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Searches for New Physics at BaBar

Searches for New Physics at BaBar. Haleh Hadavand UC San Diego July 18, 2005 SUSY 2005 Conference. This Talk will Cover. CP violation The BaBar experiment Gluonic Penguins Radiative Penguins Leptonic decays Lepton Flavor Violation in t decays. B 0 → π + π − B 0 → ρ + ρ −.

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Searches for New Physics at BaBar

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  1. Searches for New Physics at BaBar Haleh Hadavand UC San Diego July 18, 2005 SUSY 2005 Conference

  2. This Talk will Cover • CP violation • The BaBar experiment • Gluonic Penguins • Radiative Penguins • Leptonic decays • Lepton Flavor Violation in t decays H. Hadavand SUSY 05

  3. B0 → π+π−B0→ ρ+ρ− b → ulν B0B0 mixing qi = u,c,t α VtdVtb* VudVub* W+ gVij qj'= d',s',b' γ VcdVcb* β B0→ D*πB+ →D0CP K+ B → ψKSB → φKS b → clν The Quark Mixing Matrix The only Standard-Model source of CP violation in the quark sector The Cabibbo-Kobayashi-Maskawa matrix relates the flavor (q′) and the mass (q) quark eigenstates: The “unitarity triangle” H. Hadavand SUSY 05

  4. If f is a CP eigenstate, fCP, we have CP violation if λf≠ ±1: • |q/p| ≠ 1 (CP violation in mixing, negligible in SM) • |Af /Af| ≠ 1 (direct CP violation, small in b→ccs) • Im(λf) ≠ 0 (interference between mixing and decay) Time evolution of the B0 meson The time-dependent rate for B0 (G+) or B0 (G−) decays to a final state f (neglecting the lifetime difference between the mass eigenstates BH and BL): where , , , H. Hadavand SUSY 05

  5. PEP-II accelerator schematic and tunnel view The PEP-II Asymmetric B-meson Factory Most results presented are from: Run 1-2 = 88 M BB events Run 1-4 = 227 M BB events bg=0.55 (4S) Run1-4 9 GeV Run1-2 3.1 Gev Peak luminosity: 9.21 x 1033 cm–1s–2 (design: 3 x 1033 cm–1s–2) Best 24 hours: 711 pb–1 (design: 135 pb-1/day) H. Hadavand SUSY 05

  6. The BaBar Detector • ElectromagneticCalorimeter • Lepton, photon ,and p0 id 1.5 T solenoid • Cerenkov Detector (DIRC) • kaon/pion id e+ (3.1 GeV) e-(9 GeV) • Drift Chamber • 40 layers (24 stereo) z axis • Silicon Vertex Tracker • Find B vertex • 5 layer double sided strip detectors (z-f) • Instrumented Flux Return • Muon id • KL id 9 meters H. Hadavand SUSY 05

  7. Time-dependent CP analysis at a B-meson factory Exclusive B-meson reconstruction ~260 μm Δz (BaBar) Y (4S) produces a coherent pair of neutral B mesons B-flavor tagging H. Hadavand SUSY 05

  8. Kinematic Variables In CM of Y(4s) Energy Difference DE resolution depends on detector energy resolution and final particles in decay Energy substituted mass mES resolution dominated by beam energy spread 2.5 MeV/c2 H. Hadavand SUSY 05

  9. Results for BJ/yK0 (cc) KSmodes (CP = -1) background “Golden Mode” Phys. Rev. Lett. 94, 161803 (2005) • 4370 CP = −1 tagged events, signal purity ≈ 90% • 7730 total tagged events, signal purity ≈ 76% sin(2β)ccs= 0.722±0.040±0.023 H. Hadavand SUSY 05

  10. Gluonic Penguins

  11. Gluonic Penguin Decays B0η′K0,K +K−K0,π0 π0Ks,KsKsKs , ωKS, f0Ks , Ksπ0,φK0 • Gluonic penguins good way to probe new physics • New particles in the loop can cause deviations from SM diagrams • Dominated by top quark in loop • Expect same time-dependent CP violation as in bccs decays • Small direct CP asymmetry • Some modes more theoretically clean than others as we will see • Estimates from QCDF and SU(3) Standard Model SUSY H. Hadavand SUSY 05

