Posted on by Jason Major

NOvA Experiment Nabs Its First Neutrinos

The NUmI (Neutrinos from the Main Injector) horn at Fermilab, which fires protons that degrade into neutrinos. (Image: Caltech)

Neutrinos are some of the most abundant, curious, and elusive critters in particle physics. Incredibly lightweight — nigh massless, according to the Standard Model — as well as chargeless, they zip around the Universe at the speed of light and they don’t interact with any other particles. Some of them have been around since the Big Bang and, just as you’ve read this, trillions of them have passed through your body (and more are on the way.) But despite their ubiquitousness neutrinos are notoriously difficult to study precisely because they ignore pretty much everything made out of anything else. So it’s not surprising that weighing a neutrino isn’t as simple as politely asking one to step on a scale.

Thankfully particle physicists are a tenacious lot, including the ones at the U.S. Department of Energy’s Fermilab, and they aren’t giving up on their latest neutrino safari: the NuMI Off-Axis Electron Neutrino Appearance experiment, or NOvA. (Scientists represent neutrinos with the Greek letter nu, or v.) It’s a very small-game hunt to catch neutrinos on the fly, and it uses some very big equipment to do the job. And it’s already captured its first neutrinos — even before their setup is fully complete.

Created by smashing protons against graphite targets in Fermilab’s facility just outside Chicago, Illinois, resulting neutrinos are collected and shot out in a beam 500 miles northwest to the NOvA far detector in Ash River, Minnesota, located along the Canadian border. The very first beams were fired in Sept. 2013, while the Ash River facility was still under construction.

One of the first detections by NOvA of Fermilab-made neutrinos (Image courtesy of NOvA collaboration)
One of the first detections by NOvA of Fermilab-made neutrinos (Image courtesy of NOvA collaboration)

“That the first neutrinos have been detected even before the NOvA far detector installation is complete is a real tribute to everyone involved,” said University of Minnesota physicist Marvin Marshak, Ash River Laboratory director. “This early result suggests that the NOvA collaboration will make important contributions to our knowledge of these particles in the not so distant future.”

The 500-mile (800 km) path of the NOvA neutrino beam (Fermilab)
The 500-mile (800 km) subterranean path of the NOvA neutrino beam (Fermilab)

The beams from Fermilab are fired in two-second intervals, each sending billions of neutrinos directly toward the detectors. The near detector at Fermilab confirms the initial “flavor” of neutrinos in the beam, and the much larger far detector then determines if the neutrinos have changed during their three-millisecond underground interstate journey.

Again, because neutrinos don’t readily interact with ordinary particles, the beams can easily travel straight through the ground between the facilities — despite the curvature of the Earth. In fact the beam, which starts out 150 feet (45 meters) below ground near Chicago, eventually passes over 6 miles (10 km) deep during its trip.

According to a press release from Fermilab, neutrinos “come in three types, called flavors (electron, muon, or tau), and change between them as they travel. The two detectors of the NOvA experiment are placed so far apart to give the neutrinos the time to oscillate from one flavor to another while traveling at nearly the speed of light. Even though only a fraction of the experiment’s larger detector, called the far detector, is fully built, filled with scintillator and wired with electronics at this point, the experiment has already used it to record signals from its first neutrinos.”

The 50-foot (15 m) tall detector blocks are filled with a liquid scintillator that’s made of 95% mineral oil and 5% liquid hydrocarbon called pseudocumene, which is toxic but “imperative to the neutrino-detecting process.”  The mixture magnifies any light that hits it, allowing the neutrino strikes to be more easily detected and measured. (Source)

“NOvA represents a new generation of neutrino experiments,” said Fermilab Director Nigel Lockyer. “We are proud to reach this important milestone on our way to learning more about these fundamental particles.”

One of NOvA's 28 detectors (Fermilab)
One of NOvA’s 28 far detector blocks (Fermilab)

After completion this summer NOvA’s near and far detectors will weigh 300 and 14,000 tons, respectively.

The goal of the NOvA experiment is to successfully capture and measure the masses of the different neutrino flavors and also determine if neutrinos are their own antiparticles (they could be the same, since they lack  specific charge.) By comparing the oscillations (i.e., flavor changes) of muon neutrino beams vs. muon antineutrino beams fired from Fermilab, scientists hope to determine their mass hierarchy — and ultimately discover why the Universe currently contains much more matter than antimatter.

