Category Archives: Quantum Physics

Anita Daher (Brian Stefaniuk)

Peanut Butter and Chaos is the first entry in Anita Dahers new middle-grade fantasy series, The Mythic Adventures of Samuel Templeton, where real science meets imagination.

Sam Templeton has been brought up by his distracted former-scientist father to apply the scientific method to any problem, so when he feels his father doesnt see him anymore, he poses the question: Am I invisible? After careful observation and data collection, he concludes that yes, he is. Happily, that doesnt last long. His father is forced to pay attention when Sam is struck by blue lightning and jerked into an altered state of being. Sam now sees the world in shifting pixel-like cubes, and his strange new vision enables him to perceive the displaced but charming Flum, a non-binary being from an alternate reality who slipped into this reality via the same lightning strike that hit Sam. Oddly, this blue lightning also coincided with the disappearance of Thyla, Sams too-perfect neighbour who no one else seems to remember.

After many tests at the hospital, Sam is assured that his visual impairment will wear off. For Sam, its a race against time to figure out how to get Flum back to their own world and discover what happened to Thyla. If only his father would quit tripping over his own feet and getting arrested for assaulting police officers, Sam could concentrate on figuring out the science behind alternate realities and the extraordinary power he now has to rearrange matter. Oh and somehow, its all tied up with his mother, Dory, who disappeared when Sam was two years old.

Peanut Butter and Chaos is an amusing, fast-paced adventure with broad appeal for young readers. Since most of Sams wild experiences are grounded in science, curious middle-graders may speculate about what is actually possible within the bounds of quantum physics. Sam is a blundering but likeable hero, and Flum could easily be E.T.s lovable younger sibling. Together, they confront baby skunks and RCMP officers and make a daring jailbreak by walking through walls. Many of the adventures are punctuated by new and alarming ways to eat peanut butter.

At times, the book suffers from stretching science and probability just a little too far (literally: the tunnel Sam and Flum dig must be half a mile long), and the detailed scientific explanations get a little tedious. But the book is ultimately whimsical, fun and a very good start to what could be a satisfying and successful series. Underlying it all is a mysterious Icelandic mythology and a hovering villain that are bound to play larger parts in subsequent books.

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Peanut Butter and Chaos: The Mythic Adventures of Samuel Templeton - Quill & Quire

image:Researchers at Dartmouth have built the worlds first superfluid circuit that uses pairs of ultracold electron-like atoms. view more

Credit: Robert Gill/Dartmouth College

HANOVER, N.H. April 19, 2022 Researchers at Dartmouth have built the worlds first superfluid circuit that uses pairs of ultracold electron-like atoms, according to a study published in Physical Review Letters.

The laboratory test bed gives physicists control over the strength of interactions between atoms, providing a new way to explore the phenomena behind exotic materials such as superconductors.

Much of modern technology revolves around controlling the flow of electrons around circuits, said Kevin Wright, assistant professor of physics at Dartmouth and senior researcher of the study. By using electron-like atoms we can test theories in ways that were not possible before.

While conductive materials such as copper are well understood, researchers do not completely understand how electrons move or can be controlled in exotic materials like topological insulators and superconductors that can be useful for building quantum computers.

The new circuit acts as a quantum emulator to explore how electrons work in real materials, offering a way to analyze the movement of electrons in a highly controllable setting.

Electrons can do things that are far more strange and rich than anyone imagined, said Wright. We are learning about electrons without using electrons.

Atomic particles are either bosons or fermions. Bosons, such as photons, tend to bunch together. Fermions, such as electrons, tend to avoid each other. While superfluid circuits using ultracold boson-like atoms already exist, the Dartmouth circuit is the first to use ultracold atoms that act as fermions.

The circuit operates on the isotope lithium-6. Although lithium-6 is a complete atom, it has properties that make it act like an individual electron. The behavior of the complete atom serves as an analogue for individual electrons.

"If we could scale the properties of lithium-6 atoms to electrons, they would be flowing without resistance even above room temperature, said Yanping Cai, the first author of the paper who wrote the paper as a Dartmouth PhD candidate. Studying these simple circuits might provide insights about high-temperature superconductivity."

Laser light is used in the microscopic circuit to cool clouds of lithium atoms to temperatures near absolute zero. Once the atoms are slowed, the researchers can then hold them in place, move them around, or otherwise control them in ways that mimic how individual electrons flow around superconducting circuits.

By adjusting magnetic fields, the team can change the way the atoms interact, making the fermions attract or repel each other with varying strength, a feature that is not possible with individual electrons or other superfluid systems such as liquid helium.

According to the researchers, lasers have been used in similar techniques in other experiments, but this is the first atomic circuit that is tunable in this way. The lasers also provide the structure of the circuit and detect how the atoms are acting.

We have crossed the threshold to build test circuits with fermionic quantum gases, said Wright. Designing and controlling the atom flow around a circuit with ultracold fermions in the same way that is done in an electronic device has never been accomplished before.

