Physics and Astronomy Seminar (In-Person): Afif Omar, University of Victoria

“ Probing the Dark Universe with Big Bang Nucleosynthesis and Belle II ” Dark energy and dark matter account for roughly 95% of the energy budget of the Universe, yet little about their properties is known to date. In this talk, I will discuss how the MeV-GeV energy scale can be probed through two complementary directions in order to shed light on the dark Universe. Cosmic microwave background (CMB) observations, along with precise laboratory measurements of nuclear reaction rates, render big bang nucleosynthesis (BBN) an essentially parameter-free framework, and an excellent probe of new physics. I will illustrate how BBN can be used to constrain non-standard energy evolution due to an early dark energy (EDE) component that redshifts away after some critical temperature. In addition, BBN provides sensitivity to velocity-suppressed dark matter (DM) annihilation into hadrons that surpasses that of the CMB and indirect detection in the Galaxy. The second direction comes from terrestrial probes of dark sectors, for example by searching for missing energy at lepton colliders. I will discuss how Belle II can be used to search for dark bosons, and specifically how polarizing the electron beam (dubbed Chiral Belle) can provide valuable distinguishing power between different dark-sector models. Though the cosmological and terrestrial searches rely on very different approaches, the insights they provide on the dark Universe are closely connected.