Read more: Neutrino Detection Could Help Paint an Entirely New Picture of the Universe

Once the experiment is fully operational scientists expect to catch a precious few neutrinos every day — about 5,000 total over the course of its six-year run. Until then, they at least now have their first few on the books.

“Seeing neutrinos in the first modules of the detector in Minnesota is a major milestone. Now we can start doing physics.”
– Rick Tesarek, Fermilab physicist

Learn more about the development and construction of the NoVA experiment below:


(Video credit: Fermilab)

Find out more about the NOvA research goals here.

Source: Fermilab press release

The NOvA collaboration is made up of 208 scientists from 38 institutions in the United States, Brazil, the Czech Republic, Greece, India, Russia and the United Kingdom. The experiment receives funding from the U.S. Department of Energy, the National Science Foundation and other funding agencies.

Posted on by Nancy Atkinson

Space Station Detector Finds Extra Antimatter in Space, Maybe Dark Matter

From its vantage point about 400 km above Earth on the International Space Station, the Alpha Magnetic Spectrometer collects data from primordial cosmic rays from space. Credit: NASA

The first results from the largest and most complex scientific instrument on board the International Space Station has provided tantalizing hints of nature’s best-kept particle secrets, but a definitive signal for dark matter remains elusive. While the AMS has spotted millions of particles of antimatter – with an anomalous spike in positrons — the researchers can’t yet rule out other explanations, such as nearby pulsars.

“These observations show the existence of new physical phenomena,” said AMS principal investigator Samuel Ting,” and whether from a particle physics or astrophysical origin requires more data. Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”

The positron fraction measured by AMS. Credit: CERN.
The positron fraction measured by AMS. Credit: CERN.

The AMS was brought to the ISS in 2011 during the final flight of space shuttle Endeavour, the penultimate shuttle flight. The $2 billion experiment examines ten thousand cosmic-ray hits every minute, searching for clues into the fundamental nature of matter.

During the first 18 months of operation, the AMS collected of 25 billion events. It found an anomalous excess of positrons in the cosmic ray flux — 6.8 million are electrons or their antimatter counterpart, positrons.

The AMS found the ratio of positrons to electrons goes up at energies between 10 and 350 gigaelectronvolts, but Ting and his team said the rise is not sharp enough to conclusively attribute it to dark matter collisions. But they also found that the signal looks the same across all space, which would be expected if the signal was due to dark matter – the mysterious stuff that is thought to hold galaxies together and give the Universe its structure.

Additionally, the energies of these positrons suggest they might have been created when particles of dark matter collided and destroyed each other.

A screenshot from Ting's presentation at CERN on April 3, 2013. 'It took us 18 years to complete this result,' Ting said.
A screenshot from Ting’s presentation at CERN on April 3, 2013. ‘It took us 18 years to complete this result,’ Ting said.

The AMS results are consistent with the findings of previous telescopes, like the Fermi and PAMELA gamma-ray instruments, which also saw a similar rise, but Ting said the AMS results are more precise.

The results released today do not include the last 3 months of data, which have not yet been processed.

“As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector,” Ting said.

Cosmic rays are charged high-energy particles that permeate space. An excess of antimatter within the cosmic ray flux was first observed around two decades ago. The origin of the excess, however, remains unexplained. One possibility, predicted by a theory known as supersymmetry, is that positrons could be produced when two particles of dark matter collide and annihilate. Ting said that over the coming years, AMS will further refine the measurement’s precision, and clarify the behavior of the positron fraction at energies above 250 GeV.

Although having the AMS in space and away from Earth’s atmosphere – allowing the instruments to receive a constant barrage of high-energy particles — during the press briefing, Ting explained the difficulties of operating the AMS in space. “You can’t send a student to go out and fix it,” he quipped, but also added that the ISS’s solar arrays and the departure and arrival of the various spacecraft can have an effect on thermal fluctuations the sensitive equipment might detect. “You need to monitor and correct the data constantly or you are not getting accurate results,” he said.

Despite recording over 30 billion cosmic rays since AMS-2 was installed on the International Space Station in 2011, the Ting said the findings released today are based on only 10% of the readings the instrument will deliver over its lifetime.

