model particle – Polkinghorne http://polkinghorne.org/ Thu, 17 Mar 2022 18:30:28 +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 model particle – Polkinghorne http://polkinghorne.org/ 32 32 A physics experiment may have uncovered the mysterious force behind the expansion of the universe https://polkinghorne.org/a-physics-experiment-may-have-uncovered-the-mysterious-force-behind-the-expansion-of-the-universe/ Mon, 27 Sep 2021 07:00:00 +0000 https://polkinghorne.org/a-physics-experiment-may-have-uncovered-the-mysterious-force-behind-the-expansion-of-the-universe/ Representative image. | Photo credit: iStock Images What the universe is made up of at the most fundamental levels is a question that continues to both fascinate and frustrate scientists. The discovery of atoms, once thought to be nature’s smallest building blocks, paved the way for further study of subatomic particles such as electrons, protons […]]]>

Representative image. | Photo credit: iStock Images

What the universe is made up of at the most fundamental levels is a question that continues to both fascinate and frustrate scientists. The discovery of atoms, once thought to be nature’s smallest building blocks, paved the way for further study of subatomic particles such as electrons, protons and neutrons, which were found to be themselves made of particles. even smaller.

As our understanding of these particles grew, the Standard Model of particle physics was born. But after looking around the universe and measuring how widely galaxies are distributed and interact with each other, we soon realized that everything described in the Standard Model was only 5% of the matter in the universe.

What is the rest made up of, you ask? Well, we don’t really know, but about 27% of the universe, scientists are convinced, appears to be made up of something called dark matter – matter that doesn’t reflect any light but behaves similarly to normal matter. , exerting a force of gravity on everything around it.

As for the elements that make up the remaining 68% of the universe, our first clue came in the 1990s when scientists discovered that distant supernovae were fainter than their models had predicted. As more and more evidence came in, a new form of energy was theorized, one that exhibits properties that no other type of matter or radiation possesses – dark energy.

There’s next to nothing we can truly determine about the true nature of dark energy, but the measurements reveal one thing: it is remarkably uniform and constant across the universe, behaving fundamentally differently than other types of energy. energy.

It seems to be driving the expansion of the universe but, curiously, even as the volume of the universe increases, the energy density (of dark energy) remains constant. It is almost as if there is something uniformly present in space, the nature of which does not depend on anything residing in space. This prompted scientists to understand that dark energy could be a vast field that pervades the entire universe or even an inherent feature of spacetime itself.

A less explored theory though is that dark energy could be made up of particles we haven’t yet discovered, and that’s where the XENON1T experiment comes in. The XENON series of experiments were originally intended to search for theoretical dark matter particles that scientists call WIMPs. (massive particles interacting weakly).

Thousands of feet below Italy’s Gran Sasso mountain is a sensor-lined tank of 3.2 metric tons of pure xenon (chemically inert), forming a detector of unknown particles that can fly through the tank, causing ripples. The idea is that as these WIMPs move through xenon, they may occasionally hit a xenon nucleus, causing a brief flash of light that could be detected – what is called nuclear recoil.

But after years of not detecting nuclear recoil, scientists realized they could recalibrate their detector to look for electron recoil – phenomena where unknown particles collide with electrons rather than nuclei. of xenon. The researchers studied the first year’s worth of XENON1T data expecting to find 232 such setbacks – all caused by background contamination. But the experiment gave 285 – an excess of 53. It was confusing. What were these additional signals?

These findings have now led scientists to formulate three theories. The first of these – and obviously the most mundane – is that the result was an experimental hazard likely to wither away with improved accuracy and stats. The second is that some sort of unaccounted background contamination – possibly tritium in the water – may be causing these excess electron recoils.

The third, of which scientists say they are 95% certain, is the first-ever detection of an unknown type of dark energy particle that would require contortions of current particle physics theory. It’s clearly the most exotic of the three theories, but it may draw attention to a particular idea known as chameleon dark energy – a notion of a particle whose density is obscured in regions of the matter-rich spaces, but more noticeable in emptier regions. .

