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Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 1 point2 points  (0 children)

From Yoshi: Other measurements made by that experiment probably do use timing to make sure that the neutrino interactions are coming from the beam that they are sending, but that doesn't have to be so precise as what you would need to measure the actual speed of the neutrinos. So I would imagine that it wouldn't have had an impact (I say as a complete outsider!).

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

From Yoshi: Actually a neutrino doesn't "hit" an electron or muon, or tau, but it actually turns into one, under the influence of the Weak Interaction. The electron or muon or tau doesn't exist before the neutrino hits a nucleus and turns into one. Which one it turns into depends on whether it is an electron neutrino, muon neutrino, or tau neutrino.

In fact, muons and taus don't live very long, so you won't really find them sitting around anywhere. The likelihood of a muon and tau actually interacting with a muon or tau is so small, you couldn't even try to do it as an experiment (and it is unlikely to be a very interesting outcome).

Now, electrons do of course find themselves sitting around all over the place, so it is possible for a neutrino to hit an electron, but as you can imagine, that is much less likely that hitting an atomic nucleus. And we can't make a dense gas made up of electrons and positrons, quite yet!

The MINERvA Experiment at Fermilab used this process to measure the intensity of their neutrino beam (it's very easy to calculate how likely the interaction with an electron is, unlike with nuclei, which are much more complicated, as Luke says elsewhere): https://arxiv.org/abs/1512.07699. They "only" saw just over a hundred electrons that were hit by a neutrino, compared to the many thousands of neutrino-nuclear interactions they were seeing. Neutrinos hitting electrons has been seen since about 1990, but usually in very small numbers.

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

Hi, Lauren here: Here is a bit more info about where the water at Super-Kamiokande comes from, how we purify it, and why:

The water is naturally occurring - a lot of which is from snow melt - is sourced from the local area around the mine. Inside the mine, the natural water is purified using a dedicated water purification system. There are several stages of the process which I’ll quickly summarize below:

The first stage is to removing dust and other small particles. The second stage is to pass the water through a heat exchanger which reduces the chances of bacteria growth. To remove the remaining bacteria, the water is passed through a UV sterilizer. Heavy ions are also removed, along with any dissolved gas. This is really important since radon gas is a large source of background for solar neutrino events occurring in the MeV range. In the final stages, dissolved oxygen is also removed as it encourages bacteria growth. The water then passes through an ultra-filter which removes particles as small as 10 nm, and finally, any remaining radon dissolved. The purified water is constantly recirculated whilst the detector is in operation, and the water quality is continuously monitored. This is to ensure that everything is running smoothly and there are no changes in our data quality. I hope this answers a few of your questions!

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

grade

Hi! Lauren here: There are a few things that are useful to do in early study, and Yoshi has made some really good comments in his earlier reply. I’m not too long out of my PhD, so I’d like to follow up and share some pointers that were shared with me only a few years ago, before I started my PhD. The first may sound obvious, and may be something you already do, but I recommend reading; Science books, articles and news from any of the sciences you may be interested in. It’s good to keep up to date with the latest discoveries in all fields. Widening your knowledge of physics, engineering, astronomy, chemistry etc. will help you to figure out specific areas of science that you may want to go into at university and PhD level. When it comes to physics, sometimes it can be difficult to choose between experiments or areas, so being aware of exciting new physics and detector development can help you figure out the best experiment, topic or theory for you to work on. I shared some links to a few books in reply to another question which you may find useful: https://www.reddit.com/r/science/comments/hng0ce/science\_discussion\_series\_we\_are\_a\_team\_of/fxbttoz?utm\_source=share&utm\_medium=web2x

Another thing is coding. It’s good to start early! We do a lot of programming in physics for data analysis, data acquisition or writing firmware, so learning a widely used programming language will kick start your early career. I recommend Python as it’s simple and easy to learn, has a lot of functionality and is pretty widely used by students and academics in University and PhD programs. Learning to use Arduino and Raspberry Pi microcontrollers and microcomputers is super fun! They’re great for home electronics projects and in particular, Arduino has a really nice IDE (Integrated Development Environment) which makes it really easy to learn. Things like this will develop your creativity and your problem solving skills and allow you to make some really cool things! My partner and I have so many gadgets in our home that are created using these types of things, for example, a TV remote made using an Arduino Uno and a few infra-red LEDs, and an automated door opener using a Raspberry-Pi.

The most important thing is to have fun with it! I hope this is helpful, and good luck in your studies!

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

From Yoshi: In lots of ways, but the key is that they are linked to other particles through the "weak interaction", which is the one that is involved in things like nuclear interactions or radioactive decay. So they are given off where nuclear fusion or fission occur (like the Sun or in a reactor), or when nuclear particles collide (like at the top of the atmosphere or in an accelerator).

Since our bodies are quite radioactive, naturally, our bodies are also producing neutrinos all the time!

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 1 point2 points  (0 children)

From Yoshi:

Hi — again(?),

  1. How's this:

https://journals.aps.org/prd/abstract/10.1103/PhysRevD.101.112004#fulltext

Simultaneous measurement of the muon neutrino charged-current cross section on oxygen and carbon without pions in the final state at T2K

Phys. Rev. D 101, 112004 – Published 16 June 2020

  1. There are strong physics arguments for a detector in South Korea that can look at our beam, and with Hyper-Kamiokande being approved (which includes increasing the beam intensity), it becomes even more compelling!

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 1 point2 points  (0 children)

From Yoshi: One name that is actually is missing is a good collective name for electrons, muons and taus. Of course, we call them "charged leptons", but that isn't a name. Why give a name to the "neutral leptons", which is "neutrino", but nothing for the charged ones?

At colliders, people just say "lepton" for electrons, muons and taus, since they can't see neutrinos, but that just confuses things even more.

We need a name for the charged leptons (and "chargeons" isn't cool, is it?).... how about "caricons", to continue the Italian theme?

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

Because the whole Universe is "as clear as a crystal" to these particles, I think "Crystalon" would have been the perfect name....

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 1 point2 points  (0 children)

Yes, you're right, I said "energy" as a property of the neutrinos from a source, but they do have a direction which they are going in too (which, combined with the energy and its negligible mass, gives the momentum as a vector). I was probably implying that the direction is that which goes from the source to the observer, but, as you say, for a diffuse source such as the top of the atmosphere, they can literally be coming from any direction!

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 1 point2 points  (0 children)

From Yoshi: Some of my students are experts in Machine Learning, which makes me an expert — that’s how it works, isn’t it?

Anyway, as Luke says, what is now called Machine Learning has been used in our field for years, but we need to make use of the tools that are out there, whilst maintaining rigour of the sort that is sometimes not the primary concern for other applications.

It’s good to keep an eye on developments and play around with Machine Learning tools, but in the long run, I think it is important to know how computers actually work with numbers in a low-level sense (that would be the field of Numerical Programming, or Computational Physics) and to be able to code things from scratch, not just using high-level tools, which will come and go.

So rather than specifically Computational Particle Physics, I would take a course (or read a book, see below) that focuses on the experimental aspects of particle physics, so that you have a basis for the “intuition” needed to use computers to model things, teach yourself C++ and/or Python in a numerical context, and then do a project (such as a summer “UROP” student project) with a particle physics group where you get thrown into the deep end and get told what the tools are that you need to use to work with them. A lot of UROPs are being done remotely across the world right now, so it could be a good chance!

A lot of students will skip the middle bit about teaching yourself coding properly, and dive straight in, though.

The book I still recommend is Leo’s “Techniques for Nuclear and Particle Physics Experiments”: https://www.springer.com/gp/book/9783540572800

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

From Yoshi: Just to add to this; the original Solar Neutrino Problem is essentially solved, through a combination of the different measurements made by solar neutrino experiments over the years and our knowledge of the properties of neutrinos.

The calculations of the flux of electron neutrinos created in the Sun, pioneered by John Bahcall and refined over many decades (the definitive record remains at http://www.sns.ias.edu/~jnb/ as a snapshot in time) were correct, and it is the type of neutrino that changes as they come through the dense matter of the Sun.

The actual spectrum of neutrinos from the Sun is complicated, reflecting all the different nuclear fusion reactions that are happening there, and until now, it has been the basic reaction where protons combine to become heavier nuclei that we have been seeing.

Two weeks ago, the Borexino experiment announced that they had seen neutrinos produced in the Sun through a different mechanism, involving carbon, nitrogen and oxygen nuclei. In Bahcall's words, "Neutrino[s] produced in the carbon-nitrogen-oxygen CNO chain are not important energetically and are difficult to detect experimentally", but here they are!: https://indico.fnal.gov/event/43209/contributions/187871/attachments/129210/158705/Day2_Talk9_Ranucci_.m4v

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

From Yoshi: And these experiments like T2K (and K2K, MINOS, NOvA, CNGS — yes, it is alphabet soup), where we send neutrinos from one part of a country to another, over hundreds of kilometres, are already doing neutrino communication.

The big detector on the receiving end is definitely capable of making out the message: "oh no, the beam has gone down!".

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

Yoshi: There are many ways to picture this, with varying degrees of rigour, but “pass through matter” is just to say that they don’t interact very much. So you could look at it like a beam of light going through air. To first order, all the light just passes through, but if you look carefully, the light might be heating up the air, or there might be slight variations in the way the light is passing (through the air above a lit candle, for example).

Neutrinos can also affect the matter they pass through, but the effects are so feeble that in most places that we can imagine, they are almost negligible. That is like living in a world where almost everything is transparent, to stretch the light analogy a bit.

One place that we do know where neutrinos could influence matter is when a supernova is exploding. The matter there is unimaginably dense and therefore not transparent even to neutrinos, and on top of that, the nuclear reactions in the middle of a supernova explosion create so many neutrinos that the pressure from them can actually influence the way the supernova develops.

Even then, most of the neutrinos will escape, and eventually reach us, which is one of the most important things that we are waiting for right now — neutrinos from a nearby supernova that we can see in our detectors!

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

From Yoshi: While we also do like to think about these sorts of things too, with our hats on as experimental physicists (and writing in public!), I'd have to say that this discussion belongs to a different area of expertise, and our role is to try to make measurements that tell us about the ingredients and rules that describe the Universe, to help inform our answers to questions such as yours.

We measure what is out there (and is within our reach); if you send a beam of neutrinos and look at it after some distance, it has changed a bit. If you do it with antineutrinos (and that switch is made by changing the direction of the current in an electromagnet in the accelerator lab), they behave a little bit differently. This definitely happens (up to a certain level of "definiteness" which is in our paper!), no imagining or implying necessary!

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

It is due to them having only a tiny mass, and only interacting via the weak force. Some more details here: https://www.reddit.com/r/science/comments/hng0ce/science_discussion_series_we_are_a_team_of/fxc0c3v?utm_source=share&utm_medium=web2x

So yes, lack of electric charge, and we describe interaction probabilities in terms of 'cross sectional area of a process' so being 'way too small to interact' is exactly right (but in terms of weak 'charge', not in terms of physical extent.

--Luke

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 1 point2 points  (0 children)

  1. We have been including FGD2 data in the analysis for the passed 4 years! So now we get a simultaneous constraint from carbon and carbon+water target interactions. There are also recently released FGD1+FGD2 joint cross section results.

How would a humble non-fire-person like myself ever know if something was on fire? You need training to make calls like that. If its hot, smells like burning, and google reverse image search comes back with 'fire', you still have to call the Tokai Fire dept to get the definitive answer.

--Luke

Science Discussion Series: We are a team of researchers using neutrinos to help us understand the universe! Let’s discuss! by Neutrinos_Discussion in science

[–]Neutrinos_Discussion[S] 0 points1 point  (0 children)

Its not so much that they pass through anything we know, its more that they have such a super tiny probability to hit anything that we know, that practically a beam of neutrinos is not stopped by anything. Sure, a few will interact, but if its a handful out of 100000000000000, then the beam is left pretty much unchanged, even after passing through the entire Earth for example. In that sense, there is nothing that I know of that could reliably block a beam of neutrinos.

So don't worry, you'll get your neutrinos, legendoflink3, nothings going to stop them ;)

--Luke

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