neutrino LET

[benesch@cebaf.gov (Jay Benesch)]

This note may be of interest to this list; not the sort of LET most 
readers have to deal with.  

Jay Benesch
benesch@cebaf.gov

-------------------------------

PHYSICS NEWS UPDATE                         
The American Institute of Physics Bulletin of Physics News
Number 253  January 11, 1996  by Phillip F. Schewe and Ben
Stein

DID NEUTRINOS KILL THE DINOSAURS?  Massive collapsing
stars radiate most of their binding energy  (about 10**53 ergs) in
the form of neutrinos.  The rate of such collapses in our galaxy is
expected to be greater, perhaps by a large factor, than the
supernova rate.  John Bahcall estimates a rate of about one collapse
every 11 years in our galaxy.  Stellar collapses  might not exhibit
the conspicuous optical show of full-blown supernovas but can still
be potent emitters of neutrinos.  According to Juan Collar, recently
of the University of South Carolina but now with the University of
Paris (collar@gps.jussieu.fr), stellar-collapse neutrinos may have
played a role in biological extinctions on Earth in past eras,
notwithstanding their very weak interactions with ordinary matter. 
Although stellar collapse parameters are  poorly known, Collar has
ventured to calculate the effect of a hypothetical  low-dose, high-
linear-energy-transfer (the energy dissipated by a radiation per unit
length through a biological sample) neutrino flux on terrestrial
animals; he suggests that collapse neutrinos may well cause a
catastrophic level of cancerous malignancy, with ensuing large-
scale loss of life, at a frequency (on the order of 100 million years)
consistent with known major extinctions on Earth.  (Juan I. Collar,
Physical Review Letters, 15 January 1995;  science journalists can
obtain the article from AIP Public Information,
physnews@aip.org.)