Recently analyzed data from BaBar, a high energy physics experiment in the U.S., may suggest possible flaws in the Standard Model of particle physics, the reigning description of how the universe works on sub-atomic scales. The data from BaBar, a particle accelerator at the U.S. Department of Energy's (DOE's) SLAC National Accelerator Laboratory, built by ten countries including the U.K., show that a particular type of particle decay, happens more often than the Standard Model says it should. The U.K., through Queen Mary, University of London, was part of a panel to internally review the result that has been presented at a conference in China.
The data refers to a particle called the B-bar meson that decays into a D meson, an anti-neutrino and a tau lepton (^3B to D-star-tau-nu^2). This particular decay of a B meson should, theoretically, only happen in one in every 100 cases, but the new results from BaBar show it is happening too often. While the level of certainty of the difference, or excess, (3.4 sigma in statistical language) is not enough to claim a break from the Standard Model, the results are a potential sign of something amiss and are likely to impact existing theories.
"The excess over the Standard Model prediction is exciting", said BaBar spokesperson Michael Roney, Professor at the University of Victoria in Canada. "The results are significantly more sensitive than previously published studies of these decays", said Roney. "But before we can claim an actual discovery, other experiments have to replicate it and rule out the possibility this isn't just an unlikely statistical fluctuation".
"This result is very interesting, and if confirmed could be a sign of physics beyond the standard model", said Adrian Bevan, from Queen Mary, University of London and U.K. spokesperson for BaBar.
Fergus Wilson, one of the analyzers of data from Babar who is from STFC's Rutherford Appleton Laboratory, added: "Our current theory about the fundamental forces of the universe, which has been around for nearly 40 years, is beginning to show signs of failure. Just as exciting, our new measurement indicates that any replacement theory will need to be more exotic and complex than we could have hoped or imagined. Although we must not jump to conclusions based on just one measurement, this new result is one of the most compelling yet. It follows on from previous indications recently reported by us, all of which point in the same direction".
The BaBar experiment, which collected data from 1999 to 2008, was designed to explore various mysteries of particle physics, including why the universe contains matter, but no antimatter. Data from the collaboration which includes 75 institutions from Canada, France, Germany Italy, Norway, Russia, Spain, the U.K. and the U.S. helped confirm a matter-antimatter theory for which two researchers won the 2008 Nobel Prize in Physics. At its peak, some 90 British particle physicists and engineers from eleven institutions took part in the experiment.
Researchers continue to apply BaBar data to a variety of questions in particle physics. Adrian Bevan said: "This result will help guide teams of researchers looking for potentially related new physics effects at the Large Hadron Collider and at other particle physics labs around the world".
"If the excess decays shown are confirmed, it will be exciting to figure out what is causing it," said BaBar physics coordinator Abner Soffer, associate professor at Tel Aviv University. "Other theories involving new physics are waiting in the wings, but the BaBar results already rule out one important model called the Two Higgs Doublet Model. We hope our results will stimulate theoretical discussion about just what the data are telling us about new physics", added Soffer.
The researchers also hope their colleagues in the Belle collaboration, which studies the same types of particle collisions, see something similar. "If they do, the combined significance could be compelling enough to suggest how we can finally move beyond the Standard Model", said Professor Roney.
The results have been presented at the 10th annual Flavor Physics and Charge-Parity Violation Conference in Hefei, China, and submitted for publication in the journal Physical Review Letters. The paper is available on arXiv in preprint form [http://arxiv.org/abs/1206.2634].
STFC Rutherford Appleton Laboratory
+44 (0)1235 445627
Media Relations Manager
SLAC National Accelerator Laboratory
This work is supported by DOE and NSF (USA), STFC (U.K.), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and DFG (Germany), INFN (Italy), FOM (The Netherlands), NFR (Norway), MES (Russia), MICIIN (Spain), Israel and India. Individuals have received support from the Marie Curie EIF (European Union) and the A.P. Sloan Foundation (USA).
A team of around 600 physicists and engineers from ten countries built a huge particle detector at SLAC (the Stanford Linear Accelerator Center in California) to measure the decay of B mesons and their anti-particles, B-bar mesons.
The detector, which was named BaBar after these particles, weighed 1,200 tons, is 6 meters long and 6 meters in diameter. Some 75 institutions from Canada, France, Germany, Italy, Norway, Russia, Spain, The Netherlands, Israel, India, the United Kingdom and the United States all collaborated on the project. At the peak of its activity around 90 British particle physicists and engineers from eleven institutions took part in the experiment. The U.K. institutions involved were:
* University of Birmingham
* University of Bristol
* Brunel University
* University of Edinburgh
* University of Liverpool
* University of Manchester
* Imperial College London
* Queen Mary, University of London
* Royal Holloway, University of London
* University of Warwick
* STFC Rutherford Appleton Laboratory
SLAC (http://www.slac.stanford.edu) is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy Office of Science.
DOE's Office of Science (http://science.energy.gov) is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.
Queen Mary, University of London
Queen Mary, University of London is one of the U.K.'s leading research-focused higher education institutions with some 16,900 undergraduate and postgraduate students.
