1. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Form Factors and Absolute BRs for D 0   / K KEK 高エネルギ Belle in a nutshell e-e- 8GeV e+e+ 3.5GeV  = 0.425 located at KEK / Japan KEKB Collider B-Factory at  (4s) resonance peak luminosity 16.270 1/nb/s integrated luminosity 600 1/fb (as of June 2006; 280 1/fb used in this analysis) main physics goal: observation of CPV in B meson Decays Laurenz Widhalm HEPHY Vienna Belle Collaboration q²

2. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th single form factor f D (q 2 ) calcuable in LQCD, but needs checking from data D-System ideal for experimental input results can be applied in B-physics (extraction of CKM parameters) Why are semileptonic decays interesting? q²

3. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th K tag  D  mass-constrained vertex fits e+e- 3.5 GeV8 GeV   K K D0D0  slow e/µ    D* - „inverse“ fit tag side Method of Reconstruction (Event Topology)   D* signal side additional primary mesons IP    note: all possible combinations tried in parallel cuts after complete reconstruction equal weight for remaining combinations  no event loss due to particle exchanges!

4. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th D 0 Signal and Background* charm (D°) charm, no D° B±B± B0B0 uds wrong sign D° data (normalized) result (282 fb -1 of BELLE data) yield after cuts 95250 background 38789 signal charge correlation signal subtraction stats bkg sample 56461 ± 309 stat ± 776 syst ± 233 syst ± 194 syst cuts all mass-constr. fits CL >0.1% (released on D 0 fit for righthand plot) same charge K tag /  slow * from decays without a D 0, or combinatorial background control region signal region signal D 0 invariant mass opposite sign K tag /  slow same sign K tag /  slow MC note: data used for bkg subtraction, MC shown only for comparison  =0.0006 GeV!

5. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th D 0  K/  l Signal and Background D 0   l m ² / GeV² D 0   l Background sources 1.fake D 0 2.other semileptonic channels 3.hadronic channels additional cuts same charge  slow / lepton extra  energy < 700 MeV no excess charge E > 100 MeV recoil neutrino mass signal region note high resolution  (m² )=0.016 GeV²

6. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th fake-D 0 bkg bkg from K  bkg from K*/  * smaller background for  e and Kl  handled likewise data control region for K*/  bkg measurement signal region recoil neutrino mass for D 0   l D 0  K/  l Signal and Backgrounds (for  )* bkg from misidentified kaons bkg from misidentified pions semileptonic background opposite sign µ/  slow same sign µ/  slow signal region hadronic background MC data note: data used for bkg subtraction, crosschecked by MC

7. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Summary of Signal / Background Decomposition Results (282 fb -1 of BELLE data) Ke KK e  signal events1318 ± 37 stat ± 7 syst 1249 ± 37 stat ± 25 syst 126 ± 12 stat ± 3 syst 106 ± 12 stat ± 6 syst fake D 0 bkg12.6 ± 2.2 12.2 ± 4.8 12.3 ± 2.2 12.5 ± 4.5 semileptonic bkg*6.7 ± 2.6 10.0 ± 2.5 11.7 ± 1.2 12.6 ± 1.9 hadronic bkg**11.9 ± 5.6 62.1 ± 23.9 1.8 ± 0.7 9.7 ± 3.7 fake-D 0 bkg Kl bkg D 0   e D 0    l bkg D 0   e D 0   hadronic bkg m ² / GeV² * error dominated by MC stats ** error dominated by fit errors & bias special bkg sample MC data remaining signal

8. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Absolute Branching Ratios BRs (%)this analysisPDG (2005) CLEO-c (hep-ex/0505035) K - e + 3.45 ± 0.10 stat ± 0.19 syst 3.62 ± 0.163.44 ± 0.10 stat ± 0.10 syst K -  + 3.45 ± 0.10 stat ± 0.21 syst 3.20 ± 0.17  - e + 0.279 ± 0.027 stat ± 0.016 syst 0.311 ± 0.0300.262 ± 0.025 stat ± 0.008 syst  -  + 0.231 ± 0.026 stat ± 0.019 syst 0.24 ± 0.04 ratio to total number of recoil D 0 tags efficiency correction corrected for bias due to differences data/MC (1.9%±3.9%)

9. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Form Factors – q² distribution signal non-D bkg hadronic bkg semileptonic bkg D 0   e D 0   e D 0   D 0   q² background shapes from data  (q²) = 0.0145 GeV²/c² (width of red line)  no unfolding necessary!

10. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Form Factors - Theory in principle, two form factors f + (q²) and f - (q²) kinematically only f + (q²) relevant, f - (q²) suppressed by m l ² three different models that are frequently discussed in literature: f + (q²) = 1-q²/m²   f + (0) m......pole mass = m D* s  2.11 GeV (Kl ) = m D*  2.01 GeV (  l ) simple pole f + (q²) = (1-q²/m²) (1-  q²/m²)  modified pole ISGW2  0.50 (Kl )  0.44 (  l )  theor. f + (q²) = (1-  q²-q² max) )²  G. Armoros, S. Noguera, J. Portoles, Eur. Ph. J. C27, 243 (2003) N. Isgur and D. Scora, Phys. Lett. B 592 1(2004)

11. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Form Factors – Comparison with Models ISGW2 model lattice calculation modified pole model D 0   l D 0   l pole mass (GeV) Kl 1.82 ± 0.04 stat ± 0.03 syst  l 1.97 ± 0.08 stat ± 0.04 syst simple pole  Kl 0.52 ± 0.08 stat ± 0.06 syst  l 0.10 ± 0.21 stat ± 0.10 syst modified pole (poles fixed at theo. values) fit results f + (0) Kl 0.695 ± 0.007 stat ± 0.022 syst  l 0.624 ± 0.020 stat ± 0.030 syst

12. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th events searched in e + e -  D (*) D *c X (X=n  /K) new full-reconstruction-recoil method: 56k D 0 in 282 fb -1 of BELLE data high resolution neutrino  (m² )=0.016 GeV² background <5%(<27%) for K/  absolute BRs of better accuracy than previous experiments, in good agreement with recent CLEO measurements good agreement with relative measurements done by BES and FOCUS high q² resolution, no unfolding necessary absolute multi-bin measurement of f+(q²) measured form factor in good agreement with theoretical predictions and other experiments competitative with recent CLEO-c measurements preprint hep-ex/0604049, submitted to PRL Laurenz.Widhalm@oeaw.ac.at Form Factors and Absolute BRs for D 0   / K Summary & Conclusion

13. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Spares

14. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th tag side: reconstruction & fit of D 0,±  K , K2 , K3  reconstruction & fit of D* 0,±  D , D  use either D or D* as primary meson signal side: reconstruction & fit of inclusive D* 0,± via recoil from e+e-  D (*) D*n  /K reconstruction & fit of inclusive D 0 via recoil from D*  D  reconstruction & fit of neutrino via recoil from D  m   D  D*  e+e- D  e/µ  D* tagsignal  K ( )   K K additional primary mesons Method of Reconstruction (Event Topology)

15. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Method of Reconstruction (Event Topology) m/GeV D* + tag D* 0 tag D* - sig m/GeV D 0 sig m/GeV

16. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th stable particle selection: gammas: p > 40 MeV charged tracks (general): p > 100 MeV trk_fit.nhits(3) > 0 dr < 2 cm, dz < 4 cm electron: p > 500 MeV eid.prob(3,-1,5) > 0.9 muon: p > 500 MeV prerejection != 1 Muon_likelihood > 0.9 kaon / pion: atc_pid (3,1,5,3,2) prob*(1-prob_e-prob_mu) > 0.5 for meson in hlnu: > 0.9 unstable particle selection: pi0: PDG mass ± 10 MeV fit CL > 0.1 K0: only via decay pi+pi- PDG mass ± 25 MeV D_tag: channels Knpi, n=1-3 PDG mass ± 20 MeV D*_tag: channel Dpi, D  PDG mass ± 5 MeV mass/vertex fit CL > 0 D*_signal: via recoil from D*_tag+n pi/K, n=0-5 mass/vertex fit CL > 0.001 D_signal: via recoil from D*_signal  Dpi mass/vertex fit CL > 0.001 : via recoil from D_signal  hlnu |m²| < 0.05 GeV² mass/vertex fit CL > 0 additional Klnu / pilnu cuts: E_leftover < 700 MeV, no leftover charge E_nu > 100 MeV right charges of slow pions & lepton List of Cuts

17. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Bias by mass-constrained Fits on Background? very sharp mass peak after fit no bias on background   no real D 0 D 0 invariant mass with real D 0 after fit of D* before fit of D*  

18. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th D 0 Signal and Background* charm MC charm, no D° B ± MC B 0 MC uds MC wrong sign true D° data (normalized) result (282 fb -1 of BELLE data) yield selected D 0 events 95250 subtracted background 38789 signal 56461 ± 309 stat ± 830 syst systematics breakdownevents charge correlation RS/WS776 WS signal subtraction233 statistics of WS sample194 cuts confidence level of all mass-constrained vertex fits >0.1% (released on D 0 fit for righthand plot) right charge correlation between slow pion and tag side kaon (right sign, RS) procedure to measure background: select wrong charge correlation data (WS) to get shape of background correct for small WS signal component normalize to RS data in region 1.84-1.85 GeV * from decays without a D 0, or combinatorial background control region signal region signal D 0 invariant mass opposite sign K tag /  slow same sign K tag /  slow

19. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Measurement of Semileptonic Background (for  l )* procedure to measure background: 1. crosstalk from Kl : prepare special background sample, with K intentionally misidentified as  normalize to standard Kl sample then reweight the sample using known** efficiencies / fake rates (in p,  ) 2. background from vector mesons: get shapes for K*l and  l from MC (simulated ratio K*/  from PDG) normalize to data in region m² > 0.3 GeV² * background for Kl  is very small, and is handled the same way ** measured independently in data measured bkg from K*l measured bkg from Kl measured bkg from  l data control region for K*/  bkg measurement non-D° bkg (measured as described previously) signal region recoil neutrino mass D 0   l

20. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th procedure to measure background: prepare special background samples, with K(  ) intentionally misidentified as  (subtract fake D 0 background in these samples with the method described above) separate into same sign (SS) and opposite sign (OS) samples, with respect to the charges of the lepton and the slow pion semileptonic channels are highly suppressed in OS  clean sample of hadronic background perform a 2-parameter fit in the standard OS sample, using the shapes from the OS background samples for K and  to measure the effective fake rates then apply these fake rates in the background SS sample to obtain the backgrounds in the signal sample Measurement of Hadronic Background (for  )* same sign SS signal: D*  D 0  +   -  + both signs D*  D 0  +   -  +      -  ± opposite sign OS D*  D 0  +  K -  +    +  - D*  D 0  +  K -  +      -  + * significant background only for this channel; other channels are handled likewise OS SS OS

21. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Fit of Hadronic Background (for  )* bkg from misidentified kaons bkg from misidentified pions fake-D 0 bkg bkg from K  remaining events in signal region bkg from K*/  D 0   MC true composition * background for  e and Kl  are much smaller fit in this sample  use result of fit here  OS SS comparison with MC D0  K0-+D0  K0-+ D 0  K -  +  0 D0  -+0D0  -+0 green = particle seen in recoil mass signal region

22. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Measured Absolute Form Factors as function of q² extracted by dividing q² distribution by kinematical factor no unfolding necessary due to very good q² resolution D 0   e D 0   D 0   e D 0  

23. D 0  K/  l Analysis Laurenz Widhalm 北京, June 5 th Form Factor Theory * G. Amoros et al., hep-ph/0109169 in principle, two form factors f + (q²) and f - (q²) kinematically only f + (q²) relevant, f - (q²) suppressed by m l ² applying certain boundary conditions, theory* suggests model-independently a pole- structure for the form factor: f + (q²) = 1-q²/m²   f + (0) m......pole mass = mass D* s  2.11 GeV (Kl ) = mass D*  2.01 GeV (  l ) Ke q² / GeV²  KK  e q² / GeV² f+ kinematical factor f- kinematical factor f+ kinematical factor f- kinematical factor f+ kinematical factor f- kinematical factor f+ kinematical factor f- kinematical factor