1. CHARM 2007, Cornell University, Aug. 5-8, 20071Steven Blusk, Syracuse University D Leptonic Decays near Production Threshold Steven Blusk Syracuse University (on behalf of the CLEO Collaboration)

2. CHARM 2007, Cornell University, Aug. 5-8, 20072Steven Blusk, Syracuse University Introduction: D  + Introduction: D  +  Partial width measurement probes the hadronic vertex  Soft-gluon effects  Non-perturbative QCD  Decay constant, f D describes the hadronic vertex, and is proportional to the wave-function overlap (Prob  cd(s)  W annihilation)  General solution (SM) for partial width _ Calculate, or measure if V Qq known (s) or cs

3. CHARM 2007, Cornell University, Aug. 5-8, 20073Steven Blusk, Syracuse University Leptonic Decays in SM Measurement provides critical test of theory to compute f B, f Bs. Measurement provides critical test of theory to compute f B, f Bs. In a few years, we will have a precision measurement (~5 o ) of  (  3 ) by LHC b. In a few years, we will have a precision measurement (~5 o ) of  (  3 ) by LHC b. Expect  (  )~5 o with 2 fb -1 Expect  (  )~5 o with 2 fb -1 Could provide signs of NP if  measurement doesn’t coincide with  m (s,d) band. Could provide signs of NP if  measurement doesn’t coincide with  m (s,d) band. B    gives V ub f B, but hard to measure B    gives V ub f B, but hard to measure directly. directly. Constraints from V ub,  m d,  m s & B  

4. CHARM 2007, Cornell University, Aug. 5-8, 20074Steven Blusk, Syracuse University New Physics in D (s) leptonic decays  Deviations from lepton universality possible if tan  large Hewett [hep-ph/9505246] & Hou, PRD 48, 2342 (1993).  Interference between H ± and W ± suppresses D s  l, but NOT D  l Akeroyd, hep-ph/0308260 Deviations of this ratio from SM value of 9.72 would signal New Physics

5. CHARM 2007, Cornell University, Aug. 5-8, 20075Steven Blusk, Syracuse University D and D s Landscape near threshold  Produce DD at  (3770).  No additional particles  Coherent 1– state  Ideal for absolute BF measurements  Measurements from 281 pb -1 (Phys. Rev. Lett. 95, 251801 (2005))  Not reviewed in this talk  D s Leptonic Decays  Dedicated scan to find optimal energy for D s physics (see talk by B. Lang)  At E cm = 4170 MeV  (D s D s *)~0.9 nb  Additional photon, ~100 MeV to contend with.

6. CHARM 2007, Cornell University, Aug. 5-8, 20076Steven Blusk, Syracuse University Reconstructed D s “Tags” at 4170 MeV Leptonic analyses require one fully reconstructed D s decay (“tag”). Leptonic analyses require one fully reconstructed D s decay (“tag”). 8 tag modes 8 tag modes Signal region: Signal region: |M rec -M Ds | < 2.5  |M rec -M Ds | < 2.5  Sidebands: Sidebands: 5.0<|M rec -M Ds | < 7.5  5.0<|M rec -M Ds | < 7.5  Total # of Tags Total # of Tags = 31,302 ± 472 (stat) = 31,302 ± 472 (stat) K * K * from K s K     

7. CHARM 2007, Cornell University, Aug. 5-8, 20077Steven Blusk, Syracuse University Measurements of f Ds D tag Ds*Ds* DsDs  or    e+e+ e-e-  D tag DsDs DsDs  or    e+e+ e-e-  D tag DsDs DsDs   e e+e+ e-e-  “Missing Mass” Analyses (314 pb -1 ) Accepted to PRD arXiv:0704.0437v2 arXiv:0704.0437v2 “Missing Energy” Analysis (195 pb -1 ) Preliminary  Only one additional track, K ± rejection using PID  No additional  with E>300 MeV  Use (missing) mass recoiling against (D s *+  ) D s  (  ) from D s *D s  (  ) from D s  Only one additional track, consistent with electron hypothesis  Signal discriminant: Remaining energy in calorimeter after tag and electron are removed.

