Recent Charm Results From CLEO

1. Searches for D0-D0 mixing D0 -> K0sp+p- D0->K*+l-n Conclusions Recent Charm Results From CLEO Alex Smith University of Minnesota

2. 1) Large |x| 2) |x| >> |y| 3) CP violation of any kind

3. D0 – D0 Mixing Analyses: Preliminaries Complication: Strong phase ds due to final state interactions: Use D0’s from D* decays to tag flavor of D0 D*+ D0p+ x and y are what we really want Categorize D0 decays according to flavor of D0 and of K: “Right sign (RS)”: “Wrong sign (WS)”: Cabibbo-favored (CF) decays x, y, or doubly Cabibbo-suppressed decays (DCSD)

4. Recent Experiments: CLEO, FOCUS, Belle, BaBar, E791 Current Status of D0-D0 Mixing Recent Predictions: = x = y = non-SM (|x|, |y|, etc.) (1/2|Amplitude|2)

5. Measure x and y rather than x’2 and y’ • RS and WS occupy the SAME Dalitz plot: • First measurement of relative strong phase between D0 and D0 to to K0sp+p- final state • Only mode with sensitivity to sign of x! • Doubly-Cabibbo-suppressed modes • Comparable sensitivity to y as CP eigenstate (eg., D0->K+K-) analyses • Better scaling of sensitivity to x with int. luminosity than D0->K+p- analysis • Low backgrounds ~1%! • ~Flat efficiency in e+e- collisions Motivation to Study D0->Ks0p+p-

6. Visualize as pseudo-two-body decay: D0->Ks0p+p-: Dalitz Formalism Amplitude for each resonance given by a relativistic Breit-Wigner, with angular distribution determined by J. For J = 1 we have: Total amplitude is the sum with a complex coefficient: We consider 18 resonant and non-resonant decay modes:

7. Contributions to the Dalitz Plot f2(1270) K*(1680)- w K*+ r0(1700)/ r0(1450) f0(1370) K2(1430)- r0 K0(1430)- K*- f0(980) K0(1430)+

8. Fit Result Dalitz Plot Data

9. Results of Dalitz Plot Fit

10. D0->Ks0p+p- Summary • First observation (4.5s) of WS D0->K0p+p- • We observe 5 new submodes (10 total) of this decay • First measurement of strong phase shift ds between D0->K0p+p- and D0->K0p+p- = (-3 +/- 14)0 • Time-dependent analysis can measure sign of x (coming soon!) • This is the best mode in which to search for mixing: • y is likely to be comparable to or larger than x => must measure strong phase

11. D0->K*+e-n • Reconstruct K*+ in Ks0p+, Ks0-> p+ p- mode • Advantages of this mode: • Only mixing contributes to WS signal • Distinct proper time distribution of mixing: t2e-t • K* mass cut rejects backgrounds • Drawbacks of this mode: • Low momentum tracks due to pppen final state • Soft e momentum due to forward neutrino favored by V – A coupling • Must “pseudo-reconstruct” the undetected neutrino • Only sensitive to x

12. D0->K*+e-n: Fit to the “Right-sign” Data Distributions from Monte Carlo

13. D0->K*+e-n: Fit to the “Wrong-signed” Data Fit distributions from Monte Carlo

14. D0->K*+e-n • Systematic uncertainties: • Signal and background shapes • MC Statistics • Resolution and background parameters • Differences in RS and WS efficiencies • Results to be combined with D0->K+l-n analysis • Comparable sensitivity

15. Other CLEO Charm Analyses in Progress:

16. D0->K0p+p-: Summary • First observation (4.5s statistical significance) of DCSD D0->K0p+p- (prelim.) • We observe 5 new submodes of this decay • First measurement of strong phase shift ds between D0->K0p+p- and D0->K0p+p- = (-3 +/- 14)0 (prelim.) • First analysis that can measure sign of x (coming soon!) • Best channel in which to search for mixing D0->K*+l-n:

17. Mass eigenstates are also eigenstates of CP: D0->Ks0p+p-: Time Evolution of the Dalitz Plot Time evolution is given by: Evaluating <f | D1> and <f | D2>, collecting terms with similar time-dependence, and squaring the amplitude gives: • CP-even and CP-odd intermediate states provide sensitivity to G1 and G2, thus y • Sensitivity to sign of x = DM/G through sin term in |M|2 • Interference between Cabibbo-favored and DCSD may enhance sensitivity to x