We may soon know why the universe seems to have a preference for matter over antimatter.An international team of physicists working on the ALPHA experiment at CERN near Geneva, Switzerland, has successfully used microwaves to manipulate antihydrogen atoms. Their work could help answer fundamental questions about the universe. The accomplishment, by physicists working on the ALPHA experiment at CERN near Geneva, Switzerland, is a first step towards more detailed measurements that will reveal whether matter and antimatter are true mirror images.
“This comparison is motivated in part by a question that has baffled scientists for a long time,” says Simon Fraser University physics professor Mike Hayden, lead author of the research paper published in Nature March 7. “The known laws of physics tell us that matter and antimatter should naturally exist in equal amounts. The problem is that we seem to live in a universe that is almost entirely devoid of antimatter. A possible explanation is that there might be some subtle difference between matter and antimatter, which let matter win out over time as the universe evolved. If a difference between hydrogen and anti-hydrogen is discovered, it could provide a valuable clue for solving this mystery.”
The ALPHA team trapped an atom of antihydrogen –made up of a positron – the antimatter equivalent of an electron and an antiproton– using magnetic fields. By shining microwave radiation tuned to a specific frequency on the captive atom, the team was able to flip the anti-atom’s magnetic moment, liberating it from the trap and allowing it to be detected, enabling the first spectroscopic measurement of antihydrogen.
The current standard model of particle physics predicts that antimatter atoms should behave exactly the same as atoms of normal matter, and have identical properties, apart from their opposite charge, which can be verified by comparing the frequency of light emitted from excited atoms. Any difference in these spectroscopic measurements would suggest that antimatter is not an exact opposite of matter – and the assumptions the standard model is based on would be considerably weakened.
The present measurement, which was conducted by the ALPHA collaboration at CERN in Switzerland, involved irradiating magnetically-trapped anti-atoms with microwaves. Precise tuning of the microwave frequency and magnetic field enabled researchers to hit an internal resonance, kicking atoms out of the trap and revealing information about their properties.
“We have just witnessed the first-ever interactions between microwaves and trapped antimatter atoms,” says Hayden. The Daily Galaxy via Simon Fraser University. Eventually measurements may reveal clues that may help solve one of the deepest mysteries in particle physics.
Long-Sought Higgs Particle Cornered, Scientists Say
Clara Moskowitz, LiveScience Senior Writer
Date: 13 December 2011 Time: 08:52 AM ET
A typical candidate event at the Large Hadron Collider (LHC), including two high-energy photons whose energy (depicted by red towers) is measured in the CMS electromagnetic calorimeter. The yellow lines are the measured tracks of other particles produced in the collision. The pale blue volume shows the CMS crystal calorimeter barrel.
Physicists are closer than ever to hunting down the elusive Higgs boson particle, the missing piece of the governing theory of the universe’s tiniest building blocks.
Scientists at the world’s largest particle accelerator, the Large Hadron Collider at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, announced today (Dec. 13) that they’d narrowed down the list of possible hiding spots for the Higgs, (sometimes called the God particle) and even see some indications that they’re hot on its trail.
“I think we are getting very close,” said Vivek Sharma, a physicist at the University of California, San Diego, and the leader of the Higgs search at LHC’s CMS experiment. “We may be getting the first tantalizing hints, but it’s a whiff, it’s a smell, it’s not quite the whole thing.”
“It’s something really extraordinary and I think we can be all proud of this,” said CERN physicist Fabiola Gianotti, spokesperson for the LHC’s ATLAS experiment, during a public seminar announcing the results today.
Experts outside the LHC collaborations agreed.
“These are really tough experiments, and it’s just really impressive what they’re doing,” Harvard University theoretical physicist Lisa Randall told LiveScience.
Physicists at the CERN laboratory in Geneva, Switzerland view a presentation of thedata collected so far in the search for the Higgs boson particle at the Large Hadron Collider’s ATLAS experiment.
The Higgs boson is thought to be tied to a field (the Higgs field) that is responsible for giving all other particles their mass. Ironically, physicists don’t have a specific prediction for the mass of the Higgs boson itself, so they must search a wide range of possible masses for signs of the particle.
Based on data collected at LHC’s CMS and ATLAS experiments, researchers said they are now able to narrow down the Higgs’ mass to a small range, and exclude a wide swath of possibilities.
“With the data from this year we’ve ruled out a lot of masses, and now we’re just left with this tiny window, in this region that is probably the most interesting,” said Jonas Strandberg, a researcher at CERN working on the ATLAS experiment.
The researchers have now cornered the Higgs mass in the range between 115 and 130 gigaelectronvolts (GeV).For comparison, a proton weighs 1 GeV. Outside that range, the scientists are more than 95 percent confident that the Higgs cannot exist.
Within that range, the ATLAS findings show some indications of a possible signal from the Higgs boson around 125 GeV, though the data are not strong enough for scientists to make a claim with the level of confidence they require for a true discovery.
The CMS experiment also showed preliminary indications of a signal around that spot.
This plot shows the data collected so far by the Large Hadron Collider’s ATLAS experiment in the search for the Higgs boson particle.