The approach will allow researchers to study the formation and decay of persistent currents that flow indefinitely without energy input.

The ability to emulate superconducting circuits could open large experimental possibilities to test theories and to analyze materials with unique properties. The research could create opportunities for the development of new kinds of devices that use superconductors and other exotic quantum materials.

Co-authors of the research paper include Dartmouth PhD candidates Daniel Allman and Parth Sabharwal. The work was funded by the National Science Foundation. Future work will be supported by a NSF CAREER award.

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Physical Review Letters

Persistent Currents in Rings of Ultracold Fermionic Atoms

19-Mar-2022

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Lab creates superfluid circuit using fermions to study electron behavior - EurekAlert

Dov Moran - inventor of the disk-on-key, Managing Partner at Grove Ventures, which invests in Israeli early stage start-ups

My wife and I have been married for 40 years, and 20 years ago she became religious. We have four children, and each is a different world in terms of their closeness to religion. The eldest is the most non-religious, the second is traditional, the third is more religious, and the youngest studied for two years at a yeshiva in Netivot. The first time he came back from the yeshiva I asked him: 'What did you learn?' and he answered 'Judaism', but while he was talking about Judaism (yahadut), I heard 'Destinations'. (yaadut). He replied that there was no such word, but I was caught up in that concept."

"To me yaadut means living with a goal. Living your life with a real purpose. Not just trying to make as much money as possible, I have no such ambition. After that conversation with my son I wrote a book that has not yet come out, 'Goals, Doors (Entrepreneurship) and Music'. It was at a time that I was angry at the religious approach, and the book came out extremely anti-religious. Friends told me, 'You're cutting down Judaism in an excessive manner,' and I decided to polish up the angry parts, because in the end I believe religion can do good for its believers.

1

Dov Moran (Photo: Edward Kaprov. The photo was taken using the wet plate collodion technique, an early photographic process invented in the 19th century.)

When did the children choose a direction?

"It develops organically, each child chooses their own direction, and it still develops. For me too. I am constantly changing."

Do you have a hard time with the possibility that your children will become ultra-Orthodox?

"Fortunately, none of them went that far. As far as my kids go, I have a variety, and in any case I respect each of them, because they have faith. I prefer an ultra-Orthodox person to someone who has no faith in anything, someone who has no values or morals and no vocation in life other than having fun. I think I was able to convey to them a little bit of the belief in the goals."

How does a secular high-tech man manage to fit in with religious beliefs at home?

"It does not have to fit in. I live my life and my wife lives hers."

"There is no clash which needs to arise from this area. Everyone lives their own life, on their own hours and times."

It requires sacrifice from both of you.

"Yes. But we are constantly sacrificing in life, no? You come to a meeting with investors and wear a suit - that's a certain sacrifice. I have partners in the fund, and that's the biggest compromise of them all. Do you know how much I compromise with them? And they do too. I compromise all the time, every day. You don't need to optimize pleasure, fun and happiness. Anyone who tells you they never compromise in life is cheating themselves.

What are you compromising on and what are others compromising on for you?

"On Saturday (Shabbat) I try very hard not to travel. I can travel, no one will shoot me, but I do not want to cause others to feel bad. I have been a vegetarian from the age of 10, so regarding keeping kosher I already dont have a hard problem. I do not pray, and if one of my children does go to a synagogue, they do not pressure me to come along. On Shabbat I make Kiddush. To say that I believe in the need to say the particular blessing? Dont be ridiculous. I do not think God wanted me to say that, but it is important to others. If I were alone I would not make Kiddush. I fast on Yom Kippur, but more because of tradition, and I suppose I would do that even if I were alone - but not out of fear of divine punishment. I am a person who is more compromising than others compromising for me, and I am also less of a person who thinks he is always right. I always try to understand the other side."

"In things that are not a matter of principle for me. In what is very principled and related to myself, I do not compromise. Not even with myself."

"I just know I do not know. I think with high certainty that there is no entity that expects you to do anything concrete, like pray certain prayers or not turn on electricity on Shabbat. Just last week I was at a lecture on quantum theory, and even the physics we see and experience is so full of mystery and there is a lot of uncertainty in it. The great physicists said that there are phenomena that they are far from understanding. So I know there are things I do not know."

I ask because you are a science-biased person.

"Of course. I believe in science, in technology, in progress. It does not contradict the knowledge that I do not know and do not understand many things."

Did you grow up as a secular child?

"I grew up weird. I was born in a traditional house but my father did not wear a kippah. I was a child who wore a kippah, went to a secular school but did not believe in normal religion. My father once went to a parents' meeting and the religious Talmud teacher asked him how it could be that his son wore a kippah and he did not, and from then on, he started wearing one too."

And after years of high-tech and entrepreneurship and exits, you came to music at a later age as well.

