Novel Topics in π Nuclear Physics

Abstract

What is the role of π-nuclear physics? What can we learn from it? Let me first clearly state what it should not be. It is a temptation for some to use physical pions as a spectroscopic tool to investigate nuclear states, which is little more than an extension of Van de Graaff physics to a new particle and to less preciseness. With a few exceptions (mainly photopions and radiative π-capture) this is not a great challenge to our imagination and it is not the true reason for the importance of pions to nuclear physics. The key importance of pions is that it is the most important constituent in the nuclear force; in this way it indirectly influences every single aspect of nuclear physics. Because of this the nature of its interaction becomes of prime importance and so does its connection to nuclear properties. This is in particular so since the pion field may radically change under the right conditions leading for example to a nuclear phase transition. It is therefore these unfamiliar, novel features of the nucleus, its relativistic phenomena, the modification of the nuclear force by the nuclear medium (3 body forces), isobar effects and exchange currents which are the main motivations for π-nuclear physics: the use of physical pions serve to illustrate the effects and elucidate the many possibilities.