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Neutrinos

 

HINTS OF 'BSM' PHYSICS FROM NEUTRINOS


The definitive discovery of a non-zero neutrino mass represents a strong experimental hint for physics beyond the Standard Model (BSM). Neutrino, with its unknown mass and its uncertain Dirac or Majorana nature, is waiting to be placed into a new model capable to describe it in the correct way. A strong interplay between particle physics, cosmology and astroparticle physics is needed to take steps forward into this field, as well as theoretical and experimental efforts have to be tightly connected to look for new physics signatures.

 

MODEL BUILDING

The Standard Model of Particle Physics is a very successful theory but it lacks an explanation for neutrino masses, dark matter and the baryon asymmetry of the Universe. Several members of SOM work on proposing and studying scenarios of physics beyond the standard model for these unsolved issues, and to study their phenomenological implications, which can be tested against experimental results. In particular, we are experts on models of neutrino mass generation, such as low-scale seesaws and radiative models. In some of these scenarios, also dark matter and/or the baryon asymmetry can be explained. The experimental results expected in the next years will be crucial in narrowing down the plethora of possibilities. In particular, in the neutrino sector, the mass ordering and CP violation will be measured. In the context of dark matter, if a signal of a weakly interacting massive particle (WIMP) is not observed in direct or indirect detection, the WIMP paradigm may lose part of its motivation. Other options, such as asymmetric dark matter, are also of interest to our group.

 

DIRAC VS MAJORANA NEUTRINOS (neutrinoless double beta decay)

Determining if massive neutrinos are Dirac or Majorana fermions is crucial to define the mechanism that gives them mass. The most promising way to investigate the nature of massive neutrinos is to search for the neutrinoless double beta decay, a forbidden Standard Model nuclear transition which explicitly violates the total lepton number. Nowadays, many experiments are waiting to discover something more about this process, exploiting different techniques (NEXT, CUORE..).

 

SUPERNOVAE NEUTRINOS (neutrino mass ordering and neutrino mass bounds)

Core-collapse Supernovae provide a precious signal from our Universe that can help us to constrain neutrino properties. Most of the energy released by the explosion is emitted through neutrinos and antineutrinos of all flavors, with mean energies of tens of MeV. Their detection, expliyting their different interaction channels with matter, offers a lot of interesting possibilities as, for example, determine the neutrino mass ordering (normal ordering or inverted one) and imposing new bounds on neutrino mass, together with the development of more detailed models on the Supernova explosion mechanisms.
A new generation of neutrino detectors is ready to observe the next Supernova explosion (IceCube), and a future generation of detectors is under design and construction (Hyper-Kamiokande, DUNE). Thanks to the enhanced flavor sensitivity and statistics, the next observed core-collapse burst will lead to an important step forward in understanding of core-collapse mechanisms and neutrino properties.

 

The DUNE experiment

The future long baseline facility DUNE (Deep Under-ground Neutrino Experiment) consists of a beam of muon neutrinos (or muon antineutrinos) that will travel from Fermilab to the far detector, located at the Sanford Underground Research Laboratory in Lead, South Dakota — 1,300 kilometers downstream of the source. This experiment aims to extract the sign of the atmospheric mass splitting and the CP violating phase in the neutrino mixing sector. However, great physics opportunities also arise for atmospheric neutrinos, supernovae neutrinos, and neutrinos from dark matter annihilating particles. Some members of the SOM group, even if theoretical physicists, are also part of the DUNE collaboration, see some related work in:


https://arxiv.org/abs/1905.03589

 

 

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