At the moment, however, this is only conjecture. A 95% confidence interval in physics is, after all, far from sufficient, and it is entirely possible that as the experimental framework refines, these findings may never happen again. But if substantiated, it would represent a giant step towards answering one of the greatest existential questions that have plagued humanity.

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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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Muons don’t fit the standard model of particle physics https://polkinghorne.org/muons-dont-fit-the-standard-model-of-particle-physics/ Fri, 16 Apr 2021 07:00:00 +0000 https://polkinghorne.org/muons-dont-fit-the-standard-model-of-particle-physics/ Share this Item You are free to share this article under the Attribution 4.0 International License. Fundamental particles called muons behave in ways that scientists’ best theory to date, the Standard Model of particle physics, does not predict, the researchers report. The discovery comes from early results from the Muon g-2 experiment at the US […]]]>

Fundamental particles called muons behave in ways that scientists’ best theory to date, the Standard Model of particle physics, does not predict, the researchers report.

The discovery comes from early results from the Muon g-2 experiment at the US Department of Energy’s Fermi National Accelerator Laboratory.

“This experience is a bit like a detective novel.”

This historic result confirms a discrepancy that has plagued researchers for decades.

The strong evidence that muons deviate from the Standard Model calculation could hint at some exciting new physics. The muons in this experiment act as a window into the subatomic world and could interact with as yet unknown particles or forces.

“This experiment is a bit like a detective novel,” says team member David Hertzog, a University of Washington physics professor and founding spokesperson for the experiment. “We analyzed data from the inaugural Muon g-2 test at Fermilab and discovered that the Standard Model alone cannot explain what we found. Something else, perhaps beyond the standard model, may be required. »

A muon is about 200 times more massive than its cousin the electron. They occur naturally when cosmic rays hit the Earth’s atmosphere. Fermilab’s particle accelerators can produce large numbers of them. Like electrons, muons act as if they have a small internal magnet. In a strong magnetic field, the direction of the muon magnet precedes, or “wobbles,” much like the axis of a spinning top. The strength of the internal magnet determines the muon’s precession rate in an external magnetic field and is described by a number known as the g-factor. This number can be calculated with ultra-high precision.

As muons flow through the Muon g-2 magnet, they also interact with a “quantum foam” of subatomic particles that appear and disappear. Interactions with these short-lived particles affect the value of the g-factor, causing muon precession to accelerate or slightly slow down. The standard model predicts with great accuracy what the value of this “abnormal magnetic moment” should be. But if the quantum foam contains additional forces or particles not accounted for by the Standard Model, it would further alter the g-factor of the muon.

Hertzog, then at the University of Illinois, was a lead scientist in the previous experiment at Brookhaven National Laboratory. This attempt ended in 2001 and offered clues that the behavior of the muon did not conform to the Standard Model. The new measurement from the Muon g-2 experiment at Fermilab strongly agrees with the value found at Brookhaven and deviates from theory with the most accurate measurement to date.

The accepted theoretical values ​​for the muon are:

  • g-factor: 2.00233183620(86)
  • abnormal magnetic moment: 0.00116591810(43)

The new experimental global mean results announced today by the Muon g-2 collaboration are:

  • g-factor: 2.00233184122(82)
  • abnormal magnetic moment: 0.00116592061(41)

The combined results from Fermilab and Brookhaven show a difference with theoretical predictions at a significance of 4.2 sigma, a little short of the 5 sigma – or 5 standard deviations – that scientists prefer as a claim of discovery. But it’s still compelling evidence of new physics. The probability that the results are a statistical fluctuation is approximately 1 in 40,000.

“This result from the first run of the Fermilab Muon g-2 experiment is arguably the most anticipated result in particle physics in recent years,” says Martin Hoferichter, assistant professor at the University of Bern and member of the theoretical collaboration that predicts the value of the standard model. “After almost a decade, it’s great to see this massive effort finally come to fruition.”