"I'm very realistic, but I have a humane side that I do not give up on. I play drums in a rock band and love music, especially the blues and Pink Floyd. I have never played Israeli music, and then, five years ago, at Yossi Vardi's Kinnernet event, someone played the percussion and she left the stage to go down to eat and I said to her, 'I will replace you,' and I went on stage. At first I hesitated, but the guys around me encouraged me and I did it. I had a lot of fun."

And it progressed from there?

"Shortly afterwards, at an investor conference, we invited the Shalva band to sing, wonderful young people with disabilities - and who among us doesn't have one? I have one too! - and I offered to play with them a bit on the percussion. The band manager agreed but asked me to come and practice. After thoroughly enjoying the experience, I bought Conga drums and I started playing with a band of wonderful guys from the area, who are also gifted musicians. Today we have a show whose theme is the connection between music and entrepreneurship."

And what is the connection?

Take the song 'Cypress' (by Ehud Manor and Ariel Zilber), for example: 'And I saw a cypress, standing in a field in front of the sun. In a heat wave, in a cold front, in front of the storm. On its side, the cypress leaned, unbroken, bending its top to the grass. Even an entrepreneur sometimes has to bow his head. There is trouble, money is gone, things are happening. A good entrepreneur is one who does not stand upright all the time. In my life I had to bend many times.

"There are failures, where you fall, crash and have to rebuild yourself. In Modu (a start-up that developed a modular mobile), for example, I crashed. And I remember in M-Systems (the maker of the disk-on-key) that customers were annoyed, and even when the fault is their fault you have to be polite to them, like towards demanding investors or powerful suppliers. Sometimes you want to do that, but the market wants something different, and sometimes you have to do what the market wants. You want to sell at 200 but the market wants at 99. Sometimes you have to fire people, it's happened to me three times in my life. These are people you liked, they trusted you, and in the end you had to fire them. So you lower your head again and bend over."

Given the risks of start-ups and venture capital, do you feel lucky about the times it worked for you?

"In the book I wrote I'm talking about doors where the chances of each one opening are slim. If the entrepreneur is lazy he will try to open only five doors. If he is diligent, he will try all 100. And yet the open door may still be 101. I work hard and I know there are others who are more successful than me, maybe because they are more talented. I do not believe in a golden touch. Its nonsense."

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"I live my life my way and my wife lives hers as a religious person. It does not have to fit in" - CTech

We will study about Quantum Physics and Classical physics, Newtons laws of motion can explain the behaviour of macroscopic objects or objects that are at a scale of human interaction and experience, even including astronomical objects. But classical physics isnt able to explain the behaviour of macroscopic objects or objects that are at a scale of an atom.

This is mainly because the behaviour of macroscopic objects is practically particle in nature, they do have wave nature but it is negligible because of their huge masses; whereas on the other hand the atomic level particles have very little mass and hence both particle and wave nature is prevalent in them. This dual behaviour of displaying both particle and wave nature is known as dual behaviour of matter and for every particle, the particle nature comes from its mass and the wave nature comes from its matter-wave defined by De-Broglie relationship which is given by,

=

(begin{array}{l} frac {h}{mv}end{array} )

Where,

= wavelength of the matter

h = planks constant

m = mass of the matter

v = velocity of matter

Classical Physics hasnt been able to explain the dual behaviour of a matter and Heisenbergs uncertainty principle, according to which the position and momentum of a sub-atomic particle can be calculated simultaneously with some degree of inaccuracy. Hence, there was a need for a new theory that could explain the behaviour of atomic and sub-atomic particles.

So, this led to the birth of quantum physics It is a branch of science that explains the physical phenomenon by microscopic and atomic approach and takes into account the dual behaviour of matter. It is theoretical physics and it specifies the laws of motion that the microscopic objects obey. When quantum mechanics is applied to macroscopic objects (for which wave-like properties are insignificant) the results are the same as those from classical mechanics.

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Quantum Physics - Definition & Formula | Classical Physics | Dual Behaviour ...

There is a worldwide research effort exploring the potentials of quantum mechanics for applications. The field began with Feynmans proposal in 1981 at MIT Endicott House to build a computer that takes advantage of quantum mechanics and has grown enormously since Peter Shors 1994 quantum factoring algorithm. The idea of utilizing quantum mechanics to process information has since grown from computation and communication to encompass diverse topics such as sensing and simulations in biology and chemistry. Leaving aside the extensive experimental efforts to build controllable large-scale quantum devices, theory research in quantum information science (QIS) investigates several themes:

QIS theory research at MIT spans all of these areas. The CTP faculty involved are: Soonwon Choi and Aram Harrow, and the larger group at MIT includes Isaac Chuang (EECS/physics), Seth Lloyd (Mech. Eng.), Anand Natarajan (EECS) and Peter Shor (Math). Other faculty in the area include Eddie Farhi (emeritus), Jeffrey Goldstone (emeritus) and Jeff Shapiro (EECS, emeritus). Together this forms a large and vibrant group working in all areas of QIS.

