On the interplay of constraints from $$B_{s},$$ B s , D, and K meson mixing in $$Z^\prime $$ Z ′ models with implications for $$b\!\rightarrow \! s \nu {\bar{\nu }}$$ b → s ν ν ¯ transitions
Abstract Within $$Z^\prime $$ 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 $$Z^\prime $$ Z ′ parameter space, the contributions to meson mixing observables become n...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2025-05-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | https://doi.org/10.1140/epjc/s10052-025-14168-z |
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| Summary: | Abstract Within $$Z^\prime $$ 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 $$Z^\prime $$ Z ′ parameter space, the contributions to meson mixing observables become negligibly small even for large $$Z^\prime $$ Z ′ couplings. While this a priori allows for significant new physics (NP) effects in FCNC decays, we discuss how large $$Z^\prime $$ Z ′ couplings in one neutral meson sector can generate effects in meson mixing observables of other neutral mesons, through correlations stemming from $${\text {SU}(2)}_L$$ 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 $$B_s^0-{\bar{B}}_s^0$$ B s 0 - B ¯ s 0 mixing, which in the presence of both left- and right-handed $$Z^\prime bs$$ Z ′ b s couplings $$\Delta _L^{bs}$$ Δ L bs and $$\Delta _R^{bs}$$ Δ R bs remains SM-like for $$\Delta _R^{bs}\approx 0.1\,\Delta _L^{bs}.$$ Δ R bs ≈ 0.1 Δ L bs . We show that in this case, large $$Z^\prime bs$$ Z ′ b s couplings generate effects in D and K meson mixing observables, but that the D and K mixing constraints and the relation between $$\Delta _R^{bs}$$ Δ R bs and $$\Delta _L^{bs}$$ Δ L bs are fully compatible with a lepton flavour universality (LFU) conserving explanation of the most recent $$b\rightarrow s\ell ^+\ell ^-$$ b → s ℓ + ℓ - experimental data without violating other constraints like $$e^+ e^-\rightarrow \ell ^+\ell ^-$$ e + e - → ℓ + ℓ - scattering. Assuming LFU, invariance under the $${\text {SU}(2)}_L$$ SU ( 2 ) L gauge symmetry leads then to correlated effects in $$b\rightarrow s\nu {\bar{\nu }}$$ b → s ν ν ¯ observables presently studied intensively by the Belle II experiment, which allow to probe the $$Z^\prime $$ Z ′ parameter space that is opened up by the vanishing NP contributions to $$B_s^0-{\bar{B}}_s^0$$ B s 0 - B ¯ s 0 mixing. In this scenario the suppression of $$B\rightarrow K(K^*)\mu ^+\mu ^-$$ B → K ( K ∗ ) μ + μ - branching ratios implies uniquely enhancements of $$B\rightarrow K(K^*)\nu {\bar{\nu }}$$ B → K ( K ∗ ) ν ν ¯ branching ratios up to $$20\%.$$ 20 % . |
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| ISSN: | 1434-6052 |