Stellar Light Scattering as a Probe for a Braneworld-Induced Baryogenesis Scenario

TL;DR

Addresses a baryogenesis scenario in a two-brane braneworld and derives a testable astrophysical signature. It shows the associated pseudo-scalar boson can survive as a relic and constitutes a subdominant dark matter component via freeze-in, while enabling a one-loop coupling to photons. This coupling produces a distinctive exponential spectral halo around hot stars, potentially detectable by JWST or ELT, providing a direct probe of the braneworld mechanism. The results offer a concrete observational pathway to constrain extra-dimensional baryogenesis models.

Abstract

A recent baryogenesis scenario [Phys. Rev. D 110, 023520 (2024)], rooted in a two-brane Universe model, proposed a solution to the matter-antimatter asymmetry through the dynamics of a new pseudo-scalar field. In the present paper, one investigates the phenomenological consequences of this proposal. One shows that the associated boson could persist as a relic from the early Universe, forming a subdominant component of dark matter. While its overall cosmological density is small ($\approx 0.2\%$), one demonstrates that a one-loop process facilitates an ultra-weak coupling to photons, leading to a distinctive scattering signature. One argues that this effect could produce a faint, glowing halo around massive, hot stars, characterized by a unique spectral decay. Detecting or constraining this elusive light with current and future instruments like the JWST would provide a powerful and direct observational test of the underlying braneworld dynamics and its connection to baryogenesis.

Figures (5)

• Figure 1: Feynman diagrams of interest. Simple wavy line: photon ; double wavy line: hidden photon ; simple straight line: fermion ; double straight line: hidden fermion ; dashed line: scalar boson ; dashed dotted line: Wilson line. (a): Fermion-antifermion annihilation into a boson pair. (b): Fermion-hidden antifermion (or hidden fermion-antifermion) annihilation into a boson pair. (c): Various fermion annihilation processes involving a boson, a photon (or hidden photon), or a fermion. (d): Order-two correction from the Wilson lines to the vertex of the fermion-boson interaction.
• Figure 2: Scalar boson relative comoving abundance against $\varkappa =2m/T$, showing a typical freeze-in behavior.
• Figure 3: Feynman diagrams contributing to the amplitude of the pseudo-scalar boson-photon scattering. Simple wavy line: photon ; simple straight line: fermion ; double straight line: hidden fermion ; dashed line: scalar boson. The momentum of each incoming and outgoing particle is mentioned ($p_{1},p_{2},p_{3}$ and $p_{4}$), as well as the momentum flow $k$ along the loop.
• Figure 4: Pseudo-scalar boson--photon scattering and frame used to describe the scattering. Simple wavy line: photon ; dashed line: scalar boson. The momentum of each incoming and outgoing particle is mentioned ($p_{1},p_{2},p_{3}$ and $p_{4}$) with $\left\vert \mathbf{p}_{1}\right\vert =\omega$ and $\left\vert \mathbf{p}_{3}\right\vert =\omega ^{\prime }$.
• Figure 5: Sketch of the light diffusion by the scalar bosons as a dark matter component around a star. The light from the star at pulsation $\omega$ is scattered into photons at pulsation $\omega ^{\prime }$. $Oz$ axis goes from the star center to the observer. $R_{0}$ is the star's radius. $r$ is the radius of a shell of the scalar dark matter halo and varies between $R_{0}$ and $+\infty$.