1. Jan 28th, 2009Colin Jessop at Notre Dame An experiment to measure CP violation in B mesons Colin Jessop University of Notre Dame

2. 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)

3. 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

4. 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.

5. 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

6. 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

7. 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

8. July30th, 2008Bigi,Jessop,LoSecco at Notre Dame An Asymmetric B meson “Factory” An Asymmetric B meson “Factory”

9. 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

10. 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

11. July30th, 2008Bigi,Jessop,LoSecco at Notre Dame BABAR Collaboration Gathering at SLAC, July 2002 9 Countries 76 Institutions 550 Physicists July 2002

12. 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

13. 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

14. 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

15. 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

16. July30th, 2008Bigi,Jessop,LoSecco at Notre Dame An Innovative Detector for Seperating K + /  +

17. July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Projection Screen Quartz bars Cerenkov Detector Construction

18. July30th, 2008Bigi,Jessop,LoSecco at Notre Dame K + /  + Separation K + /  + Separation K + /  + for tagging and CP eigenstate identifiction

19. 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% 00

20. July30th, 2008Bigi,Jessop,LoSecco at Notre Dame Completed Detectors Completed Feb 1999 First collisions May, 1999