higgs boson – Polkinghorne http://polkinghorne.org/ Fri, 11 Mar 2022 06:23:39 +0000 en-US hourly 1 https://wordpress.org/?v=5.9.3 https://polkinghorne.org/wp-content/uploads/2022/01/icon-2022-01-25T202759.511-150x150.png higgs boson – Polkinghorne http://polkinghorne.org/ 32 32 Lancaster receives £2.9m for particle physics research https://polkinghorne.org/lancaster-receives-2-9m-for-particle-physics-research/ Thu, 10 Mar 2022 13:14:00 +0000 https://polkinghorne.org/lancaster-receives-2-9m-for-particle-physics-research/ Lancaster University has received £2.9 million from the Science and Technology Facilities Council (STFC) as part of its ongoing support for the particle physics research community in the UK. This funding helps keep the UK at the forefront of answering some of the most important and complex scientific questions and supports the next generation of […]]]>

Lancaster University has received £2.9 million from the Science and Technology Facilities Council (STFC) as part of its ongoing support for the particle physics research community in the UK.

This funding helps keep the UK at the forefront of answering some of the most important and complex scientific questions and supports the next generation of UK particle physicists.

The funding will allow the Experimental Particle Physics Group at Lancaster to continue its world-class research to study phenomena in particle physics with a focus on determining the dominance of matter over antimatter in the Universe, precise measurements of the best current theoretical description of particle physics. (the “standard model”) as well as theories that go beyond this theory.

The program uses facilities around the world including CERN (Switzerland/France), Fermilab (USA), JPARC (Japan) and SNOLab (Canada) and the group participates in and leads many activities at CERN (ATLAS and NA62 ) and neutrino ( DUNE, T2K, HK, MicroBooNE, SBND).

Professor Roger Jones of Lancaster University said: “At a time of very tight budgets, we are pleased to have increased our grant support and will be able to continue a broad and exciting program addressing the fundamental questions of particle physics.

Particle physics studies the world at the smallest possible distance scales and at the highest attainable energies, seeking answers to fundamental questions about the structure of matter and the composition of the Universe.

Ten years after British researchers contributed to the Nobel Prize-winning detection of the Higgs boson, some of the questions the community is struggling to answer include:

  • What is the Universe made of and why?
  • What is the underlying nature of neutrinos?
  • Why is there an imbalance between matter and antimatter in the Universe?
  • How to detect dark matter?
  • Are there any new particles or particle interactions we can find?

Professor Grahame Blair, Executive Director of Programs at STFC, said:

“The STFC continues to support the experimental particle physics community in the UK by answering fundamental questions about our Universe.

“Grants are essential to support technicians, engineers and academics in their skills and expertise in the field, while encouraging career development in basic research with universities and international collaborators.

“This investment supports the UK physics community and enables the UK to continue to lead the field of experimental particle physics.”

/Public release. This material from the original organization/authors may be ad hoc in nature, edited for clarity, style and length. The views and opinions expressed are those of the author or authors. See in full here.

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Some thoughts on the Standard Model of Particle Physics – Kashmir Reader https://polkinghorne.org/some-thoughts-on-the-standard-model-of-particle-physics-kashmir-reader/ Sat, 05 Feb 2022 19:58:00 +0000 https://polkinghorne.org/some-thoughts-on-the-standard-model-of-particle-physics-kashmir-reader/ It doesn’t answer the most fundamental mystery: what constitutes the dark energy and dark matter that make up the majority of our universe? The Standard Model became the fundamental model of elementary particle physics in the second half of the 20th century. It is considered today as the best description of the constituent elements of […]]]>

It doesn’t answer the most fundamental mystery: what constitutes the dark energy and dark matter that make up the majority of our universe?

The Standard Model became the fundamental model of elementary particle physics in the second half of the 20th century. It is considered today as the best description of the constituent elements of the universe. It explains how quarks (which form protons and neutrons) and leptons (electrons, etc.) make up all known matter. It is also an explanation of how quarks and leptons are influenced by the exchange of intermediate force carriers. It describes three of the four fundamental interactions that sum up the structure of matter up to the measurement of 10 high at -18 meter. It is in short a quantum theory of three basic theories of electromagnetic interaction, strong interaction and weak interaction. The development of the Standard Model has been led by a large number of experimental and theoretical physicists alike. The structure or mathematical framework of the Standard Model is provided by quantum field theory
According to the standard model, all matter is made up of three types of elementary particles: leptons, quarks and their mediators. There are six leptons divided into three generations. There are also six anti-leptons, so the total number of leptons is 12. Similarly, the number of quarks is six, each of which comes in three colors (this color bears no resemblance to the concept of color in our daily life), which represents 36 quarks in total, including the antiquarks. Quarks like leptons have three generations. Finally, for each interaction, we have a mediator. The carrier of the electromagnetic interaction is a massless photon while the carriers of the weak interaction are called intermediate vector bosons, which are two charged Ws and a neutral heavy Z. Finally, for the strong interaction exchange, we have 8 gluons.
The missing link of the Standard Model, the Higgs boson theoretically predicted by Peter Higgs in the early 1960s, which explains the mass of elementary particles via the Higgs mechanism, involving chiral symmetry breaking, was discovered in 2012 at Large Hadron Collider in Geneva, Switzerland. The marvelous achievement of the Standard Model can be measured by the simple fact that it has led to more than 50 Nobel Prizes in Physics so far.
Loopholes:
Even though the Standard Model is currently the best description we have of the subatomic world, but despite its robust predictions, there is a consensus among physicists that the Standard Model is neither complete nor the final theory. “There is a certain degree of ugliness in the standard model,” says Steve Weinberg, one of its main architects. First, the standard model is completely silent about dark energy and dark matter. This does not answer the question of what constitutes the dark energy and dark matter that make up the majority of matter in our universe. Second, it fails to explain neutrino oscillations and, more importantly, it fails to incorporate one of the most fundamental interactions, gravity, which explains the large-scale structure of the universe. At a more fundamental level, he fails to explain why there are precisely three generations of quarks and leptons. Likewise, the difference in masses of the elementary particles that they acquire due to their interaction with the Higgs field via the Higgs boson remains a mystery.
Possible output:
In order to accommodate many of the shortcomings of the Standard Model listed above, physicists over time have come up with different theories and approaches. All of these theories and approaches fall under the category “Physics Beyond the Standard Model”. Theories that lie beyond the Standard Model include the various extensions of supersymmetry and entirely new explanations and theories such as string theory, looping quantum gravity, and extra dimensions. But the theory that has gained most prominence among them is string theory. String theory has captured the imagination of a generation of particle physicists over the past 40 years. String theory not only promises the reconciliation of quantum mechanics with Einstein’s general relativity and eliminates the infinities that plague quantum field theory, it also provides a unified theory of everything from which all elementary particle physics , including gravity, would emerge as an inevitable consequence. But the bottleneck of particle physics, as string theorist and Nobel laureate David Gross puts it, is experimental, not theoretical, so in the absence of experimental evidence to back up his predictions, the future of string theory seems grim, or at least you have to cross your fingers. If string theory lives up to expectations, which seems unlikely, it will be the ultimate triumph of the human spirit.