Asked how much time he needs to explore the anomalous readings, Ting just said, “Slowly.” However, Ting will reportedly provide an update in July at the International Cosmic Ray Conference.

More info: CERN press release, the team’s paper: First Result from the Alpha Magnetic Spectrometer on the International Space Station: Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5–350 GeV

Posted on by Jason Major

Ping-Pong Particles: What the Higgs Does

Unless you’ve been hiding under a chondrite for the past week you’ve heard the news from CERN regarding the discovery of a new particle that exhibits “Higgs-like” qualities. Particle physics isn’t the easiest discipline to wrap one’s head around, and while we’ve recently shared some simplified explanations of what exactly a Higgs boson is, well…here’s another.

Here, BBC’s Jonathan Amos attempts to demonstrate what the Higgs field does, and what part the boson plays. Some Ping-Pong balls, a little sugar, and a cafeteria tray is all it takes to give an idea of how essential this long-sought after subatomic particle is to the Universe. (If only finding it had been that easy!)

Video: BBC News

Posted on by Nancy Atkinson

Higgs-like Particle Discovered at CERN

This is the signature of one of 100s of trillions of particle collisions detected at the Large Hadron Collider. The combined analysis lead to the discovery of the Higgs Boson. This article describes one team in dissension with the results. (Photo Credit: CERN)

Physicists working at the Large Hadron Collider (LHC) have announced the discovery of what they called a “Higgs-like boson” — a particle that resembles the long sought-after Higgs.

“We have reached a milestone in our understanding of nature,” CERN director general Rolf Heuer told scientists and media at a conference near Geneva on July 4, 2012. “The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle’s properties, and is likely to shed light on other mysteries of our universe.”


Two experiments, ATLAS and CMS, presented their preliminary results, and observed a new particle in the mass region around 125-126 GeV, the expected mass range for the Higgs Boson. The results are based on data collected in 2011 and 2012, with the 2012 data still under analysis. The official results will be published later this month and CERN said a more complete picture of today’s observations will emerge later this year after the LHC provides the experiments with more data.

“We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage,” said ATLAS experiment spokesperson Fabiola Gianotti, “but a little more time is needed to prepare these results for publication.”

The discovery of the Higgs is big, in that it is the last undiscovered piece of the Standard Model that describes the fundamental make-up of the universe.

Scientists believe that the Higgs boson, named for Scottish physicist Peter Higgs, who first theorized its existence in 1964, is responsible for particle mass, the amount of matter in a particle. According to the theory, a particle acquires mass through its interaction with the Higgs field, which is believed to pervade all of space and has been compared to molasses that sticks to any particle rolling through it.

And so, in theory, the Higgs would be responsible for how particles come together to form matter, and without it, the universe would have remained a formless miss-mash of particles shooting around at the speed of light.

“It’s hard not to get excited by these results,” said CERN Research Director Sergio Bertolucci. “We stated last year that in 2012 we would either find a new Higgs-like particle or exclude the existence of the Standard Model Higgs. With all the necessary caution, it looks to me that we are at a branching point: the observation of this new particle indicates the path for the future towards a more detailed understanding of what we’re seeing in the data.”

A CERN press release says that the next step will be to determine the precise nature of the particle and its significance for our understanding of the universe.

Are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4% of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96% of the universe that remains obscure. – CERN press release

“We have reached a milestone in our understanding of nature,” said CERN Director General Rolf Heuer. “The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle’s properties, and is likely to shed light on other mysteries of our universe.”

Positive identification of the new particle’s characteristics will take more time and more experiments. But the scientists feel that whatever form the Higgs particle takes, our knowledge of the fundamental structure of matter is about to take a major step forward.

Lead image caption: Event recorded with the CMS detector in 2012 at a proton-proton centre of mass energy of 8 TeV. The event shows characteristics expected from the decay of the SM Higgs boson to a pair of photons (dashed yellow lines and green towers). The event could also be due to known standard model background processes. Credit: CERN

Source: CERN

Posted on by Jason Major

Polar Telescope Casts New Light On Dark Energy And Neutrino Mass

The 10-meter South Pole Telescope in Antarctica at the Amundsen-Scott Station. (Daniel Luong-Van, National Science Foundation)

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Located at the southermost point on Earth, the 280-ton, 10-meter-wide South Pole Telescope has helped astronomers unravel the nature of dark energy and zero in on the actual mass of neutrinos — elusive subatomic particles that pervade the Universe and, until very recently, were thought to be entirely without measureable mass.

