Dark matter for $b\to s{\mu }^{+}{\mu }^{-}$ anomaly in a gauged $U(1{)}_X$ model

Abstract

We propose a new physics model which has a cold dark matter candidate and can explain the $b\to s{\mu }^{+}{\mu }^{-}$ anomaly at the same time. Our model includes a scalar quark $\tilde{q}$ and a scalar lepton $\tilde{\ell }$ which are $SU(2{)}_L$-doublet as well as a Dirac fermion $N$ which is $SU(2{)}_L$-singlet. The new particles are charged under a gauged $U(1{)}_X$ group which is spontaneously broken to a discrete $Z_2$ symmetry by a dark scalar $S$. The remnant $Z_2$ symmetry stabilizes the dark matter. Box diagrams with $\tilde{q}$, $\tilde{\ell }$, and $N$ running inside the loop can generate the correct Wilson coefficients $C_9^{\mu }=-C_{10}^{\mu }$ to accommodate the $b\to s{\mu }^{+}{\mu }^{-}$ anomaly while avoiding constraints such as $B_s-{\overline{B}}_s$ mixing. The dark matter annihilation into a second generation lepton pair via $t$-channel $\tilde{\ell }$-exchanging process plays an important role in producing the current dark matter relic abundance of the universe, showing a strong interplay between the flavor and dark matter physics. We also discuss dark-gauge-interaction-dominated and Higgs-portal-dominated scenarios for dark matter physics.

Comments: 26 pages, 8 figures, published version