—The author is a physics student
[email protected]





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The Absolutely Incredible Theory of Almost Everything https://polkinghorne.org/the-absolutely-incredible-theory-of-almost-everything/ Sat, 15 Jan 2022 08:00:00 +0000 https://polkinghorne.org/the-absolutely-incredible-theory-of-almost-everything/ How does our world work at the subatomic level? The standard model. What a boring name for the most accurate scientific theory known to human beings. More than a quarter of the Nobel Prizes in Physics of the last century are direct inputs or direct results of the Standard Model. Still, its name suggests that […]]]>

How does our world work at the subatomic level?

The standard model. What a boring name for the most accurate scientific theory known to human beings.

More than a quarter of the Nobel Prizes in Physics of the last century are direct inputs or direct results of the Standard Model. Still, its name suggests that if you can afford a few extra bucks a month, you should buy the upgrade. As a theoretical physicist, I would prefer The Absolutely Incredible Theory of almost anything. That’s what the standard model really is.

Many remember the enthusiasm of scientists and the media over the 2012 discovery of the Higgs boson. But this high-profile event didn’t come out of nowhere — it capped a five-decade unbeaten streak for the standard model. All fundamental forces except gravity are included. All attempts to overthrow it to demonstrate in the laboratory that it needs substantial reworking – and there have been many over the past 50 years – have failed.

In short, the standard model answers this question: what is it all made of and how does it fit together?

The smallest building blocks

You know, of course, that the world around us is made of molecules, and molecules are made of atoms. Chemist Dmitri Mendeleev discovered in the 1860s how to arrange all of the atoms – aka the elements – in the periodic table that you probably studied in college. But there are 118 different chemical elements. There’s antimony, arsenic, aluminum, selenium… and 114 others.

Periodic table

But these elements can be broken down further. Credit: Ruben Vera Koster

Physicists like simple things. We want to boil things down to their essence, a few basics. More than a hundred chemical elements is not simple. The ancients believed that everything was made up of only five elements: earth, water, fire, air and ether. Five is much simpler than 118. It’s also wrong.

In 1932, scientists knew that all these atoms were made up of only three particles: neutrons, protons and electrons. Neutrons and protons are tightly bound in the nucleus. Electrons, thousands of times lighter, whirl around the nucleus at speeds close to the speed of light. The physicists Planck, Bohr, Schroedinger, Heisenberg and their friends had invented a new science – quantum mechanics – to explain this movement.

It would have been a satisfying place to stop. Just three particles. Three is even easier than five. But how to hold together? Negatively charged electrons and positively charged protons are bound by electromagnetism. But the protons are all packed into the nucleus, and their positive charges should powerfully push them away. Neutrons can’t help.

What binds these protons and these neutrons? “Divine intervention” a man told me on a Toronto street corner; he had a pamphlet, I could read all about it. But this scenario seemed to pose a lot of problems, even for a divine being – to keep an eye on every one of the 108° protons and neutrons in the universe and bend them to his will.

Expand the Particle Zoo

Meanwhile, nature has cruelly refused to limit its particle zoo to just three. Really four, because you would have to count the photon, the particle of light described by Einstein. Four changed to five when Anderson measured electrons with a positive charge – positrons – hitting Earth from space. At least Dirac had predicted these first antimatter particles. Five became six when the pawn, which Yukawa believed would hold the core together, was found.

Then came the muon – 200 times heavier than the electron, but otherwise a twin. “Who ordered this? II Rabi joked. That sums it all up. Number seven. Not only not simple, redundant.

In the 1960s, there were hundreds of “fundamental” particles. Instead of the neatly organized periodic table, there were only long lists of baryons (heavy particles like protons and neutrons), mesons (like Yukawa pions) and leptons (light particles like the electron and the elusive neutrinos) – with no organization and no guiding principles.

Into this breach has slipped the standard model. It wasn’t an overnight flash of brilliance. No Archimedes jumped out of a bathtub shouting “eureka”. Instead, there was a series of crucial ideas from a few key people in the mid-1960s that turned this quagmire into a simple theory, and then five decades of experimental verification and theoretical elaboration.

Standard model of elementary particles

The standard model of elementary particles provides a list of ingredients for everything around us. Credit: National Fermi Accelerator Laboratory

Quarks. They come in six varieties which we call flavors. Like ice cream, except it’s not as tasty. Instead of vanilla, chocolate and so on, we have high, low, weird, charm, low and high. In 1964, Gell-Mann and Zweig taught us the recipes: mix and match three quarks to get a baryon. Protons are two ups and one down quark bound together; neutrons are two lows and one high. Choose a quark and an antiquark to get a meson. A pion is an up or down quark bound to an anti-up or an anti-down. All the material of our daily life is composed only of quarks, anti-quarks and electrons.

Simple. Well, it’s simple, because keeping those quarks bound is a feat. They are so closely related to each other that you never find a single quark or antiquark. The theory of this binding, and the particles called gluons (laughs) that are responsible for it, is called quantum chromodynamics. It is an essential piece of the standard model, but mathematically difficult, even posing an unsolved problem of basic mathematics. We physicists do our best to calculate with it, but we are still learning how.

