1. D leptonic decay and semi- leptonic decays from BESIII Yangheng Zheng University of Chinese Academy of Sciences (on behalf of BESIII collaboration) July. 4, 2014

2. 2Outline  Introduction  Experimental challenge  D + Leptonic decays  D 0 Semileptonic decays  Summary

3. 3 Overall picture  Windows on weak and strong physics  Weak decay  theoretically clean  Over-constrain CKM and search for New Physics  Strong interaction  test Lattice QCD

4. 4 Leptonic decays  Extract decay constant f D(s) incorporates the strong interaction effects (wave function at the origin)  Multiple tests with charm: f D, f Ds and f D /f Ds  To validate Lattice QCD calculation of f B(s) and provide constrain of CKM-unitarity  Sensitive to New Physics (Charged Higgs contribution, …)

5. 5 Semileptonic decays  D (s)  P l (Theoretically clean)  Measure |V cx | x FF  Charm physics:  CKM-unitarity  | V cx |, extract FF, test LQCD  Input LQCD FF to test CKM-unitarity  B physics : Validate LQCD for form factor, extract |V ub | to test CKM-unitarity  Example: B  l  |V ub | = 3.92  0.09  0.45(Theory) rely on LQCD Form Factor calculations (provide perfect calibration) q 2 =(p l +p ) 2  M 2 inv of lepton pair

6. 6 Recon. @charm threshold  Double tag techniques: Hadronic tag on one side, on the other side for leptonic/semileptonic studies. Neutrino is reconstructed from missing energy and momentum (Double tag efficiency is high.)

7. 7 Data samples  BESIII: 2.9 fb -1 (World largest  (3770) sample @ threshold)  BESIII plans to operate for 8 more years.

8. 8 Tag Selection (D +   )  Tag side reconstruction:  Kinematic variables: Beam- constrained mass and  E  (1.703  0.003) M tags found Beam-constrained mass of tag D  Nine D - tag modes Phy. Rev. D89, 051104

9. Signal Selection (D +   + )  Signal side reconstruction:  In addition to Tag, only one charged track with right charge  Identified as   No isolated photon  Kinematic variable: M 2 miss  451 D   candidates observed  Low background Muon counter information applied to reduces background at the expense of slightly reduced efficiency. 9  + Phy. Rev. D89, 051104

10. Results (D +   + ) N(D +   + ) = 409.0  21.2  2.3 B(D +   + ) = (3.71  0.19  0.06) x 10 -4 f D+ = (203.2  5.3  1.8)  |Vcd| of CKM-Fitter Input |Vcd| = 0.221  0.006  0.005  LQCD calculated f D = 207±4 MeV[PRL100(2008)062002] 10 Phy. Rev. D89, 051104

11. Comparisons of B[D +  μ + μ ] and f D+ 11 (0.0371  0.0019  0.0006)% BESIII (203.2  5.3  1.8) BESIII

12. 12 Tag selection (D 0  K/  e + )  Tag side reconstruction:  Fully reconstruct 4 decay modes for one side D  2.79 M tags found Beam-constrained mass of tag D  BESIII Preliminary results  Full dataset: 2.9 fb -1 DK+DK+ DK+DK+ DK+DK+ DK+DK+ DK+DK+

13. 13 Signal selection (D 0  K/  e + ) BESIII Preliminary N sig = 70727  278 N sig = 6279  87  Signal side reconstruction:  Tag plus exactly two oppositely-charged tracks  Kaon/pion/electron ID  Electron has right charge  No extra neutral energy  Kinematic variable: U miss  Good consistency with CLEO-c  BESIII Preliminary Decay modeBranching fraction (%)PDGCLEOc 3.505  0.014  0.0333.55  0.043.50  0.03  0.04 0.295  0.004  0.0030.289  0.0080.288  0.008  0.003

14. Comparisons of B[D 0  K(  ) - e + ] 14 B[D 0  K  e  ] B[D 0    e  ]

15. 15 Form Factor Fits (D 0  K/  e + ) D 0  Ke D 0   e  Fitted using different form factor models  Simple pole model  Modified pole model (Becirevic and Kaidalov, PLB 478, 417)  Series expansion (CLEO-c/BES III both explored 2nd and 3rd order): Decay rate

16. 16 Form Factors fit results (D 0  K/  e + ) D0K-e+vD0K-e+v D0-e+vD0-e+v Simple Pole f K + (0)|V cs | 0.7209  0.0022  0.0033 f  + (0)|V cd | 0.1475  0.0014  0.0005 M pole 1.9207  0.0103  0.0069 M pole 1.9114  0.0118  0.0038 Mod. Pole f K + (0)|V cs | 0.7163  0.0024  0.0034 f  + (0)|V cd | 0.1437  0.0017  0.0008  0.3088  0.0195  0.0129  0.2794  0.0345  0.0113 ISGW2 f K + (0)|V cs | 0.7139  0.0023  0.0034 f  + (0)|V cd | 0.1415  0.0016  0.0006 r ISGW2 1.6000  0.0141  0.0091 r ISGW2 2.0688  0.0394  0.0124 Series.2.Par f K + (0)|V cs | 0.7172  0.0025  0.0035 f  + (0)|V cd | 0.1435  0.0018  0.0009 r1r1 -2.2278  0.0864  0.0575 r1r1 -2.0365  0.0807  0.0260 Series.3.Par f K + (0)|V cs | 0.7196  0.0035  0.0041 f  + (0)|V cd | 0.1420  0.0024  0.0010 r1r1 -2.3331  0.1587  0.0804 r1r1 -1.8434  0.2212  0.0690 r2r2 3.4223  3.9090  2.4092 r2r2 -1.3871  1.4615  0.4677

17. 17 f(q 2 ) shapes (D 0  K/  e + ) D0-e+vD0-e+v D0K-e+vD0K-e+v

18. Comparisons of Form Factors 18  Experimental data calibrate LQCD calculation  Points: BESIII preiminary data  Curves: from Fermilab-MILC-HPQCD, PRL94 (2005) 011601; Fermilib Lattice and MILC, PRD80 (2009) 034026 Solid lines represent LQCD fits to the BK model, PLB478 (2000)417 D0-e+vD0-e+v D0K-e+vD0K-e+v

19. 19 Summary and future perspective

20. Thank you

21. Backup slides