arXiv subjects

Afif Omar

Publications and source records attributed to Afif Omar.

4 recordsLinked to original sources

arXiv2026

Neutrino Electroweak Couplings and the Neutrino Fog at Belle II

The mono-photon process $e^+e^- \to \gamma+\mathrm{invisible}$ at Belle II probes both invisible new states and the electroweak couplings of neutrinos. In this work, we study the process $e^+e^- \to \gamma\nu\bar{\nu}$, finding that Belle II with the full expected dataset can determine the neutrino-sensitive effective weak mixing angle to a 3.6$\%$ relative statistical precision, competitive with existing neutrino probes at other energy scales. Polarized beams, as proposed for the Chiral Belle upgrade, separate the neutral- and charged-current contributions and provide independent access to each, giving a handle on the chiral structure of the neutrino gauge interactions. The same process is an irreducible background to dark boson searches, producing a neutrino fog once the luminosity exceeds 1 ab$^{-1}$.

hep-ph↗

arXiv2025

BBN Constraints on the Hadronic Annihilation of sub-GeV Dark Matter

We investigate the impact of residual annihilation from sub-GeV mass thermal relic dark matter candidates during big bang nucleosynthesis (BBN). Focusing on candidates with $p$-wave annihilation channels, we show that the hadronic injection of pions and kaons beyond freeze-out, and their subsequent interaction with protons and neutrons prior to the deuterium bottleneck, provides a sensitivity to annihilation that surpasses that of the CMB and indirect detection in the galaxy.

hep-ph↗

arXiv2025

Characterizing Dark Bosons at Chiral Belle

We explore the advantages of a polarized electron beam at Belle II, as proposed for ``Chiral Belle'', in the search for invisibly decaying (dark) bosons that weakly couple to the Standard Model. By measuring the polarization dependence of the production cross section of dark bosons in association with a photon, the dark boson's spin and Lorentz structure of its couplings can potentially be determined. We analyze the mono-photon channel, $e^+ e^- \rightarrow \gamma + \text{invisible}$, in detail, focusing on the production of an on-shell spin-1 boson. We explore this in the context of three separate scenarios for a new dark vector: a dark photon, a mass-mixed ``dark $Z$'', and a vector that couples to right-handed electrons, and estimate how well the couplings of such bosons to electrons can be constrained in the event of a positive signal.

hep-ph↗

arXiv2024

Early Dark Energy During Big Bang Nucleosynthesis

We study the impact of an early dark energy component (EDE) present during big bang nucleosynthesis (BBN) on the elemental abundances of deuterium D/H, and helium $Y_p$, as well as the effective relativistic degrees of freedom $N_{\rm eff}$. We consider a simple model of EDE that is constant up to a critical time. After this critical time, the EDE transitions into either a radiation component that interacts with the electromagnetic plasma, a dark radiation component that is uncoupled from the plasma, or kination that is also uncoupled. We use measured values of the abundances and $N_{\rm eff}$ as determined by CMB observations to establish limits on the input parameters of this EDE model. In addition, we explore how those parameters are correlated with BBN inputs; the baryon to photon ratio $\eta_b$, neutron lifetime $\tau_n$, and number of neutrinos $N_\nu$. Finally, we study whether this setup can alleviate the tension introduced by recent measurements of the primordial helium abundance.

hep-ph↗