Particle Physics Without Accelerators (selected topics)

Abstract

Particle physics without accelerators covers a wide variety of subjects. Only the following three main topics are discussed in this report :

• 1) High energy cosmic ray experiments, with a particular emphasis on the observations related to Cygnus X3 and their implications.

• 2) Neutrino physics : Majorana or Dirac neutrinos, neutrino masses, neutrino oscillations.

• 3) Constancy of the coupling constants over a long period of time based on the discovery of a fossil nuclear reactor in Gabon.

It is relatively easy to define what is the study of elementary particles with accelerators. An accelerator is any device which by means of intense electric fields, accelerates charged particle beams. The process starts from a hydrogen, deuterium, or helium bottle (or heavier element). Atoms are stripped by means of an electric field, and then acceleration of either the electrons or the stripped atoms can take place. A typical experiment will be the study of the collisions between beam particles and a specific target. It is much more complicated to tell what is exactly the study of elementary particles without accelerator : all what we know about the experiments is that they do not use accelerators, but obviously this is not enough since it has to deal with elementary particle physics. So the discovery of new particles without accelerators, mass measurements, branching ratios like double beta decay belong to this field. Nobody will object to include also the study of the properties of the interactions between elementary particles : quantum number conservation, hints to ultra high energy phenomena which cannot, at least presently, be reached by accelerators.

Particle Physics without accelerators aims for fundamental discoveries. Obviously, except for cosmic ray experiments, this is a very low Q2 physics. Nevertheless this is partly compensated by the fact that one can search for very rare processes by looking during a very long period of time at many elementary particles. In that sense this is a nice complementary way to study elementary particle physics compared to accelerator techniques.

A tentative list of the various topics is given below :

• 1. Hints for very high energy interactions from cosmic ray experiments

  Search for ultrahigh energy pointlike source of cosmic rays : the possible new physics involved by the recent discoveries concerning Cygnus X3.

• 2. Search for new particles : axions, monopoles and quarks.

• 3. Neutrino physics and weak interactions

• 4. Experiments related to Grand Unified Theories :

  baryon number conservation (proton lifetime.

  neutron antineutron oscillations)

  electric dipole moment of the neutron (involves CP conservation).

• 5. Constancy of the coupling constants over a long period of time (fossil reactor).

It can be argued whether or not we should include quantum mechanic tests (Bell inequalities and Aspect experiments), or general relativity tests (search for gravitational waves for instance ...) and quantum electrodynamics related experiments (g-2 for the electron).

In the two lectures given at Cargese 85, I had to choose between all these topics. Only points 1, 3 and 5 were covered and will be presented here. A more detailed report which will discuss all the above subjects will be published in Physics Reports together with M. Cribier and J. Rich [1].

This following report is not intended to be complete. Specially, recent experimental results might be missed. The main goals are ly to introduce the subjects and the motivations, to describe in a itical way the present status, and to foresee the main perspectives.