The NSF-funded South Pole Telescope (SPT) is specifically designed to study the secrets of dark energy, the force that purportedly drives the incessant (and apparently still accelerating) expansion of the Universe. Its millimeter-wave observation abilities allow scientists to study the Cosmic Microwave Background (CMB) which pervades the night sky with the 14-billion-year-old echo of the Big Bang.

Overlaid upon the imprint of the CMB are the silhouettes of distant galaxy clusters — some of the most massive structures to form within the Universe. By locating these clusters and mapping their movements with the SPT, researchers can see how dark energy — and neutrinos — interact with them.

“Neutrinos are amongst the most abundant particles in the universe,” said Bradford Benson, an experimental cosmologist at the University of Chicago’s Kavli Institute for Cosmological Physics. “About one trillion neutrinos pass through us each second, though you would hardly notice them because they rarely interact with ‘normal’ matter.”

If neutrinos were particularly massive, they would have an effect on the large-scale galaxy clusters observed with the SPT. If they had no mass, there would be no effect.

The SPT collaboration team’s results, however, fall somewhere in between.

Even though only 100 of the 500 clusters identified so far have been surveyed, the team has been able to place a reasonably reliable preliminary upper limit on the mass of neutrinos — again, particles that had once been assumed to have no mass.

Previous tests have also assigned a lower limit to the mass of neutrinos, thus narrowing the anticipated mass of the subatomic particles to between 0.05 – 0.28 eV (electron volts). Once the SPT survey is completed, the team expects to have an even more confident result of the particles’ masses.

“With the full SPT data set we will be able to place extremely tight constraints on dark energy and possibly determine the mass of the neutrinos,” said Benson.

“We should be very close to the level of accuracy needed to detect the neutrino masses,” he noted later in an email to Universe Today.

The South Pole Telescope's unique position allows it to watch the night sky for months on end. (NSF)

Such precise measurements would not have been possible without the South Pole Telescope, which has the ability due to its unique location to observe a dark sky for very long periods of time. Antarctica also offers SPT a stable atmosphere, as well as very low levels of water vapor that might otherwise absorb faint millimeter-wavelength signals.

“The South Pole Telescope has proven to be a crown jewel of astrophysical research carried out by NSF in the Antarctic,” said Vladimir Papitashvili, Antarctic Astrophysics and Geospace Sciences program director at NSF’s Office of Polar Programs. “It has produced about two dozen peer-reviewed science publications since the telescope received its ‘first light’ on Feb. 17, 2007. SPT is a very focused, well-managed and amazing project.”

The team’s findings were presented by Bradford Benson at the American Physical Society meeting in Atlanta on April 1.

Read more on the NSF press release here.

Posted on by Nancy Atkinson

Particle Physicists Put the Squeeze on the Higgs Boson; Look for Conclusive Results in 2012

Scientists gather as the ATLAS and CMS experiments present the status of their searches for the Standard Model Higgs boson. Credit: CERN

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With “freshly squeezed” plots from the latest data garnered by two particle physics experiments, teams of scientists from the Large Hadron Collider at CERN, the European Center for Nuclear Research, said Tuesday they had recorded “tantalizing hints” of the elusive subatomic particle known as the Higgs Boson, but cannot conclusively say it exists … yet. However, they predict that 2012 collider runs should bring enough data to make the determination.

“The very fact that we are able to show the results of very sophisticated analysis just one month after the last bit of data we used has been recorded is very reassuring,” Dr. Greg Landsberg, physics coordinator for the Compact Muon Solenoid (CMS) detector at the LHC told Universe Today. “It tells you how quick the turnaround time is. This is truly unprecedented in the history of particle physics, with such large and complex experiments producing so much data, and it’s very exciting.”

For now, the main conclusion of over 6,000 scientists on the combined teams from CMS and the ATLAS particle detectors is that they were able to constrain the mass range of the Standard Model Higgs boson — if it exists — to be in the range of 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS.

The Standard Model is the theory that explains the interactions of subatomic particles – which describes ordinary matter that the Universe is made of — and on the whole works very well. But it doesn’t explain why some particles have mass and others don’t, and it also doesn’t describe the 96% of the Universe that is invisible.

