♪ (𝘴𝘱𝘢𝘤𝘦𝘺 𝘱𝘪𝘢𝘯𝘰 𝘯𝘰𝘵𝘦𝘴 𝘢𝘣𝘰𝘷𝘦 𝘦𝘦𝘳𝘪𝘦 𝘴𝘺𝘯𝘵𝘩 𝘥𝘳𝘰𝘯𝘪𝘯𝘨) ♪ MATT: If it looks like we're at the sci-fi headquarters of some league of superheroes,
♪ ♪ it's because we are.
♪ (𝘢𝘥𝘥 𝘥𝘦𝘦𝘱𝘦𝘳 𝘴𝘺𝘯𝘵𝘩) ♪ This is Fermilab.
♪ (𝘢𝘥𝘥 𝘥𝘦𝘦𝘱𝘦𝘳 𝘴𝘺𝘯𝘵𝘩) ♪ For over half a century,
♪ ♪ this has been the premier particle accelerator facility of the United States.
♪ ♪ These days, many of the super-powered geniuses of Fermilab are tackling
♪ ♪ the most feeble particle in the universe:
♪ (𝘩𝘪𝘨𝘩 𝘥𝘪𝘨𝘪𝘵𝘢𝘭 𝘴𝘺𝘯𝘵𝘩 𝘦𝘯𝘵𝘦𝘳𝘴 𝘳𝘩𝘺𝘵𝘩𝘮𝘪𝘤𝘢𝘭𝘭𝘺) ♪ the neutrino.
♪ (𝘩𝘪𝘨𝘩 𝘥𝘪𝘨𝘪𝘵𝘢𝘭 𝘴𝘺𝘯𝘵𝘩 𝘦𝘯𝘵𝘦𝘳𝘴 𝘳𝘩𝘺𝘵𝘩𝘮𝘪𝘤𝘢𝘭𝘭𝘺) ♪ Why?
♪ ♪ Because, this elusive particle may hold powerful secrets,
♪ ♪ from the unification of the forces of nature,
♪ (𝘣𝘦𝘤𝘰𝘮𝘦𝘴 𝘥𝘢𝘳𝘬 𝘥𝘪𝘨𝘪𝘵𝘢𝘭 𝘴𝘺𝘯𝘵𝘩) ♪ to the biggest question of all:
♪ (𝘥𝘢𝘳𝘬 𝘥𝘪𝘨𝘪𝘵𝘢𝘭 𝘴𝘺𝘯𝘵𝘩) ♪ Why is there something rather than nothing?
♪ (𝘧𝘢𝘥𝘦 𝘰𝘶𝘵) ♪ ♪ (𝘴𝘱𝘢𝘤𝘦𝘺 𝘱𝘪𝘯𝘨 𝘳𝘦𝘷𝘦𝘳𝘣𝘦𝘳𝘢𝘵𝘦𝘴) ♪
♪ (𝘧𝘢𝘥𝘦 𝘰𝘶𝘵) ♪ (title) "SPACE TIME"
(title) "SPACE TIME"
♪ (𝘫𝘰𝘺𝘧𝘶𝘭 / 𝘢𝘯𝘵𝘪𝘤𝘪𝘱𝘢𝘵𝘰𝘳𝘺 𝘴𝘺𝘯𝘵𝘩 𝘨𝘶𝘪𝘵𝘢𝘳 𝘱𝘶𝘭𝘴𝘦𝘴) ♪ MATT: Everyone, I want you to meet Dr. Don Lincoln.
♪ (𝘫𝘰𝘺𝘧𝘶𝘭 / 𝘢𝘯𝘵𝘪𝘤𝘪𝘱𝘢𝘵𝘰𝘳𝘺 𝘴𝘺𝘯𝘵𝘩 𝘨𝘶𝘪𝘵𝘢𝘳 𝘱𝘶𝘭𝘴𝘦𝘴) ♪ So Don is a particle physics researcher here at Fermilab,
♪ ♪ So Don is a particle physics researcher here at Fermilab,
♪ ♪ but he also writes and hosts many of the awesome videos on Fermilab's youtube channel.
