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Radiative and electroweak penguin processes in exclusive B decays
Dmytro Kovalskyi University of California, Santa Barbara BaBar Collaboration Dmytro Kovalskyi ICHEP 2006
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Topics covered in this talk
FCNC – a well known method to look for new physics bd and bd ll - new testing ground for Standard Model B B RUN1-5 – 316 fb-1 BK(*)l+l B l+l RUN1-4 – 209 fb-1 Dmytro Kovalskyi ICHEP 2006
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Extraction of |Vtd/Vts| with B() decays
Use SU(3) to relate B() to BK* Get |Vtd/Vts| with B() Form factor ratio 1/ = 1.17±0.09 hep-ph/ Annihilation amplitude corrections R = 0.1±0.1 SU(3) breaking corrections: A.Ali, A.Parhomenko hep-ph/ pre-ICHEP2006 results 2005 Belle observation of B() - first “direct” measurement of |Vtd/Vts| Dmytro Kovalskyi ICHEP 2006
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Extracting signal in B()
Reconstructed decays: B+, ++0 B0, 0 B, 0 Background Signal Major challenge – enormous background from Signal-background separation: 0 and photon veto and photon isolation particle identification event shape event content kinematical constraints Maximum likelihood fit (E, mES, Neural Net, helicity) BD used to validate signal NN PDF BK* control sample and background ee - photon systematics Dmytro Kovalskyi ICHEP 2006
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We do see B B++ B00 Dmytro Kovalskyi ICHEP 2006
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BaBar estimate of |Vtd/Vts|
Combined fit result: BR(B→(ρ/ω)γ)/BR(B→K*γ) Belle 2005 CDF measurement (mS) B-Factories average BaBar ICHEP 2006 CKM fitter code w/o Δms Global CKM fit excluding ms and B() Dmytro Kovalskyi ICHEP 2006
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B l+l - Terra Incognita
Standard Model prediction: Last measurement by Mark II (1990): Big Bang Expected improvement is ~ 104 – 105 |Vtd/Vts|2 suppressed with respect to BKll, which has been seen already Electroweak penguin and box amplitudes are not well constrained, so surprises are possible. Today Mark II Dmytro Kovalskyi ICHEP 2006
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B l+l - no signal found with Standard Model just around the corner
Dmytro Kovalskyi ICHEP 2006
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Different ways to probe new physics in BK(*)l+l
Electroweak penguins with substantial signal yield well established signal large number of observables to test SM branching fractions decay rate asymmetries angular distributions CP violation BK*ll (57 events) BKll (46 events) Dmytro Kovalskyi ICHEP 2006
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Forward-backward asymmetry and K* polarization
AFB – forward-backward asymmetry of the helicity angle of l+l- system FL – longitudinal component of polarization Theoretical curves Experimental results Dmytro Kovalskyi ICHEP 2006
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Branching ratios, CP asymmetries
Dmytro Kovalskyi ICHEP 2006
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Conclusion BaBar confirms Belle observation of B(), finds first evidence for B++ and provides the most precise measurement of the decay rate: Based on this information we estimate: New search for B l+l improves the previous upper limit measured by Mark II by about 4 orders of magnitude: Significant signal yield in BK(*)l+l decays allows to measure the forward-backward asymmetry of l+l- system, which provide a way to probe for new physics contribution in radiative and electroweak penguin decays Dmytro Kovalskyi ICHEP 2006
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BACK UP SLIDES Dmytro Kovalskyi ICHEP 2006
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The CKM matrix Dmytro Kovalskyi ICHEP 2006
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BaBar Detector e+ (3.1 GeV) e- (9 GeV) Electromagnetic Calorimeter
Cerenkov Detector (DIRC) 1.5 T solenoid Electromagnetic Calorimeter Drift Chamber Instrumented Flux Return Silicon Vertex Tracker e+ (3.1 GeV) e- (9 GeV) Dmytro Kovalskyi ICHEP 2006
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Improvements in background suppression
and veto: mass resolution vs energy dependence and photon conversion (~10% less background) New Neural Net: B flight significance, B flavor tagging, correlations etc (~30% less background) Dmytro Kovalskyi ICHEP 2006
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B/K l+l details Dmytro Kovalskyi ICHEP 2006
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