  12. BABAR KKK0 QCDF SU(3) bound 227 M BB B0K+K−K0 KKKL: Nsig=777  80 CP contentin KKKL sample: f(P-wave) = 0.92  0.07  0.06 Cheng,Chua,Soni, hep-ph/0506268 Grossman,Ligeti,Nir,Quinn, PRD68 Combined KKKL and KKKS NSig=1229 events Phys. Rev. D 71, 091102(R) (2005) hep-ex 0507016 H. Hadavand SUSY 05

  13. BABARh’K0 QCDF SU(3) bound 232 M BB B0η′K0 h’KL: Nsig=440 Combined h’KLand h’Ks: Nsig=1245  67 Beneke, hep-ph/0505075 Grossman,Ligeti,Nir,Quinn, PRD68 2.8 s away from BaBar value of sin 2b =0.722 0.04 Phys. Rev. Lett. 94, 191802 (2005) H. Hadavand SUSY 05

  14. y Ks0 p+ p- p+ z p- p+ K0s e+ e- K0s p- Btag sz ~ 180 mm Btag- Standard Method B0KSKSKS The BCPproduction point is constrained to the beamspot in (x, y) • Beam size 4 mm in y and and 200 mm in x • Error on Dt still dominated by tag side B • About ~ 100% of events vertexed in 3Ks(p+p-) • About ~97% of events vertexed in 2Ks(p+p-)Ks(p0p0) • 3Ks(p+p-) • 2Ks(p+p-)Ks(p0p0) sPlot * sPlot [Pivk, Diberder, physics/0402083] all events H. Hadavand SUSY 05

  15. B0 KSKSKS QCDF SU(3) bound 227 M BB Combined result Preliminary Englehard, Nir, Raz hep-ph/0505194 Cheng,Chua,Soni, hep-ph/0506268 Nsig = 88 ± 10 PRL 95 011801 (2005). Main Systematic uncertainty PDF parametrization Nsig = 41± 9 Preliminary H. Hadavand SUSY 05

  16. Bp0p0KS 227 M BB • 70% of events with good Vertex • Use NN to reduce continumm background Nsig=11727 Preliminary • Dominant syst. errors: • pdf shapes • Bkg composition and CP • Dt resolution • fit bias H. Hadavand SUSY 05

  17. Summary of BABAR Results • No evidence for direct CP in these samples • Intriguing difference from sin2b[cc] remains: naïve average 0.440.09 (~2.7s) (BABAR Only) H. Hadavand SUSY 05

  18. New Combined sin2b Values Errors from QCD factorization [Beneke, hep-ph/0505075] [Cheng,Chua,Soni, hep-ph/0506268] • Most theoretical calculations have positive deviations • Avoid averaging all modes since effected by different errors • h’Ks and fKs modes with smallest uncertainty H. Hadavand SUSY 05

  19. (*) Radiative Penguins

  20. Radiative Penguins • New particle in loop can change both the rate and phase • SM: Photon approx left handed • Other: Theories more L-R symmetric Good agreement for inclusive modes Nucl. Phys B 631, 219 (2002)) BaBar Preliminary Exclusive decays have more theoretical uncertainties, form factors needed B → K*, , , Kll B0→0, , D*0, … B+→+, … H. Hadavand SUSY 05

  21. BK*g • Direct CP asymm: ACP = -0.013 0.036 0.010 • No isospin breaking from the dominant penguin diagram • In the K*g mode: D0  ~ 5 – 10 % (*): Errors stat.+syst.+uncertainty on B+/B0 production ratio B(B0→K*0) = (38.7  2.8  2.6) x 10-6 B(B+→K*+) = (39.2  2.0  2.4) x 10-6 Ali and Parkhomenko, Eur.Phys.JC 23,89 (2002) Ali et al, PLB 595,323 (2004) Can bound |Vtd/Vts| from ratio below: DR is different in dynamics such as W annihilation V =0.85 0.1form factor ratio * PRD 70, 112006 (2004) H. Hadavand SUSY 05

  22. Search for B →r/wg Simplest and most “common” b  dexclusive decays B0→0 B+→+ B0→ =42% =46% =50% A total of 211M BB 22 Simultaneous fit to all three samples with the constraint: Simultaneous fit to all 3 modes H. Hadavand SUSY 05 PRL 92, 11801 (2004)

