From AAAS: “Five things scientists could learn with their new, improved particle accelerator”

AAAS

15 February
Emily Conover

CMS

The Large Hadron Collider (LHC) is back, and it’s better than ever.

LHC

The particle accelerator, located at CERN, the European particle physics lab near Geneva, Switzerland, shut down in February 2013, and since then scientists have been upgrading and repairing it and its particle detectors. The LHC will be back up to full speed this May. Yesterday, scientists discussed the new prospects for the LHC at the annual meeting of AAAS (which publishes Science).

The LHC is the world’s most powerful particle accelerator. Protons blast along its 17-mile (27-kilometer) ring at nearly light speed, colliding at the sites of several particle detectors, which sift through the resulting particle debris. In 2012, LHC’s ATLAS and CMS experiments discovered the Higgs boson with data from the LHC’s first run, thereby explaining how particles get mass.

ATLAS

CMS

The revamped LHC will run at a 60% higher energy, with more sensitive detectors, and a higher collision rate. What might we find with the new-and-improved machine? Here are five questions scientists hope to answer:

1. Does the Higgs boson hold any surprises?

Now that we’ve found the Higgs boson, there’s still a lot we can learn from it. Thanks to the LHC’s energy boost, it will produce Higgs bosons at a rate five times higher, and scientists will be using the resulting abundance of Higgs to understand the particle in detail. How does it decay? Does it match the theoretical predictions? Anything out of the ordinary would be a boon to physicists, who are looking for evidence of new phenomena that can explain some of the unsolved mysteries of physics.

2. What is “dark matter”?

Only 15% of the matter in the universe is the kind we are familiar with. The rest is dark matter, which is invisible to us except for subtle hints, like its gravitational effects on the cosmos. Physicists are clamoring to know what it is. One likely dark matter culprit is a WIMP, or weakly interacting massive particle, which could show up in the LHC. Dark matter’s fingerprints could even be found on the Higgs boson, which may sometimes decay to dark matter. You can bet that scientists will be sifting through their data for any trace.

3. Will we ever find supersymmetry?

Supersymmetry, or SUSY, is a hugely popular theory of particle physics that would solve many unanswered questions about physics, including why the mass of the Higgs boson is lighter than naively expected—if only it were true. This theory proposes a slew of exotic elementary particles that are heavier twins of known ones, but with different spin—a type of intrinsic rotational momentum. Higher energies at the new LHC could boost the production of hypothetical supersymmetric particles called gluinos by a factor of 60, increasing the odds of finding it.

Standard Model of Supersymmetric particles

4. Where did all the antimatter go?

Physicists don’t know why we exist. According to theory, after the big bang the universe was equal parts matter and antimatter, which annihilate one another when they meet. This should have eventually resulted in a lifeless universe devoid of matter. But instead, our universe is full of matter, and antimatter is rare—somehow, the balance between matter and antimatter tipped. With the upgraded LHC, experiments will be able to precisely test how matter might differ from antimatter, and how our universe came to be.

5. What was our infant universe like?

Just after the big bang, our universe was so hot and dense that protons and neutrons couldn’t form, and the particles that make them up—quarks and gluons—floated in a soup known as the quark-gluon plasma. To study this type of matter, the LHC produces extra-violent collisions using lead nuclei instead of protons, recreating the fireball of the primordial universe. Aided by the new LHC’s higher rate of collisions, scientists will be able to take more baby photos of our universe than ever before.

See the full article here.

The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

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From NBC: “After the Higgs, LHC Rounds Up the Unusual Suspects in Particle Physics”

NBC News

February 14th 2015
Alan Boyle

Supersymmetry and dark matter, neutralinos, gravitinos and gluinos … you can expect exotic topics like these to be spinning around as the Large Hadron Collider ramps up to smash subatomic particles again over the next couple of months.

LHC at CERN

Physicists say the first hints of unconventional physics, such as evidence for the existence of those weird-sounding gluinos, could emerge within the next few months. Or not.

It’s been almost three years since scientists at Europe’s CERN particle physics lab announced that the world’s most powerful collider had found the Higgs boson, a mysterious particle whose existence was predicted almost a half-century earlier. It’s been two years since the LHC was shut down for repairs and upgrades. Now thousands of physicists are getting ready to send beams of protons through the machine for the first time since 2013.

“The beam is knocking at the door,” Frederick Bordry, CERN’s director for accelerators and technology, said Saturday during a preview of the LHC’s second experimental run at the annual meeting of the American Association for the Advancement of Science, here in San Jose.

Bordry said the LHC’s supercooled magnets are being prepared for the first proton beams to start circulating around the end of March. Scientific observations would begin after a two-month conditioning period, or by the end of May, he said.

“Don’t kill me if we are taking three or four days more,” he joked.

LHC gets an energy boost

It has taken decades to plan and build the $10 billion Large Hadron Collider and its four main detectors, housed in tunnels that run 300 feet (100 meters) beneath the countryside at the French-Swiss border. Now Bordry and others at CERN have mapped out a schedule of experimental runs and maintenance periods to keep the LHC on the frontier of physics until at least 2035.

The upcoming run is scheduled to last until 2017. During that time, the LHC will ramp up to smash protons together at 60 percent higher energies than it did at the end of its initial run: 13 trillion electron volts, or 13 TeV, as opposed to 8 TeV. Moreover, the beam luminosity will be three times higher.

That means the collider’s detectors should be detecting Higgs bosons — particles that are associated with the process that imparts mass to other subatomic particles — at five times the frequency, said Beate Heinemann, a physicist at the University of California at Berkeley and the Berkeley Lab who’s part of the LHC’s ATLAS experimental group.

