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Charm Semileptonic Decay

Charm Semileptonic Decay. Jim Wiss Univ of Illinois HQL2004 June 2 , 2004. The importance of charm SL decay Pseudoscalar l n decay Vector l n decay Analysis of D  K* mn The V/PS enigma : G (D+  K* mn / K mn) The D s  fmn form factor enigma The future of SL decay

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Charm Semileptonic Decay

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  1. Charm Semileptonic Decay Jim Wiss Univ of IllinoisHQL2004June 2 , 2004 • The importance of charm SL decay • Pseudoscalar l n decay • Vector l n decay • Analysis of DK*mn • The V/PS enigma: G (D+K*mn / Kmn) • The Dsfmn form factor enigma • The future of SL decay • Cleo-c / Bes III y(3770) running Featuring results from E791 Apologies for all the important and fascinating results that I had to skip E687

  2. Charm semileptonic decay as tests of LQCD The form factors incorporate hadronic complications and can be calculated via non-perturbative Lattice QCD. Apart from form factors, these decays can be computed using perturbation theory and are first order in CKM elements Charm SL decays provide a high quality lattice calibration crucial to reducing future systematic error in the Unitarity Triangle. The same techniques validated in charm can be applied to beauty.

  3. Pseudoscalar l n decays is easiest for LQCD Kaon at rest in D frame Two forms are used to parameterizef+(q2) cleanest theory highest rate pole ISGW Provides a way to either measure CKM elements or to verify f+(q2) calculations These should be among the first unquenched lattice calculations... ...But a major disconnect exists between experiment and theory. Theory works best where experiment works worse.

  4. Comparing pole versus ISGW form in Dpen ...where differences are dramatic. pen decay gets quite close to the D* pole... hep-ph/0101023 Lattice better sys as Pp0 The lattice can now calculate f+ as a function of q2. Unfortunately present LGT offers very little discrimination between the two common forms Dpen should provide a powerful test of future lattice predictions But pastpen signals have severe backgrounds and poor q2 resolution. Thus requiring parameterizations.

  5. Dpen/Ken Kln pln A big advance in precision! • Look for D*D decays. The “signal” is in the Dm plot. • 3 bins in q2 to get form factor info. • Include peaking and non peaking backgrounds Consistent w/ SU(3) breaking

  6. q2 information in Dpen/Ken Clearly the data does not favor the simple Ds* pole After correcting for smearing Cleo reports these corrected q2 fractions pen Ken Disfavors ISGW2 form by ~4.2s The Cleo 04 pen pole mass is

  7. Dvector mn decays left-handed m+ Two amplitude sums over W polarization using D-matrices right-handed m+ Helicity FF are combinations of the vector and two axial form factors Two numbers parameterize the decay H0(q2), H+(q2), H-(q2) are helicity-basis form factors computable by LQCD...

  8. Interference in D+ K* mn F-B asymmetry -15% F-B asymmetry! matches model Focus “K*” signal Yield 31,254 DataMC K* mn interferes with S- wave Kp and creates a forward-backward asymmetry in the K* decay angle with a mass variationdue to the varying BW phase The S-wave amplitude is about 7% of the (H0) K* BW with a 45o relative phase The same relative phase as LASS (2002)

  9. K*mn form factors Due to interference Incisive tests of the model are possible Results are getting very precise and unquenched calculations for incisive tests of the theory would be very desirable. acoplanarity

  10. Further tests of the K*mn model A dramatic mismatch is seen at very low q2 suggesting a V(q20) problem Generally the model tracks the data rather well… Focus even has a preliminary analysis of the K*0 line shape. G(K*0)is less than PDG by~1.6 MeV w/  errors

  11. The vector/pseudo scalar enigma circa 1993 The 2002 FOCUS result tended to reinstated it by getting a value close to previous K*ln/K2p world average. 0.620.02 G(K*l n)/G(Kpp) muons electrons Form factor ratios were well predicted but the scales were not. The 2002 CLEO result tended to resolve this discrepancyby reporting a larger K*ln/K2p BR

  12. Direct G (D+K*mn / Kmn) Theory Use upstream Ks (~10%) so that both the numerator (Kpmn) and denominator (Ksmn) leave 3 tracks in FOCUS m-strip S-wave corrected

  13. Ds fmn form factor enigma circa 1999 But the (2004) FOCUS measurement has consistent r2 values as well! 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 .

  14. Other results on Ds fmn A highly cut sample is required to remove backgrounds BR relative to fp are consistent Angular projections look fine fmn/ fp NO evidence for s-wave interference in Ds fmn (<4%) of (H0 ) BW

  15. The future of charm SL physics yDoDo, DoK-p+ Extremely clean events! K+ prelimin data (60 pb-1) p+ K- p- Pavlunin APS Talk “yellow book”1 fb-1 U = Emiss - Pmiss MC yellow book1 fb-1 (MC) U = Emiss - Pmiss Cleo-c and Bes III: Run at Y(3770) with high luminosity and a modern detector Closing the neutrino in D pen events The q2 impasse afflicting SL data for the last 20 years should finally be overcome

  16. Summary New CLEO Dpen/Ken result q2< 0.2 F-B asymmetry V(q20) problem D+ K* mn s-wave interference in D+ K* mn Consistent FF for D+ K* mn&Ds+f mn V/PS ratio

  17. SL Physics of the future prelim data Promises of a rosy future with precision neutrino closure 1 fb-1 (MC) U = Emiss - Pmiss

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