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Fully leptonic and semileptonic decay

Fully leptonic and semileptonic decay. CLEO-c and BESIII. Joint workshop on charm, QCD and tau physics. Jan. 13-15, 2004 in Beijing, China. Jim Wiss University of Illinois. Acknowledgements and Full Disclosure This talk is from the perspective of a brand new CLEO-c member

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Fully leptonic and semileptonic decay

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  1. Fully leptonic and semileptonic decay CLEO-c and BESIII Joint workshop on charm, QCD and tau physics Jan. 13-15, 2004 in Beijing, China Jim WissUniversity of Illinois • Acknowledgements and Full Disclosure • This talk is from the perspective of a brand new CLEO-c member • It borrows very heavily from an excellent longer talk of Ian Shipsey • I have worked on semileptonic decays from the Fermilab FOCUS (fixed target) experiment with vastly different systematics and very complementary techniques. Allowed transition

  2. Hi impact leptonic and semileptonic physics The most uncertain CKM elements are |Vtd|and |Vub|. Both uncertainties are dominated by systematics on calculating hadronic effects that can be significantly reduced by calibrating LQCD on related charm decays. D+ mn D0 pln An impressive check of the unitarity triangle.

  3. D meson Decay Constants |VCKM|2 |fD|2 l n In a pseudoscalar D meson decay: c and q annihilate Helicity suppression B(D+l)/ D+ : fD+|Vcd| B(DS l)/ Ds : fDs|Vcs| * Charm meson lifetimes known 0.3-2% * 3 generation unitarity Vcs, (Vcd) known to 0.1% (1.1%)  fD+fDs

  4. Improving knowledge Vtd using D+mn (ICHEP02) 1.2% ~15% (LQCD) Lattice predicts fB/fD with small errors precision measurement of fD precision estimates of fB precision determination of Vtd

  5. D meson Decay Constants Current Status fDs Values from Ds Common systematic error from B(Ds) fD+ < 290 MeV @ 90% CL (Mark III) Estimated BR usingfDs=260 fD=220 fB=200 MeV 14% relative error

  6. fD+ from Absolute Br(D+ m+n) MC D+ mn PDG 3fb-1 mf Ds 17% 1.9% tf Ds 33% 1.6% mf D+ UL 2.3% • Fully reconstruct one D (tag) • Require one additional charged track and no additional photons Huge improvement over existing knowledge!

  7. Probing the hadronic current

  8. Exclusive Charm Semileptonic Signal Yields in 3 fb-1 yellow book yields with 3 fb-1 *Focus K*mn FF sample The BESIII yields are likely to be 5 to 10 times larger!

  9. Improvements in charm semileptonic branching ratios from 3 fb-1 Threshold running can dramatically improve on the PDG value of dB/B for every D+ and D0 semileptonic branching ratio.

  10. Importance of absolute charm semileptonic decay rates. |VCKM|2 |f(q2)|2 I. Absolute magnitude & shape of form factors are a stringent test of theory. II. Absolute charm semileptonic rate gives direct measurements of Vcd and Vcs. III Key input to precise Vub vital CKM cross check of sin2  B l u b  D l c d 1) Measure D form factor in Dl. Calibrate LQCD uncertainties . 2) Extract Vub at BaBar/Belle using calibrated LQCD calc. of B form factor. 3) But: need absolute Br(D l) and high quality f(q2) data and neither exist

  11. f(q2) models of the past is easiest for LQCD cleanest theory highest rate A major disconnect between experiment and theory afflicts published data An incisive test of LQCD requires one to measure f(q2) where there is still rate and compare in a theoretically controlled q2 region Previous data had low rates and terrible q2 resolution which required a parametric form for meaningful measurement ISGW

  12. Measuring q2 evolution “yellow book”1 fb-1 MC At present, K*ln data fits to the pole form return poles slightly lower than Ds*. But past studies were compromised by poor q2 resolution and control of backgrounds at low visible mass and K*ln is not an optimal state... pln probe q2 dependence nearly up to the spectroscopic pole! DK*ln Signals at the y (3770) will be clean , copious, and well resolved in q2

