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


Slide2: Subjects Covered


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


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


FOCUS saw discrepancies in the data: FOCUS saw discrepancies in the data Phys.Lett.B535:43-51, 2002 hep-ex/0203031 Yield 31,254 Data MC Focus “K*” signal


Slide6: FOCUS added a term, things got better L=0 ansatz Signal Events weighted by avg(cosqV): No added term


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


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


FOCUS Form Factors: 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 Right sign – Wrong sign Charm Background Systematic Checks S-wave – varied cuts 35 fits – Sample Variance Form Factor (3 sources) Varied Cuts Split sample Vary MC input Charm Backgrounds Phys.Lett.B544:89-96, 2002 hep-ex/0207049 Very Clean Data


Slide10: Form Factors Comparison S-Wave effects apparent only with high statistics Lattice Gauge! Experiment Models


A more detailed look at the Kp line shape: 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*


Slide12: Using LASS parameters for ER model of d Constant d FOCUS PRELIMINARY K* Mass K* Width BL-WK radius #K* events Scalar Fraction Mass and Width Don’t change Careful studies of resolution effects too


Slide13: FOCUS PRELIMINARY Systematics by varying cuts, background contribution, shapes


Slide14: FOCUS Form Factors - Event by Event version of discrete transform method - No evidence for S - wave Phys.Lett.B586:183-190, 2004 hep-ex/0401001 - Backgrounds higher (cut on M(f))


Ds  fmn form factor enigma: Ds  fmn form factor enigma Theoretically the Dsfln form factor should be within 10% of D+ K*ln . The rV values were consistent but r2 for Dsfln was  2 higher than D+ K*ln . Ds  fmn versus D+ K*ln


Slide16: Backgrounds Make a difference! Biggest Players: Signal, ~400 events (red and dots) Combinatoric Background, ~750 events (pink hatch) Muon Misid, ~300 events (faint black histogram) A peek at:


Search for Cabibbo Suppressed Ds semileptonic decay: Search for Cabibbo Suppressed Ds semileptonic decay Note kaon and muon have same sign K+ K- mass in KKm events K p mass in Kp m events What’s this?


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


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


BR Comparisons to Exp. & Models: BR Comparisons to Exp. & Models BR relative to Kpp …not so good


Slide21: 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?


Slide22: FOCUS In the FOCUS silicon Reconstruct both Drawback: Only about 10% of Ks>p+p- Decays occur in the FOCUS silicon Find Background Dominated by D>KsXmn


Slide23: FOCUS is world’s best Correct for S-Wave: hep-ex/0406060 Submitted to PLB Measure: Use Focus K*mn and PDG Kpp, compare to D0: Isospin OK again ?=1.03=? Long standing “difference” for D0 is in “wrong” direction


Slide24: Other Exp’s Models Comparison to other Experiments and Theory Focus measurements suggest little “missing” Semileptonic rate PDG Sum of PDG CA e modes Focus m’s as e’s Hard to believe PDG for PS electron is correct


Slide25: 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%)


Conclusions:: Conclusions: Resolved some outstanding enigmas (f ff’s, V/PS Ratio, PDG rates) Raised some new ones (low q2 in K*, proper S-wave description 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*)… Looking at new things