CERN May Have Evidence of a Quasiparticle We’ve Been Hunting For Decades


Meet the elusive odderon.

The Large Hadron Collider (LHC) is the particle accelerator that just keeps on giving, and recent experiments at the site suggest we’ve got the first evidence for a mysterious subatomic quasiparticle that, until now, was only a hypothesis.

Quasiparticles aren’t technically particles, but they act like them in some respects, and the newly recorded reactions point to a particular quasiparticle called the odderon.

It already has a name because physicists have been on its theoretical trail for the past 40 years.

Now, they still haven’t seen the elusive odderon itself, but researchers have now observed certain effects that hint the quasiparticle really is there.

That would in turn give us new information to feed into the Standard Model of particle physics, the guidebook that all the building blocks of physical matter are thought to follow.

“This doesn’t break the Standard Model, but there are very opaque regions of the Standard Model, and this work shines a light on one of those opaque regions,” says one of the team, particle physicist Timothy Raben from the University of Kansas.

“These ideas date back to the 70s, but even at that time it quickly became evident we weren’t close technologically to being able to see the odderon, so while there are several decades of predictions, the odderon has not been seen.”

The reactions studied in this case involve quarks, or electrically charged subatomic particles, and gluons, which act as exchange particles between quarks and enable them to stick together to form protons and neutrons.

In proton collisions where the protons remain intact, up until now scientists have only seen this happen when an even number of gluons are exchanged between different protons. The new research notes, for the first time, these reactions happening with an odd number of gluons.

And it’s the way the protons deviate rather than break that’s important for this particular area of investigation. It was this phenomena that first led to the idea of a quasiparticle called an odderon, to explain away collisions where protons survived.

“The odderon is one of the possible ways by which protons can interact without breaking, whose manifestations have never been observed .. this could be the first evidence of that,” Simone Giani, spokesperson at the TOTEM experiment of which this is a part, told Ryan F. Mandelbaum at Gizmodo.

It’s a pretty complex idea to wrap your head around, so the researchers have used a vehicle metaphor to explain what’s going on.

“The protons interact like two big semi-trucks that are transporting cars, the kind you see on the highway,” explains Raben.

“If those trucks crashed together, after the crash you’d still have the trucks, but the cars would now be outside, no longer aboard the trucks – and also new cars are produced. Energy is transformed into matter.”

“Until now, most models were thinking there was a pair of gluons – always an even number… We found measurements that are incompatible with this traditional model of assuming an even number of gluons.”

What all of that theoretical physics and subatomic analysis means is that we may have seen evidence of the odderon at work – with the odderon being the total contribution produced from the exchange of an odd number of gluons.

The experiments involved a team of over 100 physicists, colliding billions of proton pairs together every second in the LHC. At its peak, data was being collected at 13 teraelectronvolts (TeV), a new record.

By comparing these high energy tests with results gleaned from other tests run on less powerful hardware, the researchers could reach a new level of accuracy in their proton collision measurements, and that may have revealed the odderon.

Ultimately this kind of super-high energy experiment can feed into all kinds of areas of research, including medicine, water purification, and cosmic ray measuring.

We’re still waiting for confirmation that this legendary quasiparticle has in fact been found – or at least that its effects have – and the papers are currently submitted to be published in peer reviewed journals.

But it’s definitely a super-exciting time for physicists.

“We expect big results in the coming months or years,” says one of the researchers, Christophe Royon from the University of Kansas.

The research is currently undergoing peer review, but you can read the studies on the ArXiv.org and CERN pre-print servers.

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The Real Science of the God Particle in Netflix’s ‘The Cloverfield Paradox’


Even if you’re not a particle physics buff, you may have noticed that the plot of Netflix’s surprise Superbowl Sunday release, The Cloverfield Paradox, relies heavily on a huge physics discovery that was in the news a few years ago: the Higgs Boson particle.

The Cloverfield Paradox

Also known as the “God particle” — which happened to be the working title of the new J.J. Abrams film — the Higgs Boson was first observed directly by scientists in 2012.

Gratuitous spoilers for The Cloverfield Paradox ahead.

In the midst of an energy crisis in the year 2028, scientists are struggling to use a massive space-based particle accelerator to help efficiently produce energy. When they finally get it to accelerate particles, they suddenly find themselves on the opposite side of the sun from the Earth. Chaos ensues: Worms explode out of a guy. Someone’s arm rematerializes on the other side of the ship with a mind of its own. Standard body horror nonsense.

Long story short, we’re led to believe that this botched experiment is what brought monsters to Earth in the first Cloverfield film — which, given the crazy science that goes on at the European Organization for Nuclear Research (CERN), is not totally absurd.

Cloverfield Paradox Monster
In ‘The Cloverfield Paradox,’ we’re led to believe that a particle accelerator experiment gone wrong in 2028 messed up the multiverse and caused a monster attack in 2008.

