1. Oct., 2006 1  Overview of the CLEO experiment  D and D S leptonic decays to  and  : Measurements of absolute branching fractions Measurements of absolute decay constants  Comparison with theory (LQCD) Victor Pavlunin on behalf of the CLEO collaboration DPF-2006

2. Oct., 2006 2 The CLEO detector  The CLEO detector was developed for B physics at the Y (4S). CLEO-III configuration: B-field: 1.5 T Gas (drift chamber): He and C 3 H 8 Tracking: 93% of 4 ,  P/P  0.6% for a 1.0 GeV track Hadron particle ID: RICH (80% of 4  ) and dE/dx E/M crystal calorimeter: 93% of 4π,  E/E  2.0% (4.0)% for a 1.0 GeV (100 MeV) photon Muon prop. chambers at 3, 5 and 7 I.  Transition from CLEO III to CLEO-c: B-field: 1.5 T  1.0 T Silicon vertex detector  low mass stereo drift chamber  Advantages of running at the  (3770) for charm physics: Pure DD, no additional particles  [ DD at  (3770)] = 6.4 nb [  (cc) at Y (4S) ~1.3 nb] Low mulitplicity, high tagging efficiency (>20%) An event taken at  the Y (4S) 6-layer all-stereo

3. Oct., 2006 3 The main task of the CLEO-c open charm program: Calibrate and Validate Lattice QCD  Help heavy flavor physics constrain the CKM matrix now : Precision tests of the Standard Model or Discovery of new physics beyond the SM in b or c quark decays Difficulty: hadronic uncertainties complicate the interpretation of exp. results:  Help LHC search for and interpret new physics if new physics is strongly coupled in the future Why a Charm Factory? Reduce theory error on B form factors and B decay constants using tested LQCD

4. Oct., 2006 4  Leptonic decays ( D +  and D s  ):  Semileptonic decays ( D   e, D  Ke ):  Combination of leptonic and semileptonic decays: Examples of LQCD tests and their impact BdBd BdBd LQCD Experiment Known to  1% from the CKM unitarity Lattice predicts f B /f D and f B /f Bs with small errors  precise f D gives precise f B and |V td |; f D /f Ds checks f B /f Bs and allows precise |V td |/|V ts | |V CKM | 2 |f D | 2 D |f(q 2 )| 2 |V CKM | 2 D Test LCQD calculations of f + (q 2 ) in the D system and apply them to the B system for |V ub | and |V cb | The topic of the next CLEO talk Test LQCD with no errors from CKM couplings )(K  The main topic of this talk

5. Oct., 2006 5 CLEO-c Data Samples Results presented in this talk were obtained using the following data samples:   (3770): total luminosity = ~ 280 pb  1  E CM = 4170 MeV: total luminosity = ~ 200 pb  1 CLEO scanned E CM = 3.97 – 4.26 GeV: Optimal energy for D s physics: E CM = 4.170 GeV Dominant production mechanism:  [Additional 120 pb -1 at E CM = 4170 MeV already collected: to be analyzed] DATA Preliminary

6. Oct., 2006 6 D (s) Leptonic Decays  Standard Model predicts: D decays: D s decays:  Use V cd and V cs to extract f D and f D s, and compare them to theory

7. Oct., 2006 7 D +   and D +   at the  (3770) References: PRL 95, 25801 (2005) PRD 73, 112005 (2006)

8. Oct., 2006 8 Tagging at the  (3770)  The  (3770) is about 40 MeV above the DD pair threshold ( )  Variables used in the tag reconstruction:  Leptonic decays are identified using missing mass squared: Tagging creates a beam of D mesons with known momentum

9. Oct., 2006 9 D  Tags DATA (280/pb) All 6 modes Cut on  E and fit M BC: Total number of tags: [158.4  0.5 (stat)]  10 3 DATA (280/pb)

10. Oct., 2006 10 D +   + and e +  Full event reconstruction: require a tag, require a muon cand. (E CC track < 300 MeV), veto events with extra tracks and energy clusters > 250 MeV.  Results: 50 D +   candidates Estimated bckg: 2.8 events  The same analysis is repeated for D +  e +. No signal candidates are seen: DATA

11. Oct., 2006 11 Case I: E CC track < 300 MeV Case II: E CC track > 300 MeV Sign. Candidates: 12 Est. Background: 6.1 Sign. Candidates: 8 Est. Background: 5.0 D +   +  Reconstruct D +  + with  +  + [ B (  +  + ) ~11%]; the same technique but two ’s complicate the analysis:  Consider two cases: Case I: E CC track < 300 MeV (  and  ) Case II: E CC track > 300 MeV (mostly  )  No significant signal  Broad MM 2 DATA

12. Oct., 2006 12 D S  and D S  at E CM = 4170 MeV References: CLEO CONF 06-17 hep-ex/0610026

13. Oct., 2006 13 D  S Tags (1)  Recall at E CM = 4170 MeV: D S * decays to D S via emission of ~150 MeV photon ~95% of the time  significant smearing of M BC  Tag modes used in the analysis: Yields from M(Ds) Total number of tags from M ( D s ): [19.2  0.3 (stat)]  10 3 DATA (200/pb)

14. Oct., 2006 14 D  S Tags (2)  To fully reconstruct the event, the photon must be detected. The missing mass squared can be used to obtain the number of tags: All 8 Modes DATA Total number of tags in the signal region of MM *2 : [11.9  0.4 (stat)  0.5 (syst)]  10 3

