The fourth generation, linac-ring type colliders, preons and so on

TL;DR

The paper reviews recent developments in collider physics, discusses tensions in minimal SM4 Higgs data, and advocates for linac-ring colliders like LHeC and TAC for QCD and charm physics, while exploring the possibility of preonic fundamental particles.

Contribution

It highlights the potential of linac-ring colliders for QCD and charm physics and discusses the implications of Higgs data tensions for minimal SM4 and preonic models.

Findings

Minimal SM4 is in tension with LHC Higgs data.

Linac-ring colliders like LHeC and TAC can advance QCD and charm physics.

Preonic models are considered as a deeper layer of fundamental particles.

Abstract

Following a brief review of our contributions to the 2006 European PP Strategy, recent comments on several topics are presented. First of all, it is emphasized that only the simplest version of the fourth chiral generation, namely, minimal SM4 (mSM4) with only one Higgs doublet is in some tension with the recent LHC data on the Higgs boson search. This tension, which follows from the relative strengths of the H --> 4l and Higgs --> {\gamma}{\gamma} channels, can be naturally resolved if there is a mechanism to enhance the H-->{\gamma}{\gamma} width (although any charged and heavy particle could enhance the H-{\gamma}-{\gamma} loop, 2HDM can be given as an example). We then emphasize the possible role of the linac-ring type colliders, especially LHeC (QCD Exploder) and TAC super charm factory. The QCD Explorer will give opportunity to enlighten the origin of the 98.5% portion of the visible universe's mass. Especially the {\gamma}-nucleus option seems to be very promising for QCD studies. The TAC super charm factory may provide opportunity to investigate the charm physics with statistics well above that of the dedicated runs at Super-B factories. Finally, it is argued that the history of particle physics (and, more generally, the history of the investigation of the fundamental ingredients of the matter), a large number of "fundamental" particles, an inflation of observable free parameters, and, especially, the mixing of "fundamental" fermions favor the idea of a new set of fundamental particles at a deeper level. These new particles can be formulated with the preonic or even pre-preonic models.