IT'S "THAT GODDAMN PARTICLE"
10 years after the discovery of the Higgs boson, physicists still can't get enough of the 'God particle'


By Keith Cooper published about 16 hours ago

"Particle physics has changed more in the past 10 years than in the previous 30 years."

An artist's depiction of a Higgs boson. (Image credit: Tobias Roetsch/Future Publishing via Getty Images)

Ten years ago, jubilant physicists working on the world's most powerful science experiment, the Large Hadron Collider (LHC) at CERN, announced the discovery of the Higgs boson — a particle that scientists had been searching for since 1964, when its existence was first predicted.

"For particle physicists, the Higgs boson was the missing piece of the Standard Model," Victoria Martin, a professor of particle physics at the University of Edinburgh in the U.K., told Space.com.

Although the Large Hadron Collider's remit is wide-ranging, searching for the Higgs boson was its top priority when it came online in 2010. The LHC's two key experiments — ATLAS (A Toroidal LHC Apparatus) and CMS (Compact Muon Solenoid) — detected the Higgs boson within just two years of beginning operations.

"We were not expecting to see the Higgs boson so quickly," CERN's Director-General, Fabiola Gianotti, said during a preview press conference held on Thursday (June 30). It was the LHC's superior computing infrastructure applied to experiments that performed better than their design specifications — testament to the many years of hard work put into building the LHC — that accelerated the Higgs boson's discovery, she said.


Related: 10 cosmic mysteries the Large Hadron Collider could unravel

Read more: Our original coverage of the Higgs discovery

The mystery of mass

The Higgs boson changed the world of particle physics, opening doors that had been slammed shut until its discovery.

"Particle physics has changed more in the past 10 years than in the previous 30 years," Gian Giudice, head of CERN's theoretical physics department, said during the event.

The Higgs boson is important because it carries the force of an energy field known as the Higgs field, in much the same way that a photon carries the force of the electromagnetic field.

"The field is more fundamental than the particles," Martin said. "It permeates all the way across space and time." It's the interaction between certain particles and the Higgs boson, which represents the Higgs field, that gives those particles their mass.

"Particle physics has changed more in the past 10 years than in the previous 30 years."— Gian Giudice

One analogy is to think of the Higgs field as a kind of cosmic treacle that slows down some particles more than others. Less massive particles pass through the Higgs field relatively effortlessly, and so they can fly off at the speed of light — think of electrons, which have a tiny mass, or photons, which have no mass at all. For other particles, wading through the cosmic treacle of the Higgs field slows them down, giving them more mass, and therefore these particles are the most massive.

Just like these particles, scientists believe — although they have yet to watch the process happen — that the Higgs boson also gets its mass from interacting with itself. And measurements by the LHC have shown that the Higgs boson has a high mass as well: 125 billion electronvolts, which is about 125 times more massive than one of the positively charged protons at an atom's core. (Thanks to Einstein's special relativity, particle physicists know that mass and energy are interchangeable and so refer to masses in terms of their energy.) Only one fundamental particle known to science is more massive.

Discovering the Higgs boson and measuring its mass was only the beginning. "We've spent the last 10 years testing the Higgs boson, because discovering it was one thing, but the Standard Model also tells us lots of things about the way the Higgs boson should behave," Martin said.



The ATLAS instrument at the Large Hadron Collider.

 (Image credit: CERN/Claudia Marcelloni/Max Brice)

An existential question


For one thing, the Higgs boson's quantum spin — or lack thereof — could provide an insight into why our universe even exists.

Every known particle has a quantum spin, except for the Higgs boson. The Standard Model of particle physics predicted this oddity, so it isn't a surprise, but scientists including Martin and her research team have continued trying to measure the spin of the Higgs boson as a way to test the Standard Model. So far, they've found no evidence that it has any spin.

The reason why the Higgs boson has no spin when every other known particle does is because of the nature of the Higgs field. Unlike the gravitational and electromagnetic fields, which have obvious sources such as an object's mass or an electric current passing through magnetic fields, the Higgs field has no source. It's just there, a non-localized part of the cosmos pervading everything. As such it is coupled to the 'vacuum,' the very fabric of space-time, and therefore the field shares the vacuum's properties. The vacuum has no quantum spin, and therefore neither does the Higgs boson.

However, the vacuum isn't inert. Particles fizz in and out of existence thanks to quantum fluctuations, raising the energy level of the vacuum above its lowest possible state. The thing about energy levels is that an object — be it a person in a gravitational field, an electron orbiting an atomic nucleus, or the vacuum — always prefers to be at its lowest possible energy level. Yet our universe is not. What keeps the universe from succumbing to the inevitable urge to drop energy levels is the shape of what scientists characterize as the energy potential of the Higgs field.

A graph of this energy potential would look like a 'mountain' in the middle, and two 'valleys' flanked by 'hills' on either side. The energy level of the vacuum would lie in one of those valleys, but physicists strongly suspect that on either side of those hills are even deeper 'valleys' representing even lower energy states. And the measurement of the mass of the Higgs boson supports this idea; the particle is so large that it suggests that there's room for the Higgs field to potentially decay to a lower energy level one day.

