B,D

1. B,D p,D,K,…

2. El q2 = pl2+pn2 D, MX Semileptonic B and D Meson Decays • Study semileptonic B and D meson decays: BXc,uln , D Xd,sl n • Leptonicand hadronic currents factorize! • Experimental approaches: inclusiveor exclusive (B → pln, D→ Kln, ...) • electroweak interaction coupling • |Vcb| , |Vub| or |Vcs| ,|Vcd| • strong interaction •  meson structure Inclusive Decays • Large signal rate, high bkg • Total rate calculated with HQE • Need Shape Function (b-quark motion in B meson)  smears kin. spectra • SF param. from b  sg or b  cln. Exclusive Decays • Low signal rate, better bkg reduction • Need Form Factors to describe hadronization process • Measurement as function of q2, angles

3. high mass charm states Mx2[GeV2/c4] Enough d.o.f. to fit 8 parameters: needed for |Vub| |Vcb| from Ee and MX Moments • Measure moments of lepton momentum and hadronic mass spectra from B  Xcl n • 1st to 4th MX moments , 0th to 3rd Ee moments (as function of min. cut on Ee) HQE fit theo. error band Global fit to Ee , MX , Eg (bsg) moments: |Vcb| = (41.58 + 0.45 +0.58) x 10-3 mb (kin) = 4.591 ± 0.040 GeV mp2(kin) = 0.406 ± 0.042 GeV |Vcb| @ 1.7% mb < 1% mc @ 5%

4. |Vcb| from B  D* l n Phase space Form factor • Decay rate is: • f (1) = 1 in the heavy quark limit; lattice QCD says: • Shape of f(w) expressed by r2 (slope at w = 1) and form factor ratios R1, R2. Curvature from analyticity. • Measure decay angles ql , qV , c . Fit3Ddistribution in bins of w to extact r2, R1, R2 . Here we use w = D* boost in B rest frame Hashimoto et al, PRD 66 (2002) 014503 Caprini, Lellouch, Neubert Nucl. Phys. B 530, 153 (1998)

5. stat. MC stat. syst. B  D* l n Form Factors & |Vcb| 1D projections of fit result: 88M BB w cosql cosqV c Factor 5 improvement on FF uncertainty from previous CLEO measurement (1996!) Total systematic error on |Vcb| : 4.5%  3.5% BABAR

6. Inclusive |Vub| from Lepton Endpoint BABAR 88M BB Data MC bkgb  cln Data – bkg MC signalb  uln +0.42 –0.38SF |Vub|=(4.44±0.25exp ±0.22theo)´10-3 • Study inclusive decays B  Xuln • Need to fight large charm bkg from B  Xcln • Low S/B  need accurate bkg subtraction • Restrict phase space (problematic for HQE !)  shape function becomes important • Select events with high-E lepton: 2.0 < Eℓ < 2.6 GeV • Lower Eℓ cut below charm threshold • Larger acceptance, smaller theoretical error fully corrected spectrum

7. p Btag signal e- D* e+ n Bsignal Xu l theory uncertainties +0.46 –0.38SF |Vub|=(4.65±0.34exp ±0.23theo)´10-3 Inclusive |Vub| with Hadronic B tag • Hadronic B tag: Fully reconstruct one Btag in hadronic decay mode  know momentum, flavor, charge of other Bsignal MX < 1.7 GeV and q2 > 7 GeV2 • New “shape function-independent” approach: • Combine b cln rate with b  sg spectrum • Or measure full MX spectrum Leibovich, Low, Rothstein hep-ph/0005124,0105066 MX<1.67 GeV: |Vub| = (4.43 ± 0.45exp± 0.29theo)×10-3  Cut on MX 

8. mES (GeV) disfavors ISGW II quark model 83 x 106 BB Data Signal MC Comb. Sig. Crossfeed bcln qq |Vub| from B p l n • Untagged analysis: Reconstruct neutrino from missing 4-momentum of event • Experimentally: • Good S/B ratio, untagged & tagged analyses • Measure q2 dependence of form factor • Theoretically: • Complementary to inclusive approach • Form-factor norm. dominates error on |Vub| Form Factor LQCD2  +0.89 –0.53FF |Vub| = (3.82 ±0.26exp ) ´10-3

9. D Testing Theory with D  K/p l n • Study D-meson decays from e+ e- cc with high statistics • Tag one c quark via full reconstruction of D(*) meson • Dramatically reduces bkgfrom u, d, s and B mesons mpole = 1.854 ± 0.016 ± 0.020 apole = 0.43 ± 0.03 ± 0.04 |Vcs| from unitarity  determine |f+(q2)| |f+(q2)|from LQCD  determine |Vcs| Goal: measure ratio B(D  pln) / B(D  Kln)  compare with lattice |f+p(q2)| / |f+K(q2)| Charm SL decays provide high-quarlity lattice calibration. Techniques validated by charm decays can be applied to beauty decays!

10. + + + + c = + |fDs|2 m + s |Vcs|2 Nmn = 489±55 Ds→mn signal Preliminary 230fb-1 DS mn and Decay Constant fDs • Leptonic decay proceeding through weak annihilation of quarks • Form factor f (q2 = M2Ds) decay constant fDs • Reconstruct signal c quark via • D*SDSgm n g • Normalize to Dsf p : stat syst Ds→fp LQCD: Aubin et al. PRL 95 122002 (2005) Validates LQCD predictions at 10% level

11. Conclusions • BABAR has broad program of semileptonic/leptonic B decays and dominates this sector. SLAC plays a leading role here. • Much progress in the last 1-2 years: |Vcb|  2%, |Vub|  7% , form factors, … • BABAR started to make use of their large D-meson samples • Measurements ofB and D semileptonic decays have reached precision to allow critical comparisons with lattice calculations: Form Factors & HQE Parameters CKM constraints (CP conserving) 2005  2006 fDs results: