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

TL;DR

This paper presents a highly sensitive search for fourth-generation bottom-like quarks decaying to top and W bosons, setting new mass exclusion limits based on proton-antiproton collision data at 1.96 TeV.

Contribution

It provides the most sensitive direct search for pair-produced bottom-like quarks decaying to top and W, establishing new mass exclusion limits using data from the CDF II detector.

Findings

No excess events observed over background.

Excluded bottom-like quark masses below 372 GeV/c^2.

Set upper limits on production cross section (~30 fb).

Abstract

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 $p\bar{p}$ 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 $b'$ pair production cross section ($\sigma_{b\bar{b'}}\lesssim 30$ fb for $m_{b'}>$375 GeV/$c^2$) and exclude $m_{b'}<372$ \gevcc at 95% confidence level.