention to the contribution of the sterile states to Neff as a function of M, we will show that a large part of the M parameter space (8 orders of magnitude) can be excluded thanks to cosmological measurements. The implications for neutrinoless double beta decay will be discussed too.
Neutrino masses, leptogenesis, and dark matter in a hybrid seesaw model
2009
4 pages.-- ISI article identifier:000263816600020.-- ArXiv pre-print avaible at:http://arxiv.org/abs/0811.0953
Physics at new accelerators: Looking beyond the Standard Model
1993
Abstract Neutrino masses can have important implications in nuclear and particle physics, astrophysics and cosmology. Apart from the effects related to solar neutrinos, neutrino oscillations, dark matter, beta and double beta decays, massive neutrinos can also produce signals in the new accelerators. Here I focus on μ and τ number violating processes, very promising for muon and tau factories, as well as on the signatures associated with spontaneously broken R parity supersymmetry and neutral heavy leptons. These include the possibility of high rates for single chargino and neutralino production at LEP, LHC/SSC, as well as new signatures involving invisibly decaying Higgs bosons.
On the description of non-unitary neutrino mixing
2015
28 pages.- 8 figures.- typos corrected.- modified bounds on non-unitarity parameters.- new figs 3 and 4