Particle physics – Polkinghorne http://polkinghorne.org/ Wed, 28 Sep 2022 12:18:00 +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 Particle physics – Polkinghorne http://polkinghorne.org/ 32 32 A Former Particle Physicist Is Completely Ruining the Field of Particle Physics https://polkinghorne.org/a-former-particle-physicist-is-completely-ruining-the-field-of-particle-physics/ Tue, 27 Sep 2022 00:57:47 +0000 https://polkinghorne.org/a-former-particle-physicist-is-completely-ruining-the-field-of-particle-physics/ “Now is not the time to dwell on inventing particles, arguing that even a blind chicken sometimes finds a grain.” Shots fired If you’re struggling to keep up with the latest advances in particle physics, we don’t blame you. The anime field has exploded in recent years, with an extensive series of highly experimental studies […]]]>

“Now is not the time to dwell on inventing particles, arguing that even a blind chicken sometimes finds a grain.”

Shots fired

If you’re struggling to keep up with the latest advances in particle physics, we don’t blame you. The anime field has exploded in recent years, with an extensive series of highly experimental studies – and a lot of very inconclusive literature – resulting. You’d be forgiven for assuming that if so much time, money, and effort is put into a particular area of ​​study, it must be worth it. Right?

According to former particle physicist Sabine Hossenfelder, the answer is unfortunately wrong.

“It has become common practice for physicists to invent new particles for which there is no evidence, to publish articles about them, to write more articles on the properties of these particles and to demand that the hypothesis is tested experimentally,” said Hossenfelder, who now works as an astrophysicist. argued in an excoriating essay for The Guardian. “It’s a waste of time and money.”

Big grain time

Hossenfelder’s case rests on several critiques of the field, the first being social. Basically, she says, everyone follows the leader. If your peers are receiving grants in the name of faraway, conceptual, unproven particles, why would anyone pull out? Science doesn’t come cheap, and going against the grain is inherently a much harder sell.

But that question aside, the astrophysicist thinks there’s a deeper problem with the race to discover particles: that particle physicists have “misinterpreted” Karl Popper’s philosophy of falsifiability, the misinterpreting it to mean, as she writes, that “every falsifiable idea is also good science.”

In other words, many of his peers have used falsifiability to justify a good deal of dead-end research, rather than using it as a guideline. And this, in his view, has led to the use and study of misinterpreted and-or-probably-not-real particles as convenient plugs for statistical holes in a number of other theories. A disturbing observation, given that, if true, it would mean that a lot of research there is blocked by non-existent glue.

“I believe that there are breakthroughs waiting to be made in the fundamentals of physics; the world needs technological advances more than ever”, explains the astrophysicist, “now is not the time to dwell on inventing particles, arguing that even a blind chicken sometimes finds a grain.”

“It saddens me,” she added, “to see that the estate has become a wasteful academic paper mill.”

READ MORE: Nobody in physics dares to say it, but the race to invent new particles is useless [The Guardian]

Learn more about particle physics: CERN scientists annoyed that people think they’re losing reality

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The Standard Model of Particle Physics: Theory of the Subatomic World https://polkinghorne.org/the-standard-model-of-particle-physics-theory-of-the-subatomic-world/ Mon, 19 Sep 2022 13:30:05 +0000 https://polkinghorne.org/the-standard-model-of-particle-physics-theory-of-the-subatomic-world/ The Standard Model is the most comprehensive description of the subatomic world that has ever been created in modern physics. The model was built throughout the 20th century on the foundations of Quantum mechanics, the strange theory that describes the behavior of particles at the smallest scales. The Standard Model explains three of the four […]]]>

The Standard Model is the most comprehensive description of the subatomic world that has ever been created in modern physics. The model was built throughout the 20th century on the foundations of Quantum mechanics, the strange theory that describes the behavior of particles at the smallest scales. The Standard Model explains three of the four forces of nature: electromagnetism, strong nuclear force and the weak nuclear force. The theory has been tested thousands of times with incredible accuracy and, despite its shortcomings, remains one of the most important achievements of modern science.

“It’s the dominant paradigm for thinking about how things interact at the most basic level,” and it’s been “tested to a phenomenal degree of accuracy,” said Union College physicist and author Chad Orzel. of several popular physics books, including “How to Teach Your Dog Quantum Physics” (Scribner, 2009), Live Science said in an email.

How was the standard model developed?

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Lia Merminga has a vision for particle physics https://polkinghorne.org/lia-merminga-has-a-vision-for-particle-physics/ Fri, 09 Sep 2022 17:29:20 +0000 https://polkinghorne.org/lia-merminga-has-a-vision-for-particle-physics/ As a child, she played hopscotch in the suburbs of Athens. Today, the director of Fermilab wants the facility to lead the world in neutrino research. By Sophia Chen | September 9, 2022 Credit: Fermilab Lia Merminga, director of Fermilab Lia Merminga still remembers her first glimpse of the United States, as her plane arrived […]]]>

As a child, she played hopscotch in the suburbs of Athens. Today, the director of Fermilab wants the facility to lead the world in neutrino research.

By Sophia Chen | September 9, 2022

Credit: Fermilab

Lia Merminga, director of Fermilab


Lia Merminga still remembers her first glimpse of the United States, as her plane arrived from Greece in 1983. On the descent to New York, Merminga saw the densely populated skyscrapers of Manhattan.

“I just felt inspired,” says Merminga, who comes from the outskirts of Athens. “I said, ‘My God, how privileged I am.’ I wanted to do something big. I still have that feeling now.

From there, Merminga went to the University of Michigan, where she earned her doctorate in physics and began her decades-long career innovating particle accelerators for high-energy physics research. She began leading these efforts, most recently leading Proton Improvement Plan-II (PIP-II), an ongoing upgrade of the Fermi National Accelerator Laboratory complex of accelerators outside of Chicago. Founded in 1966, the 6,800-acre site of Fermilab has hosted landmark experiments in particle physics, such as the 1995 discovery of the top quark.

Last April, Merminga became the new director of Fermilab, the first woman to hold this position. As director, Merminga oversees nearly 2,000 people working on cutting-edge experiments, ranging from the Muon G-2 experiment, whose 2021 measurement of the muon’s magnetic moment could point to physics beyond the Standard Model, at the Long-Baseline Neutrino Facility currently under construction, designed to study the properties of neutrinos that could help explain why the amount of matter dominates antimatter and why the universe exists.

