Angular Analysis of B → K^* E^+ E^- in the Low-Q^2 Region with New Electron Identification at Belle

We perform an angular analysis of the B→ K^* e^+ e^- decay for the dielectron mass squared, q^2, range of 0.0008 to 1.1200 GeV^2 /c^4 using the full Belle data set in the K^*0→ K^+ π^- and K^*+→ K_S^0 π^+ channels, incorporating new methods of electron identification to improve the statistical power of the data set. This analysis is sensitive to contributions from right-handed currents from physics beyond the Standard Model by constraining the Wilson coefficients 𝒞_7^('). We perform a fit to the B→ K^* e^+ e^- differential decay rate and measure the imaginary component of the transversality amplitude to be A_T^ Im = -1.27 ± 0.52 ± 0.12, and the K^* transverse asymmetry to be A_T^(2) = 0.52 ± 0.53 ± 0.11, with F_L and A_T^ Re fixed to the Standard Model values. The resulting constraints on the value of 𝒞_7^' are consistent with the Standard Model within a 2σ confidence interval.