Rare and Semileptonic Decays of B and K Mesons

1. Rare and Semileptonic Decays of B and K Mesons Particles and Nuclei International Conference Santa Fe, Oct. 27, 2005 Jeffrey D. Richman University of California, Santa Barbara BABAR Collaboration

2. Outline • Goals and challenges • KLp0nn • The “kaon revolution”: KL p+e-n, |Vus|, and the recalibration of kaon branching fractions • Electroweak penguin/box diagram processes: BK*g, Brg, BXsg and BKl+l-, BK*l+l- • Semileptonic B decays and the measurement of |Vcb |, |Vub |, mb, mc • [Leptonic B decays: Bsm+m-, B+t +nt] • Perspective and conclusions Far too many topics to cover... my apologies! Parallel session talks contain many more details (Bizjak, Godang, Koeneke, Mohapatra,…)

3. Rare and Semileptonic Decays: Goals Rare decay: loop/box process  test SM at 1-loop level  new (heavy) particles can be produced in virtual intermediate states; can compete with SM amps  search for effects of new physics Semileptonic decay: tree diagram  measure |Vij|  determine quark masses, QCD parameters

4. Common theme: understanding dynamics • Amplitude factorizes  single hadronic current • Form factors/QCD parameters can sometimes be extracted from data or be calculated • Precise rate predictions possible for some processes • Methods: HQET, heavy-quark expansions, lattice QCD,… Understanding dynamics is an important goal in itself!

5. CKM matrix: b and s decays are both suppressed! (Wolfenstein parametrization) 5 highlighted Vij: discuss in this talk! unitarity: 6 triangles, all with same area

6. BABAR

7. KLp0nn • KL decay directly measures h (height of unitarity triangle)! • SM prediction: • Use K+p0 e+n measurement to compute hadronic current. Buras, Schwab, & Uhlig, hep-ph/0405132; very small theory errors achievable. E949, PRL 93, 031801 (2004)

8. Preliminary results on KLp0nn from KEK E391a 1. Measure g position and energy in CsI • Prelim. result uses 1.14 x 109KL decays; e=0.73x10-2 • So far, only very small fraction of data used. • No events observed in signal box • E391a goal • Proposal in preparation for follow-on experiment at J-PARC 2. Reconstruct decay vertex assuming Mgg=M(p0). 3. Signature: z(vertex) and pt Major backgrounds

9. Kpen , |Vus|, and the “kaon revolution” Review of Particle Properties, 2002 experiment: BR, tK KLen: 1 K+en:1/2 form factor theory: q2=0 exp’t: shape I-spin corr. for K+ decay long distance rad. corrections short distance radiative corr. Leutwyler & Roos, Z.Phys.25, 91 (1984) Cirigliano et al., Eur.Phys. J C35, 53 (2004) Andre, hep-ph/0406006 Sirlin, Nucl. Phys. B196, 83 (1982) +other work in progress

10. Recalibration of KL branching fractions • KTeV measured 6 largest KL modes [PRL 93, 181802-1 (2004)] • Account for 99.93% of decays; 5 ratios of branching fractions • 105-106 events/mode; careful treatment of radiation from electrons. • Measurement of KL semilep form factors (1.7%-4.2% shifts) [hep- ex/0406003, 0406006] E. Blucher, Lepton-Photon 2005 fit to all new meas.

11. Extraction of |Vus| E. Blucher, Lepton-Photon 2005 • Average of recent results: • KLOE, KTeV, NA48, ISTRA+ • correlations taken into account Competing method: G(K+m+n) [KLOE, hep-ex/0509045] + lattice [MILC, PRD70, 114501 (2004); Marciano, PRL93, 231803 (2004)]

12. Radiative penguin decays of B mesons Now it’s a physics program! Observation of BK* g CLEO II (1993): Loops in B decays! PRL 71, 674 (1993) cited >500 times!

