Measurements of branching fractions for electromagnetic transitions involving the $\chi_{bJ}(1P)$ states

Using (9.32, 5.88) million Y(2S; 3S) decays taken with the CLEO III detector, we obtain five product branching fractions for the exclusive processes Y(2S) -> gamma chi(b0,1,2)(1P) -> gamma gamma Y(1S) and Y(3S) -> gamma chi(b1,2)(1P) -> gamma gamma Y(1S). We observe the transition chi(b0)(1P) -> yY(1S) for the first time. Using the known branching fractions for B[Y2S) -> gamma chi(bJ)(1P)], we extract values for B[chi(bJ)(1P) -> gamma Y(1S)] for J = 0, 1, 2. In turn, these values can be used to unfold the Y(3S) product branching fractions to obtain values for B[Y(3S) -> gamma chi(b1,2)(1P)] for the first time individually. Comparison of these with each other and with the branching fraction B[Y(3S) -> gamma chi(b0)] previously measured by CLEO provides tests of relativistic corrections to electric dipole matrix elements.