Stars as Laboratories for Fundamental Physics - MPP Theory Group

Preface
xvii
search for proton decay, or the search for particle dark matter in the
galaxy by direct and indirect detection experiments (Rich, Lloyd Owen,
and Spiro 1987). It is fascinating that the IMB and Kamiokande water
Cherenkov detectors which had been built to search for proton decay
ended up seeing supernova (SN) neutrinos instead. The Fréjus detector,
instead of seeing proton decay, has set important limits on the
oscillation of atmospheric neutrinos. Kamiokande has turned into a
major solar neutrino observatory and dark-matter search experiment.
The forthcoming Superkamiokande and SNO detectors will continue
and expand these missions, may detect a future galactic SN, and may
still find proton decay.
⋄
All currently known phenomena of elementary particle physics are
either perfectly well accounted for by its standard model, or are not
explained at all. The former category relates to the electroweak and
strong gauge interactions which have been spectacularly successful at
describing microscopic processes up to the energies currently available
at accelerators. On the other side are, for example, the mass spectrum
of the fundamental fermions (quarks and leptons), the source for CP
violation, or the relationship between the three families (why three).
There must be “physics beyond the standard model!”
In the standard model, neutrinos have been assigned the most minimal
properties compatible with experimental data: zero mass, zero
charge, zero dipole moments, zero decay rate, zero almost everything.
Any deviation from this simple picture is a sensitive probe for physics
beyond the standard model—thus the enthusiasm to search for neutrino
masses and mixings, notably in oscillation experiments, but also
for neutrino electromagnetic properties, decays, and other effects. In
astrophysics, even “minimal neutrinos” play a major role for the energy
loss of stars as they can escape unscathed from the interior once
produced. Moreover, in spite of their weak interaction there are two
astrophysical sites where they actually reach thermal equilibrium: the
early universe up to about the nucleosynthesis epoch and in a SN core
for a few seconds after collapse. Neutrinos thus play a dominant role
in the cosmic and SN dynamical and thermal evolution—little wonder
that these environments are important neutrino laboratories.
Nonstandard neutrino properties such as small Majorana masses
or magnetic dipole moments would be low-energy manifestations of
novel physics at short distances. Another spectacular interloper of highenergy
physics in the low-energy world would be a Nambu-Goldstone