Some of the notable contributions involving the CTP include the quantum adiabatic algorithm and quantum walk algorithms (Farhi, Goldstone), the first example of a problem for which quantum computers exhibit no speedup (Farhi, Goldstone), proposals for unforgeable quantum money (Farhi, Shor), a quantum algorithm for linear systems of equations (Harrow, Lloyd), efficient protocols for simulating quantum channels (Harrow, Shor), both algorithms and hardness results for testing entanglement (Harrow), proposals for quantum approximate optimization algorithms (Farhi, Goldstone), proposals and experimental observations of exotic quantum dynamics such as slow thermalization or a discrete time crystalline phase in quantum simulators (Choi), quantum sensing protocols using strongly interacting spin ensembles (Choi), and quantum convolutional neural networks (Choi). Ongoing research at MIT in QIS includes work on new quantum algorithms, efficient simulations of quantum systems, methods to characterize and control existing or near-term quantum hardwares, connections to many-body physics, applications in high-energy physics, and many other topics.

The larger QIS group at MIT shares a seminar series, a weekly group meeting, regular events for grad students.

Interdepartmental course offerings include an introductory and an advanced class in core QI/QC, as well as occasional advanced special topics classes. Quantum information has also entered the undergraduate physics curriculum with a junior lab experiment on NMR quantum computing and some lectures in the 8.04/8.05/8.06 sequence on quantum computing.

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Quantum Information Science - MIT Physics

Physicists have found that an elementary particle called the W boson appears to be 0.1% too heavy a tiny discrepancy that could foreshadow a huge shift in fundamental physics.

The measurement, reported today in the journal Science, comes from a vintage particle collider at the Fermi National Accelerator Laboratory in Batavia, Illinois, that smashed its final protons a decade ago. The roughly 400 members of the Collider Detector at Fermilab (CDF) collaboration have continued to analyze W bosons produced by the collider, called the Tevatron, chasing down myriad sources of error to reach an unparalleled level of precision.

If the Ws excess heft relative to the standard theoretical prediction can be independently confirmed, the finding would imply the existence of undiscovered particles or forces and would bring about the first major rewriting of the laws of quantum physics in half a century.

This would be a complete change in how we see the world, potentially even rivaling the 2012 discovery of the Higgs boson in significance, said Sven Heinemeyer, a physicist at the Institute for Theoretical Physics in Madrid who is not part of CDF. The Higgs fit well into the previously known picture. This one would be a completely new area to be entered.

The finding comes at a time when the physics community hungers for flaws in the Standard Model of particle physics, the long-reigning set of equations capturing all known particles and forces. The Standard Model is known to be incomplete, leaving various grand mysteries unsolved, such as the nature of dark matter. The CDF collaborations strong track record makes their new result a credible threat to the Standard Model.

Theyve produced hundreds of beautiful measurements, said Aida El-Khadra, a theoretical physicist at the University of Illinois, Urbana-Champaign. Theyre known to be careful.

But no one is popping champagne yet. While the new W mass measurement, taken alone, departs starkly from the Standard Models prediction, other experiments weighing the W have produced less dramatic (albeit less precise) results. In 2017, for instance, the ATLAS experiment at Europes Large Hadron Collider measured the W particles mass and found it to be only a hair heavier than what the Standard Model says. The clash between CDF and ATLAS suggests that one or both groups has overlooked some subtle quirk of their experiments.

I would like it to be confirmed and to understand the difference from prior measurements, said Guillaume Unal, a physicist at CERN, the laboratory that houses the Large Hadron Collider, and a member of the ATLAS experiment. The W boson has to be the same on both sides of the Atlantic.

Its a monumental piece of work, said Frank Wilczek, a Nobel Prize-winning physicist at the Massachusetts Institute of Technology, but its very hard to know what to do with it.

W bosons, together with Z bosons, mediate the weak force, one of the universes four fundamental forces. Unlike gravity, electromagnetism and the strong force, the weak force doesnt push or pull so much as it transforms heavier particles into lighter ones. A muon spontaneously decays into a W boson and a neutrino, for instance, and the W then becomes an electron and another neutrino. Related subatomic shape-shifting causes radioactivity and helps keep the sun shining.

Assorted experiments have measured the W and Z bosons masses over the last 40 years. The W bosons mass has proved an especially alluring target. Whereas other particle masses must simply be measured and accepted as facts of nature, the W mass can be predicted by combining a handful of other measurable quantum properties in the Standard Model equations.

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Fermilab Says Particle Is Heavy Enough to Break the Standard Model - Quanta Magazine

Almost 400 years ago, in The Assayer, Galileo wrote: Philosophy is written in this grand book, the universe [But the book] is written in the language of mathematics. He was much more than an astronomer, and this can almost be thought of as the first writing on the scientific method.

We do not know who first started applying mathematics to scientific study, but it is plausible that it was the Babylonians, who used it to discover the pattern underlying eclipses, nearly 3,000 years ago. But it took 2,500 years and the invention of calculus and Newtonian physics to explain the patterns.