Under his leadership, Merminga hopes to cement Fermilab’s position as the world leader in neutrino physics for decades to come. “We will do the definitive neutrino experiments here,” she says.

Merminga spoke to APS News about his life, career, and views on the future of particle physics.

This interview has been edited for length and clarity.

SC: You are from Greece. Can you describe where you grew up?

LM: I was born and raised in Chalandri, in the suburbs of Athens. I still have many friends who live in the area. I grew up playing in the street outside my house with other children. We played tennis, football and a game like hopscotch. I walked everywhere, to school, to the bakery, to the farmer’s market. The whole town had a high school and we were divided into girls and boys. The girls went to school in the morning from Monday to Wednesday and the boys in the afternoon. Then the following week, the program would change.

How did you decide to become a physicist?

In Greece, at 15, you have to choose between studying the humanities or the sciences. At that time, I knew that I loved physics and mathematics. Looking back, I really liked describing a physical phenomenon with the language of mathematics. For me, it was the ultimate form of elegance. I also liked that the physics and math problems had a real answer that wasn’t subjective.

My first exposure to science was through my mother’s and grandmother’s stories about my uncle [George Dousmanis], who had a doctorate in physics from Columbia University. He was legendary in my family, but he died very young, at 37. [from a heart attack]. I met him once when he came over from the United States when I was two, but I have no recollection of him. Later, when I became a graduate student, I was able to read some of his physics papers. I appreciated how exceptional he was and how unfortunate his untimely death was.

Also, when I was 13, a college friend of mine gave me a biography of Marie Curie written by her daughter Eva Curie. I just absorbed this book. Then, in high school, I had a fantastic physics teacher. All this influenced my interest in physics.

You started in theoretical physics as an undergraduate at the University of Athens, but then pivoted to accelerator physics in graduate school at the University of Michigan. What led you to make this change?

I’ve always loved theoretical physics, but it takes so long between the development of a theory and its experimental demonstration. For example, the Higgs boson was supposed to exist in the early 1960s, and it wasn’t discovered until 2012. In the meantime, thousands of people had to build the largest particle accelerator in the world.

When I was in graduate school looking for a PhD thesis topic, my current husband, who was a friend at the time, was a postdoc at Fermilab. He told me about a graduate program in accelerator physics. I realized that with accelerator physics you can do theoretical physics and validate those predictions using test facilities in a matter of months or a year. It also turned out that I love engineering. I decided to go into accelerator physics, and I’ve been having a blast ever since.

Photo by Lia Merminga
Credit: Fermilab

Merminga (right) and engineer Lidija Kokaska discuss PIP-II, an upgrade to Fermilab’s accelerator complex.


What are the major current challenges in the development of future accelerators?

We have pushed the performance of the accelerators in terms of higher energy, intensity and efficiency. A big challenge today is to reach higher energies using more compact machines. The ultimate breakthrough in our field would be to manufacture plasma accelerators [a method that would significantly reduce facility size].

A shorter term goal is to produce more efficient technology to create accelerators that consume less energy. I would like to see more progress on sustainable accelerators.

Without improved technology, future colliders would consume enough energy for a small town. What strategies are people working on to make accelerators more sustainable?

People are starting to make more energy-efficient components, such as superconducting and radio frequency (RF) power supplies. The design of the European source of spallation [a neutron source under construction in Sweden] also recovers the waste heat produced by the accelerators and then uses it to heat the neighboring buildings.

Proposed future colliders include a 100 TeV circular collider, linear electron-proton colliders like the ILC, and muon colliders. What is your opinion on what the particle physics community should invest in?

For the health of our field, it behooves us to continue these design studies of all these different types. But we still have to solve important technical and physical questions for each of these approaches. Fortunately, these approaches require similar research and development. For example, several of them require high-field magnets and highly efficient superconducting RF technology. CERN has already chosen to pursue a future 100 TeV circular collider.

What kind of behind-the-scenes activity goes into these massive particle physics projects?

There are not only a large number of people involved, but also a diversity of expertise and cultural backgrounds. For PIP-II [the upgrade to Fermilab’s accelerator complex], we have worked with partners in the UK, Poland, France, Italy, etc. Some are physicists, engineers, technicians, computer scientists, administrators, logisticians and even import and export control lawyers. This diverse set of people working towards a common goal – it makes for such an amazing result.

In 2019, a New York Times The editorial sparked a public debate about whether science drove the need for a larger collider, particularly because the price tag is in the billions of dollars. What is your response to these criticisms?

Colliders are essential instruments that have helped advance our field forever. The Tevatron, which until 2011 was the highest energy collider in the world, made it possible to discover the tau neutrino and the top quark. The LHC discovered the Higgs. In terms of discoveries, these investments have paid off extremely well.

Several Fermilab physicists have drawn attention to anti-black racism in science. They helped organize a #ShutDownSTEM strike in 2020 and formed a group called Change Now, which wrote a document calling for racial justice and fairness at Fermilab. How do you approach these issues?

Even before taking on my duties as director, I knew that I wanted to listen to our collaborators, our teams and our users on the culture of our laboratory. In this context, I launched what I call listening tours. I receive groups of 10 to 20 people for 30 minutes to an hour. In our discussions, I mostly listen. My goal is to reach every employee in our lab. We are now about a third of the way through about 2,000 people on staff. It is obvious that we have work ahead of us.

I read the ChangeNow document and met with group members one-on-one to continue the discussion. I want to understand how people feel and what they’ve been through historically. This deserves a long-term strategic plan, not a quick fix. I fundamentally believe that we must have excellence and diversity in our workforce, our activities and the operations of the laboratory, in order to achieve excellence in our scientific mission. Excellence means an environment where everyone feels they can thrive, can advance their careers, and can experience gratification in their work.

Sophia Chen is a writer based in Columbus, Ohio.

