On the Interplay of Constraints from B_s, D, and K Meson Mixing in Z^′ Models with Implications for b→ s νν Transitions

2024/12/18 by Andrzej J. Buras, Buras, Andrzej J., Peter Stangl +1
Physics and Astronomy · #Black Holes and Theoretical Physics #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Phenomenology (hep-ph) #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions

paper · pdf · doi:10.48550/arxiv.2412.14254

openalex publication_date 2024/12/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31

Abstract

Within Z^′ models, neutral meson mixing severely constrains beyond the Standard Model (SM) effects in flavour changing neutral current (FCNC) processes. However, in certain regions of the Z^′ parameter space, the contributions to meson mixing observables become negligibly small even for large Z^′ couplings. While this a priori allows for significant new physics (NP) effects in FCNC decays, we discuss how large Z^′ couplings in one neutral meson sector can generate effects in meson mixing observables of other neutral mesons, through correlations stemming from SU(2)_L gauge invariance and through Renormalization Group (RG) effects in the SM Effective Field Theory (SMEFT). This is illustrated with the example of B_s⁰- B_s⁰ mixing, which in the presence of both left- and right-handed Z^′ bs couplings Δ_L^bs and Δ_R^bs remains SM-like for Δ_R^bs≈ 0.1 Δ_L^bs. We show that in this case, large Z^′ bs couplings generate effects in D and K meson mixing observables, but that the D and K mixing constraints and the relation between Δ_R^bs and Δ_L^bs are fully compatible with a lepton flavour universality (LFU) conserving explanation of the most recent b→ sℓ⁺ℓ^- experimental data without violating other constraints like e⁺ e^-→ℓ⁺ℓ^- scattering. Assuming LFU, invariance under the SU(2)_L gauge symmetry leads then to correlated effects in b→ sνν observables presently studied intensively by the Belle II experiment, which allow to probe the Z^′ parameter space that is opened up by the vanishing NP contributions to B_s⁰- B_s⁰ mixing. In this scenario the suppression of B→ K(K^*)μ⁺μ^- branching ratios implies uniquely enhancements of B→ K(K^*)νν branching ratios up to 20%.

Related

• Z^′-Tandem Mechanism for the Suppression of New Physics in Quark Mixing with Implications for K, D and B Decays
• Meson Mixing Bounds on Z^′ Mass in the Alignment Limit: Establishing the Phenomenological Viability of the 331 Model
• Plan B: New Z^′ models for b→ sl⁺l^- anomalies
• Kinetic mixing, custodial symmetry, Z, Z^′ interactions and Z^′ production in hadron colliders
• Delving into the B_s → ℓ ℓ^′, B_(s) → (K^(*), ϕ, f₂^′, K₂^*) ℓ ℓ ^′ processes