arXiv subjects

Zong-Huan Ye

Publications and source records attributed to Zong-Huan Ye.

3 recordsLinked to original sources

arXiv2026

Electroweak right-handed neutrino portal dark matter

We study dark matter coupled to the Standard Model via electroweak scale right-handed neutrinos in a Type-I seesaw framework. We consider a minimal dark sector containing a fermion $χ$ and a complex scalar $ϕ$ whose only connection to the Standard Model is through renormalizable Yukawa interactions with right-handed Majorana neutrinos, thus realizing a neutrino portal after seesaw mixing. We discuss three representative realizations of electroweak right-handed neutrinos arising from the Type-I seesaw mechanism, spanning small, tiny, and ultraweak couplings to the Standard Model sector, so that the dark particles can either undergo secluded freeze-out or be produced via freeze-in. Instead of merely estimating the order of magnitude of the seesaw couplings, we use the Particle Swarm Optimization algorithm to obtain viable seesaw parameter sets consistent with neutrino data and other constraints, and then compute the coupled evolution of the dark particles and right-handed neutrinos, reproducing the observed dark matter relic abundance in representative benchmark scenarios. For freeze-out, dark matter depletion is controlled by coupled dark sector dynamics, requiring a full Boltzmann treatment for a reliable relic abundance. For freeze-in, internal dark interactions also alter the relic density: treating hidden particles as independent components with late decays added afterward can misestimate the abundance by $30\%$ or even $95\%$, depending on the interaction structure. Electroweak right-handed neutrino portal dark matter thus provides a robust and predictive framework that tightly connects neutrino physics, heavy neutral lepton phenomenology, and the cosmological dark matter relic density, offering a well-motivated benchmark for complementary collider, neutrino, and cosmological probes at the high energy frontier.

hep-ph↗

arXiv2026

Supercool with PPO: Exploring Supercooled Phase Transitions via Reinforcement Learning

Gravitational waves from cosmological first-order phase transitions provide a powerful probe of hidden sectors and beyond the Standard Model physics. However, identifying phenomenologically relevant benchmark points remains computationally challenging, since viable and detectable signals typically occupy only a small fraction of the scanned parameter space. In this work, we introduce a reinforcement learning strategy based on Proximal Policy Optimization (PPO) to accelerate the search for gravitational wave signals from supercooled phase transitions in a minimal dark $U(1)_x$ sector. We construct a numerical reinforcement learning environment that maps the microscopic model parameters to the corresponding phase transition and gravitational wave observables, using a gauge-independent low-temperature formulation of the effective action. Several reward designs are developed to guide the agent toward parameter regions producing large gravitational wave amplitudes, broad frequency coverage, and detector sensitive benchmark points. We compare the PPO scans with conventional Monte Carlo scans in both narrow and broad windows of the $U(1)_x$ vacuum expectation value. Our results demonstrate that PPO provides an efficient goal-directed search strategy for gravitational wave phenomenology and offers a broadly applicable framework for learning-assisted exploration of high-dimensional scientific parameter spaces.

hep-ph↗

arXiv2026

Gauge-independent Gravitational Waves from Cogenesis in a $B-L$ Conserving Universe

An analysis of baryogenesis and stochastic gravitational wave production is presented for an extension of the standard model where the dark sector consists of dark matter particles charged under a $U(1)_x$ gauge symmetry, while a subset of dark fields also carry lepton number but no $U(1)_x$ charge. We demonstrate that with CP violation induced by Yukawa couplings, equal and opposite lepton asymmetries are generated in the visible and hidden sectors. Subsequent evolution preserves lepton number separately in each sector, and sphaleron interactions partially convert the lepton asymmetry into baryon asymmetry near the temperature of the first-order phase transition. Further, we discuss stochastic gravitational wave background production for the first-order phase transition using a gauge-independent bubble nucleation dynamics which yields spectra also valid in the supercooled low-temperature regime with {$T_p/m_{A_x} \ll 1$} where $T_p$ is the percolation temperature and $m_{A_x}$ is the dark photon mass. A parameter-space scan identifies regions that simultaneously account for cogenesis of baryon asymmetry and dark matter and predict stochastic gravitational wave signals within reach of current (NANOGrav, EPTA, PPTA) and future detectors at higher frequencies, providing a unified framework for cogenesis and associated gravitational wave production.

hep-ph↗