In 1964, physicist Peter Higgs and colleagues proposed the existence of a mysterious energy field that interacts with some subatomic particles more than others, resulting in varying values for particle mass. That field is known as the Higgs field, and the Higgs Boson is the smallest particle of the Higgs field. But the Higgs Boson hasn’t been discovered yet, and one of the main reasons the LHC was built was to try to find it.

To look for these tiny particles, the LHC smashes high-energy protons together, converting some energy to mass. This produces a spray of particles which are picked up by the detectors. However, the discovery of the Higgs relies on observing the particles these protons decay into rather than the Higgs itself. If they do exist, they are very short lived and can decay in many different ways. The problem is that many other processes can also produce the same results.

How can scientists tell the difference? A short answer is that if they can figure out all the other things that can produce a Higgs-like signal and the typical frequency at which they will occur, then if they see more of these signals than current theories suggest, that gives them a place to look for the Higgs.

The experiments have seen excesses in similar ranges. And as the CERN press release noted, “Taken individually, none of these excesses is any more statistically significant than rolling a die and coming up with two sixes in a row. What is interesting is that there are multiple independent measurements pointing to the region of 124 to 126 GeV.”

“This is very promising,” said Landsberg, who is also a professor at Brown University. “This shows that both experiments understand what is going on with their detectors very, very well. Both calibrations saw excesses at low masses. But unfortunately the nature of our process is statistical and statistics is known to play funny tricks once in a while. So we don’t really know — we don’t have enough evidence to know — if what we saw is a glimpse of the Higgs Boson or these are just statistical fluctuations of the Standand Model process which mimic the same type of signatures as would come if the Higgs Boson is produced.”

Landsberg said the only way to cope with statistics is to get more data, and the scientists need to increase the size of the data samples considerably in order to definitely answer the question on whether the Higgs Boson exists at the mass of 125 GeV or any mass range which hasn’t been excluded yet.

The good news is that loads of data are coming in 2012.

“We hope to quadruple the data sample collected this year,” Landsberg said. “And that should give us enough statistical confidence to essentially solve this puzzle and tell the world whether we saw the first glimpses of the Higgs Boson. As the team showed today, we will keep increasing until we reach a level of statistical significance which is considered to be sufficient for discovery in our field.”

Landsberg said that within this small range, there is not much room for the Higgs to hide. “This is very exciting, and it tells you that we are almost there. We have enough sensitivity and beautiful detectors; we need just a little bit more time and a little more data. I am very hopeful we should be able to say something definitive by sometime next year.”

So the suspense is building and 2012 could be the year of the Higgs.

More info: CERN press release, ArsTechnica

Posted on by Jason Major

Neutrinos Still Breaking Speed Limits

Particle Collider
Today, CERN announced that the LHCb experiment had revealed the existence of two new baryon subatomic particles. Credit: CERN/LHC/GridPP

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New test results are in from OPERA and it seems those darn neutrinos, they just can’t keep their speed down… to within the speed of light, that is!

A report released in September by scientists working on the OPERA project (Oscillation Project with Emulsion-tracking Apparatus) at Italy’s Gran Sasso research lab claimed that neutrinos emitted from CERN 500 miles away in Geneva arrived at their detectors 60 nanoseconds earlier than expected, thus traveling faster than light. This caused no small amount of contention in the scientific community and made news headlines worldwide – and rightfully so, as it basically slaps one of the main tenets of modern physics across the face.

Of course the scientists at OPERA were well aware of this, and didn’t make such a proclamation lightly; over two years of repeated research was undergone to make sure that the numbers were accurate… as well as could be determined, at least. And they were more than open to having their tests replicated and the results reviewed by their peers. In all regards their methods were scientific yet skepticism was widespread… even within OPERA’s own ranks.

One of the concerns that arose regarding the discovery was in regards to the length of the neutrino beam itself, emitted from CERN and received by special detector plates at Gran Sasso. Researchers couldn’t say for sure that any neutrinos detected were closer to the beginning of the beam versus the end, a disparity (on a neutrino-sized scale anyway) of 10.5 microseconds… that’s 10.5 millionths of a second! And so in October, OPERA requested that proton pulses be resent – this time lasting only 3 nanoseconds each.

The OPERA Neutrino Detector

The results were the same. The neutrinos arrived at Gran Sasso 60 nanoseconds earlier than anticipated: faster than light.