Any good science fiction story has some basis in reality, and it’s clear that The Cloverfield Paradox drew heavily on conspiracy theories that sprung up around CERN and its efforts to find direct evidence of the Higgs-Boson particle using a 27-kilometer circumference accelerator, the Large Hadron Collider.

 The particle’s discovery was a big deal because it was the only one out of 17 particles predicted by the Standard Model of particle physics that had never been observed. The Higgs Boson is partly responsible for the forces between objects, giving them mass.

But it wasn’t the particle itself that conspiracy theorists and skeptics worried about. It’s the way physicists had to observe it.

Doing so involved building the LHC, an extraordinarily large real-life physics experiment that housed two side-by-side high-energy particle beams traveling in opposite directions at close to the speed of light. The hope was that accelerated protons or lead ions in the beam would collide, throwing off a bunch of extremely rare, short-lived particles, one of which might be the Higgs Boson. In 2012, scientists finally observed it, calling it the “God particle” because “Goddamn particle” — as in “so Goddamn hard to find” — was considered too rude to print.

Critics and skeptics argued that colliding particles at close to the speed of light increased the potential to accidentally create micro black holes and possibly even larger black holes, leading to wild speculation like that in Cloverfield Paradox.

cloverfield paradox
Ah yes, the elusive Hands Bosarm particle.

This has never happened in real life, of course, and there’s also strong evidence that it couldn’t happen. Check out this excerpt from an interaction between astrophysicist Neil deGrasse Tyson and science skeptic Anthony Liversidge that Gizmodo reported on in 2011:

NDT: To catch everybody up on this, there’s a concern that if you make a pocket of energy that high, it might create a black hole that would then consume the Earth. So I don’t know what papers your fellow read, but there’s a simple calculation you can do. Earth is actually bombarded by high energy particles that we call cosmic rays, from the depths of space moving at a fraction of the speed of light, energies that far exceed those in the particle accelerator. So it seems to me that if making a pocket of high energy would put Earth at risk of black holes, then we and every other physical object in the universe would have become a black hole eons ago because these cosmic rays are scattered across the universe are hitting every object that’s out there. Whatever your friend’s concerns are were unfounded.

Liversidge may be on the fringe with his argument, but he isn’t alone. As Inverse previously reported, Vanderbilt University physicist Tom Weiler, Ph.D., has hypothesized that a particle created alongside the Higgs Boson, called the Higgs singlet, could travel through time through an as-yet-undiscovered fifth dimension. If Weiler’s hypothesis is correct, then it seems possible that interdimensional travel, as depicted in Cloverfield Paradox, could be possible, though his model really only accounts for the Higgs singlet particle’s ability to time travel.

'The Cloverfield Paradox' is forever the most important Cloverfield.
In ‘The Cloverfield Paradox,’ a particle accelerator plays a central role.

The reason the Cloverfield Paradox scientists were trying to fire up a particle accelerator in space is just as speculative. While particle accelerators take a massive amount of energy to accelerate their beams to near light speed, some physicists argue that under certain conditions, a particle accelerator could actually produce energy. Using superconductors, they argued, it would be possible for a particle accelerator to actually produce plutonium that could be used in nuclear reactors. So in a sense, the science of the movie is kind of based on maybe possibly real science.

That being said, this space horror film takes extreme liberties, even where it’s based on real science. Even on the extreme off-chance that any of the hypotheses outlined in this article turned out to be true, the tiny potential side effects of particle accelerators are nothing like what we see in The Cloverfield Paradox.

The Hunt For Elusive Single-Pole Magnets Just Became More Challenging


A search through a mountain of data from the Large Hadron Collider for particles called magnetic monopoles has once again come up empty handed.

That doesn’t yet completely rule out the possibility of these hypothetical objects. But it does tell us that if they exist, they might be extraordinarily massive particles that are beyond our ability to create.

 

Magnetic monopoles are often explained as being a particle that represents a single pole of a magnet – something nobody has ever seen so far.

If you slice a magnet in half, you still get an object with a north pole and a south pole. No matter how tiny you make the thing, you won’t get an isolated pole.

Not that this stops physicists from looking: the story of the magnetic monopole dates back to the equations of the theoretical physicist James Clerk Maxwell.

He mathematically showed that we could swap electric for magnetic fields and not see any real difference – in other words, the two were symmetrical.

That only works for their fields, though. Electrical currents have charges, which are points that exist in a vector, meaning the current flows in a direction.

If we have magnetic fields that are symmetrical with electric fields, why not magnetic points that also flow along a vector? Finding one would tell us a lot about their electrical twin as well.

So the search was on for magnetic points that were the equivalent of a charge – the magnetic monopole.

Not everybody is convinced they exist. Last year, physicists argued that the symmetry between electricity and magnetism is broken at a deep, fundamental level. Still, for many optimists, the search continues.