13. Observation of the bdgdecaysBr (w) g Belle, 386 M BB hep-ex/0506079 BABAR, 211M BB PRL 94, 011801 (2005) 8.2 evts 20.8 evts Ali, Lunghi, Parkhomenko, PLB 595, 323 (2004) 5.9 evts Belle good agreement w/global CKM fit Belle

14. BABARPRD 72, 052004 (2005) Inclusive BXs gDecay • Canonical process for testing the SM at 1 loop level • Provides powerful constraints on new physics models • Major effort by theory community to compute QCD and EW corrections; NLL calculation complete; NNLL calculation forseen Hurth, Lunghi, Porod, Nucl. Phys. B 704, 56 (2005); see also Neubert, Eur.Phys. J C40, 165 (2005); Buras et al., Nucl.Phys. B631, 219 (2002) HFAG July 2005 Belle, PRL93, 061803 (2004) fully incl. sum of 38 excl. modes

15. Moments of BXsg Photon Energy Spectrum (see talk by Karsten Koeneke, Section VI.4) Used in determination of mb, |Vcb |, and | Vub | 2nd Moment (GeV2) 1st Moment (GeV) Minimum Eγ (GeV) Minimum Eγ (GeV) hep-ex/0507001 D. Benson, I.I. Bigi and N. Ultrasev Nucl. Phys. B 710, 371-401 (2005)

16. Electroweak penguins BKl+l- and BK*l+l- • With l+l- pair, can produce both pseudoscalar and vector mesons • New physics can affect both rate and kinematic distributions. BABAR hep-ex/0507005 (229M BB) Belle prelim. hep-ex/0410006, 0508009

17. BKl+l- and BK*l+l- : branching fractions Theory errors mainly due to form factors. (rarest observed B decay) pole at low q2

18. BK*l+l-: Lepton F-B Asymmetry Lepton angular distribution in l+ l- rest frame Belle: lepton A(FB) [raw] 386 M BB hep-ex/0508009 SM NP scenarios constraints on Wilson coeffs describing short-distance physics

19. chromomagnetic expec. value Darwin term spin-orbit kinetic expec. value kinetic scheme Benson, Bigi, Mannel & Uraltsev, hep-ph/0410080 Gambino & Uraltsev, Eur.Phys.J. C34, 181 (2004) Precision measurement of |Vcb|and the atomic physics of B mesons • inclusive semileptonic rate • inclusive lepton-energy spectrum (moments) • inclusive recoil hadron mass spectrum (moments) Observables |Vcb|, mb, mc, mp , mG , rD , rLS Heavy-quark expansion theory params: BABAR, PRL 93, 011803 (2004)

20. |Vcb| and inclusive parameters from BXcln and BXsg • Buchmuller and Flacher; hep-ph/0507253 • Fit to moments of inclusive distributions in BXcln and BXsg • Experiments: BABAR, Belle, CDF, CLEO, DELPHI all moments all moments D*ln zero rec. <2% errors kinetic mass scheme

21. Measuring |Vub | is hard, but the error is shrinking Large bc background; suppression cuts introduce dependence on theory predictions for kinematic distributions. Fully reconstructed B recoil analysis Lepton spectrum endpoint analysis p BABARhep-ex/0509040 Breco e- D* e+ n Brecoil Xu continuum data (off res) l Belle hep-ex/0505088 bc subtraction bu

22. |Vub | inclusive measurements Eℓ endpoint • Key CKM constraint • Use mb and QCD parameters extracted from inclusive BXcln and BXsg spectra. • Many methods with uncertainties around 10%. • Uncertainty from mb has been reduced to 4.5%. • With more data, the |Vub| uncertainties could be pushed down to 5%-6.5%. Eℓvs. q2 mX mXvs. q2 mb, theory expt

23. Measuring |Vub| using Bpln and lattice QCD B0p+ l-nform-factor predictions f+(q2) is relevant form factor for Bpln (l=e, m) Fermilab/MILC HPQCD At fixed q2, lepton momentum spectrum is exactly known in this mode, since only one form factor. HPQCD: hep-lat/0408019 restricted q2 range Fermilab/MILC: hep-lat/0409116

24. Bpln: branching fraction and q2 distribution Becher and Hill, hep-ph/0509090 Relatively flat distribution in spite of rapidly changing form factor. Consequence of p3 factor in decay rate. HFAG averages

