Do - Do Mixing and CP Violation: Experimental Projections for a T-Charm Factory t

153 Introduction This report presents the results of a set of feasability'studies for observing Do-go mixing and CP violation in the proposed high luminosity r-charm factory. These studies are not yet complete, but clear general conclusions can already be drawn. In particular, a year of running with 1O33 luminosity would allow observation of Do-Do mixing at the level of IO-" to 10V5, consistent with standard model expectations, while CP violation in the D system could be probed at the 10L2 level. Do-D Mixing The usual problem encountered in the attempt to measure Do-0' mixing is that one is forced to choose between two experimental signatures: ('iJ the unambiguous signature presented by the observation of semileptonic decays such as Do 4 Se-v which are usuall) complicated by the lack of a definite mass peak in the presence of plentiful backgrounds , or (ii) the ambiguous signature provided by hadronic decays such as Do-+ K+T-in which the mass peak provides a clean identifiable signal, but potential mixing must be distinguished from the expected doubly Cabibbo suppressed decays (DCSD). Unfortunately the DCSD are expected to occur at a rate , relative to the corresponding Cabibbo favored mode of the order of tan48 c M 3 x 10e3, which is larger than the rate for Do-go mixing expected from the standard model " ' Fermilab experiment E-691 " I chose to search for Do-Do mixing by measuring the hadronic modes Do + K-n+ or Do t K-7r+a+n-. They distinguish the mixing and DCSD components to these decays by measuring the time evolution of the process. For example, the time dependence for the rate for Do + K+T-is given by: (lZj)2 (x2 $ y2) $ (pK, 1' tan 48c Rate (DO(t)-f K'r-) M emr2 + y It tan " 8, Re (E p,,)-2 l? t tan'B, Im (e p,,) I where the DCSD amplitude is contained in the factor PK~ defined as: 1.0 tan'@, and the mixing is characterized by z and y which are defined in terms of the mass and width 153 differences of the flavor and mass eigenstates of the Do as follows: Am 5f-r It is seen from the above that the ratio of Do-D mixing rate to that from DCSD is proportional to t 2, leading to a relative enhancement of mixing at large decay times. In this experiment, Do's from the decay of D*'s are observed via the reaction:(right …