Measurement of indirect CP-violating asymmetries in D0 → K+K and D0 → π+π decays at CDF

Primary authors: A. Di Canto, S. Leo, P. Maestro, K. Pitts, D. Tonelli

A search for indirect CP violation in D0 → K+K and D0 → π+π decays is performed using the full Run II data set, corresponding to 9.7 fb−1 of integrated luminosity and collected by the trigger on displaced tracks.

Exploiting the strong D*+ →D0 π+ decay to identify the flavor of the neutral charmed meson at production time, we measure in each decay mode the asymmetry in several decay-time bins between the numbers of charm and anticharm decays. By fitting the yield asymmetry as a function of decay time with a linear function, we measure the amount of indirect CP violation, which is linked to the effective-lifetime asymmetry AΓ, by ACPind = −AΓ.

The analysis is described in CDF Public Note 11117.

The results do not show any sign of indirect CP violation:

AΓ+π) = [-0.1 ± 1.8 (stat.) ± 0.3 (syst.)] × 10−3,
AΓ(K+K) = [-1.9 ± 1.5 (stat.) ± 0.4 (syst.)] × 10−3,

They are among the most precise measurements to date of these quantities and are compatible with those from other experiments.

Figure: yield asymmetry versus decay time with fit projections overlaid.

List of public plots

Time and flavor integrated mass distributions
Mass fit projections Impact parameter fit projections Asymmetry fits Checks Plots for paper