Measuring the Photon Helicity in Radiative B Decays

We propose a way of measuring the photon helicity in radiative B decays into excited kaons, which can test the Standard Model and probe new physics. In B → K 2(1430)γ and B → K1(1400)γ, where excited kaons are observed in Kππ channels, the photon helicity is shown to be measured by the up-down asymmetry of the photon direction relative to the K resonance decay plane in the resonance rest frame. Assuming B(B → K1(1400)γ) = 0.7×10−5, this measurement is estimated to require a total of 8×107 charged and neutral BB̄ pairs, and is feasible at currently operating B factories. Present Address: Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309 USA.