1. J. Whitmore BEACH 2004 June 30, 2004 KTeV Results: K L    ( =e, , ) BEACH 2004 June 30, 2004 Julie Whitmore, Fermilab l Physics Motivation - Direct CP Violation l KTeV Detector l Results l Summary The KTeV Collaboration: Arizona, Campinas, Chicago, Colorado, Elmhurst, Fermilab, Osaka, Rice, Rutgers, Sao Paulo, UCLA, UCSD, Virginia, Wisconsin

2. J. Whitmore BEACH 2004 June 30, 2004 Direct CP Violation in K L   0 Direct CP Violation in K L   0 Direct (K L  K 2 +  K 1 ; K 2   0  *,  0 Z*) DIR The Golden Mode

3. J. Whitmore BEACH 2004 June 30, 2004 CPV = Indirect (K L  K 2 +  K 1 ; K 1   0        + Interference + Direct (K L  K 2 +  K 1 ; K 2   0  *,  0 Z * ) Conserving(K L  K 2 +  K 1 ; K 2   0      CP Violation in K L   0 CP Violation in K L   0 Theoretical Predictions (from theory + BR(K L  0  )) Theoretical Predictions (from theory + BR(K s  0 ) (NA48))

4. J. Whitmore BEACH 2004 June 30, 2004 KTeV Fixed Target Run KTeV(E832) 96-97 Data Set: 3.3E6 K L  0  0 l KTeV (E799-II) 97 Data Set: 2.7E11 K L Decays KTeV(E832) 99 Data Set: 3.7E6 K L  0  0 l KTeV (E799-II) 99 Data Set: 3.6E11 K L Decays

5. J. Whitmore BEACH 2004 June 30, 2004 The KTeV Detector l Pure CsI Calorimeter: (Energy resolution  1% at  E   = 10GeV,  /e rejection of  700) l Transition radiation detectors (p/e rejection of  200) l Drift chambers with resolutions (~100  m) l Clean intense beams: (5-8)E12 protons on target per spill 5-8 x 10 9 kaons per spill l KTeV (E799-II) Data Set: 6.3E11 Kaon Decays (97 + 99)

6. J. Whitmore BEACH 2004 June 30, 2004 l Advantage - Dominated by direct CP violation Disadvantage -  0   difficult; Dalitz decay BR(  0  ee  ); significant backgrounds l 1997 Analyses 1. Dalitz Analysis (  0  ee  ) Event Selection: 1 , 2 electron-like showers matched to tracks, unbalanced P t Backgrounds: K L  2  0, K L  3  0,   n  0,    0 Normalize to K L  ee  2. Neutral Analysis (  0   ) Special Run - 1 Day of data taking, Single smaller beam Normalize to (K L   0  0 ) l 1999 Data – Dalitz Trigger Prescaled K L    K L    Z vertex Muon Steel Muon Counters KLKL e+e+ e-e-  CsI from e + e -

7. J. Whitmore BEACH 2004 June 30, 2004 BR(K L    )  5.9 x 10 -7 (  0  ee , 1997 Data) [PRD 61,072006 (2000)] BR (K L    )  1.6 x 10 -6 (  0  , 1997 1 Day) [PLB 447, 240 (1999)] K L    K L    Data MC BG Sum   n   MC     MC Signal MC 1997 Data Dalitz Analysis

8. J. Whitmore BEACH 2004 June 30, 2004 K L    e + e - Advantage: fully reconstruct the final state. l Disadvantages: not pure direct CP violation Serious background (K L  ee  ) Contributions to BR(K L    e + e - ) CP Violating: BR ~ (17 ± 9 + 5 ) x 10 -12 (est. from theory+K S   0 e + e - ) CP Conserving: BR ~ 0.5 x 10 -12 (est. from theory+ K L     ) Total:BR  K L   0 e + e -  )= (1-3) x 10 -11 New Physics  Enhancements in BR Previous Result: BR (K L   0 e + e - )< 5.1 x 10 -10 (KTeV1997) [PRL 86, 397 (2001)]

9. J. Whitmore BEACH 2004 June 30, 2004 1988 Events 76.6  3.3 Est. Background K L  e + e -  BR(K L  e + e - , E  * >5MeV) = (6.31  0.14(stat)±0.42(sys))x10 -7 [PRD 64, 012003 (2001)]  L  0  0,  0  ee   L  ee   ACC

10. J. Whitmore BEACH 2004 June 30, 2004 K L    e + e - l Analysis – 1999 Data Event selection: 2  forming  0 ; 2 electron-like showers matched to tracks, CsI+TRD(  /e) Backgrounds: K L     +  -, K L   e +  acc +  rad, and K L  ee  Suppress with kinematic Cuts: |COS(   )| and  min Total contribution in the blind analysis box: 3.9 ± 1.4 events (2.9 ± 0.47 events come from K L  ee  Normalize to K L     ,    ee  Muon Steel Muon Counters CsI Z vertex KLKL e+e+ e-e-   from e + e -

