Radiative and Electroweak Penguin Decays of B Mesons Jeffrey D. Richman University of California, Santa Barbara B A B AR Collaboration 11 th International Conference on B Physics at Hadron Machines Oxford, Sept. 28, 2006

Outline Overview: a little history, physics goals, and challenges B +   +  B 0   0  B 0   and the  extraction of |V td /V ts | B  K l + l - and B  K* l + l - : search for new physics using the lepton forward-backward asymmetry Inclusive B  X s  branching fraction measurements and extraction of heavy-quark-expansion parameters (including m b ) using the E  spectrum Conclusions Apologies for not covering all results on radiative/electroweak penguin decays in this talk!

Radiative penguin decays of B mesons Observation of B  K*  CLEO II (1993): Loops in B decays! PRL 71, 674 (1993): cited >500 times! Now it’s a physics program! Rare, but not all that rare!

Probe SM at 1-loop level (flavor-changing neutral currents) Search for new physics: can affect amplitudes at leading order As for semileptonic decays, the amplitude in EM/EW penguins involves only one hadronic current  factorizes. What can we learn from b  s, d transitions? (+ W + W - box diagram) (dominated by t quark)

Understand QCD dynamics: single hadronic current allows us to isolate non-perturbative parameters in well-defined way. Can be related to same/similar parameters for other decays.  Exclusive decays: decay form factors f i (q 2 ). b  s transition is similar to b  u (heavy-to-light decays)  Inclusive decays: parameters of heavy-quark expansion (m b,   2,…); important input for |V ub |, |V cb | extractions. Measure/constrain CKM elements (|V td /V ts |): if info on hadronic parameters is available from data, theory, or both. What can we learn from b  s,d transitions?

Ali, Lunghi, Parkhomenko, PLB 595, 323 (2004) [for I-spin avg.] I-spin (  ), quark model (  ). Expect small I-spin violation: (1.1+/-3.9)%. Ball and Zwicky, JHEP 0604, 046 (2006) Ball and Zwicky, hep-ph/ W annihilation diagram (small) Observation of b  d  and Measurement of |V td /V ts |

Measurement of b  d  Decays (Belle) Signal BK*BK* continuum background Belle, PRL 96, (2006); 386 M BB. Good particle ID is critical in this measurement to suppress B  K*  feed- down.

Measurement of b  d  Decays (B A B AR ) signal bkgnd signal + bkgnd BABAR, hep-ex/ , 347 M BB B++B++ B++B++ B 0   0  B00B00 projections of 4-D fit

Comparison of b  d  Branching Fractions Mode B A B AR (10 -6 ) (6.3  signif.) Belle (10 -6 ) (5.1  signif.) PRL 96, (2006). preliminary; hep-ex/ CKM fitter includes CDF B s mixing result. Error on CKM Fitter prediction includes uncert. on B  V  form-factor ratio. I-spin consistency?

Extracting |V td /V ts | from b  d  Decays Belle, PRL 96, (2006). BABAR, hep-ex/ (preliminary) (used CDF hep-ex/ ) Consistent within errors! courtesy M. Bona (UTfit collab.) Theoretical uncertainties already or soon limiting both approaches. CDF, hep-ex/ (preliminary) exptthy expt thy

B  Kl + l - and B  K*l + l - in the SM and Beyond Photon penguin 3-body decays  dependence of rate on kinematic variables can be used to study the different amplitudes and their interference effects. The mode B  Kl + l - is allowed as well as B  K*l + l - (B  K  forbidden by conservation of angular momentum). Z penguin W + W - box

B  K*l + l - Dalitz plot Can see A FB behavior and q 2 dependence from the Dalitz plot Note: B  Kl+l- is expected to have very small A FB, even in presence of new physics; effectively provides a crosscheck. effect of  pole Standard Model Prediction

Amplitude for B  K*l + l - Short-distance physics encoded in C i ’s (Wilson coefficients); calculated at NNLO in SM: Interference terms generate asymmetries in lepton angular distribution over most of q 2 range. C i ’s can be affected by new physics; enters at same order as SM amp. mix of Z-penguin, W + W - box photon penguin dom. at v. low q 2 Kruger and Matias; PRD 71, (2005) Ali et al., PRD 61, (2000)

Form Factors and Observables Long distance QCD physics is mainly described in terms of form factors, which are functions of 4 semileptonic form factors: A 1, A 2, V, A 0 (similar to B  D*l, B   l  3 penguin form factors: T 1, T 2, T 3 Form factor uncertainies  35% uncertainty in rate predictions. large s

Predictions for A FB in B  K*l + l - : SM and beyond Standard Model s 0 : Ali, Kramer, Zhu, hep-ph/

B A B AR, PRD 73, (2006) 229 M BB B  Kl + l - and B  K*l + l - Signals from B A B AR (6.6 , rarest observed B decay) (5.7  )

B  K ( * ) l + l - Signals from Belle Belle, PRL 96, (2006) 386 M BB (Data sample used for study of Wilson coefficients)

B  Kl + l - and B  K*l + l - branching fractionsMode B A B AR (10 -6 ) [208 fb -1 ] Belle (10 -6 ) [253 fb -1 ] preliminary, hep-ex/ PRD 73, (2006) Inclusive: HFAG avg.

