Neutrinos Obey The Speed Limit, After All

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Neutrinos have been cleared of allegations of speeding, according to an announcement issued today by CERN and the ICARUS experiment at Italy’s Gran Sasso National Laboratory. Turns out they travel exactly as fast as they should, and not a nanosecond more.

The initial announcement in September 2011 from the OPERA experiment noted a discrepancy in the measured speed of neutrinos traveling in a beam sent to the detectors at Gran Sasso from CERN in Geneva. If their measurements were correct, it would have meant that the neutrinos had arrived 60 nanoseconds faster than the speed of light allows. This, understandably, set the world of physics a bit on edge as it would effectually crumble the foundations of the Standard Model of physics.

As other facilities set out to duplicate the results, further investigations by the OPERA team indicated that the speed anomaly may have been the result of bad fiberoptic wiring between the detectors and the GPS computers, although this was never officially confirmed to be the exact cause.

Now, a a statement from CERN reports the results of the ICARUS experiment — Imaging Cosmic and Rare Underground Signals — which is stationed at the same facilities as OPERA. The ICARUS data, in measuring neutrinos from last year’s beams, show no speed anomaly — further evidence that OPERA’s measurement was very likely a result of error.

The full release states:

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The ICARUS experiment at the Italian Gran Sasso laboratory has today reported a new measurement of the time of flight of neutrinos from CERN to Gran Sasso. The ICARUS measurement, using last year’s short pulsed beam from CERN, indicates that the neutrinos do not exceed the speed of light on their journey between the two laboratories. This is at odds with the initial measurement reported by OPERA last September.

What neutrinos look like to ICARUS. (LNGS)

“The evidence is beginning to point towards the OPERA result being an artefact of the measurement,” said CERN Research Director Sergio Bertolucci, “but it’s important to be rigorous, and the Gran Sasso experiments, BOREXINO, ICARUS, LVD and OPERA will be making new measurements with pulsed beams from CERN in May to give us the final verdict. In addition, cross-checks are underway at Gran Sasso to compare the timings of cosmic ray particles between the two experiments, OPERA and LVD. Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements. This is how science works.” 

The ICARUS experiment has independent timing from OPERA and measured seven neutrinos in the beam from CERN last year. These all arrived in a time consistent with the speed of light.

“The ICARUS experiment has provided an important cross check of the anomalous result reports from OPERA last year,” said Carlo Rubbia, Nobel Prize winner and spokesperson of the ICARUS experiment. “ICARUS measures the neutrino’s velocity to be no faster than the speed of light. These are difficult and sensitive measurements to make and they underline the importance of the scientific process. The ICARUS Liquid Argon Time Projection Chamber is a novel detector which allows an accurate reconstruction of the neutrino interactions comparable with the old bubble chambers with fully electronics acquisition systems. The fast associated scintillation pulse provides the precise  timing of each event, and has been exploited for the neutrino time-of-flight measurement. This technique is now recognized world wide as the most appropriate for future large volume neutrino detectors”.

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An important note is that, although further research points more and more to neutrinos behaving as expected, the OPERA team had proceeded in a scientific manner right up to and including the announcement of their findings.

“Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements,” the ICARUS team reported. “This is how science works.”

See more news from CERN here.

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

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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

Cosmic Particle Accelerators – Let’s Dance!

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Are you ready to dance with a new discovery? ESA’s Cluster satellites are playing the tune of cosmic particle acceleration – and it’s more efficient than speculated. Now we’re taking a look at the beginnings of universal motion. By embracing a wide variety of astronomical targetry, the images are revealing shock waves where supersonic flows of plasma encounter everything from a slow flow to an irresistible force.

What sets things in motion? When it comes to particle accelerators, something needs to set it off. Here on Earth, the Large Hadron Collider (LHC) located at Cern uses a bank of smaller machines for giving rise to the charged particles before introducing them into the mainstream. In space, cosmic rays act as this “mainstream”, but they aren’t very efficient at setting the particles going initially. Now the ESA Cluster mission has revealed what could be ” natural particle accelerators of space”.

