Tevatron claims possible glimpse of particles beyond the standard model - April 06, 2011
Just as the Tevatron, the proton-antiproton collider at Fermilab in Batavia, Illinois, enters its final months of operations, possible signals of new physics are emerging. First came a report from the Collider Detector at Fermilab (CDF) experiment of a puzzling asymmetry in the way top quarks decay into lighter particles. Now the same experiment is reporting on the possible observation of particles beyond the standard model in collisions that produce a W boson – a particle of the weak nuclear force. Spokesmen for the experiment say the signal may be due to random fluctuations, but that it’s nonetheless causing some excitement. “Either what we thought we knew about this process is wrong or there’s a totally new effect,” says Giovanni Punzi, CDF co-spokesman.
CDF looked at events caused by the collisions of protons and antiprotons forming a W together with two jets of particles, carrying away energy. At a collision energy of around 144 GeV they saw an excess of electrons and muons – around 253 more than expected against a background of around 10,000, Punzi says. The excess could be caused by the creation of a new particle that decays into an extra W (that in turn decays into electrons or muons) and another lighter particle that produces jets. The effect has a magnitude of 3.2 standard deviations, enough to be considered intriguing, but not enough to claim a discovery.
Co-spokesman Rob Roser says the effect is unlikely to be due to the appearance of the Higgs boson that endows all others with mass because, at this energy, the Higgs is expected to decay into bottom quarks, which were not seen. “It doesn’t mean that it’s not some funky object that is Higgs-like,” he says. The next step will be to use extra data that CDF already has in hand and that the Tevatron continues to collect to confirm or reject the signal. Roser says he’s aware that, because of the Tevatron program is going to be shutdown this year, there will be some skeptics outside the 700-strong collaboration but that those inside have given the analysis a careful check before releasing it. “You always run the risk that people think you’re grandstanding when funding is at risk but we’re not. We’re trying to put this out in a responsible way. It’s hard to convince 700 people.”
This is certainly exciting. Of course this could just be an anomaly and that is what a lot of people have been saying; but it could also point to something far more exciting such as a new fundamental force that we've overlooked, which would revolutionise physics.
