We report the most sensitive direct search for pair production
of fourth-generation bottom-like chiral quarks (b') each decaying
promptly to tW. We search for an excess of events with an electron or
muon, at least five jets (one indentified as due to a b or c quark) and
an imbalance of transverse momentum using data from p anti-p collisions
collected by the CDF II detector at Fermilab with an integrated luminosity
of 4.8 fb-1. We observe events consistent with background expectation
and calculate upper limits on the b' pair production cross section
(sigma_bb-bar < 30 fb for m_b' > 375 GeV/c2) and exclude m_b' <
372 GeV/c2 at 95% confidence level.
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Updated: Friday, 2011 April 08 15:42:41 CDT automatically from input from "Carol Picciolo"