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A new B-flavour anomaly in Bd,s\( {K}^{\ast 0}{\overline{K}}^{\ast 0} \): anatomy and interpretation

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In the context of the recently measured non-leptonic decays Bd \( {K}^{\ast 0}{\overline{K}}^{\ast 0} \) and Bs \( {K}^{\ast 0}{\overline{K}}^{\ast 0} \) we analyse the anatomy of the LVV observable that compares the longitudinal components of Bs VV and Bd VV decays. This observable is cleaner than the longitudinal polarisation fraction as it is afflicted only at subleading order in a 1/mb expansion by the theoretical uncertainties arising in the transverse components entering the polarisation fraction. Focusing on the particular case of Bd \( {K}^{\ast 0}{\overline{K}}^{\ast 0} \) and Bs \( {K}^{\ast 0}{\overline{K}}^{\ast 0} \), we discuss the main sources of hadronic uncertainty in the SM. We find for the SM prediction \( {L}_{K^{\ast }{\overline{K}}^{\ast }}={19.5}_{-6.8}^{+9.3} \), which implies a 2.6σ tension with respect to the most recent data, pointing to a deficit in the b s transition of the non-leptonic decay versus the corresponding b d transition. We discuss possible New Physics explanations for this deviation, first at the level of the Weak Effective Theory and we identify that the two Wilson coefficients \( {\mathcal{C}}_4 \) and \( {\mathcal{C}}_{8g} \) can play a central role in explaining this anomaly. Finally, we briefly explore two different simplified New Physics models which can explain the anomaly through a contribution either in \( {\mathcal{C}}_4 \) (Kaluza-Klein gluon) or in \( {\mathcal{C}}_{8g} \), with a significant amount of fine tuning, but possible connections to the b sℓℓ anomalies.


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Correspondence to Marcel Algueró.

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Algueró, M., Crivellin, A., Descotes-Genon, S. et al. A new B-flavour anomaly in Bd,s\( {K}^{\ast 0}{\overline{K}}^{\ast 0} \): anatomy and interpretation. J. High Energ. Phys. 2021, 66 (2021).

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  • Effective Field Theories
  • Heavy Quark Physics