ATLAS

Heinemann said the boost in the LHC’s capabilities should also improve scientists’ chances of detecting gluinos, a theoretical particle predicted by supersymmetry theory, by a factor of 60.

Hints of weirdness

Heinemann and her colleagues said the collider’s initial three-year run has already pointed to some apparent discrepancies with the Standard Model, the theory that currently holds sway in particle physics. However, those discrepancies have not yet shown up at a confidence level that would persuade scientists that something weird was really going on.

The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

If the weirdness is real, the LHC could provide evidence for it during the upcoming run, perhaps as soon as August or September, Heinemann told reporters.

The new phenomena could take the form of supersymmetric particles, as-yet-undetected bits of matter that would add an elegant twist to the Standard Model. One such particle could be a gluino, the supersymmetric partner of a known particle called the gluon.

Other hypothesized supersymmetric particles include neutralinos, which could account for the universe’s mysterious dark matter; and gravitinos, which could help explain dark matter as well as some of the mysteries surrounding gravity. The discrepancies also could be caused by a new breed of fourth-generation quark, Heinemann said.

Supersymmetry theory, or SUSY, suggests that each fundamental subatomic particle we’ve detected to date has a yet-to-be-discovered partner with complementary characteristics. The red box highlights the gluino, a particle that physicists believe could be detected at the Large Hadron Collider. If it exists, that is.

However, there’s also a chance that the apparent discrepancies are nothing more than statistical glitches. That’s what happened a couple of years ago, when physicists saw hints pointing to the existence of a second kind of Higgs boson — only to watch those hints fade away as more readings were taken.

“When you put a thousand physicists in a room to do data analysis, and each one of them makes 100 or 1,000 data plots, you’re likely to get statistical anomalies now and then — just like monkeys in the room typing out Shakespeare plays. Things happen,” said UCLA physicist Jay Hauser, a member of the LHC’s CMS collaboration.

CMS

He said the data anomalies will provide a focus for future observations.

“If it’s statistics, they’ll probably go away or diminish,” Hauser said. “If it’s real and interesting, then the effect will grow, and we get really excited.”

Fermilab physicist Don Lincoln discussed the upcoming restart of the Large Hadron Collider — and the discoveries that may lie ahead — with NBC News’ Alan Boyle earlier this month on “Virtually Speaking Science.”

Read the pre-show interview, and listen to the hourlong podcast via BlogTalkRadio or iTunes.

See the full article here.

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30 Rock

From Symmetry: “What’s new for LHC Run II”

Symmetry

February 13, 2015
Sarah Charley

The most powerful particle accelerator on Earth has been asleep for the past two years. Soon it will reawaken for its second run.

LHC

Since shutting down in early 2013, the LHC and its detectors have undergone a multitude of upgrades and repairs. When the particle accelerator restarts, it will collide protons at an unprecedented energy: 13 trillion electron volts. Scaled up into our macroscopic world, the force of these proton-proton collisions is roughly equivalent to an apple hitting the moon hard enough to create a crater 6 miles across.

The upgraded capabilities of the ATLAS, CMS, ALICE and LHCb detectors—plus the LHC’s extra boost of power—will give scientists access to a previously inaccessible realm of physics.

ATLAS

CMS

ALICE

LHCb

To the Higgs boson …and beyond!

In the first run of the LHC, the ATLAS and CMS experiments ended the 50-year hunt for the Higgs boson, which was predicted the Standard Model of particles and forces. Now scientists want to know if the Higgs they found is hiding any surprises.

The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

“All the properties of the Higgs boson are already predicted by the Standard Model, so it’s our job to go out and measure those properties and see if they agree,” says Jay Hauser, a UCLA physicist working on the CMS experiment. “If anything disagrees, it could be a window to new physics.”

Because the Higgs boson loves mass, scientists suspect that it might interact with a range of hidden, massive particles that we cannot see, such as dark matter. If the Higgs boson is dancing with any undiscovered physics, scientists should see evidence of this in the way the Higgs behaves.

But even if the Higgs agrees with all predictions, something about it still seems a bit strange.

“The Higgs mass doesn’t make any sense,” says Beate Heinemann, a Berkeley physicist and the deputy head of the ATLAS experiment. “It would make much more sense if it was much heavier, which is why we think there must be something that protects the Higgs boson and gives it a lower mass.”

This Higgs bodyguard could be anything from supersymmetric particles to dark matter to extra dimensions.

Standard Model of Supersymmetry

“We have quite a few puzzles,” Heinemann says. “We think that there should be new physics at this energy scale, but we don’t know what it is yet.”

Bringing it back to the big bang

Scientists on the ALICE experiment have their sights on something else.

In the beginning, the entire universe—all the stars, planets and galaxies—were part of a hot soup of matter called quark gluon plasma. The LHC can recreate those conditions in miniature by colliding beams of heavy atomic nuclei, which it does for four weeks per year. The ALICE detector specializes in investigating the properties of this primordial material.

“The quark gluon plasma is so hot that ordinary protons and neutrons cannot exist in it,” says Peter Jacobs, a Berkeley physicist working on the ALICE experiment. “Quarks and gluons move around in it and interact in new ways that we haven’t seen before. It’s a new form of matter and we want to know how it behaves and what its properties are—like its structure and how it acts at different temperatures.”

In the first run of the LHC, the ALICE experiment was able to characterize many aspects of this weird semi-liquid plasma, such as its viscosity.

“The quarks and gluons interact more than we originally thought, indicating that the quark-qluon plasma is more like a liquid than a gas; indeed, almost as “perfect” a liquid as nature allows,” Jacobs says.

But there is still more to investigate.