11. J. Whitmore BEACH 2004 June 30, 2004 K L    e + e - Signal Ellipse ± 2  K L  ee  ; M   M   M  M   K L   e +   ACC K L   e +  rad +  ACC XX eX K L       eXeX K L       eX  Blind Analysis Box Region

12. J. Whitmore BEACH 2004 June 30, 2004 Kinematic Variables for K L    e + e - and K L  e + e -  Cos(   ) K L  0 ee  min K L  ee  K L  0 ee K L  ee  K L  e+e-  K L   0 e+e-

13. J. Whitmore BEACH 2004 June 30, 2004 Kinematic Cuts for K L    e + e - and K L  e + e -  l Phase space cuts optimized Cuts varied and expected background and signal acceptance calculated 90% CL BR limit determined for each set via Feldman-Cousins technique Assume any events are background Cuts optimized to yield lowest expected branching ratio limit Signal Acceptance: (2.749 ± 0.013)% 30% less than 1997 due to accidentals (tighter TRD, phase space, and mass cuts) SES: 1.04 x 10 -10 Cos     MIN Cos(  <0.745  MIN >0.362

14. J. Whitmore BEACH 2004 June 30, 2004 K L    e + e - BR(K L    e + e - )  3.50 x 10 -10 (90% C.L.) (1999) [Accepted by PRL] BR(K L    e + e - )  2.8 x 10 -10 (90% C.L.) (1997+1999) 1999 Data Box Region: 130<m  <140 MeV/c 2 485<meegg<510 MeV/c2 Signal Region: ± 2  in K L    e + e - Background in ellipse: 0.99 ± 0.35

15. J. Whitmore BEACH 2004 June 30, 2004 K L     +  - l Advantage: Probes direct CP violation Like K L    e + e - - fully reconstruct the final state l Disadvantages: phase space suppression Small relative to the CPC and Indirect CPV Potential background (K L   ) Contributions to BR(K L     +  - ) CP Violating: BR ~ (9 ± 6 + 1) x 10 -12 (est. from theory + K S   0     ) CP Conserving: BR ~ 5 x 10 -12 (est. from theory+ K L     ) Total:BR  K L         )= (1 – 2) x 10 -11 New Physics  Enhancements in BR Previous limit: BR (K L   0     )< 5.1 x 10 -9 (E799-I)

16. J. Whitmore BEACH 2004 June 30, 2004 K L     +  - l 1997 Analysis Event Selection: 2  reconstructing as a  0 ; 2 tracks which MIP in the calorimeter, 2 ID muons Backgrounds from  punch- through and  decay-in-flight from  +  -  0 and K L  (+ 2  ACC ); K L   (0.373  0.032 evts) Suppress with kinematic cuts on M(  ) and M(  ) Angular cuts on |COS(   )| and  min less effective than with ee  Total contribution: 0.87 ± 0.15 events Normalize to  +  -  0 decays Muon Steel Muon Counters CsI  Z vertex from     KLKL   

17. J. Whitmore BEACH 2004 June 30, 2004 K L       Dangerous background for K L   0     l Never been observed l Analysis Event Selection: 2  which do not reconstruct as a  0 ; 2 tracks which MIP in the calorimeter, 2 ID muons Backgrounds from K L   (+2  ACC ),  +  ACC Kinematic Cuts: E  Total Contribution: 0.155 ± 0.081 Normalize to K L   +  -  0 QED Pred:BR(K L       9.1  0.78) x 10 -9

18. J. Whitmore BEACH 2004 June 30, 2004 K L   First observation 4 events seen BR(K L       M  >1MeV/c 2 )  BR(K L       E  * >10MeV)  [PRD 62, 112001 (2000)]

19. J. Whitmore BEACH 2004 June 30, 2004 Kinematic Distributions for K L     +  - and K L   +  -  K L  K L  0  K L   min Cos(   ) K L  0  K L     K L  

20. J. Whitmore BEACH 2004 June 30, 2004 K L     BR(K L     )  3.8 x 10 -10 (90% C.L.) [PRL 86, 5425 (2001)] 2 events in signal region Background MC Data

21. J. Whitmore BEACH 2004 June 30, 2004 Current Status

22. J. Whitmore BEACH 2004 June 30, 2004Summary Analyzed 1997 data - BR(K L    )  5.9 x 10 -7 (  0  ee  ) B(K L  e + e -  (6.31  0.14(stat)  0.42(sys))x10 -7 No Dalitz trigger in1999 data Look forward to future experiments – KOPIO and E391a Analyzed full KTeV data set (1997 + 1999) - BR(K L    e + e - )  2.8 x 10 -10 (90% C.L.) Analyzed 1997 data - BR(K L     3.8 x 10 -10 (90% C.L.) B(K L       x 10 -9 Currently analyzing 1999 data Combined 1997+1999 data set ~ 2 x 1997 More accidentals – tighter cuts (lose acceptance) Normalize to K L       – reduce uncertainties from muon system Expected SES (1997+1999) ~ 1 x 10 -10