“A lot of people think they should exist,” says particle physicist James Pinfold from the University of Alberta in Edmonton, Canada.

He and his team have just trawled through a pile of data from the Monopole and Exotics Detector at the LHC (MoEDAL). And they came up with nothing.

Their research was published recently on the pre-print website arXiv.org, which means we need to be cautious in not reading too deeply until it gets published in a peer-reviewed journal.

But the fact they had six times the information as previous efforts involving MoEDAL, and also took into consideration monopoles with a different kind of spin to previous analyses, shows how much ground has been covered.

In some ways this is a good thing – the research further narrows down where the monopole might be hiding. Crashing protons together at ridiculous speeds is just one way we might be able to make magnetic monopoles.

Another team of physicists from Imperial College London took a slightly different approach to searching for the elusive particles, publishing their results in the journal Physical Review Letters last December.

Part of the problem as they saw it was if monopoles were being produced inside particle colliders, there was every chance they’d be strongly stuck together.

What was needed was another way to narrow down the kinds of properties they might have, and then compare those with MoEDAL’s results.

To do this they considered how magnetic monopoles might appear inside intense, hot magnetic fields, just like those surrounding a type of neutron star called a magnetar.

If their mass was small enough, their magnetic charge would affect the star’s magnetic field.

Of course, even the strength of the monopole’s charge is hypothetical at the moment, but based on a few reasonable assumptions they calculated we could expect the particle’s mass to be more than about the third of that of a proton.

That’s not exactly tiny. And if the actual charge is heavier than the smallest one imaginable, that mass goes up.

Either way we look at it, physicists are needing to consider two possibilities; either the magnetic monopole is a myth, and the fractured symmetry between electricity and magnetism is a fundamental part of nature; or this thing is big.

It’s possible we just might need bigger colliders. It’s also possible magnetic monopoles are so heavy, only something as monumental as a Big Bang could produce them, leaving us to hunt for relics.

Only one thing is for certain – the hunt continues

The Large Hadron Collider Just Detected a New Particle That’s Heavier Than a Proton


The Large Hadron Collider has once again done what it does best – smash bits of matter together and find new particles in the carnage.

This time physicists have come across a real charmer. It’s four times heavier than a proton and could help challenge some ideas about how this kind of matter sticks together.

 We’ve seen a lot of interesting new particles from CERN’s Large Hadron Collider “beauty” (LHCb) collaboration, which is a little sister to the ATLAS and CMS experiments that brought us the famous Higgs boson a few years back.

The experiments run in CERN’s colliders all involve accelerating matter and then bringing it to a quick stop. The resulting burst of energy results in a shower of particles with different properties, most of which we’re pretty familiar with.

Running these experiments over and over again and doing the maths on the sizes and behaviours of the particles as they form and interact with one another can occasionally provide something different.

We can now officially add a new kind of baryon to the zoo of particles, one that was already predicted to exist but never before seen.

The two baryons you’re no doubt most familiar with are the ones that make up an atom’s nucleus, called protons and neutrons.

Baryons are effectively triplets of smaller particles called quarks, which are elementary particles meaning they aren’t made up of anything smaller themselves.

 Quarks come in a variety of flavours, oddly called up, down, top, bottom, charm, and strange. It’s combinations of these that give us different bosons. Current models predict there are a bunch of ways quarks can make baryons, with some more common than others.

Protons consist of two ups and a down quark, while neutrons are two downs and an up. These quarks stick together under what’s called the strong nuclear force, which is caused by the swapping of particles called gluons. Never let it be said that physicists lack a sense of humour.

This new baryon – made when two charm quarks and a single up bound together – was given the less whimsical name Xi cc++, so they can’t all be winners.

Quarks have different masses, and charm is a beefy one. That makes this baryon a touch on the heavy side, which is good news for particle physicists.

“Finding a doubly heavy-quark baryon is of great interest as it will provide a unique tool to further probe quantum chromodynamics, the theory that describes the strong interaction, one of the four fundamental forces,” said Giovanni Passaleva, the spokesperson for the LHCb collaboration.

Seeing how this particle keeps itself together compared to the predictions made by current models will help give the going theories a good shake.

 Being made of two heavy quarks should give Xi cc++ a slightly different structure to protons and neutrons.

“In contrast to other baryons, in which the three quarks perform an elaborate dance around each other, a doubly heavy baryon is expected to act like a planetary system, where the two heavy quarks play the role of heavy stars orbiting one around the other, with the lighter quark orbiting around this binary system,” says former collaboration spokesperson Guy Wilkinson.

If you’re wondering where this baryon has been hiding all this time, like many particles it doesn’t hang around very long. It wasn’t seen directly, but was recognised by the particles it broke into.

The LHCb experiment is a champion at spotting these kinds of decay products, as well as making heavy quarks.

