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Summary of Recent Results on Rare Decays of B Mesons from BaBar

Lake Louise Winter Institute Chateau Lake Louise 20-26 February 2011. Summary of Recent Results on Rare Decays of B Mesons from BaBar. Searching for New Physics via Effective Flavor-Changing Neutral Currents. for the BaBar Collaboration. Bruce A. Schumm

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Summary of Recent Results on Rare Decays of B Mesons from BaBar

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  1. Lake Louise Winter Institute Chateau Lake Louise 20-26 February 2011 Summary of Recent Results on Rare Decays of B Mesons from BaBar Searching for New Physics via Effective Flavor-Changing Neutral Currents for the BaBar Collaboration Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz

  2. Outline Recent (past year) results are in three areas: • B  K l+ l- with Missing Energy • B  K (limit) • B  K + -(limit) • B   (limit) • b  (s,d)  Penguins • CP Violation in Penguin Decays (measurement) • B→Xd and the Status of |Vtd/Vts| (measurement) LLWI 2011: Rare Decays at BaBar

  3. The BaBar Dataset 426 fb-1 54 fb-1 BaBar collected 468 M BB pairs between 2000-2007 and 54 fb-1 off-resonance data LLWI 2011: Rare Decays at BaBar

  4. B+ K+ Flavor-Changing Neutral Currents and New Physics For example: • The Basic Story: • FCNC process in SM require loops  suppressed rates • New physics can enter at same order • Modification of BF (x10 or greater!) • Large CP-violating effects • But always a battle against backgrounds… Standard Model Contribution from Extended Higgs Sector LLWI 2011: Rare Decays at BaBar

  5. K Boosted Decision Tree • Missing energy • Whole-event properties • Signal kinematics • Reconstruction quality B  K,K Approach Mitigate backgrounds by tagging recoil B meson Signal B Meson Tagging B Meson K Selection: Multivariate Algorithm (Boosted Decision Tree) B  K Tag with reconstructed exclusive SL decay;   1% B  K Tag with fully reconstructed Hadronic decay;   0.2% K Selection: Cut-Based LLWI 2011: Rare Decays at BaBar

  6. B  K,K Results K Result: Phys. Rev D82, 112002 (2010) SM Expectation  4x10-6 W. Altmannshofer et al., JHEP 04, 022 (2009) G. Buchalla et al., PRD63, 014015 (2000) Comparison of results, B+ K+ SM Expectation K Result (Preliminary): SM Expectation  2x10-7 J.L. Hewett, Phys. Rev. D53, 4964 (1996) (But New Physics effects coupling to m2f could approach measured limit) PRELIMINARY Momentum Transfer to +- System LLWI 2011: Rare Decays at BaBar

  7. B   arXiv:1010.2229; to appear in Phys. Rev. D Form B candidates from photon pairs after likelihood-based 0 rejection B(B) = (1.7  1.1(stat.)  0.2(syst.)) x 10-7 (1.9 significance) B(B) < 3.2 x 10-7 (90% CL) SM Expectation (Bosch & Buchalla, JHEP 0208:054, 2002) LLWI 2011: Rare Decays at BaBar

  8. Radiative Penguins I: ACP in b  (s,d)  • Reconstruct single high-energy photon 2.1 < E* < 2.8 GeV • Reduce backgrounds by requiring lepton on tagging side • Charge of lepton tags flavor on signal side • Standard model expectation: • Any signal would be an unambiguous signature of new physics. Inclusive Radiative Penguin Reconstruction High Energy Photon PRELIMINARY Tagging B Meson (Lepton from SL decay) X LLWI 2011: Rare Decays at BaBar

  9. Vts(d) (d) Vt(s,d) (d) (d) (d) Vts(d) b  d (“Xd”) and Vtd/Vts • Motivation and Interpretation • (bs) leading indirect constraint on new physics (SUSY, extended Higgs, extra dimension…) • (bd)/(bs)  0.03  Precise measurements of (bd) even more constraining? • Practicalities: • Rate depends on hadronic effects  Normalize to Vts by measuring corresponding s-quark process • Rate depends on poorly constrained CKM parameter Vtd Play off against B mixing, which also measures Vtd sensitively •  Compare effective values of |Vtd/Vts| from B mixing and radiative penguins decays (different diagrams!); discrepancy implies new physics LLWI 2011: Rare Decays at BaBar

  10. b  d (“Xd”) and Vtd/Vts • Initial approach: • Reconstruct B  (,)  and B  K* ; • |Vtd/Vts| from [B(,)]/[BK*] • More current (“Xd” Analysis) : • Reconstruct “semi-inclusively” via • sum of seven exclusive decay modes; • |Vtd/Vts| directly from [bs]/[bd] • Use two independent hadronic system mass ranges • 0.6 < MX < 1.0 (, “resonant” region) • 1.0 < MX < 2.0 • Together, comprise ~2/3 of total width LLWI 2011: Rare Decays at BaBar

  11. B  Xd  Results Result of fit to seven B Xd modes in high mass region 1.0 < MX < 2.0 GeV/c2 First observation of b  d transition above resonance (,) region Phys. Rev. D 82, 051101(R) (2010) Theory Error No evidence for new physics in bd transition Relative accuracy of bd constraint approaching that for bs transition Has impact of this constraint been fully examined? LLWI 2011: Rare Decays at BaBar

  12. Summary • New limits on B  K and B  K • B(B  K+) < 1.3 x 10-5 approaching SM expectation of B(B  K+)  4 x 10-6 • B(B  ) < 3.2 x 10-7; consistent with expected B(B) = • b  (s,d)  Penguins • No observed CP violation in b (s,d); -0.05 < ACP < 0.16 at 90% CL • First observations of bd in non-resonant region; |Vtd/Vts| from b→ d consistent with that from B mixing; relative accuracy of constraint approaching that of bs. LLWI 2011: Rare Decays at BaBar

  13. Backup LLWI 2011: Rare Decays at BaBar

  14. # bodies # bodies # 0 # 0 Measured Regions for B  Xd(s)  UNMEASURED XS MEASURED K* Region 1.0 < Mhad < 2.0 2.0 < Mhad 0.6 < Mhad < 1.0 UNMEASURED Xd MEASURED Xd analysis only  and Xd analyses Mhad (MXd) LLWI 2011: Rare Decays at BaBar

  15. B  s and SUSY Parameter Space (cont’d) … on some of our favorite scenarios … Fate of “Snowmass” MSSM study points LLWI 2011: Rare Decays at BaBar

  16. B  s and SUSY Parameter Space (cont’d) … and just in general. C.F. Berger, J.S. Gainer, J.L. Hewett, T.G. Rizzo, “Supersymmetry Without Prejudice”, arXiv:0812.0980v1 [hep-ph] Explore 107 points over 19-dimensional parameter space of CP-conserving MSSM b  s most effective constraint (72% of models surviving prior constraints are eliminated; better than direct searches for SUSY partners) LLWI 2011: Rare Decays at BaBar

  17. The BaBar Detector LLWI 2011: Rare Decays at BaBar

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