25. Search for Bsm+m- and B0l+l- • Highly suppressed in the SM • Bdsuppressed by |Vtd/Vts|2 • No SM signals expected at Tevatron or at B factories, but can have large enhancements from new physics. Strong correlation with neutralino-proton cross section in mSUGRA! Beck,Kim,Ko hep-ph/0406033

26. Perspective/Conclusions • K Physics • Early results from 1st dedicated KLp0nn experiment • KL branching fractions re-measured: 5% to 8% shifts • |Vus| shift: +3% • Unitarity of 1st row of CKM matrix looks better; work in progress on |Vud| • B Physics • Brg observed; provides interesting constraint on |Vtd|/|Vts| • Many bsg and bsl+l- modes observed; studies of kinematic distributions are especially interesting • |Vcb| measured to 2% via inclusive method; mb well determined • |Vub| precision now below 10%. • Keep pushing inclusive vs. exclusive crosscheck! • Leptonic B decays providing interesting sensitivity to new physics • B factories will push to 1 ab-1. Many more results to come!

27. Backup slides

28. Huge program on B decays to charmless hadronic final states... see H. Jawahery talk for hadronic bs decays (10-6)

29. Observation of the bdgdecaysBr (w) g Belle BABAR Note: naïve expectation is G(B+r+g)=2 G(B0r0g)=2 G(B0wg) BABAR/Belle discrepancy on B0r0g; to be resolved with more data.

30. BABAR

31. BXsg New Physics Sensitivity • Constraints on Two Higgs doublet models (Type II) • mH = charged Higgs mass • tanb = ratio of vacuum expectation values of the two doublets • Hou [PRD48, 2342 (1993)], Gambino & Misiak [Nucl. Phys B611, 338 (2001)], Neubert [Eur. Phys. J C40, 165 (2005)]. future projections current BABAR data 90% C.L. allowed regions (above lines) 2 ab-1 1 ab-1 0.5 ab-1 combined

32. Search for leptonic B-decays • helicity suppressed • CKM suppressed (Vub) • annihilation diagram • tree-level sensitivity to H- Non-relativistic mesons (2 heavy quarks): Predicted leptonic branching fractions: (|Vub| = 0.0039, fB= 200 MeV)

33. Search for B-t-n BABAR, hep-ex 0507069 • t reconstruction: a major challenge • fully reconstruct other B in event • require lepton (or pion) and no additional observed energy (2-3n) e- Eextra Belle, hep-ex/0507034 Backgrnd e+ Backgrnd t- nt nt Expected signal x10 e- ne

34. Search for Bsm+m- and B0l+l- • Highly suppressed in the SM • Bdsuppressed by |Vtd/Vts|2 • No SM signals expected at Tevatron or at B factories, but can have large enhancements from new physics. 90% C.L.

35. Bsm+m-and SUSY Dermisek, Raby, Roszkowski, Ruiz de Austri, hep-ph/0507233 Baek, Kim, Ko, hep-ph/0406033 Dark matter cross section s(cp) vs. B(Bsm+m-).

36. Experiment vs. Lattice: DKln form factor

37. Measuring |Vub| using Bpln Projection to 1 ab-1 (data taken to be on BK fit curve from present measurement). BABAR PRD 72, 051102 (2005) In the high q2 region alone, we will measure the branching fraction with an uncertainty of (6-7)% , or (3-3.5)% uncertainty on |Vub |. Lattice theorists expect to reach 6%, so exclusive/inclusive will be similar.

38. Precision measurement of |Vcb|: fits to moments of lepton spectrum and hadron recoil spectrum BABAR PRL 93:011803 (2004) ● = used, ○ = unusedin the nominal fit mX moments BABAR c2/ndf = 20/15 Eℓmoments Red line: OPE fitYellow band: theory errors

39. Muon decay: a prototype low-energy weak decay W-mediated b-quark transitions have several key features in common with muon decay. Very strong dependence of decay rate on mass! (ignoring QED radiative corrections)