Search for a fourth generation charge -1/3 quark via flavor changing neutral current decay

We report on a search for pair production of a fourth generation charge -1/3 quark (b') in pbar p collisions at sqrt(s) = 1.8 TeV at the Fermilab Tevatron using an integrated luminosity of 93 pb^-1. Both quarks are assumed to decay via flavor changing neutral currents (FCNC). The search uses the signatures gamma + 3 jets + mu-tag and 2 gamma + 2 jets. We see no significant excess of events over the expected background. We place an upper limit on the production cross section times branching fraction that is well below theoretical expectations for a b' quark decaying exclusively via FCNC for b' quark masses up to m(Z) + m(b).

Note:

Eleven pages, two postscript figures, submitted to Physical Review Letters

D0
anti-p p: colliding beams
new particle: search for
charge: fractional
quark: pair production
family: 4
quark: decay
neutral current: flavor changing
final state: (3jet photon)
final state: (2jet 2photon)

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