♪ ♪
♪ ♪ Don, Thank you for having us.
♪ ♪ DR. DON: You know, we're glad you could visit.
♪ ♪ MATT: I'm kind of obsessed with neutrinos;
♪ ♪ it seems like they could open the window into the next frontier of physics.
♪ ♪ DR. DON: We have a very broad research program,
♪ ♪ but our core research program is centered around neutrinos,
♪ ♪ and the big one - the future one - is the DUNE experiment.
♪ (𝘴𝘱𝘢𝘤𝘦𝘺 𝘴𝘺𝘯𝘵𝘩 𝘯𝘰𝘵𝘦𝘴) ♪ (text) "Deep Underground Neutrino Experiment" Its core - and sort of the central most important thing that it's looking for -
♪ ♪ (text) "Deep Underground Neutrino Experiment" is to study whether or not matter and antimatter actually act differently.
♪ ♪ As you know from E=mc^2, matter and antimatter should be the same,
♪ ♪ and they're not.
♪ ♪ DUNE may tell us why.
♪ ♪ MATT: Well, it sounds like we probably need to learn a little bit more about neutrinos.
♪ (𝘥𝘢𝘳𝘬 𝘴𝘺𝘯𝘵𝘩 𝘧𝘳𝘰𝘮 𝘪𝘯𝘵𝘳𝘰) ♪
♪ (𝘥𝘢𝘳𝘬 𝘴𝘺𝘯𝘵𝘩 𝘧𝘳𝘰𝘮 𝘪𝘯𝘵𝘳𝘰) ♪ DR. DON: Neutrinos are elementary particles of a type called leptons.
♪ ♪ DR. DON (voiceover): That's the same family as the familiar electron
♪ ♪ and it's heavier cousins the muon and tau particle.
♪ ♪
♪ ♪ Neutrinos also come in three flavors:
♪ ♪ one for each of the charged leptons.
♪ ♪ So we have the electron neutrino,
♪ ♪ muon neutrino, and tau neutrino.
♪ ♪
♪ (𝘢𝘥𝘥 𝘥𝘦𝘦𝘱𝘦𝘳 𝘴𝘺𝘯𝘵𝘩) ♪ But all neutrinos have the bizarre quality that they oscillate between these types over time.
♪ ♪ But all neutrinos have the bizarre quality that they oscillate between these types over time.
♪ ♪
♪ ♪ Measuring neutrino oscillations is a big part of how we unlock their secrets, but it's not easy.
♪ ♪
♪ ♪ Neutrinos are among the most elusive elementary particles of nature,
♪ ♪ only interacting by the weak nuclear force and gravity.
♪ ♪ DR. DON (voiceover): In fact, it would take a wall of lead five light-years thick to have a 50/50 chance at stopping a single neutrino from the Sun.
♪ ♪ Figuring out ways to detect them is tricky to say the least.
♪ (𝘧𝘢𝘥𝘦 𝘵𝘰 𝘭𝘪𝘨𝘩𝘵 𝘳𝘩𝘺𝘵𝘩𝘮𝘪𝘤 𝘨𝘶𝘪𝘵𝘢𝘳 𝘱𝘪𝘤𝘬𝘪𝘯𝘨)♪ (title) "MINOS: Main Injector Neutrino Oscillation Search"
♪ (𝘭𝘪𝘨𝘩𝘵 𝘳𝘩𝘺𝘵𝘩𝘮𝘪𝘤 𝘨𝘶𝘪𝘵𝘢𝘳 𝘱𝘪𝘤𝘬𝘪𝘯𝘨) ♪ MATT: The weakly interacting nature of the neutrino makes them insanely difficult to detect,
♪ ♪ and we'll be seeing exactly how that's done soon.
♪ ♪ But in order to have a chance at spotting even one single neutrino,
♪ ♪ a truly enormous number needs to reach the detector.