Since then, probably every single major scientific discovery has used mathematics in some form, simply because it is far more powerful than any other human language. It is not surprising that this has led many people to claim that mathematics is much more: that the universe is created by a mathematician.

So could we imagine a universe in which mathematics does not work?

The Sapir-Whorf hypothesis asserts that you cannot discuss a concept unless you have the language to describe it.

In any science, and physics in particular, we need to describe concepts that do not map well on to any human language. One can describe an electron, but the moment we start asking questions like What colour is it? we start to realize the inadequacies of English.

The colour of an object depends on the wavelengths of light reflected by it, so an electron has no colour, or more accurately, all colours. The question itself is meaningless. But ask How does an electron behave? and the answer is, in principle, simple. In 1928, Paul A.M. Dirac wrote down an equation that describes the behaviour of an electron almost perfectly under all circumstances. This does not mean it is simple when we look at the details.

For example, an electron behaves as a tiny magnet. The magnitude can be calculated, but the calculation is horrendously complicated. Explaining an aurora, for example, requires us to understand orbital mechanics, magnetic fields and atomic physics, but at heart, these are just more mathematics.

But it is when we think of the individual that we realize that a human commitment to logical, mathematical thinking goes much deeper. The decision to overtake a slow-moving car does not involve the explicit integration of the equations of motion, but we certainly do it implicitly. A Tesla on autopilot will actually solve them explicitly.

So we really should not be surprised that mathematics is not just a language for describing the external world, but in many ways the only one. But just because something can be described mathematically does not mean it can be predicted.

One of the more remarkable discoveries of the last 50 years has been the discovery of chaotic systems. These can be apparently simple mathematical systems that cannot be solved precisely. It turns out that many systems are chaotic in this sense. Hurricane tracks in the Caribbean are superficially similar to eclipse tracks, but we cannot predict them precisely with all the power of modern computers.

However, we understand why: the equations that describe weather are intrinsically chaotic, so we can make accurate predictions in the short term, (about 24 hours), but these become increasingly unreliable over days. Similarly, quantum mechanics provides a theory where we know precisely what predictions cannot be made precisely. One can calculate the properties of an electron very accurately, but we cannot predict what an individual one will do.

Hurricanes are obviously intermittent events, and we cannot predict when one will happen in advance. But the mere fact that we cannot predict an event precisely does not mean we cannot describe it when it happens. We can even handle one-off events: it is generally accepted that the universe was created in the Big Bang and we have a remarkably precise theory of that.

A whole host of social phenomena, from the stock market to revolutions, lack good predictive mathematics, but we can describe what has happened and to some extent construct model systems.

So how about personal relationships? Love may be blind, but relationships are certainly predictable. The vast majority of us choose partners inside our social class and linguistic group, so there is absolutely no doubt that is true in the statistical sense. But it is also true in the local sense. A host of dating sites make their money by algorithms that at least make some pretence at matching you to your ideal mate.

A universe that could not be described mathematically would need to be fundamentally irrational and not merely unpredictable. Just because a theory is implausible does not mean we could not describe it mathematically.

But I do not think we live in that universe, and I suspect we cannot imagine a non-mathematical universe.

This article by Peter Watson, Emeritus professor, Physics, Carleton University, is republished from The Conversation under a Creative Commons license. Read the original article.

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Why mathematics is essential to understanding our universe - The Next Web

Peter Morgan; Yale University, Department of Physics

Abstract: The connection between classical mechanics and quantum mechanics has historically been dominated by quantization and, in the opposite direction, the correspondence principle and Ehrenfest's theorem, which fall far short of the clarity of isomorphisms between mathematical structures. In contrast, we can use Koopman's Hilbert space formalism for classical mechanics to construct isomorphisms between classical and quantum Hilbert spaces and between classical and quantum algebras of operators, which allows a unified approach to joint and incompatible measurements. With a common measurement theory in place, other differences between classical and quantum can be more clearly described. At the level of field theories, signal analysis can be adopted as an empiricist way to unify QFT and random fields, which allows a carefully judged classical intuition to suggest several ways to rethink QFT.

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Math Physics Seminar - Peter Morgan | Physics and Astronomy | The University of Iowa - The University of Iowa

Abstract artists concept of neutrino particles.

Physicists are closing in on the true nature of the neutrino and might be closer to answering a fundamental question about our own existence.

In a Laboratory under a mountain, physicists are using crystals far colder than frozen air to study ghostly particles, hoping to learn secrets from the beginning of the universe. Researchers at the Cryogenic Underground Observatory for Rare Events (CUORE) announced this week that they had placed some of the most stringent limits yet on the strange possibility that the neutrino is its own antiparticle. Neutrinos are deeply unusual particles, so ethereal and so ubiquitous that they regularly pass through our bodies without us noticing. CUORE has spent the last three years patiently waiting to see evidence of a distinctive nuclear decay process, only possible if neutrinos and antineutrinos are the same particle. CUOREs new data shows that this decay doesnt happen for trillions of trillions of years, if it happens at all. CUOREs limits on the behavior of these tiny phantoms are a crucial part of the search for the next breakthrough in particle and nuclear physics and the search for our own origins.

