# What is the neutrino field?

1. Jun 26, 2012

### nburns

What is the neutrino field? How much of what we know about neutrinos is adequately explained by theory?

Thanks.

Last edited: Jun 26, 2012
2. Jun 26, 2012

### phinds

https://www.physicsforums.com/blog.php?b=3588 [Broken]

Last edited by a moderator: May 6, 2017
3. Jun 26, 2012

### nburns

Sorry for the vague question. These fascinating particles don't seem to generate much literature. Is it because of a lack of experimental results?

It seems that these particles could be the key to a lot of new physics, if they were better understood.

4. Jun 26, 2012

### phinds

I think you significantly underestimate the extent to which they ARE understood.

5. Jun 26, 2012

### nburns

Is there reading material you could point me to, please?

6. Jun 26, 2012

### phinds

I don't have any specific references but I would think an internet search would turn up quite a lot. Perhaps one of the other members will have something specific.

There are several neutrino detectors around the world. There's one in Japan in particular, but I can't remember the name. I suggest Googling "neutrino detectors" to start with

7. Jun 26, 2012

Staff Emeritus
No, it's because it's not true.

There were 1433 papers with the word "neutrino" in the title in 2011.

8. Jun 26, 2012

### Staff: Mentor

Before the current crop of neutrino detectors, which are mainly focused on studying neutrino oscillations, both Fermilab and CERN used more traditional detectors (both electronic detectors and bubble chambers) to study neutrino beams produced from their fixed-target accelerators (e.g. Tevatron at Fermilab and SPS at CERN). These were active from the 1970s probably into the 1990s.

9. Jun 26, 2012

### nburns

I realized after I posted it that I was probably mistaken. I don't read the *real* literature, though, I only read what filters down to magazines like Scientific American -- which is the highlights.

As far as I know, the state of knowledge is still that neutrinos appear to have mass, but also appear to travel at the speed of light. And there is no way to reconcile these two things with existing theory.

10. Jun 26, 2012

### nburns

Moreover; apparently, by far, most of the energy of supernovae goes into neutrinos -- they are what blow the star apart. These strange particles seem to have a major role to play in nature. Even if the LHC doesn't find any new particles, it seems like particle physics still has a lot of work to do explaining the ones we already know about.

11. Jun 26, 2012

### Staff: Mentor

Their mass is so small that their speed is so close to the speed of light that the difference is undetectable.

12. Jun 27, 2012

### nburns

That explanation sounds a little bit too convenient. I believe that there has to be a more satisfying answer.

13. Jun 27, 2012

### nburns

By the way --

Thank you, jtbell, vanadium 50 and phinds for replying on my thread.

14. Jun 27, 2012

Staff Emeritus
That's false.

On PF we discourage the style of learning where one person makes a parade of false statements to be corrected by others. We find it ineffective and many people find it irritating. Asking questions by asking questions just works better than asking questions by making incorrect statements.

Given a particle's energy and mass, we can calculate its velocity - that's true whether the particle is a neutrino, a brick, or a planet. It just so happens that for neutrinos of detectable energy, this works out to very, very, very close to the speed of light. You may wish that the difference were bigger, of course, but it is what it is.

15. Jun 27, 2012

### Staff: Mentor

Look up the energies of the neutrinos used in these experiments, and the current estimates of their masses. Find the momentum from

$$E^2 = \sqrt {(pc)^2 + (mc^2)^2}$$

and the speed from

$$\frac{v}{c} = \frac{pc}{E}$$

The last time I tried it, I got a speed which was identical with c out to more than ten decimal places. (I can't seem to turn up that thread at the moment, though. It was sometime during the past year.)

16. Jun 27, 2012

### nburns

Forgive me if I gave the impression that I know something about physics. I am just an observer, not a participant. I don't even know why my statements were incorrect. I was trying to help the discussion along by stating my impression of the current state of knowledge, in the hope that someone would correct me wherever I was wrong.

I'm pretty sure that a real physicist must have had those ideas at some point, though. Because I must have gotten them from somewhere.

I'm not capable of doing the calculations. But that explanation doesn't ring true for me. I think that would be the first known case of a particle traveling at almost the speed of light because it almost doesn't have mass. All the other ones either do or don't.

As I said, I'm definitely not an expert, so I can't offer anything more than my non-expert intuition. But I get the sense that there's not nearly enough data to settle the matter once and for all, so even non-expert intuition has a chance.

Last edited: Jun 27, 2012
17. Jun 27, 2012

Staff Emeritus
For a 0.1 eV neutrino at 10 GeV, it's the same to twenty-two decimal places.

18. Jun 27, 2012

Staff Emeritus
The thing about science is that if you can't do the calculation, you don't get to have an opinion. This isn't "I like broccoli" where everyone's opinion is equal. In science, everyone's opinion is not equal - it has to be based on facts.

19. Jun 27, 2012

### nburns

Thanks. I'll have to see if I can make anything out of those equations with what knowledge I have.

The explanation doesn't feel very satisfying, though, does it?

20. Jun 27, 2012

### nburns

Agreed. But the calculations are based on assumptions, and those assumptions could prove false.

I'm going to stop pretending to be more of an expert than I am and leave it at that. I'll remain skeptical until the data are all in and then I'll accept the outcome, whatever that is. It doesn't look to me like it will be resolved for at least a few more years.