“The excess is most compatible with a Standard Model Higgs in the vicinity of 124 GeV and below, but the statistical significance is not large enough to say anything conclusive,” CMS experiment spokesperson Guido Tonelli said in a statement. “As of today what we see is consistent either with a background fluctuation or with the presence of the boson. Refined analyses and additional data delivered in 2012 by this magnificent machine will definitely give an answer.”
Proceed with caution
Ultimately, scientists said they were excited by the LHC’s findings so far, but that it’s too soon to celebrate.
“Please be prudent,” said CERN director general Rolf-Dieter Heuer. “We have not found it yet, we have not excluded it yet. Stay tuned.”
The fact that the independent studies conducted by ATLAS and CMS appear to be pointing in the same direction is particularly promising, experts said.
“Based on the predicted size of the signal, the experiments may have their first glimpse of a positive signal,” University of Chicago physicist Jim Pilcher wrote in an email to LiveScience. “It is especially important to compare the results of two independent experiments to help reduce statistical fluctuations and experimental biases.”
But it shouldn’t be much longer before scientists can be sure if the Higgs exists, and if so, how much mass it has.
“We know we must be getting close,” Strandberg told LiveScience. “All we need is a little bit more data. I think the data we take in 2012 should be able to really give a definitive answer if the Higgs boson exists.”
The Large Hadron Collider is a 17-mile (27-kilometer) loop buried underneath France and Switzerland, run by CERN, based in Geneva.
Inside this loop, protons traveling near the speed of light collide head-on, and release huge amounts of energy in powerful explosions.
This energy then coalesces into new particles, some of which are exotic, hard-to-find species like the Higgs. The Higgs quickly decays into other particle products, which are then sensed by the detectors inside ATLAS and CMS. [6 Exotic Particles Explained]
The new results are based on data accumulated over 500 trillion proton-proton collisions inside the LHC.
The Higgs boson and its related Higgs field were predicted in 1964 by physicist Peter Higgs and his colleagues. Though the Higgs mechanism is the best explanation for why particles have mass, it can’t be trusted until its major prediction — the Higgs boson — is found. [Infographic: The Higgs Boson]
“It would be a major discovery, absolutely,” said Randall, who is the author of a recent book covering the Higgs and other particle mysteries called “Knocking on Heaven’s Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World” (Ecco, 2011). “We’ve known about the Higgs mechanism for years, but we don’t know if it’s right.”
The discovery of the Higgs would offer final credence to the idea and its originators.
“If it is found there are several people who are going to get a Nobel prize,” said Vivek Sharma, a physicist at the University of California, San Diego, and the leader of the Higgs search at LHC’s CMS experiment.
Possible Hints of Higgs Boson Remain in Latest Analyses, Physicists Say
ScienceDaily (Dec. 13, 2011) — Two experiments at the Large Hadron Collider have nearly eliminated the space in which the Higgs boson could dwell, scientists announced in a seminar held at CERN Dec. 13. However, the ATLAS and CMS experiments see modest excesses in their data that could soon uncover the famous missing piece of the physics puzzle.
Simulated production of a Higgs event in ATLAS. This track is an example of simulated data modeled for the ATLAS detector on the Large Hadron Collider at CERN. (Credit: Image courtesy
The experiments revealed the latest results as part of their regular report to the CERN Council, which provides oversight for the laboratory near Geneva, Switzerland.
Theorists have predicted that some subatomic particles gain mass by interacting with other particles called Higgs bosons. The Higgs boson is the only undiscovered part of the Standard Model of physics, which describes the basic building blocks of matter and their interactions.
The experiments’ main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery.
Higgs bosons, if they exist, are short-lived and can decay in many different ways. Just as a vending machine might return the same amount of change using different combinations of coins, the Higgs can decay into different combinations of particles. Discovery relies on observing statistically significant excesses of the particles into which they decay rather than observing the Higgs itself. Both ATLAS and CMS have analysed several decay channels, and the experiments see small excesses in the low mass region that has not yet been excluded.
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. It’s far too early to say whether ATLAS and CMS have discovered the Higgs boson, but these updated results are generating a lot of interest in the particle physics community.
Hundreds of scientists from U.S. universities and institutions are heavily involved in the search for the Higgs boson at LHC experiments, said CMS physicist Boaz Klima of the Department of Energy’s Fermi National Accelerator Laboratory near Chicago. “U.S. scientists are definitely in the thick of things in all aspects and at all levels,” he said.
More than 1,600 scientists, students, engineers and technicians from more than 90 U.S. universities and five U.S. national laboratories take part in the CMS and ATLAS experiments, the vast majority via an ultra-high broadband network that delivers LHC data to researchers at universities and national laboratories across the nation. The Department of Energy’s Office of Science and the National Science Foundation provide support for U.S. participation in these experiments. Fermi National Accelerator Laboratory is the host laboratory for the U.S. contingent on the CMS experiment, while Brookhaven National Laboratory hosts the U.S. ATLAS collaboration.
Over the coming months, both the CMS and ATLAS experiments will focus on refining their analyses in time for the winter particle physics conferences in March. The experiments will resume taking data in spring 2012.