The test was repeated – by different teams, no less – and so far 20 such events have been recorded. Each time, the same.

Faster. Than light.

What does this mean? Do we start tearing pages out of physics textbooks? Should we draw up plans for those neutrino-powered warp engines? Does Einstein’s theory of relativity become a quaint memento of what we used to believe?

Hardly. Or, at least, not anytime soon.

OPERA’s latest tests have managed to allay one uncertainty regarding the results, but plenty more remain. One in particular is the use of GPS to align the clocks at the beginning and end of the neutrino beam. Since the same clock alignment system was used in all the experiments, it stands that there may be some as-of-yet unknown factor concerning the GPS – especially since it hasn’t been extensively used in the field of high-energy particle physics.

In addition, some scientists would like to see more results using other parts of the neutrino detector array.

Of course, like any good science, replication of results is a key factor for peer acceptance. And thus Fermilab in Batavia, Illinois will attempt to perform the same experiment with its MINOS (Main Injector Neutrino Oscillation Search) facility, using a precision matching OPERA’s.

MINOS hopes to have its independent results as early as next year.

No tearing up any textbooks just yet…

 

Read more in the Nature.com news article by Eugenie Samuel Reich. The new result was released on the arXiv preprint server on November 17. (The original September 2011 OPERA team paper can be found here.)

Posted on by Tammy Plotner

Large Hadron Collider Finishes 2011 Proton Run

A new loop will be added to CERN's Antiproton Decelerator in 2016 to increase antiproton production at low energies. Credit: CERN

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The world’s largest and highest-energy particle accelerator has been busy. At 5:15 p.m. on October 30, 2011, the Large Hadron Collider in Geneva, Switzerland reached the end of its current proton run. It came after 180 consecutive days of operation and four hundred trillion proton collisions. For the second year, the LHC team has gone beyond its operational objectives – sending more experimental data at a higher rate. But just what has it done?

When this year’s project started, its goal was to produce a surplus of data known to physicists as one inverse femtobarn. While that might seem like a science fiction term, it’s a science fact. An inverse femtobarn is a measurement of particle collision events per femtobarn – which is equal to about 70 million million collisions. The first inverse femtobarn came on June 17th, and just in time to prepare the stage for major physics conferences requiring the data be moved up to five inverse femtobarns. The incredible number of collisions was reached on October 18, 2011 and then surpassed as almost six inverse femtobarns were delivered to each of the two general-purpose experiments – ATLAS and CMS.

“At the end of this year’s proton running, the LHC is reaching cruising speed,” said CERN’s Director for Accelerators and Technology, Steve Myers. “To put things in context, the present data production rate is a factor of 4 million higher than in the first run in 2010 and a factor of 30 higher than at the beginning of 2011.”

But that’s not all the LHC delivered this year. This year’s proton run also shut out the accessible hiding space for the highly prized Higgs boson and supersymmetric particles. This certainly put the Standard Model of particle physics and our understanding of the primordial Universe to the test!

“It has been a remarkable and exciting year for the whole LHC scientific community, in particular for our students and post-docs from all over the world. We have made a huge number of measurements of the Standard Model and accessed unexplored territory in searches for new physics. In particular, we have constrained the Higgs particle to the light end of its possible mass range, if it exists at all,” said ATLAS Spokesperson Fabiola Gianotti. “This is where both theory and experimental data expected it would be, but it’s the hardest mass range to study.”

“Looking back at this fantastic year I have the impression of living in a sort of a dream,” said CMS Spokesperson Guido Tonelli. “We have produced tens of new measurements and constrained significantly the space available for models of new physics and the best is still to come. As we speak hundreds of young scientists are still analysing the huge amount of data accumulated so far; we’ll soon have new results and, maybe, something important to say on the Standard Model Higgs Boson.”

“We’ve got from the LHC the amount of data we dreamt of at the beginning of the year and our results are putting the Standard Model of particle physics through a very tough test ” said LHCb Spokesperson Pierluigi Campana. “So far, it has come through with flying colours, but thanks to the great performance of the LHC, we are reaching levels of sensitivity where we can see beyond the Standard Model. The researchers, especially the young ones, are experiencing great excitement, looking forward to new physics.”

