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

In the context of the recently measured non-leptonic decays Bd→$$ {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ K ∗ 0 K ¯ ∗ 0 and Bs→$$ {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ K ∗ 0 K ¯ ∗ 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→$$ {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ K ∗ 0 K ¯ ∗ 0 and Bs→$$ {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ K ∗ 0 K ¯ ∗ 0 , we discuss the main sources of hadronic uncertainty in the SM. We find for the SM prediction $$ {L}_{K^{\ast }{\overline{K}}^{\ast }}={19.5}_{-6.8}^{+9.3} $$ L K ∗ K ¯ ∗ = 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 $$ {\mathcal{C}}_4 $$ C 4 and $$ {\mathcal{C}}_{8g} $$ C 8 g 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 $$ {\mathcal{C}}_4 $$ C 4 (Kaluza-Klein gluon) or in $$ {\mathcal{C}}_{8g} $$ C 8 g , with a significant amount of fine tuning, but possible connections to the b→sℓℓ anomalies.

Strong constraints on the b → sγ photon polarisation from B0 → K*0e+e− decays

An angular analysis of the B0 → K*0e+e− decay is performed using a data sample corresponding to an integrated luminosity of 9 fb−1 of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared (q2) interval between 0.0008 and 0.257 GeV2, where the rate is dominated by the B0 → K*0γ transition with a virtual photon. The fraction of longitudinal polarisation of the K*0 meson, FL, is measured to be FL = (4.4 ± 2.6 ± 1.4)%, where the first uncertainty is statistical and the second systematic. The $$ {A}_{\mathrm{T}}^{\mathrm{Re}} $$ A T Re observable, which is related to the lepton forward-backward asymmetry, is measured to be $$ {A}_{\mathrm{T}}^{\mathrm{Re}} $$ A T Re = −0.06 ± 0.08 ± 0.02. The $$ {A}_{\mathrm{T}}^{(2)} $$ A T 2 and $$ {A}_{\mathrm{T}}^{\mathrm{Im}} $$ A T Im transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be $$ {A}_{\mathrm{T}}^{(2)} $$ A T 2 = 0.11 ± 0.10 ± 0.02 and $$ {A}_{\mathrm{T}}^{\mathrm{Im}} $$ A T Im = 0.02 ± 0.10 ± 0.01. The results are consistent with Standard Model predictions and provide the world’s best constraint on the b → sγ photon polarisation.