♪ (𝘷𝘦𝘳𝘺 𝘴𝘰𝘧𝘵 𝘴𝘱𝘢𝘤𝘦𝘺 𝘨𝘶𝘪𝘵𝘢𝘳) ♪ In order to do that, neutrinos need to be focused into a beam.
♪ (𝘴𝘪𝘯𝘨𝘭𝘦 𝘴𝘱𝘢𝘤𝘦𝘺 𝘨𝘶𝘪𝘵𝘢𝘳 𝘸𝘩𝘢𝘮𝘮𝘺) ♪ But, if neutrinos are so weakly interacting,
♪ ♪ how do we channel them into a beam in the first place?
♪ ♪ The answer is:
♪ ♪ We don't; at least, not directly.
♪ (𝘴𝘰𝘧𝘵 𝘸𝘩𝘢𝘮𝘮𝘺) ♪ We don't; at least, not directly.
♪ ♪ MATT (voiceover): The main Fermilab beam line accelerates protons around a two and a half mile circumference ring, using giant electromagnets,
♪ (𝘳𝘩𝘺𝘵𝘩𝘮 𝘣𝘶𝘪𝘭𝘥𝘴) ♪ to around 99.997% the speed of light.
♪ ♪ That's possible because, unlike neutrinos, protons have an electric charge.
♪ ♪ Those protons are then smashed into a graphite barrier,
♪ ♪ and as they collide with nuclei they produce all sorts of particles.
♪ ♪ More magnetic fields are used to sort the positively charged pion particles from the debris
♪ ♪ and focus *them* into a beam.
♪ ♪ Those pions quickly decay into muons and muon neutrinos.
♪ (𝘴𝘰𝘧𝘵 𝘢𝘯𝘥 𝘴𝘱𝘢𝘤𝘦𝘺 𝘢𝘨𝘢𝘪𝘯) ♪ The beam then passes through several hundred meters of solid rock, which blocks the muons,
♪ ♪ The beam then passes through several hundred meters of solid rock, which blocks the muons,
♪ (𝘴𝘰𝘧𝘵 𝘸𝘩𝘢𝘮𝘮𝘺) ♪ but the neutrinos pass straight through into an almost pure beam of muon neutrinos
♪ ♪ but the neutrinos pass straight through into an almost pure beam of muon neutrinos
♪ ♪ ready to be sent to our detector.
♪ (𝘧𝘢𝘥𝘦 𝘵𝘰 𝘴𝘰𝘧𝘵ly 𝘣𝘳𝘰𝘰𝘥𝘪𝘯𝘨 𝘴𝘺𝘯𝘵𝘩 𝘱𝘶𝘭𝘴𝘦𝘴) ♪ (title) "ICARUS (Imaging Cosmic And Rare Underground Signals): Liquid Argon Neutrino Hunter"
♪ ♪ MATT: Down here, we have the ICARUS neutrino detector.
♪ ♪ And, as awesome a piece of science equipment as this looks,
♪ ♪ It's definitely not five light-years of lead.
♪ ♪ How is it supposed to stop a neutrino?
♪ ♪ DR. DON: Well,
♪ ♪ it's entirely probabilistic.
♪ ♪ Each neutrino has only a *tiny* possibility of interacting with any particular argon atom,
♪ ♪ so what we do is we shoot 10 trillion neutrinos per second through this detector,
♪ ♪ and only a handful of them actually interact.
♪ (𝘴𝘱𝘢𝘤𝘦𝘺 𝘴𝘺𝘯𝘵𝘩 𝘣𝘦𝘭𝘭 𝘵𝘰𝘯𝘦𝘴) ♪ And so, by doing that, we're able to understand what's going on.
♪ ♪ MATT: I think we should go down there.
♪ ♪ Let me try to give you a sense of why neutrinos are so elusive.
♪ ♪ As we mentioned: they only experience the weak nuclear force and gravity,
♪ ((𝘴𝘰𝘧𝘵)) ♪ and the latter is so weak we can ignore it altogether.
♪ ((𝘴𝘰𝘧𝘵)) ♪ MATT (voiceover): In order to interact with other types of matter, a neutrino needs to
♪ (𝘩𝘪𝘨𝘩 𝘴𝘺𝘯𝘵𝘩 𝘸𝘩𝘪𝘯𝘦 𝘧𝘢𝘥𝘦𝘴 𝘪𝘯) ♪ exchange one of the carriers of the weak force:
♪ ♪ a W or Z boson;
♪ (𝘤𝘰𝘯𝘵𝘦𝘮𝘱𝘭𝘢𝘵𝘪𝘷𝘦 𝘦𝘭𝘦𝘤𝘵𝘳𝘪𝘤 𝘱𝘪𝘢𝘯𝘰 𝘴𝘰𝘧𝘵𝘭𝘺 𝘢𝘳𝘱𝘦𝘨𝘨𝘪𝘢𝘵𝘦𝘴) ♪ or, truly, a virtual boson. It exists only for an instant -
♪ (𝘤𝘰𝘯𝘵𝘦𝘮𝘱𝘭𝘢𝘵𝘪𝘷𝘦 𝘦𝘭𝘦𝘤𝘵𝘳𝘪𝘤 𝘱𝘪𝘢𝘯𝘰 𝘴𝘰𝘧𝘵𝘭𝘺 𝘢𝘳𝘱𝘦𝘨𝘨𝘪𝘢𝘵𝘦𝘴) ♪ just long enough to exchange energy between the neutrino and, say the nucleus of an atom.
♪ ♪ just long enough to exchange energy between the neutrino and, say the nucleus of an atom.
♪ ♪ It borrows the energy it needs to exist from, well, nowhere, really.
♪ ♪ It's sort of cheats energy conservation by taking advantage of the Heisenberg uncertainty principle,
♪ ♪ which tells us that there's a fundamental uncertainty
♪ ♪ between certain pairs of properties, in this case, energy and time.
♪ ♪
♪ ♪ So: the briefer the lifetime of this virtual boson, the more energy it's allowed to borrow.
♪ (𝘥𝘳𝘢𝘮𝘢𝘵𝘪𝘤 𝘱𝘢𝘶𝘴𝘦, 𝘵𝘩𝘦𝘯 𝘴𝘢𝘮𝘦 𝘱𝘪𝘢𝘯𝘰 𝘢𝘳𝘱𝘦𝘨𝘨𝘪𝘰) ♪ Now, the thing about the weak force bosons is that they are massive,
♪ ♪ unlike the massless photon or gluon, which carry the electromagnetic and strong nuclear forces.
♪ ♪ In order to exist, they need to borrow a lot of energy to cover their rest mass.
♪ ♪ That greatly limits the amount of time they can exist,
♪ ♪ and so limits the distance that they can travel.
♪ ♪ In order for a neutrino to interact with an atomic nucleus
♪ ♪ it needs to pass so close that it's essentially inside the nucleus.
♪ ♪ In other words:
♪ ♪ we need a direct hit.
♪ ♪ DR. DON: And if a neutrino interacts in our detector,
♪ ♪ an Argon nucleus is broken apart and charged particles are released - in particular, pions and muons.
♪ ♪ Those particles then travel through the liquid argon knocking electrons free from atoms.
♪ ♪ We charge the sides of the detector, so a giant electric field fills the entire tank.
♪ ♪ That draws these free electrons to the walls of the tank, which lets us trace out the path of the particles
♪ ♪ From those paths, we can learn all about the neutrino oscillation,
♪ ♪ and that includes the flavour of the neutrino that caused it - be it an electron, muon, or tau neutrino.
♪ ♪ But remember: our neutrino source produces only muon neutrinos,
♪ ♪ so if we detect a tau or electron neutrino, then we've seen neutrino oscillation.
♪ ♪ We can use our measurement to determine how much oscillation has occurred.
♪ ♪ When we add that we know how far the neutrinos traveled at the speed of light, we know how fast they oscillate.