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How do dark photons work (particle physics) | by Monodeep Mukherjee | Sep 2022 https://polkinghorne.org/how-do-dark-photons-work-particle-physics-by-monodeep-mukherjee-sep-2022/ Sat, 03 Sep 2022 20:02:59 +0000 https://polkinghorne.org/how-do-dark-photons-work-particle-physics-by-monodeep-mukherjee-sep-2022/ Photo by Bhushan Sadani on Unsplash Formation and dynamics of dark photon vortices(arXiv) Author : William E. East, Junwu Huang Summary : We study the formation and evolution of vortices in dark matter of U(1) black photons and the clouds of black photons that arise through the superradiance of black holes. We show how the […]]]>
Photo by Bhushan Sadani on Unsplash
  1. Formation and dynamics of dark photon vortices(arXiv)

Author : William E. East, Junwu Huang

Summary : We study the formation and evolution of vortices in dark matter of U(1) black photons and the clouds of black photons that arise through the superradiance of black holes. We show how the production of photonic dark matter in the longitudinal mode and in the transverse mode can lead to the formation of vortices. After the formation of the vortex, the energy stored in the dark matter of dark photons will be transformed into a large number of vortex chains. In the event that a magnetic field of dark photons is produced, bundles of vortex strings form in a superheated phase transition, and evolve into a pattern consisting of many large-scale uncorrelated string loops, analogous to a phase transition. fusion phase in condensed matter. In the process, they dissipate via the emission of dark photons and gravitational waves, providing a target for experimental research. Vortex chains have also recently been shown to form in dark photon superradiance clouds around black holes, and we discuss the dynamics and observational consequences of this phenomenon with phenomenological parameters. In this case, the string loops ejected from the superradiance cloud, in addition to producing gravitational waves, are also quantized magnetic flux lines and can be tracked with magnetometers. We discuss the connection between the dynamics in these scenarios and the similar vortex dynamics found in Type II superconductors

2. Searches for dark photons via the production of Higgs bosons at the LHC and beyond(arXiv)

Author : Sanjoy Biswas, Emidio Gabrielli, Barbara Mele

Summary : Numerous scenarios beyond the Standard Model, aimed at solving long-standing problems in cosmology and particle physics, suggest that dark matter could undergo long-range interactions mediated by unbroken dark U(1) gauge symmetry , thus predicting the existence of a massless dark photon. Unlike the massive dark photon, a massless dark photon can only couple to the standard model sector by means of efficient higher-dimensional operators. The production of massless dark photons at colliders will then in general be suppressed at low energy by a UV energy scale, which is on the order of the masses of portal (messenger) fields connecting the dark and observable sectors. A violation of this expectation is provided by the production of dark photons mediated by the Higgs boson, thanks to the non-decoupling properties of Higgs. The production of Higgs bosons in colliders, followed by the Higgs decay into a photon and a dark photon, then provides a very promising production mechanism for the discovery of the dark photon, being insensitive in certain UV-scale regimes of the new physics. This decay channel gives rise to a particular signature characterized by a monochromatic photon with an energy equal to half the Higgs mass (in the Higgs rest frame) plus the missing energy. We show how such a resonant missing photon-plus-energy signature can be uniquely connected to dark photon production. The production and decay of the Higgs boson into a photon and a dark photon as a source of dark photons is reviewed at the Large Hadron Collider, in light of the current limits of the corresponding signature by the CMS and ATLAS collaborations. Prospects for the production of dark photons in Higgs-mediated processes in future e+e− colliders are also discussed.

3. Constraints on the dark photon of parity violation and mass W (arXiv)

Author : AW Thomas, XG Wang

Summary : We present an analysis of experimental data for parity violating electron scattering (PVES) and atomic parity violation, including the effects of a dark photon. We derive the privileged region of the dark photon parameter space, which provides a good description of the experimental data from the Qweak collaboration and the Jefferson Lab PVDIS collaboration and simultaneously relieves the tension between the neutron skin thickness determined in the PREX-II experiment and nuclear-model predictions. In addition, we extract the parametric region required to explain the latest mass anomaly of the W boson. Our results indicate that a heavy dark photon with a mass greater than the mass of the Z boson is favored, while other sources of new Physics beyond the Standard Model in addition to the dark photon would also be expected.

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What particle physics can do to improve diversity https://polkinghorne.org/what-particle-physics-can-do-to-improve-diversity/ Fri, 02 Sep 2022 11:46:12 +0000 https://polkinghorne.org/what-particle-physics-can-do-to-improve-diversity/ Physicist Kétévi Assamagan co-led the Diversity, Equity, and Inclusion Working Group for a leading US particle physics journal called Snowmass.Credit: Brookhaven National Laboratory This year, thousands of particle physicists debated the future of their field in the United States, in a roughly once-a-decade planning exercise called Snowmass. For the first time, the process — which […]]]>

Physicist Kétévi Assamagan co-led the Diversity, Equity, and Inclusion Working Group for a leading US particle physics journal called Snowmass.Credit: Brookhaven National Laboratory

This year, thousands of particle physicists debated the future of their field in the United States, in a roughly once-a-decade planning exercise called Snowmass. For the first time, the process — which influences U.S. federal funding — elevated diversity, equity, and inclusion (DEI) issues among the top ten topics, or boundaries, that were discussed.

DEI was part of Snowmass’ ‘community engagement’ frontier, alongside issues such as career development, education and outreach. Physics in the United States is heavily dominated by white men; in 2018, women only received 22% of doctorates in physics and only 7% went to underrepresented minorities1.

Nature spoke to Kétévi Assamagan, a particle physicist at Brookhaven National Laboratory in Upton, New York, and co-organizer of the Community Engagement Frontier, about the DEI recommendations that emerged from the Snowmass process — and why meritocracy in particle physics is an illusion.

DEI issues were more prominent than ever in the Snowmass process. Why now?

The death of George Floyd in 2020, and other times police have killed black people, have made people more aware that something needs to be done. Many institutions and organizations have started paying attention to DEI issues and work climate.

But this does not necessarily translate into action. In an anonymous survey we did at Snowmass, we saw that men, in general, believe less that there is a problem with diversity. They are the most important group in physics and the people who need to be convinced if we want to translate everything we talk about into change.

Does particle physics have a particular problem with diversity?

Particle physics wasn’t meant to exclude people, but that’s how it evolved. This requires a threshold of funding and access to education, and this is where exclusion and marginalization, especially of people in developing countries, comes into play.

How do you convince people that particle physics is not a meritocracy?

People in the mainstream culture think, “I’m not racist, I don’t see any racism in my band, so if these people work hard, it’ll be fine.” But research has shown that there is far more underrepresentation in our field than meritocracy suggests.

