CIPANP Richard Kass 1 Searches for new physics in B decays at BaBar Outline of Talk Searches for: B 0  invisible ( γ ) Charged Lepton Flavor Violation Measurement of B  D (*) τ ν Richard Kass for the BaBar Collaboration

CIPANP Richard Kass 2 Search for B  invisible (  ) A. Dedes, H. Dreiner, and P. Richardson, Phys. Rev.D65, (2001) Search for B decays with neutrinos or other non-interacting (e.g. SUSY) particles in the final state. In SM B  v v is highly suppressed by ~(m v /m b ) 2 In SM BF(B  v v γ ) is ~10 -9 In SUSY models BF(B  invisible) can be enhanced to ~(0.1-1)x10 -6 due to neutrino + neutralino production Previous Babar results with 88.5 fb -1 ( B. Aubert et al., Phys.Rev.Lett.93:091802,2004 ): BF(B  invisible)<22x10 -5, BF(B  v v γ ) <4.7x10 -5

CIPANP Richard Kass 3 B  invisible ( γ ) analysis details Use BaBar data sample: 471x10 6 B B pairs taken at  (4S) Divide the event into a signal B and a tag B Use B 0  D (*)- l + v as the tag B. l=electron/muon Semi-leptonic B tag has higher efficiency than fully reconstructed B tag B 0 → D - lν D - → K + π - π - /K S π - B 0 → D *- lν D *- → D 0 π - /D - π 0 D 0 → K - π + /K - π + π 0 /K - π + π + π - Use cosine between B & D(*)l assuming only 1 v is missing common vertex for D (*) l system Signal side of the event: no charged tracks, require photon with E CM >1.2 GeV for B  invisible γ Use Neural Net to discriminate signal from background (B’s, q q, etc) B → Invisible D tag : 9 variables D* tag : 6 variables B → Inv.+γ D tag : 6 variables D* tag : 4 variables BaBar Preliminary

CIPANP Richard Kass 4 B  invisible ( γ ) analysis details Extract event yields using unbinned Max. Likelihood fit Discriminating variable is the extra energy in the EM calorimeter, E extra For B → invisible+ γ the high energy γ is removed from E extra. Signal region has E extra <1.2 GeV Signal efficiencies: B 0  invisible =17.8x10 -4, B 0  invisible+ γ = 16.0x10 -4 Signal and background yields determined from ML fit Preliminary B 0  invisible B 0  invisible+ γ

CIPANP Richard Kass 5 B  inv (γ) systematic errors & results Bayesian approach used to calculate 90% CL upper limits Use “unphysical” B +  inv ( γ ) as a control sample to check the analysis P(B) assumes flat priors, systematics modeled as gaussians BR(B 0  invisible) <2.4x10 -5 BR(B 0  invisible + γ ) <1.7x10 -5

CIPANP Richard Kass 6 Search for Charged Lepton Flavor Violation in B decay Look for charged B decays B ±  h ± τl with h=π/K and l=e/μ LFV highly suppressed in SM ~ (m v /m W ) 2 Possible to greatly enhance the rate in extensions to SM 2 nd & 3 rd generations favored if coupling ~ mass φ s is a scalar Sher & Yuan, Phys.Rev.D44: ,1991 consider φ s and estimate: B ±  h ± τe < 3x10 -3 B ±  h ± τ μ < 3x10 -4 BaBar: B ±  K ± τ μ < 7.7x10 CL, PRL 99, (2007) NP SM+v mixing submitted to PRD arXiv: v1

CIPANP Richard Kass 7 B ±  h ± τ l Analysis Details Use BaBar data sample: 472x10 6 B B pairs taken at Y (4S) Divide the event into a signal B and a tag B Tag B reconstructed using hadronic decays B ±  D (*)0 X - X - =combination of  s & Ks Signal B reconstructed from B ±  h ±  l  charged tracks  h ± = π ± or K ±, l=e or  indirectly reconstruct the tau (use 1-prong taus:  e  n     ): p  =- p tag - p h - p l E  = E beam – E h - E l m 2  = E 2  - | p  | 2  |m  -m  PDG |<60 MeV/c 2 Use B  D (*)0 lv, D 0  Kπ as a control sample for BF normalization N Dlv /N D*lv /N D**lv determined from ML fit to data B  D (*)0 μv D0D0 D* 0 D** 0 BaBar Preliminary

