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Results from KTeV. E. Blucher, Chicago. Introduction The KTeV Detector Status of analysis Conclusions. The KTeV Collaboration: Arizona, Chicago, Colorado, Elmhurst, Fermilab, Osaka , Rice, Rutgers, UCLA, UCSD, Virginia, Wisconsin. Indirect vs. Direct CP Violation.
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Results from KTeV E. Blucher, Chicago • Introduction • The KTeV Detector • Status of analysis • Conclusions The KTeV Collaboration: Arizona, Chicago, Colorado, Elmhurst, Fermilab, Osaka, Rice, Rutgers, UCLA, UCSD, Virginia, Wisconsin ICHEP 2000, Osaka
Indirect vs. Direct CP Violation KL~ Kodd + Keven “Indirect” from asymmetric mixing “Direct” in decay process / 0 direct CP violation KTeV Goal: measure / to 10-4
KTeV Detector KL E832: E799: rare decays KL + KS KS: c ~ 3.5m KL: c ~ 2.2 km For EK ~ 70 GeV,
KTeV CsI Electromagnetic Calorimeter KL a rab b zab
KTeV Datataking K for first result K+- for first result ,+- for this analysis • First result used from 1996 and • from first 18 days of 1997 E832 run (1997a). • Current analysis is based on remaining 1997 • data -- ~3 larger sample than first result. • 1999 run 1996 + 1997 with better • systematics
1997 Reconstructed Mass Distributions (before background subtraction) ~ 1.6 MeV ~ 1.5 MeV ( distributions exclude 1997a data used in publication.)
Backgrounds Main classes of background: • Misidentified kaon decays • For K+-: KLe, KL • For K00: KL000 • Scattered K events • From regenerator and final collimator K00 events
Acceptance • Acceptance correction based on detailed Monte Carlo simulation. • High statistics decay modes (e.g., K e, K 30) are used to check MC simulation. • Largest systematic error in first result came from data/MC comparison of z distributions for K +: 1997a K + Data / MC Comparison from first result + Data/MC z slope: = 1.6 Total syst. error from K+: = 2.0 Total systematic error: = 2.8 (from first result)
KTeV 1997* Data / Monte Carlo Comparison (preliminary) KL KLe * excludes 1997a data used in publication.
KTeV 1997 Data / Monte Carlo Comparison (preliminary) KL KL
Status of Analysis of 1997 Data • K: ~ complete; all systematics have been evaluated (current sys. error ~ 2/3 sys. error in first result). Work to reduce systematic error is continuing. • K : completing systematic studies. The 1997 analysis has been done blind. Thevalue of is still hidden.
Stability of Vacuum Beam (KL) / Regenerator Beam (“KS”) Ratio for KTeV preliminary 1104 97a 97b Run periods in 1997b rest of 1997 data published data (statistical errors only) • 1997b K data are consistent with • 1997a K data used in published result. • K ratioand are still hidden.
Conclusions • Published KTeV result: Re() = (28.0 3.0 (stat) 2.8(syst)) 10-4 = (28.0 4.1) 10-4 • Analysis of remaining 1997 sample is almost complete. Statistical error on this independent data sample will be 1.7 10-4 • Full KTeV data sample (96+97+99) will reduce the statistical error on to ~ 1 10-4 may be measured to 5%! • KTeV data sample will also provide precise measurements of m, S, +, 00, , and