The culture is not welcoming and the climate is not conducive to the presence of certain people. Unconscious bias fuels how people progress and rise to higher positions, and how senior managers then maintain that culture. We do not ask for favoritism for any group. We’re talking about making the environment and culture work for everyone as it does for the majority.

Can you give me examples of how an unwelcoming climate can affect particle physicists?

Someone might ask a female physicist, “Can you bring me some coffee?” Or I could go to my lab and a newly hired white person could ask me, “When are you going to clean my room?” It is assumed that people who look like me can only be there to do this kind of work. The police were called on co-workers because they were in the building where people didn’t expect them to be.

These incidents make people very uncomfortable and mean that you have to work to demonstrate that you are in that space because you have the training and the ability to be there. People might also say that you are a “diversity recruit”. As minorities, we’re supposed to take all those things, ignore them, and excel like everyone else.

What are some of your recommendations for improving the working climate and encouraging diversity?

It starts with enforcing a code of conduct for everyone, including anti-harassment policies and policies to protect victims when reporting concerns. Conducting work climate surveys will tell you what your community needs. For example, for people with disabilities, you should ensure that meetings are organized with their needs in mind.

You also need to start engaging with science in schools and building the pipeline – there are minority-serving institutions that have a lot of capacity that particle physics can tap into.

Leadership is also important. One of the papers submitted to Snowmass says there needs to be a cultural shift where people are chosen for leadership positions by excellence and then promote an environment of fairness and excellence, for example by away from automatically rewarding privileges such as coming from a better university.

How will Snowmass recommendations be implemented?

The American Physical Society’s Division of Particles and Fields is forming a committee to see if they can find a way to coordinate efforts across different agencies and remind people that we have a set of recommendations for the institutions. This means that at the next Snowmass we won’t have to discuss the same things again.

How involved were physicists in the frontier of community engagement during Snowmass?

Not enough. Very few people participated in community engagement activities, compared to the broad areas of physics. All of this research work has been done by just a few people. People feel they understand the issues and want solutions, but they don’t have a lot of time to devote to them.

This interview has been edited for length and clarity.

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Hitchhiker’s Guide to the Standard Model of Particle Physics https://polkinghorne.org/hitchhikers-guide-to-the-standard-model-of-particle-physics/ Thu, 01 Sep 2022 07:00:00 +0000 https://polkinghorne.org/hitchhikers-guide-to-the-standard-model-of-particle-physics/ At the turn of the 4th century BC, the Greek philosopher Democritus smelled the smell of pastry and thought that small pieces of bread must have been floating through the air and into his nose. He called the little pieces “atoms” (meaning “uncuttable”) and imagined them as tiny spherical balls. But atoms are not small […]]]>

At the turn of the 4th century BC, the Greek philosopher Democritus smelled the smell of pastry and thought that small pieces of bread must have been floating through the air and into his nose. He called the little pieces “atoms” (meaning “uncuttable”) and imagined them as tiny spherical balls.

But atoms are not small solid spheres. They are made up of even smaller pieces, called particles.

The best scientific description of these particles and the forces that govern their behavior is called the Standard Model of Particle Physics, or simply “The Standard Model.”

The Standard Model categorizes all of nature’s particles, the same way the periodic table categorizes the elements. The theory is called the Standard Model because it has been so successful that it has become “standard”.

And no, there is no Economy model or Deluxe.

There are, however, still a few issues to iron out (as well as some huge omissions). This is why it is sometimes called the “theory of almost everything”.

How it all began ?

At the start of the 20th century, scientists believed that there were only three fundamental particles in nature: protons and neutrons, which make up the nucleus of an atom, and the electrons which swirl around it.

But in the 1950s and 1960s, physicists started squishing these particles, and some of them shattered. It turned out that protons and neutrons had even smaller particles inside.

Several dozen new particles were discovered – and for a while no one could explain them. Physicists called it the “particle zoo”.

In the 1970s, physicists like Murray Gell-Mann found order in chaos. The approach they took was similar to that of the Russian chemist Dmitry Mendeleev to find an order to the chemical elements in his periodic table.

The new particle order explained many newly discovered particle properties, as well as correctly predicted some new ones.

These 17 fundamental particles constitute the standard model of particle physics. – MissMJ/Wikimedia Commons

Meet the family

Standard Model particles form a large family. Your first introduction can be daunting, a bit like attending a meeting with lots of distant cousins ​​you’ve never heard of. No matter how weird these cousins ​​are, it’s important to remember that they’re all related.

The basics

Gell-Mann and others have classified particles into two main categories: fermions and bosons.

The fermions, such as the electron, constitute what we call matter. Bosons, like the photon, transmit forces.

Fermions are further subdivided into two types of particles, depending on the forces they feel. These are quarks and leptons (see below).

forces of nature

Particles communicate with each other via four forces: electromagnetism, strong force, weak force and gravity.

The Standard Model describes the first three (gravity is not in the Standard Model, as explained below).

Different particles communicate through different forces, the same way people can communicate in different languages. For example, only quarks speak “gluon”. While electrons can speak “photon” as well as “W boson” and “Z boson”.

Electromagnetism is the force that holds electrons in an atom. It is communicated by photons.

The strong force holds the nuclei of atoms together. Without it, every atom in the universe would spontaneously explode. It is communicated by gluons.

The weak force causes radioactive decay. It is transmitted by the W and Z bosons.

Fundamental particles

All matter is made up of two types of particles called quarks and leptons.

Quarks: (the purple particles in the figure) come in six “flavors”, all with strange names. It helps to see them come in pairs to form three generations. These are “high” and “low” (first generation), “charmed” and “strange” (second generation), and “high” and “low” (third generation).

Only up and down quarks are important in everyday life because they make protons and neutrons.

The others only make “exotic” matter, too unstable to form atoms. Physicists can create exotic matter in particle accelerators, but it usually only lasts a fraction of a second before it decays.

leptons: there are six leptons, the best known of which is the electron, a tiny fundamental particle with a negative charge.

The muon (second generation) and tau (third generation) particles are like fatter versions of the electron. They also have a negative electrical charge, but they are too unstable to appear in ordinary matter.

And each of these particles has a corresponding, chargeless neutrino.

Neutrinos deserve special mention because they are perhaps the least understood of all the Standard Model particles.

They are fast but only interact with weak force, which means they can easily cross a planet. They are created during nuclear reactions, such as those that power the core of the Sun.

