Measurement of branching fractions and mass sepctra in B to K pi pi gamma decays

We present a measurement of the branching fractions of the exclusive radiative penguin processes B to K pi pi gamma in a sample of 232 million e+ e- to B Bbar decays recorded by the BaBar detector at the PEP-II asymmetric-energy storage ring. We reconstruct four final states: K+ pi- pi+, K+ pi- pi0, Ks pi+ pi-, and Ks pi+ pi0, where Ks to pi+ pi-, in the range m(K pi pi) < 1.8 GeV/c^2. We measure the branching fractions BR(B+ to K+ pi- pi+ gamma) = (2.95 +- 0.13 (stat.) +- 0.19 (syst.)) x 10^-5, BR(B0 to K+ pi- pi0 gamma) = (4.07 +- 0.22 (stat.) +- 0.31 (syst.)) x 10^-5, BR(B0 to K0 pi+ pi- gamma) = (1.85 +- 0.21 (stat.) +- 0.12 (syst.)) x 10^-5, and BR(B+ to K0 pi+ pi0 gamma) = (4.56 +- 0.42 (stat.) +- 0.30 (syst.)) x 10^-5.