Split Supersymmetry - Long Lived Gluinos

Long Lived Gluinos

The striking feature of split supersymmetry is that the gluino becomes a quasi-stable particle with a lifetime that could be up to 100 seconds long. A gluino that lived longer than this would disrupt Big Bang nucleosynthesis or would have been observed as an additional source of cosmic gamma rays. The gluino is long lived because it can only decay into a squark and a quark and because the squarks are so heavy and these decays are highly suppressed. Thus the decay rate of the gluino can roughly be estimated, in natural units, as where is the gluino rest mass and the squark rest mass. For gluino mass of the order of 1 TeV, the cosmological bound mentioned above sets an upper bound of about GeV on squarks masses.

The potentially long lifetime of the gluino leads to different collider signatures at the Tevatron and the Large Hadron Collider. There are three ways to see these particles:

• Measuring the ratio of momentum to energy or velocity in tracking chambers ( dE/dx in the inner tracking chamber or p/v in the outer muon tracking chamber)
• Looking for excess singlet jet events that arise from initial or final state radiation.
• Looking for gluinos that have come to rest inside the detector and later decay. Such an event may occur if the gluino hadronize to form an exotic hadron which strongly interacts with a nucleon in the detector to create an exotic charged hadron. The latter will decelerate by electromagnetic interaction inside the detector and will eventually stop.