  13. Pole versus ISGW form in Dpen hep-ph/0101023 Lattice The lattice can now calculate f+ as a function of q2. Dpen provides a powerful test of the lattice predictions. Once validated, the lattice can be used with confidence in the extraction of CKM matrix. for both B’s and D’s better sys MC yellow book1 fb-1

  14. Dvector l n decays left-handed m+ right-handed m+ Two amplitude sums over W polarization (“mass terms”) Wigner D-matrices A 4-body decay requires 5 kinematic variables: Three angles and two masses. MKpMW2 q2 H0(q2), H+(q2), H-(q2) are helicity-basis form factors computable by LQCDThese evolve according to vector and axial pole forms

  15. Form Factor Ratios The H+ , H- , and H0 form factors are various combinations of vector and axial pole formswhich are parameterized as spectroscopic poles. Nominal spectroscopic pole masses The intensity is then described by just 2 numbers rV rv/ rv= 4.6% r2/ r2 = 9.2% Focus sys+stat YB 1 fb-1 stat r2 Although ratios of form factors are known precisely, A1(0) , A2(0) and V(0) measurement requires knowledge of (1) absolute BR (2) charm lifetimes (3) reliance on q2 model Latest LGT: Becirevic (ICHEP02) RV = 1.55  0.11

  16. Hadronic complications in K*l n DataMC Yield 31,254 constant s-wave The Kpln process consists of both K* ln and an interfering, s-wave component which creates a forward-backward asymmetry in the K* decay angle with a distinctive mass variation.

  17. Both good news and bad news eventsCosV const ampLASS amp M(Kp) A very naive calculation Estimated errors for a 31 000 event sample |amp|2 Adds additional complications such as amplitude and phase variation, an additional helicity form factor etc. But allows additional handles on the relevant hadronic physics such as: 1. Studies of the I=1/2 s-wave phase variation 2. Detailed studies of the K* line shape Phase (deg)

  18. Great to extend data to Drln Kinematic projections from 1 fb-11 Very clean2 Great resolution3 Good efficiency MC MC K*l n r l n It would very interesting to compare form factors in r l nto K*l n and search for s-wave interference in r l n MC MC BESIII could study S-wave interference in rln interference with half the (tagged) statistics as used in the Focus K*mn study

  19. Enigma #1: G (DK*ln) circa 1993 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 discrepancy.The 2002 FOCUS result tended to reinstated it. A1 follows from G (K*mn) measured from K*ln/ Kpp using the Kpp BF and D+ lifetime. This can then be compared with LGT prediction

  20. Enigma #2: Dsfln form factors circa 1999 CL (rV) = 44.3% CL(r2) = 21.5% It was anticipated that the form factor ratios for Dsflnshould be within 10% of those for D K*ln . Until just recently, it looked like rV values were consistent but r2 for Dsflnwas  a factor of two higher than that for D K*ln . The new Focus data(hep-ex/0401001)challenges this.

  21. Determining Vcs and Vcd combine semileptonic and leptonic decays eliminating V CKM (D+ ln) / (D+ ln) independent of Vcd Test rate predictions at ~4% (Dsln) / (Dsln) independent of Vcs Test rate predictions at ~ 4.5% Test amplitudes at 2% Stringent test of theory! If theory passes the test….. Vcs /Vcs = 1.6% (now: 11%) Vcd /Vcd = 1.7% (now: 7%) I Use CLEO-c validated lattice to calc. B semileptonic form factor, then B factories can use Br/p/h/lv for precise Vub II

  22. Improving unconstrained CKM elements (Snowmass E2 WG) Without invoking powerful unitarity constraints, many CKM elements are relatively poorly known. PDG PDG CLEO-c data and LQCD B Factory/Tevatron Data & CLEO-c Lattice Validation With lattice validation from threshold e+e- running allows for much better unitarity tests |Vcd|2 + |Vcs|2 + |Vcb|2 = 1 ?? CLEO –c: test to ~3% (if theory D K/ln good to few %)

