Fourth generation quark mass limits in CKM-element space

TL;DR

This paper reanalyzes CDF data to extend fourth-generation quark mass limits across all possible flavor-mixing scenarios, showing that current constraints are more broadly applicable than previously thought.

Contribution

It provides a comprehensive reinterpretation of existing data to establish more general mass limits in the four-generation CKM parameter space.

Findings

Mass limits of 290 GeV and above across various mixing scenarios.

Current CKM constraints do not further restrict fourth-generation quark masses.

Reanalysis broadens the applicability of existing experimental limits.

Abstract

We present a reanalysis of CDF data to extend limits on individual fourth-generation quark masses from particular flavor-mixing rates to the entire space of possible mixing values. Measurements from CDF have set individual limits on masses, $m_{b'}$ and $m_{t'}$, at the level of $335$--$385$ GeV assuming specific and favorable flavor-mixing rates. We consider the space of possible values for the mixing rates and find that the CDF data imply limits of $290$ GeV and greater over a wide range of mixing scenarios. We also analyze the limits from the perspective of a four-generation CKM matrix. We find that present experimental constraints on CKM elements do not suggest further constraints on fourth-generation quark masses.