"The Higgs boson is a very precise microscope to study nature at the smallest scales, and at the same time it is a formidable telescope to access physics at very high energy scales."— Fabiola Gianotti

For this reason, physicists call our vacuum a 'false' vacuum, because it 'wants' to decay to a lower energy — a 'truer' vacuum. The valleys and hills of the Higgs field's energy potential are holding our universe in this false vacuum, long enough for planets, stars and galaxies to form.

However, over eons upon eons of time, the false vacuum is inherently unstable, and eventually it will decay. Maybe quantum energy fluctuations will allow the false vacuum to climb over those 'hills' and roll down the slope on the other side, or maybe the strange phenomenon of quantum tunneling will let it drill through the 'hill' that is the energy barrier.

However it happens, it would be bad for the universe — the decay of the false vacuum would expand outward in a wave moving at the speed of light, destroying everything and replacing it all with a true vacuum. It's only the Higgs field that is holding vacuum decay at bay, so we therefore have the Higgs field to thank for our current universe

A schematic of one of the proton-proton collisions at the LHC that revealed the Higgs boson decaying into daughter particles.

 (Image credit: CERN/CMS Collaboration/Thomas McCauley/Lucas Taylor)

Another run at understanding the universe

In addition to the Higgs boson's spin, researchers have spent the past decade trying to pin down its life span. The Higgs boson existence is fleeting; the standard model predicts that a Higgs boson survives for a tiny amount of time, just 10^–22 seconds, before breaking apart into more subatomic particles. However, this calculation hasn't been experimentally verified yet. "It happens so quickly," Martin said.

THEY ARE ABOUT TO CHANGE QUANTUM REALITY, AGAIN
Physicists hope that the next operational phase on the LHC, dubbed Run 3 and beginning on Tuesday (July 5), will serve as the much sought-after stopwatch.

"We hope that in an indirect way we might be able to make a measurement of how long the Higgs boson is living for," Martin said. "If we can measure the lifetime it will give us more constraints on what particles the Higgs boson is decaying into."

In turn, understanding how the Higgs boson breaks apart into other particles could reveal hidden subatomic particles new to science, perhaps even including particles of mysterious dark matter.

Because of these implications, Gianotti described the Higgs boson as a crucial tool for probing the deepest mysteries of particle physics. "The Higgs boson is a very precise microscope to study nature at the smallest scales, and at the same time it is a formidable telescope to access physics at very high energy scales," she said.

The discovery of the Higgs boson hasn't just allowed physicists to tick another particle off the list. Its very existence and its behavior raise questions about some of the most profound areas of fundamental physics: the structure of matter in the universe, the fate of the universe, whether the universe is stable, and how elementary particles relate to each other.

RELATED STORIES:
— Higgs boson: The 'God Particle' explained
— The Large Hadron Collider: Inside CERN's atom smasher
— The Higgs boson could have kept our universe from collapsing

However, the Higgs boson continues to play coy with its secrets. "Everything that we've seen so far seems to be just what the Standard Model predicted," Martin said. "While this is interesting, it is also slightly disappointing because we were hoping that the Higgs boson might help us see beyond the Standard Model."

Far from breaking the rules and destroying physics, moving beyond the Standard Model is necessary to explain phenomena that doesn't fit, such as dark matter, or opening doorways into new physics, such as supersymmetry. It's why, fresh off four years of upgrades, the LHC will once again tackle the mysteries of the Higgs boson.


Follow Keith Cooper on Twitter @21stCenturySETI. Follow us on Twitter @Spacedotcom and on Facebook.
Keith Cooper (opens in new tab)

Contributing writer
Keith Cooper is a freelance science journalist and editor in the United Kingdom, and has a degree in physics and astrophysics from the University of Manchester. He's the author of "The Contact Paradox: Challenging Our Assumptions in the Search for Extraterrestrial Intelligence" (Bloomsbury Sigma, 2020) and has written articles on astronomy, space, physics and astrobiology for a multitude of magazines and websites.

Particle physics: A decade of Higgs boson research

Nature

July 4, 2022

Ten years after the first reported observation of the Higgs boson at the CERN Large Hadron Collider, the most up-to-date results of the properties of this elementary particle from the ATLAS and CMS collaborations are presented in two papers published Nature.

In July 2012, the ATLAS and CMS collaborations announced that they had found a particle with properties that matched those expected for the Higgs boson. Since then, more than 30 times as many Higgs bosons have been detected, offering the opportunity to verify if its behaviour matches up with the standard model of elementary particle physics.

The two collaborations present an analysis of data produced within Run 2 of the Large Hadron Collider (between 2015 and 2018) that involve production or decay of Higgs bosons. The key question investigated by the researchers is how the Higgs boson interacts with other elementary particles. According to the theory from the standard model of particle physics, the strength with which any particle interacts with the Higgs boson should be proportional to the particle mass. Ten years of data allow the two collaborations to estimate, within reasonable errors, the Higgs interaction with the heaviest known particles: top and bottom quarks, Z and W bosons and tau lepton. For all these particles the data fall precisely in line, within experimental errors, of the behaviour predicted by the standard model of elementary particle physics.

The progress made over the past decade is predicted to continue over the next one. Some of the key properties of the Higgs boson, such as coupling to itself or to lighter particles, remain to be measured and potentially reveal deviations from theory. However, the current dataset is expected to more than double during the next decade of research, which will help to improve our understanding of Higgs boson physics.

