  The coherence factor and average strong phase difference of D0 and D0bar
decay amplitudes to the same final state play an important role in the
precision determination of the CKM parameter gamma using B- -> DK- and related
decay modes. So far, this important input from the charm sector could only be
obtained from measurements based on quantum-correlated DDbar pairs produced at
the charm threshold. We propose to constrain these parameters using charm
mixing, using the large charm samples available at the B factories and LHCb. We
demonstrate for the example of D0->Kpipipi that a substantial improvement in
the precision of the coherence factor and average strong phase difference can
be obtained with this method, using existing data.
