1202.4694 (H. Lacker et al.)

Model-independent extraction of $|V_{tq}|$ matrix elements from
top-quark measurements at hadron colliders    [PDF]

H. Lacker, A. Menzel, F. Spettel, D. Hirschbühl, J. Lück, F. Maltoni, W. Wagner, M. Zaro

Current methods to extract the quark-mixing matrix element $|V_{tb}|$ from
single-top production measurements assume that $|V_{tb}|\gg |V_{td}|,
|V_{ts}|$: top quarks decay into $b$ quarks with 100% branching fraction,
s-channel single-top production is always accompanied by a $b$ quark and
initial-state contributions from $d$ and $s$ quarks in the $t$-channel
production of single top quarks are neglected. Triggered by a recent
measurement of the ratio
$R=\frac{|V_{tb}|^{2}}{|V_{td}|^{2}+|V_{ts}|^{2}+|V_{tb}|^{2}}=0.90 \pm 0.04$
performed by the D0 collaboration, we consider a $|V_{tb}|$ extraction method
that takes into account non zero d- and s-quark contributions both in
production and decay. We propose a strategy that allows to extract consistently
and in a model-independent way the quark mixing matrix elements $|V_{td}|$,
$|V_{ts}|$, and $|V_{tb}|$ from the measurement of $R$ and from single-top
measured event yields. As an illustration, we apply our method to the Tevatron
data using a CDF analysis of the measured single-top event yield with two jets
in the final state one of which is identified as a $b$-quark jet. We constrain
the $|V_{tq}|$ matrix elements within a four-generation scenario by combining
the results with those obtained from direct measurements in flavor physics and
determine the preferred range for the top-quark decay width within different
scenarios.

View original: http://arxiv.org/abs/1202.4694