🚀 go-pugleaf

In article <1992Aug11.063110.4104@cco.caltech.edu>, brahm@cco.caltech.edu (David E. Brahm) writes...

>One interesting new result I heard was from Norman (of LBL) himself.  Their
>old experiment, beta decay of 14-C, saw a kink at 17 keV; I think I heard a
>statistical significance of 9 sigma.  Their new experiment, inner
>bremstrahlung from 55-Fe, sees no kink, contradicting the result of their
>first experiment by 7 sigma.  It was amusing hearing Norman describe both
>results in the same talk.  To my untrained eye the 55-Fe data (null result)
>looked a lot more convincing.

Yeah.  Me too.  But Eric Norman seems convinced that this is all OK.  I 
asked him about it and he gave me some reasons - poor statistics, blah blah, 
etc. why that result is not as firm as his positive findings.  He has new
experiments in progress.  Norman is a careful researcher, and I trust his
judgement about the weight to give his experiments - although I didn't study 
the results enough to judge for myself. 

In my mind, the most compelling evidence is that the same 17 KeV kink occurs
in so many different systems.  It's too hard to ignore.  

In the absense of any good resolution of the experimental confusion, there is 
one other source of potential clarification - neutrino oscillation experiments
which measure e-tau neutrino mixing directly in high-intensity neutino beams.
There are several experiments currently under way.

The e-mu mixing experiment is easy to do - just produce a beam of muon
neutrinos from a secondary pion beam which decays in-flight, and irradiate
a detector volume which can discriminate electrons and muons which might
be produced by neutrino-nucleon interactions.  If you see any electrons, 
then there was (a) mixing or (b) contamination of your beam.

But e-tau mixing is more difficult.  Taus decay quickly - so you have
to discriminate electrons from e-neutrino-nucleon interactions from 
electrons due to tau decays when a tau is produced as the result of mixing.
You can do the experiment - using phase space cuts, etc.  But it's tricky.
Actually, I'm not even sure if they do e-tau experiments directly or 
if they do mu-tau.  But the problems are the same due to the short tau
lifetime.

If a mixing experiment were to conclusively rule out the possibility
of a tau neutrino which couples at something near 1% to electrons, then 
I think that the 17 KeV neutrino advocates would be pressed hard up against
the wall.  

-Scott

--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver