Anomalies in Bottom from new physics in Top

Abstract

We analyze the possibility to accommodate current $b \to s \ell^+ \ell^-$ anomalies with TeV-scale mediators that couple to right-handed top quarks and muons, contributing to $b \to s \ell^+ \ell^-\,$ at the one-loop level. We use the Standard Model Effective Field Theory (SMEFT) framework but also look at specific scenarios by taking into account all possible irreducible representations of the Lorentz and Standard Model gauge group for the mediators. From a global fit of $b \to s \ell^+ \ell^-$ data and LEP-I observables we find that the Wilson coefficients of two SMEFT operators: $\mathcal{O}_{\ell u}= (\bar \ell_{ L \mu} \gamma^{\alpha} \ell_{ L \mu}) (\bar t_R \gamma_{\alpha} t_R )$ and $\mathcal{O}_{e u}= (\bar \mu_{R} \gamma^{\alpha} \mu_{R}) (\bar t_R \gamma_{\alpha} t_R )$ need to satisfy $\mathcal{C}_{eu} \sim \mathcal{C}_{\ell u}$. New physics enters then in $b \to s \ell^+ \ell^-$ mainly through the operator $\mathcal{O}_9 = ( \bar s \gamma_{\mu} P_{L} b )( \bar \ell \gamma^{\mu} \ell )$ of the Weak Effective Theory. After discussing all possible mediators, we concentrate on two scenarios: A vector boson in the irreducible representation $Z_{\mu}^{\prime} \sim (1,1,0)$ of the Standard Model gauge group with vectorial coupling to muons, and a combination of two leptoquarks: the scalar $R_2 \sim (3,2,7/6)$ and the vector $\widetilde U_{1 \mu} \sim (3,1,5/3)$. We derive LHC constraints by recasting di-muon resonance, $pp \to t \bar t t \bar t$ and SUSY searches. Additionally, we analyze the prospects for discovering these mediators during the high-luminosity phase of the LHC.