While cruising through a magnetic shock wave, the four Cluster satellites found themselves perfectly lined up with the magnetic field. This perfect chance alignment was a revelation – allowing the mission to sample the event with incredible accuracy on a very short timescale – one of 250 milliseconds or less. What surfaced from the investigation was the realization that the electrons heated rapidly, a state which contributes to acceleration on a greater scale. While this type of action had been speculated before, it hadn’t been observed or proved. No one really knew about the process or the size of the shock layers. With this new data, Steven J. Schwartz of the Imperial College London, and his colleagues were able to estimate the thickness of the shock layer – a significant advancement in understanding, because a thinner layer means faster acceleration.

“With these observations, we found that the shock layer is about as thin as it can possibly be,” says Professor Schwartz.

So just how skinny is this dance partner? Scientists had originally estimated the shock layers above Earth to be no more than 100 km, but the satellite information showed them to be about 17 km… a very fine detail!

Artist's impression of the four Cluster spacecraft flying through the thin layer of Earth's bow shock. The crossing, which took place on 9 January 2005, showed that the shock's width was only about 17 kilometres across.

This type of knowledge is significant simply because shocks exists universally – originating virtually everywhere a flow encounters an obstacle or another flow. For example, here in the Solar System the Sun generates a speedy, electrically charged stellar wind. When it runs headlong into a magnetic field – such as generated by Earth – it creates a shock wave located in front of the planet. Through the Cluster mission studies, we can apply what we learn here at home and extrapolate it on a grander scale – such as those created by supernovae events, black holes and galaxies. It might even reveal the origin of cosmic rays!

“This new result reveals the size of the proverbial ‘black box’, constraining the possible mechanisms within it involved in accelerating particles,” says Matt Taylor, ESA Cluster project scientist. “Yet again, Cluster has provided us with a clear insight into a physical process that occurs throughout the Universe.”

Come on, baby. Let’s dance…

Original Story Source: ESA News Release.

Unifying The Quantum Principle – Flowing Along In Four Dimensions

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In 1988, John Cardy asked if there was a c-theorem in four dimensions. At the time, he reasonably expected his work on theories of quantum particles and fields to be professionally put to the test… But it never happened. Now – a quarter of a century later – it seems he was right.

“It is shown that, for d even, the one-point function of the trace of the stress tensor on the sphere, Sd, when suitably regularized, defines a c-function, which, at least to one loop order, is decreasing along RG trajectories and is stationary at RG fixed points, where it is proportional to the usual conformal anomaly.” said Cardy. “It is shown that the existence of such a c-function, if it satisfies these properties to all orders, is consistent with the expected behavior of QCD in four dimensions.”

His speculation is the a-theorem… a multitude of avenues in which quantum fields can be energetically excited (a) is always greater at high energies than at low energies. If this theory is correct, then it likely will explain physics beyond the current model and shed light on any possible unknown particles yet to be revealed by the Large Hadron Collider (LHC) at CERN, Europe’s particle physics lab near Geneva, Switzerland.

“I’m pleased if the proof turns out to be correct,” says Cardy, a theoretical physicist at the University of Oxford, UK. “I’m quite amazed the conjecture I made in 1988 stood up.”

According to theorists Zohar Komargodski and Adam Schwimmer of the Weizmann Institute of Science in Rehovot, Israel, the proof of Cardy’s theories was presented July 2011, and is slowly gaining notoriety among the scientific community as other theoretical physicists take note of his work.

“I think it’s quite likely to be right,” says Nathan Seiberg, a theoretical physicist at the Institute of Advanced Study in Princeton, New Jersey.

The field of quantum theory always stands on shaky ground… it seems that no one can be 100% accurate on their guesses of how particles should behave. According to the Nature news release, one example is quantum chromodynamics — the theory of the strong nuclear force that describes the interactions between quarks and gluons. That lack leaves physicists struggling to relate physics at the high-energy, short-distance scale of quarks to the physics at longer-distance, lower-energy scales, such as that of protons and neutrons.

