Published on June 19th, 2012 | by James Ayre
Cracks Appearing In The Standard Model Of Particle Physics
Newly analyzed data from the ‘BaBar experiment’ suggests that there might be flaws in the Standard Model of particle physics, which is the accepted theory of how the universe works on subatomic scales.
The BaBar experiment is a high-energy physics experiment based at the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory. The new data shows that a specific type of particle decay called “B to D-star-tau-nu” is much more common than the Standard Model says it should be.
During this type of decay, a particle called the B-bar meson decays into a D meson, an antineutrino, and a tau lepton. “While the level of certainty of the 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, including those attempting to deduce the properties of Higgs bosons.”
“The excess over the Standard Model prediction is exciting,” said BaBar spokesperson Michael Roney, professor at the University of Victoria in Canada. These results are much more sensitive than previously published studies analyzing 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.”
The BaBar experiment collected particle collision data from 1999 until 2008, and was designed to explore various unexplained aspects of particle physics. These included the question of why the universe contains matter but no antimatter. Data from the experiment helped confirm a theory on matter-antimatter interactions.
The data from BaBar is still being used by researchers to explore a variety of questions in particle physics. The data has actually more questions itself, particularly in regards to the Higgs Boson. The Higgs Boson is the theorized particle thought to give fundamental particles their mass. “Higgs bosons are predicted to interact more strongly with heavier particles — such as the B mesons, D mesons and tau leptons in the BaBar study — than with lighter ones, but the Higgs posited by the Standard Model can’t be involved in this decay.”
“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 are also hoping that their colleagues in the ‘Belles collaboration’, which researches the same kinds of particle collisions, might find something similar.
“If they do, the combined significance could be compelling enough to suggest how we can finally move beyond the Standard Model.” Roney said.
The research has just been submitted for publication in the journal Physical Review Letters.
Source: DOE/SLAC National Accelerator Laboratory
Image Credits: Greg Stewart, SLAC National Accelerator Laboratory, DOE/Brookhaven National Laboratory