Hadrons: composite particles

Now that we know the fundamental particles of nature, we can start stacking them up in different ways to make larger particles.

The most important composite particles are the baryons, made up of three quarks. Protons and neutrons are the two types of baryon.

The largest particle collider of the European Organization for Nuclear Research (CERN) crushes protons. Because protons are a kind of hadron, it’s called the Large Hadron Collider, or LHC.

Antimatter: double or nothing?

As far as we know, all quarks and leptons have twin particles of antimatter. Antimatter is like matter except it has the opposite charge. For example, the electron has a counterpart that has exactly the same mass, except with a positive charge instead of negative. When a matter particle meets its antimatter twin, they both annihilate in a burst of pure energy.

Antimatter is incredibly rare in the Universe, although it plays an important role in technology. Positron emission tomography (PET) scanners, for example, use positron annihilation to see inside the body.

One of the great mysteries of physics is why the Universe is made up almost entirely of matter. Many particle physicists are trying to answer them.

Atoms: composites of composites

The bread that Democritus sniffed is made of only the first generation of fundamental particles.

Up and down quarks bind together by the strong force to form protons and neutrons, and the strong force also sticks them together to form the nucleus of an atom.

Electrons orbit the nucleus in arrangements determined by quantum mechanics (see our introduction to quantum physics for the confusing end-stages).

The Higgs: the divine particle

You’ve probably noticed the loner on the right side of the particle table – the Higgs boson. The Higgs is a special type of particle that gives other fundamental particles their mass.

The idea is that there is an existing field everywhere in space. And when particles move through space, they tend to collide with this field, and this interaction slows them down (in the same way that it is harder to move in water than in air) . This interaction is what gives the fundamental particles their mass.

Some particles such as photons and gluons do not interact with the Higgs field and are therefore massless.

Just as photons communicate electromagnetic force, the Higgs boson communicates the Higgs field.

The Higgs boson was a theoretical particle until 2013 when CERN announced that it had finally been discovered, although scientists are still uncovering its properties.

What is missing ?

Gravity

The biggest hole in the standard model is the lack of gravity. The fourth force of nature simply does not fit into the current picture.

Gravity is also incredibly weak compared to other forces (the strong force is 100,000,000,000,000,000,000,000,000,000,000,000,000 times stronger than gravity, for example).

Some physicists believe that gravity is also transmitted by a kind of particle, called a graviton, but so far there is no evidence that this particle exists.

Neutrino mass

The neutrino is so small compared to all other particles that it really begs an explanation. It is possible that the neutrino does not derive its mass from the Higgs in the same way as other particles.

Black matter: To observe the Universe, it seems that a large part of it consists of dark matter – a new type of matter that does not interact with ordinary matter and is therefore probably entirely absent from the Standard Model.

Supersymmetry

Some physicists are looking for extensions to the Standard Model to explain these mysteries. Supersymmetry is an extension where each particle has another twin with higher mass.

Some of these particles would interact very weakly with ordinary things and could therefore be good candidates for dark matter.


Check out some of the latest research on the Standard Model of particle physics:



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Nucleons select pair partners differently in small nuclei https://polkinghorne.org/nucleons-select-pair-partners-differently-in-small-nuclei/ Wed, 31 Aug 2022 15:00:54 +0000 https://polkinghorne.org/nucleons-select-pair-partners-differently-in-small-nuclei/ Two of tritium’s three nucleons can form short-range correlations that include a proton and one of its neutrons or two neutrons. Credit: DOE’s Jefferson Lab When the odds are equal, particles pair up with others of the same type more often than expected. Protons and neutrons, which make up the atom‘s core, often pair up. […]]]>

Two of tritium’s three nucleons can form short-range correlations that include a proton and one of its neutrons or two neutrons. Credit: DOE’s Jefferson Lab

When the odds are equal, particles pair up with others of the same type more often than expected.

Protons and neutrons, which make up the atom‘s core, often pair up. Now, a new high-precision experiment has discovered that these particles can choose different partners depending on the density of the nucleus. The work was carried out at the US Department of Energy’s Thomas Jefferson National Accelerator Facility.

The findings also reveal new details about short-range interactions between protons and neutrons in nuclei and could impact the results of experiments aimed at unraveling deeper details of nuclear structure. The data is an order of magnitude more precise than in previous studies, and the research will be published today (August 31, 2022) in the journal Nature.

Shujie Li is the lead author of the article. She is a postdoctoral researcher in nuclear physics at the DOE’s Lawrence Berkeley National Laboratory in Berkeley, Calif., and began working on the experiment as a graduate student at the University of New Hampshire. Li said the experiment was designed to compare short-lived partnerships between protons and neutrons, called short-range correlations, in small nuclei.

Protons and neutrons are collectively called nucleons. When involved in short-range correlations, nucleons overlap briefly before separating with high momentum. Correlations can form between a proton and a neutron, between two protons or between two neutrons.

This experiment compared the prevalence of each type of short-range correlation in the so-called mirror nuclei of helium-3 and tritium, an isotope of hydrogen. These nuclei each contain three nucleons. They are considered “mirror nuclei” because the proton content of each reflects the neutron content of the other.

“Tritium is composed of one proton and two neutrons, and helium-3 is composed of two protons and one neutron. By comparing tritium and helium-3, we can assume that the neutron- proton in tritium are the same as the neutron-proton pairs in helium-3. And tritium can produce an extra neutron-neutron pair, and helium-3 can produce an extra proton-proton pair,” Li explained.

Taken together, the data from the two nuclei reveals how often nucleons pair up with others like them versus those that are dissimilar.

“The simple idea is just to compare how many pairs the two cores have in each configuration,” she said.

Physicists expected to see a result similar to previous studies, which found that nucleons prefer to pair more than 20 to 1 with a different type (for example, protons paired with neutrons 20 times for each time that they pair with another proton). These studies were conducted in heavier nuclei with many more protons and neutrons available for pairing, such as carbon, iron, and lead.

“The ratio we extracted in this experiment is four neutron-proton pairs for every proton-proton or neutron-neutron pair,” Li revealed.

This surprising result gives new insight into the interactions between protons and neutrons in nuclei, according to John Arrington, spokesperson for the experiment and Berkeley Lab scientist.

“So in this case, we see that the proton-proton contribution is much, much larger than expected. So that raises questions about what’s different here,” he said.