  23. Summary • Leptonic Decay • Dramatic improvements in fDs and first measurements of fD+ at 2% • Plays a crucial role in Vtd when combined with mixing • Pseudoscalar semileptonic decay • Unparalleled cleanliness in f+ form factor measurement in D pln • Removereliance of f(q2) models to bridge theory and experiment • Pole dominance and ISGW forms can be easily distinguished • Provide clean calibration of f+ : Both value and q2 evolution predicted by LQCD • Provides crucial calibration f+ to use B  pln to measure Vub • Vector semileptonic decay • Improvement in rV and r2 parameters • Unique advantages in determining A1(q2), A2(q2) , V(q2) • q2 dependence for the first time • Hadronic complications / opportunities due to s-wave interference • Settle two long term experimental enigmas • The K*ln/Kln problem • The Ds  fln versus D+  K*ln r2 inconsistency • Direct measurements of Vcs , Vcd and incisive unitarity tests

  24. Interplay between semileptonic , leptonic charm and improved beauty data and LQCD • Crucial Validation of Lattice QCD: Lattice QCD will be able to calculate with accuracies of 1-2%. The CLEO-c decay constant and semileptonic data will provide a “golden,” & timely test. B Factories only ~2005 Imagine a world Where we have theoretical mastery of non- perturbative QCD at the 2% level Theory errors = 2%

  25. Question slides ??

  26. Inclusive Semileptonic Decays • Currently SLof all D mesons are consistent with being equal: • Threshold: the best place to measure inclusive semileptonic branching ratios Hadronic tag 30 improvement ! HQE predicts the near equality of SL for D+, D0 and Ds but large 1/mc corrections and duality violations are a concern.CLEO-c inclusive rate and spectral shape provide precision test of 1/mc expansion

  27. CLEO-c Yellow Book Run Plan Year 1 y(3770) – 3 fb-1 30 million DD events, 6 million tagged D decays (310 times MARK III) C L E O - c Year 2 MeV – 3 fb-1 1.5 million DsDs events, 0.3 million tagged Ds decays (480 times MARK III, 130 times BES) Year 3 y(3100), 1 fb-1 –1 Billion J/y decays (170 times MARK III, 20 times BES II) A 3 year program …and about to begin the year 1 program with 50 pb-1 @ y(3770)X5 Mark III with a state of the art detector that is understood at a precision level, and has proven itself with pioneering measurements of Vub, Vcb, & radiative penguins, discovery of the Y D states and DsJ(2463) and many more.

  28. s(DoDo) = 5.8 nb s(D+D-) = 4.2 nb s(Ds Ds) = 0.5 nb Unique Opportunities at Charm Thresholds (3770) DD s ~4140  DsDs R (units of s(m+m-)) s(m+m-)= 5.4 nb at 4 GeV

  29. Decay constants are important in many processes

  30. CKM Facts

  31. Vub/Vub 25% Vud/Vud 0.1% Vus/Vus =1% l l e B n n K n n p p  Vcs/Vcs =16% Vcb/Vcb 5% Vcd/Vcd 7% l D n l K B n l D D n p Vtb/Vtb 29% W Vtd/Vtd =36% Vts/Vts 39% t b Bd Bd Bs Bs Precision Quark Flavor Physics Goal for the decade: high precision measurements of Vub, Vcb, Vts, Vtd, Vcs, Vcd, & associated phases.Over-constrain the “Unitarity Triangles” - Inconsistencies  New physics ! CKM Matrix Current Status: Nc Wcs Many experiments will contribute. Measurement of absolute charm branching ratios At CLEO-c will enable precise new measurements at Bfactories/Tevatron to be translated into greatly improved CKM precision.

  32. Charm Facilities Future charm data sets

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