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Jan 28th, 2009Colin Jessop at Notre Dame An experiment to measure CP violation in B mesons Colin Jessop University of Notre Dame
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Measuring a CP phase by Interference Measuring a CP phase by Interference Interference of two amplitudes is required initial final The two amplitudes must have a relative CP even phase and relative CP odd phase CP even phase: CP odd phase: (the CP violating phase)
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame initial final For the (antiparticle) process Define an Asymmetry: A cp =0 if =0 or =0 Measuring a CP violating Phase
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Real Amplitude + Complex: CP odd phase from Vub CP even phase from gluon Strong Phase from non-perturbative QCD is not reliably predicted Direct CP Violation Direct CP Violation CP even phase from strong interaction.
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Use Mixing to Provide CP even Phase Mixing parameters discovered to be favourable to such a measurement in 1980’s and these parameters are precisely measurable
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame f cp (e.g K 0 s) CP eigenstates f cp accessible to B 0 and B 0 are rare ( < 1 in 3000 B decays) Measuring CP odd phase in B Mixing Need to produce millions of B meson decays Need a way to identify if you started with B 0 or B 0 Need to measure time dependence of process
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame A Confluence of Nature and Technology In the 1980’s we found that the parameters of B decays made this measurement possible but not at existing facilities ChallengeSolution Millions of B mesons High Luminosity e+e- storage rings Identifying B or BProduce BB pairs Measuring time dependence Development of silicon track detectors
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame An Asymmetric B meson “Factory” An Asymmetric B meson “Factory”
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Two B-Factories: USA and Japan Two B-Factories: USA and Japan BELLE at KEKB nr Tokyo, Japan Both US and Japanese experiments Parralleled each other 1993-2004 After 2004 funding issues in US slowed BaBar down and lead to eventual termination of experiment in 2007 (486 fb-1) BELLE in Japan is still going strong (895 fb-1 so far) At termination BaBar was running at seven times design luminosity.and had published over 300 papers
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame B-Flavor Tagging Exclusive B Meson Reconstruction (flavor eigenstates) lifetime, mixing analyses (CP eigenstates) CP analysis Experimental Technique for B Factories (4S) produces coherent B pair: t t Time-integrated asymmetries are zero
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame BABAR Collaboration Gathering at SLAC, July 2002 9 Countries 76 Institutions 550 Physicists July 2002
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Cerenkov Detector (DIRC) 1.5 T solenoid Electromagnetic Calorimeter Drift Chamber Instrumented Flux Return Silicon Vertex Tracker e + (3.1 GeV) e - (9 GeV) BABAR Detector
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Silicon Vertex Detector at BABAR 5 Layer AC-coupled double-sided silicon detector Located in high radiation area –Radiation hard readout electronics (4- 5Mrad) 97% hit reconstruction efficiency Hit resolution ~15 μm at 90 o e - beame + beam
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Completed SVT Detector Beam pipe Layer 1,2 Layer 3 Layer 4 Layer 5 B1 bending magnet Readout chips r BP,IR = 25 mm 2 x Be walls = 0.83+0.53 mm T 1.5 mm H 2 O cooling gap
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame BABAR Drift Chamber BABAR Drift Chamber 40 layers of wires (7104 cells) in 1.5 Tesla magnetic field Helium:Isobutane 80:20 gas, Al field wires, Beryllium inner wall, and all readout electronics mounted on rear endplate Particle identification from ionization loss (7% resolution) 16 axial, 24 stereo layers
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame An Innovative Detector for Seperating K + / +
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Projection Screen Quartz bars Cerenkov Detector Construction
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame K + / + Separation K + / + Separation K + / + for tagging and CP eigenstate identifiction
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame High Resolution Electromagnetic Calorimeter 6580 CsI(Tl) crystals with photodiode readout 0 reconstruction for rare CP eigenstates = 5.0% 00
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July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Completed Detectors Completed Feb 1999 First collisions May, 1999
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