Impact of B→K0⁎ℓ+ℓ− on the New Physics search in B→K⁎ℓ+ℓ−B→K⁎ℓ+ℓ− decay

We discuss the uncertainty related to the amount of unwanted B→K0⁎(Kπ)ℓ+ℓ− events in the sample of B→K⁎(Kπ)ℓ+ℓ−B→K⁎(Kπ)ℓ+ℓ− ones. Those events can increase the measured differential decay rate by up to 10%10% in the low q2q2 region, and can be a source of non-negligible uncertainty in the full angular distribution of the B→K⁎(Kπ)ℓ+ℓ−B→K⁎(Kπ)ℓ+ℓ− decay. Although the transverse asymmetries should be unaffected by the presence of the S-wave Kπ   pairs, coming from the scalar K0⁎ meson, we show that in practice, their normalization might be sensitive to those events and could entail a sizable uncertainty in transverse asymmetries around q2=2 GeV2q2=2 GeV2. For other q2q2ʼs that error is under 10%.