Linking R_K^（*） anomalies to Hubble tension via a single right-handed neutrino

【摘要】 Updated measurements from the LHCb and SH0ES collaborations have respectively strengthened the deviations of the ratio R_K in rare semi-leptonic B-meson decays and the present-day Hubble parameter H₀ in the Universe,implying tantalizing hints of new physics beyond the standard model.In this paper,we consider a simple flavor-specific two-Higgs-doublet model,where long-standing R_K^（*） anomalies can be addressed by a one-flavor righthanded neutrino.An intriguing prediction resulting from the parameter space for the R_K^（*） resolution under flavorand collider-physics constraints points toward a shift in the effective neutrino number,ΔN_eff=N_eff-N_eff^SM,as a favored way to ease the H₀ tension.Depending on whether the neutrino is of the Dirac or Majorana type,we show that the resulting shift is ΔN_eff■1.0 for the former case and ΔN_eff■0.5 for the latter case.While the Dirac case is disfavored by the CMB polarization measurements,the Majorana solution is consistent with recent studies using a combined dataset from various sources.Consequently,such a simple flavor-specific two-Higgs-doublet model provides a link between R_K^（*） anomalies and H₀ tension,which in turn can be readily verified or disproved by upcoming measurements.更多还原

【Abstract】 Updated measurements from the LHCb and SH0ES collaborations have respectively strengthened the deviations of the ratio R_K in rare semi-leptonic B-meson decays and the present-day Hubble parameter H₀ in the Universe,implying tantalizing hints of new physics beyond the standard model.In this paper,we consider a simple flavor-specific two-Higgs-doublet model,where long-standing R_K^（*） anomalies can be addressed by a one-flavor righthanded neutrino.An intriguing prediction resulting from the parameter space for the R_K^（*） resolution under flavorand collider-physics constraints points toward a shift in the effective neutrino number,ΔN_eff=N_eff-N_eff^SM,as a favored way to ease the H₀ tension.Depending on whether the neutrino is of the Dirac or Majorana type,we show that the resulting shift is ΔN_eff■1.0 for the former case and ΔN_eff■0.5 for the latter case.While the Dirac case is disfavored by the CMB polarization measurements,the Majorana solution is consistent with recent studies using a combined dataset from various sources.Consequently,such a simple flavor-specific two-Higgs-doublet model provides a link between R_K^（*） anomalies and H₀ tension,which in turn can be readily verified or disproved by upcoming measurements.更多还原