The other aspect of the standard model is “a lepton model”. It’s the name of Steven Weinberg’s landmark 1967 paper that brought together quantum mechanics with the essential knowledge of how particles interact and organized the two into a single theory. He incorporated the familiar electromagnetism, associated it with what physicists called “the weak force” that causes certain radioactive decays, and explained that they were different aspects of the same force. It incorporated the Higgs mechanism to give mass to fundamental particles.

Since then, the Standard Model has predicted the results of experiment after experiment, including the discovery of several varieties of quarks and W and Z bosons, heavy particles that are to weak interactions what the photon is to electromagnetism. The possibility that neutrinos are not massless was overlooked in the 1960s, but slipped easily into the Standard Model in the 1990s, a few decades later.

CERN particle accelerator Higgs boson decay SM

3D view of an event recorded at the CERN particle accelerator showing the expected characteristics of the decay of the SM Higgs boson into a pair of photons (dashed yellow lines and green towers). Credit: McCauley, Thomas; Taylor, Lucas; for the CMS CERN collaboration

Discovering the Higgs boson in 2012, long predicted by the Standard Model and long sought after, was a thrill but not a surprise. It was yet another crucial victory for the Standard Model over the dark forces that particle physicists have repeatedly warned were looming on the horizon. Concerned that the Standard Model did not adequately embody their expectations of simplicity, worried about its mathematical consistency, or anticipating the possible need to incorporate the force of gravity, physicists made numerous proposals for theories beyond of the norm. Model. These go by exciting names like Grand Unified Theories, Supersymmetry, Technicolor, and String Theory.

Unfortunately, at least for their proponents, theories beyond the Standard Model have not yet successfully predicted a new experimental phenomenon or an experimental divergence from the Standard Model.

After five decades, far from needing an upgrade, the Standard Model deserves to be celebrated as an absolutely incredible theory of almost everything.

Written by Glenn Starkman, Distinguished University Professor of Physics, Case Western Reserve University.

This article first appeared in The Conversation.The conversation

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Wobbling in the history of particle physics – now. Powered by Northrop Grumman https://polkinghorne.org/wobbling-in-the-history-of-particle-physics-now-powered-by-northrop-grumman/ Mon, 18 Oct 2021 07:00:00 +0000 https://polkinghorne.org/wobbling-in-the-history-of-particle-physics-now-powered-by-northrop-grumman/ Particle physics is the quest to discover the fundamental components of the universe by analyzing, cataloging and measuring the particles that combine to create everything. It’s no easy task – the variety and variability of these physical firmaments makes them an ever-changing puzzle that can seem completely impenetrable until a new secret is unlocked. Now, […]]]>

Particle physics is the quest to discover the fundamental components of the universe by analyzing, cataloging and measuring the particles that combine to create everything. It’s no easy task – the variety and variability of these physical firmaments makes them an ever-changing puzzle that can seem completely impenetrable until a new secret is unlocked.

Now, new research on the muon – a small electron-like particle 200 times heavier than its negatively charged cousin – could pave the way for the particle’s next pivot: oscillations.

Standard operation procedure

To help make sense of the universe and how it works, scientists created the Standard Model. It was not an easy task either. As SciTechDaily notes, while the electron was discovered in 1897, the last element in the current framework – the Higgs boson – wasn’t confirmed until 2012.

The model makes it possible to reconcile three of the four fundamental forces: electromagnetism, the strong nuclear force and the weak nuclear force. It also highlights the role of quarks and leptons as the building blocks of all matter, including the familiar trio of protons, neutrons and electrons. Work on the Standard Model has shown that photons play a role in the transport of electromagnetism, while the strong force relies on gluons to ensure the stability of atomic nuclei and the weak force exploits W and Z bosons. to drive the powerful nuclear processes that keep stars burning for billions of years. year.

However, despite its usefulness, the standard model has a blind spot: gravity. While the model does an excellent job of describing which particles underlie the other three fundamental forces, gravity is conspicuously absent. This is because scientists have never been able to link a specific particle to the creation and distribution of gravity. While it plays a vital role in the workings of our universe – whether it’s counteracting the expansive tendencies of nuclear reactions within our sun or keeping our feet firmly planted on planet Earth – this apparently appealing operation simple has historically resisted deep understanding.

But new muon measurements could change all that.

Crack the code

What is important to remember from scientists – and particle physicists in particular – is that they are never satisfied with the status quo. Although the Standard Model provides a starting point for understanding the universe, obvious shortcomings in the current framework mean there is still work to be done. In practice, this work involves finding new approaches to potentially breaking the model by conducting experiments, taking measurements, and then comparing the results to what the model predicts.

The challenge? For years, the model has found the right answers, much to the frustration of physicists who know something is missing. Repeated experiments using different particle approaches have produced precise measurement after precise measurement – ​​so far. Recent follow-up work on earlier muon experiments using more advanced equipment suggests a crack in the current model and raises hope that scientists may finally have found the key to a new revolution in particle physics.

Meet the muon

So what exactly is a muon? Think electron, but heavier. Much heavier – 200 times heavier, in fact. As Science Daily notes, muons and electrons “are essentially tiny magnets with their own magnetic field.” However, unlike electrons, muons are much less stable, existing only a few millionths of a second before decaying. It is also difficult to observe muons, even during their brief stay here, because the vacuum they occupy is not empty.

“It’s your cappuccino-foam version of a vacuum, where there are virtual particles appearing and disappearing all the time,” Lawrence Gibbons, who led the Cornell team involved in the new research, told Science Daily. “And that turns out to affect the strength of a muon’s magnetic field.”

Through work at CERN in 1959, followed by more precise experiments in 1966 and 1969, and then another round at Brookhaven National Laboratory in 1999, the researchers finally found something: a disconnect between the observed magnetic measurements and predicted when the muons made their way into this void. New efforts at Fermilab with more precise and advanced equipment have confirmed these findings – and could pave the way for a much more massive muon impact.

Let’s Get Physics-al

Work at CERN, Brookhaven and Fermilab all focus on the same thing: the g-2 value of the muon, which represents the amount it “wobbles” via vacuum interactions. As Jessica Esquivel, a particle physicist at Fermilab, notes, this oscillation is called the precession frequency.

“When muons enter a magnetic field, they precess or spin like a top,” she told Vox.

