Measurement of charm mixing in a CP-odd mode at Belle and its prospects at Belle II

	The observed baryon asymmetry of the universe implies the existence of particle interactions that played an important role during the early evolution of the universe and which have much more CP violation than the Standard Model. The effects of such interactions can be probed in measurements for which the Standard-Model contribution to CP violation is small. A prime candidate is the charm-quark system.  The observable y_CP parameterizes charm-mixing in D0 decays to CP eigenstates and is sensitive to CP violation in the charm system. Until recently, measurements of y_CP were conducted mostly in CP-even final states, with only one measurement in CP-odd

	final states, which assumed CP conservation. In this talk, I will present the first measurement of y_CP in a CP-odd final-state decay, D0→ KSω, allowing for CP violation. The analysis uses the full Belle data set and was recently published in Phys. Rev. D 102, 071102(R). I will alsodiscuss the prospects of y_CP measurements at Belle II with CP-odd final states.