Stars as Laboratories for Fundamental Physics - MPP Theory Group

Supernova Neutrinos 445
presence of magnetic fields were discussed by a number of authors. 68
Because of the left-handedness of the weak interaction both neutrinos
and antineutrinos would be emitted preferentially in the same direction
singled out by the magnetic field. Its effects become substantial only for
field strengths near and above the critical strength m 2 e/e = 4.4×10 13 G.
In order to obtain neutron-star kick velocities of several 100 km s −1
it appears that magnetic fields several orders of magnitude larger are
required which, however, may possibly exist in some SN cores after
collapse. Also, the asymmetric emission of neutrinos may be aided by
the formation of a pion condensate and perhaps other processes (Parfenov
1988, 1989). Certain special field configurations seem to allow
for significantly anisotropic neutrino emission (Bisnovatyi-Kogan and
Janka 1995).
It remains to be seen if sufficiently anisotropic neutrino emission can
be established as a generic property of a protoneutron star’s Kelvin-
Helmholtz cooling phase. Meanwhile, the neutrino rocket engine remains
a fascinating speculation for accelerating neutron stars.
11.6 Future Supernovae
The neutrino observations from SN 1987A gave us a wealth of information
in the sense that they confirmed the broad picture of neutrino
cooling of the compact object formed after collapse. The data were
much too sparse, however, to distinguish between, say, different equations
of state or different assumptions concerning neutrino transport, or
to detect or significantly constrain neutrino masses and mixing parameters.
Some worry is caused by the apparent anomalies of the SN 1987A
data, notably the angular distribution of the secondary charged particles.
No doubt it would be extremely important to observe a SN
neutrino signal with greater statistical significance, or from a greater
distance. What is the prospect for such an observation
SN neutrinos can be observed in a number of underground detectors
which are operational now or in the near future, or which have only
been proposed. An extensive overview was given by Burrows, Klein,
and Gandhi (1992). Of the experiments which will become operational
within the foreseeable future, the upcoming Superkamiokande water
Cherenkov detector (Sect. 10.9) would yield by far the largest num-
68 O’Connell and Matese (1969a,b); Matese and O’Connell (1969); Ivanov
and Shul’man (1980, 1981); Dorofeev, Rodionov, and Ternov (1984); Loskutov
(1984a,b); Cheng, Schramm, and Truran (1993).