Aims of the Workshop

Abstract

There are challenges and opportunities for the European particle physics community to engage with innovative and exciting developments which could lead to precision measurements in the neutrino sector. These have the potential to yield significant advances in the understanding of CP violation, the flavour riddle and theories beyond the Standard Model. This workshop aims to start the process of a dialogue in Europe so that informed decisions on the appropriate directions to pursue can be made in a few years time. 1 The Importance of Neutrino Physics Neutrinos have already contributed much to our understanding of the quantum world yet our evolving knowledge of their parameters and their importance is still in its infancy. Their ability to surprise has been one of the highlights of the development of particle physics ever since Pauli postulated their existence in 1930 Repeatedly ideas and theories concerning their nature and role have had to be modified or even abandoned as experimental measurements have had unexpected consequences. The enigmatic nature of the neutrino and its place in the theory of matter remains and unforeseen developments in the neutrino area are likely to continue to excite as experimental data become more precise. We are now fully aware that neutrinos are not correctly described in the basic Standard Model but what is not known is whether this can be accommodated by a small tweaking of that model or it is the first sign of the long awaited direction particle physics must take to go beyond the Standard Model. Even the nature of the neutrino is unknown; unless lepton number has some deeper significance than has so far been appreciated it could well be that neutrinos are not Dirac but Majorana states and the possible consequences of this are quite mind-blowing. Neutrino properties are intimately connected with the unexplained role of flavour in particle physics, which, despite many years of exacting work in the quark sector, remains a mystery. Neutrino oscillations, manifestly beyond the Standard model, are intimately connected with flavour transitions and it is diffciult to believe that the flavour problem will be solved without an equally exhaustive study of flavour transitions in the lepton sector. Closely connected with this and arguably of even greater importance than the flavour riddle is that of CP violation. It is a crucial ingredient of any explanation of the baryon asymmetry but has so far only been observed in flavour transitions in the quark sector. Discovering additional sources of CP violation in the lepton sector would be a major advance. Finally, it would seem obvious that the ultimate theory of particle physics must intimately connect lepton and quark sectors. Many models encompassing such a connection are now emerging but only precise experimental data can provide the necessary discrimination for a major breakthrough.