“Run I was a discovery run, and we were able to explore many new things and developed a lot of curiosities,” Jacobs says. “During Run II, we will be able to explore these curiosities more deeply and give them quantitative values instead of just being able to describe them qualitatively.”

The case of the missing antimatter

Scientists suspect that the big bang acted like a universe-sized supercollider that brought equal parts of matter and antimatter into existence. But where did all of the antimatter go?

The LHCb experiment is one of the world’s best early-universe detectives and looks for clues in the case of the disappearing antimatter.

“We should have started with equivalent amount of matter and antimatter in the universe,” says Michael Williams, an MIT physicist working on the LHCb experiment. “But now, all we see is matter, and there is no way the Standard Model can explain this huge discrepancy. There must be some other way matter and antimatter behave differently.”

To uncover the root of this huge discrepancy, the LHCb experiment does precision measurements of subatomic processes. LHCb scientists then compare the Standard Model predictions with these experimental observations to see how well they match up.

Thus far, the Standard Model has been hard to break. But Williams thinks that increasing the precision of these measurements could start to show where the cracks are.

“You never know if you’re on the cusp of making a discovery,” Williams says. “In Run II, we will measure lots of processes with a much higher precision, and this might reveal something that the Standard Model is not explaining.”

See the full article here.

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Symmetry is a joint Fermilab/SLAC publication.

Amazing CERN Photo Essay From NBC News: “World’s Biggest Particle Smasher Gears Up for Next Run”

After the discovery of the Higgs boson, or “God Particle,” in 2012, Europe’s giant particle accelerator at CERN has been getting an overhaul.

1. Scientists at the CERN particle physics center at the French-Swiss borders are preparing to restart the Large Hadron Collider (LHC), the world’s most powerful particle-smasher. Photographer Luca Locatelli was given access to maintenance work in November, providing a unique view into this vast underground laboratory. Engineers work on equipment for the LHC in the main workshop at CERN shown here.

2. A model of the Large Hadron Collider is displayed inside the LHC Magnet facility building, where components for the particle accelerator are built. The LHC was first started up in 2008 and is resuming high-energy collisions in March.

3. The LHC’s 17-mile-round underground tunnel directs particles through ATLAS, one of the facility’s two general-purpose detectors. ATLAS and the other detector, the Compact Muon Solenoid [CMS], probe a wide range of scientific mysteries, from the successful search for the Higgs boson to the hunt for extra dimensions and particles that could make up dark matter.

4. A scientist works inside one of the underground rooms of the Compact Muon Solenoid, another of LHC’s general-purpose detectors. The CMS experiment is one of the largest international scientific collaborations in history, involving 4,300 particle physicists, engineers, technicians, students and support staff from 182 institutes in 42 countries.

5. Maintenance work continues inside the CMS. The CMS detector is built around a huge solenoid magnet. This takes the form of a cylindrical coil of superconducting cable that generates a field of 4 tesla, about 100,000 times the strength of Earth’s magnetic field.

6. A unusual feature of the CMS detector is that instead of being built in place like the LHC’s other detectors, it was constructed in 15 sections at ground level before being lowered into an underground cavern and assembled. The complete detector is 70 feet long, 50 feet wide and 50 feet high (21 by 15 by 15 meters).

7. The last bit of maintenance work is perfomed inside the ALICE (A Large Ion Collider Experiment) before it resumes operation in 2015. ALICE is a heavy-ion detector that’s designed to study the physics of strongly interacting matter at extreme energy densities.

8. The ALICE detector sits in a vast cavern almost 200 feet (56 meters) below ground, close to the village of St Genis-Pouilly in France. When ALICE is in operation, the engineers in charge of the LHC switch from using beams of protons to beams of lead ions.

9. The ALICE collaboration uses a 10,000-ton detector – 85 feet long, 50 feet high and 50 feet wide (26 by 16 by 16 meters) – to study quark-gluon plasma, the “Big Bang soup” that existed when the universe was a trillionth of a second old.

10. In addition to the experiments at the LHC, scientists at the CERN particle physics center conduct huge numbers of smaller experiments. A bird’s-eye view shows one of the experiments in progress.

11. The Antiproton Decelerator provides low-energy antiprotons, mainly for studies of antimatter. Previously, “antiparticle factories” at CERN and elsewhere consisted of chains of accelerators, each performing one of the steps needed to provide antiparticles for experiments. Now the Antiproton Decelerator performs all the necessary steps, from making the antiprotons to delivering them to experiments. At CERN, scientists have used the antiprotons to create atoms of antihydrogen for a fraction of a second.

12.The 7,000-ton ATLAS detector is the largest particle detector ever constructed in terms of volume. ATLAS and the Compact Muon Solenoid, or CMS, were instrumental in the successful search for the Higgs boson at the Large Hadron Collider.

And, for good measure, the 2008 video The Big Bang Machine from BBC. This video is from before the LHC started up. But, in my view, it is the best teaching video on both the LHC and
particle physics involved in its experiments. This video features Sir Dr. Brian Cox, University of Manchester. Brian worked or works on the ATLAS project. He spent some time at FNAL’s Tevatron and does not leave it out as has been done by others. There are more recent videos. They simply do not do as well in communicating this story.

Watch, enjoy, learn.

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From CERN- “LHC Season 2: holding the key to new frontiers”

12 Jan 2015
Cian O’Luanaigh

This year, the Large Hadron Collider (LHC) will restart at the record collision energy of 13 TeV, following a two-year long shutdown (LS1) for planned maintenance. To mark this, today saw the LS1 activities coordinator symbolically handing over the LHC key to the operations team. The team will now perform tests on the machine in preparation for the restart this spring.

