Title: Chiral U (1)X Gauge Symmetries and Their Phenomenological Implications
Speaker: Hemant Kumar Prajapati
Abstract:
While the Standard Model is highly successful, phenomena like dark matter and neutrino oscillations require new physics. A well-motivated remedy is extending the SM with an additional Abelian $U(1)_X$ gauge symmetry.
In this talk, I present new chiral $U(1)_X$ extensions of the SM and explore their phenomenological implications across two distinct frameworks. First, I discuss flavor-universal chiral models where anomaly cancellation requires introducing three dark fermions, providing a natural dark matter. The $Z'$ gauge boson mediates interactions between the dark and visible sectors, and we call this $U(1)_X$ symmetry as the “Dark hypercharge” symmetry. We analyze both heavy ($M_{Z'} > M_Z$) and light ($M_{Z'} < M_Z$) $Z'$ scenarios using collider, CE$\nu$NS, and E$\nu$ES data. I will also discuss how $U(1)_X$ gauge extension can explain the CDF-II W boson mass anomaly. Second, I introduce flavor-specific chiral models that naturally generate mixed vector-axial or pure axial-vector couplings for a light $Z'$. Using representative benchmarks, we demonstrate that this framework successfully accommodates global fits to $b \to s$ observables while respecting $B$ and $K$ meson mixing constraints. Finally, we show how this framework realizes the necessary axial-vector couplings to explain the ATOMKI anomaly while satisfying stringent low-energy and collider bounds.