# I Neutrino detection?

1. Sep 11, 2016

### bbbl67

Now my understanding of neutrino detectors is that there are two common fluids used in the detectors, either Tetrachloroethylene (C2Cl4) aka "dry-cleaning fluid", and heavy water (D20). Why were these substances chosen specifically? Is there something about the elements within these substances that make them easier to study vs. any other element on the periodic table?

Also within these two substances, only one of the elements in each is singled out for study. In the case of C2Cl4, it is the Chlorine that is studied, and not the Carbon. In the heavy water, it is the Deuterium that is studied and not the Oxygen. Why is that? Isn't a neutrino just as likely to hit the Carbon or the Oxygen atoms, in each case?

Now, a related question. Is the Sudbury Neutrino Observatory (SNO) the only one in the world that can detect all neutrino events, and not just electron-neutrino events, or are there others now? SNO uses heavy water, is heavy water better for all-neutrino detection vs. C2Cl4? According to the following article, under the section about Cerenkov radiation:

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel.html

According to the above, a muon-neutrino strike maintains a very well-defined light-cone, whereas an electron-neutrino strike results in an electron shower which produces a very diffuse light-cone. Why should there be an electron shower from a single electron-neutrino hit, while a muon-neutrino hit doesn't result in a muon shower? Aren't each neutrino strike just producing one electron or one muon, respectively? Why should there even be a shower of electrons, when only one new electron is produced?

2. Sep 11, 2016

### Orodruin

Staff Emeritus
No, these are only two choices that have been used historically. Other choices include regular water (eg, Super-K), liquid scintillator (eg, LSND, NOvA), iron (eg, INO), and emulsions (eg, OPERA).

This is a matter of how the detection process works and how the physics allows the neutrinos in study to react with the different elements.

In the chlorine case, the search was for solar neutrinos and the interactions with chlorine left a particular residual atom that could be searched for. In the case of the deuterium in the SNO detector, it was because it allowed for the study of a particular interaction that has the same strength regardless of the neutrino flavour.

SNO is decommissioned and therefore no longer operational. Any other water Cherenkov detector will also be sensitive to other neutrino flavours, but not as strongly as to electron neutrinos (the cross section is about 1/6th for other flavours). For the neutral current process in SNO, all flavours interact with equal strength. Furthermore, for the charged current process in SNO, only electron neutrinos were relevant. The chlorine experiments were based on inverse beta decay and therefore only sensitive to electron neutrinos.

Yes, the neutrino strikes a single electron. The shower is a result from the subsequent electron interactions.

3. Sep 11, 2016

### Staff: Mentor

As well as liquid hydrogen, and a liquid hydrogen/neon mixture (in the 15-foot bubble chamber at Fermilab); and halon (CF3Br, in the Gargamelle bubble chamber at CERN).

Last edited: Sep 11, 2016
4. Sep 11, 2016

### bbbl67

What is liquid scintillator exactly?

In the case of iron, is that just solid iron, or is it molten?

Understood, but why exactly were certain elements within the molecules excluded? In the case of dry-cleaning fluid, it was the carbons that were ignored. In the case of water, it was the oxygens that were ignored.

Okay, so I can understand a hgh-speed electron smashing through a cloud of other electrons and causiong havoc That's because electrons all have the same charge, and other electrons want to get away from it. However, muons also have the same charge as electrons. Why wouldn't a high-speed muon also crash through a cloud of elecctrons and create a shower of electrons too?

5. Sep 11, 2016

### Orodruin

Staff Emeritus
https://en.wikipedia.org/wiki/Scintillator

Why on Earth would you use molten iron?

I already told you this. They do not participate in reactions that are detectable.

The charge is not the important parameter. The mass plays a huge role and the muon is 200 times more massive. You should be able to find this described in any basic text on how particles interact with a medium.

6. Sep 12, 2016

### ChrisVer

Not only (I guess you are refering to electron scattering off other electrons)....
there is Brehmstrahlung radiation (gammas) from the electron which produces e+e- pairs...then they also interact with other electrons and can give further photons and electron/positron pairs. The whole thing ends up to an electromagnetic shower.
The power radiated away by a particle with Brehmstrahlung radiation depends on the particle's mass- and so the electrons tend to radiate away more energy than muons....
Why are you studying neutrino detectors?

7. Sep 12, 2016

### bbbl67

So a less massive particle, radiates away more power than a more massive one? I guess I already should've known that, as taking a proton through a circular particle accelerator doesn't result in much Brehmstrahlung radiation, but doing the same thing to an electron does. Is there some formula that shows this relationship between generated Brehmstrahlung and mass?

I'm not really sure anymore, I guess curiosity really. I think I was just reading about something else, and that got me off on a tangent towards neutrino detectors. Often happens with me, I got a million questions saved up inside me, and I usually forget most of them, and then every once in a while, one comes back to the forefront and I gotta figure it out completely, before I forget it again.

Oh, BTW, I just remembered what led me to it. Somebody recently asked me something about the Weak Force, and the functional differences between the W & Z bosons, especially the Z. That then led to my sudden curiosity about neutrinos again, since they are involved in so many of the transformations caused by the Weak. I'm not a physicist, just a layman: I got a background in engineering, but not particle physics.

8. Sep 12, 2016

### ChrisVer

9. Sep 12, 2016

### bbbl67

Perfect, thanks! Interestingly, there seems to be a recurring theme in many areas of physics which seem to show that a lower-mass object seems to lose more energy than a higher mass object, for example, smaller black holes lose more energy due to Hawking Radiation than larger ones.

10. Sep 12, 2016

### ChrisVer

Well the mass powers don't coincide...

11. Sep 12, 2016

### Staff: Mentor

Bremsstrahlung, from German "bremsen" (brake) and "strahlung" (radiation). No h in "brems", two s.
This is not bremsstrahlung, it is synchrotron radiation.

The interaction of charged particles with matter or electromagnetic fields mainly depends on the speed, for high-energetic particles expressed as the Lorentz factor $\gamma$. To reach the same gamma-factor, protons need a factor 2000 more energy than electrons, muons need a factor 200 more. That is rarely the case, so electrons are typically the fastest particles around, which also means they lose the most energy.

This has nothing to do with Hawking radiation.

12. Sep 12, 2016

### bbbl67

Okie-dokie.

So, it's caused by Relativistic speeds?

Well obviously not, it's just an interesting observation. Perhaps a coincidence, that's all.

13. Sep 12, 2016

### Staff: Mentor

Yes, all the effects discussed are negligible or don't happen at nonrelativistic speeds.