To measure precession, efforts at Fermilab used a powerful particle accelerator – capable of creating 20 times more muons than those previously used at CERN – to shoot an intense beam of muons into highly sensitive detectors, which measured their precession frequency. As the Standard Model predicts, this precession occurs when muons collide with virtual particles, which Esquivel describes as “a kind of ghosting of real particles.”

“We have photons going in and out and they’re just kind of like there, but not really there,” she told Vox. However, despite this recurring strangeness, these virtual particles have a physical impact on muon oscillations.

But this is where it gets really weird: Experiments at Fermilab confirm that muons flicker more than they should, according to the Standard Model. Even more exciting? Scientists don’t know why.

Stumbling our way forward

The lack of certainty here is what makes these experimental results so interesting. According to the Standard Model, g-2 muon values ​​are explainable using actual particle interactions and should produce predictable results. However, Fermilab’s efforts suggest that something else is causing this additional oscillation – something outside the current functional framework, as Esquivel and his colleagues told Vox.

And while there have been discussions about this “breaking” of the Standard Model before, it’s more about filling in the details where the data was clearly missing. Esquivel likens it to adding elements to the periodic table.

“Even back then,” she tells Vox, “they had places where they knew an item had to go, but they hadn’t been able to see it yet. That’s basically where we are now. In practice, this movement of muons opens the door to a multitude of potential operations on the particles.This unexpected oscillation could be caused by an interaction with dark matter or long-predicted dark energy particles, or it could help establish a particle-based link with the peripheral fourth fundamental gravitational force.

Esquivel simply explains the impact of this measurement of movement: “It’s once in a lifetime. We are looking for new physics and we are so close that we can taste it. A meal of muons, an extra oscillation – it happens!

Being at the forefront of change, especially in space, physics and engineering, has been part of the Northrop Grumman culture for generations. Click here to search for jobs in these areas of scientific innovation.

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Nobel Prize in Particle Physics Steven Weinberg ’54 Dies at 88 https://polkinghorne.org/nobel-prize-in-particle-physics-steven-weinberg-54-dies-at-88/ Tue, 24 Aug 2021 07:00:00 +0000 https://polkinghorne.org/nobel-prize-in-particle-physics-steven-weinberg-54-dies-at-88/ Steven Weinberg ’54, the theoretical physicist whose Nobel Prize-winning work transformed scientists’ understanding of fundamental forces, died on July 23. He was 88 years old. “[His work] is basically the foundation of everything we do in particle physics, what we now call the Standard Model,” said physicist Professor Csaba Csaki. The Standard Model explains the […]]]>

Steven Weinberg ’54, the theoretical physicist whose Nobel Prize-winning work transformed scientists’ understanding of fundamental forces, died on July 23. He was 88 years old.

“[His work] is basically the foundation of everything we do in particle physics, what we now call the Standard Model,” said physicist Professor Csaba Csaki. The Standard Model explains the fundamental particles and interactions that make up the universe.

In his most significant work, the former Cornell student and former guest speaker proposed the electroweak force, which unifies the electromagnetic and weak forces, two of the fundamental forces that explain the behavior of all particles in the universe.

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Steven Weinberg obituary | Particle physics https://polkinghorne.org/steven-weinberg-obituary-particle-physics/ Mon, 02 Aug 2021 07:00:00 +0000 https://polkinghorne.org/steven-weinberg-obituary-particle-physics/ The American theoretical particle physicist Steven Weinberg, who died at the age of 88, was one of the leading figures of the 20th century in this field. In 1979, he won a Nobel Prize for his work uniting two of nature’s fundamental forces, which became a foundation of the Standard Model of particle physics, the […]]]>

The American theoretical particle physicist Steven Weinberg, who died at the age of 88, was one of the leading figures of the 20th century in this field. In 1979, he won a Nobel Prize for his work uniting two of nature’s fundamental forces, which became a foundation of the Standard Model of particle physics, the theory that describes all known particles and fundamental forces in the universe. .

From Weinberg’s prodigious work – in research, in his technical and popular books on quantum field theory and cosmology, and in scientific commentary articles – his work demonstrating that the transmutation of elements by the weak nuclear force is fundamentally related to electromagnetism constituted a truly remarkable breakthrough.

Following Peter Higgs’ discovery in 1964 that fundamental particles can, in theory, gain mass through the “Higgs mechanism”, he, Weinberg and others tried to find examples where this mechanism is used in the nature. These attempts initially focused on the strong force that binds atomic nuclei, but no consistent correspondence emerged, until 1967, while on his way to work at MIT (the Massachusetts Institute of Technology), Weinberg had an inspired thought: they had implemented the right idea. , but to the wrong problem.

Instead of the strong force, Weinberg realized that the mechanism could apply to the weak nuclear force, manifested by radioactivity. As a bonus, Weinberg realized that thanks to this application, he could describe in a single mathematical diagram both the phenomena of electromagnetism and the form of radioactivity which is the key to the creation of elements in stars. This idea would become the basis of the current standard model of particles and forces.

A viable quantum field theory of electromagnetism – quantum electrodynamics (QED) – had been known since 1947. The key to its consistency was that the photon – the basic particle of electromagnetic radiation – is massless. Weinberg’s marriage of weak and electromagnetic forces required the existence of analogues of the photon. These “W and Z bosons” were later discovered and confirmed to be very massive, as Weinberg had predicted.

There was a problem, however: being massive, they apparently undermined the mathematical coherence of the theory. Weinberg conjectured, but was unable to prove, that if the W and Z gained their masses through the Higgs mechanism, his extension of QED would indeed be a viable quantum theory of two forces.

Initially his paper had little impact, with one prominent scientist later describing the response: “Rarely has such a great achievement been so widely ignored.” Then, in 1971, a young Dutch student, Gerard ‘t Hooft, proved the model to be a complete and viable theory, winning himself a Nobel Prize in 1999 for this feat.

With the demonstration that Weinberg had indeed constructed a coherent relativistic quantum theory of electromagnetic and weak force fields, the predictions of which were soon confirmed in a variety of experiments, his seminal paper quickly became the most cited in all of theoretical physics. Its implications were so profound that they determined the direction of high-energy particle physics during the last decades of the 20th century. In what was to prove to be of momentous importance, his papers drew attention to a cornerstone of his theoretical construction – the necessary role of the ‘Higgs boson’. The search for this particle would take four decades; its discovery in 2012 was the final piece in a structure whose architectural design owed much to the genius of Weinberg.