The Fermilab experiment, which is underway, reuses the main component of the Brookhaven experiment, a superconducting magnetic storage ring 50 feet in diameter. In 2013, it was transported 3,200 miles by land and sea from Long Island to suburban Chicago, where scientists were able to take advantage of Fermilab’s particle accelerator and produce the states’ most intense muon beam. -United. Over the next four years, researchers mounted the experiment; tuned and calibrated an incredibly uniform magnetic field; developed new techniques, instruments and simulations; and thoroughly tested the entire system.

The Muon g-2 experiment sends a beam of muons into the storage ring, where they circulate thousands of times at near the speed of light. Detectors lining the ring allow scientists to determine how fast muons “wobble”.

Many Fermilab sensors and detectors have been built at the University of Washington, such as instruments to measure the muon beam as it enters the storage ring and to detect the telltale particles that appear when the muons decay . Dozens of scientists – including professors, postdoctoral researchers, technicians, graduate students and undergraduates – worked to assemble these sensitive instruments, then set them up and monitor them at Fermilab.

“The outlook for the new result has triggered a coordinated theoretical effort to provide our experimental colleagues with a robust and consensus prediction of the Standard Model,” says Hoferichter. “Future runs will motivate further refinements, to enable a conclusive statement whether physics beyond the Standard Model lurks in the muon’s anomalous magnetic moment.”

In its first year of operation, 2018, the Fermilab experiment collected more data than all previous muon g-factor experiments combined. The Muon g-2 collaboration has now completed the analysis of the movement of more than 8 billion muons from this first period.

Analysis of data from the second and third cycles of the experiment is in progress; the fourth is in progress and a fifth is planned. Combining the results from all five tests will give scientists an even more precise measurement of the muon’s ‘wobble’, revealing with greater certainty whether new physics is lurking in the quantum foam.

“So far, we’ve analyzed less than 6% of the data the experiment will eventually collect,” says Fermilab scientist Chris Polly, who is a co-spokesperson for the current experiment and was a graduate student. of the University of Illinois under Hertzog during the Brookhaven Experiment. “While these early results tell us there is an intriguing difference to the standard model, we will learn much more over the next two years.”

“With these exciting results, our team, especially our students, are excited to push hard on analyzing the remaining data and taking future data to achieve our ultimate goal of accuracy,” says Peter Kammel, research professor of physics at the University of Washington.

An article on the research appears in Physical examination letters. Hertzog will present the findings at a University of Washington Physics Department Symposium on April 12.

The Muon g-2 experiment is an international collaboration between Fermilab in Illinois and more than 200 scientists from 35 institutions in seven countries.

Source: University of Washington

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Brookhaven Lab Appoints New Director of Nuclear and Particle Physics Branch https://polkinghorne.org/brookhaven-lab-appoints-new-director-of-nuclear-and-particle-physics-branch/ Thu, 15 Apr 2021 07:00:00 +0000 https://polkinghorne.org/brookhaven-lab-appoints-new-director-of-nuclear-and-particle-physics-branch/ Haiyan Gao, nuclear physicist and professor, will join the lab as associate lab director for nuclear and particle physics UPTON, NY – Haiyan Gao, currently the Henry W. Newson Professor Emeritus of Physics at Duke University, will join the U.S. Department of Energy’s Brookhaven National Laboratory as Associate Laboratory Director (ALD) for Nuclear Physics and […]]]>

Haiyan Gao, nuclear physicist and professor, will join the lab as associate lab director for nuclear and particle physics

UPTON, NY – Haiyan Gao, currently the Henry W. Newson Professor Emeritus of Physics at Duke University, will join the U.S. Department of Energy’s Brookhaven National Laboratory as Associate Laboratory Director (ALD) for Nuclear Physics and particles (NPP) from or around June 1, 2021.

Gao, who has a long background in nuclear physics, will help develop Brookhaven’s collective long-term vision for the next 10 years. She will also work throughout the lab and beyond to develop her emerging expertise at the future Electron-Ion Collider (EIC), a one-of-a-kind nuclear physics research facility to be built at the lab over the next decade after Brookhaven’s flagship nuclear physics facility, the Relativistic Heavy Ion Collider, completes its research mission.

