Semileptonic & Rare Charm Decays

1. Semileptonic & Rare Charm Decays Will E. Johns Vanderbilt University FPCP 2003, June 4

2. Rare Charm Decays Box and Penguin Diagrams are Smallish for Charm Potential FCNC Decays are Suppressed No Top Quuark in the loop Short Distance 10-19 10-16 10-8

3. Rare Charm Decays Enhancement from Long Distance Effects Long Distance 10-13 10-8 10-6 Even More room for decays: Room for New Physics

4. New Result from CDF Use D* tagged Do’s Use Similar Normalization Mode Very Similar Kinematics Keep cuts “same” Blessed • Need Anyway: • Background from Normalization • ~(MISID)2 = (0.013)2 or (1/5 ev.) The “MISID ZONE” Back of the Envelope: 1.5E-3 (2.2/1371) = 2.4E-6 "Blind" Search Optimal: Sideband + (MISID)2

5. New Result from CDF • Expected background • events • Fake: • Combinatorial: • 0 events in window • New best limit Br < 2.4 x 10-6 at 90% CL Br < 3.1 x 10-6 at 95% CL Open the Box Blessed Previous Bests: 4.1 x 10-6 at 90% CL (BEATRICE) 4.2 x 10-6 at 90% CL (E771) Background Sideband (Combinatorial Estimate)

6. New Result from CLEO Form D0 mass from 2 photons (Cuts optimized on ) Mass must be within of M(D0) Veto candidate when extra photons form mass: 13.8 fb-1 (reduces bkgnd from 4 to 1) Find soft pion consistent with D momentum cuts and Particle ID Form Fit data to Gaussian and threshold function Gaussian width and center fixed from Monte Carlo

7. New Result from CLEO (stat) Systematic error 13.1% from finding efficiencies, fits, MC stats, D selection, Event selection (added in quadrature with stat error for upper limit estimate) My toy explanation 0.033 90% of Probability is above 0.0194 Sigma is total error Phys. Rev. Lett. 90:101801, 2003 hep-ex/0212045 0.0194

8. Final Results from FOCUS Look for 3 bodies with 2 muons Cut Grid, based on vertexing, Particle ID ss sp L/s – vary from >5-21 L ISO1 – CL DK’s in prim (vary <0.1 –0.001) DCL – CL of DK vertex (>1 -- 4%) MuCL – CL for Muon ID (>1 – 10%) Cuts on P(m) for m’s, Cerenkov for p’s and K’s Loosest Cuts Tightest cuts

9. Final Results from FOCUS Use Dual Bootstrap - First Bootstrap sets cuts for optimal Sensitivity (Blind) - Second Bootstrap calculates quoted Sensitivity and Branching Ratio Systematic Check uses a single cut (makes better plots!) Signal Excluded

10. Final Results from FOCUS Final Results from FOCUS (E687) Dominated by PDG rate to normalizing mode

11. Still Room for New Physics Rare Decay Round-Up A 1st ! No Lower Limits Close to Long Distance Predictions A 1st! Sets MSSM constraint MSSM Constraint Closing in on Long range SM predictions Lots of Room At the bottom!

12. Semileptonic Charm Decays More than just CKM measurement tools… Simple Equation: (D decay, No form factors, V decays to spin 0 particles) Neutrino is left handed V products spinless Prefers W spin along muon,e Prefer LZ=0 Scalar Resonance? Baryons (spin ½) Gets Complicated... CP? Form Factors

13. FOCUS saw discrepancies in the data Yikes! Phys.Lett.B535:43-51, 2002 hep-ex/0203031

14. FOCUS added a term, things got better With a Clean The data (error bars) preferred the L=0 ansatz (solid) over no extra term (dashed) L=0 ansatz And the distributions were ready for fitting Bkgnd

15. FOCUS BR Measurements Cuts similar to rare search: ISO1 ISO2 – No unused tracks consistent with charm vertex (CL < 0.1%) OoM – Charm vertex outside of target and silicon by Includes S-wave interference Phys.Lett.B540:25-32, 2002 hep-ex/0206013 events / 5 MeV/c2 (add in if > 1)

16. FOCUS Form Factors Tried in fit, no sensitivity (E791?) (common – vary generated parameters in Montecarlo by using agreement with reconstructed distributions and data) Technique: Pioneered by D.M. Schmidt for E691 K*ev analysis: NIM A 328 (1993) 1st find S-wave with PDG r's, then fit for r's S-wave term and r’s essentially decouple S-wave term Breaks symmetry

17. FOCUS Form Factors Cuts similar to previous, some change to get uniform acceptance, one extra OoM – Charm vertex outside of target and silicon by Cut on q2 < 0.2 GeV2/c2 r’s are flat, feeling mμ? Goodness of fit issue Results: • Systematic Checks • S-wave – varied cuts • 35 fits – Sample Variance • Form Factor (3 sources) • Varied Cuts • Split sample • Vary MC input • Charm Backgrounds Right sign – Wrong sign Charm Background Phys.Lett.B544:89-96, 2002 hep-ex/0207049

18. CLEO Form Factors and CP Spin ½ Λbaryon adds a new wrinkle… Körner and Krämer use supplementary definitions for X and the lepton angle One pole mass describes the decay Helicty H’s made from 2 form factors: Integrate over variables and look at asymmetries: (other choices possible) (no sign change for particle and anti-particle)

19. CLEO Form Factors and CP (To be sent to PRL) 13.4 fb-1 from CLEO II and II.5 Results: Look for Λe+ pairs where Λ→p π– • Event thrust axis for direction • Try to close kinematics: (use fragmentation to break ambg) Technique: (again the Schmidt meth) KK 4-D r and pole mass 2-D asymmetry • Systematics: • Background Normalizations • Kinematic Closing • Fitting simulation • Efficiencies

20. CLEO Form Factors and CP

21. Very Interesting! Semileptonic Round-up Interference effects Probably more in there… Need other experiments to look Lowers by 5.5% (From K. Stenson’s APS review)

22. Semileptonic Round-up We all seem to agree! No Surprises! No CP violation Expect ~-1 from HQET Good agreement in the Distributions

23. I didn’t miss ‘em! Would be nice to measure: