2026/07/31 by Benoît Assi, Ryan Plestid, Amartya Sengupta +1
Physics and Astronomy · #hep-ph #hep-ex #hep-th
42 pages, 6 figures
arxiv created 2026/07/31 · arxiv updated 2026/08/04
We study the flavour structure of an SU(15)p confining chiral gauge theory in which the Standard Model (SM) quarks, leptons, and Higgs emerge as composite bound states. The couplings of two scalar fields in the conjugate antisymmetric (105) and conjugate symmetric (120) representations of SU(15)p provide two SU(4)F flavour-breaking spurions that generate both the SM Yukawa couplings and the flavour-changing processes. The up and down Yukawa matrices are tightly-correlated due to a "right-handed isospin" symmetry, which predicts a trivial CKM matrix in the absence of spontaneous symmetry breaking. The lepton Yukawas are correlated with the quarks due to a common source of flavour spurions. With a judicious Froggatt-Nielsen-like texture for the two flavour spurions we find that a benchmark fit with O(1) non-perturbative coefficients reproduces all six quark masses, three charged lepton masses, and the CKM matrix. The same spurions mediate charged lepton flavour violation, neutral meson mixing, rare kaon decays, and induce electric dipole moments. We compare the reach on the compositeness scale Λ\rm pre across these observables in the numerical benchmark and find that the electron EDM and K0-K0 mixing provide the strongest sensitivity, reaching O(104) TeV, the lower end of the range probed by proton decay, while μ→ eγ, D0-D0 mixing, and μ-e conversion give complementary reach at 102-103 TeV. The projected electron EDM sensitivity extends this to O(106) TeV, beyond the reach of planned proton decay searches.