Approaching a strong fourth family

TL;DR

This paper explores the implications of a hypothetical heavy fourth quark family, proposing signals at the LHC, methods for mass reconstruction, and a neutrino mass model without right-handed neutrinos, challenging the light Higgs paradigm.

Contribution

It introduces a novel approach to detect and distinguish fourth family quarks at the LHC and proposes a new neutrino mass framework without right-handed neutrinos.

Findings

Potential LHC signals of heavy fourth family quarks via W-jet excess

Methods for reconstructing heavy quark masses using W-jets

Distinguishing fourth family quarks from vector-like quarks with same-sign lepton signals

Abstract

A heavy fourth family is an example of new physics which is well defined and familiar in some respects, but which nevertheless has radical implications. In particular it eliminates a light Higgs description of electroweak symmetry breaking. We discuss an early signal for heavy quarks at the LHC in the form of an excess of "$W$-jets", and as well show how $W$-jets may be useful in the reconstruction of the heavy quark masses. We argue that fourth family quarks can be distinguished from vector-like quarks of a similar mass at roughly the same time that a same sign lepton signal becomes visible. Given the large mass of the fourth neutrino we describe how a picture for neutrino mass emerges in the absence of right-handed neutrinos, and how it suggests the existence of a remnant flavor gauge symmetry. Based on talk given at "Second Workshop on Beyond 3 Generation Standard Model -- New Fermions at the Crossroads of Tevatron and LHC", January 2010, Taipei Taiwan.