8. CHARM 2007, Cornell University, Aug. 5-8, 20078Steven Blusk, Syracuse University Anatomy of Missing Mass Analyses D tag Ds*Ds* DsDs   or    e+e+ e-e-  D s  (  ) from D s D tag DsDs DsDs e+e+ e-e-  D s  (  ) from D s *   or   

9. CHARM 2007, Cornell University, Aug. 5-8, 20079Steven Blusk, Syracuse University Missing Mass Analyses – N tag *  Take each D s tag and photon candidate and compute the recoil mass against (D s tag +  ). regardless of whether D s +  forms D s *, recoil mass peaks at M(D s ) 2  N tag * = 18645±426(stat) tags, after 2.5  selection on MM* 2. All 8 Modes D tag Ds*Ds* DsDs   or    e+e+ e-e-  D s  (  ) from D s All 8 Modes D tag Ds*Ds* DsDs   or    e+e+ e-e-  D s  (  ) from D s * All 8 modes combined

10. CHARM 2007, Cornell University, Aug. 5-8, 200710Steven Blusk, Syracuse University Missing Mass Analyses – Signal Side All 8 Modes D tag Ds*Ds* DsDs   or    e+e+ e-e-  D s  (  ) from D s All 8 Modes D tag Ds*Ds* DsDs   or    e+e+ e-e-  D s  (  ) from D s * For each D s * candidate, perform a kinematic fit, imposing the following constraints: Two solutions for each D s * candidate   belongs with D s tag   belongs with D s   (try both)

11. CHARM 2007, Cornell University, Aug. 5-8, 200711Steven Blusk, Syracuse University Missing Mass Analyses – Signal Side All 8 Modes D tag Ds*Ds* DsDs   or    e+e+ e-e-  D s  (  ) from D s All 8 Modes D tag Ds*Ds* DsDs   or    e+e+ e-e-  D s  (  ) from D s * For each D s * candidate, perform a kinematic fit, imposing the following constraints: Choose solution with lowest  2 (but no cut), and compute: Signal D s   Signal D s   →  Two possibilities for each D s * candidate   belongs with D s tag   belongs with D s   (try both) Signal MC

12. CHARM 2007, Cornell University, Aug. 5-8, 200712Steven Blusk, Syracuse University MM 2 from CLEO-c Data Electron Sample 92 events 31 events Return to 3 separate cases: i. E trk CC <300 MeV  “D   -like”: (  ~99%) - 0.05<MM 2 <0.05 GeV 2  “D     -like”: (  ~60%) 0.05<MM 2 <0.20 GeV 2 ii. E trk CC >300 MeV  “D     -like”: (  ~40%) - 0.05<MM 2 <0.20 GeV 2 iii.Electron-like E trk CC > 0.3 GeV in CC E trk CC < 0.3 GeV in CC 25 events

13. CHARM 2007, Cornell University, Aug. 5-8, 200713Steven Blusk, Syracuse UniversityBackgrounds  Combinatoric background under peaks: Use D s cand. mass sidebands  D s   backgrounds from real D S decays Signal region High SB region Low SB regionSampleSignal Comb. Back. (i) E trk CC <300 MeV, “D   -like”92 3.5±1.4 (ii) E trk CC <300 MeV, “D   -like”31 2.5±1.1 (iii) E trk CC >300 MeV, “D   -like”25 3.0±1.3 Total148 9.0 ±1.3 Background BF (%) E trk CC <300 MeV, “D   -like” DsXDsX 0 +1.8 -0 0 DsXDsX1.0 0.03±0.04 0.08±0.03 D s            1.5 0.55±0.22 0.64±0.24 D s           1.0 0.37±0.15 0 Total 1.0 +1.8 -0.3 0.7±0.2 Negligible real D s decay background to D s   Since B(D s      ) <1.1x10 -3 @ 90% CL

