Dispersive determination of fourth generation quark masses

We determine the masses of the sequential fourth generation quarks b′ and t′ in the extension of the Standard Model by solving the dispersion relations associated with the mixing between the neutral states Qq¯ and Q¯q, with Q (q) being a heavy (light) quark. The box diagrams responsible for the mixing, which provide the perturbative inputs to the dispersion relations, involve multiple intermediate channels, i.e., the ut and ct channels, u (c, t) being an up (charm, top) quark, in the b′ case, and the db′, sb′, and bb′ ones, d (s, b) being a down (strange, bottom) quark, in the t′ case. The common solutions for the above channels lead to the masses mb′=(2.7±0.1) and mt′≈200 TeV unambiguously. We show that these superheavy quarks, forming bound states in a Yukawa potential, barely contribute to Higgs boson production via gluon fusion and decay to photon pairs and bypass current experimental constraints. The mass of the b¯′b′ ground state is estimated to be about 3.2 TeV. It is thus worthwhile to continue the search for b′ quarks or b¯′b′ resonances at the (high-luminosity) Large Hadron Collider. Published by the American Physical Society 2024