The progress made in the past decade, what remains to be established, and potential future explorations are discussed in a Perspective by Giulia Zanderighi and colleagues.

doi:10.1038/s41586-022-04893-w

SEE LA REVUE GAUCHE - Left Comment: Search results for HIGGS BOSON 

A THEORY IN SEARCH OF EVIDENCE

Dark matter: Why we keep searching for something that may not even exist

Our understanding of the universe keeps improving. But there's a huge invisible force out there called dark matter and we're virtually clueless about it.

Astrophysicists say the James Webb Space Telescope may help them detect,

 if not see, dark matter in the universe

It has never been detected, only speculated. But scientists estimate that up to 85% of the matter in the universe could be made of what's called dark matter.

Scientists cannot define dark matter with any certainty, but that hasn't stopped the search for it. Our largest and newest space-based telescope, the James Webb Space Telescope is on the case.

It was barely moments after the first images taken by the telescope had been released on July 12, 2022, when Kai Noeske said something both mysterious and true.

Noeske, an astronomer at the European Space Observation Centre (ESOC) in Darmstadt, Germany, was pointing to an image of Stephan's Quintet, a group of five galaxies, as they have never been seen before.

Astronomer Kai Noeske looked at the image of Stephan's Quintet and said:

 "There is a lot out there that we do not know [...] One of those things could be dark matter."

And he said: "There is a lot out there that we do not know. And we do not know what we do not know. [But] one of those things could be dark matter." 

An accidental discovery

In the 19th century, Lord Kelvin, a Scottish-Irish physicist, wanted to estimate the mass of our galaxy, the Milkyway, using data on how fast stars moved around the galaxy's core.

But Kelvin found discrepancies or anomalies in the data, things which could not be explained and were attributed to "dark bodies" that we cannot see.

"The galaxy seems to be rotating much faster than it should, based on estimates," explained Tevong You, a theorist at CERN, the European Organization for Nuclear Research.

The Large Hadron Collider is the world's most powerful particle accelerator

The theory is that there is an "invisible matter" responsible for the speed at which our galaxy rotates, said You. And that may be true of other galaxies as well.

Stars have been observed to travel at higher-than-estimated speeds, especially at the edges of galaxies. And that is weird.

Stars should cut loose and 'fly off'

Imagine you attached a stone to a string, and you rotated it at high speed. The stone would cut loose and fly off if it reached a speed higher than a certain threshold — a point at which the string becomes too weak to hold onto the stone, as the stone picks up speed and gains more force.

But astronomers have observed stars that continue to spin around the center of the galaxy, even when the string holding them to the galaxy, as it were, should have ripped, and the stars should have "flown off".

The astronomers' only explanation is that there must be some invisible matter holding the stone in range. Perhaps it's this elusive dark matter?

That remains an unanswered question. And there are many other anomalies, such as the shape of some galaxies, including our Milkyway, that are so far unexplained.

We can't see dark matter but we may see its effects

Scientists say that the reason we are unable to see or detect this invisible matter is that it does not interact with electromagnetic forces — things like visible light, X-ray or radio waves.

They argue that we can, however, observe some of the effects of dark matter through its gravitational force.

But we still want to detect dark matter in its own right. And here's where CERN's Large Hadron Collider comes in. Tevong You and other researchers at CERN think the LHC is our best chance of detecting dark matter.

When particles collide at the LHC, the resulting debris gets caught in detectors

 such as this one. This is a illustrating one of the LHC's detectors.

A decade ago, experiments at the LHC proved the Standard Model of particle physics by detecting the Higgs boson particle — a particle which itself had long proved to be elusive.

The Standard Model is the idea that everything in the universe is made of a few fundamental particles and that those are governed by four fundamental forces — the strong force, the weak force, the electromagnetic force, and the gravitational force.

Tevong You said that the LHC could help solve the mystery of dark matter. But even now, You suspects that dark matter will be nothing like the particles we know from the Standard Model.

"It has to interact very weakly. It can't interact with light or electromagnetism. It can't interact with the strong force, and it may interact through the weak force that causes radioactivity," said You.

If that reads like a riddle, you're not alone. Scientists are still trying to work it out themselves.

Measuring dark matter by what's missing

The Large Hadron Collider smashes particles together to create collisions. The collisions produce a debris that gets caught by particle detectors.

It's just the same as if you smashed two apples together, bits would spray in all directions and get caught on the walls and floor. Those bits of apple would still be fruit, but they would have also become somewhat different. Even so, if we then collected all the bits of apple, including the juices, we would theoretically have all the bits to reconstruct those two original apples.

And the same is true of fundamental particles. We smash them up, they split and spray against the LHC detectors, and if we piece them back together, we should be able to account for all the bits that made those original particles.  

But if after all that, we find that there is something missing... especially missing energy or mass, as energy is also known... Well, when it comes to particle physics, scientists tend to think that there would have to be some dark, or invisible, matter — elements that we can't see, but which are very much part of the whole thing.

Andre David is an experimental physicist at CERN who builds particle detectors and says that if there is missing energy after a collision, it is likely that that energy has been transferred to dark matter. 

"The Higgs boson interacts with all the other elements that have mass. And so dark matter must [also] have mass in order to fulfill the effect that we see in the galaxies," said David.

New theories about dark matter

Some scientists argue that if there were invisible forces in the universe, we would have found them already and that, given that we haven't detected those forces, they suggest we should think outside of the Standard Model.

One of those scientists is the physicist Mordehai Milgrom. Milgrom has developed an alternative theory of gravity, one that suggests that gravitational force operates differently at different distances from the core of a galaxy.

While Newton's theory of gravity explains most large-scale movements in the cosmos, Milgrom's Modified Newtonian Dynamics suggests that a force acts differently when it is weak, such as at the edge of a galaxy.

Advocates of the theory say it predicts the rotation of galaxies and the speed of the stars better than Newton's theory.

But we still don't know whether we will ever discover dark matter or prove Milgrom's Modified Newtonian Dynamics. What we do know is that our understanding of the universe is far from complete.

Edited by: Zulfikar Abbany

INSIDE THE COSMOS: JAMES WEBB SPACE TELESCOPE CONTINUES TO DAZZLE
Spinning wormholes
Webb recently peered into a wormhole in the mysterious-looking "Phantom Galaxy." Scientists believe the dust lanes spiral towards an intermediate-mass black hole at the heart of the galaxy.
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The 5 biggest scientific breakthroughs of 2022: Fusion energy, ‘life after death’, and more

Scientific Breakthroughs of the Year: 

From a breakthrough in nuclear fission energy technology to pigs being "revived" after their death, here are some of the biggest scientific breakthroughs that happened in 2022.

Written by Sethu Pradeep
New Delhi | Updated: December 17, 2022 

Scientific Discoveries of 2022: The year 2022 bore witness to many impressive scientific breakthroughs including the simulation of a wormhole to an artificial mouse embryo that developed a brain. 

(Image credit: Indian Express)

A major US breakthrough in nuclear fusion technology gave us a glimpse of a future where a renewable, clean and near-limitless source of energy might just be possible. This breakthrough capped off an exciting year for science, which bore witness to many scientific developments that promise to alter the course of humanity and our understanding of the universe. Here, we have put together five of the most significant scientific developments that happened this year.

Fusion energy breakthrough promises future of clean energy

Scientists announced on Tuesday (December 13) that researchers at the Lawrence National Laboratory in California conducted a nuclear fission reaction that produced more energy than what was used to ignite it. This marks a major breakthrough for the field. Nearly all the energy on the planet comes from nuclear fusion energy. Many of the energy sources that we know, from the food we eat to the fossil fuels that we burn, can be traced back to nuclear fission reactions that happen in the Sun. But we are still years, and maybe decades away, from mastering the process ourselves.

The conventional nuclear electric plants that we know and nuclear weapons derive their energy from a nuclear fission process, where the nucleus of an atom, usually Uranium, is split into two different nuclei, generating large amounts of energy.

Also read |Why fusion could be a clean-energy breakthrough

In an almost contrary process, nuclear fusion is when two nuclei fuse together to form a single heavier nucleus. When this happens, the mass of the new heavier nucleus is less than the sum of the individual nuclei combined, meaning that a little bit of mass is lost. E=MC^2, Einstein’s most famous equation, explains how this mass is converted into a large amount of energy.

While both fission and fusion reactions release large amounts of energy, the latter produces substantially more energy than the former. For example, the nuclear fusion of two nuclei of a heavier hydrogen isotope will produce four times as much energy as the fission of a uranium atom.

If nuclear fission energy were to be commercialised, it would offer a clean and renewable source of energy that will help fight climate change, while also not producing the panoply of radioactive waste products that fission energy reactors are known for. The technology still has a long way to go before becoming a viable energy alternative, as fusion reactions currently being tested barely last a few minutes, due to the difficulty in maintaining the conditions required for the reactions to happen.
Large hadron collider gets back into action, producing almost immediate results

After a hiatus of over three years for maintenance and upgrades, the world’s largest particle accelerator, the large hadron collider (LHC), got back into action in April this year. This marked the beginning of the third run of LHC, when scientists will collect data from an unparalleled number of particle collisions happening at unprecedented energy levels.

The LHC did not take long after starting up again to deliver impressive new science. In July this year, CERN (European Organization for Nuclear Research) announced the discovery of three new exotic particles—a new pentaquark and a pair of new tetraquarks— using the particle accelerator.

Also read |“Everyone wants to look for a signal that goes beyond the standard physics model”: Scientist at Large Hadron Collider

“The newly-discovered pentaquark is still a baryon, but with the three quarks, it has an extra pair consisting of a quark and an anti-quark. The two tetraquarks are within the family of mesons, but instead of having pairs of quarks and anti-quarks, it has two pairs of quarks. These states were predicted in the nominal quark model introduced in the sixties, but these states were not found until now,” said Nicola Neri, a senior member of the LHCb (LHC beauty) experiment, to indianexpress.com at the time.

During its third run, the unrivalled number of collisions in LHC will allow physicists from around the world to study the Higgs boson particle in great detail, while also putting the “Standard model of particle physics” through its most rigorous tests yet.

“Baby wormhole” simulated in a quantum computer

Since they were first proposed by Albert Einstein and Nathan Rosen in 1935, wormholes have remained in the realm of speculative science fiction. Wormholes, or Einstein-Rosen bridges, are theoretical structures that can be considered a tunnel with two ends at different points in space-time. This tunnel could be connecting two points at large or small distances, or two different points in time.

Now, scientists have brought wormholes out of the worlds of “Interstellar” and “Star Trek” and have brought it into this world that we live in. Well, sort of. Researchers at the California Institute of Technology (CalTech) created two simulated black holes in a quantum computer and transmitted a message between them, essentially creating a tunnel in space-time.

