Figure 1
APS/Alan Stonebraker

Figure 1: (a)—(c) show how the charges of the π mesons from the D* and the D decay can be used to tag the D “flavor” (D0 or D̅ 0) at production and decay. In a right-sign (RS) decay the charges match [see (a)], unlike in wrong-sign (WS) decays, for which there are two possible sources [see (b),(c)]. (d) displays the weak interaction process responsible for D0-D̅ 0 oscillations, which involves all three generations of quarks.