Once more on extra quark-lepton generations and precision measurements

TL;DR

This paper investigates how an additional quark-lepton generation can be consistent with precision electroweak measurements, even with heavy new particles, challenging previous constraints on new physics models.

Contribution

It demonstrates that a single extra generation remains compatible with electroweak precision data despite heavy masses, providing new insights into possible extensions of the Standard Model.

Findings

One extra generation can satisfy electroweak constraints.

Heavy new particles do not necessarily violate precision measurements.

The results challenge previous assumptions about new physics mass bounds.

Abstract

Precision measurements of $Z$-boson parameters and $W$-boson and $t$-quark masses put strong constraints on non $SU(2)\times U(1)$ singlet New Physics. We demonstrate that one extra generation passes electroweak constraints even when all new particle masses are well above their direct mass bounds.