Measuring the Magnitude of the Fourth-Generation CKM4 Matrix Element V_{t'b'}

TL;DR

This paper investigates how to measure the CKM4 matrix element V_{t'b'} by analyzing heavy quark decays in a four-generation Standard Model extension, focusing on decay ratios and LHC measurement prospects.

Contribution

It proposes a method to determine |V_{t'b'}| from decay branching ratios and discusses experimental measurement strategies at the LHC.

Findings

|V_{t'b'}| can be extracted from decay ratio measurements.

The decay modes of t' are highly sensitive to |V_{t'b'}|.

Estimates of measurement precision at the LHC are provided.

Abstract

We study the decays of heavy chiral (t', b') quarks in a four-generation extension of the Standard Model. If the difference between the t' and b' masses is smaller than the W mass, as favored by precision electroweak measurements, then the Cabibbo-Kobayashi-Maskawa favored, on-shell decay t'-->b'W is forbidden. As a result, other t' decays have substantial branching fractions, which are highly sensitive to the magnitude of the diagonal CKM matrix element V_{t'b'}. We show that |V_{t'b'}| can be determined from the ratio of the two-body and three-body t'-decay branching fractions and estimate the precision of such a measurement at the LHC. We discuss the hadronization of a t' for large enough values of |V_{t'b'}|.