  23. B →r/wg :CKM Constraints Theoretical limits : Must be close to discovery of decays Ratio of exclusive bsg and bdg modes provides useful CKM limits With theory error Without theory error H. Hadavand SUSY 05

  24. Measurement of BK(*)l+l- SUSY diagram SM diagrams W+ W– box EW penguin RK BF(B Km+m-) / BF(B Ke+e-)  1 RK* BF(B K*m+m-) / BF(B K*e+e-)  0.75 New Physics can change enhance RK/K* value direct CP violation forward-backward di-lepton asymmetry • SM predictions Suppressed decays (BF10-6), negligible direct CP asymmetry Ratio of branching fractions predictions Contribution from a pole in EM penguin for the e+e- final state at q2 0 See for instance Ali et al, Phys. Rev. D 66, 034002 (2002) H. Hadavand SUSY 05

  25. B K(*)l+l- Preliminary Results + 0.19 - 0.17 hep-ex/0507005 Preliminary BF( B Kl+l-) = ( 0.34 0.07 0.03)  10-6 BF( B K*l+l-) = ( 0.78 0.12)  10-6 B Kl+l- Crossfeed from B Kl+l- events Tested that no bias is induced 229M BB Preliminary RK= 1.06 0.48 0.05 RK* = 0.93 0.46 0.06 Consistent with SM Preliminary ACP( B+ K+l+l- ) = -0.08 0.22 0.11 (*) ACP( B K*l+l- ) = 0.03 0.23 0.12 (*) B K*l+l- (*): Main systematics due to a conservative estimate of the peaking background asymmetry H. Hadavand SUSY 05

  26. BKppg • Up to ms/mb corrections, we expect in the SM: • A different polarization is a marker of new physics • It can be probed in • Need 2 interfering amplitudes related by isospin: (Kp+)p0g (Kp0)p+g MES Gronau et al Phys. Rev. D66 (2002) 054008. hep-ex/0507031, preliminary H. Hadavand SUSY 05

  27. Time Dep-CP B0K*(K0sp0)g K*gR B0 B0 K*gL Same vertexing technique as B0K0sK0sK0s Standard Model Expectations: 156 +/- 16 events 59 +/- 13events In the SM, mixed decay to K*g requires wrong photon helicity Helicity Flip suppressed by ~ms/mb Mixing hep-ex/0507038, submitted to PRD-RC H. Hadavand SUSY 05

  28. Leptonic Decays

  29. Btn • New physics in Btn • Charged Higgs boson as propagator: SUSY, two-Higgs doublet models • Enhancement of the B up to 5 times • Measurement of fB • Assuming |Vub| known from semileptonic decays • Measurement of |Vub|2 / |Vtd|2 • From B (Btn)/Dm • Constraints CKM matrix • Experimentally challenging • n in final state H. Hadavand SUSY 05

  30. Btn ++ + e+ ++ + + misiden. lepton • Exclusive reconstruction with a semileptonic B “tag” • Search for a Btn signal in the rest of the event • t e+nn, m+nn, p+n, p+p0n, p+p-p+ • Eextra: Residual energy in Calorimeter • Peaks at 0 for signal events • Signal MC • on-res Data • Background MC H. Hadavand SUSY 05

  31. Btn B(B)  2.6  104 @ 90% C.L. fB0.41 GeV@ 90% C.L. Preliminary constraint on new physics tanb /mH < 0.34 (GeV/c2)-1 tanb  ratio of the vacuum expectation values for two-Higgs doublets Preliminary, combined with hadronic tags Preliminary, semileptonic tag B(B+ t+n) <2.8 10-4 @ 90% C.L. Total of 232 M BB events used H. Hadavand SUSY 05

  32. Lepton Flavor Violation in t decays

  33. tm/eg t- 9.0 GeV e- 3.1 GeV e+ t+ • BaBar is also a t factory • In SM B(te/mg) ~ O(10-40) from n mixing and mass inclusion • However LFV is present in other theories at the order of 10-10-10-7 E. Ma, Nucl. Phys. Proc. Suppl. 123, 125 (2003). J.R Ellis et al Phys. Rev. D 66, 115013 (2002). • Current most stringent experimental limits of that order 10-7-10-8 H. Hadavand SUSY 05