The discovery has a high statistical significance at 7 sigma. Physicists break out the champagne at 5 sigma, so we can be pretty confident Xi cc++ was produced.

If you’re playing Standard Model bingo, that’s one more to cross off your list.

Tetraquark Evidence Mounts with Help from the Large Hadron Collider


IN BRIEF

Physicists working with the Large Hadron Collider have found an entire set of particles with four heavy quarks, further confirming the existence of tetraquarks. The four structures do not follow the characteristics of particles dictated by pre-existing laws of physics.

“IT’S THE FIRST TIME WE’VE SEEN THIS”

While technically protons have tons of quarks (and anti-quarks), three of those quarks, known as valence quarks, make up the positive charge of a proton. Hence, the three-quark label.

Throughout the history of physics, we have been familiar with two and three-quark particles. This made the recent discovery of four-quark particles called tetraquarks, and five-quark particles or pentaquarks, a slow uphill battle as it is met with severe skepticism. In 2003, the Belle experiment in Japan first observed particles in a four-quark state but lacked sufficient evidence to definitively prove it. Belle, Fermilab, and other research facilities since have announced similar observations, but none have been able to provide irrefutable proof of their existence.

Tetraquark in comparison with ordinary matter. Credit: Nature
In 2014, the Large Hadron Collider finally confirmed tetraquarks, and now has identified four more of these particles—a discovery that stands as solid evidence that would permanently cement their existence. “It was a long road to get here,” says University of Iowa physicist Kai Yi of the Collider Detector at Fermilab (CDF) and Columbia-MIT-Fermilab (CMF) experiments.

The exotic particles are named based on their respective masses in mega-electronvolts: X(4140), X(4274), X(4500) and X(4700). They are each composed entirely of heavy quarks: two charm quarks and two strange quarks arranged in a unique way, each with a different internal structure by mass and quantum numbers. “The quarks inside these particles behave like electrons inside atoms,” says Syracuse University physics professor Tomasz Skwarnicki says. “They can be ‘excited’ and jump into higher energy orbitals. The energy configuration of the quarks gives each particle its unique mass and identity.”

 “What we have discovered is a unique system,” Skwarnicki continues. “We have four exotic particles of the same type; it’s the first time we have seen this and this discovery is already helping us distinguish between the theoretical models.”

ARE THEY EVEN PARTICLES?

Our current laws of physics cannot explain this groundbreaking discovery. “We looked at every known particle and process to make sure these four structures couldn’t be explained by any pre-existing physics. It was like baking a six-dimensional cake with 98 ingredients and no recipe—just a picture of a cake,” Syracuse University researcher Thomas Britton says.

The researchers are now working on models that would help make sense of these new particles, which may not even be particles, as they do not behave in accordance with our standard models of particles. “The molecular explanation does not fit with the data,” Skwarnicki adds. “But I personally would not conclude that these are definitely tightly bound states of four quarks. It could be possible that these are not even particles. The result could show the complex interplays of known particle pairs flippantly changing their identities.”

The bizarre particles (or whatever else they may eventually turn out to be) are possibly heralding a new era of expansion for quantum physics, thanks to the Large Hadron Collider. “The huge amount of data generated by the LHC is enabling a resurgence in searches for exotic particles and rare physical phenomena,” Britton says. “There’s so many possible things for us to find and I’m happy to be a part of it.”

Ancient particle accelerator discovered on Mars.


New images of the surface of Mars taken by NASA’s Mars Reconnaissance Orbiter probe have revealed the presence of the largest particle accelerator.

The search for water, or even signs of life, on the planet Mars has been ongoing for some time. But with today’s announcement by CERN and NASA scientists, the exploration of the red planet has revealed a major new discovery. New images of the surface of Mars taken by NASA’s Mars Reconnaissance Orbiter probe, analysed by an interdisciplinary team of experts from the fields of geology, archaeology and particle physics, have revealed the presence of the largest particle accelerator ever built. The team has shown that Olympus Mons, previously thought to be the largest volcanic formation in the solar system, is in fact the remains of an ancient particle accelerator thought to have operated several million years ago.

A landslide stretching over several kilometres spotted by the probe’s high-resolution camera, sparked the scientists’ attention. This apparently recent event revealed a number of structures, which intrigued the scientists, as their shapes clearly resembled those of superconducting accelerating cavities such as those used in the Large Hadron Collider (LHC). With a circumference of almost 2000 kilometres, this particle accelerator would have been around 75 times bigger than the LHC, and millions of times more powerful. However, it is not yet known which type of particles might have been accelerated in such a machine.

