A joint Fermilab/SLAC publication

CHAMPs take a chomp from SUSY


A whimsically named type of particle, the CHAMP, is taking a bite out of possible theories of supersymmetry.

CHArged Massive stable Particles are a theoretically conjectured type of long-lived, heavy particles that could be created in particle colliders and which would survive long enough to make it out of the detector before decaying. Todd Adams from Florida State University explained how they leave a fairly unusual signal because they penetrate a detector a long way, are slow moving, and are heavily ionizing, therefore potentially leaving strong signals in detectors. However, there is also a risk that the particles could be confused for either energetic muons or a type of particle called an “R-hadron”.

So far, there has been no evidence of the existence of CHAMPs at the Fermilab’s Tevatron, but the fact that they haven’t shown up allows physicists to place limits on how supersymmetry must appear if it is present in nature. The DZero experiment has looked for CHAMPs that masquerade as muons in the detector and the CDF experiment has looked for particles that mimic R-hadrons.

One CDF search reveals that the mass of the “stop”, the supersymmetric partner of the top quark, must be more than 249 GeV, and also places limits on how strongly it could interact with other particles, ruling out predictions in some supersymmetry models. That paper was published in 2009 in Physical Review Letters and described yesterday by Adams at the American Physical Society meeting in Washington, DC. The DZero search was used as a key part of a theoretical paper “Supersymmetry Without Prejudice” by Carola Berger and colleagues about how the signals of supersymmetry can lead to unusual and unexpected signatures. Adams described the CHAMP searches as good ways of exploring some of the theoretical predictions of SUSY theories because they can cover areas of supersymmetry predictions that other searches can’t interrogate.

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