Photon Polarization in Radiative B Decays

We study decay distributions in B → Kππγ, combining contributions from several overlapping resonances in a Kππ mass range near 1400 MeV, 1 K1(1400), 2 K 2 (1430) and 1 − K(1410). A method is proposed for using these distributions to determine a photon polarization parameter in the effective radiative weak Hamiltonian. This parameter is measured through an up-down asymmetry of the photon direction relative to theKππ decay plane. We calculate a dominant up-down asymmetry of 0.33 ± 0.05 from the K1(1400) resonance, which can be measured with about 10 BB̄ pairs, thus providing a new test for the Standard Model and a probe for some of its extensions.