April Fools'10: Supersymmetry Discovered at the LHC?!

The floor has hardly been swept after celebrations of the first LHC 7 TeV collisions, and it seems that very soon champagne corks will pop again. That could well be rivers of champagne. I've just been informed that a couple of events captured during the first day of high-energy running contain unmistakable signatures of a particle predicted by supersymmetric theories!!!

The first of these events, reproduced on the right, has been observed in the ATLAS detector. An analysis of the event uncovered that the track marked in red corresponds a charged particle with the mass of approximately 800 GeV!!! This is a new, previously unknown particle, that can only be produced in very high energy collisions such as the ones now available at the LHC.

Let me quote the anonymous ATLAS member who sent me this event display

This is absolutely amazing, it's the greatest day in the history of particle physics.
We thought that reaching discoveries would be a long and painful process, but Nature has been extremely kind to us.

Indeed.

The other striking event comes from the CMS detector. Ironically, it has already been shown at the public presentation on March 30. At that time, however, the particle marked in red has been mistaken for an ordinary muon due to a glitch in the detector electronics that lead to an incorrect measurement of the particle momentum. But a reanalysis of the event lead to a conclusion that this is an 800 GeV particle, definitely not a muon!!! Most likely this particle is of the same kind as the one seen by ATLAS, which means we have an independent confirmation of the discovery.

The most plausible theoretical interpretation is that ATLAS and CMS have observed a chargino: a supersymmetric partner of the standard model W and Higgs bosons. A very interesting conclusion that can be drawn from these two events is that the chargino is quasi stable: rather than decaying immediately, it lives long enough to traverse the entire detector. Such long-lived charginos are predicted by a version supersymmetric theories known as gauge mediation. In that scenario, the chargino decays to a W boson and a gravitino (the supersymmetric partner of the graviton) who is the lightest supersymmetric particle. The decay proceeds very slowly because the gravitino, much as the graviton, has a tiny coupling to ordinary matter.

A few points are still unclear from the theoretical point of view. For example, we would expect supersymmetric particles to be produced in pairs, whereas both experiments observed a single chargino. It is possible that the other chargino might have been lost in a crack of the detector, or charginos are produced together with a different supersymmetric particle species that decays immediately. This conundrum should be resolved as soon as a larger event sample is acquired.

The ATLAS and CMS collaborations are currently embroiled in a fierce battle over the priority of the discovery. This is quite a delicate matter, since the CMS was the first to register a chargino, while ATLAS was the first to correctly interpret it. I believe CERN is refraining from an official announcement of the discovery until the dispute is settled. But we should expect the confirmation anytime soon... stay tuned!

Update:
This post is an April Fools' joke. This was obvious to everyone, of course, because there is no supersymmetry in Nature :-) The displayed events feature ordinary muons; these and more are available at ATLAS and CMS public pages.