D-0(D)over-bar-(0) oscillations as a probe of quark-hadron duality

It is usually argued that the Standard Model predicts slow D-0-(D) over bar (0) oscillations with DeltaM(D), Delta Gamma (D) less than or equal to 10(-3) Gamma (D) and that New Physics can reveal itself through DeltaM(D) exceeding 10(-3) Gamma (D). It is believed that the bulk of the effect is due to long distance dynamics that cannot be described at the quark level. We point out that in general the OPE yields soft GIM suppression scaling only like (m(s)/mu (hadr))(2) and even like m(s)/mu (hadr) rather than m(s)(4)/m(c)(4) of the simple quark box diagram. Such contributions can actually yield DeltaM(D), Delta Gamma (D) similar to O(10(-3))Gamma (D) without invoking additional long distance effects. They are reasonably suppressed as long as the OPE and local duality are qualitatively applicable in the 1/m(c) expansion. We stress the importance of improving the sensitivity on Delta Gamma (D) as well as DeltaM(D) in a dedicated fashion as a laboratory for analyzing the onset of quark-hadron duality and comment on the recent preliminary study on Delta Gamma (D) by the FOCUS group. (C) 2001 Elsevier Science B.V. All rights reserved.