♪ ♪ ICARUS is much smaller than the upcoming DUNE experiment.
♪ ♪ Let's see part of the new accelerator that's being built to feed DUNE.
♪ (𝘥𝘦𝘦𝘱 𝘦𝘦𝘳𝘪𝘦 𝘴𝘺𝘯𝘵𝘩 𝘥𝘳𝘰𝘯𝘦, 𝘰𝘤𝘤𝘢𝘴𝘪𝘰𝘯𝘢𝘭𝘭𝘺 𝘴𝘸𝘦𝘭𝘭𝘴) ♪ (title) "PIP - II: Proton Improvement Plan - II"
♪ ♪ MATT: We are standing in front of the injection test accelerator for 'PIP-II' - that's the Proton Improvement Plan Two -
♪ ♪ which is going to *massively* increase the number of neutrinos
♪ ♪ that Fermilab will be able to send to the DUNE experiments.
♪ (𝘴𝘸𝘦𝘭𝘭𝘴) ♪ Don, I think you need to tell us a bit about how DUNE is actually going to work.
♪ (𝘵𝘦𝘤𝘩𝘺 𝘴𝘺𝘯𝘵𝘩 𝘢𝘯𝘥 𝘣𝘶𝘪𝘭𝘥𝘪𝘯𝘨 𝘳𝘩𝘺𝘵𝘩𝘮 𝘧𝘢𝘥𝘦 𝘰𝘷𝘦𝘳) ♪ DR. DON: Sure. Well, what we're gonna do is we're going to send a super intense beam of neutrinos through the Earth
♪ ♪ 1,300 kilometers from Chicago to South Dakota, where
♪ ♪ a huge detector weighing 70,000 tons
♪ ♪ consisting of liquid argon and located a mile underground
♪ ♪ will catch the beam and tell us what happened to the neutrinos as they passed from here to there.
♪ (𝘴𝘺𝘯𝘵𝘩 𝘥𝘳𝘰𝘯𝘦 𝘣𝘢𝘤𝘬 𝘪𝘯 𝘧𝘰𝘤𝘶𝘴) ♪ MATT: Which will, hopefully, tell us something fundamental about the difference between matter and antimatter
♪ ♪ Which, also hopefully, will tell us why we live in a universe made of matter in the first place.
♪ ♪ MATT (voiceover): Our best understanding of particle physics tells us that matter and antimatter
♪ (𝘭𝘰𝘸 𝘦𝘯𝘥 𝘰𝘧 𝘴𝘺𝘯𝘵𝘩 𝘧𝘢𝘥𝘦𝘴) ♪ should have been created in equal quantities in the early universe,
♪ (𝘩𝘪𝘨𝘩 𝘦𝘯𝘥 𝘰𝘧 𝘴𝘺𝘯𝘵𝘩 𝘥𝘳𝘰𝘯𝘦 𝘸𝘪𝘵𝘩 𝘴𝘰𝘧𝘵, 𝘵𝘢𝘱𝘱𝘪𝘯𝘨 𝘳𝘩𝘺𝘵𝘩𝘮) ♪ and so, should have perfectly annihilated each other
♪ ♪ leaving a universe of only photons.
♪ ♪ The fact that we see a universe full of matter
♪ (𝘷𝘰𝘭𝘶𝘮𝘦 𝘣𝘶𝘪𝘭𝘥𝘴, 𝘴𝘺𝘯𝘵𝘩 𝘴𝘵𝘳𝘪𝘯𝘨 𝘱𝘭𝘶𝘤𝘬 𝘧𝘢𝘥𝘦𝘴 𝘰𝘷𝘦𝘳) ♪ means there must have been a tiny imbalance between matter and antimatter,
♪ (𝘴𝘰𝘧𝘵 𝘩𝘰𝘳𝘯 𝘣𝘶𝘳𝘴𝘵, 𝘩𝘪𝘨𝘩 𝘴𝘺𝘯𝘵𝘩) ♪ enough to leave a bit of leftover stuff to produce the stars and galaxies and
♪ ♪ particle physicists that we see around us today.