LHC

After three years of highly successful running, the LHC was shut down for maintenance in 2013. Since then, engineers and technicians have been repairing and strengthening the 27-kilometre accelerator in preparation for its restart at 13 TeV. Some 18 of the 1232 dipole magnets that steer particle beams around the accelerator were replaced, and more than 10,000 electrical interconnections between the magnets were strengthened. The LHC’s vacuum, cryogenics and electronics systems were also consolidated.

“It’s important to stress that after the long shutdown, the LHC is essentially a new machine,” said CERN Director-General Rolf Heuer in his New Year address at CERN last week.

The collision energy of 13 TeV is a significant increase compared with the initial three-year LHC run, which began at 7 TeV and rose to 8 TeV. In addition, in the run that starts this year, bunches of protons in the accelerator will collide at briefer intervals – 25 nanoseconds(ns) between them instead of 50 ns – and the beams will be more tightly focused. All these factors are aimed at optimising the delivery of particle collisions for physics research.

With collisions at energies never reached in a particle accelerator before, the LHC will open a new window for discovery, allowing further studies of the Higgs boson and the potential to address unsolved mysteries such as dark matter.

The LHC is CERN’s flagship machine, but the accelerator complex also provides a broad programme of research that makes many contributions to fundamental physics. The long shutdown has allowed teams throughout CERN to upgrade experiments, detectors, accelerators and equipment.

In addition, the laboratory has continued to nurture its collaborations around the world with involvements in future collider studies, showing CERN’s dedication to the future of particle physics at the very forefront of knowledge.

It will be a busy year ahead, and with so much in store the laboratory looks forward to LHC Season 2 and more!

See the full article here.

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Meet CERN in a variety of places:

Cern Courier

THE FOUR MAJOR PROJECT COLLABORATIONS

ATLAS

ALICE

CMS

LHCb

LHC

Quantum Diaries

From Huff Post: “The Future of Physics”

The Huffington Post

01/26/2015

Dr. Sten Odenwald, Astronomer, National Institute of Aerospace

In another few months the Large Hadron Collider. will be powered up to explore its maximum energy range. Many physicists fervently hope we will see definite signs of “new physics,” especially a phenomenon called “supersymmetry.” In the simplest view, the Standard Model souped-up with supersymmetry will offer a massive new partner particle for every known particle (electron, quark, neutrino, etc). One of these, called the neutralino, may even explain dark matter itself!

LHC at CERN

Standard Model of Supersymmetry

But Wait, There’s More!

Supersymmetry is the foundational cornerstone on which string theory rests. That’s why physicists call this “stringy” theory of matter “superstring theory.” If the LHC does not turn up any signs of supersymmetry during the next two or three years, not only will simple modifications to the current Standard Model be ruled out, but the most elegant forms of supersymmetry theory will fall too.

As an astronomer I am not too worried. The verified Standard Model is now fully capable of accounting for everything we see in the universe since a trillion-trillion-trillionth of a second after the Big Bang to the present time, once you include gravity, and don’t worry too much about dark matter and dark energy.

The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

But we need some explanation for dark energy and dark matter to complete our understanding of the cosmos, and for that we still need our physicist friends to show the way. Currently their only answers involve supersymmetry theory. If this idea falls, astronomers will be completely stumped to explain what governs our universe on the largest scales.

Beyond supersymmetry, we also have the huge investment of talent that has pursued superstring theory since the early 1980s. Without supersymmetry, the “super” part of string theory also falls, and you end up with a non-super string theory that is clunky, inelegant and pretty dismal in accounting for the finer details of our physical world, often termed “quantum gravity.” A big part of this is the idea that our universe inhabits more than four dimensions — perhaps as many as 11!

On April 26, 2006, I had the following exchanges with Stanford theoretical physicist Leonard Susskind, who is widely regarded as one of the fathers of string theory, along with other provocative and foundational ideas such as the “holographic universe.” His comments are still relevant seven years later.

Odenwald: Why is it so important for physicists to consider the universe having more than four dimensions, as the mathematics of superstring theory seems to require?

Susskind: Almost all working high-energy theoretical physicists are convinced some sort of extra dimensions are needed to explain the complexity of elementary particles. That particles move in extra dimensions is another way of talking about the fact that they have more complex properties than just position and velocity. It is hard to find a serious paper about particle phenomenology that doesn’t in some way use the tools of superstring theory. Furthermore, we all agree that the origin of elementary particles is most likely at the planck scale and cannot be understood without a good theory of quantum gravity.

Odenwald: So if superstring theory were found to be an incorrect model for our particular universe, is that like turning the clock back to circa 1978 in physics?

Susskind: I agree that going back to the ’70s would be turning the clock back in the sense that we would be ignoring the vast amount of mathematical knowledge that has been gained over the subsequent years, mostly from string theory. That is just not going to happen. The changes in our theoretical understanding of quantum field theory, gravity, black holes, are completely irreversible. [String theory mathematics] has even worked its way into nuclear physics and heavy ion collisions as well as into condensed matter physics.

Odenwald: Kind of a hard place for modern theoreticians to revisit, but for astronomy and cosmology the 1970s seem not such a bad place. Without superstring theory, we would still have cosmological inflation. Without superstring theory, what happened at the instant of the Big Bang would remain unknown, logically indescribable, and still a great puzzle… as it always has.

Susskind: [Not quite.] Recent cosmology has been completely dominated by studying the cosmic microwave background [CMB] and inflationary theory.

CMB per ESA/Planck

ESA/Planck

Gravitational waves from BICEP2 in support of Inflation theory not yet accepted

BICEP2

The CMB fluctuation spectrum is widely understood as a quantum effect. Inflation is a gravitational effect. Is there any question that quantum gravity (quantum plus gravity) will be the framework for understanding the early universe? No, there is not. Also I might add that the old inflation that you are referring to was a disaster. It didn’t work. Many inflationary cosmologists like Linde, Vilenkin, and Guth are looking to string theory for possible answers to the puzzles of inflation.

