An improved determination of the width of the top quark

TL;DR

This paper provides an improved measurement of the top quark's total decay width and lifetime using data from the D0 experiment, along with updated limits on CKM matrix elements involving the top quark.

Contribution

The study introduces a novel method combining single top production cross section and $tar{t}$ decay measurements to determine the top quark width more precisely.

Findings

Top quark width $oxed{2.00^{+0.47}_{-0.43} ext{ GeV}}$ for $m_t=172.5$ GeV

Top quark lifetime $oxed{(3.29^{+0.90}_{-0.63}) imes 10^{-25} ext{s}}$

Updated limits on CKM matrix elements involving the top quark

Abstract

We present an improved determination of the total width of the top quark, $\Gamma_t$, using 5.4 fb$^{-1}$ of integrated luminosity collected by the D0 Collaboration at the Tevatron $p\bar{p}$ Collider. The total width $\Gamma_t$ is extracted from the partial decay width $\Gamma(t\to Wb)$ and the branching fraction $\mathcal{B}(t\to Wb)$. $\Gamma(t\to Wb)$ is obtained from the $t$-channel single top quark production cross section and $\mathcal{B}(t\to Wb)$ is measured in $t\bar{t}$ events. For a top mass of $172.5\;\rm GeV$, the resulting width is $\Gamma_t = 2.00^{+0.47}_{-0.43}$ GeV. This translates to a top-quark lifetime of $\tau_t = (3.29^{+0.90}_{-0.63})\times10^{-25}$ s. We also extract an improved direct limit on the CKM matrix element $0.81 < |V_{tb}| \leq 1$ at 95% C.L. and a limit of $|V_{tb'}| < 0.59$ for a high mass fourth generation bottom quark assuming unitarity of the fourth generation quark mixing matrix.