♪ (𝘭𝘰𝘸 𝘴𝘺𝘯𝘵𝘩 𝘥𝘳𝘰𝘯𝘦 𝘳𝘦𝘵𝘶𝘳𝘯𝘴) ♪ In order for that to happen,
♪ ♪ there must have been a tiny asymmetry
♪ (𝘭𝘰𝘸 𝘴𝘸𝘦𝘭𝘭) ♪ between the behavior of matter and antimatter.
♪ (𝘭𝘰𝘸 𝘴𝘸𝘦𝘭𝘭) ♪ The full details of that are speculative,
♪ ♪ but one possibility is 'leptogenesis':
♪ ♪ a hypothetical physical process that may have occurred right after the Big Bang.
♪ (𝘴𝘭𝘰𝘸𝘭𝘺 𝘧𝘢𝘥𝘦 𝘰𝘶𝘵) ♪ a hypothetical physical process that may have occurred right after the Big Bang.
And, Don has already made an excellent video on the subject, which you should check out.
♪ (𝘥𝘪𝘧𝘧𝘶𝘴𝘦 𝘦𝘵𝘩𝘦𝘳𝘦𝘢𝘭 𝘣𝘦𝘭𝘭 𝘵𝘰𝘯𝘦𝘴 𝘧𝘢𝘥𝘦 𝘪𝘯)♪ And, Don has already made an excellent video on the subject, which you should check out.
♪ (𝘥𝘪𝘧𝘧𝘶𝘴𝘦 𝘦𝘵𝘩𝘦𝘳𝘦𝘢𝘭 𝘣𝘦𝘭𝘭 𝘵𝘰𝘯𝘦𝘴 𝘧𝘢𝘥𝘦 𝘪𝘯)♪ DR. DON: But, the short version is that, according to leptogenesis,
♪ ♪ DR. DON: But, the short version is that, according to leptogenesis,
♪ ♪ DR. DON (voiceover): neutrinos in the early universe may have decayed into other matter particles,
♪ ♪ with matter neutrinos producing antimatter particles,
♪ ♪ and antimatter neutrinos - or anti-neutrinos - producing matter particles.
♪ ♪ DR. DON: If there *was* an imbalance in the number of neutrinos versus anti neutrinos,
♪ ♪ that could lead to an ultimate imbalance in the amount of matter versus antimatter.
♪ ♪ DR. DON (voiceover): And, that same initial imbalance should also be reflected in the way neutrinos oscillate:
♪ ♪ with anti-neutrinos oscillating between the three different types more slowly than matter neutrinos.
♪ ♪ DR. DON: And *that* is what the DUNE experiment seeks to detect.
♪ ♪ MATT: Well, it sounds like you all have a *lot* of work ahead of you, so we're gonna get out of your hair,
♪ ♪ but thank you so much for taking us literally behind the scenes.
♪ ♪ DR. DON: You know, you're welcome to come anytime,
♪ ♪ we love Space Time.
♪ ♪ MATT: And we love Fermilab.
♪ ♪
♪ ♪ And that is how you study the most elusive particle in the universe.
♪ ♪ Check out the Fermilab channel for a much deeper dive into neutrinos and lots lots more.
♪ ♪ It's honestly one of my go-to resources when I'm researching
♪ ♪ a new episode of a Space Time.
♪ (𝘦𝘵𝘩𝘦𝘳𝘦𝘢𝘭 𝘣𝘦𝘭𝘭𝘴 𝘴𝘭𝘰𝘸𝘭𝘺 𝘧𝘢𝘥𝘦 𝘰𝘶𝘵) ♪
♪ (𝘦𝘵𝘩𝘦𝘳𝘦𝘢𝘭 𝘣𝘦𝘭𝘭𝘴 𝘴𝘭𝘰𝘸𝘭𝘺 𝘧𝘢𝘥𝘦 𝘰𝘶𝘵) ♪ (title) "SPACE TIME"
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