Odenwald: Is it fair to say that superstring theory is “too big to fail”? I am reminded of the alledged quotation by Einstein as he was awaiting news about a major test of relativity in 1919. A reporter is said to have asked, “Well, what would it mean if your theory is wrong?” to which Einstein allegedly replied, “Then I would feel sorry for the good Lord; the theory is correct!” Is the physics community in the same predicament because superstring theory is a “beautiful” theory that seems to explain so much, and its mathematics is so impeccable that it is used in other theoretical settings in physics?

Susskind: Exactly right. However, it is fair to say that while theorists were developing powerful tools, they mostly had wrong expectations for what the theory was indicating. Most theorists hoped that string theory would lead to an absolutely unique set of particles, coupling constants, with exactly vanishing cosmological constant. What we have learned from the theory itself is that it is a theory of tremendous diversity. Unexpectedly, string theory is most comfortable with a huge multiverse of tremendous variety instead of the small “knowable” and unique universe we once imagined.

Odenwald: So what would our theoretical explanations for our universe look like without added dimensions, quantum gravity or string theory?

Susskind: Without these things the world as we know it couldn’t exist. Giving up quantum gravity means giving up either the ideas of quantum [mechanics] or of gravity [and general relativity]. In a cosmological context quantum gravity is responsible for the primordial density fluctuations [we directly observe in the CMB] that ultimately condensed to form stars, galaxies, planets, etc. Without string theory we should not have the diversity of possibilites that allow pocket universes [Alan Guth’s term] with the ultra-fine tuning needed to insure conditions for our kind of life.

Odenwald: If string theory loses its experimental support at the LHC, wouldn’t it be far worse than merely going back to cosmology circa 1975 or even 1965? We would have to question the very mathematical tools we have been using for the last 50 years!

Susskind: I agree with your analysis, except that I would add: Expect the unexpected. Unforseen surprises are the rule in science, not the exception. Remember: Stuff happens.

Odenwald: If superstring theory falls, are there any competing theories out there that could hold out some hope?

Susskind: Not as far as I know.

• * * * *

So there you have it. The Large Hadron Collider absolutely has to find some clue about supersymmetry, or superstring theory is compromised, we will have no good idea about dark matter, and we will definitely be in a bad place until the super-LHC is built in the 2030s.

Patience, however, is a still a necessary virtue. Physicists were in this same quandary before the Higgs boson was finally discovered after 50 years of increasingly panicked searching.

See the full article here.

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From Symmetry: “Superconducting electromagnets of the LHC”

Symmetry

January 23, 2015

This article was written by Don Lincoln, Fermi National Accelerator Laboratory

You won’t find these magnets in your kitchen.

Photo by Maximilien Brice, CERN

Magnets are something most of us are familiar with, but you may not know that magnets are an integral part of almost all modern particle accelerators. These magnets aren’t the same as the one that held your art to your parent’s refrigerator when you were a kid. Although they have a north and south pole just as your fridge magnets do, accelerator magnets require quite a bit of engineering.

When an electrically charged particle such as a proton moves through a constant magnetic field, it moves in a circular path. The size of the circle depends on both the strength of the magnets and the energy of the beam. Increase the energy, and the ring gets bigger; increase the strength of the magnets, the ring gets smaller.

The Large Hadron Collider is an accelerator, a crucial word that reminds us that we use it to increase the energy of the beam particles. If the strength of the magnets remained the same, then as we increased the beam energy, the size of the ring would similarly have to increase. Since the size of the ring necessarily remains the same, we must increase the strength of the magnets as the beam energy is increased. For that reason, particle accelerators employ a special kind of magnet.

LHC at CERN

When you run an electric current through a wire, it creates a magnetic field; the strength of the magnetic field is proportional to the amount of electric current. Magnets created this way are called electromagnets. By controlling the amount of current, we can make electromagnets of any strength we want. We can even reverse the magnet’s polarity by reversing the direction of the current.

Given the connection between electrical current and magnetic field strength, it is clear that we need huge currents in our accelerator magnets. To accomplish this, we use superconductors, materials that lose their resistance to electric current when they are cooled enough. And “cooled” is an understatement. At 1.9 Kelvin (about 450 degrees Fahrenheit below zero), the centers of the magnets at the LHC are one of the coldest places in the universe—colder than the temperature of space between galaxies.

Given the central role of magnets in modern accelerators, scientists and engineers at Fermilab and CERN are constantly working to make even stronger ones. Although the main LHC magnets can generate a magnetic field about 800,000 times that generated by the Earth, future accelerators will require even more. The technology of electromagnets, first observed in the early 1800s, is a vibrant and crucial part of the laboratories’ futures.

See the full article here.

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Symmetry is a joint Fermilab/SLAC publication.

From FNAL “Frontier Science Result: CMS Stealth SUSY”

Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

Friday, Jan. 16, 2015

This column was written by Don Lincoln

Stealth SUSY is a theory of supersymmetry that doesn’t have the usual signatures expected in more common supersymmetric models. Collisions in which stealth SUSY appears look much like the ordinary collisions of the Standard Model. A recent analysis studied CMS data to see if any evidence of stealth SUSY could be found.

Don Lincoln on supersymmetry

The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

With the impending resumption of operations of the LHC, scientists often discuss what they think will be the next big discovery. While it is hard to make predictions, CERN odds-makers are leaning toward a discovery that incorporates supersymmetry, or SUSY, as the clear favorite.

