Oblique Parameters and Extra Generations via OPUCEM

TL;DR

This paper uses an improved computational tool, OPUCEM, to analyze how additional fermion generations fit within current electroweak precision data, revealing that multiple extra generations are still compatible with observations.

Contribution

The paper introduces recent enhancements to OPUCEM and demonstrates that multiple extra fermion generations can exist within current electroweak constraints, expanding previous limits.

Findings

Fourth generation with Dirac neutrinos is allowed.

Majorana neutrinos enlarge the allowed parameter space.

Up to 6 generations are compatible with data.

Abstract

Recent improvements to OPUCEM, the tool for calculation of the contributions of various models to oblique parameters, are presented. OPUCEM is used to calculate the available parameter space for the four family Standard Model given the current electroweak precision data. It is shown that even with the restrictions on Higgs boson and new quark masses presented in the 2011 autumn conferences, there is still enough space to allow a fourth generation with Dirac type neutrinos. For Majorana type neutrinos, the allowed region is even larger. The electroweak precision data also favors non-zero mixing between light and fourth generations, thus effectively reducing current experimental limits. Additionally, calculations with OPUCEM show that even 5th and 6th generations are compatible with the existing electroweak precision data, with a probability comparable to or higher than the Standard Model with 3 generations.