Explaining the $R_{K^{(\ast )}}$ anomalies and the CDF $M_W$ in Flavorful Top Seesaw Models with Gauged $U(1{)}_{L(-R)}$

Abstract

A new heavy $Z^{\prime }$ vector boson provides a possible explanation for the neutral current B anomalies and points to the scale where we expect the solution to the hierarchy problem to appear. In this paper, we explore a modified Top Seesaw model based on the global symmetry breaking of $U(3{)}_L$ to $U(2{)}_L$. The symmetry is partially gauged such that the breaking introduces not only a composite Higgs doublet but also a TeV-scale $Z^{\prime }$ boson. The $U(3{)}_L/U(2{)}_L$ Top Seesaw model predicts a light Higgs boson as well as a large top Yukawa coupling. Additional $U(1{)}^{\prime }$ symmetry is gauged such that a flavorful TeV-scale $Z^{\prime }$ boson is introduced to address the B anomalies. The existence of a heavy vector-like top quark and $Z-Z^{\prime }$ mixing breaks the custodial symmetry, which predicts a heavier $W$ mass as observed by the CDF collaboration. Two possible candidates for the $U(1{)}^{\prime }$ symmetry corresponding to the $Z^{\prime }$ boson, $U(1{)}_L$ and $U(1{)}_{L-R}$, are discussed in detail. The parameter space for the models to address both anomalies is presented. The direct searches of the $Z^{\prime }$ boson from dilepton channels are also studied. Based on the assumptions, a TeV-scale $Z^{\prime }$ boson is still viable and can be probed in the near future.

Comments: 27 pages, 4 figures; v2: some typos corrected and comments added; v3: some equations corrected and comments on new LHCb measurements added