While the researchers did not create a rupture in space and time in physical space, it appeared a traversable wormhole was formed based on quantum information “teleported” using quantum codes on the quantum computer.

“There’s a difference between something possible in principle and possible in reality. So don’t hold your breath about sending your dog through the wormhole. But you have to start somewhere. And I think it’s exciting that we can get our hands on this at all,” said Fermilab physicist and study co-author Joseph Lykken to Reuters, at the time.

While it may be a long time before we can send a person, or indeed, their dog, through a wormhole, this research still represents an important breakthrough. Scientists have long pursued a better understanding of these wormholes, and the new research will help them make progress towards that goal.

“Reversing death” by reviving pig cells

From the Greek mythological figure Achilles to the Hindu mythological figure Hiranyakashipu, who was killed by Narasimha, the quest for immortality is a tale as old as time. But new research published in the journal Nature this August by Yale scientists plays with that notion of immortality.

The New York Times reported how scientists pumped a custom-made solution called OrganEx into dead pigs’ bodies using a device similar to the heart-lung machines used in hospitals. As the machine began circulating the solution into the cadavers’ veins and arteries, its brain, heart, liver and kidney cells began functioning again. Also, the cadavers never got stiff, unlike typical dead bodies.

Even though the seemingly dead cells seemed revived, the pigs were not conscious. While this experiment was far off from immortality and actually reversing death, it opens up important questions about the scientific division between life and death.

One of the main goals of the researchers is to increase the supply of human organs for transplant in the future by letting doctors obtain viable organs long after a patient has died. They also hope this technology could be used to prevent severe damage to organs like the heart after a major heart attack or the brain after a stroke.

The OrganEx solution used by researchers consisted of nutrients, anti-inflammatory medications, drugs to prevent cell death, and interestingly, nerve blockers—substances that dampen the activity of neurons and prevent the possibility of the pigs regaining consciousness.

But what if the solution did not contain nerve blockers? Would the brains of the pigs be revived, essentially reanimating them from death? Well, these are questions that the researchers are still yet to answer. But any research in this direction will be burdened by many ethical considerations, apart from the scientific challenges.

Synthetic mouse embryo develops a beating heart

In another scientific breakthrough that will have you questioning what life means, the University of Cambridge and Caltech created an artificial embryo without using any sperm or egg cells. The embryo created using mouse stem cells developed a brain, a beating heart, and the foundations for all the other organs in the body, according to the University of Cambridge.

The stem cells are the body’s master cells and can develop into almost any of the many cell types in the body. The researchers mimicked the natural processes that happen at conception and guided three types of stem cells found in early mammalian development till they began interacting. They established a unique environment for their interactions and got the stem cells to talk to each other.

Due to this, the stem cells organised themselves into structures and progressed through developmental stages until the embryos had beating hearts and the foundations of the brain, along with the yolk sac from which embryos get nutrients in the first weeks. Unlike other synthetic embryos developed in the past, the researchers’ embryos reached the point where the entire brain began to develop.

“Our mouse embryo model develops not only a brain, but also a beating heart, all the components that make up the body. It’s unbelievable that we’ve got this far. This has been the dream of our community for years, and a major focus of our work for a decade, and finally we’ve done it,” said Magdalena Zernicka-Goetz, corresponding author of a research article published in the journal Nature.

This research was carried out on mice, but the researchers hope the technology can be used to develop certain human organ types. This research helps them understand the crucial organ development processes that could not be done with real human embryos. The “14-day rule” in the United Kingdom and other countries prevents scientists from studying human embryos in laboratory conditions.

But further investigating this science could potentially lead to a future where individual human organs can be grown in laboratory settings using stem cells, so that they can be transplanted to a human patient.

If the Higgs can reach the Hidden Valley, we will see new physics already in next-generation accelerators

Peer-Reviewed Publication

THE HENRYK NIEWODNICZANSKI INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCES

 

IMAGE: THE SEARCH FOR EXOTIC HIGGS BOSON DECAYS IN FUTURE LEPTON COLLIDERS: 1) AN ELECTRON AND A POSITRON FROM OPPOSING BEAMS COLLIDE; 2) THE COLLISION PRODUCES A HIGH-ENERGY HIGGS BOSON; 3) THE BOSON DECAYS INTO TWO EXOTIC PARTICLES MOVING AWAY FROM THE AXIS OF THE BEAMS; 4) EXOTIC PARTICLES DECAY INTO PAIRS OF QUARK-ANTIQUARK, VISIBLE TO DETECTORS. view more 

CREDIT: SOURCE: IFJ PAN

It may be that the famous Higgs boson, co-responsible for the existence of masses of elementary particles, also interacts with the world of the new physics that has been sought for decades. If this were indeed to be the case, the Higgs should decay in a characteristic way, involving exotic particles. At the Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow, it has been shown that if such decays do indeed occur, they will be observable in successors to the LHC currently being designed.

