Role of Neutrinos: What Are They and What Do They Do?

[RobinSky]

Hi

I'm just curious, what role does neutrinos play in the universe? I mean protons an electrons and neutrons make up the atom, quarks make up protons and such.

But neutrinos? Barely heard anything except that they are barely interacting with anything, and that they are a "waste product" from nuclear processes?

Best Regards
Robin A

 

[twofish-quant]

I'm just curious, what role does neutrinos play in the universe? I mean protons an electrons and neutrons make up the atom, quarks make up protons and such.

Among other things, neutrinos make supernova go boom. When supernova collapse, it releases a huge amount of neutrinos and somehow enough of them get trapped to create an explosion.

 

[ImaLooser]

Among other things, neutrinos make supernova go boom. When supernova collapse, it releases a huge amount of neutrinos and somehow enough of them get trapped to create an explosion.

At least, so is believed. No one has yet to succeed in getting the math to work.

Neutrinos are emitted with liquids form Cooper pairs and go superfluid, I think. But I'm sure that it always happens that way.

They seem to have almost no mass at all. Somehow it was calculated that even though there are a great many of them, their mass is insignificant.

 

[Chronos]

Neutrinos are so weakly interactive with almost everything, it was long thought they were massless. Only recently has opinion changed on that count. A neutrino has about a 50% chance of penetrating a lead shield extending from here to alpha centauri. This gives us a basis for comparison with whatever constitutes a dark matter particle.

 

[twofish-quant]

At least, so is believed. No one has yet to succeed in getting the math to work.

I know, I tried :-) :-)

We know supernova emit large amounts of neutrinos because we saw them in 1987. To give you an idea of how murky they are, the 1987 event involved the detection of about a dozen neutrinos within a few seconds.

They seem to have almost no mass at all. Somehow it was calculated that even though there are a great many of them, their mass is insignificant.

It depends on the what their mass was. One calculation that I've seen for the upper limit of the neutrino mass you take the amount of matter necessary to close the universe divide it by the number of expected neutrinos, and this gives you a lower limit.

We have very strong reasons to think that the mass of the neutrino is not zero.

 

[RobinSky]

We know supernova emit large amounts of neutrinos because we saw them in 1987. To give you an idea of how murky they are, the 1987 event involved the detection of about a dozen neutrinos within a few seconds.

Wow that's cool! Didn't know about the relation between supernovae and neutrinos at all actually.

 

[twofish-quant]

Wow that's cool! Didn't know about the relation between supernovae and neutrinos at all actually.

Yup. One "oops" moment. There were two detectors on planet Earth at the time. One in Japan and one under Lake Erie. If we had precision times as to when the neutrinos hit the detectors, then we'd be able to tell if they were traveling at the speed of light or at slightly less than the speed of light and then figure all sorts of things about the neutrinos.

One of the experiments had a timestamps generated by an ultraprecise atomic clock so we know exactly when the neutrino pulse hit that detector. The other one had a clock in which someone just typed in a time when the PC got booted. Unfortunately someone turned off the PC before they could sync the timestamps. Ironically, it was the detector in Japan that had the inaccurate clock.

 

[mfb]

Looking at the http://prl.aps.org/abstract/PRL/v58/i14/p1490_1 :

A neutrino burst was observed in the Kamiokande II detector on 23 February, 7:35:35 UT (±1 min) during a time interval of 13 sec

and the http://prl.aps.org/abstract/PRL/v58/i14/p1494_1 :

The events span an interval of six seconds and have visible energies in the range 20–40 MeV.

How do you compare neutrino timings with sub-second precision if the neutrino burst lasts ~10 seconds with about 1 detected event per second?