Ancient Egyptian hieroglyphs, the meaning of which was previously a mystery, seem to corroborate these observations, leading scientists to believe that the pyramids might have served as giant antennae 

This major discovery could also help to explain the Egyptian pyramids, one of archaeology’s oldest mysteries. Heavily eroded structures resembling pyramids also appear on the images in the immediate vicinity of Olympus Mons. In addition, ancient Egyptian hieroglyphs, the meaning of which was previously a mystery, seem to corroborate these observations, leading scientists to believe that the pyramids might have served as giant antennae. The pyramids on Earth might therefore have allowed the accelerator to be controlled remotely. “The accelerator control room was probably under the pyramids,” said Friedrich Spader, CERN’s Head of Technical Design.

This particle accelerator – a veritable “stargate” – is thought to have served as a portal into the solar system for a highly technologically advanced civilisation with the aim of colonisation. “The papyrus that was recently deciphered indicates that the powerful magnetic field and the movement of the particles in the accelerator were such that they would create a portal through spacetime,” said Fadela Emmerich, the leader of the team of scientists. “It’s a phenomenon that is completely new to CERN and we can’t wait to study it!” Such a technology could revolutionise space travel and open the way for intergalactic exploration.

Olympus Mons was until now considered to be the biggest volcano in the solar system, with its most recent lava flows estimated to be about 2 million years old. Scientists believe that this dating is quite accurate, on the basis of the latest measurements carried out by NASA’s Mars Odyssey probe. “This would mean that the particle accelerator was last used around 2 million years ago,” suggested Eilert O’Neil, the geologist who led this aspect of the research.

The powerful synchrotron radiation emitted by the particle accelerator generated an intense heat, which explains the volcanic structure and the presence of lava flows. “We have also suspected for a long time that a large quantity of water must have existed on the surface of Mars. We can only assume that this water was used at the time to cool the machines,” revealed Friedrich Spader.

“We’re probably talking about forgotten technologies and a highly advanced ancient civilisation,” said Eilert O’Neil. “Maybe even our own distant ancestors.”

Source:http://home.cern/

What No New Particles Means for Physics


Physicists are confronting their “nightmare scenario.” What does the absence of new particles suggest about how nature works?

[No Caption]
Physicists at the Large Hadron Collider (LHC) in Europe have explored the properties of nature at higher energies than ever before, and they have found something profound: nothing new.

It’s perhaps the one thing that no one predicted 30 years ago when the project was first conceived.

The infamous “diphoton bump” that arose in data plots in December has disappeared, indicating that it was a fleeting statistical fluctuation rather than a revolutionary new fundamental particle. And in fact, the machine’s collisions have so far conjured up no particles at all beyond those catalogued in the long-reigning but incomplete “Standard Model” of particle physics. In the collision debris, physicists have found no particles that could comprise dark matter, no siblings or cousins of the Higgs boson, no sign of extra dimensions, no leptoquarks — and above all, none of the desperately sought supersymmetry particles that would round out equations and satisfy “naturalness,” a deep principle about how the laws of nature ought to work.

“It’s striking that we’ve thought about these things for 30 years and we have not made one correct prediction that they have seen,” said Nima Arkani-Hamed, a professor of physics at the Institute for Advanced Study in Princeton, N.J.

The news has emerged at the International Conference on High Energy Physics in Chicago over the past few days in presentations by the ATLAS and CMS experiments, whose cathedral-like detectors sit at 6 and 12 o’clock on the LHC’s 17-mile ring. Both teams, each with over 3,000 members, have been working feverishly for the past three months analyzing a glut of data from a machine that is finally running at full throttle after being upgraded to nearly double its previous operating energy. It now collides protons with 13 trillion electron volts (TeV) of energy — more than 13,000 times the protons’ individual masses — providing enough raw material to beget gargantuan elementary particles, should any exist.

 

So far, none have materialized. Especially heartbreaking for many is the loss of the diphoton bump, an excess of pairs of photons that cropped up in last year’s teaser batch of 13-TeV data, and whose origin has been the speculation of some 500 papers by theorists. Rumors about the bump’s disappearance in this year’s data began leaking in June, triggering a community-wide “diphoton hangover.”

“It would have single-handedly pointed to a very exciting future for particle experiments,” said Raman Sundrum, a theoretical physicist at the University of Maryland. “Its absence puts us back to where we were.”

The lack of new physics deepens a crisis that started in 2012 during the LHC’s first run, when it became clear that its 8-TeV collisions would not generate any new physics beyond the Standard Model. (The Higgs boson, discovered that year, was the Standard Model’s final puzzle piece, rather than an extension of it.) A white-knight particle could still show up later this year or next year, or, as statistics accrue over a longer time scale, subtle surprises in the behavior of the known particles could indirectly hint at new physics. But theorists are increasingly bracing themselves for their “nightmare scenario,” in which the LHC offers no path at all toward a more complete theory of nature.

Some theorists argue that the time has already come for the whole field to start reckoning with the message of the null results. The absence of new particles almost certainly means that the laws of physics are not natural in the way physicists long assumed they are. “Naturalness is so well-motivated,” Sundrum said, “that its actual absence is a major discovery.”