When talking about the 'hidden valley', our first thoughts are of dragons rather than sound science. However, in high-energy physics, this picturesque name is given to certain models that extend the set of currently known elementary particles. In these so-called Hidden Valley models, the particles of our world as described by the Standard Model belong to the low-energy group, while exotic particles are hidden in the high-energy region. Theoretical considerations suggest then the exotic decay of the famous Higgs boson, something that has not been observed at the LHC accelerator despite many years of searching. However, scientists at the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow argue that Higgs decays into exotic particles should already be perfectly observable in accelerators that are successors to the Large Hadron Collider – if the Hidden Valley models turn out to be consistent with reality.

“In Hidden Valley models we have two groups of particles separated by an energy barrier. The theory is that there could then be exotic massive particles which could cross this barrier under specific circumstances. The particles like Higgs boson or hypothetic Z’ boson would act as communicators between the particles of both worlds. The Higgs boson, one of the most massive particle of the Standard Model, is a very good candidate for such a communicator,” explains Prof. Marcin Kucharczyk (IFJ PAN), lead author of an article in the Journal of High Energy Physics, which presents the latest analyses and simulations concerning the possibility of detecting Higgs boson decays in the future lepton accelerators.

The communicator, after passing into the low energy region, would decay into two rather massive exotic particles. Each of these would, in picoseconds – that is, trillionths of a second – decay into another two particles, with even smaller masses, which would then be within the Standard Model. So what signs would be expected in the detectors of future accelerators? The Higgs itself would remain unnoticed, as would the two Hidden Valley particles. However, the exotic particles would gradually diverge and eventually decay, generally into quark-antiquark beauty pairs visible in modern detectors as jets of particles shifted from the axis of the lepton beam 

“Observations of Higgs boson decays would therefore consist of searching for the jets of particles produced by quark-antiquark pairs. Their tracks would then have to be retrospectively reconstructed to find the places where exotic particles are likely to have decayed. These places, professionally called decay vertices, should appear in pairs and be characteristically shifted with respect to the axis of the colliding beams in the accelerator. The size of these shifts depends, among other things, on masses and average lifetime of exotic particles appearing during the Higgs decay”, says Mateusz Goncerz, M.Sc. (IFJ PAN), co-author of the paper in question.

The collision energy of protons at the LHC, currently the world's largest particle accelerator, is up to several teraelectronvolts and is theoretically sufficient to produce Higgs capable of crossing the energy barrier that separates our world from the Hidden Valley. Unfortunately, protons are not elementary particles – they are composed of three valence quarks bound by strong interactions, capable of generating huge numbers of constantly appearing and disappearing virtual particles, including quark-antiquark pairs. Such a dynamic and complex internal structure produces huge numbers of secondary particles in proton collisions, including many quarks and antiquarks with large masses. They form a background in which it becomes practically impossible to find the particles from the exotic Higgs boson decays that are being sought.

The detection of possible Higgs decays to these states should be radically improved by accelerators being designed as successors to the LHC: the CLIC (Compact Linear Collider) and the FCC (Future Circular Collider). In both devices it will be possible to collide electrons with their anti-material partners, the positrons (with CLIC dedicated to this type of collision, while FCC will also allow collisions of protons and heavy ions). Electrons and positrons are devoid of internal structure, so the background for exotic Higgs boson decays should be weaker than at the LHC. Only will it be sufficiently so to discern the valuable signal?

In their research, physicists from the IFJ PAN took into account the most important parameters of the CLIC and FCC accelerators and determined the probability of exotic Higgs decays with final states in the form of four beauty quarks and antiquarks. To ensure that the predictions cover a wider group of models, the masses and mean lifetimes of the exotic particles were considered over suitably wide ranges of values. The conclusions are surprisingly positive: all indications are that, in future electron-positron colliders, the background of exotic Higgs decays could be reduced even radically, by several orders of magnitude, and in some cases could even be considered negligible.

The existence of particle-communicators is not only possible in Hidden Valley models, but also in other extensions of the Standard Model. So if the detectors of future accelerators register a signature corresponding to the Higgs decays analysed by the Cracow researchers, this will only be the first step on the road to understanding new physics. The next will be to collect a sufficiently large number of events and determine the main decay parameters that can be compared with the predictions of theoretical models of the new physics.

“The main conclusion of our work is therefore purely practical. We are not sure whether the new physics particles involved in Higgs boson decays will belong to the Hidden Valley model we used. However, we have treated this model as representative of many other proposals for new physics and have shown that if, as predicted by the model, the Higgs bosons decay into exotic particles, this phenomenon should be perfectly visible in those electron and positron colliders which are planned to be launched in the near future”, concludes Prof. Kucharczyk.

The research in question was funded by an OPUS grant from the Polish National Science Centre.

The Henryk Niewodniczański Institute of Nuclear Physics (IFJ PAN) is currently one of the largest research institutes of the Polish Academy of Sciences. A wide range of research carried out at IFJ PAN covers basic and applied studies, from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly publication output of IFJ PAN includes over 600 scientific papers in high-impact international journals. Each year the Institute hosts about 20 international and national scientific conferences. One of the most important facilities of the Institute is the Cyclotron Centre Bronowice (CCB), which is an infrastructure unique in Central Europe, serving as a clinical and research centre in the field of medical and nuclear physics. In addition, IFJ PAN runs four accredited research and measurement laboratories. IFJ PAN is a member of the Marian Smoluchowski Kraków Research Consortium: "Matter-Energy-Future", which in the years 2012-2017 enjoyed the status of the Leading National Research Centre (KNOW) in physics. In 2017, the European Commission granted the Institute the HR Excellence in Research award. As a result of the categorization of the Ministry of Education and Science, the Institute has been classified into the A+ category (the highest scientific category in Poland) in the field of physical sciences.

