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Summary of Recent Results on Rare Decays of B Mesons from BaBar for the BaBar Collaboration Lake Louise Winter Institute Chateau Lake Louise 20-26 February 2011 Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz Searching for New Physics via Effective Flavor-Changing Neutral Currents
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BaBar LLWI 2011: Rare Decays at BaBar2 Bruce Schumm 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 → X d and the Status of |V td /V ts | (measurement)
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BaBar LLWI 2011: Rare Decays at BaBar3 Bruce Schumm The BaBar Dataset 54 fb -1 426 fb -1 BaBar collected 468 M BB pairs between 2000-2007 and 54 fb -1 off-resonance data
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BaBar LLWI 2011: Rare Decays at BaBar4 Bruce Schumm Flavor-Changing Neutral Currents and New Physics B + K + 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… For example: Standard Model Contribution from Extended Higgs Sector
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BaBar LLWI 2011: Rare Decays at BaBar5 Bruce Schumm B K,K Approach Mitigate backgrounds by tagging recoil B meson Tagging B Meson B K Tag with reconstructed exclusive SL decay; 1% B K Tag with fully reconstructed Hadronic decay; 0.2% Signal B Meson K Selection: Cut-Based K Boosted Decision Tree Missing energy Whole-event properties Signal kinematics Reconstruction quality K Selection: Multivariate Algorithm (Boosted Decision Tree)
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BaBar LLWI 2011: Rare Decays at BaBar6 Bruce Schumm 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) K Result (Preliminary): SM Expectation 2x10 -7 J.L. Hewett, Phys. Rev. D53, 4964 (1996) (But New Physics effects coupling to m 2 f could approach measured limit) Momentum Transfer to + - System Comparison of results, B + K + PRELIMINARY SM Expectation
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BaBar LLWI 2011: Rare Decays at BaBar7 Bruce Schumm B SM Expectation ( Bosch & Buchalla, JHEP 0208:054, 2002 ) 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) arXiv:1010.2229; to appear in Phys. Rev. D
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BaBar LLWI 2011: Rare Decays at BaBar8 Bruce Schumm Radiative Penguins I: A CP in b (s,d) Tagging B Meson X High Energy Photon Inclusive Radiative Penguin Reconstruction 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. PRELIMINARY (Lepton from SL decay)
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BaBar LLWI 2011: Rare Decays at BaBar9 Bruce Schumm 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 V ts by measuring corresponding s-quark process Rate depends on poorly constrained CKM parameter V td Play off against B mixing, which also measures V td sensitively Compare effective values of |V td /V ts | from B mixing and radiative penguins decays (different diagrams!); discrepancy implies new physics V t(s,d) Radiative Penguins II: b d (“X d ”) and V td /V ts V ts(d ) (d)
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BaBar LLWI 2011: Rare Decays at BaBar10 Bruce Schumm Radiative Penguins II: b d (“X d ”) and V td /V ts Initial approach: Reconstruct B ( , ) and B K * ; |V td /V ts | from [B ( , ) ]/ [B K * ] More current (“X d ” Analysis) : Reconstruct “semi-inclusively” via sum of seven exclusive decay modes; |V td /V ts | directly from [b s ]/ [b d ] Use two independent hadronic system mass ranges 0.6 < M X < 1.0 ( , “resonant” region) 1.0 < M X < 2.0 Together, comprise ~2/3 of total width
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BaBar LLWI 2011: Rare Decays at BaBar11 Bruce Schumm B X d Results Result of fit to seven B X d modes in high mass region 1.0 < M X < 2.0 GeV/c 2 First observation of b d transition above resonance ( , ) region 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? Phys. Rev. D 82, 051101(R) (2010) Theory Error
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BaBar LLWI 2011: Rare Decays at BaBar12 Bruce Schumm 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 < A CP < 0.16 at 90% CL First observations of b d in non-resonant region; |V td /V ts | from b → d consistent with that from B mixing; relative accuracy of constraint approaching that of b s .
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BaBar LLWI 2011: Rare Decays at BaBar13 Bruce Schumm
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BaBar LLWI 2011: Rare Decays at BaBar14 Bruce Schumm K * Region 1.0 < M had < 2.02.0 < M had XSXS XdXd MEASURED UNMEASURED and X d analyses X d analysis only M had (M Xd ) # 0 # bodies # 0 # bodies MEASURED UNMEASURED 0.6 < M had < 1.0
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BaBar LLWI 2011: Rare Decays at BaBar15 Bruce Schumm Fate of “Snowmass” MSSM study points … on some of our favorite scenarios …
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BaBar LLWI 2011: Rare Decays at BaBar16 Bruce Schumm C.F. BergerC.F. Berger, J.S. Gainer, J.L. Hewett, T.G. Rizzo,J.S. GainerJ.L. HewettT.G. Rizzo “Supersymmetry Without Prejudice”, arXiv:0812.0980v1 [hep-ph]arXiv:0812.0980v1 Explore 10 7 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) … and just in general.
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BaBar LLWI 2011: Rare Decays at BaBar17 Bruce Schumm
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