15. Oct., 2006 15 Electron Sample E CC track < 300MeV 64 events 24 events 12 events Case I: Case II E CC track > 300MeV Case III Mostly D S   + Mostly D S   + Signal region region A region B DATA D S   + and  + (  + ) (1)  Full event reconstruction: Require a tag and a  from D S *, Require one additional track, Veto events with E CC > 300 MeV or extra tracks.  Use MM 2 to separate  +,  + (  + ) and background:  Consider three cases: Case I: E CC track < 300 MeV ( accept 99% of muons and 60% of pions ) Case II: E CC track > 300 MeV ( accept 1% of muons and 40% of pions ) Case III: require an electron [Kinematical constraints are used to improve resolution and remove multiple combinations]

16. Oct., 2006 16 100 events Sum of Case I and Case II K0p+K0p+  signal line shape Consistency Check Note the scale limits: 0.20 and 0.80 GeV 2 MM 2 MC  +  + DATA D S   + and  + (  + ) (2)

17. Oct., 2006 17 Electron Sample E CC track < 300MeV 64 events 24 events 12 events Case I: Case II E CC track > 300MeV Case III Mostly D S   + Mostly D S   + Signal region region A region B DATA D S   + and  + (  + ) (3)  D S   + ( Case I, Reg.A ) 64 signal candidates, 2.0 bkg events:  D S   + ( Case I,Reg.B+Case II ) 36 signal candidates, 4.8 bkg events:  Use the SM B (  + )/ B (  + ) to average results above:  D S  e + (Case III): No signal candidates: Preliminary

18. Oct., 2006 18 D S   + ( e + )  Complimentary analysis: D S   + with  +  e +.  B ( D S  + ) B (  +  e + )~1.3% is large [cf. B ( D S + → Xe + )~8%]  Analysis Technique: Find e + and D S   tag (  from D S * is not reconstructed, same tag modes) Veto events with extra tracks Extra energy in CC < 400 MeV  Results: 400 MeV Xe + Preliminary

19. Oct., 2006 19 Comparison with theory Summary of CLEO-c results:   Unquenched LQCD [ PRL 95, 122002 (2005) ]  [Weighted average; syst. errors are mostly uncorrelated] CLEO-c: statistically limited LQCD: systematically limited An example of theor. preditions: Preliminary

20. Oct., 2006 20 Conclusions  An important task of CLEO-c is to calibrate and validate LQCD.  Charm leptonic decays provide particularly stringent tests.  Current precision of CLEO-c and LQCD results is comparable. CLEO-c results are statistically limited; LQCD results are limited by systematic uncertainties.  Expect a three fold increase in the size of CLEO-c data sample and a complete suite of leptonic and semileptonic measurements in the next few years.  On a longer time scale, BES III (China) should be able to improve CLEO-c results and further constrain the theory.

21. Oct., 2006 21 Additional Slides

22. Oct., 2006 22 Data taking started in the fall of 2003 Note: Log Scale Over 20 years operated at the Y(4S) ~16 fb -1 at the Y(4S) CESR and CLEO  The CLEO experiment is located at the Cornell Electron Storage Ring (CESR), a symmetric e + e - collider that operated in the region of the Upsilon resonances for over 20 years: Max inst luminosity achieved: 1.3  10 33 cm -2 s -1 Total integrated luminosity at the Y(4S): 16 fb -1 Lots of important discoveries, e.g., Y (nS), b  s , b  uW.  In 2003, CLEO started running at the  (3770), ~40 MeV above DD production threshold, and slightly higher energies for D S studies.  Transition from CESR to CESR-c: 12 wigglers are installed to increase synchrotron radiation/beam cooling Max luminosity achieved: ~7  10 31 cm -2 s -1

23. Oct., 2006 23 The main task of the CLEO-c open charm program: Calibrate and Validate Lattice QCD  Help heavy flavor physics constrain the CKM matrix now: Precision tests of the Standard Model or Discovery of new physics beyond the SM in b or c quark decays Difficulty: hadronic uncertainties complicate interpretation of exp. results  Help LHC search for and interpret new physics (future) Why a Charm Factory? Reduce theory error on B form factors and B decay constants using tested LQCD A realistic example using recent CKM status ( new B s mixing results are not included ): 200 fb -1 at Babar/Belle 500 fb -1 at Babar/Belle

24. Oct., 2006 24 Why now?  C. Davies opened her talk in Lisbon at EPS-2005: “There has been a revolution in LQCD…” BEFORE quenched NOW unquenched PRL 92, 022001 (2004) LQCD demonstrated that it can reproduce a wide range of mass differences and decay constants in unquenched calculations. These were postdictions. Testable predictions are now being made for: Decay constants f D and f B ; D and B Semileptonic form factors CLEO-c can test f D and D semileptonic form factors

25. Oct., 2006 25 Tagging at the  (3770)  The  (3770) is about 40 MeV above the DD pair threshold ( )  One of the two D ’s is reconstructed in a hadronic “tag” mode ( e.g., K +  - ). Two key variables:  From the remaining tracks and showers the semileptonic decay is reconstructed ( e.g., K  e + )  U  E miss  | P miss | is used to identify signal, where E miss and P miss are the missing energy and momentum approximating the neutrino E and P. The signal peaks at zero in U.  Full event reconstruction allows to measure any kinematic variable with no ambiguities and with high precision K-K-  - - e+e+ K+K+  (3770)  D 0 D 0 D 0  K +  -, D 0  K - e +

26. Oct., 2006 26 D  S Tags at 4170 MC: D S  