A global analysis of $$b \rightarrow s \ell \ell $$ data in heavy and light $$Z'$$ models

Abstract

AbstractWe perform a model-independent global fit to all $$b \rightarrow s \ell \ell $$ b → s ℓ ℓ data in the light of recent measurements of the lepton flavour universality violating (LFUV) observables $$R_{K_S^0}$$ R K S 0 , $$R_{K^{*+}}$$ R K ∗ + , and the updated observables in $$B_s \rightarrow \phi \mu ^+ \mu ^-$$ B s → ϕ μ + μ - decay, by the LHCb collaboration. Assuming NP only in the muon sector, we find that the 1D NP scenarios $$C_9^{\textrm{NP}} <0 $$ C 9 NP < 0 and $$C_{9}^{\textrm{NP}}=-C_{10}^{\textrm{NP}}$$ C 9 NP = - C 10 NP continue to be the most favoured ones. However, the significance of the favoured scenario $$C_{9}^{\textrm{NP}}=-C'_{9}$$ C 9 NP = - C 9 ′ has reduced and the updated data now marginally prefers $$C_{10}^{\textrm{NP}} > 0$$ C 10 NP > 0 scenario. The 2D scenarios $$(C_9^{\textrm{NP}}, C_{10}^{\prime } )$$ ( C 9 NP , C 10 ′ ) , $$(C_9^{\textrm{NP}}, C_{9}^{\prime } )$$ ( C 9 NP , C 9 ′ ) and $$(C_9^{\textrm{NP}}, C_{10}^{\textrm{NP}} )$$ ( C 9 NP , C 10 NP ) , continue to be favoured by the data in the listed order. We analyse generic TeV scale $$Z'$$ Z ′ models which can generate the 1D scenarios, $$C_9^{\textrm{NP}} <0 $$ C 9 NP < 0 and $$C_9^{\textrm{NP}} = -C_{10}^{\textrm{NP}}$$ C 9 NP = - C 10 NP as well as 2D scenarios $$(C_9^{\textrm{NP}}, C_{9}^{\prime } )$$ ( C 9 NP , C 9 ′ ) and $$(C_9^{\textrm{NP}}, C_{10}^{\textrm{NP}} )$$ ( C 9 NP , C 10 NP ) . We find that all four models provide an equally good fit to the data. We also consider a model with a 25 MeV $$Z'$$ Z ′ that couples to muons only and has a $$q^2$$ q 2 dependent $$b - s$$ b - s coupling. We study the implications of the current data on the LFUV observables $$R_{\phi }$$ R ϕ , $$Q_{4,5}$$ Q 4 , 5 as well as $$R_{K^{(*)}}$$ R K ( ∗ ) in the high $$q^2$$ q 2 . We find that the $$Q_{4,5}$$ Q 4 , 5 observables have a potential to discriminate between a few favored solutions, and disentangle different heavy and light $$Z'$$ Z ′ scenarios.