“Although lots of work has gone into relating short- and long-distance scales for particular quantum field theories, there are relatively few general principles that do this for all theories that can exist,” says Robert Myers, a theoretical physicist at the Perimeter Institute in Waterloo, Canada.

However, Cardy’s a-theorem just might be the answer – in four dimensions – the three dimensions of space and the dimension of time. However, in 2008, two physicists found a counter-example of a quantum field theory that didn’t obey the rule. But don’t stop there. Two years later Seiberg and his colleagues re-evaluated the counter-example and discovered errors. These findings led to more studies of Cardy’s work and allowed Schwimmer and Komargodski to state their conjecture. Again, it’s not perfect and some areas need further clarification. But Myers thinks that the proof is correct. “If this is a complete proof then this becomes a very powerful principle,” he says. “If it isn’t, it’s still a general idea that holds most of the time.”

According to Nature, Ken Intriligator, a theoretical physicist at the University of California, San Diego, agrees, adding that whereas mathematicians require proofs to be watertight, physicists tend to be satisfied by proofs that seem mostly right, and intrigued by any avenues to be pursued in more depth. Writing on his blog on November 9, Matt Strassler, a theoretical physicist at Rutgers University in New Brunswick, New Jersey, described the proof as “striking” because the whole argument follows once one elegant technical idea has been established.

With Cardy’s theory more thoroughly tested, chances are it will be applied more universally in the areas of quantum field theories. This may unify physics, including the area of supersymmetry and aid the findings with the LHC. The a-theorem “will be a guiding tool for theorists trying to understand the physics”, predicts Myers.

Pehaps Cardy’s work will even expand into condensed matter physics, an area where quantum field theories are used to elucidate on new states of materials. The only problem is the a-theorem has only had proof in two and four dimensions – where a few areas of condensed matter physics embrace layers containing just three dimensions – two in space and one in time. However, Myers states that they’ll continue to work on a version of the theorem in odd numbers of dimensions. “I’m just hoping it won’t take another 20 years,” he says.

Original Story Source: Nature News Release. For Further Reading: On Renormalization Group Flows in Four Dimensions.

Large Hadron Collider Finishes 2011 Proton Run

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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.

LHC Officially Becomes Most Powerful Accelerator

Well, they’ve done it: at 2028 GMT, 29 November 2009 the Large Hadron Collider officially became the most powerful particle accelerator ever built by humans. One of the proton beams in the LHC was powered up to 1.05 teraelectron volts (TeV) at that time, and three hours later both of the beams were powered to 1.18 TeV. This breaks the previous record held by the Fermilab accelerator in Chicago, which has held the record of .98 TeV since 2001.

Despite the initial problems that the largest scientific instrument ever built had this past year, things seem to be progressing smoothly. Last week, the proton-proton beams were collided for the first time. This latest record accelerated the protons to 0.9997 times the speed of light.

No new collisions were seen at this latest milestone, as it is just part of the process of powering up the beams to the projected 7 TeV needed for the first experiments of next year. Each beam will be powered up to 3.5 TeV to smash protons in order to re-create the conditions that existed near the time of the Big Bang, and help physicists understand the fundamental nature of matter. The 7 TeV goal should be reached by the end of December, and the first collisions at the amazing energies of the LHC will occur in early 2010.

Director-General of CERN Rolf Heuer said the recent progress has been fantastic. “However, we are continuing to take it step by step, and there is still a lot to do before we start physics in 2010,” he said. “I’m keeping my champagne on ice until then.”

The LHC, is a 27 km (17 mile) long circular tunnel composed of super-cooled, superconducting magnets that runs underneath the town of Geneva, Switzerland. By colliding protons together at such energetic speeds, some fundamental questions about what matter is made of, and what the conditions were like around the earliest times of our Universe may be answered.

You can follow further advancements of the LHC at CERN’s site, on Twitter or right here at Universe Today!

Source: CERN