Over the next few weeks, the LHC will be further refining the 2011 data set with an eye to improving our understanding of physics. And, while it’s possible we’ll learn more from current findings, look for a leap to a full 10 inverse femtobarns which may yet be possible in 2011 and projected for 2012. Right now the LHC is being prepared for four weeks of lead-ion running… an “attempt to demonstrate that large can also be agile by colliding protons with lead ions in two dedicated periods of machine development.” If this new strand of LHC operation happens, science will soon be using protons to check out the internal machinations of much heftier structures – like lead ions. This directly relates to quark-gluon plasma, the surmised primordial conglomeration of ordinary matter particles from which the Universe evolved.

“Smashing lead ions together allows us to produce and study tiny pieces of primordial soup,” said ALICE Spokesperson Paolo Giubellino, “but as any good cook will tell you, to understand a recipe fully, it’s vital to understand the ingredients, and in the case of quark-gluon plasma, this is what proton-lead ion collisions could bring.”

Original Story Source: CERN Press Release.

Posted on by Nancy Atkinson

Q&A with Brian Cox, part 1: Recent Hints of the Higgs

Brian Cox at CERN with Kevin Eldon and Simon Munnery. Photo by Gia Milinovich, courtesy Brian Cox

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At two separate conferences in July, particle physicists announced some provoking news about the Higgs boson, and while the Higgs has not yet been found, physicists are continuing to zero in on the elusive particle. Universe Today had the chance to talk with Professor Brian Cox about these latest findings, and he says that within six to twelve months, physicists should be able to make a definite statement about the existence of the Higgs particle. Cox is the Chair in Particle Physics at the University of Manchester, and works on the ATLAS experiment (A Toroidal LHC ApparatuS) at the Large Hadron Collider at CERN. But he’s also active in the popularization of science, specifically with his new television series and companion book, Wonders of the Universe, a follow up to the 2010 Peabody Award-winning series, Wonders of the Solar System.

Universe Today readers will have a chance to win a copy of the book, so stay tuned for more information on that. But today, enjoy the first of a three-part interview with Cox:


Universe Today: Can you tell us about your work with ATLAS and its potential for finding things like extra dimensions, the unification of forces or dark matter?

Brian Cox, during the filming of one of his television series. Image courtesy Brian Cox.

Brian Cox: The big question is the origin and mass of the universe. It is very, very important because it is not an end in itself. It is a fundamental part of Quantum Field Theory, which is our theory of three of the four forces of nature. So if you ask the question on the most basic level of how does the universe work, there are only two pillars of our understanding at the moment. There is Einstein’s Theory of General Relatively, which deals with gravity — the weakest force in the Universe that deals with the shape of space and time and all those things. But everything else – electromagnetism, the way the atomic nuclei works, the way molecules work, chemistry, all that – everything else is what’s called a Quantum Field Theory. Embedded in that is called the Standard Model of particle physics. And embedded in that is this mechanism for generating mass, and it’s just so fundamental. It’s not just kind of an interesting add-on, it’s right in the heart of the way the theory works.

So, understanding whether our current picture of the Universe is right — and if there is this thing called the Higgs mechanism or whether there is something else going on — is critical to our progress because it is built into that picture. There are hints in the data recently that maybe that mechanism is right. We have to be careful. It’s not a very scientific thing to say that we have hints. We have these thresholds for scientific discovery, and we have them for a reason, because you get these statistical flukes that appear in the data and when you get more data they go away again.

The statement from CERN now is that if they turn out to be more than just fluctuations, really, within six months we should be able to make some definite statement about the existence of the Higgs particle.

I think it is very important to emphasize that this is not just a lot of particle physicists looking for particles because that’s their job. It is the fundamental part of our understanding of three of the four forces of nature.

Brian Cox at Fermilab. Photo by Paul Olding.

UT : So these very interesting results from CERN and the Tevatron at Fermilab giving us hints about the Higgs, could you can talk little bit more about that and your take on the latest findings?

COX: The latest results were published in a set of conferences a few weeks ago and they are just under what is called the Three Sigma level. That is the way of assessing how significant the results are. The thing about all quantum theory and particle physics in general, is it is all statistical. If you do this a thousand times, then three times this should happen, and eight times that should happen. So it’s all statistics. As you know if you toss a coin, it can come up heads ten times, there is a probability for that to happen. It doesn’t mean the coin is weighted or there’s something wrong with it. That’s just how statistics is.