“The Nuclear and Particle Physics Branch is internationally well-known in the fields of accelerator science, high-energy physics and nuclear physics,” Gao said. “I am very excited about the opportunity and the impact that I will be able to have in collaboration with many people at the Lab.”

Gao will replace ALD Deputy for High Energy Physics Dmitri Denisov, who became interim NPP ALD after Berndt Mueller left office last year to return to teaching and research full-time at Duke.

“We are delighted to welcome Haiyan to Brookhaven at such an exciting time for nuclear and particle physics,” said Brookhaven Laboratory Director Doon Gibbs. “His perspective and experience will be instrumental in advancing science here in the lab and beyond.”

Gao joins Brookhaven Lab as he develops the EIC in collaboration with scientists at the DOE’s Thomas Jefferson National Accelerator Facility. The EIC will offer scientists a deeper look at the building blocks of visible matter and the most powerful force in nature.

“What’s important in the end is that we really deliver the science,” she said.

The facility is one that the nuclear physics community has been campaigning for for many years, to work towards a more complete understanding of nucleons and atomic nuclei in quantum chromodynamics, the physical theory that describes strong interactions, Gao noted. . It will also allow scientists to discover new physics beyond the Standard Model of particle physics, Gao said.

“This facility also gives us a wonderful opportunity to train a highly motivated scientific and technical workforce in this country,” she added.

In addition to his expertise in nuclear physics, Gao has a keen interest in promoting diversity, equity and inclusion in science.

Gao obtained his doctorate. in physics from the California Institute of Technology in 1994. Since then, she has held several positions in the field, including as assistant physicist at Argonne National Laboratory and assistant and associate professor of physics at Massachusetts Institute of Technology.

While at Duke, Gao also served as the Founding Professor of Physics and Vice Chancellor for Academic Affairs at Duke Kunshan University in Kunshan, China, where she spent some of her childhood years.

Gao’s research interests at Duke have included the structure of the nucleon, the search for exotic states of quantum chromodynamics, fundamental studies of low-energy symmetry to search for new physics beyond the standard model of electroweak interactions, and the development of polarized targets.

She was elected a Fellow of the American Physical Society in 2007 and won the U.S. Department of Energy’s Best Junior Researcher Award in 2000.

Brookhaven National Laboratory is supported by the US Department of Energy’s Office of Science. The 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://energy.gov/science.

Follow @BrookhavenLab on Twitter or find us on Facebook.

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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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Have we just discovered new physics? These theoretical physicists don’t think so https://polkinghorne.org/have-we-just-discovered-new-physics-these-theoretical-physicists-dont-think-so/ Mon, 12 Apr 2021 07:00:00 +0000 https://polkinghorne.org/have-we-just-discovered-new-physics-these-theoretical-physicists-dont-think-so/ When the results of an experiment don’t match the predictions made by the best theory of the day, something is wrong. Fifteen years ago, physicists from Brookhaven National Laboratory discovered something puzzling. Muons – a type of subatomic particle – were moving in unexpected ways that did not match theoretical predictions. Was the theory wrong? […]]]>

When the results of an experiment don’t match the predictions made by the best theory of the day, something is wrong.

Fifteen years ago, physicists from Brookhaven National Laboratory discovered something puzzling. Muons – a type of subatomic particle – were moving in unexpected ways that did not match theoretical predictions. Was the theory wrong? Was the experiment interrupted? Or, temptingly, was this evidence of new physics?

Since then, physicists have been trying to solve this mystery.

A group of Fermilab addressed the experimental component and on April 7, 2021, published the results confirming the original measurement. But my colleagues and I took a different approach.

I am a theoretical physicist and the spokesperson and one of the two coordinators of the Budapest-Marseille-Wuppertal partnership. This is a large-scale collaboration of physicists who tried to see if the old theoretical prediction was incorrect. We used a new method to calculate how muons interact with magnetic fields.

My team’s theoretical prediction is different from the original theory and matches both old experimental evidence and new Fermilab data. If our calculation is correct, it resolves the gap between theory and experiment and would suggest that there is not an undiscovered force of nature.

Our result was published in the journal Nature on April 7, 2021, the same day as the new experimental results.