showing 14 related works from this author
Summary Report of MINSIS Workshop in Madrid
2010
Recent developments on tau detection technologies and the construction of high intensity neutrino beams open the possibility of a high precision search for non-standard {\mu} - {\tau} flavour transition with neutrinos at short distances. The MINSIS - Main Injector Non-Standard Interaction Search- is a proposal under discussion to realize such precision measurement. This document contains the proceedings of the workshop which took place on 10-11 December 2009 in Madrid to discuss both the physics reach as well as the experimental requirements for this proposal.
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 $\mathcal{O}(100\text{ }\text{ }\mathrm{MeV})$.
Physics at a future Neutrino Factory and super-beam facility
2009
The conclusions of the Physics Working Group of the international scoping study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Superbeams, Laboratori Nazionali di Frascati, Rome, June 21-26, 2005) and NuFact06 (Ivine, California, 24{30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second generation super-beam experiments, …
Global bounds on the Type-III Seesaw
2020
We derive general bounds on the Type-III Seesaw parameters from a global fit to flavor and electroweak precision data. We explore and compare three Type-III Seesaw realizations: a general scenario, where an arbitrary number of heavy triplets is integrated out without any further assumption, and the more constrained cases in which only 3 or 2 (minimal scenario) additional heavy states are included. The latter assumption implies rather non-trivial correlations in the Yukawa flavor structure of the model so as to reproduce the neutrino masses and mixings as measured in neutrino oscillations experiments and thus qualitative differences can be found with the more general scenario. In particular,…
Minimal models with light sterile neutrinos
2011
We study the constraints imposed by neutrino oscillation experiments on the minimal extensions of the Standard Model (SM) with $n_R$ gauge singlet fermions ("right-handed neutrinos"), that can account for neutrino masses. We consider the most general coupling to SM fields of the new fields, in particular those that break lepton number and we do not assume any a priori hierarchy in the mass parameters. We proceed to analyze these models starting from the lowest level of complexity, defined by the number of extra fermionic degrees of freedom. The simplest choice that has enough free parameters in principle (i.e. two mass differences and two angles) to explain the confirmed solar and atmospher…
Testable baryogenesis in seesaw models
2016
We revisit the production of baryon asymmetries in the minimal type I seesaw model with heavy Majorana singlets in the GeV range. In particular we include "washout" effects from scattering processes with gauge bosons, Higgs decays and inverse decays, besides the dominant top scatterings. We show that in the minimal model with two singlets, and for an inverted light neutrino ordering, future measurements from SHiP and neutrinoless double beta decay could in principle provide sufficient information to predict the matter-antimatter asymmetry in the universe. We also show that SHiP measurements could provide very valuable information on the PMNS CP phases.
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.
The seesaw path to leptonic CP violation
2016
Future experiments such as SHiP and high-intensity $e^+ e^-$ colliders will have a superb sensitivity to heavy Majorana neutrinos with masses below $M_Z$. We show that the measurement of the mixing to electrons and muons of one such state could imply the discovery of leptonic CP violation in the context of seesaw models. We quantify in the minimal model the CP discovery potential of these future experiments, and demonstrate that a 5$\sigma$ CL discovery of leptonic CP violation would be possible in a very significant fraction of parameter space.
The seesaw portal in testable models of neutrino masses
2017
A Standard Model extension with two Majorana neutrinos can explain the measured neutrino masses and mixings, and also account for the matter-antimatter asymmetry in a region of parameter space that could be testable in future experiments. The testability of the model relies to some extent on its minimality. In this paper we address the possibility that the model might be extended by extra generic new physics which we parametrize in terms of a low-energy effective theory. We consider the effects of the operators of the lowest dimensionality, $d=5$, and evaluate the upper bounds on the coefficients so that the predictions of the minimal model are robust. One of the operators gives a new produ…
The minimal 3+2 neutrino model versus oscillation anomalies
2012
We study the constraints imposed by neutrino oscillation experiments on the minimal extension of the Standard Model that can explain neutrino masses, which requires the addition of just two singlet Weyl fermions. The most general renormalizable couplings of this model imply generically four massive neutrino mass eigenstates while one remains massless: it is therefore a minimal 3+2 model. The possibility to account for the confirmed solar, atmospheric and long-baseline oscillations, together with the LSND/MiniBooNE and reactor anomalies is addressed. We find that the minimal model can fit oscillation data including the anomalies better than the standard $3\nu$ model and similarly to the 3+2 …
Leptogenesis in GeV scale seesaw models
2015
We revisit the production of leptonic asymmetries in minimal extensions of the Standard Model that can explain neutrino masses, involving extra singlets with Majorana masses in the GeV scale. We study the quantum kinetic equations both analytically, via a perturbative expansion up to third order in the mixing angles, and numerically. The analytical solution allows us to identify the relevant CP invariants, and simplifies the exploration of the parameter space. We find that sizeable lepton asymmetries are compatible with non-degenerate neutrino masses and measurable active-sterile mixings.
N_eff in low-scale seesaw models versus the lightest neutrino mass
2014
We evaluate the contribution to $N_{\rm eff}$ of the extra sterile states in low-scale Type I seesaw models (with three extra sterile states). We explore the full parameter space and find that at least two of the heavy states always reach thermalisation in the Early Universe, while the third one might not thermalise provided the lightest neutrino mass is below ${\mathcal O}(10^{-3}$eV). Constraints from cosmology therefore severely restrict the spectra of heavy states in the range 1eV- 100 MeV. The implications for neutrinoless double beta decay are also discussed.
Relaxing cosmological neutrino mass bounds with unstable neutrinos
2020
At present, cosmological observations set the most stringent bound on the neutrino mass scale. Within the standard cosmological model ($\Lambda$CDM), the Planck collaboration reports $\sum m_\nu < 0.12\,\text{eV}$ at 95% CL. This bound, taken at face value, excludes many neutrino mass models. However, unstable neutrinos, with lifetimes shorter than the age of the universe $\tau_\nu \lesssim t_U$, represent a particle physics avenue to relax this constraint. Motivated by this fact, we present a taxonomy of neutrino decay modes, categorizing them in terms of particle content and final decay products. Taking into account the relevant phenomenological bounds, our analysis shows that 2-body deca…
Looking at the axionic dark sector with ANITA
2020
The ANITA experiment has recently observed two anomalous events emerging from well below the horizon. Even though they are consistent with tau cascades, a high energy Standard Model or Beyond the Standard Model explanation is challenging and in tension with other experiments. We study under which conditions the reflection of generic radio pulses can reproduce these signals. We propose that these pulses can be resonantly produced in the ionosphere via axion-photon conversion. This naturally explains the direction and polarization of the events and avoids other experimental bounds.