Missing Pieces

The main reason physicists felt sure that the Standard Model could not be the whole story is that its linchpin, the Higgs boson, has a highly unnatural-seeming mass. In the equations of the Standard Model, the Higgs is coupled to many other particles. This coupling endows those particles with mass, allowing them in turn to drive the value of the Higgs mass to and fro, like competitors in a tug-of-war. Some of the competitors are extremely strong — hypothetical particles associated with gravity might contribute (or deduct) as much as 10 million billion TeV to the Higgs mass — yet somehow its mass ends up as 0.125 TeV, as if the competitors in the tug-of-war finish in a near-perfect tie. This seems absurd — unless there is some reasonable explanation for why the competing teams are so evenly matched.

 

Maria Spiropulu of the California Institute of Technology, pictured in the LHC’s CMS control room, brushed aside talk of a nightmare scenario, saying, “Experimentalists have no religion.”

Supersymmetry, as theorists realized in the early 1980s, does the trick. It says that for every “fermion” that exists in nature — a particle of matter, such as an electron or quark, that adds to the Higgs mass — there is a supersymmetric “boson,” or force-carrying particle, that subtracts from the Higgs mass. This way, every participant in the tug-of-war game has a rival of equal strength, and the Higgs is naturally stabilized. Theorists devised alternative proposals for how naturalness might be achieved, but supersymmetry had additional arguments in its favor: It caused the strengths of the three quantum forces to exactly converge at high energies, suggesting they were unified at the beginning of the universe. And it supplied an inert, stable particle of just the right mass to be dark matter.

“We had figured it all out,” said Maria Spiropulu, a particle physicist at the California Institute of Technology and a member of CMS. “If you ask people of my generation, we were almost taught that supersymmetry is there even if we haven’t discovered it. We believed it.”

Hence the surprise when the supersymmetric partners of the known particlesdidn’t show up — first at the Large Electron-Positron Collider in the 1990s, then at the Tevatron in the 1990s and early 2000s, and now at the LHC. As the colliders have searched ever-higher energies, the gap has widened between the known particles and their hypothetical superpartners, which must be much heavier in order to have avoided detection. Ultimately, supersymmetry becomes so “broken” that the effects of the particles and their superpartners on the Higgs mass no longer cancel out, and supersymmetry fails as a solution to the naturalness problem. Some experts argue that we’ve passed that point already. Others, allowing for more freedom in how certain factors are arranged, say it is happening right now, with ATLAS and CMS excluding the stop quark — the hypothetical superpartner of the 0.173-TeV top quark — up to a mass of 1 TeV. That’s already a nearly sixfold imbalance between the top and the stop in the Higgs tug-of-war. Even if a stop heavier than 1 TeV exists, it would be pulling too hard on the Higgs to solve the problem it was invented to address.

 

“I think 1 TeV is a psychological limit,” said Albert de Roeck, a senior research scientist at CERN, the laboratory that houses the LHC, and a professor at the University of Antwerp in Belgium.

Some will say that enough is enough, but for others there are still loopholes to cling to. Among the myriad supersymmetric extensions of the Standard Model, there are more complicated versions in which stop quarks heavier than 1 TeV conspire with additional supersymmetric particles to counterbalance the top quark, tuning the Higgs mass. The theory has so many variants, or individual “models,” that killing it outright is almost impossible. Joe Incandela, a physicist at the University of California, Santa Barbara, who announced the discovery of the Higgs boson on behalf of the CMS collaboration in 2012, and who now leads one of the stop-quark searches, said, “If you see something, you can make a model-independent statement that you see something. Seeing nothing is a little more complicated.”

Particles can hide in nooks and crannies. If, for example, the stop quark and the lightest neutralino (supersymmetry’s candidate for dark matter) happen to have nearly the same mass, they might have stayed hidden so far. The reason for this is that, when a stop quark is created in a collision and decays, producing a neutralino, very little energy will be freed up to take the form of motion. “When the stop decays, there’s a dark-matter particle just kind of sitting there,” explainedKyle Cranmer of New York University, a member of ATLAS. “You don’t see it. So in those regions it’s very difficult to look for.” In that case, a stop quark with a mass as low as 0.6 TeV could still be hiding in the data.

Experimentalists will strive to close these loopholes in the coming years, or to dig out the hidden particles. Meanwhile, theorists who are ready to move on face the fact that they have no signposts from nature about which way to go. “It’s a very muddled and uncertain situation,” Arkani-Hamed said.

New Hope

Many particle theorists now acknowledge a long-looming possibility: that the mass of the Higgs boson is simply unnatural — its small value resulting from an accidental, fine-tuned cancellation in a cosmic game of tug-of-war — and that we observe such a peculiar property because our lives depend on it. In this scenario, there are many, many universes, each shaped by different chance combinations of effects. Out of all these universes, only the ones with accidentally lightweight Higgs bosons will allow atoms to form and thus give rise to living beings. But this “anthropic” argument is widely disliked for being seemingly untestable.

