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1. Testable flavored TeV-scale resonant leptogenesis with MeV-GeV dark matter in a neutrinophilic two-Higgs-doublet model

   https://doi.org/10.1103/b5sk-5f3d  

   Huang, Peisi; Zhang, Kairui (June 2025, Physical Review D)

   We explore flavored resonant leptogenesis embedded in a neutrinophilic two-Higgs-doublet model. Successful leptogenesis is achieved by the very mildly degenerate two heavier right-handed neutrinos (RHNs) 𝑁2 and 𝑁3 with a level of only Δ⁢𝑀32/𝑀2∼𝒪⁡(0.1%–1%). The lightest RHN, with a MeV–GeV mass, lies below the sphaleron freeze-out temperature and is stable, serving as a dark matter candidate. The model enables TeV-scale leptogenesis while avoiding the extreme mass degeneracy typically plaguing conventional resonant leptogenesis. Baryon asymmetry, neutrino masses, and potentially even dark matter relic density can be addressed within a unified, experimentally testable framework. 

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2. Leptogenesis with dynamical couplings

   https://doi.org/10.1103/PhysRevD.110.115006  

   Huang, Peisi; Xu, Tao (December 2024, Physical Review D)

   We propose a novel leptogenesis mechanism with a temperature-dependent coupling between the right-handed neutrino and Standard Model particles. This coupling experiences suppression at high temperatures and becomes sizable when the lepton asymmetry washout processes are Boltzmann-suppressed. Such a feature ensures that the washout rates remain consistently below the Hubble expansion rate, preserving all lepton asymmetry generated in the decay of right-handed neutrinos. We illustrate the feasibility of this mechanism with two example models and show that the observed baryon asymmetry of the Universe can be successfully obtained for right-handed neutrino masses larger than ${10}^9\mathrm{GeV}$as well as for smaller violation of charge-parity symmetry. Published by the American Physical Society2024 

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3. Radiative Majorana neutrino masses in a parity solution to the strong CP problem

   https://doi.org/10.1007/JHEP03(2024)047  

   Hall, Lawrence J; Harigaya, Keisuke; Shpilman, Yogev (March 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> The strong CP problem is solved in Parity symmetric theories, with the electroweak gauge group containing SU(2)_L× SU(2)_Rbroken by the minimal set of Higgs fields. Neutrino masses may be explained by adding the same number of gauge singlet fermions as the number of generations. The neutrino masses vanish at tree-level and are only radiatively generated, leading to larger couplings of right-handed neutrinos to Standard Model particles than with the tree-level seesaw mechanism. We compute these radiative corrections and the mixing angles between left- and right-handed neutrinos. We discuss sensitivities to these right-handed neutrinos from a variety of future experiments that search for heavy neutral leptons with masses from tens of MeV to the multi-TeV scale. 

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4. Conformal leptogenesis in composite Higgs models

   https://doi.org/10.1007/JHEP02(2025)132  

   Agashe, Kaustubh; Du, Peizhi; Ekhterachian, Majid; Fong, Chee Sheng; Hong, Sungwoo; Vecchi, Luca (February 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> 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 callConformal 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 forallthe generations of SM neutrinos, which is currently consistent with all constraints but may be within reach of future colliders. 

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5. Leptogenesis during an era of early SU(2) confinement

   https://doi.org/10.1103/nmpt-fwz6  

   Bhalla-Ladd, India; Ginnett, Izzy; Tait, Tim_M P (October 2025, Physical Review D)

   We explore leptogenesis during a cosmological epoch during which the electroweak $\mathrm{SU}(2{)}_L$force is confined. During weak confinement, there is only one conserved nonanomalous global charge, $r$, which is a linear combination of lepton-number, baryon-number, and hypercharge. The inclusion of heavy Majorana neutrinos leads to an $r$-charge and $CP$-violating interaction with a composite scalar, $\mathrm{\Phi }$, and composite fermions, $\mathrm{\Psi }$, allowing for the generation of an $r$-charge asymmetry, which translates into a baryon asymmetry post $\mathrm{SU}(2{)}_L$deconfinement. Determining the resulting baryon asymmetry as a function of the model parameters, we find that the predicted baryon-asymmetry can match observations for a wide swath of parameter space: a weak confinement scale ${\mathrm{\Lambda }}_W\sim {10}^{11}–{10}^{14}\mathrm{GeV}$, the sum of the Standard Model Yukawa couplings $\sum Y_{i\alpha }{Y}_{i\alpha }^{*}\sim {10}^{-2}-{10}^0$, $m_{\mathrm{\Phi }}/m_{\mathrm{\Psi }}\sim 0-0.5$, and a $\mathrm{\Phi }-\mathrm{\Psi }-\mathrm{\Psi }$coupling $\left|g\right|\sim 1$with complex phase ${\theta }_g\sim \pi /4$. While leptogenesis under the assumption of a standard cosmology relies on the complex phase of the neutrino Yukawa couplings, the asymmetry generated in this novel background cosmology primarily depends on a strong phase from $\mathrm{SU}(2{)}_L$confinement, ${\theta }_g$, and favors negligible $CP$-violation in the right-handed neutrino decays. 

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