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Semileptonic Charm Decays

Semileptonic Charm Decays. Will E. Johns (for the FOCUS Collaboration) Vanderbilt University, BEACH 2004, July 1. Subjects Covered. Published Results. Coming Soon. Works in Progress. Data from 96-97 run of FOCUS. -Vertex Resolution -Particle ID -Mass Resolution. Lots of Pubs.

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Semileptonic Charm Decays

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  1. Semileptonic Charm Decays Will E. Johns (for the FOCUS Collaboration) Vanderbilt University, BEACH 2004, July 1

  2. Subjects Covered Published Results Coming Soon Works in Progress

  3. Data from 96-97 run of FOCUS -Vertex Resolution -Particle ID -Mass Resolution Lots of Pubs Over 1,000,000 Reco’d. Charm Very Good

  4. Semileptonic Charm Decays More than just CKM measurement tools… "Simple" Equation: (D decay, No form factors, V decays to spin 0 particles) Neutrino is left handed Prefers W spin along muon,e Prefer LZ=0 Gets Complicated... V products spinless Scalar Resonance? CP? Form Factors

  5. -15% F-B asymmetry! matches model FOCUS saw discrepancies in the data Focus “K*” signal Yield 31,254 DataMC Phys.Lett.B535:43-51, 2002 hep-ex/0203031

  6. FOCUS added a term, things got better Signal Events weighted by avg(cosqV): No added term L=0 ansatz

  7. FOCUS Semileptonic cuts description Look for N bodies with a muon Vertexing cuts: ss sp ISO1 – CL DK’s in prim L/s – L DCL – CL of DK vertex OOM – No DK’s in stuff ISO2 – No Xtra trks in DK Particle ID cuts: TRKFITcl – Muon P consistency MuCL – CL for Muon ID Cuts on P(m) for m’s Cerenkov for p’s and K’s (from ~ 4-60 GeV/c) MISIDMCS Radius, Decay Prob (Ask me offline for all the detailed cut values!)

  8. FOCUS Form Factors Tried in fit, no sensitivity (E791?) (common – vary generated parameters in Montecarlo by using agreement with reconstructed distributions and data) Technique: Pioneered by D.M. Schmidt for E691 K*ev analysis: NIM A 328 (1993) 1st find S-wave with PDG r's, then fit for r's S-wave term and r’s essentially decouple S-wave term Breaks symmetry

  9. FOCUS Form Factors Cuts similar to previous, some change to get uniform acceptance, one extra Cut on q2 < 0.2 GeV2/c2 r’s are flat, feeling mμ? Goodness of fit issue Very Clean Data • Systematic Checks • S-wave – varied cuts • 35 fits – Sample Variance • Form Factor (3 sources) • Varied Cuts • Split sample • Vary MC input • Charm Backgrounds Results: Right sign – Wrong sign Phys.Lett.B544:89-96, 2002 hep-ex/0207049 Charm Background

  10. Form Factors Comparison S-Wave effects apparent only with high statistics Lattice Gauge! Experiment Models

  11. A more detailed look at the Kp line shape Take advantage of the very clean signal Previous best K* parameters Lass (1988) Kp scattering Spectra is complicated Mass range limit in fit More Blatt-Weisskopf radius info away from pole FOCUS sees S-wave effects primarily Below K*

  12. FOCUS PRELIMINARY Using LASS parameters for ER model of d • Careful studies of resolution effects too K* Mass K* Width BL-WK radius #K* events Scalar Fraction Mass and Width Don’t change Constant d

  13. FOCUS PRELIMINARY Systematics by varying cuts, background contribution, shapes

  14. FOCUS Form Factors - Event by Event version of discrete transform method - No evidence for S - wave - Backgrounds higher (cut on M(f)) Phys.Lett.B586:183-190, 2004 hep-ex/0401001

  15. circa 1999 But the (2004) FOCUS measurement has consistent r2 values as well! Ds fmn form factor enigma Ds fmnversusD+ K*ln Theoretically the Dsflnform factor should be within 10% of D+ K*ln . The rV values were consistent but r2 for Dsflnwas  2 higher than D+ K*ln .

  16. Backgrounds Make a difference! A peek at: Biggest Players: Signal, ~400 events (red and dots) Combinatoric Background, ~750 events (pink hatch) Muon Misid, ~300 events (faint black histogram)

  17. Cabibbo suppressed SL Decay A Cabibbo favored SL decay Would be a discovery! Right Sign Wrong Sign DsK*mndecay is a small WS background component in our previous D+K*mn work Easy to see and study MKp (GeV/c2) Search for Cabibbo Suppressed Ds semileptonic decay Note kaon and muon have same sign In Fact: K p mass in Kpm events K+ K- mass in KKm events What’s this?

  18. dataMC After lots of cuts Preliminary results of the search We compared the WS Kp spectrum to a MC that incorporated all known charm decay and normalize the MC to the D+K*mnyield observed in the data With tight cuts, the MC matched the data away from the K* peak. We saw a 3.9s excess in K* yield in data over MC In the loosely cut sample, the MC was a poor match to the observed WS Kp spectrum. Large non-charm contribution? MKp (GeV/c2) MKp (GeV/c2) If this K* excess were interpreted as DsK*mn, we would obtain... preliminary This BR is very consistent with (10 ±1.3)% predicted by R.J. Oakes et al. (1997) (hep-ph/9708277)

  19. FOCUS BR Measurements Phys.Lett.B540:25-32, 2002 hep-ex/0206013 events / 5 MeV/c2 events / 10 MeV/c2 Includes S-wave interference

  20. BR relative to fp are consistent 0.620.02 fmn/ fp G(K*l n)/G(Kpp) muons electrons BR Comparisons to Exp. & Models but, BR relative to Kpp …not so good

  21. ? What about • Could resolve lepton ID issues • Topological trouble though • > need an extra particle for K* • Most Experiments measure ~0.5 (E687 too!) • (some use rates though…compare D+D0) But CLEO2 Reported Using the From the PDG But using PDG values we also find: Isospin Violation?

  22. Reconstruct both FOCUS In the FOCUS silicon Drawback: Only about 10% of Ks>p+p- Decays occur in the FOCUS silicon Find Background Dominated by D>KsXmn

  23. hep-ex/0406060 Submitted to PLB FOCUS is world’s best Measure: Correct for S-Wave: Use Focus K*mn and PDG Kpp, compare to D0: Isospin OK again Long standing “difference” for D0 is in “wrong” direction ?=1.03=?

  24. Comparison to other Experiments and Theory Focus measurements suggest little “missing” Semileptonic rate Other Exp’s Models PDG Sum of PDG CA e modes Focus m’s as e’s Hard to believe PDG for PS electron is correct

  25. Preview of other FOCUS analysis -Plot of pseudo D*-D mass difference -Will repeat Vector analysis (tough to see S-wave) -measure q2 shape and BR for pmn and Kmn (expect dBR/BR<10%)

  26. Conclusions: • We’ve gotten a lot of physics out of the careful analysis of the Vector decays (S-wave, B(K*,f), M(K*), r’s, W(K*), CS(K*)… • Resolved some outstanding enigmas (f ff’s, V/PS Ratio, PDG rates) • Raised some new ones (low q2 in K*, proper S-wave description • Looking at new things

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