CIPANP Richard Kass 8 B ±  h ± τ l Analysis Details Extract event yields using an unbinned Max. Likelihood fit Use poisson PDFs for the three tau channels (  e  n     ) Assume uniform 3-body phase space for the signal decays Set 90% UL CL using Feldman-Cousins procedure Reject continuum ( e + e -  q q ) background using a likelihood ratio Variables include: cos  thrust neutral energy in calorimeter muon quality (primary, tau daughter) BaBar Preliminary

CIPANP Richard Kass 9 B ±  h ± τ l Results Look at 8 channels, NO signals, Only ULs Combine modes assuming B(B +  h + τl )= B(B -  h - τl ) 5X better model independent bounds on NP scale in μτ flavor changing operators. Λ bd >11 TeV, Λ bs >15 TeV D. Black, et al, PRD 66, (2002) BaBar Preliminary more details in “extra slides”

CIPANP Richard Kass 10 B  D (*) τν Large mass of tau adds sensitivity to additional helicity amplitude. For B  D (*) τν we have: -- D (*)  H-,W-H-,W- We can compare our rate measurements with the SM predictions for: These ratios are sensitive to physics beyond the SM arXiv: submitted to PRL S. Fajfer, J. F. Kamenik, I. Nisandzic, arXiv: ,, J. F. Kamenik, F. Mescia, PRD (2008)

CIPANP Richard Kass 11 Analysis Details Use BaBar data sample: 471x10 6 B B pairs taken at Y (4S) Divide the event into a signal B and a tag B Fully reconstructed tag B using hadronic decays Signal B reconstructed from a lepton (  e  ) & D (*) No additional charged particles allowed in event Require q 2 =(p B -p D(*) ) 2 > 4 GeV 2 Backgrounds are suppressed using Boosted Decision Trees Extract event yields using an unbinned 2-D Max. Likelihood fit Perform fit using lepton momentum in B rest frame (p l * ) & (missing mass) 2 mm 2 =(p e+e- -p tag -p D(*) -p l ) 2 Signal Samples: D 0 l, D *0 l, D + l, D *+ l with l= e or  Fixed backgrounds: B 0 -B + cross feed, combinatorial, continuum Use data control samples for corrections & validation: B  D ** lν, D (*) lν control samples BaBar Preliminary

CIPANP Richard Kass 12 B  D * τ ν Yields D*0D*0 Events/25 MeV Events/100 MeV m 2 miss (GeV 2 ) p l * (GeV) D*+D*+ D*0D*0 D*+D*+ Events/100 MeV Free yields Fixed yield BaBar Preliminary D *0  D *+  D*D* N sig 693±62245±27888±63 Stat. sig. (  ) R(D * )0.322± ± ±0.024 B( B  D * τν ) % 1.71± ± ±0.13 statistical errors only fit assumes R(D *0 )=R(D *+ )

CIPANP Richard Kass 13 B  D τ ν Yields Free yields Fixed yield D0D0 Events/25 MeV Events/100 MeV M 2 miss (GeV 2 ) p l * (GeV) D+D+ D0D0 D+D+ BaBar Preliminary D0D0 D+D+ DD N sig 314±60177±31489±63 Stat. sig. (  ) R(D)0.429± ± ±0.058 B( B  Dτν ) % 0.99± ± ±0.13 statistical errors only fit assumes R(D 0 )=R(D + )

CIPANP Richard Kass 14 Systematic Errors & Results R(D)=0.440±0.058±0.042 R(D * )=0.332±0.024±0.018 SM Average does not include this measurement  =correlation coeff. SourceR(D) %R(D * ) %  D ** lv bkg MC statistics Cont. & B B bkg  sig /  norm System. Uncert Statist. Uncert Total Uncertainty

CIPANP Richard Kass 15 Comparison with SM R(D)R(D*) BABAR / / SM / /  2.0  2.7  The combination of the two measurements (-0.27 correlation) yields  2 =14.6 for 2 DOF and p-value = 6.9x10 -4 Data differ from SM rate by 3.4 