CUORE scientists Dr. Paolo Gorla (LNGS, left) and Dr. Lucia Canonica (MIT, right) inspect the CUORE cryogenic systems. Credit: Yury Suvorov and the CUORE Collaboration

Ultimately, we are trying to understand matter creation, said Carlo Bucci, researcher at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy and the spokesperson for CUORE. Were looking for a process that violates a fundamental symmetry of nature, added Roger Huang, a postdoctoral researcher at the Department of Energys Lawrence Berkeley National Laboratory (Berkeley Lab) and one of the lead authors of the new study.

CUORE Italian for heart is among the most sensitive neutrino experiments in the world. The new results from CUORE are based on a data set ten times larger than any other high-resolution search, collected over the last three years. CUORE is operated by an international research collaboration, led by the Istituto Nazionale di Fisica Nucleare (INFN) in Italy and Berkeley Lab in the US. The CUORE detector itself is located under nearly a mile of solid rock at LNGS, a facility of the INFN. U.S. Department of Energy-supported nuclear physicists play a leading scientific and technical role in this experiment. CUOREs new results were published on April 6, 2022, in Nature.

Neutrinos are everywhere there are trillions of neutrinos passing through your thumbnail alone as you read this sentence. They are invisible to the two strongest forces in the universe, electromagnetism and the strong nuclear force, which allows them to pass right through you, the Earth, and nearly anything else without interacting. Despite their vast numbers, their enigmatic nature makes them very difficult to study, and has left physicists scratching their heads ever since they were first postulated over 90 years ago. It wasnt even known whether neutrinos had any mass at all until the late 1990s as it turns out, they do, albeit not very much.

One of the many remaining open questions about neutrinos is whether they are their own antiparticles. All particles have antiparticles, their own antimatter counterpart: electrons have antielectrons (positrons), quarks have antiquarks, and neutrons and protons (which make up the nuclei of atoms) have antineutrons and antiprotons. But unlike all of those particles, its theoretically possible for neutrinos to be their own antiparticles. Such particles that are their own antiparticles were first postulated by the Italian physicist Ettore Majorana in 1937, and are known as Majorana fermions.

CUORE detector being installed into the cryostat. Credit: Yury Suvorov and the CUORE Collaboration

If neutrinos are Majorana fermions, that could explain a deep question at the root of our own existence: why theres so much more matter than antimatter in the universe. Neutrinos and electrons are both leptons, a kind of fundamental particle. One of the fundamental laws of nature appears to be that the number of leptons is always conserved if a process creates a lepton, it must also create an anti-lepton to balance it out. Similarly, particles like protons and neutrons are known as baryons, and baryon number also appears to be conserved. Yet if baryon and lepton numbers were always conserved, then there would be exactly as much matter in the universe as antimatter and in the early universe, the matter and antimatter would have met and annihilated, and we wouldnt exist. Something must violate the exact conservation of baryons and leptons. Enter the neutrino: if neutrinos are their own antiparticles, then lepton number wouldnt have to be conserved, and our existence becomes much less mysterious.

The matter-antimatter asymmetry in the universe is still unexplained, said Huang. If neutrinos are their own antiparticles, that could help explain it.

Nor is this the only question that could be answered by a Majorana neutrino. The extreme lightness of neutrinos, about a million times lighter than the electron, has long been puzzling to particle physicists. But if neutrinos are their own antiparticles, then an existing solution known as the seesaw mechanism could explain the lightness of neutrinos in an elegant and natural way.

But determining whether neutrinos are their own antiparticles is difficult, precisely because they dont interact very often at all. Physicists best tool for looking for Majorana neutrinos is a hypothetical kind of radioactive decay called neutrinoless double beta decay. Beta decay is a fairly common form of decay in some atoms, turning a neutron in the atoms nucleus into a proton, changing the chemical element of the atom and emitting an electron and an anti-neutrino in the process. Double beta decay is more rare: instead of one neutron turning into a proton, two of them do, emitting two electrons and two anti-neutrinos in the process. But if the neutrino is a Majorana fermion, then theoretically, that would allow a single virtual neutrino, acting as its own antiparticle, to take the place of both anti-neutrinos in double beta decay. Only the two electrons would make it out of the atomic nucleus. Neutrinoless double-beta decay has been theorized for decades, but its never been seen.

The CUORE experiment has gone to great lengths to catch tellurium atoms in the act of this decay. The experiment uses nearly a thousand highly pure crystals of tellurium oxide, collectively weighing over 700 kg. This much tellurium is necessary because on average, it takes billions of times longer than the current age of the universe for a single unstable atom of tellurium to undergo ordinary double beta decay. But there are trillions of trillions of atoms of tellurium in each one of the crystals CUORE uses, meaning that ordinary double beta decay happens fairly regularly in the detector, around a few times a day in each crystal. Neutrinoless double beta decay, if it happens at all, is even more rare, and thus the CUORE team must work hard to remove as many sources of background radiation as possible. To shield the detector from cosmic rays, the entire system is located underneath the mountain of Gran Sasso, the largest mountain on the Italian peninsula. Further shielding is provided by several tons of lead. But freshly mined lead is slightly radioactive due to contamination by uranium and other elements, with that radioactivity decreasing over time so the lead used to surround the most sensitive part of CUORE is mostly lead recovered from a sunken ancient Roman ship, nearly 2000 years old.

