Dark hypercharge symmetry

We introduce a new class of U ( 1 ) X symmetries where all Standard Model fermions are “chiral,” i.e., the left- and right-handed components have different charges under the U ( 1 ) X symmetry. Gauge anomaly cancellation is achieved by introducing three Standard Model gauge singlet dark fermions ( f i ; i = 1 , 2, 3) charged under this symmetry. We systematically present chiral solutions for cases in which (a) one, (b) two, or (c) all three generations of Standard Model fermions are charged under the U ( 1 ) X symmetry. The U ( 1 ) X charges of these dark fermions are uniquely determined by anomaly cancellation conditions. These new fermions belong to the dark sector, with the lightest of them being a good dark matter candidate. Additionally, 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. Using a benchmark model, we explore phenomenological implications in the heavy Z ′ case ( M Z ′ > M Z ), analyzing collider constraints and examining the lightest dark fermion’s viability as dark matter. Our analysis shows that it satisfies all current dark matter constraints over a wide range of dark matter mass.