On the Interplay of Constraints from $B_s$, $D$, and $K$ Meson Mixing in $Z^\prime$ Models with Implications for $b\to s ν\barν$ Transitions
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2024
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| author | Buras, Andrzej J. Stangl, Peter |
| author_facet | Buras, Andrzej J. Stangl, Peter |
| contents | Within $Z^\prime$ 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 $Z^\prime$ parameter space, the contributions to meson mixing observables become negligibly small even for large $Z^\prime$ couplings. While this a priori allows for significant new physics (NP) effects in FCNC decays, we discuss how large $Z^\prime$ couplings in one neutral meson sector can generate effects in meson mixing observables of other neutral mesons, through correlations stemming from $\text{SU(2)}_L$ gauge invariance and through Renormalization Group (RG) effects in the SM Effective Field Theory (SMEFT). This is illustrated with the example of $B_s^0-\bar B_s^0$ mixing, which in the presence of both left- and right-handed $Z^\prime bs$ couplings $Δ_L^{bs}$ and $Δ_R^{bs}$ remains SM-like for $Δ_R^{bs}\approx 0.1\,Δ_L^{bs}$. We show that in this case, large $Z^\prime bs$ 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 $b\to s\ell^+\ell^-$ experimental data without violating other constraints like $e^+ e^-\to\ell^+\ell^-$ scattering. Assuming LFU, invariance under the $\text{SU(2)}_L$ gauge symmetry leads then to correlated effects in $b\to sν\barν$ observables presently studied intensively by the Belle II experiment, which allow to probe the $Z^\prime$ parameter space that is opened up by the vanishing NP contributions to $B_s^0-\bar B_s^0$ mixing. In this scenario the suppression of $B\to K(K^*)μ^+μ^-$ branching ratios implies uniquely enhancements of $B\to K(K^*)ν\barν$ branching ratios up to $20\%$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2412_14254 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | On the Interplay of Constraints from $B_s$, $D$, and $K$ Meson Mixing in $Z^\prime$ Models with Implications for $b\to s ν\barν$ Transitions Buras, Andrzej J. Stangl, Peter High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Lattice Within $Z^\prime$ 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 $Z^\prime$ parameter space, the contributions to meson mixing observables become negligibly small even for large $Z^\prime$ couplings. While this a priori allows for significant new physics (NP) effects in FCNC decays, we discuss how large $Z^\prime$ couplings in one neutral meson sector can generate effects in meson mixing observables of other neutral mesons, through correlations stemming from $\text{SU(2)}_L$ gauge invariance and through Renormalization Group (RG) effects in the SM Effective Field Theory (SMEFT). This is illustrated with the example of $B_s^0-\bar B_s^0$ mixing, which in the presence of both left- and right-handed $Z^\prime bs$ couplings $Δ_L^{bs}$ and $Δ_R^{bs}$ remains SM-like for $Δ_R^{bs}\approx 0.1\,Δ_L^{bs}$. We show that in this case, large $Z^\prime bs$ 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 $b\to s\ell^+\ell^-$ experimental data without violating other constraints like $e^+ e^-\to\ell^+\ell^-$ scattering. Assuming LFU, invariance under the $\text{SU(2)}_L$ gauge symmetry leads then to correlated effects in $b\to sν\barν$ observables presently studied intensively by the Belle II experiment, which allow to probe the $Z^\prime$ parameter space that is opened up by the vanishing NP contributions to $B_s^0-\bar B_s^0$ mixing. In this scenario the suppression of $B\to K(K^*)μ^+μ^-$ branching ratios implies uniquely enhancements of $B\to K(K^*)ν\barν$ branching ratios up to $20\%$. |
| title | On the Interplay of Constraints from $B_s$, $D$, and $K$ Meson Mixing in $Z^\prime$ Models with Implications for $b\to s ν\barν$ Transitions |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Lattice |
| url | https://arxiv.org/abs/2412.14254 |