Born in New York, Steven was the son of Jewish immigrants, Eva (née Israel) and Frederick Weinberg, a court stenographer. Steven’s love for science began in childhood with the gift of a chemistry set. He attended Bronx Science High School, which produced eight Nobel laureates, including Weinberg’s contemporary Sheldon Glashow, whose freelance work led him to share the 1979 prize with Weinberg and Abdus Salam. He earned a bachelor’s degree at Cornell University in 1954, and that year married Louise Goldwasser, whom he had met while a student; she became a law professor. After a year at what is now the Niels Bohr Institute in Copenhagen, Weinberg returned to the United States and Princeton University, where he earned a doctorate (1957).

After two years at Columbia University and six at Berkeley, in 1966 Weinberg joined Harvard University, first as a lecturer, and from 1973 as a professor of physics. Early in his Harvard stint, Weinberg had a joint appointment at MIT, and it was while driving there in his red Camarro that he had his weak nuclear force epiphany.

In 1982 he moved to the University of Texas at Austin, where he spent the rest of his career. He never retired and continued teaching until the spring of that year.

For decades, Weinberg’s ideas outside of his 1967 paper inspired new lines of research. His work on “effective field theories” redefined the direction of work in quantum field theory and influenced attempts to find a viable quantum theory of gravity. He was one of the founders of the concept of “chiral perturbation theory” as a mathematical approach to understanding aspects of the strong nuclear force.

In addition to these seminal research contributions, Weinberg wrote an influential text on gravitation, a masterful three-volume set of textbooks on quantum field theory, and authored the popular best-selling cosmology book The First Three Minutes (1977).

In 1992 he published Dreams of a Final Theory, which has become a classic discourse on the goal of fundamental physics at the dawn of the 21st century.

In his later years he became an authoritative historian of science, his gravity and wisdom making him a respected commentator on science policy as well as social issues, and making him one of the most respected figures in science. world.

He is survived by his wife, Louise, whom he married in 1954, their daughter, Elizabeth, and one granddaughter.

Steven Weinberg, theoretical physicist, born May 3, 1933; passed away on July 23, 2021

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Argonne aurora will accelerate particle physics discoveries at CERN https://polkinghorne.org/argonne-aurora-will-accelerate-particle-physics-discoveries-at-cern/ Thu, 22 Jul 2021 07:00:00 +0000 https://polkinghorne.org/argonne-aurora-will-accelerate-particle-physics-discoveries-at-cern/ July 22, 2021 – The U.S. Department of Energy’s (DOE) Argonne National Laboratory will house one of the nation’s first exascale supercomputers when Aurora arrives in 2022. To prepare code for the architecture and System-wide, 15 research teams are taking part in the Aurora Early Science program through the Argonne Leadership Computing Facility (ALCF), a […]]]>

July 22, 2021 – The U.S. Department of Energy’s (DOE) Argonne National Laboratory will house one of the nation’s first exascale supercomputers when Aurora arrives in 2022. To prepare code for the architecture and System-wide, 15 research teams are taking part in the Aurora Early Science program through the Argonne Leadership Computing Facility (ALCF), a DOE Office of Science user facility. With access to pre-production time on the supercomputer, these researchers will be among the first in the world to use an exascale machine for science.

Early philosophers first formulated the idea of ​​the atom around the fifth century BCE. And just when we thought we had understood its basic structure – protons, neutrons and electrons – theories and technologies emerged to prove us wrong. It turns out that there are still more fundamental particles, like quarks, bound together by aptly named gluons.

Physicists discovered many of these and other particles in the huge beasts of machinery we call colliders, helping to develop what we know today as the Standard Model of physics. But there are questions that keep nagging: is there something even more fundamental? Is the standard model all there is?

Determined to find out, the high-energy physics community is working to integrate ever larger colliders and more sophisticated detectors with exascale computing systems. Among them is Walter Hopkins, assistant physicist at Argonne National Laboratory and collaborator on the ATLAS experiment at CERN’s Large Hadron Collider (LHC), near Geneva, Switzerland.

In collaboration with researchers from Argonne and Lawrence Berkeley National Lab, Hopkins is leading an Aurora Early Science Program project through the ALCF to prepare software used in LHC simulations for exascale computing architectures, including the upcoming exascale machine d ‘Argonne, Aurora. With a trillion calculations per second, Aurora is at the frontier of supercomputing and at the height of the next particle physics challenge of gargantuan scale.

The project was started several years ago by physicist and Argonne Emeritus James Proudfoot, who saw the distinct advantages of exascale in enhancing the impact of such complex science.

Align the codes on the new architecture

The collisions produced in the LHC occur in one of the many detectors. The one the team is focusing on, ATLAS, witnesses billions of particle interactions every second and the new particle signatures these collisions create in their wake.

One type of code the team is focusing on, called event generators, simulates the underlying physical processes that occur at interaction points in the 17-mile-circumference collider ring. Aligning the physics produced by the software with that of the Standard Model helps researchers accurately simulate collisions and predict the types, trajectories and energies of residual particles.

Detecting physics in this way creates a mountain of data and requires equally significant computational time. And now CERN is upping the ante as it prepares to upgrade the LHC’s luminosity, enabling more particle interactions and a 20-fold increase in data output.

As the team looks to Aurora to handle this increase in its simulation needs, the machine is not without some challenges.

Workers inside ATLAS, one of several primary detectors at CERN’s Large Hadron Collider. ATLAS witnesses a billion particle interactions every second and the signatures of new particles created in proton-proton collisions at near light speed. (Picture: CERN)

Until recently, event generators ran on computer processors (central processing units). Although they work fast, a processor can usually only perform several operations at a time.

Aurora will feature both CPUs and GPUs (graphics processing units), the choice of gamers around the world. GPUs can handle many operations by breaking them up into thousands of smaller tasks spread across many cores, the engines that drive both types of units.

But it takes a lot of effort to move CPU-based simulations to GPUs efficiently, Hopkins notes. So making this move to prepare for both Aurora and the onslaught of new LHC data presents several challenges, which have become a central part of the team’s goal.