 

Nima Arkani‐Hamed discussing theoretical physics with a colleague at the Institute for Advanced Study in Princeton, N.J.

In the past two years, some theoretical physicists have started to devise totally new natural explanations for the Higgs mass that avoid the fatalism of anthropic reasoning and do not rely on new particles showing up at the LHC. Last week at CERN, while their experimental colleagues elsewhere in the building busily crunched data in search of such particles, theorists held a workshop to discuss nascent ideas such as the relaxion hypothesis — which supposes that the Higgs mass, rather than being shaped by symmetry, was sculpted dynamically by the birth of the cosmos — and possible ways to test these ideas. Nathaniel Craig of the University of California, Santa Barbara, who works on an idea called “neutral naturalness,” said in a phone call from the CERN workshop, “Now that everyone is past their diphoton hangover, we’re going back to these questions that are really aimed at coping with the lack of apparent new physics at the LHC.”

Arkani-Hamed, who, along with several colleagues, recently proposed another new approach called “Nnaturalness,” said, “There are many theorists, myself included, who feel that we’re in a totally unique time, where the questions on the table are the really huge, structural ones, not the details of the next particle. We’re very lucky to get to live in a period like this — even if there may not be major, verified progress in our lifetimes.”

As theorists return to their blackboards, the 6,000 experimentalists with CMS and ATLAS are reveling in their exploration of a previously uncharted realm. “Nightmare, what does it mean?” said Spiropulu, referring to theorists’ angst about the nightmare scenario. “We are exploring nature. Maybe we don’t have time to think about nightmares like that, because we are being flooded in data and we are extremely excited.”

There’s still hope that new physics will show up. But discovering nothing, in Spiropulu’s view, is a discovery all the same — especially when it heralds the death of cherished ideas. “Experimentalists have no religion,” she said.

Some theorists agree. Talk of disappointment is “crazy talk,” Arkani-Hamed said. “It’s actually nature! We’re learning the answer! These 6,000 people are busting their butts and you’re pouting like a little kid because you didn’t get the lollipop you wanted?”

Hope for a New Particle Fizzles at the LHC


A curious signal of a potentially revolutionary new particle detected last year turned out to be a fluke.

A portion of the ATLAS detector, one of the two massive experiments at the Large Hadron Collider that reported—and have now refuted—what could have been a revolutionary new subatomic particle. 

For months, the world of physics has been abuzz with rumors about a potential new subatomic particle that could revolutionize our entire view of physics. But new results presented today by physicists from the Large Hadron Collider (LHC) today have, for now, quashed the revolution.

The first hints of a new particle appeared in December 2015, when two independent experiments at the LHC, ATLAS and CMS, each announced the same tantalizing quirk in their data. Both experiments smash together protons at nearly the speed of light, searching for new fundamental particles produced by the enormously energetic collisions. When they ramped up to their highest energies yet, the two experiments detected a mysterious signal: more pairs of photons with a combined energy of 750 giga-electron volts (GeV) than expected.

This “diphoton bump” was not a prediction of the Standard Model of physics—a rigorously tested and profoundly successful theory forged in the 1970s that incorporates all known fundamental particles and forces. Despite its success, however, the Standard Model does not explain what lies at the hearts of black holes, the nature of dark matter and dark energy, the quantum behavior of gravity, and other deep mysteries of the universe. With their shared diphoton bumps, ATLAS and CMS appeared on the verge of peering into physics beyond the Standard Model’s musty confines. Within weeks, the little bump had inspired hundreds of speculative papers by theorists. “At the LHC, physicists are looking very intensively for new particles and new laws of physics so it’s easy to get excited about something that seems very convincing,” says Michael Peskin, a theoretical physicist at Stanford’s SLAC National Accelerator Laboratory.

Whatever produced the diminutive diphoton bump didn’t neatly fit into any theory. Many scientists suggested that the bump was produced by a heavier cousin of the Higgs boson, another particle that similarly showed up as an eyebrow-raising blip in the data about four years ago. Others suggested that it could be a kind of dark matter particle, or even the vaunted graviton, the predicted carrier particle for gravity itself.

But as scientists at the LHC started collecting more data this year, the 750 GeV diphoton bump started disappearing. Now, after analyzing nearly five times the amount of data that they had last year, ATLAS and CMS physicists have watched the bump diminish to statistical insignificance. Presenting at the International Conference on High Energy Physics in Chicago, particle physicist and ATLAS spokesperson Dave Charlton said that when looking at all the data, the 750GeV signal now only has a significance of 2 sigma, which is much less than the 5 sigma (or 1 in 3.5 million chance) that is needed to confirm a new discovery in physics. Simply put, the diphoton bump was a false alarm. “It is a bit surprising that we saw the fluctuation on both instruments but it was just that—a fluctuation or statistical fluke,” said Charlton.