LHC at CERN

Theories that incorporate SUSY can easily explain why the mass of the Higgs boson is so much lower than one would naturally expect. In fact, it is this aspect of SUSY that has intrigued physicists for decades, leading to more than 10,000 theoretical and experimental papers on the subject. Thus far, in spite of the best efforts by very smart people at both the Fermilab Tevatron and the CERN Large Hadron Collider, no experimental evidence has been found that SUSY is true.

Tevatron at FNAL

Supersymmetric theories predict a whole class of supersymmetric particles that are cousins to the familiar particle of the Standard Model. In the most common models, these new particles are all unstable, except for the lightest supersymmetric particle (or LSP). From our measurements, we know that the LSP (if it exists) is massive, stable and electrically neutral. (The LSP is actually a leading candidate for dark matter, and this is another reason that SUSY is considered an attractive idea.)

Standard Model of supersymmetry

LSPs do not interact very much with ordinary matter and thus will escape any particle collision that produces them without leaving a trace in a particle detector. Using the principle of momentum conservation, we know that the momentum perpendicular to the particle beams must be zero. If we add up the visible momentum and it isn’t zero, we can infer that a particle escaped our detector. Given that LSPs can escape, events with a high momentum imbalance are ideal for searching for SUSY.

The problem is that we have studied events with these characteristics and have seen no evidence for the existence of SUSY. This has led theoretical physicists to invent new theories that predict little or no momentum imbalance. For instance, one such idea postulates that there exist new particles that interact very little with ordinary matter. In this model, the new particle and its supersymmetric cousin have very similar masses. This similarity in mass means that the LSP can have very little momentum, thus no striking momentum imbalance is expected. Theories with this property are generically called stealth SUSY.

CMS scientists studied a class of events with little missing momentum, the signature of W and Z bosons, along with jets from quark production, trying to see if they might find stealth SUSY. No evidence was found. This measurement was used to exclude some parameters in stealth SUSY models.

CMS in the LHC at CERN

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Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

From Dennis Overbye at NYT: “An Ambassador for Physics Is Shifting His Mission”

The New York Times

JAN. 12, 2015

Dennis Overbye

The Compact Muon Solenoid Experiment, among others, has helped CERN become a leader in particle physics once again. Credit Denis Balibouse/Reuters

Rolf-Dieter Heuer, a crinkly-eyed German with a snowy goatee, showed up at the Four Seasons, the perennial Manhattan power lunch spot, dressed like the physicist he is — in a sweater and baggy jeans for the red-eye to Geneva — rather than the diplomat he had just been playing.

The United Nations was in session, and Dr. Heuer, the director-general of the European Organization of Nuclear Research, or CERN, had a featured role in events celebrating the laboratory’s 60th anniversary.

In 2009, when he took over, dark clouds were hanging over CERN, the world’s largest physics lab.

A few months before, the lab’s new Large Hadron Collider, the most expensive particle accelerator ever built, had blown up, indefinitely delaying the hunt for new particles, new forces and even perhaps new dimensions of nature. Some scientists were taking their research to a competing collider at the Fermi National Accelerator Laboratory in the United States. The worldwide economy was collapsing, as if into the black hole some alarmists had predicted the collider would make.

LHC at CERN

Tevatron at FNAL

Under Rolf-Dieter Heuer, who is in his last year at the helm, CERN has been revived as a leader in particle research. Credit Gerard Julien/Agence France-Presse — Getty Images

Now he looks fondly on those days. “If you start with such a low point, you can show your team was able to bring everything out of a low point up to a high point,” he said.

Dr. Heuer, 66, is entering the last year of his term; in 2016, Fabiola Gianotti, an Italian particle physicist, will take over as the director. Dr. Heuer will become the director of the German Physical Society.

Fabiola Gianotti

If he rode in under dark clouds, he will ride out on a white horse. It was Dr. Heuer who stood up on the morning of July 4, 2012, in front of the world’s physicists and said, “I think we have it,” declaring an end to the half-century chase for the Higgs boson, a keystone of modern physics that explains why elementary particles have mass.

CERN, formed after World War II to rekindle European science, now has 21 member states. The newest, and the only one outside Europe, is Israel. The United States, which has observer status at CERN, is not a member but played a big role in building and operating the Large Hadron Collider.

In December, Dr. Heuer went to Islamabad to sign up Pakistan as an associate member. He said his long-term dream was a network of international labs, “islands where people can work together independently of the political situation in their home country.”

Dr. Heuer, born in Bad Boll in southern Germany in 1948, has spent his career in the trenches of particle physics, in which scientists emulate 3-year-olds by smashing bits of matter together to see what comes out.

He has no heroes, but said he had learned the ropes from his teachers. One indelible moment came when his Ph.D. supervisor at the University of Heidelberg, Joachim Heintze, tore up the first draft of his dissertation, saying it was too detailed. “It was amazing,” Dr. Heuer said. “A clear string of logic was missing. And that was the last time it was missing.”

He went on: “It was a memorable meeting. Since then, I propagate that message: When you have a problem, make sure you speak it out, and then it is forgotten.”

He had an opportunity to put that philosophy to the test early in his term at CERN, when physicists reported in a seminar there that they had measured subatomic particles known as neutrinos streaming from Geneva to their detector in Italy faster than the speed of light, contrary to the laws of physics then known.

Dr. Heuer was criticized for letting CERN be used as a platform for a result everybody believed was probably wrong. (The researchers later realized they had plugged their equipment together wrong.) In the end, Dr. Heuer said, nobody was fooled and the kerfuffle was fun, an example of the scientific process. Given the choice now, he said, he would do it again.

