By Devin Powell
After the two most powerful particle colliders in the world went toe-to-toe July 22 at the Europhysics Conference on High-Energy Physics in Grenoble, France, the result was a technical knockout.
New data from CERN’s Large Hadron Collider near Geneva delivered a serious blow to hints of unusual new physics coming out of the Tevatron at the Fermi National Accelerator Laboratory in Batavia, Ill. With 70 trillion collisions under its belt, the LHC has so far been a stalwart defender of the standard model, the reigning theory of particle physics.
“We’re learning that the standard model is very hard to kill,” says Pierluigi Campana, spokesperson for the LHCb detector team.
Researchers at the Tevatron’s collider detector at Fermilab, or CDF, had reported the first signs of a rare decay in a paper posted online July 12 at arXiv.org. Particles called Bs mesons seemed to be disintegrating into a muon (a cousin of the electron) and an antimuon more frequently than expected.
The standard model predicts that three out of every billion Bs mesons will meet this fate. CDF measurements suggested a higher rate of about 18 per billion, a light jab at the standard model and a tantalizing though inconclusive hint of other physics at work.
But at the recent meeting physicists from two LHC detectors — the compact muon solenoid, or CMS, and the LHCb — presented Bs meson decay sightings consistent with established particle theory.
“It doesn’t look like there are hints beyond the standard model,” says Dmitri Denisov, cospokesperson for CDF’s sister detector at Fermilab, DZero.
Tevatron fans can look forward to a rematch, however. CDF and DZero have both found signs that the top quark (the heaviest fundamental particle) and its antimatter particle, the antitop quark, prefer to move in opposite directions. An initial search at the LHC found no evidence of this puzzling behavior. Such behavior would be at odds with the standard model.
But with the LHC dataset expected to at least double in size this year and the Tevatron collecting data until its shutdown in September, everyone is looking forward to a winter bout between these friendly rivals.