B  K*l + l - : B A B AR results on K* polarization SM K* polarization Theory predictions in graphs: Ali et al., PRD 66, (2002); Ball and Zwicky, PRD 71, (2005). Data apply in 2 bins of q 2 high q 2 low q 2 J/  (vetoed) Polarization consistent with SM, but doesn’t discriminate against new physics scenarios with current data sample. BABAR, PRD 73, (2006) SM

B  K*l + l - : B A B AR results on A FB and  L SM q 2 range (GeV 2 ) A FB FLFL Data excluded at 3.6  ! Any A FB 2.7  use in 2 bins of q 2 (A FB =0 in SM and many BSM)

: B  K*l + l - : Belle results on A FB Belle, PRL 96, (2006) best fit with A 7 fixed to SM for reference:

B  K*l + l - : Belle results on Wilson coefficients fix |A 7 | to SM (B  X s  ) fit for A 9 /A 7 and A 10 /A 7 data consistent with SM quadrants I, III excluded at 98.2% C.L. SM fit A 10 >0 (A i are real and constant; q 2 dep. corrections fixed to theory) Fit q 2 and cos  l for need A 9 A 10 <0 to get A FB >0 in upper q 2 region allowed excluded

Inclusive B  X s  Canonical process for studying b  s transition. Theory uncertainties currently at 10% level (NLO); pushing toward 5% (NNLO). Huge theoretical effort to predict branching fraction & photon energy spectrum. Also predictions for CP and I-spin violation. Spectrum is insensitive to new physics but is sensitive to m b and Fermi motion of b-quark (“shape function”). T. Hurth, E. Lunghi, W. Porod, Nucl. Phys. B 704, 56 (2005). M. Misiak and M. Steinhauser, hep-ph/ NNLO M. Neubert, Eur. Phys. J. C 40, 165 (2005). all for New!

Challenges of measuring inclusive B  X s  Weak experimental signature: single high-energy photon + event- shape cuts. Huge background from  0 ’s and  ’s! Difficult to carry analysis down to E  < 2.0 GeV. Want to push toward 5% precision to match the expected precision of NNLO calculations. MethodAdvantagesDisadvantages Fully inclusive Don’t reconstruct X s Closest correspondence to inclusive B(B  X s  ). Weak kinematic constraints  larger background E  known in Y(4S) frame, not B frame (smearing).  (E   MeV Sum-of-exclusive e.g., BABAR: 38 modes! Less background due to additional kinematic constraints (m ES,  E). Better E  resolution. More model dependence due to finite set of explicitly reconstructed B  X s  decays.

Fully inclusive B  X s  CLEO, PRL 87, (2001), 9.1 fb-1 Measure for E  >2.0; extrap. to E  >0.25 GeV Belle, PRL 93, (2004), 140 fb -1 Belle, hep-ex/ (moments) Measure for E  >1.8 GeV; extrap. to full background subtracted efficiency corrected background subtracted not efficiency corrected

Fully inclusive, lepton-tagged B  X s  (B A B AR ) Suppress large continuum background using Event-shape cuts (continuum has jet topology) Lepton tag: high energy lepton from 2 nd B in event (B  X c l ) qq + ττ BB XSγXSγ continuum dominated BB dominated (blinded) lepton tag hep-ex/ (preliminary, submitted to PRL)

B A B AR Fully Inclusive B  X s  w/lepton tag hep-ex/ (preliminary, sub. to PRL) Spectrum from best fit to kinetic scheme. Spectrum from best fit to shape function scheme. (extrapolated, kinetic scheme) (measured) spectrum not efficiency corrected stat sys model

B A B AR B  X s  with Sum of Exclusive Final States B A B AR, PRD 72, (2005) Energy RangeBranching Fraction (10 -4 ) E  >1.9 GeV E  >1.6 GeV (extrapolated) averages over two shape-function schemes errors: stat, sys, variation of shape fcn params E  MomentsValue (GeV or GeV 2 ) E  (min) = GeV K*(890) for BF, sum over all m(X s ): continuum signal comb. BB peaking bknd for spectrum, fit m ES in bins of m(X s ) BF/10 -3

Summary: B  X s  Branching Fraction & Moments Buchmüller and Flächer, PRD 73, (2006) HFAG 2006: common corrections to for BFs for extrapolations to E    GeV. Gambino and Uraltsev, Eur. Phys. J C34, 181 (2004) green band expt uncert. average stat+sys b  d  frac shape fcn

Fits to moments of inclusive B  X c l and B  X s  distributions all moments kinetic mass scheme Buchmüller and Flächer, PRD 73, (2006) Data from BaBar, Belle, CDF, CLEO, & DELPHI m b used for |V ub | (7.5% error!)

