Study of the reaction. pi. /sup -/ + /sup 12/C. -->. pi. /sup -/ + /sup 12/C* (4. 44 MeV) at 4. 5 GeV/c. [Angular distribution, electric quadrupole transition, polarization, density matrix elements, cross sections]

Characteristic 4.44-MeV ..gamma.. rays from the first excited state of carbon were observed in coincidence with scattered 4.5-GeV/c ..pi../sup -/ mesons in counters and wire spark chambers. The ..gamma..-ray angular distribution in the momentum-transfer frame confirms the electric quadrupole nature of the transition and reveals the polarization of the recoiling /sup 12/C* nucleus so that density matrix elements can be determined. A simple model with no adjustable parameters, which employs the distorted-wave impulse approximation and uses electron scattering data to obtain the nuclear transition matrix elements, predicts the angular distribution of the pions and the polarization of the /sup 12/C* recoils very well. However, the absolute values of the measured cross sections are only half as large as the predicted ones. (AIP)