PHY651P - Neutrino Physics (2023-2024)

Lecturers: Thomas MUELLER, Cristina VOLPE

The course will focus on forefront experimental and theoretical neutrino physics and astrophysics. The lectures will be articulated as follows.

We will start with a (relatively) short historical introduction leading up to the Standard Model of electroweak interactions and the discovery of neutrino oscillations. We will present theoretical aspects of neutrino oscillations in vacuum and in matter - the Mikheev-Smirnov-Wolfenstein effect and applications to the Sun, to the Earth and core-collapse supernovae. The most important results will be described concerning solar, atmospheric, reactor and accelerator neutrino oscillation experiments that lead us to the 3 flavour oscillation framework and the current measurement of most of the oscillation parameters. We will present the global analysis of all existing neutrino oscillation data, the presence of anomalies and discuss remaining key questions, including the neutrino (Majorana versus Dirac) nature and absolute mass, the neutrino mass ordering, the existence of CP violation and of sterile neutrinos.

Since neutrino oscillations require those particles to have a mass, we will describe how to extend the Standard Model to generate a mass to the neutrino. We will then discuss neutrinos as Dirac or Majorana particles. We will present our knowledge on the absolute scale of neutrino masses coming from the measurement of the end-point of the electron spectrum in nuclear beta-decays and neutrinoless 
double-beta-decay experiments.

Neutrinos can be produced in violent phenomena and dense environments, such as in core-collapse supernovae and in accretion disks around compact objects (neutron star mergers and black holes). The investigation of neutrino propagation in media has uncovered novel flavor conversion phenomena, due in particular to the neutrino self-interaction. In this context many open questions remain. We will describe the density matrix and effective spin formalisms employed to describe neutrino evolution. We will derive the evolution equations currently used, based on the mean-field approximation and make the connection to other many body systems such as condensed matter and atomic nuclei. We will discuss the link to the supernova dynamics, the relevance for heavy element nucleosynthesis and the recent kilonova observation. Finally we will discuss future observations of neutrinos from core-collapse supernovae and the possible discovery of the diffuse supernova neutrino background.

ECTS credits: 3