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TOPCHARM Report Summary

Project ID: 614794
Funded under: FP7-IDEAS-ERC
Country: Israel

Periodic Report Summary 2 - TOPCHARM (The LHC Battle for Naturalness on the Top Charm Front)

The scalar particle discovered in the Large Hadron Collider (LHC) fits into a minimal picture of spontaneously broken gauge symmetry, via the celebrated Higgs mechanism.
The mechanism has already passed several important experimental tests. Furthermore, when combined with the absence of any hints of new physics, thus far, during the second run of the LHC, it enables us to make the following qualitative statement. The Standard Model (SM) of particle physics is now complete, and it forms a consistent theory that is valid up to very high energy scales.
However, even after the Higgs discovery, major fundamental questions and several basic puzzles remain open.
There are powerful theoretical arguments, as well as observational facts, that imply
that more particles and forces exists beyond those predicted by the SM:
the non-vanishing of the neutrino mass; the baryon asymmetry of the Universe; and the evidences for dark matter (DM).
Furthermore, the SM suffers from hierarchy problems/puzzles: (i) The Higgs mass-square, being unstable against quantum corrections, is more than 32 orders of magnitude smaller than the maximal scale of validity of the SM; leading to the Higgs fine tuning problem. (ii) The flavor parameters of the SM, the fermion masses and mixings, are small and hierarchical; leading to the SM flavor puzzle.
Shedding light on any of these unsolved mysteries would lead to a revolution of our field and is likely to change the perception of our universe.
Regarding these basics questions, we note that apart from the case of the fine tuning problem, it is not possible to associate them with a concrete new physics scale. In fact, regarding electroweak symmetry breaking, it was recently proposed that the weak scale may be obtained as a result of a dynamical relaxation mechanism. These relaxion models, have a very different and largely unexplored phenomenology as described below.

It seems that a broad program is required to be able to tackle these fundamental issues, and, in accordance, the research described below is divided into two different categories:
(i) LHC driven research, searching for new physics at the energy frontier;
(ii) Studying the interplay between the physics of flavor, Higgs and naturalness.
The research done in this project is unique in the sense that it provides a unique integrated effort towards deciphering the Higgs hierarchy problem combined with the flavor hierarchy puzzle. We have already made a progress on both topic both in terms of theoretical progress and in terms of collider-oriented studies. Finally, as a spinoff of this progress we have advocated for the importance of performing “flavor of the 21st century type of research” where we probe the origin of flavor looking at the excitation of the electroweak background (the Higgs) as opposed with just doing the measurement in the “frozen” background which is the more conventional/traditional way of probing the flavor structure of the standard model of basic particles and interactions.

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