Studies of radiative/electroweak penguins have moved far beyond B  K* . Observation of exclusive b  d  decays: B  (  0,  +,  )  Use to extract |V td /V ts |; consistent with value from B s mixing. Precision soon to be limited by theoretical uncertainties. Electroweak penguins decays B  K l + l -, B  K* l + l -, and B  X s l + l - have been measured. First studies of decay distributions have been performed and exclude some non-SM scenarios. More data needed to exploit full potential. Inclusive B  X s  measurements provide information on m b and non-pert. QCD parameters and help improve precision on |V cb | and |V ub |. Difficult issues with systematic errors, but goal is to achieve 5% uncertainty on branching fraction. We will study radiative/EW penguins for many years to come at BaBar, Belle, and LHC-b! Conclusions

B A B AR

Backup slides

Extracting |V td /V ts | from b  d  Decays Belle, PRL 96, (2006). BABAR, hep-ex/ (preliminary) CDF, hep-ex/ (preliminary) Consistent within errors. Theoretical uncertainties limiting both approaches. BR(B→(ρ/ω)γ)/BR(B→K*γ) Belle 2005 CDF measurement (  m S ) B-Factories average BaBar ICHEP 2006 CKM fitter code w/o Δm s

B 0   BABAR, hep-ex/ , 347 M BB

B  Kl + l - and B  K*l + l - : q 2 distributions J/   (2S)K q2q2 q2q2 SM nonres SUSY models Pole from K*  even in  +  - constructive interf. destructive

B  Kl + l - and B  K*l + l - : the J/  veto The decays B  J/  K and B  J/  K* are huge backgrounds and must be carefully removed (also B   (2S)K,  (2S)K*). These backgrounds are restricted in q 2, but there is a tail due to bremsstrahlung in the electron modes. But B  J/  K and B  J/  K* are valuable control samples; use them to study efficiency of almost any analysis cut. Ali, Kramer, Zhu: B  Ke + e - J/  and  (2S) veto: MC B  Ke + e - e + e - )B  Ke + e - m(e + e - ) projection: MC B  Ke + e -

M(l + l - ) distributions from B  J/  K + control samples: data vs. Monte Carlo absolute normalization points: data histogram: MC Bremsstrahlung tails well described by MC. B A B AR

B  Kl + l - Signal from B A B AR summed over all K l + l - modes (K + e + e -, K +  +  -, K S e + e -, K S  +  - ) significance=6.6  rarest observed B decay (averaged) B A B AR, PRD 73, (2006) 229 M BB

B  K*l + l - Signal from BAB AR B A B AR, PRD 73, (2006) 229 M BB

B  K*l + l - Dalitz plot Can see A FB behavior and q 2 dependence from the Dalitz plot Note: B  Kl+l- is expected to have very small A FB, even in presence of new physics; effectively provides a crosscheck. effect of  pole Standard Model Prediction

B  K*l + l - Dalitz plot Can see A FB behavior and q 2 dependence from the Dalitz plot effect of  pole Maximal new physics effect:

B  K*l + l - : B A B AR results on q 2 distribution BABAR, PRD 73, (2006)

Lepton angular distribution in l  l  rest frame use l - if B use l + if B Ali, Kramer, Zhu, hep-ph/

Extracting A FB and F L in bins of q 2 B A B AR, PRD 73, (2006)

Belle, hep-ex/041006

Inclusive B  X s  some history CLEO, PRL 74, 2885 (1995); 2.01 fb -1 on Y(4S), 0.96 fb -1 below Y(4S) Backgrounds: B decays, continuum, e + e -  qq  (ISR), e + e -  qq   0 X “Event-shape analysis”“B-reconstruction analysis” scaled off resonance total background (points w/error bars)

B A B AR B  X s  with Sum of Exclusive Final States Reconstruct 38 exclusive modes |  E|<40 MeV For E  spectrum, fit m ES distrib. in bins of m(X s ) Correct for efficiency of each mode and missing modes fraction (  model dependence) for BF, sum over all m(X s ): continuum signal comb. BB peaking bknd

Systematic Errors on B  X s  Belle, PRL 93, (2004)

Belle: B  X s l + l - Belle, PRL 72, (2006) 5.4 

Extraction of heavy-quark expansion parameters from B  X s  B  X s  inclusive E  spectrum B  X c l inclusive E l spectrum and M(X c ) hadron mass distrib. m b now determined to about 1% and |V cb | is determined to <2%. (measures kinetic-energy-squared of b-quark) Using heavy-quark expansion (HQE), moments of inclusive B decay distributions can be expressed in terms of non-perturbative QCD parameters and quark masses.

Predictions for A FB in B  K*l + l - : SM and beyond Standard Model s 0 : Ali, Kramer, Zhu, hep-ph/

B  K*l + l - : B A B AR results on A FB and  L SM q 2 range (GeV 2 ) A FB FLFL Data excluded at 3.6  ! Any A FB 2.7  use in 2 bins of q 2 (A FB =0 in SM and many BSM)