Search for Very High Energy Radiation from the Radio Bright Region Dr4 of the Snr G78.2+2.1

Data from the HEGRA air shower array are used to set an upper limit on the emission of-radiation above 25 (18) TeV from the direction of the radio bright region DR4 within the SNR G78.2+2.1 of 2.5 (7.1) 10 ?13 cm ?2 sec ?1. The shock front of SNR G78.2+2.1 probably recently overtook the molecular cloud Cong 8 which then acts as a target for the cosmic rays produced within the SNR, thus leading to the expectation of enhanced-radiation. Using a model of Drury, Aharonian and V olk which assumes that SNRs are the sources of galactic cosmic rays via rst order Fermi acceleration, we calculated a theoretical prediction for the-ray ux from the DR4 region and compared it with our experimental ux limit. Our`best estimate' value for the predicted ux lies a factor of about 18 above the upper limit for-ray energies above 25 TeV. Possible reasons for this discrepancy are discussed.