“We want to be able to use Aurora to help us meet these challenges,” says Hopkins, “but that forces us to study computing architectures that are new to us and our code base. For example, we focus on a generator used in ATLAS, called MadGraph, which runs on GPUs, which are more parallel and have different memory management requirements.

A particle interaction simulation code, MadGraph, has been written by an international team of high-energy physics theorists and meets the simulation needs of the LHC.

Simulation and AI support experimental work

The LHC has played an important role in bringing the predictions to fruition. Even more famously, the Standard Model predicted the existence of the Higgs boson, which imparts mass to all fundamental particles; ATLAS and its counterpart detector, CMS, confirmed the existence of Higgs in 2012.

But, as is often the case in science, big discoveries can lead to more substantial questions, many of which are not predicted by the Standard Model. Why does the Higgs have the mass it is? What is dark matter?

“The reason for this very large LHC upgrade is that we hope to find that needle in the haystack, that we will find an anomaly in the dataset that offers a hint of physics beyond the Standard Model,” says Hopkins. .

A combination of computing power, simulation, experience, and artificial intelligence (AI) will greatly aid this research by providing accuracy in both prediction and identification.

When the ATLAS detector witnesses these particle collisions, for example, it records them as electronic signals. These are reconstructed in the form of pixels of bursts of energy which can correspond to the passage of an electron.

“But just like in AI, where the canonical example identifies cats and dogs in images, we have algorithms that identify and reconstruct those electronic signals into electrons, protons, and other things,” says Taylor Childers, computer scientist at the ALCF, member of the team. .

Data reconstructed from real crash events is then compared to simulated data to look for differences in patterns. This is where the accuracy of the physical models comes in. If they perform well and the real and simulated data do not match, you continue to measure and eliminate anomalies until it is likely that you found that needle, that something that doesn’t fit the standard pattern.

The team is also using AI to quantify uncertainty, to determine the likelihood that they have correctly identified a particle.

Humans are able to identify particles to a limited extent – several parameters like moment and position could tell us that a certain particle is an electron. But base that characterization on 10 interrelated parameters, then that’s another story altogether.

“This is where artificial intelligence really shines, especially if these input parameters are correlated, like the momentum of the particles around an electron and the momentum of the electron itself,” says Hopkins. “These correlations are hard to deal with analytically, but because we have so much simulation data, we can teach artificial intelligence and it can tell us, it’s an electron with this probability because I have all this information from Entrance. “

Exascale computing and the way forward

In preparation for Aurora, the team continues to work on programming languages ​​for new architectures and code to run on Intel hardware that will be used on Aurora, as well as hardware from other vendors.

“Part of the R&D we do with our partner Intel is to make sure the hardware does what we expect it to do and does it efficiently,” says Childers. “Having a machine like Aurora will give us lots of computing power and lots of nodes to effectively reduce solution time, especially when we move to the upgraded LHC.”

The solution is an answer to a fundamental question: is there more beyond the standard model? — and one that could have repercussions unimaginable a hundred years from now, Hopkins notes.

“Basic research can give us knowledge that can lead to societal transformation, but if we don’t do research, it won’t lead anywhere,” he says.

The ALCF is a DOE Office of Science user facility.

Funding for this project was provided by the DOE Office of Science: Offices of High Energy Physics and Advanced Scientific Computing Research. ATLAS is an international collaboration supported by the DOE.

About the ALCF

The Argonne Leadership Computing Facility provides supercomputing capabilities to the scientific and engineering community to advance fundamental discovery and understanding across a wide range of disciplines. Supported by the Advanced Scientific Computing Research (ASCR) program of the U.S. Department of Energy’s (DOE) Office of Science, the ALCF is one of two DOE advanced computing facilities dedicated to open science.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts cutting-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state, and municipal agencies to help them solve their specific problems, advance American scientific leadership, and prepare the nation for a better future. With employees in more than 60 countries, Argonne is managed by UChicago Argonne, LLC for the US Department of Energy’s Office of Science.

The U.S. Department of Energy’s Office of Science is the largest supporter of basic physical science research in the United States and works to address some of the most pressing challenges of our time. For more information, visit https://​ener​gy​.gov/​s​c​ience.

Click here to find out more.


Source: JOHN SPIZZIRRI, ALCF

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Is the Standard Model of Particle Physics really Kaput? https://polkinghorne.org/is-the-standard-model-of-particle-physics-really-kaput/ Thu, 15 Apr 2021 07:00:00 +0000 https://polkinghorne.org/is-the-standard-model-of-particle-physics-really-kaput/ Lately the internet has been flooded with stories about the Standard Model of particle physics having been broken. These stories stem from a recent experiment by physicists at Fermilab in Illinois, where a group of scientists discovered that muons “twerk.” Well, sort of. Don’t worry if you don’t know what a muon is, you’ll find […]]]>

Lately the internet has been flooded with stories about the Standard Model of particle physics having been broken.

These stories stem from a recent experiment by physicists at Fermilab in Illinois, where a group of scientists discovered that muons “twerk.” Well, sort of. Don’t worry if you don’t know what a muon is, you’ll find out in a moment, and if you don’t know what twerking is, try Googling Miley Cyrus.

Muons are electrically charged particles, which means that when placed in a magnetic field, they begin to spin. Their rotation frequency is determined by the muon’s interactions with other particles and forces – this is called its g-factor.

Just as the Earth oscillates on its axis as it spins, a muon’s axis of rotation also oscillates. Twenty years ago, scientists at Brookhaven National Laboratory first measured the g-factor and muon oscillation, and they found values ​​that did not match predictions made by the Standard Model. The Brookhaven data came in at 3 sigma, or three standard deviations.

Last week, Fermilab’s G-2 experiment, which is still ongoing, concluded that muons gliding around their magnetized ring were wobbling more than originally. The group’s conclusions reached the level of 4.2 sigma, which is very close to the magical 5 sigma which corresponds to a 1 in 3.5 million chance that the data is statistical chance. Physicists regard 5-sigma as irrefutable proof of a discovery.

The question then is, “What gives muons that extra push that makes them wobble?” One explanation is that they are pushed by virtual particles that appear and disappear due to quantum fluctuations.