  34. tm/eg • Tag side t reconstructed in 6 modes-1-1 or 1-3 prong topology • Use Neural Network to reduce background in each mode after some initial cuts • m/e constrained to e+e- collision • axis m/e g trec 9.0 GeV e- 3.1 GeV e+ ttag Preliminary hep-ex/0502032 accepted by PRL Beam Energy constrained mass: H. Hadavand SUSY 05

  35. Summary (*) Gluonic Penguins: sin 2b measured is less than charmonium; new theoretical bounds to interpret deviations; h’Ks and fKs modes to follow Radiative Penguins: CP asymmetries still statistics limited; b sg, sl+l- becoming precision measurements; Br/wg close to discovery limit Leptonic Decay: Btn consistent with SM; limit on fB < 0.41 GeV and tan b/MH<0.34 GeV LFV in t decays: New upper limit on teg <1.1 x 10-7 sensitivity at reach of New Physics H. Hadavand SUSY 05

  36. Backup Slides H. Hadavand SUSY 05

  37. Vertexing Constraints p+ p- Brec sz ~ 50mm For short lived particles p+ Ks0 Constrain in x-y to beam-spot p- K0s p+ e+ e- K0s p- Beam-Spot Constrained Vertexing (BSCV) Btag sz ~ 180 mm y y Btag- Standard Method x z p+ p- p- p+ K0s p+ K0s K0s ~30 mm Beam ~4 mm ~200 mm Inflated Beam Beam • K0s have a long lifetime • Can decay outside SVT or have few hits • Need SVT hits to find Vertex • Solution:Constrain in x-y plane to the beam • Inflate error to error on beam size • Comparable to sz from tag side H. Hadavand SUSY 05

  38. Bsg  B+ B- Xs e or  Xc  B+ B- K, Ks,etc X • New particle in loop can change both the rate and phase • SM: Photon approx left handed • Other: Theories more L-R symmetric Two Experimental Techniques Sum of Exclusive modes Inclusive, tagged recoil B 38 modes Kinematic constraints reduces background Lepton tag reduces bkg Reconstruct photon (1.8-2.8 GeV) H. Hadavand SUSY 05

  39. bsg Preliminary Results Semi-exclusive Peak corresponding to K* resonance ( M(Xs) < 1.1 GeV/c2 ) +0.64 +0.07 -0.41 -0.08 B(E1.6 GeV) = ( 3.38 ± 0.19 )·10-4 SM expectation (Nucl. Phys B 631, 219 (2002)): B(bsE1.6 GeV) = ( 3.57 ±0.30 )·10-4 ACP(bs)= ( 0.025 ± 0.050 ± 0.015 ) “simpler” version of the analysis Inclusive tag SM expectation: ACP(bs) < 1% ACP(bs+b d) = (-0.010 ± 0.115 ± 0.017 ) SM expectation ACP(bs+bd)~0 A total of 89M BB events are used 39 PRL 93 021804 (2004) B rest frame Y(4s) rest frame H. Hadavand SUSY 05

  40. B0ωKS : dominated by b → sdd B0f0KS : yes, dominated by b → sss Another two penguin-dominated modes: B0ωKS,f0KS The possible tree contamination is relatively large. Nsig = 92 ± 13 hep-ex/0503018 (conf. paper) Nsig = 153 ± 19 hep-ex/0408095 (conf. paper) H. Hadavand SUSY 05

  41. B0KSKSKS,KSπ0 B0KSKSKS : theoretically clean, ηCP=+1 B0KSπ0: tree pollution up to 20% Nsig = 88 ± 10 PRL 95 011801 (2005). Nsig = 300 ± 23 hep-ex/0503011 (submitted to PRD-RC) The BCPproduction point is constrained to the beamspot in (x, y) H. Hadavand SUSY 05

  42. CP Violation in the B System • CPV through interference of decay amplitudes • CPV through interference between mixing and decay amplitudes H. Hadavand SUSY 05

  43. B0D*0g Weak annihilation important for bdg understanding: annihilation diagram in addition to rad penguin SM expectation 10-6 88 M BB events hep-ex/0506070, submitted to PRL H. Hadavand SUSY 05

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