CIPANP Richard Kass 16 Charged Higgs? Compare our R(D) & R(D*) measurements with Type II 2HDM red=theory ±1  blue=exp ± 1  PDF shapes and efficiencies are recalculated vs tan  /m H Data match the 2HDM model for: R(D): tan  /m H =0.44 ±0.02 & R(D*): tan  /m H =0.75 ±0.04 Exclude Type II 2HDM at 99.8% CL SM:tan  /m H =0

CIPANP Richard Kass 17 Summary & Conclusions *Search for B 0  invisible ( γ ): improved upper limits: BR(B 0  invisible) <2.4x10 -5 BR(B 0  invisible + γ) <1.7x10 -5 *Search for Charged Lepton Flavor Violation in B decay *Measurement of B  D (*) τ ν: Larger than SM predictions BR(B +  K + τμ) <4.8x10 -5 BR(B +  K + τe) <3.0x10 -5 BR(B +  π + τμ) <7.2x10 -5 BR(B +  π + τe) <7.5x10 -5 new improved R(D)R(D*) BABAR / / SM / /  2.0  2.7  Exclude Type II 2HDM at 99.8% CL submitted to PRL arXiv: submitted to PRD arXiv: v1

CIPANP Richard Kass 18 Extra slides

CIPANP Richard Kass 19 B ±  h ± τl Analysis Details Use BaBar data sample: 472x10 6 B B pairs taken at Y(4S) Divide the event into a signal B and a tag B The tag B is fully reconstructed using hadronic decays B ±  D (*)0 X - with X - =n 1 π, n 2 K, n 3 Ks, n 4 π 0, n 1 +n 2 ≤ 5, n 3 ≤2, n 4 ≤2 The signal B is reconstructed from B ±  h ±  l  charged tracks h= π or K l=e or  indirectly reconstruct the tau (use 1-prong taus:  e  n     ): p  =- p tag - p h - p l E  = E beam – E h - E l m 2  = E 2  - | p  | 2  |m  -m  PDG |<60 MeV/c 2 Use B  D (*)0 lv, D 0  Kπ as a control sample for BF normalization N Dlv /N D*lv /N D**lv determined from ML fit to data B  D (*)0 μv D0D0 D* 0 D** 0 ≈1 BaBar Preliminary

CIPANP Richard Kass 20 B ±  h ± τl Results submitted to PRD arXiv: v1

CIPANP Richard Kass 21 B  D (*) τ ν Yields arXiv:

CIPANP Richard Kass 22 PEP-II at SLAC asymmetric e + e − collider: 9 GeV (e - )/3.1 GeV (e + ) PEP-II Peak Luminosity 1.2 x cm -2 s -1 BaBar recorded 429 fb -1 at Y (4S) asymmetric e + e − collider: 9 GeV (e - )/3.1 GeV (e + ) PEP-II Peak Luminosity 1.2 x cm -2 s -1 BaBar recorded 429 fb -1 at Y (4S) 4.7 x 10 8  (4S)→B B events

CIPANP Richard Kass T Solenoid Electromagnetic Calorimeter (EMC) Detector of Internally Recflected Cherenkov Light (DIRC) Instrumented Flux Return (IFR) Silicon Vertex Tracker (SVT) Drift Chamber (DCH) e - (9 GeV) e + (3.1 GeV) BaBar Detector SVT, DCH: charged particle tracking: vertex & mom. resolution, K 0 s /Λ EMC: electromagnetic calorimeter:  /e/π 0 /η DIRC, IFR, DCH: charged particle ID: π/μ/K/p Highly efficient trigger for B mesons

CIPANP Richard Kass 24 Threshold kinematics: we know the initial energy (E* beam ) of the Y(4S) system Therefore we know the energy & magnitude of momentum of each B meson Background (spherical) (jet-structure) Signal Analysis Technique Also, use neural networks + unbinned maximum likelihood fits Event topology

CIPANP Richard Kass 25 BaBar DIRC BaBar K/  ID D * + → D 0  + D 0 → K +  -