Measurements of Measurements of Radiative Penguin B Decays Radiative Penguin B Decays at BaBar at BaBar Jeffrey Berryhill University of California, Santa Barbara For the BaBar Collaboration 32 nd International Conference on High Energy Physics August 17, 2004 TM All results preliminary unless explicitly indicated
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Measurements of Radiative Penguin B Decays at BaBar
TM. Measurements of Radiative Penguin B Decays at BaBar. All results preliminary unless explicitly indicated. Jeffrey Berryhill University of California, Santa Barbara For the BaBar Collaboration. 32 nd International Conference on High Energy Physics August 17, 2004. - PowerPoint PPT Presentation
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Measurements of Measurements of Radiative Penguin B Decays at Radiative Penguin B Decays at
BaBarBaBar
Jeffrey BerryhillUniversity of California, Santa Barbara
For the BaBar Collaboration
32nd International Conference on High Energy Physics
August 17, 2004
TM
All results preliminary unless explicitly indicated
ICHEP 17 Aug 04 Jeffrey Berryhill (UCSB) 2
Radiative Penguin Decays and New Radiative Penguin Decays and New PhysicsPhysics
Radiative penguin decays: b → s and b → d FCNC transitions
SM leading order = one EW loopVts, Vtd dependent
FCNCs probe a high virtual energy scale comparable to high-energy collidersRadiative FCNCs have precise SM predictions:
BF(b→s)TH = 3.57 ± 0.30 x 10-4 (SM NLO)BF(b→s)EXP = 3.54 ± 0.30 x 10-4 (HFAG)
Decay rate agreement highly constrains new physics at the electroweak scale!
Further tests presented here:•Exclusive b→s decay rates
•b→s CP asymmetries•b→d penguins
Multiple new BF(b→s)measurements coming soon from BaBar
For signal, mES ≈ mB, mES) ≈ 3 MeV E* ≈ 0, (E*) ≈ 50 MeV
Small rates (BF < 10-4) on top of large backgrounds
Common strategy : select photon + hadrons with strict particle ID cut when possible on meson masses reduce continuum background with multivariate methods extract signal with multi-dimensional maximum likelihood fit
583±30 events
Ex: signal fit for B → K*0, K*0 → K+-Best kinematic constraintsfrom B candidate momentum and energy, compared with Ebeam:
Combine properties discriminatingB → + X from continuuminto a single-output neural net:
•Event shape variables: spherical B vs. jet-like continuum•B flavor tagging variables: kaons and leptons in the rest of the event•B candidate vertex separation fromrest of the event
Neural net trained on simulated signal and continuum samples
•Decay rate measurements of b→ s penguins are well into the precision era.
•CP asymmetries of b→ s penguins are statistics limited and will continue to test the SM
ACP in B → Xs PRL 93 (2004) 021804, hep-ex/0403035 BF, ACP, and Isospin asymmetry in B→ K*submitted to PRL, hep-ex/0407003time-dependent CPV in B0 → K*0 submitted to PRL, hep-ex/0405082
b→ d penguins are only now beginning to reveal themselves in B-factory data.They could also uncover new physics, or measure the poorly known |Vtd|.
BaBar finds no evidence for B → in 211 million BB events submitted to PRL, hep-ex/0408034
BF(B → ) < 1.2 X 10-6 |Vtd/Vts| < 0.19 (90% CL)
First measurement!
Backup SlidesBackup Slides
TM
ICHEP 17 Aug 04 Jeffrey Berryhill (UCSB) 22
B B → K*→ K*(82 fb(82 fb-1-1): Signal fits): Signal fits
ICHEP 17 Aug 04 Jeffrey Berryhill (UCSB) 23
B B → K*→ K*(82 fb(82 fb-1-1): K*): K* lineshape lineshape
K* lineshape forevents with:mES > 5.27 GeV/c2
-0.2 GeV <E < 0.1 GeV
Background subtractedwith shape from mES
sideband
Fit to relativistic Breit-Wigner withPDG K*), mK*
ICHEP 17 Aug 04 Jeffrey Berryhill (UCSB) 24
Time-Dependent CP Asymmetry inTime-Dependent CP Asymmetry in B B →→K*K*
Projection of fit with likelihood cut
Z resolution vs. KS decay radius
ICHEP 17 Aug 04 Jeffrey Berryhill (UCSB) 25
B B → → Neural net performanceNeural net performance