Flavor and CP Invariant Composite Higgs Models

TL;DR

Flavor protection in composite Higgs models with partial compositeness faces severe CP-odd constraints. The paper develops two protection schemes: (i) Minimal Flavor Violation achieved by a flavor-symmetric strong sector, enabling light-quark compositeness and distinctive LHC signatures, and (ii) a CP-invariant strong sector in which CP violation is driven by elementary mixings, yielding Minimal CP Violation and potentially alleviating EDM bounds. It analyzes 4-Fermi and dipole operators, discusses EDM constraints, and maps the resulting phenomenology to dijet searches and resonance production at the LHC, highlighting sizable cross-sections for right-handed light-quark compositeness. A complementary CP-invariant approach shows how CKM-like CP violation can be generated while keeping CP-odd observables under control, suggesting two coherent routes to natural CHMs with testable collider consequences.

Abstract

The flavor protection in composite Higgs models with partial compositeness is known to be insufficient. We explore the possibility to alleviate the tension with CP odd observables by assuming that flavor or CP are symmetries of the composite sector, broken by the coupling to Standard Model fields. One realization is that the composite sector has a flavor symmetry SU(3) or SU(3)_U x SU(3)_D which allows us to realize Minimal Flavor Violation. We show how to avoid the previously problematic tension between a flavor symmetric composite sector and electro-weak precision tests. Some of the light quarks are substantially or even fully composite with striking signals at the LHC. We discuss the constraints from recent dijet mass measurements and give an outlook on the discovery potential. We also present a different protection mechanism where we separate the generation of flavor hierarchies and the origin of CP violation. This can eliminate or safely reduce unwanted CP violating effects, realizing effectively "Minimal CP Violation" and is compatible with a dynamical generation of flavor at low scales.

Figures (6)

• Figure 1: Penguin diagram. The photon attaches to the fermion and to charged scalars.
• Figure 2: a) Production cross-section for $p p \to \rho$ of the gluon resonance at LHC7 (dashed) and LHC14 (solid) for $g_\rho=3$ obtained with Madgraph madgraph. The gray line corresponds to the anarchic scenario and the red line to the scenario with fully composite right handed fermions. b) Cross-section for $p p \to \rho\to q_i q_i$ with $i=u,d,c,s,b$ as a function of the $\rho$-mass and the right-handed mixing angles. We show the constraint from compositeness (blue) and the region excluded by the dijet resonance search (red). See text for details.
• Figure 3: Total cross-section of associated production of partners of the first two generations at LHC7 and LHC14 obtained with Madgraph mad graph for $g_\rho =3$, $\sin \varphi_{u_R} = 0.7$, $\sin \varphi_{d_R} = 1/6$. The blue region shows the parameter space excluded by compositeness searches LHCcompositeness. The dijet resonance search does not lead to a constraint for this choice of parameters.
• Figure 4: Dominant contribution to $\sigma(pp\to \rho \to \chi q)$.
• Figure 5: On the left we plot real and imaginary parts of the Jarlskog invariant corresponding to different points of the sample of example $g_\rho=3$. The contour lines show the distribution of points. On the right, we show real and imaginary parts of the Wilson coefficient $C_4^K$ normalized with the respective experimental bound.