Seeing anomalies in the data is not uncommon at the LHC. The collider crashes so many protons together and churns out so much raw data that occasionally finding extra pairs of photons in the wreckage was bound to happen. “If you conduct many, many searches you come across these kinds of coincidences,” says Guy Wilkinson, a member of the LHCb collaboration.

Although the diphoton bump has now evaporated under closer scrutiny, researchers remain optimistic that the LHC will still lead them to new physics beyond the Standard Model. The multibillion-dollar project has years of operations left during which it will produce far more data for physicists to parse for elusive new particles. “We would have been very lucky if we found something, some new phenomenon or some new state of matter at this early stage,” says CMS physicist Tiziano Camporesi. “But we have to be patient.”

 

The LHC is now colliding lead ions at record-breaking energy levels


After shutting down for two years to make substantial upgrades, the Large Hadron Collider (LHC) resumed operations earlier in 2015, and is now embarking on a new phase – colliding lead ions at an energy level twice that of any previous collider experiment.

Starting this month, scientists at the world’s largest particle accelerator are running a trial with positively charged lead ions, which are lead atoms stripped of their electrons. Colliding these lead ions allows scientists at the European Organisation for Nuclear Research (CERN) in Switzerland to study a state of matter that existed shortly after the Big Bang, reaching a temperature of several trillion degrees.

“It is a tradition to collide ions over one month every year as part of our diverse research program at the LHC,” said CERN chief Rolf Heuer. “This year however is special, as we reach a new energy and will explore matter at an even earlier stage of our Universe.”

To study the state of matter directly after the Big Bang, you need to recreate a moment in time that was almost infinitesimally brief. The state of matter that’s being quasi-simulated by CERN only existed in our Universe for a few millionths of a second, at a time when extremely hot and dense matter existed in a kind ofprimordial soup made up of particles called quarks and gluons.

By increasing the energy of the collisions in the new lead ion experiments – which is now possible thanks to the two years of work carried out on the LHC – scientists will increase the volume and temperature of quark and gluon plasma, enabling a more detailed and precise study of how matter existed in the fleeting conditions immediately after the Big Bang.

“There are many very dense and very hot questions to be addressed with the ion run for which our experiment was specifically designed and further improved during the shutdown,” said one of the team, Paolo Giubellino. “The whole collaboration is enthusiastically preparing for a new journey of discovery.”

In an opinion piece about the experiment, John Jowett, who runs CERN’s heavy-ion program, said we should celebrate the breaking of a “new symbolic energy barrier”, explaining that it might be a while before the next such frontier could be passed.

“[T]he concentration of so much energy into the tiny nuclear volume is enough to establish truly colossal densities and temperatures about a quarter of a million times those at the core of the sun,” he wrote. “Heavy-ion collisions recreate the quark-gluon plasma, the extreme state of matter that is believed to have filled the Universe when it was only microseconds old… From the perspective of the early 1950s, the energies attained by the [LHC] would have seemed like science-fiction.”

LHC creates liquid from Big Bang


Wow, this is amazing, maybe we will be closer from understanding the universe than ever.

Scientists using the Large Hadron Collider (LHC) have produced tiny droplets of a state of matter thought to have existed right at the birth of the universe.

An international team at the Large Hadron Collider (LHC) have produced quark-gluon plasma — a state of matter thought to have existed right at the birth of the universe — with fewer particles than previously thought possible. The results were published in the journal APS Physics on June 29, 2015.

The Large Hadron Collider is the world’s largest and most powerful particle accelerator. The LHC, located in a tunnel between Lake Geneva and the Jura mountain range on the Franco-Swiss border, is the largest machine in the world. The supercollider was restarted this spring (April 2015) following two years of intense maintenance and upgrade. Take a virtual tour of the LHC here.

The new material was discovered by colliding protons with lead nuclei at high energy inside the supercollider’s Compact Muon Solenoid detector. Physicists have dubbed the resulting plasma the “littlest liquid.”

So, the Big bang was not solid, but liquid??? Did i get ir right, this is a very interesting stuff.


Quan Wang is a University of Kansas researcher working with the team at CERN, the European Organization for Nuclear Research. Wang described quark-gluon plasma as a very hot and dense state of matter of unbound quarks and gluons — that is, not contained within individual nucleons. He said:

It’s believed to correspond to the state of the universe shortly after the Big Bang.

While high-energy particle physics often focuses on detection of subatomic particles, such as the recently discovered Higgs Boson, the new quark-gluon-plasma research instead examines behavior of a volume of such particles.

Wang said such experiments might help scientists to better understand cosmic conditions in the instant following the Big Bang.

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