Stars as Laboratories for Fundamental Physics - MPP Theory Group

Supernova Neutrinos 419
to multiple scattering varies from about 34 ◦ at E e = 5 MeV to 22 ◦ at
20 MeV (Hirata 1991).
The direction of motion of the charged lepton relative to the incident
neutrino is well preserved in νe collisions (Sect. 10.3.4) so that the
main limitation to a reconstruction of the primary neutrino direction is
multiple Coulomb scattering. For the ν e p reaction, the angular distribution
is isotropic, apart from a small (about 10%) backward asymmetry
(e.g. Boehm and Vogel 1987). The ν 16 e O reaction yields a distribution
approximately proportional to 1 − 1 cos Θ, i.e. it is also nearly isotropic
3
with a backward bias (Haxton 1987). As a SN is expected to produce all
(anti)neutrino flavors in about equal numbers, the signal is dominated
by the isotropic ν e p reaction.
Table 11.1. Neutrino burst at the Kamiokande detector (Hirata et al. 1988).
The time is relative to the first event at 7:35:35 ± 0:01:00 UT, 23 Feb. 1987.
The energy refers to the detected e ± , not to the primary neutrino.
Event Time Angle Energy
[s] [degree] [MeV]
1 0.000 18 ± 18 20.0 ± 2.9
2 0.107 40 ± 27 13.5 ± 3.2
3 0.303 108 ± 32 7.5 ± 2.0
4 0.324 70 ± 30 9.2 ± 2.7
5 0.507 135 ± 23 12.8 ± 2.9
6 a 0.686 68 ± 77 6.3 ± 1.7
7 1.541 32 ± 16 35.4 ± 8.0
8 1.728 30 ± 18 21.0 ± 4.2
9 1.915 38 ± 22 19.8 ± 3.2
10 9.219 122 ± 30 8.6 ± 2.7
11 10.433 49 ± 26 13.0 ± 2.6
12 12.439 91 ± 39 8.9 ± 1.9
13 a,b 17.641 . . . 6.5 ± 1.6
14 a,b 20.257 . . . 5.4 ± 1.4
15 a,b 21.355 . . . 4.6 ± 1.3
16 a,b 23.814 . . . 6.5 ± 1.6
a Usually attributed to background.
b Quoted after Loredo and Lamb (1995).