1 Charm Semileptonic Decay The importance of charm SL decay Pseudoscalar l decay Vector l decay –Analysis of D  K*  –The V/PS enigma :  (D+  K*  / K  –The D s  form factor enigma The future of SL decay – Cleo-c / Bes III  (3770) running Jim Wiss Univ of Illinois HQL2004 June 2, 2004 Apologies for all the important and fascinating results that I had to skip Featuring results from

2 Charm semileptonic decay as tests of LQCD Apart from form factors, these decays can be computed using perturbation theory and are first order in CKM elements The form factors incorporate hadronic complications and can be calculated via non-perturbative Lattice QCD. 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  decays Provides a way to either measure CKM elements or to verify f + (q 2 ) calculations...But a major disconnect exists between experiment and theory. Theory works best where experiment works worse. cleanest theory highest rate ISGW Two forms are used to parameterize f + (q 2 ) pole These should be among the first unquenched lattice calculations... is easiest for LQCD Kaon at rest in D frame

4 Comparing pole versus ISGW form in D  e D  e should provide a powerful test of future lattice predictions Lattice hep-ph/ better sys as P   0 Unfortunately present LGT offers very little discrimination between the two common forms...where differences are dramatic.  e decay gets quite close to the D* pole... But past  e  signals have severe backgrounds and poor q 2 resolution. Thus requiring parameterizations. The lattice can now calculate f+ as a function of q 2.

5 D  e /Ke Consistent w/ SU(3) breaking Look for D*  D decays. The “ signal ” is in the  m plot. 3 bins in q 2 to get form factor info. Include peaking and non peaking backgrounds A big advance in precision! Kl  l

6 q 2 information in D  e /Ke The Cleo 04  e pole mass is After correcting for smearing Cleo reports these corrected q 2 fractions  e Ke Clearly the data does not favor the simple Ds* pole Disfavors ISGW2 form by ~4.2 

7 D  vector  decays H 0 (q 2 ), H + (q 2 ), H - (q 2 ) are helicity-basis form factors computable by LQCD... right-handed  + left-handed  + Two amplitude sums over W polarization using D-matrices Helicity FF are combinations of the vector and two axial form factors Two numbers parameterize the decay

8 Interference in D +  K*  Yield 31,254 Data MC K*  interferes with S- wave K  and creates a forward-backward asymmetry in the K* decay angle with a mass variation due to the varying BW phase (2002) F-B asymmetry The S-wave amplitude is about 7% of the (H 0 ) K* BW with a 45 o relative phase Focus “ K* ” signal The same relative phase as LASS matches model -15% F-B asymmetry!

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

10 Further tests of the K*  model Generally the model tracks the data rather well … A dramatic mismatch is seen at very low q 2 suggesting a V(q 2  0) problem Focus even has a preliminary analysis of the K* 0 line shape.  K* 0 )  is less than PDG by  ~1.6 MeV w/  errors

11 The vector/pseudo scalar enigma  K*l  /  K  muonselectrons 0.62  0.02 The 2002 CLEO result tended to resolve this discrepancy by reporting a larger K*l /K2  BR circa 1993 Form factor ratios were well predicted but the scales were not. The 2002 FOCUS result tended to reinstated it by getting a value close to previous K*l /K2  world average.

Direct  (D+  K*  / K  Use upstream K s (~10%) so that both the numerator (K  ) and denominator (K s  ) leave 3 tracks in FOCUS  -strip Theory S-wave corrected

13 D s  form factor enigma Theoretically the Ds  l form factor should be within 10% of D+  K*l The rV values were consistent but r2 for Ds  l was  2  higher than D+  K*l circa 1999 But the (2004) FOCUS measurement has consistent r2 values as well! D s   versus D+  K*l

14 Other results on D s  NO evidence for s-wave interference in Ds  (<4%) of (H 0 ) BW Angular projections look fine  BR relative to  are consistent A highly cut sample is required to remove backgrounds

15 The future of charm SL physics “yellow book” 1 fb -1 MC U = E miss - P miss Closing the neutrino in D  e events Cleo-c and Bes III: Run at  (3770) with high luminosity and a modern detector  D o D o, D o  K -  + K-K- K+K+ ++  Extremely clean events! U = E miss - P miss prelimin data (60 pb -1 ) Pavlunin APS Talk yellow book 1 fb -1 (MC) The q 2 impasse afflicting SL data for the last 20 years should finally be overcome

16 Summary Consistent FF for D +  K*  & D s +   s-wave interference in D +  K*  F-B asymmetry V(q 2  0) problem D +  K*  q 2 < 0.2 New CLEO D  e /Ke  result V/PS ratio

17 1 fb -1 (MC) U = E miss - P miss prelim data SL Physics of the future Promises of a rosy future with precision neutrino closure