Amongst the largest of the colleges of the University of London, Queen Mary has accepted an invitation to join the Russell Group, which represents the 24 leading universities in the U.K. We will officially join the Group in August 2012.
Queen Mary's 3,800 staff deliver world class degree programs and research across 21 academic departments and institutes, within three sectors: Science and Engineering; Humanities, Social Sciences and Laws; and the School of Medicine and Dentistry.
Queen Mary is ranked 11th in the U.K. according to the Guardian analysis of the 2008 Research Assessment Exercise, and has been described as 'the biggest star among the research-intensive institutions' by the Times Higher Education.
The College has a strong international reputation, with around 20 percent of students coming from over 100 countries. Queen Mary has an annual turnover of #300 million, research income worth #70 million, and generates employment and output worth #600 million to the U.K. economy each year.
The College is unique amongst London's universities in being able to offer a completely integrated residential campus, with a 2,000-bed award-winning Student Village on its Mile End campus.
The Science and Technology Facilities Council is keeping the U.K. at the forefront of international science and tackling some of the most significant challenges facing society such as meeting our future energy needs, monitoring and understanding climate change, and global security.
The Council has a broad science portfolio and works with the academic and industrial communities to share its expertise in materials science, space and ground-based astronomy technologies, laser science, microelectronics, wafer scale manufacturing, particle and nuclear physics, alternative energy production, radio communications and radar.
STFC operates or hosts world class experimental facilities including:
* in the U.K.; ISIS pulsed neutron source, the Central Laser Facility, and LOFAR. STFC is also the majority shareholder in Diamond Light Source Ltd.
* overseas; telescopes on La Palma and Hawaii
It enables U.K. researchers to access leading international science facilities by funding membership of international bodies including European Laboratory for Particle Physics (CERN), the Institut Laue Langevin (ILL), European Synchrotron Radiation Facility (ESRF) and the European Southern Observatory (ESO). STFC is one of seven publicly-funded research councils. It is an independent, non-departmental public body of the Department for Business, Innovation and Skills (BIS).
Black Holes as Particle Detectors
Previously undiscovered particles could be detected as they accumulate around black holes say Scientists at the Vienna University of Technology.
Artist's impression of a black hole, surrounded by axions.
Artist's impression of a black hole, surrounded by axions.
Gabriela Mocanu and Daniel Grumiller
Gabriela Mocanu and Daniel Grumiller
Finding new particles usually requires high energies - that is why huge accelerators have been built, which can accelerate particles to almost the speed of light. But there are other creative ways of finding new particles: At the Vienna University of Technology, scientists presented a method to prove the existence of hypothetical "axions". These axions could accumulate around a black hole and extract energy from it. This process could emit gravity waves, which could then be measured.
Axions are hypothetical particles with a very low mass. According to Einstein, mass is directly related to energy, and therefore very little energy is required to produce axions. "The existence of axions is not proven, but it is considered to be quite likely", says Daniel Grumiller. Together with Gabriela Mocanu he calculated at the Vienna University of Technology (Institute for Theoretical Physics), how axions could be detected.
Astronomically Large Particles
In quantum physics, every particle is described as a wave. The wavelength corresponds to the particle's energy. Heavy particles have small wavelengths, but the low-energy axions can have wavelengths of many kilometers. The results of Grumiller and Mocanu, based on works by Asmina Arvanitaki and Sergei Dubovsky (USA/Russia), show that axions can circle a black hole, similar to electrons circling the nucleus of an atom. Instead of the electromagnetic force, which ties the electrons and the nucleus together, it is the gravitational force which acts between the axions and the black hole.
However, there is a very important difference between electrons in an atom and axions around a black hole: Electrons are fermions - which means that two of them can never be in the same state. Axions on the other hand are bosons, many of them can occupy the same quantum state at the same time. They can create a "boson-cloud" surrounding the black hole. This cloud continuously sucks energy from the black hole and the number of axions in the cloud increases.
Such a cloud is not necessarily stable. "Just like a loose pile of sand, which can suddenly slide, triggered by one single additional grain of sand, this boson cloud can suddenly collapse", says Daniel Grumiller. The exciting thing about such a collapse is that this "bose-nova" could be measured. This event would make space and time vibrate and emit gravity waves. Detectors for gravity waves have already been developed, in 2016 they are expected to reach an accuracy at which gravity waves should be unambiguously detected. The new calculations in Vienna show that these gravity waves can not only provide us with new insights about astronomy, they can also tell us more about new kinds of particles.
Picture Download: http://www.tuwien.ac.at/dle/pr/aktuelles/downloads/2012/axion/
Original publication: http://prd.aps.org/abstract/PRD/v85/i10/e105022
free arxiv-version: http://arxiv.org/abs/arXiv:1203.4681
Additional information, written by Gabriela Mocanu: http://www.tuwien.ac.at/fileadmin/t/tuwien/docs/pa/black_holes.pdf
Dr. Daniel Grumiller
Institute for Theoretical Physics
Vienna University of Technology
Wiedner Hauptstrasse 8, 1040 Vienna
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