Perhaps the most impressive piece of machinery used at CUORE is the cryostat, which keeps the detector cold. To detect neutrinoless double beta decay, the temperature of each crystal in the CUORE detector is carefully monitored with sensors capable of detecting a change in temperature as small as one ten-thousandth of a Celsius degree. Neutrinoless double beta decay has a specific energy signature and would raise the temperature of a single crystal by a well-defined and recognizable amount. But in order to maintain that sensitivity, the detector must be kept very cold specifically, its kept around 10 mK, a hundredth of a degree above absolute zero. This is the coldest cubic meter in the known universe, said Laura Marini, a research fellow at Gran Sasso Science Institute and CUOREs Run Coordinator. The resulting sensitivity of the detector is truly phenomenal. When there were large earthquakes in Chile and New Zealand, we actually saw glimpses of it in our detector, said Marini. We can also see waves crashing on the seashore on the Adriatic Sea, 60 kilometers away. That signal gets bigger in the winter, when there are storms.

Despite that phenomenal sensitivity, CUORE hasnt yet seen evidence of neutrinoless double beta decay. Instead, CUORE has established that, on average, this decay happens in a single tellurium atom no more often than once every 22 trillion trillion years. Neutrinoless double beta decay, if observed, will be the rarest process ever observed in nature, with a half-life more than a million billion times longer than the age of the universe, said Danielle Speller, Assistant Professor at Johns Hopkins University and a member of the CUORE Physics Board. CUORE may not be sensitive enough to detect this decay even if it does occur, but its important to check. Sometimes physics yields surprising results, and thats when we learn the most. Even if CUORE doesnt find evidence of neutrinoless double-beta decay, it is paving the way for the next generation of experiments. CUOREs successor, the CUORE Upgrade with Particle Identification (CUPID) is already in the works. CUPID will be over 10 times more sensitive than CUORE, potentially allowing it to glimpse evidence of a Majorana neutrino.

But regardless of anything else, CUORE is a scientific and technological triumph not only for its new bounds on the rate of neutrinoless double beta decay, but also for its demonstration of its cryostat technology. Its the largest refrigerator of its kind in the world, said Paolo Gorla, a staff scientist at LNGS and CUOREs Technical Coordinator. And its been kept at 10 mK continuously for about three years now. Such technology has applications well beyond fundamental particle physics. Specifically, it may find use in quantum computing, where keeping large amounts of machinery cold enough and shielded from environmental radiation to manipulate on a quantum level is one of the major engineering challenges in the field.

Meanwhile, CUORE isnt done yet. Well be operating until 2024, said Bucci. Im excited to see what we find.

Reference: Search for Majorana neutrinos exploiting millikelvin cryogenics with CUORE by The CUORE Collaboration, 6 April 2022, Nature.DOI: 10.1038/s41586-022-04497-4

CUORE is supported by the U.S. Department of Energy, Italys National Institute of Nuclear Physics (Instituto Nazionale di Fisica Nucleare, or INFN), and the National Science Foundation (NSF). CUORE collaboration members include: INFN, University of Bologna, University of Genoa, University of Milano-Bicocca, and Sapienza University in Italy; California Polytechnic State University, San Luis Obispo; Berkeley Lab; Johns Hopkins University; Lawrence Livermore National Laboratory; Massachusetts Institute of Technology; University of California, Berkeley; University of California, Los Angeles; University of South Carolina; Virginia Polytechnic Institute and State University; and Yale University in the US; Saclay Nuclear Research Center (CEA) and the Irne Joliot-Curie Laboratory (CNRS/IN2P3, Paris Saclay University) in France; and Fudan University and Shanghai Jiao Tong University in China.

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Physicists Are Closing In on the Next Breakthrough in Particle Physics And the Search for Our Own Origins - SciTechDaily

An ultraprecise measurement of the mass of a subatomic particle called the W boson may diverge from the Standard Model, a long-reigning framework that governs the strange world of quantum physics.

After 10 years of collaboration using an atom smasher at Fermilab in Illinois, scientists announced this new measurement, which is so precise that they likened it to finding the weight of an 800-pound (363 kilograms) gorilla to a precision of 1.5 ounces (42.5 grams). Their result puts the W boson, a carrier of the weak nuclear force, at a mass seven standard deviations higher than the Standard Model predicts. That's a very high level of certainty, representing only an incredibly small probability that this result occurred by pure chance.

