Low Temperature Detectors for Neutrino Physics

Low temperature detectors are a class of detectors that leverage material properties at low temperature (normal- and super-conductivity, magnetization, ...) to detect radiation and measure its energy.  

Low temperature detectors can be broadly divided in two categories:

• equilibrium detectors which wait for all the deposited energy to have thermalized and measure temperature variations, i.e. changes in the thermodinamic equilibrium phonon energy distribution
• non-equilibrium detectors which do not wait for energy thermalization and are sensitive for example to athermal phonons created in the absorber or to changes in the density of quasi-particles in superconductors

Recent years have witnessed many exciting breakthroughs in neutrino physics.

In the Standard Model of Elementary Particles the neutrino ν is assumed to be not the same particle as the anti-neutrino  ν, i.e it is a Dirac particle. In many extensions to the Standard Model aiming to the Grand Unification of particle interactions and in theories of particle mass generation, the neutrino and the anti-neutrino turn out to be the same particle, i.e. the neutrino is a Majorana particle. The only available experimental probe to asses the actual nature of the neutrino is the search for the neutrinoless double beta decay.

Assessing the absolute neutrino mass scale is one of the major challenges in today particle physics and astrophysics. This requires to measure the mass of one of the three neutrinos and the kinematical neutrino mass measurement is the only model independent method since it exploits only energy and momentum conservation. In particular, the electron anti-neutrino mass can be measured by precisely analyzing the kinematics of electrons emitted in beta decays. In practice this means measuring the minimum energy carried away by the anti-neutrino, i.e. its rest mass, by observing the highest energy electrons emitted in the decay.