Decays of the heavy top and new insights on ϵK in a one-VLQ minimal solution to the CKM unitarity problem

• Published in: The European physical journal. C, Particles and fields Vol. 82; no. 4
• Main Authors: Botella, Francisco J., Branco, G. C., Rebelo, M. N., Silva-Marcos, J. I., Bastos, José Filipe
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.04.2022; Springer Nature B.V
• Subjects: Astronomy; Astrophysics and Cosmology; Decay rate; Elementary Particles; Hadrons; Heavy Ions; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Parameterization; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quarks; Regular Article - Theoretical Physics; String Theory; Upper bounds
• ISSN: 1434-6052; 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-022-10299-9

We propose a minimal extension of the Standard Model where an up-type vector-like quark, denoted T , is introduced and provides a simple solution to the CKM unitarity problem. We adopt the Botella-Chau parametrization in order to extract the 4 × 3 quark mixing matrix which contains the three angles of the 3 × 3 CKM matrix plus three new angles denoted θ 14 , θ 24 , θ 34 . It is assumed that the mixing of T with standard quarks is dominated by θ 14 . Imposing a recently derived, and much more restrictive, upper-bound on the New Physics contributions to ϵ K , we find, in the limit of exact θ 14 dominance where the other extra angles vanish, that ϵ K NP is too large. However, if one relaxes the exact θ 14 dominance limit, there exists a parameter region, where one may obtain ϵ K NP in agreement with experiment while maintaining the novel pattern of T decays with the heavy quark decaying predominantly to the light quarks d and u . We also find a reduction in the decay rate of K L → π 0 ν ν ¯ .