“We’ve now analyzed all or most of the data taken in 2011 in some of the most important Higgs search analyses,” said ATLAS physicist Rik Yoshida of Argonne National Laboratory near Chicago. “I think everybody’s very surprised and pleased at the pace of progress.”
Higgs-hunting scientists on experiments at U.S. particle accelerator the Tevatron will also present results in March.
Discovering the type of Higgs boson predicted in the Standard Model would confirm a theory first put forward in the 1960s.
Even if the experiments find a particle where they expect to find the Higgs, it will take more analysis and more data to prove it is a Standard Model Higgs. If scientists found subtle departures from the Standard Model in the particle’s behavior, this would point to the presence of new physics, linked to theories that go beyond the Standard Model. Observing a non-Standard Model Higgs, currently beyond the reach of the LHC experiments with the data they’ve recorded so far, would immediately open the door to new physics.
Another possibility, discovering the absence of a Standard Model Higgs, would point to new physics at the LHC’s full design energy, set to be achieved after 2014. Whether ATLAS and CMS show over the coming months that the Standard Model Higgs boson exists or not, the LHC program is closing in on new discoveries.
Physicists at the Large Hadron Collider could be getting an early Christmas present: the Higgs boson. According to the latest rumours, scientists at the LHC are seeing a signal that could correspond to a Higgs particle with a mass of 125 GeV (a proton is slightly less than 1 GeV).
Public talks are scheduled to discuss the latest results from Atlas and CMS, two of the main LHC experiments, on 13 December. This follows one day after a closed-door Cern council meeting where officials will get a short preview of the findings, whatever they may be.
“Chances are high (but not strictly 100%) that the talks will either announce a (de facto or de iure) discovery or some far-reaching exclusion that will be really qualitative and unexpected,” wrote theoretical physicist Lubos Motl on his blog.
Motl also mentioned that an internal email sent to the Cern community suggests that results on the elusive Higgs — which is required under the Standard Model of particle physics to provide mass to different particles — will be inconclusive. This could mean that the finding is below the five-sigma threshold needed to definitively declare a discovery in physics.
But if the rumours are true, and the Higgs has been seen at 125 GeV, it could bolster the idea that there is physics beyond the Standard Model that describes the behaviour of subatomic particles. A 125 GeV Higgs is lighter than predicted under the simplest models and would likely require more complex theories, such as supersymmetry, which posits the existence of a heavier partner to all known particle
CERN: Light Speed May Have Been Exceeded By Subatomic Particle
FRANK JORDANS and SETH BORENSTEIN 09/22/11 09:19 PM ET
GENEVA — One of the very pillars of physics and Einstein’s theory of relativity – that nothing can go faster than the speed of light – was rocked Thursday by new findings from one of the world’s foremost laboratories.
European researchers said they clocked an oddball type of subatomic particle called a neutrino going faster than the 186,282 miles per second that has long been considered the cosmic speed limit.
The claim was met with skepticism, with one outside physicist calling it the equivalent of saying you have a flying carpet. In fact, the researchers themselves are not ready to proclaim a discovery and are asking other physicists to independently try to verify their findings.
“The feeling that most people have is this can’t be right, this can’t be real,” said James Gillies, a spokesman for the European Organization for Nuclear Research, or CERN, which provided the particle accelerator that sent neutrinos on their breakneck 454-mile trip underground from Geneva to Italy.
Going faster than light is something that is just not supposed to happen according to Einstein’s 1905 special theory of relativity – the one made famous by the equation E equals mc2. But no one is rushing out to rewrite the science books just yet.
It is “a revolutionary discovery if confirmed,” said Indiana University theoretical physicist Alan Kostelecky, who has worked on this concept for a quarter of a century.
Stephen Parke, who is head theoretician at the Fermilab near Chicago and was not part of the research, said: “It’s a shock. It’s going to cause us problems, no doubt about that – if it’s true.”
Even if these results are confirmed, they won’t change at all the way we live or the way the world works. After all, these particles have presumably been speed demons for billions of years. But the finding will fundamentally alter our understanding of how the universe operates, physicists said.
Einstein’s special relativity theory, which says that energy equals mass times the speed of light squared, underlies “pretty much everything in modern physics,” said John Ellis, a theoretical physicist at CERN who was not involved in the experiment. “It has worked perfectly up until now.”
The chief of the world’s leading physics lab at CERN in Geneva has prohibited scientists from drawing conclusions from a major experiment. The CLOUD (“Cosmics Leaving Outdoor Droplets”) experiment examines the role that energetic particles from deep space play in cloud formation. CLOUD uses CERN’s proton synchrotron to examine nucleation.
CERN Director General Rolf-Dieter Heuer toldWelt Online that the scientists should refrain from drawing conclusions from the latest experiment.
“I have asked the colleagues to present the results clearly, but not to interpret them,” reports veteran science editor Nigel Calder on his blog. Why?
Because, Heuer says, “That would go immediately into the highly political arena of the climate change debate. One has to make clear that cosmic radiation is only one of many parameters.”