One idea is that interactions between nucleons are a driver of this difference, and these interactions are somewhat modified by the distance between nucleons in tritium versus helium-3 versus very large nuclei.

“In the nucleon-nucleon interaction, there is the ‘tensor’ part, which generates neutron-proton pairs. And there’s a shorter-range “nucleus” that can generate proton-proton pairs. When the nucleons are further apart, like in these very light nuclei, you can get a different balance between these interactions.

Differences in the average distances between potentially correlated nucleons can have a strong influence on which particles they choose to pair up with in an overlapping short-range correlation. For reference, a proton is just under a femtometer, or fermi, wide. The longer-range tensor part of the short-range interaction dominates when the particles overlap on the order of a half-fermi, or about a half-particle overlap. The shorter-range central part of the interaction dominates because the particles mostly overlap at one fermi.

He says further research on this topic will help test this idea. In the meantime, scientists are studying whether the result will impact other measures. For example, in deep inelastic scattering experiments, nuclear physicists use hard short-range collisions to explore the structure of nucleons.

“We are pushing precision in nuclear structure experiments, and so these seemingly small effects can become very significant as we continue to produce high-precision results at Jefferson Lab,” said Douglas Higinbotham, spokesperson for the Jefferson Lab experiment and scientist. . “So if nuclear effects are not only persistent but unexpected in light nuclei, that means you may have unexpected things in your deep inelastic scattering results.”

Arrington agreed.

“We are always making new measurements in familiar nuclei that are relevant to nuclear structure and finding surprises. So the fact that we’re still finding surprises on a simple kernel is very interesting,” Arrington commented. “We really want to understand where it’s coming from, because it has to tell us something about how nucleons interact at close range, which is hard to measure outside of Jefferson Lab.”

This experiment was conducted in Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF), a Science Bureau User Facility, in its Experimental Hall A. It featured a single tritium target designed for a series of rare experiments, and it used another tactic to capture a data set that is a factor of 10 more accurate than previous experiments: measuring only electrons that have bounced off a correlated nucleon inside mirror nuclei.

“Through looking at tritium and helium-3, we were able to use inclusive scattering, which gives us much higher stats than other metrics. This is a very unique chance, and a excellent design, and a lot of effort from the tritium project to achieve this result,” Li added.

Nuclear physicists want to follow up this intriguing result with additional measurements in heavier nuclei. The first experiments in these nuclei used high-energy electrons generated in CEBAF. Electrons bounced off protons or neutrons engaged in short-range correlation and the “triple coincidence” of the outgoing electron, the knocked out proton and the correlated partner was measured.

A challenge for this type of two-nucleon short-range correlation measurement is to capture all three particles. Still, it’s hoped that future measurements can capture the short-range correlations of three nucleons for an even more detailed view of what’s going on inside the nucleus.

In the near term, Arrington is a co-spokesperson for another experiment that is gearing up for additional measurements of short-range correlations at CEBAF. The experiment will measure the correlations in a range of light nuclei, including the isotopes of helium, lithium, beryllium and boron, as well as a number of heavier targets that vary in neutron-proton ratio.

Reference: “Revealing the short-range structure of the mirror kernels 3H and 3He” August 31, 2022, Nature.
DOI: 10.1038/s41586-022-05007-2

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A summer of particle physics https://polkinghorne.org/a-summer-of-particle-physics/ Wed, 24 Aug 2022 21:30:38 +0000 https://polkinghorne.org/a-summer-of-particle-physics/ Three young physicists from the University of California at Riverside are thinking big. Gigantic-particle-great accelerator. Undergraduate students Andrew Caruso, Robert Vasquez and Selim Zoorob completed internships this summer at the European Organization for Nuclear Research, or CERN. The center is home to the Large Hadron Collider, or LHC, the largest and most powerful particle accelerator […]]]>

Three young physicists from the University of California at Riverside are thinking big. Gigantic-particle-great accelerator. Undergraduate students Andrew Caruso, Robert Vasquez and Selim Zoorob completed internships this summer at the European Organization for Nuclear Research, or CERN. The center is home to the Large Hadron Collider, or LHC, the largest and most powerful particle accelerator in the world.

The LHC, a circular tunnel with a circumference of 17 miles, smashes particles by firing two beams of them traveling in opposite directions through the tunnel. After several spins, the particles approach the speed of light and collide head-on, their debris giving physicists an opportunity to study the quantum world.

Andre Caruso. (UCR/Andrew Caruso)

Caruso, 22, was motivated to apply for the internship at CERN because he was interested in both experimental particle physics and a piece of software used at CERN called ROOT. After being offered the internship, he took a course in particle physics at UCR, which further piqued his interest in the field.

Having never been to Europe or pursued such an opportunity, Caruso had no idea how central daily life and work would be.

“I thought the work would be similar to what I did with the ROOT software in my undergraduate research in physics at UCR, and the daily life would be similar to that on campus,” he said. declared. “As I gained experience, I found that CERN exceeded those expectations. I ended up not using the ROOT software at all, but instead created a program using Python, a programming language.

Caruso discovered that CERN had a rich diversity of international students and offered him a range of opportunities in computer science and physics through workshops and conferences. He appreciates that CERN promotes communication between students and organizes extracurricular activities through clubs and events.

“It’s easy to find things to do and meet new people,” he said. “Furthermore, all students are CERN personnel and are treated as such. I was expected to work on my project and take advantage of learning and social opportunities.

The project that Caruso worked on at CERN is called “Model of NA62 CEDAR”.

“The NA62 experiment is a fixed-target experiment in which a beam of protons hits a fixed target and produces particles called kaons whose decays are studied,” he said.

Caruso believes his experience at CERN will enhance his interest and skills in the field of particle physics, which will ultimately benefit his career. In his spare time, he traveled to Geneva and places in or near Switzerland.

“It was a unique opportunity to not only engage in intriguing scientific research, but also to learn new topics and meet many people,” he said. “It’s amazing to work and talk with people from so many different backgrounds. Sure, sometimes there are language barriers, but it’s fun to learn other people’s languages ​​and cultures. It is also amazing how many people are part of CERN, since the sites are basically small towns with their own fire brigades, hostels, cafeterias, buses and medical centre. There are many people, not just scientists, who keep CERN running. »

Robert Vasquez

Robert Vasquez. (UCR/Robert Vasquez)

Basin, 27, a first-generation student, has always wanted to visit CERN for the work and research carried out there. But when he saw the internship application via the UCR Physics Undergraduate digital bulletin board, his first thought was not to apply.

