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.
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Acknowledgments
We thank Riccardo Rattazzi and Emilio Trevisani for discussions, and Matthew Walters for pointing to us the relevant literature on CFT at finite temperature. The work of KA is supported by NSF Grant No. PHY-2210361 and by the Maryland Center for Fundamental Physics. PD is supported by DOE grant DOE-SC0010008. The work of ME is supported by the Swiss National Science Foundation under contract 200020-213104. ME also acknowledges the hospitality of the CERN theory group where part of this work was completed. CSF acknowledges the support by Fundacão de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Contract No. 2019/11197-6 and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) under Contract No. 304917/2023-0. The work of SH is supported by the National Research Foundation of Korea (NRF) Grant RS-2023-00211732, by the Samsung Science and Technology Foundation under Project Number SSTF-BA2302-05, and by the POSCO Science Fellowship of POSCO TJ Park Foundation. The work of LV was partly supported by the Italian MIUR under contract 202289JEW4 (Flavors: dark and intense), the Iniziativa Specifica “Physics at the Energy, Intensity, and Astroparticle Frontiers” (APINE) of Istituto Nazionale di Fisica Nucleare (INFN), and the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 860881-HIDDeN.
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Agashe, K., Du, P., Ekhterachian, M. et al. Conformal leptogenesis in composite Higgs models. J. High Energ. Phys. 2025, 132 (2025). https://doi.org/10.1007/JHEP02(2025)132
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DOI: https://doi.org/10.1007/JHEP02(2025)132