“I don’t think it’s up to the director-general to act like a censor if the result is against what everyone believes,” he said.

The neutrino controversy helped set a sort of dubious stage for the main event in particle physics so far this century: the Higgs boson.

Energy is the coin of the particle physics realm. The more energy with which two particles can be collided and transformed, the more intimately nature can be studied. The Large Hadron Collider was designed to be powerful enough to shake loose the Higgs boson.

“I think everybody was surprised it went so fast,” Dr. Heuer said of the Higgs hunt, especially because the collider had to be operated at only half its capability to avoid straining its circuits after the 2009 explosion.

It will start up again in March, running close to full strength for the first time, with proton bullets of 6.5 trillion electron volts — enough energy, scientists hope, to break into new ground.

The Higgs boson completed the Standard Model, a suite of equations that agrees with all the experiments that have been done on earth. But that model is not the end of physics. It does not explain dark matter or dark energy, the two major constituents of the cosmos, for example, or why the universe is made of matter instead of antimatter.

The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

For decades, theorists have flirted with a concept called supersymmetry that would address some of these issues and produce a bounty of new particles for CERN’s collider.

“At the beginning, everyone was assuming supersymmetry was around the corner,” Dr. Heuer said, “and it would be the first thing to be detected.” It was not, nor has any deviation from the Standard Model predictions for the Higgs yet been recorded, disgruntling many theorists who hoped for a clue to the next great theory.

Standard MOdel of supersymmetry

Dr. Heuer is not among them — yet. “It’s not up to us to be disappointed by something nature has given us,” he said.

“On the one hand, it is fantastic how well the Standard Model works,” he said. “On the other hand, it’s frustrating how it holds against all precision tests.”

“If nothing shows up in the next runs, then one has to scratch the head,” he said.

The CERN collider has years yet to run, but the world’s physicists are already pondering even bigger colliders. Last summer, Chinese physicists announced a proposal to build a pair of colliders 32 miles around, twice as big as CERN’s. With international support, they said, the machines could be scaled up to reach energies of 100 trillion electron volts. Not to be outdone, CERN scientists have suggested tunneling under Lake Geneva to build a supercollider. Japan is also interested in having a Higgs factory built there.

It takes more than national pride and curiosity to build a multibillion-dollar particle accelerator. The Large Hadron Collider, Dr. Heuer said, had a natural justification: It would be powerful enough to find the Higgs boson, or whatever else made particles have mass.

“It was a no-lose theorem,” he said.

Without a clearer theory about how nature works at higher energies, however, there is no specific prediction for bigger machines to test. The energy value of 100 trillion electron volts, he conceded, is just a nice round number.

“This no-lose scenario does not exist for 100 TeV,” he said. To propose a new machine without such a killer app, he said, “you have to have a very good argument you can explain in a relatively clear-cut way.”

Can that be done? Do taxpayers and everybody else have a hope of understanding what the physicists are doing?

“That depends on your effort, sir,” he answered.

“The math behind it — forget it, even for me,” said Dr. Heuer, admitting that he is not fluent in quantum field theory, the body of math from which the Higgs springs. “I’m not a theorist.”

But he went on, “The answer is yes: You should be able to understand at least the logic behind it. You can explain to interested laymen.”

“Of course,” he said, “they will forget it two hours later. I know how it is when I learn something new.”

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From Daily Mail: “Will the Large Hadron Collider find dark matter? Atom smasher could soon solve one the universe’s greatest mysteries, claims scientist”

Daily Mail

31 December 2014
Jonathan O’Callaghan

Dr Monica Dunford worked at Cern in Switzerland up until 2013
She was directly involved in the detection of the Higgs boson in 2012
Speaking to MailOnline she said of the time leading up to its discovery: “I don’t think there will be another time like that in my career for sure”
But she said that the Large Hadron Collider could find dark matter
And if it did it would be a ‘bigger discovery’ than the Higgs boson
In March 2015 the LHC will be restarted at double its previous power

In 2012, the science world broke into celebration with the announcement that the Higgs boson – sometimes controversially referred to as the ‘God particle’ – had been found. The discovery of the particle, which is believed to give mass to matter, was a crowning achievement and justification for the Large Hadron Collider (LHC) in Cern. But one scientist has told MailOnline we can expect even greater discoveries from the collider in the coming years – and one in particular could be the most important in history.

LHC at CERN

Dr Monica Dunford, originally from California and now a researcher at the University of Heidelberg in Germany, worked at Cern in Switzerland until 2013.

She is one of six scientists who feature in the widely acclaimed documentary Particle Fever, which chronicles the first round of experiments at the LHC at Cern in 2008, leading up to the discovery of the Higgs boson in 2012.

On whether it would be the LHC’s most important discovery to date, she said: ‘Personally yes. It would be a bigger discovery than the Higgs boson. ‘For the Higgs we had a very good concrete theoretical prediction; for dark matter we really have no idea what it would be.’ She added: ‘There is no particle that we know of today that can explain dark matter, let alone what dark energy might be. ‘So if we could directly produce dark matter particles at the LHC this would be a huge step forward in our understanding of the composition of the universe!’

Dr Monica Dunford (pictured), originally from California and now a researcher at the University of Heidelberg in Germany, worked at Cern in Switzerland until 2013. She is one of six scientists who feature in the widely acclaimed documentary, which chronicles the moments leading up to the discovery of the Higgs. (CERN)

If the LHC does one day find dark matter, it will be interesting to see if the moments leading up to it are as tense as those before the Higgs boson was found.

