A chiral SU(4) explanation of the $b\to s$ anomalies

Abstract

We propose a variant of the Pati-Salam model, with gauge group $SU(4{)}_C\times SU(2{)}_L\times U(1{)}_{Y^{\prime }}$, in which the chiral left-handed quarks and leptons are unified into a $\underline{4}$ of $SU(4{)}_C$, while the right-handed quarks and leptons have quite a distinct treatment. The $SU(4{)}_C$ leptoquark gauge bosons can explain the measured deviation of lepton flavour universality in the rare decays: $\bar{B}\to {\bar{K}}^{(\ast )}\bar{\ell }\ell ,\ell =\mu ,e$ (taken as a hint of new physics). The model satisfies the relevant experimental constraints and makes predictions for the important $B$ and $\tau$ decays. These predictions will be tested at the LHCb and Belle II experiments when increased statistics become available.

Comments: 10 pages, 4 figures; references added, minor changes to match version published in PRD