SCIENTIFIC PUBLICATIONS:

“Search for exotic decays of the Higgs boson into long-lived particles with jet pairs in the final state at CLIC”

M. Kucharczyk, M. Goncerz

Journal of High Energy Physics, 131, 2023

DOI: https://doi.org/10.1007/JHEP03(2023)131

LINKS:

http://www.ifj.edu.pl/

The website of the Institute of Nuclear Physics, Polish Academy of Sciences.

http://press.ifj.edu.pl/

Press releases of the Institute of Nuclear Physics, Polish Academy of Sciences.

IMAGES:

IFJ230518b_fot01s.jpg                                 

HR: http://press.ifj.edu.pl/news/2023/05/18/IFJ230518b_fot01.jpg

The search for exotic Higgs boson decays in future lepton colliders: 1) an electron and a positron from opposing beams collide; 2) the collision produces a high-energy Higgs boson; 3) the boson decays into two exotic particles moving away from the axis of the beams; 3) exotic particles decay into pairs of quark-antiquark, visible to detectors. (Source: IFJ PAN)

---

JOURNAL

Journal of High Energy Physics

DOI

10.1007/JHEP03(2023)131 

ARTICLE TITLE

Search for exotic decays of the Higgs boson into long-lived particles with jet pairs in the final state at CLIC

ARTICLE PUBLICATION DATE

17-Mar-2023

Demystifying vortex rings in nuclear fusion, supernovae

A mathematical model linking these vortices with more pedestrian types, like smoke rings, could help engineers control their behavior in power generation and more

Peer-Reviewed Publication

UNIVERSITY OF MICHIGAN

Images

Better understanding the formation of swirling, ring-shaped disturbances—known as vortex rings—could help nuclear fusion researchers compress fuel more efficiently, bringing it closer to becoming a viable energy source. 

The model developed by researchers at the University of Michigan could aid in the design of the fuel capsule, minimizing the energy lost while trying to ignite the reaction that makes stars shine. In addition, the model could help other engineers who must manage the mixing of fluids after a shock wave passes through, such as those designing supersonic jet engines, as well as physicists trying to understand supernovae.

"These vortex rings move outward from the collapsing star, populating the universe with the materials that will eventually become nebulae, planets and even new stars—and inward during fusion implosions, disrupting the stability of the burning fusion fuel and reducing the efficiency of the reaction," said Michael Wadas, a doctoral candidate in mechanical engineering at U-M and corresponding author of the study.

"Our research, which elucidates how such vortex rings form, can help scientists understand some of the most extreme events in the universe and bring humanity one step closer to capturing the power of nuclear fusion as an energy source," he said.

Nuclear fusion pushes atoms together until they merge. This process releases several times more energy than breaking atoms apart, or fission, which powers today's nuclear plants. Researchers can create this reaction, merging forms of hydrogen into helium, but at present, much of the energy used in the process is wasted.

Part of the problem is that the fuel can't be neatly compressed. Instabilities cause the formation of jets that penetrate into the hotspot, and the fuel spurts out between them—Wadas compared it to trying to squish an orange with your hands, how juice would leak out between your fingers. 

Vortex rings that form at the leading edge of these jets, the researchers have shown, are mathematically similar to smoke rings, the eddies behind jellyfish and the plasma rings that fly off the surface of a supernova.

Perhaps the most famous approach to fusion is a spherical array of lasers all pointing toward a spherical capsule of fuel. This is how experiments are set up at the National Ignition Facility, which has repeatedly broken records for energy output in recent years. 

The energy from the lasers vaporizes the layer of material around the fuel—a nearly perfect, lab-grown shell of diamond in the latest record-setter in December 2022. When that shell vaporizes, it drives the fuel inward as the carbon atoms fly outward. This generates a shockwave, which pushes the fuel so hard that the hydrogen fuses.

While the spherical fuel pellets are some of the most perfectly round objects humans have ever made, each has a deliberate flaw: a fill tube, where the fuel enters. Like a straw stuck in that crushed orange, this is the most likely place for a vortex-ring-led jet to form when the compression starts, the researchers explained.

"Fusion experiments happen so fast that we really only have to delay the formation of the jet for a few nanoseconds," said Eric Johnsen, an associate professor of mechanical engineering at U-M, who supervised the study.

The study brought together the fluid mechanics expertise of Wadas and Johnsen as well as the nuclear and plasma physics knowledge in the lab of Carolyn Kuranz, an associate professor of nuclear engineering and radiological sciences.

"In high-energy-density physics, many studies point out these structures, but haven’t clearly identified them as vortex rings," said Wadas.

Knowing about the deep body of research into the structures seen in fusion experiments and astrophysical observations, Wadas and Johnsen were able to draw on and extend that existing knowledge rather than trying to describe them as completely new features.

Johnsen is particularly interested in the possibility that vortex rings could help drive the mixing between heavy elements and lighter elements when stars explode, as some mixing process must have occurred to produce the composition of planets like Earth.

The model can also help researchers understand the limits of the energy that a vortex ring can carry, and how much fluid can be pushed before the flow becomes turbulent and harder to model as a result. In ongoing work, the team is validating the vortex ring model with experiments. 

