|Gauge bosons||photon, g, Z0, W+, W-|
This paper reports on a dedicated search for a fourth generation quark, called the b'. In this paper, we look for the b' quark by looking for its decay into either a b quark and a photon or a b quark and a g boson (gluon). Such decays are called "flavor changing neutral currents," because they involve an electrically neutral gauge boson (photon or gluon).
It is unusual for quarks to decay by emitting neutral gauge bosons. Most of the time, quarks decay into one of the electrically charged gauge bosons, W+ or W-, and another quark. Such decays are called "charged currents," because they involve a charged gauge boson. Several experiments have searched for fourth generation quarks by looking for their charged current decays, and not found any.
In recent years, it was pointed out by particle theorists that a fourth generation b' quark might decay by emitting neutral gauge bosons instead of charged gauge bosons. In that case, a fourth generation quark could exist that had been missed by previous experiments.
This experiment did not find any evidence for neutral current decays of b' quarks. The conclusion of this paper is that b' quarks with masses less than the mass of the Z0 boson are ruled out if they decay by neutral currents.
A copy of the paper, in preprint form, is available from hep-ex-9611021 .
For further information contact Dr. Herbert Greenlee, Fermilab, email: firstname.lastname@example.org
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