Stars as Laboratories for Fundamental Physics - MPP Theory Group

What Have We Learned from SN 1987A 499
13.3.3 Intrinsic Dispersion of the ν e -Pulse
a) Neutrino Mass
So far the transit time of different particle species was compared under
the assumption of a fixed velocity each. However, the most likely
effect of signal propagation over large distances is dispersion due to an
energy-dependent speed of propagation. The most widely discussed 84
case is that of a nonzero neutrino mass (Zatsepin 1968). The main
problem at extracting information about the signal dispersion is the
unknown behavior of the source which must be modelled according
to some theoretical assumptions. A particularly detailed discussion is
that of Loredo and Lamb (1989) who found a mass limit of m νe < 23 eV
(Sect. 11.3.4). In a similar analysis which included the 13% dead-time
effect at IMB, Kernan and Krauss (1995) found m νe < 20 eV.
b) Neutrino Charge
The absence of an energy-dependent dispersion of the neutrino pulse
can be used to constrain other neutrino properties. A small electric
charge e ν would bend the neutrino path in the galactic magnetic field,
leading to a time delay of
∆t
t
= e2 ν (B T d B ) 2
, (13.6)
6Eν
2
where B T is the transverse magnetic field and d B the path length within
the field. This leads to a constraint of
( ) ( )
e ν
1 µG 1 kpc
e ∼< 3×10 −17 B T d B
(13.7)
(Barbiellini and Cocconi 1987; Bahcall 1989). Note that a typical field
strength for the ordered magnetic field in the galactic spiral arms is
2−3 µG and that the path length of the neutrinos within the galactic
disk is only of order 1 kpc because the LMC lies high above the disk
(galactic latitude about 33 ◦ ).
84 Limits on m νe from the SN 1987A data were derived, among others, by Abbott,
de Rújula, and Walker (1988), Adams (1988), Arnett and Rosner (1987), Bahcall
and Glashow (1987), Burrows and Lattimer (1987), Burrows (1988a), Chiu,
Chan, and Kondo (1988), Cowsik (1988), Kolb, Stebbins, and Turner (1987a,b),
Midorikawa, Terazawa, and Akama (1987), Sato and Suzuki (1987a,b), Spergel and
Bahcall (1988), Loredo and Lamb (1989), and Kernan and Krauss (1995).