The research is funded by Lawrence Livermore National Laboratory and the Department of Energy, with computational resources provided by the Extreme Science and Engineering Discovery Environment through the National Science Foundation and the Oak Ridge Leadership Computing Facility.

Study: Saturation of vortex rings ejected from shock-accelerated interfaces. (DOI: 10.1103/PhysRevLett.130.194001)

JOURNAL

Physical Review Letters

DOI

10.1103/PhysRevLett.130.194001 

Europe’s CERN takes first steps toward building giant particle accelerator

Nuclear research organization says goal of Future Circular Collider is to ‘push the energy and intensity frontiers’ of particle smashers ‘in the search for new physics’

By AGNÈS PEDRERO

22 April 2023, 

A radio frequency particle accelerator is displayed in an exhibition during a press tour at the European Organization for Nuclear Research (CERN) on the Future Circular Collider (FCC) feasibility study, in Geneva, on April 19, 2023. (Fabrice Coffrini/AFP)

GENEVA (AFP) — Europe’s CERN laboratory has taken its first steps toward building a huge new particle accelerator that would eclipse its Large Hadron Collider — and hopes to see light at the end of the tunnel.

The Future Circular Collider (FCC) particle smasher would be more than triple the length of the LHC, already the world’s largest and most powerful particle collider, constructed in the hope of revealing secrets about how the universe works.

The FCC would form a new circular tunnel under France and Switzerland, 91 kilometers (56.5 miles) long and about five meters (16 feet) in diameter.

“The goal of the FCC is to push the energy and intensity frontiers of particle colliders, with the aim of reaching collision energies of 100 tera electron volts, in the search for new physics,” CERN says.

The tunnel would pass under the Geneva region and its namesake lake in Switzerland, and loop around to the south near the picturesque French town of Annecy.
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Eight technical and scientific sites would be built on the surface, with seven in France and one in Geneva, CERN engineer Antoine Mayoux told reporters this week.

CERN Radio-frequency head Eric Montesinos gestures next to a map of the actual Large Hadron Collider (LHC) during a press trip at the European Organization for Nuclear Research CERN on the Future Circular Collider (FCC) feasibility study, in Geneva, on April 19, 2023. (Fabrice Coffrini/AFP)

After carrying out a theoretical analysis, “we are now embarking for the first time on field activities” to study potential environmental issues, he said, with seismic and geotechnical studies to follow.
Mysteries of the universe

Once the feasibility studies are completed, CERN’s member states — 22 European countries plus Israel — will decide in the next five to six years on whether to build the FCC.

The FCC would accelerate electrons and positrons until 2060, and then hadrons until 2090, as it seeks answers to many remaining questions of fundamental physics, with about 95 percent of the mass and energy of the universe still a mystery.

CERN’s Large Hadron Collider — a 27-kilometer (17-mile) ring running about a hundred meters below ground — has already begun chipping away at the unknown.

Among other things, it was used to prove the existence of the Higgs Boson — dubbed the God particle — which broadened the understanding of how particles acquire mass, and earned two scientists who had theorized its existence the 2013 Nobel physics prize.

A simulated data projection of a Higgs boson collision. (Photo credit: CC BY Wikipedia)

But the LHC, which began operating in 2010, is expected to have run its course by around 2040.

“The problem with accelerators is that at some point, no matter how much data you accumulate, you hit a wall of systematic errors,” CERN physicist Patrick Janot said.

“Around 2040-2045, we will have taken away all the substance of the precision possible with the LHC,” he said.

“It will be time to move on to something much more powerful, much brighter, to better see the contours of the physics that we are trying to study.”
Opening doors to the future

Some researchers fear that this huge project will gobble up funds that could be used for other, less abstract physics research.

But others insist that pushing fundamental physics forward is vital for advances in applied physics as well.

“The benefits of our research are extremely important,” said Malika Meddahi, CERN’s deputy director for accelerators and technology, citing as examples medical imaging and the fight against tumors.

Janot agreed: “The day the electron gun was invented, it was the beginning of accelerators; we didn’t know it was going to give rise to television. The day general relativity was discovered, we didn’t know it was going to be used to run GPS.”

A projection on fundamental particles is seen during a press trip at the European Organization for Nuclear Research CERN on the Future Circular Collider (FCC) feasibility study, in Geneva, on April 19, 2023. (Fabrice Coffrini/AFP)

Harry Cliff, a particle physicist at Britain’s University of Cambridge, acknowledged that the FCC was an “expensive bit of kit.”

But he noted that it would be built by “a large international collaboration of nations working together over a very long period of time.”

“Particle physics isn’t about discovering new particles — it’s about understanding the fundamental ingredients of nature and the laws that govern them.”

Competition from China

More than 600 institutes and universities around the world use CERN’s facilities, and are responsible for funding and carrying out the experiments they take part in.

However, CERN has some competition: China announced in 2015 that it intended to start work within a decade on building the world’s largest particle accelerator.

Michael Benedikt, who is heading up the FCC feasibility studies, told AFP that CERN had more than 60 years of experience in developing long-lasting research infrastructure.

And political stability in Europe helped to “minimize the development risk for such long-term projects,” he said.

Meddahi also highlighted Europe’s leading position in the field, but warned that “China displays the same ambition.”

“Let’s be vigilant and be sure that we are not on the verge of a change in this hierarchy,” she said.