“I thought I had no chance,” he said. “But my mum would have encouraged me to apply and after losing her to COVID-related complications last year, I thought it would be a good way to honor her memory.”

CERN exceeded Vasquez’s expectations in terms of the physical size of the facility and the research carried out there.

“What I’m most excited about at CERN is a facility called the ‘Antimatter Factory’, where they produce and experiment with antimatter, including studies of how it interacts with gravity,” said he declared.

For Vasquez, the benefit of working with an international team of scientists was learning how other countries differ from the United States in their approach to education, scientific interests, and culture.

The project he worked on focused on expanding the functionality of the AppLE.py program.

Vasquez explained that particle accelerators use magnets to change the direction and focus of particles moving through them. To know how these particles will behave when they pass through these magnets requires a set of equations that dictate the behavior. For a magnet and a particle, the calculations are relatively simple, but for several thousand particles passing through several magnets, the calculations can be long and tedious.

“A program called MAD-X has been developed to simulate the beams traveling through these magnets,” he said. “This program works but can be difficult to run for repeated simulations. To make things easier, a program called AppLE.py is being developed as a user-friendly GUI in Python. My job was to program additional features into the app to make the job easier for those who use these magnets. »

Vasquez thinks his experience at CERN stands out in his resume. He has already spoken to potential employers interested in considering his candidacy because of the CERN endorsement.

During his first trip to Europe and his first trip outside of the southwestern region of the United States, Vasquez took photography and took many photos in Zurich, Paris, Mont Blanc and other places.

To the student who hesitates to accept his type of internship, Vasquez offers words of encouragement.

“My mom would say the worst she can say to you is no,” he said. “Better to try and fail than to always wonder whether or not you could have gotten in. Even if you think you shouldn’t apply because your field isn’t primarily physics, there’s a place for you here. in terms of computer science, engineering, mathematics and other disciplines.

Selim Zoorob

Selim Zoorob. (UCR/Selim Zoorob)

Zoorob, 22, graduated at the beginning of the summer and was happy to have had the opportunity to spend three months at CERN. His journey there began when one day on campus he saw a post about the internship in the undergraduate physics section on iLearn.

“Going to CERN has always been a dream of mine and it was surreal when I applied for the internship,” he said. “It was a lot of work once we got there, which was the most exciting part of the trip.”

Zoorob has found it both humbling and inspiring to be part of an international team of scientists.

“I was able to be part of all the behind-the-scenes meetings and preparations,” he said. “It was fascinating to see how many ideas and moving parts came together to create a science experiment. It was amazing to see how science actually gets done in the real world.

Zoorob worked on two projects at CERN: “Radiation detected Zero to UltraLow-Field Nuclear Magnetic Resonance (RD-ZULF-NMR)” and “Liquid β-NMR studies of the interaction of Na and K cations with DNA G-quadruplex structures” .

“I was able to participate in the discussions surrounding the development of the RD-ZULF-NMR project, work on a section of the experimental setup and move this section to a hospital in Geneva,” he said. “For the Liquid β-NMR project, I participated in data collection and processing.”

According to Zoorob, the RD-ZULF-NMR project could revolutionize the field of biochemistry by offering a new visualization tool to study molecules. It could also benefit the medical field by making MRI machines more compact, affordable and safe.

“I often took the tram to visit Geneva – a car-free city with attractive local markets, many tourist attractions and museums,” he said. “I was amazed by the rich history of Geneva and visiting the Geneva Museum of Ethnography, or Museum of Ethnicity in Geneva, was my favorite part.”

For Zoorob, CERN will hold a place close to his heart because it taught him to work as a scientist and opened his mind to exploration.

“A certain sense of mystique can be found in every corner of CERN, from the library which exclusively contains books related to physics, to the marvelous laboratories that I had only seen before in textbooks,” he said. . “What is surprising at CERN is its sense of decentralization. There is no ‘main building’ but rather different facilities that come together to form a complex system. I was free and encouraged to explore this system that once seemed impossible to understand.

CERN internships for UCR students started in mid-June and ended in mid-August. Professors from the UCR Department of Physics and Astronomy who assisted and guided Caruso, Vasquez, and Zoorob are Yongtao Cui, Bill Gary, Owen Long, Flip Tanedo, and Stephen Wimpenny.

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Accelerator Operators: Pillars of Particle Physics https://polkinghorne.org/accelerator-operators-pillars-of-particle-physics/ Tue, 23 Aug 2022 14:03:45 +0000 https://polkinghorne.org/accelerator-operators-pillars-of-particle-physics/ Despite the fact that accelerator operators are essential to keeping an accelerator lab afloat, the role is largely unknown outside of physics, even to the people who end up in this position. “It was a kind of position that I didn’t know about or didn’t even know existed before,” says Judah O’Neil, who has worked […]]]>

Despite the fact that accelerator operators are essential to keeping an accelerator lab afloat, the role is largely unknown outside of physics, even to the people who end up in this position.

“It was a kind of position that I didn’t know about or didn’t even know existed before,” says Judah O’Neil, who has worked for the US Department of Energy’s Fermi National Accelerator Laboratory for two years. .

At Fermilab, accelerator operators are responsible for maintaining and operating the machines needed to deliver particle beams to all experiments around the lab.

It all starts with the 500-foot Linear Accelerator, or Linac, which operators use to kick a beam of protons for the first time. From the Linac, the proton beam heads to the Booster, a 1,500-foot circular accelerator that increases the energy of the beam. From there, operators can direct the beam to different parts of the complex, including Fermilab’s neutrino and muon experiments.

By directing protons from the Booster to a target, operators can create low-energy neutrino beams for neutrino experiments. Operators can also transfer a beam from the booster into the 2-mile-circumference recycler instead to alter its composition or produce muon beams for muon experiments. The transfer of protons from the recycler to the main injector, the next step in the line, allows operators to increase the energy even further. They use the Main Injector, also 2 miles in circumference, to produce the world’s highest intensity neutrino beam for long baseline neutrino experiments.

The PIP-II construction project, currently underway, will expand the capabilities of the entire accelerator complex with a brand new 700-foot superconducting linear accelerator.

