Re: Neutrino Masses

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#37

From: Matt Carey
Date: Tue, 17 Jul 2001 01:12

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Uncle Al wrote:

> 
> More interesting is the purported mass of the heaviest neutrino:
> 0.05 eV.  An electron comes in at 511 KeV, and it is charged.
> What does 0.05 eV mean!  Every neutrino would be relativistic
> (kinetic energy exceeds rest mass) near room temp, and almost all
> of them ultra-relativistic in the extreme.  If you can't catch up
> to and pass by a free particle with spin you cannot invert its
> handedness - neutrinos stay absolutely left-handed.

I guess I have a hard time understanding the logic here.

1) the low mass is sort of the point, isn't it?  If it has
a larger mass there wouldn't be a question, would there?

2) What is the "Room Temperature" of the universe?  The bright
boys at Bell Labs measured the background radiation of the universe
at about 3K (2.77K?) as I recall.  About 0.01 what we consider
room temperature.  kbT is about 1/40 eV at RT, so the background
"temperature" of the universe would be about 1/4000 eV.  Hardly
enough to make a neutrino relativistic.

3) the whole arguement in 2) is useless anyway.  A rule of
thumb is that a particle needs about 10 collisions to become thermalized
(assuming the mass differences aren't huge, as they are here). But,
what is it a neutrino would bounce off of to become thermalized?

Matt

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From: Matt Carey <matt.carey@ieee.org>
Newsgroups: sci.physics.cond-matter,sci.materials,sci.mech.fluids,fj.sci.matter
Subject: Re: Neutrino Masses
Date: Mon, 16 Jul 2001 18:12:04 -0700
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