1. 1 Charm Results from FOCUS Kihyeon Cho Kyungpook National University Daegu, Korea (On behalf of FOCUS Collaborations) Flavor Physics CP Violation 2004 October 4 -9, 2004

2. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 2 Contents Why Charm Physics? FOCUS Experiment Recent Charm Results from FOCUS 1.Pseudoscalar semileptonic decays 2.Vector semileptonic decays 3.Charm hadronic mixing 4.Search for new particles – pentaquarks, double charm baryons Conclusions

3. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 3 Why charm physics? Window to new physics  Standard model rates for rare decays, CP violation and mixing are very low.  With current experiments, observation of CP violation, rare decays or mixing  new physics Provides information about QCD  Measurements of production characteristics, lifetimes, branching ratios and subresonant analyses provide insight into QCD. Needed for b physics  Many b particles decay to charm so branching ratios and lifetimes are needed for accurate b results.  Experimental techniques are developed in charm physics. (lifetime measurement, Dalitz plot analyses...)  Heavy quark effective theory often needs charm to bootstrap to b physics.

4. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 4 Pho toproduction of C harm with an U pgraded S pectrometer ~100 Physicists, 18 institutes from 5 countries Univ. of California-Davis, CBPF-Rio de Janeiro, CINVESTAV-Mexico City, Univ. Colorado-Boulder, FERMILAB, Laboratori Nazionali di Frascati, Univ. of Illinois-Urbana-Champaign, Indiana Univ.-Bloomington, Korea Univ.-Seoul, Kyungpook National Univ.-Daegu, INFN and Univ.-Milano, Univ. of North Carolina-Asheville, INFN and Univ.-Pavia, Univ. of Puerto Rico-Mayaguez, Univ. of South Carolina-Columbia, Univ. of Tennessee-Knoxville, Vanderbilt Univ.-Nashville, Univ. of Wisconsin-Madison FOCUS Experiment

5. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 5 Vertexing is the Key Golden Modes: D +  K -     D 0  K -   D 0  K -       BeO tarsil | primary vtx | secondary vtx Decays / 200  m BackgroundSubtracted Golden Mode Charm

6. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 6 1.Pseudoscalar semileptonic decay Using D 0      D 0       (D 0      (  D 0       Pole masses  f - (0)/f + (0)  f +  (0)/f + K (0)  Non-parametric q 2 dependent

7. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 7 Why Pseudoscalar semileptonic decay? The differential decay rate is Measuring the q 2 dependence and form factors in heavy quark transition is critical to our understanding of QCD. Hadronic current contains information about strong contributions.

8. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 8 What do we measure in D 0  Pl   (D 0      (  D 0      Pole masses f - (0)/f + (0) f +  (0)/f + K (0)  provides the test of SU(3) symmetry breaking Non-parametric q 2 dependent  A model independent measurement would allow to discriminate between different models. f + (q 2 ) parameter Pole form Modified pole from

9. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 9 Fitting Technique on D 0         Fitting Technique on D 0         Fit D*-D 0 mass difference plot to find the amount of combinatoric background. Apply the mass difference cut (< 0.154 GeV/c 2 ) to suppress combinatoric and peaking background

10. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 10 Results on D 0         Results on D 0         Fit to cos  l and q 2 to measure branching ratio, pole masses and the ratio f - (0)/f + (0). 288  29 6574  92 Preliminary (GeV/c 2 ),

11. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 11 Extracting f +  (0)/f + K (0) Compute a numerical integration on Dalitz Get efficiency as a function of q 2 Get yield from the fit Using PDG |V cd /V cs | 2 =0.051  Consistent with the predictions from SU(3) symmetry breaking and lattice QCD Preliminary

12. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 12 Non-parametric q 2 dependent  e Ke form factor f + (q²) single-pole model Based on 820 events q² / GeV² Kl  l q² / GeV² Using ~13,000 K  events D 0  l  / Kl 3 brand new results from CLEO, Belle and FOCUS on form factor f + (q²) in D 0  l  / Kl f + (q²) Excellent agreement with LQCD! Preliminary

13. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 13 Summary for pseudoscalar semileptonic decay The  and  branching ratio is consistent with recent results from CLEO. The pole masses are lower than the predicted value at the D* or D s * masses. We presented a non-parametric analysis of the q 2 dependence for D 0  K  which shows excellent agreement with the results obtained with the parametric analysis and lattice QCD. Preliminary,(GeV/c 2 )

14. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 14 2. Vector Semileptonic decay D +  K *0    form factor Branching ratio D 0  K *-    form factor Branching ratio

15. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS  (D +  K *0    /  D +  K 0   ) Use upstream K s (~10%) so that both the signal (K  ) and normalization (K s  ) leave 3 tracks in FOCUS microstrip Theory S-wave corrected Old quark model PLB 598 (2004) 33

16. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 16 Form Factors of D 0  K *-  + Form Factors of D 0  K *-  + K* -  Ks  - After background subtraction, we fit D*-D 0 mass difference and cos  l X cos  v X q 2 distribution at the same time. Results  R V = 1.706  0.677  0.342  R 2 = 0.912  0.370  0.104  World’s first measurement Preliminary

17. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 17 Summary of vector semilepotonic decay Form Factor FOCUS D 0  K *-  + FOCUS D +  K *0   RvRv 1.706  0.677  0.3421.504  0.057  0.039 R2R2 0.912  0.370  0.1040.875  0.049  0.064 ReferencePreliminary PLB 544 (2002) 89 PLB 598 (2004) 33 Preliminary

18. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 18 3. D 0 -D 0 hadronic mixing and DCS decays D 0 goes to K +  - in two ways (mixing + CF decay and DCS decay)  Interference Assuming CP conservation, D 0  K +  - wrong sign to right sign decay ratio is written by Three terms from DCS decays, interference & mixing Soft pion charge in D* +  D 0  + defines right sign(RS) and wrong sign(WS). Fit for R DCS, x’ 2 and y’ Mixing parameters

19. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 19 Right Sign vs Wrong Sign

20. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 20 Summary for Mixing Results All results shown here assume CP conservation. FOCUS results agree better with BaBar in location and shape than CLEO.

21. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 21 4. New particle searches S=-1 pentaquark  (1540) + with uudds S=-2 pentaquark  (1860) – – with uddss Charm pentaquark  c (3100) 0 with uuddc Double charm baryons  cc with ccu and ccd

22. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 22 Evidence for  + (uudds)

23. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 23 Evidence for  + (cont’d)

24. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 24  (1540) + p Ks search  (1540) +  p Ks search No evidence for  (1540) +  pKs but reconstructs 8 million K*(892) +  Ks  + and 240,000  (1385) +   0  +

25. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 25  (1860) – – search  (1860) - -   -  - (S=-2 pentaquark) NA49 shows evidence for  (1860) - - and  (1860) 0 decaying  -  .. No evidence for  (1860) - -   -  - but reconstructs 60,000  (1530) 0   -  +, approximately 1,000 times more than observing experiment.

26. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 26 Charm Pentaquark search No evidence for a charm pentaquark decaying to D* - p or D - p with a factor of 10 more D* + decays than the observing experiment.

27. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 27  CC search No evidence

28. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 28 Summary for Search Results No evidence for  (1540) +  pKs but reconstructs 8 million K*(892) +  Ks  + and 240,000  (1385) +   0   No evidence for  (1860) - -   -  - but reconstructs 60,000  (1530) 0   -  +, approximately 1,000 times more than observing experiment No evidence for a charm pentaquark decaying to D* - p or D - p with a factor of 10 more D* + decays than the observing experiment. No evidence for double charm baryons with 10 times more  C decays than the observing experiment.

29. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 29 Conclusions Charm mode … Charm physics gives a rich source of new results. FOCUS is playing a major role in understanding the charm decays. The recent charm results from FOCUS include  Charm pseudoscalar semileptonic decays  Charm vector semileptonic decays  Charm hadronic mixing  Search for pentaquarks and double charm. FOCUS is continuing studies of charm physics.

30. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 30 Backups

31. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 31 FOCUS Spectrometer At Fermilab   BeO charm  Segmented target Silicon vertexing MWPC tracking ~175 GeV Cenenkov ID EM/hadronic Calorimeter Muon detectors

32. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 32 Kl 1.91  0.04 q 2 dependent (cont’d) Clearly the data does not favor the simple Ds* pole We presented a non-parameteric analysis of the q 2 dependence for D 0  K  which shows excellent agreement with the results obtained with the parameteric analysis and lattice QCD.

33. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 33 D +  K *0    channel Only external diagram involved. Factorization is possible between hadronic and leptonic current.

34. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 34 H 0 (q 2 ), H + (q 2 ), H - (q 2 ) are helicity-basis form factors computable by LQCD right-handed  + left-handed  + Two amplitudes get summed over W polarization using D-matrices Helicity FF are combinations of one vector and two axial form factors. Two observables parameterize the decay  Four body decays requires five variables: 3 angles, M k , q. D +  K *0    decays

35. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 35 Yield 31,254 Data MC Focus “ K* ” signal matches model -15% F-B asymmetry! Interference in D +  K *0   Interference in D +  K *0    Huge Asymmetry in cos  v below K* pole led to a discovery of s- wave interference.

36. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 36 K * interference term (Ae i  ) S-wave interference term Signal events weighted by avg(cos  V ): No added term PLB535(2002) 43

37. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 37 S-Wave effects apparent only with high statistics Lattice Gauge! Experiment Models PLB544(2002) 89 Form Factors D +  K *0 l  Form Factors D +  K *0 l   A=0.330  0.022  0.015GeV -1     =0.68  0.07  0.05 rad  R V = 1.504  0.057  0.039  R 2 = 0.875  0.049  0.064

38. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 38 D 0  K *-  + channel

39. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 39 K * interference term (Ae i  ) A term which is non- symmetric vs. cos  v appears due to the S-wave Use a model that includes S- wave   = 0.68 rad fixed from  A=0.347  0.222  0.053 GeV -1

40. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 40 Branching Ratio D*-D mass difference plot for normalization mode Accounting for S-wave component in Normalization mode  Excellent agreement with semielectronic decay

41. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 41 Summary of vector semilepotonic decay FOCUS D 0 FOCUS D + RvRv 1.706  0.677  0.3421.504  0.057  0.039 R2R2 0.912  0.370  0.1040.875  0.049  0.064 A(GeV -1 ) 0.347  0.222  0.0530.330  0.022  0.015   (rad) 0.68 (fixed) 0.68  0.07  0.05 ReferencePreliminary PLB 544 (2002) 89 PLB 598 (2004) 33 Preliminary

42. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 42  Fit Shape (Signal)

43. KIHYEON CHO CENTER FOR HIGH ENERGY PHYSICS 43 Double charm baryon production compared If the  C + K -  + (  C K -  +  + ) signal is real, SELEX produces at least 42 (111) times more  cc baryons relative to  C than FOCUS.