Virtual particles appear in pairs – one of matter and one of antimatter. An example is an electron and its antimatter counterpart, a positron. If the muons are jostled around by virtual pairs of particles that are part of the standard model, so much the better, but what if the muons are affected by a pair of unknown virtual particles? This question is what keeps physicists awake at night.

What is the standard model?

The standard model of particle physics is the set of equations that describe the 17 known elementary particles. Elementary particles are particles that are not composed of other particles.

Prior to their discovery, the Standard Model predicted the existence and properties of W and Z bosons, the gluon, and top and charm quarks. The Standard Model also predicted the existence of the Higgs boson, which we will encounter in a minute.

The Standard Model began to take shape in 1897, when English physicist JJ Thomson discovered the electron, and it was not considered complete until 2012, when scientists at CERN’s Large Hadron Collider discovered the boson. of Higgs.

The graph below displays the particles composing the standard model. They are divided into fermions and bosons, with the 12 fermions being divided into six quarks and six antiquarks, and six leptons and antileptons.

The standard model of particle physics Source: Wikimedia Commons/Marcia Wendorf

Quarks

What sets quarks apart is that they have something called color charge, which causes them to interact via the strong force. Quarks can combine in two ways:

1. A quark and an antiquark, called meson.
2. Three quarks, called a baryon. The lightest baryons are the proton and the neutron.

Quarks also have electric charge and weak isospin, which means they can interact with each other through electromagnetism and weak interaction.

Standard model of elementary particles
Standard model of elementary particles Source: MissMJ, Cush/Wikimedia Commons

leptons

Leptons do not carry a color charge, so they do not respond to the strong force. Three of the leptons, the electron, the muon and the tau, carry an electric charge and thus interact electromagnetically with other particles. Three of the leptons, the neutrinos, carry no electrical charge, which means they only respond to the weak force. This makes them very difficult to detect.

Generations of Fermions

Just as generations of people are made up of grandparents, parents, and children, fermions also come in generations, with both members of a succeeding generation having greater mass than a previous generation.

In the table above, the first generation of quarks is made up of up and down quarks, the second generation is made up of charm and strange quarks, and the third generation is made up of top and bottom quarks.

First generation charged particles do not decay, which is a good thing since protons and neutrons are composed of at the top and down quarks, which are first-generation quarks. Second and third generation fermions decay, which means they have very short half-lives. A half-life is the time it takes for half of a sample to decay.

Last-generation fermions can only be observed in very high-energy environments, such as the Large Hadron Collider. Neutrinos invade our universe and the three generations do not decay. However, neutrinos are very difficult to detect because they almost never interact with matter.

gauge bosons

Our universe has four fundamental forces: electromagnetism, strong force, weak force and gravity. Now, for bad news, the standard model can’t account for gravity, so for now, we’ll ignore it.

The Standard Model explains the other three forces as resulting from particles exchanging other particles, the effect being that the force influences both particles. This is why gauge bosons are called force-mediator particles.

The electromagnetic force is transmitted between electrically charged particles by the photon, which has no mass. The weak force is transmitted between quarks and leptons by gauge bosons W+, W− and Z. These are massive particles, the Z boson being more massive than the W±.

Now get ready for a headache: the W± bosons act on either left-handed particles or right-handed antiparticles, while the electrically neutral Z boson interacts with both left-handed particles and antiparticles.

W± bosons carry an electric charge of +1 and -1, and they couple to the electromagnetic interaction, so when grouped with photons they collectively mediate what is called the electroweak interaction.

There are eight gluons which transmit the strong force among the six quarks. Gluons are massless, and because they themselves have a color charge, they can interact with each other.

The Higgs boson

The video of Peter Higgs, 83, taking out his handkerchief and wiping his eyes at the July 4, 2012 announcement at CERN that, finally, the Higgs boson had been discovered is truly moving. Higgs theorized the particle in 1964.

The Higgs boson generates the lepton, electron, muon and tau masses, and the quark masses. It does not generate mass for the photon and gluon, and since the Higgs boson itself is massive, that means it has to interact with itself.

Not only is the Higgs boson massive, with a mass of about 125 GeV/c2, or about 133 proton masses, but it decays almost immediately once created. This means that the Higgs can only be created and observed in a very high energy particle accelerator. Before it was observed at CERN, scientists at Fermilab were looking for the Higgs.

A year after the discovery of the Higgs boson, in 2013, Peter Higgs is finally honored with a Nobel Prize in Physics, alongside François Englert. On the day of the announcement, Higgs wanted to avoid media attention, so he walked out. He didn’t own a cell phone, so he only found out he had won the Nobel Prize when he met a neighbor.

Is the standard model really outdated?

Just last month, new scientist reported that Large Hadron Collider scientists found a deviation from the predicted rates at which particles containing the bottom quark decay into an electron and a muon. While the production of electrons and muons should be equal, this is not the case.

Other problems not explained by the standard model include:

  • Does the Higgs boson also give mass to neutrinos?
  • About 95% of the universe is not made of ordinary matter but consists of dark energy and dark matter that does not fit into the Standard Model.
  • The gluons that transmit the force of gravity have never been found.
  • Baryon asymmetry.
  • Neutrino oscillations and nonzero masses.
  • Why is the universe expanding faster and faster?
  • Why is the universe made up of more matter than antimatter?

The next two years will determine whether the Standard Model is still a correct representation of our universe, or whether it will need to be modified or abandoned altogether. Whatever happens, it’s going to be one hell of a ride.

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The muon and its oscillation https://polkinghorne.org/the-muon-and-its-oscillation/ Mon, 12 Apr 2021 07:00:00 +0000 https://polkinghorne.org/the-muon-and-its-oscillation/ There’s a lot of suspension on the unintended wobble. Muons, heavier cousins ​​of electrons, don’t behave as expected when thrown through a strong magnetic field, an Illinois lab reports. By teetering faster than expected, scientists say, they raise tantalizing questions about the accepted understanding of the fundamental laws of particle physics, the “standard model” that […]]]>

There’s a lot of suspension on the unintended wobble. Muons, heavier cousins ​​of electrons, don’t behave as expected when thrown through a strong magnetic field, an Illinois lab reports. By teetering faster than expected, scientists say, they raise tantalizing questions about the accepted understanding of the fundamental laws of particle physics, the “standard model” that describes particles (currently 17) and the forces that govern the subatomic world. .