"While this is an intriguing result, the measurement needs to be confirmed by another experiment before it can be interpreted fully," Joe Lykken, Fermilab's deputy director of research, said in a statement (opens in new tab).

The new result also disagrees with older experimental measurements of the W boson's mass. It remains to be seen if this measurement is an experimental fluke or the first opening of a crack in the Standard Model. If the result does stand up to scrutiny and can be replicated, it could mean that we need to revise or extend the Standard Model with possibly new particles and forces.

Related: Physicists get closer than ever to measuring the elusive neutrino

The weak nuclear force is perhaps the strangest of the four fundamental forces of nature. It's propagated by three force carriers, known as bosons. There is the single Z boson, which has a neutral electric charge, and the W+ and W- bosons, which have positive and negative electric charges, respectively.

Because those three bosons have mass, they travel more slowly than the speed of light and eventually decay into other particles, giving the weak nuclear force a relatively limited range. Despite those limitations, the weak force is responsible for radioactive decay, and it is the only force (besides gravity) to interact directly with neutrinos, the mysterious, ghost-like particles that flood the universe.

Pinning down the masses of the weak force carriers is a crucial test of the Standard Model, the theory of physics that combines quantum mechanics, special relativity and symmetries of nature to explain and predict the behavior of the electromagnetic, strong nuclear and weak nuclear forces. (Yes, gravity is the "elephant in the room" that the model cannot explain.) The Standard Model is the most accurate theory ever developed in physics, and one of its crowning achievements was the successful prediction of the existence of the Higgs boson, a particle whose quantum mechanical field gives rise to mass in many other particles, including the W boson.

According to the Standard Model, at high energies the electromagnetic and weak nuclear forces combine into a single, unified force called the electroweak interaction. But at low energies (or the typical energies of everyday life), the Higgs boson butts in, driving a wedge between the two forces. Through that same process, the Higgs also gives mass to the weak force carriers.

If you know the mass of the Higgs boson, then you can calculate the mass of the W boson, and vice versa. For the Standard Model to be a coherent theory of subatomic physics, it must be consistent with itself. If you measure the Higgs boson and use that measurement to predict the W boson's mass, it should agree with an independent, direct measurement of the W boson's mass.

Using the Collider Detector at Fermilab (CDF), which is inside the giant Tevatron particle accelerator, a collaboration of more than 400 scientists examined years of data from over 4 million independent collisions of protons with antiprotons to study the mass of the W boson. During those super-energetic collisions, the W boson decays into either a muon or an electron (along with a neutrino). The energies of those emitted particles are directly connected to the underlying mass of the W boson.

"The number of improvements and extra checking that went into our result is enormous," said Ashutosh V. Kotwal, a particle physicist at Duke University who led the analysis. "We took into account our improved understanding of our particle detector as well as advances in the theoretical and experimental understanding of the W boson's interactions with other particles. When we finally unveiled the result, we found that it differed from the Standard Model prediction."

The CDF collaboration measured the value of the W boson to be 80,433 9 MeV/c2, which is about 80 times heavier than the proton and about 0.1% heavier than expected. The uncertainty in the measurement comes from both statistical uncertainty (just like the uncertainty you get from taking a poll in an election) and systematic uncertainty (which is produced when your experimental apparatus doesn't always behave in the way you designed it to act). Achieving that level of precision of an astounding 0.01% is itself an enormous task, like knowing your own weight down to less than a quarter of an ounce.

"Many collider experiments have produced measurements of the W boson mass over the last 40 years," CDF co-spokesperson Giorgio Chiarelli, a research director at the Italian National Institute for Nuclear Physics, said in the statement. "These are challenging, complicated measurements, and they have achieved ever more precision. It took us many years to go through all the details and the needed checks."

The result differed from the Standard Model prediction of the W boson's mass, which is 80,357 6 MeV/c2. The uncertainties in that calculation (the "") come from uncertainties in the measurement of the Higgs boson and other particles, which must be inserted into the calculation, and from the calculation itself, which relies on several approximation techniques.

The differences between the results aren't very large in an absolute sense. Because of the high precision, however, they are separated by seven standard deviations, indicating the presence of a major discrepancy.

The new result also disagrees with previous measurements from other collider experiments, which have been largely consistent with the Standard Model prediction. It's not clear yet if this result is caused by some unknown bias within the experiment or if it's the first sign of new physics.

If the CDF result holds up and other experiments can verify it, it could be a sign that there's more to the W boson mass than its interaction with the Higgs. Perhaps a previously unknown particle or field, or maybe even dark matter, is interacting with the W boson in a way the Standard Model currently doesn't predict.

Nonetheless, the result is an important step in testing the accuracy of the Standard Model, said CDF co-spokesperson David Toback, a professor of physics and astronomy at Texas A&M University. "It's now up to the theoretical physics community and other experiments to follow up on this and shed light on this mystery," he said.

The researchers described their results April 7 in the journal Science (opens in new tab).

Originally published on Live Science.

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Oddly heavy particle may have just broken the reigning model of particle physics - Livescience.com