All of this, as well as the maintenance of the different parts of the accelerator complex, goes through the accelerator operators in the main control room at Fermilab.

Each group of operators, led by a team leader, rotates day, evening and night to staff the control room 24/7. “[Having rotating shifts] allows you to get to know everyone and gain experience at different times of the day,” says O’Neil. “You can be in the control room and talk to the experts, see what’s going on and meet everyone.”

Working in the control room requires operators to perform multiple tasks. They must follow multiple monitors on their individual consoles, as well as larger screens that display general system status and weather radar across the room, as the accelerator complex can be affected by storms. Beeps, beeps, and other sound effects provide auditory cues that can cut through the noise of people entering to check access keys, notify operators of a problem, or simply drop in for a quick hello. If something goes wrong, the operators are the ones to investigate and fix the problem or find a more experienced operator who can.

Operators don’t learn to manage these responsibilities overnight. They follow a training period that lasts for their first two years of work.

“You’re not even assigned to a crew for your first month because you’ve just had initial training,” says Laura Bolt, who has been an operator since November 2021. “For the first year to two years that you’re here , your main goal is to complete this training and also be useful in the control room.

Once operators complete their on-the-job training, or OJT, they can then specialize in a specific area or help train new operators.

“When you start out, you do things, but it’s usually under supervision or you watch someone do something, so you learn how to do it,” says Cassidy Mayorga, who has been an operator for four years. “Then you slowly move on to doing it on your own, and then you do it to teach other people.”

Mayorga sits on the training committee and helps ensure training documentation is up to date.

FCE consists of studying instruction manuals and taking written tests, supplemented by in-person instruction from experienced operators.

Since much of an operator’s training comes from collaboration and hands-on supervisory experience, the pandemic has had a significant impact on Fermilab’s main control room. The usual hustle and bustle came to a halt as operators acclimated to new schedules and skeletal crew changes to allow for social distancing. “It was a big adjustment,” says Mayorga. “It was very quiet and a bit unnerving.”

For operators who were hired during the pandemic, the gradual lifting of restrictions and the more recent return to semi-normal day-to-day operations have given them a new appreciation for the expertise of their colleagues.

“It’s really good to have these conversations with the experts and to be able to have a lot of people in the control room at once because you get different opinions, you learn a lot of things,” O’Neil says.

Operators are a diverse group. Some of them knew they wanted to work at Fermilab from an early age, others came across the job by accident. There are writers, like Bolt; amateur astronomers, like O’Neil; and Ultimate Frisbee enthusiasts, like Mayorga. Many share at least one interest: video games.

Bolt, O’Neil, and Mayorga all say that being an operator is a great job for anyone interested in the practical elements of particle physics, including those who don’t plan to follow the usual path all the way through. a doctorate in physics. “The cool factor of this work is right off the charts,” Bolt says. “It’s the perfect place for non-traditional physics students.”

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Research Associate in Theoretical Particle Physics at ROYAL HOLLOWAY, UNIVERSITY OF LONDON https://polkinghorne.org/research-associate-in-theoretical-particle-physics-at-royal-holloway-university-of-london/ Tue, 23 Aug 2022 00:08:47 +0000 https://polkinghorne.org/research-associate-in-theoretical-particle-physics-at-royal-holloway-university-of-london/ Location: Egham Salary: £37,467 per year – including London allowance Post type: Full time Closing Date: 23:59 BST on Monday 05 September 2022 Reference: 0822-385 Full time, CDD Applications are invited for a Postdoctoral Research Associate in Theoretical Physics in the area of ​​Beyond the Standard Model and Astroparticle Physics, with an emphasis on the […]]]>

Location: Egham

Salary: £37,467 per year – including London allowance

Post type: Full time

Closing Date: 23:59 BST on Monday 05 September 2022 Reference: 0822-385

Full time, CDD

Applications are invited for a Postdoctoral Research Associate in Theoretical Physics in the area of ​​Beyond the Standard Model and Astroparticle Physics, with an emphasis on the theory and phenomenology of possible new light particles, including, for example, axions and axion-like particles. You must have a PhD in theoretical particle physics or a closely related field. The position is available to start immediately and is fixed term for 24 months.

The position is part of the “Quantum sensors for the hidden sector” project. The first year in this role will be at Royal Holloway with the second year in the Standard Model String and Beyond Phenomenology Group at the University of Liverpool. The successful candidate will be strongly encouraged to work with all theoretical members of the collaboration: Dr Edward Hardy (Liverpool), Prof John March-Russell (Oxford), Prof Stephen West (Royal Holloway), and to develop interactions with the members of the group.

The Quantum Sensors for the Hidden Sector Collaboration, webpage: https://qshs.shef.ac.uk, is an STFC-funded project to search for axions and axion-like particles using advanced quantum electronics and quantum measurement techniques. The collaboration works with the Axion Dark Matter Experiment (ADMX), which is currently the world leader in dark matter axion sensing. Our aim is to develop a new high frequency axion target to integrate into the existing ADMX device, as well as develop our own state-of-the-art research instrumentation for axion and ALP research in the UK. We are looking for postdoctoral researchers to support this program with experience in a range of fields across quantum electronics, microwave electronics, cryogenics, magnetic field physics, quantum systems theory and theory and particle phenomenology. They will join the collaboration as it embarks on this exciting new program of cutting-edge basic research in the UK.

In return, we offer a highly competitive rewards and benefits package including:

  • Generous annual leave
  • Training and development opportunities
  • Pension plan with generous employer contribution
  • Various programs, including Cycle to Work, subscription loans and help with the cost of eye tests.

For an informal discussion about the position, please contact Professor Stephen West on Stephen.West@rhul.ac.uk or Dr Ed Hardy on ehardy@liverpool.ac.uk.

To view more details about this position and to apply, please visit https://jobs.royalholloway.ac.uk and please include: 1) Curriculum Vitae, 2) List of publications, 3) Declaration of research interests. Please arrange for two letters of recommendation to be sent directly to Professor West via Stephen.West@rhul.ac.uk at the deadline.

Royal Holloway recognizes the importance of helping its employees balance work and personal life by offering flexible working arrangements.

Please cite the reference: 0822-385

Closing Date: 23:59, September 5, 2022

Date of interview: To confirm

We particularly welcome applications from women as they are underrepresented at this level in the Physics Department at Royal Holloway, University of London.

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