Mainstream thinking suggests that all the forces we experience can be reduced to just four categories: gravity, electromagnetism, and, shaping the behavior of subatomic particles, the strong force and the weak force. The muon wobble suggests a fifth force that could provide an explanation for mysteries such as the accelerating expanding universe and the nature of dark matter, the invisible matter that astronomers say makes up a quarter of the mass of the universe.

Strange behaviour

Results announced last week from the Muon g-2 experiment at the Fermi National Accelerator Laboratory, or Fermilab, in Batavia – a team of 200 physicists from seven countries – appear to have successfully replicated a 20-year-old experiment on the strange behavior of muons and their deviation from the standard model remained unexplained. Separately, reports from the CERN Large Hadron Collider on the Franco-Swiss border of the decay of unstable B mesons into muons and electrons this week have also raised doubts about the model.

During a seminar and press conference last week, Fermilab physicist Dr. Chris Polly pointed to a graph displaying white space where their findings deviated from the theoretical prediction. “We can say with fairly high confidence that there must be something contributing to this white space. What monsters could be hiding there?

The work and its promising implications are far from conclusive, but scientists have likened it to the much-heralded 2012 discovery of the Higgs boson, a particle that impregnates other particles with mass. The ephemeral quantum world of the muon may be revealing its secrets.

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New muon measurements could rewrite particle physics | Smart News https://polkinghorne.org/new-muon-measurements-could-rewrite-particle-physics-smart-news/ Fri, 09 Apr 2021 07:00:00 +0000 https://polkinghorne.org/new-muon-measurements-could-rewrite-particle-physics-smart-news/ The 50-foot-wide hippodrome used to study muons traveled by barge around Florida and Mississippi, then by truck through Illinois. Reidar Hahn, Fermilab About 50 years ago, physicists came up with a rulebook to describe how fundamental particles interact to create the world as we know it. Since then, researchers have pushed this theoretical framework, called […]]]>

The 50-foot-wide hippodrome used to study muons traveled by barge around Florida and Mississippi, then by truck through Illinois.
Reidar Hahn, Fermilab

About 50 years ago, physicists came up with a rulebook to describe how fundamental particles interact to create the world as we know it. Since then, researchers have pushed this theoretical framework, called the Standard Model, to its limits in order to study its imperfections.

Today, the results of two particle physics experiments come close to uncovering a gap in the Standard Model.

The experiments focused on muons, which are similar to electrons. Both have electric charge and spin, causing them to oscillate in a magnetic field. But muons are more than 200 times larger than electrons, and they split into electrons and another particle, neutrinos, in 2.2 millionths of a second. Luckily, that’s just enough time to collect accurate measurements, with the right equipment, like a 50-foot-wide magnetic circuit.

Physicist Chris Polly of the Fermi National Accelerator Laboratory presented a graph at a seminar and press conference last week that showed a discrepancy between the theoretical calculation and actual measurements of muons moving through the racetrack.

“We can say with pretty high confidence that there has to be something contributing to that white space,” Polly said at the press conference, according to Dennis Overbye at the New York Times. “What monsters could be hiding there?”

The Standard Model aims to describe everything in the universe in terms of its fundamental particles, like electrons and muons, and its fundamental forces. The model predicted the existence of the Higgs boson particle, which was discovered in 2012. But physicists know that the model is incomplete: it takes into account three fundamental forces, but not gravity, for example.

A disconnect between theory and experimental results could help researchers uncover hidden physics and extend the Standard Model to more fully explain the universe.

“New particles, new physics could be just beyond our search,” Wayne State University particle physicist Alexey Petrov tells The Associated Press’ Seth Borenstein. “It’s tantalizing.”

The Standard Model requires such complex calculations that it took a team of 132 theoretical physicists, led by Aida El-Khadra, to come up with its prediction for the muon oscillation in the Fermi Lab experiment. The calculations predicted an oscillation lower than that measured by the Fermilab experiment.

This week’s results closely follow new findings from the Large Hadron Collider. Last month, LHC researchers showed a startling rate of particles left over after breaking up high-speed muons.

“The LHC, if you will, is almost like crashing two Swiss watches against each other at high speed. The debris comes out and you try to piece together what’s inside,” University of Manchester physicist Mark Lancaster, who worked on the Fermilab experiments, tells Michael Greshko at National geographic. At Fermilab, “we have a Swiss watch, and we look at it very, very, very, very carefully and precisely, to see if it does what we expect it to do. »

The Fermilab group used the same 50-foot-wide ring that was first used in the 2001 muon experiments. The researchers shoot a particle beam into the ring, where the particles are exposed to magnets superconductors. The beam particles decay into several other particles, including muons. Then those muons swirl around the racetrack several times before decaying, giving physicists a chance to measure how they interact with the magnetic field, writes Daniel Garisto for American Scientist.

To avoid bias, the instruments the researchers used to measure muons gave encrypted results. The key – a number written on a piece of paper and hidden in two offices at Fermilab and the University of Washington – remained secret until a virtual meeting in late February. When the key was entered into the spreadsheet, the results became clear: the experiment did not match the theory.

“We were all really ecstatic, excited, but also shocked, because deep down I think we’re all a bit pessimistic,” Fermilab physicist Jessica Esquivel tells National geographic.

If the results hold as more data from the experiment emerges, they would upend “every other calculation made” in the field of particle physics, says David Kaplan, a theoretical physicist at Johns Hopkins University. , to the Associated Press.

Freya Blekman, a physicist from the Free University of Brussels, who did not take part in the work, says National geographic that the work “is Nobel-worthy, no doubt,” if it holds up.

Results to date should be published in journals Physical examination letters, A&B physical examination, Physical examination A and physical examination d. These results come from only six percent of the data that the Fermilab experiment expects to collect. Between this six percent and the experimental results from 2001, there is a one in 40,000 chance that the difference between theory and experiment is in error.

“It’s strong evidence that the muon is sensitive to something that’s not in our best theory,” says University of Kentucky physicist Renee Fatemi. New York Times.

But particle physics demands that researchers bring that down to a one in 3.5 million chance. The research team could have the final results by the end of 2023.

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