So there are intriguing hints that they have found something interesting. Both experiments at the Large Hadron Collider, the ATLAS and the Compact Muon Solenoid (CMS) recently reported “excess events” where there were more events than would be expected if the Higgs does not exist. It is about the right mass: we think the Higgs particle should be somewhere between about 120 and 150 gigaelectron volts [GeV—a unit of energy that is also a unit of mass, via E = mc2, where the speed of light, c, is set to a value of one] which is the expected mass range of the Higgs. These hints are around 140, so that’s good, it’s where it should be, and it is behaving in the way that it is predicted to by the theory. The theory also predicts how it should decay away, and what the probability should be, so all the data is that this is consistent with the so-called standard model Higgs.

But so far, these events are not consistently significant enough to make the call. It is important that the Tevatron has glimpsed it as well, but that has even a lower significance because that was low energy and not as many collisions there. So you’ve got to be scientific about things. There is a reason we have these barriers. These thresholds are to be cleared to claim discoveries. And we haven’t cleared it yet.

But it is fascinating. It’s the first time one of these rumors have been, you know, not just nonsense. It really is a genuine piece of exciting physics. But you have to be scientific about these things. It’s not that we know it is there and we’re just not going to announce it yet. It’s the statistics aren’t here yet to claim the discovery.

Brian Cox, while filming a BBC series in the Sahara. Image courtesy Brian Cox

UT : Well, my next question was going to be, what happens next? But maybe you can’t really answer that because all you can do is keep doing the research!

COX: The thing about the Higgs, it is so fundamentally embedded in quantum theory. You’ve got to explore it because it is one thing to see a hint of a new particle, but it’s another thing to understand how that particle behaves. There are lots of different ways the Higgs particles can behave and there are lots of different mechanisms.

There is a very popular theory called supersymmetry which also would explain dark matter, one of the great mysteries in astrophysics. There seems to be a lot of extra stuff in the Universe that is not behaving the way that particles of matter that we know of behave, and with five times more “stuff” as what makes up everything we can see in the Universe. We can’t see dark matter, but we see its gravitational influence. There are theories where we have a very strong candidate for that — a new kind of particle called a supersymmetry particles. There are five Higgs particles in them rather than one. So the next question is, if that is a Higgs-like particle that we’ve discovered, then what is it? How does it behave? How does it talk to the other particles?

And then there are a huge amount of questions. The Higgs theory as it is now doesn’t explain why the particles have the masses they do. It doesn’t explain why the top quark, which is the heaviest of the fundamental particles, is something like 180 times heavier than the proton. It’s a tiny point-like thing with no size but it’s 180 times the mass of a proton! That is heavier than some of the heaviest atomic nuclei!

Why? We don’t know.

I think it is correct to say there is a door that needs to be opened that has been closed in our understanding of the Universe for decades. It is so fundamental that we’ve got to open it before we can start answering these further questions, which are equally intriguing but we need this answered first.

UT: When we do get some of these questions answered, how is that going to change our outlook and the way that we do things, or perhaps the way YOU do things, anyway! Maybe not us regular folks…

COX: Well, I think it will – because this is part of THE fundamental theory of the forces of nature. So quantum theory in the past has given us an understanding, for example, of the way semiconductors work, and it underpins our understanding of modern technology, and the way chemistry works, the way that biological systems work – it’s all there. This is the theory that describes it all. I think having a radical shift and deepening in understanding of the basic laws of nature will change the way that physics proceeds in 21st century, without a doubt. It is that fundamental. So, who knows? At every paradigm shift in science, you never really could predict what it was going to do; but the history of science tells you that it did something quite remarkable.

There is a famous quote by Alexander Fleming, who discovered penicillin, who said that when he woke up on a certain September morning of 1928, he certainly didn’t expect to revolutionize modern medicine by discovering the world’s first antibiotic. He said that in hindsight, but he just discovered some mold, basically, but there it was.

But it was fundamental and that is the thing to emphasize.

Some of our theories, you look at them and wonder how we worked them! The answer is mathematically, the same way that Einstein came up with General Relativity, with mathematical predictions. It is remarkable we’ve been able to predict something so fundamental about the way that empty space behaves. We might turn out to be right.

Tomorrow: Part 2: The space exploration and hopes for the future

Find out more about Brian Cox at his website, Apollo’s Children