HIGGS BOSON VS DARK MATTER
They might seem quite different, but both the Higgs boson and dark matter particles may have some similarities. The Higgs boson is thought to be the particle that gives matter its mass. And in the same vain, dark matter is thought to account for much of the ‘missing mass’ in galaxies in the universe. It may be that these mass-giving particles have more in common than was thought. However, at the time some scientists, including Stephen Hawking, had actually been championing the non-discovery of the particle. In 2013 he was quoted as saying it would have been ‘far more interesting’ if it hadn’t been found, as it would have allowed for new theories of the universe to be formulated. And Dr Dunford agrees that it could have been just as interesting had the Higgs not been found.
‘Nature is what nature is,’ she said. ‘We’re trying to unlock its secrets. ‘We believed the Higgs was there, but if nature had something different in mind, all the better. We would have to go back to the drawing board. ‘It wouldn’t have been a failure, it would have been equally exciting to not see anything, but more work for my theory colleagues.

The existence of the Higgs boson was put forward in the 1960s by British physicist Dr Peter Higgs (pictured) to explain why the tiny particles that make up atoms have mass. It has been described as the ‘missing piece’ of the Standard Model, which explains how the parts of the universe that we understand interact

The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

LHC TO BE TURNED ON AT DOUBLE POWER IN MARCH
Cern’s Large Hadron Collider will be turned back on in March 2015 – at double power. The world’s biggest particle collider, located near Geneva, has been undergoing a two-year refit and had been offline since February 2014. Work is now ‘in full swing’ to start circulating proton beams again in March, with the first collisions due by May, the European Organisation for Nuclear Research (Cern) said in a statement. ‘With this new energy level, the (collider) will open new horizons for physics and for future discoveries,’ said Cern Director General Rolf Heuer.

‘I’m looking forward to seeing what nature has in store for us.’ The goal for 2015 will be to run with two proton beams in order to produce 13 TeV (teraelectronvolts) collisions, an energy never achieved by any accelerator in the past.

The chances of finding dark matter at the LHC, though, are unknown at the moment. Many theories predict its existence, particularly within the Standard Model of physics, but if it can’t be found it may require an even greater machine that the LHC. Next year it will double the energy of the two proton beams it collides to 13TeV (teraelectronvolts), an energy never achieved by an accelerator before.

Dr Dunford says this will give it ‘a lot of potential’ to find new particles – possibly dark matter – or even other particles not in our current understanding of nature. Whatever the future holds for the LHC, the project so far is a testament to what can be achieved through international cooperation. ‘One of the things people don’t appreciate about Cern is it’s an incredibly international organisation, all achieving the same goals,’ Dr Dunford adds. ‘I hope a lot of the media attention inspires people to realise why fundamental physics is important.’

Particle Fever – Unravel the mysteries of the Large Hadron Collider

See the full article here.

WHAT IS DARK MATTER?
When physicists study the dynamics of galaxies and the movement of stars, they are confronted with a mystery. If they only take visible matter into account, their equations simply don’t add up: the elements that can be observed are not sufficient to explain the rotation of objects and the existing gravitational forces. There is something missing. From this they deduced that there must be an invisible kind of matter that does not interact with light, but does, as a whole, interact by means of the gravitational force. Called ‘dark matter’, this substance appears to make up at least 80 per cent of the universe. Finding the Higgs boson was one of the primary goals of the LHC – but perhaps the LHC’s most important moment is yet to come.‘One of the things I’m most interested in is creating and discovering dark matter,’ Dr Dunford said. ‘We know from measurements of cosmology that 25 per cent of the universe is dark matter and we have absolutely no idea what that is.
‘For comparison, what we do know, electrons and protons, only count for four per cent. ‘You have this huge chunk of a pie and no idea what it consists of. One thing we could possibly produce would be a dark matter candidate via its decay products. ‘Being able to produce it at the LHC would be a huge connection between our astronomical measurements and what we can produce in the laboratory.’

An illustration of dark matter in the universe.

WHAT IS THE HIGGS BOSON?
The Higgs boson’s role is to give the particles that make up atoms their mass. It has been described as the ‘missing piece’ of the Standard Model, which explains how the parts of the universe that we understand interact with one another. Without this mass, particles would zip around the cosmos, unable to bind together to form the atoms that make stars and planets – and people. The particle was confirmed using the Large Hadron Collider – the highest-energy particle collider ever made, built by the European Organisation for Nuclear Research (CERN) in 2012.
However, our knowledge of particle physics is still far from complete, with mysteries such as the nature of dark matter to still be solved. Dr Dunford first came to Cern in 2006, when she was involved in the initial construction and development of the world’s largest particle accelerator.‘In the beginning we were building the detector,’ she said. ‘It was awesome, total stress, but it was great. We were probably a core team of several hundred in the day and night.’ After that initial period, the teams moved onto the ‘much less sexy’ tasks of data analysis from the detector.
‘In the beginning, before the Higgs boson was discovered, there was a lot of tension,’ Dr Dunford continues. ‘We would have these blocks of data and people would be like “is it there? Can we see it?” ‘At the time the announcement was made in 2012, it had risen to a fever pitch.‘I don’t think there will be another time like that in my career for sure.’

That discovery was not only a groundbreaking moment for physics, but also justified the huge cost £5.9 billion ($9.1 billion) of building and operating the LHC.

Finding the Higgs boson was one of the primary goals of the LHC, so the moments leading up to its discovery were understandably tense. Illustrated is one of the proton-proton collisions measured in the Compact Muon Solenoid (CMS) experiment in the search for the Higgs boson.

CMS in the LHC at CERN

Some scientists, including Stephen Hawking (pictured), had actually been championing the non-discovery of the Higgs boson. In 2013 he was quoted as saying it would have been ‘far more interesting’ if it hadn’t been found, as it would have allowed for new theories of the universe to be formulated.

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