Paper detail

The β-term for D^* --> D γwithin a heavy-light chiral quark model

We present a calculation of the β-term for D^* --> D gamma within a heavy-light chiral quark model. Within the model, soft gluon effects in terms of the gluon condensate with lowest dimension are included. Also, calculations of 1/m_c corrections are performed. We find that the value of βis rather sensitive to the constituent quark mass compared to other quantities calculated within the same model. Also, to obtain a value close to the experimental value, one has to choose a constituent light quark mass larger than for other quantities studied in previous papers. For a light quark mass in the range 250 to 300 MeV and a quark condensate in the range -(250-270 MeV)^3 we find the value (2.5 +- 0.6) GeV^-1. This value is in agreement with the value of βextracted from experiment 2.7 +- 0.2 GeV^-1.