Abstract
Recent studies of several multi-body D0 meson decays have revealed that the final states are dominantly CP-even. However, the small value of the width difference between the two physical eigenstates of the D0–D‾0 system indicates that the total widths of decays to CP-even and CP-odd final states should be the same to within about a percent. The known contributions to the width difference from hadronic D0 decays are discussed, and it is shown that an apparent excess of quasi-CP-even modes is balanced, within current uncertainty, by interference effects in quasi-flavour-specific decays. Decay modes which may significantly affect the picture with improved measurements are considered.
Highlights
Oscillations between the flavour eigenstates of the neutral D meson result in physical states with distinct masses and widths
The Particle Data Group reports that (38.2 ± 1.4) % of D0 decays are as-yet unaccounted for, this indicates that these missing modes either have low values of 2F+ − 1, or that there is a balance between net CP -even and CP -odd modes leading to the low value of Eq (9). (For comparison, the modes included in Tables 1 and 2 account for about 40 % of the total D0 width – the remainder are predominantly from semileptonic decays.)
There is a significant body of results from studies of various hadronic D meson decays, including determinations of net CP content, coherence factors and parameters related to strong phase differences
Summary
Oscillations between the flavour eigenstates of the neutral D meson result in physical states with distinct masses and widths. In Eq (3) the widths and branching fractions to CP -even and CP -odd states include decays to CP eigenstates, but any decays with net CP content [2]. Where the notation yDB−qCP indicates that this value is determined from the experimental knowledge of the branching fractions of decays to quasi-CP eigenstates only. It is not a true estimate of yD as there are additional modes, including those discussed in Secs. Note that the uncertainty on yDB−qCP is dominated by the least precisely measured modes, with the largest contributions coming from uncertainties on the branching fractions of D decays to KS0π0π0 and KS0ηπ0 final states. If all such modes containing K0 mesons in the final state are excluded from the calculation of yDB−qCP , a larger value of (14.7 ± 0.5)×10−3 is obtained
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