14. CHARM 2007, Cornell University, Aug. 5-8, 200714Steven Blusk, Syracuse University Branching fractions N tag =18645±426±1081  = efficiency for reconstructing     = 80.1%   = efficiency for E CC <300 MeV + |MM 2 |<50 MeV = 91.4%   = efficiency for E CC <300 MeV(60%) + |MM 2 |<50 MeV(13%) = 13.2% N  = 92 – (3.5±1.4) = 88.5±9.7 B(D S + →  +  (0.597±0.067±0.039)% B(D S + →  +  B(D S + →  +  Type (i) Type (ii) N cand 3125 N back 3.5 +1.7 -1.1 5.1±1.6  (E trk CC )60%40% MM 2 )req.  (MM 2 )req.32%45% B(D S + →  +  (8.0±1.3±0.4)%

15. CHARM 2007, Cornell University, Aug. 5-8, 200715Steven Blusk, Syracuse University Combined f Ds Combine (i) and (ii).   = 91.4%   = 45.2% N  = 148 – (10.7 +2.9 -2.3 ) (still applies)  B eff (D S + →  +   (0.638±0.059±0.033)%  f Ds = 274 ± 13 ± 7 MeV  B(D S + → e +  x10 -4 @90%CL Signal region Results

16. CHARM 2007, Cornell University, Aug. 5-8, 200716Steven Blusk, Syracuse University Missing Energy Analysis D S + →  +  + → e + Missing Energy Analysis D S + →  +  + → e + Xe + Use 195 pb -1 at E cm =4170 MeV Reconstruct D s tag, use recoil from D s to get N(D s D s * ) Require one extra electron candidate + no other tracks. No need to find  from D S * Main backgrounds from D S + →Xe +   Discriminant is E CC extra : extra energy in CC left over after showers associated to reconstructed particles are removed. Signal region: E CC extra < 400 MeV Background obtained by scaling MC B(D S + →  +  (6.29±0.78±0.52)%  f Ds = 278 ± 17 ± 12 MeV (Preliminary)

17. CHARM 2007, Cornell University, Aug. 5-8, 200717Steven Blusk, Syracuse University Combined results Weighted Average: f Ds =275±10±5 MeV, the (systematic errors are mostly uncorrelated between the measurements) Weighted Average: f Ds =275±10±5 MeV, the (systematic errors are mostly uncorrelated between the measurements) Previously CLEO-c measured Previously CLEO-c measured M. Artuso et al., Phys.Rev. Lett. 95 (2005) 251801 M. Artuso et al., Phys.Rev. Lett. 95 (2005) 251801 Thus f Ds / f D + =1.24±0.10±0.03 Thus f Ds / f D + =1.24±0.10±0.03  (D S + →  +  (D S + →  +   (D S + →  +  (D S + →  +  11.5±2.0, SM=9.72, 11.5±2.0, SM=9.72, consistent with lepton universality consistent with lepton universality D + →    pb   at  K0+K0+  

18. CHARM 2007, Cornell University, Aug. 5-8, 200718Steven Blusk, Syracuse University Comparisons with theoretical expectations CLEO-c data consistent with most models, more precision needed CLEO-c data consistent with most models, more precision needed Using Lattice ratio find |V cd /V cs |=0.2166± 0.020 (exp) ±0.0017(theory) Using Lattice ratio find |V cd /V cs |=0.2166± 0.020 (exp) ±0.0017(theory)

19. CHARM 2007, Cornell University, Aug. 5-8, 200719Steven Blusk, Syracuse University Comparison to previous measurements CLEO-c is most precise result to date for both f Ds & f D + CLEO-c is most precise result to date for both f Ds & f D + 275±10±5 -2

20. CHARM 2007, Cornell University, Aug. 5-8, 200720Steven Blusk, Syracuse University  Decay constants from CLEO-c are most precise to date  Expect to reach a precision of ~4.0-4.5% on these decay constants with full CLEO-c (through Apr 2008). Summary

21. CHARM 2007, Cornell University, Aug. 5-8, 200721Steven Blusk, Syracuse University Backups

22. CHARM 2007, Cornell University, Aug. 5-8, 200722Steven Blusk, Syracuse University Missing Mass Distributions - MC Check of resolution, procedure using D s  K s K - Remove extra track/shower/K ± veto  MC resolution consistent w/ data  Find BF=(2.90±0.19±0.18)%, Result from double tags: (3.12±0.16±0.10)%  This background is wiped out by the PID requirement on the stiff .