Conformal Leptogenesis in Composite Higgs Models

TL;DR

This paper introduces Conformal Leptogenesis, a novel mechanism for baryon asymmetry generation in Composite Higgs models involving out-of-equilibrium decays of heavy neutrinos within a conformal field theory framework, accounting for phase transitions and washout effects.

Contribution

It develops the first complete description of leptogenesis in Composite Higgs models with conformal dynamics, including Boltzmann equations based on CFT correlation functions.

Findings

Conformal Leptogenesis can reproduce the observed baryon asymmetry.

The scenario predicts sizable neutrino compositeness consistent with current constraints.

The mechanism remains viable across a broad parameter space.

Abstract

We study the generation of the baryon asymmetry in Composite Higgs models with partial compositeness of the Standard Model (SM) fermions and heavy right-handed neutrinos, developing for the first time a complete picture of leptogenesis in that setup. The asymmetry is induced by the out of equilibrium decays of the heavy right-handed neutrinos into a plasma of the nearly conformal field theory (CFT), i.e. the deconfined phase of the Composite Higgs dynamics. This exotic mechanism, which we call Conformal Leptogenesis, admits a reliable description in terms of a set of ``Boltzmann equations'' whose coefficients can be expressed in terms of correlation functions of the CFT. The asymmetry thus generated is subsequently affected by the supercooling resulting from the confining phase transition of the strong Higgs sector as well as by the washout induced by the resonances formed after the transition. Nevertheless, a qualitative description of the latter effects suggests that conformal leptogenesis can successfully reproduce the observed baryon asymmetry in a wide region of parameter space. A distinctive signature of our scenarios is a sizable compositeness for all the generations of SM neutrinos, which is currently consistent with all constraints but may be within reach of future colliders.