Search for heavy bottom-like quarks decaying to an electron or muon and jets in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV

We report the most sensitive direct search for pair production of fourth-generation bottom-like chiral quarks ($b^{\mathrm{\prime }}$) 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 $p\bar{p}$ 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 $b^{\mathrm{\prime }}$ pair production cross section ($\sigma_{b\bar{b’}}\lesssim 30$fbfor$m_{b’}>$375GeV\mathrm{/}$c^2$)andexclude$m_{b’}<372$ \gevcc at 95% confidence level.