D0–D̄0 oscillations as a probe of quark–hadron duality

It is usually argued that the Standard Model predicts slow D0–D̄0 oscillations with ΔMD, ΔΓD⩽10−3ΓD and that New Physics can reveal itself through ΔMD exceeding 10−3ΓD. 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 (ms/μhadr)2 and even like ms/μhadr rather than ms4/mc4 of the simple quark box diagram. Such contributions can actually yield ΔMD, ΔΓD∼O(10−3)ΓD without invoking additional long distance effects. They are reasonably suppressed as long as the OPE and local duality are qualitatively applicable in the 1/mc expansion. We stress the importance of improving the sensitivity on ΔΓD as well as ΔMD in a dedicated fashion as a laboratory for analyzing the onset of quark–hadron duality and comment on the recent preliminary study on ΔΓD by the FOCUS group.