1 / 37

370 likes | 447 Views

A New Measurement of from KTeV. E. Blucher, Chicago. Introduction The KTeV Detector Analysis of 1997 Data Update of Previous Result Conclusions. The KTeV Collaboration: Arizona, Chicago, Colorado, Elmhurst, Fermilab, Osaka, Rice, Rutgers, UCLA,

Download Presentation
## A New Measurement of from KTeV

**An Image/Link below is provided (as is) to download presentation**
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.
Content is provided to you AS IS for your information and personal use only.
Download presentation by click this link.
While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

**A New Measurement of from KTeV**E. Blucher, Chicago • Introduction • The KTeV Detector • Analysis of 1997 Data • Update of Previous Result • Conclusions The KTeV Collaboration: Arizona, Chicago, Colorado, Elmhurst, Fermilab, Osaka, Rice, Rutgers, UCLA, UCSD, Virginia, Wisconsin Snowmass**Indirect vs. Direct CP Violation**KL~ Kodd + Keven “Indirect” from asymmetric mixing “Direct” in decay process / 0 direct CP violation Standard Model Prediction: Re() ~ (0-30)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 Datataking**• First result (PRL 83, 22 (99)) 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**KL**a rab b zab**(before background subtraction)**1997 Reconstructed Mass Distributions ~ 1.6 MeV ~ 1.5 MeV**Backgrounds**Main classes of background: • Misidentified kaon decays • For K+-: KLe, KL • For K00: KL000 • Scattered K events • From regenerator and final collimator Background levels (in %)**Center-of-energy for K Events**• KS+ distribution used to model scattering • background in K . • Improvements in procedurerevealed a mistake • in the background estimation for the • published result: Re() = 1.7.**Yield after Background Subtraction**KL “KS” Vacuum Beam Reg. Beam K 8,593,988 14,903,532 K00 2,489,537 4,130,392 Raw double ratio: (no acceptance correction)**0.1% shift in E scale:**~3 cm shift in vertex; ~1 shift in **Acceptance**• Detailed Monte Carlo simulation based on • measured detector geometry and response. • Includes: • Accidental overlays • Full trigger simulation (L1,L2,L3) • For K00: • Geant-based shower library for CsI • (showers cover 0.6750.675 m2) • Detail photon veto simulation • For K+-: • Detailed drift chamber simulation • Magnetic field map • CsI pion shower library • High statistics decay modes (e.g., K e, • K 30) are used to check MC simulation.**KTeV 1997* Data / Monte Carlo Comparison**KL KLe * excludes 1997a data used in publication.**KTeV 1997 Data / Monte Carlo Comparison**KL KL**Calorimeter Energy Scale**Final energy scale adjustment based on regenerator edge. Energy scale depends on PK. Applying an energy-independent scale shifts Re() by -0.5 compared to nominal method.**Cross Checks of Energy Scale**Check E scale with different modes: K, K*KS, hadronic 2 production, K20 Dalitz, 30**Calculating **Naively, but regenerator beam is not purely KS.**KL - KS Interference Downstream of Regenerator**KTeV Preliminary Results:**Re() Result from 1997 Data Set**Re() = (19.8 1.7 (stat) 2.3 (syst) 0.6 (MC stat)) 10-4**Geometry-only Monte Carlo**KL+ KL • Using acceptance correction from MC with • perfect detector resolution (only geometry) • shifts Re( by 12 compared to full MC. • Correcting for observed data/MC z slope • reduces shift to ~2 .**Cross-check using reweighting method**Reweight KL decays to reg. beam distribution. • Provides check of Monte Carlo method • Statistically less significant than Monte Carlo • method ().**KTeV and NA48 Beams**KTeV NA48**Reweighting Method Result**Based on preliminary study of correlation of systematic errors, difference between standard method and reweighting method is: Re() = (1.5 2.1 (stat) 3 (syst)) **Improvements in Analysis**• CsI Calibration • Drift Chamber calibration and alignment • Neutral backgrounds • Apertures • Attenuation • m, S**Update of Published Result(96-97a dataset)**Re() = (23.2 3.0 (stat) 3.2 (syst) 0.7 (MC stat)) 10-4**KTeV Results**• 1997 (independent from published result) Re() = (19.8 1.7 (stat) 2.3 (syst) 0.6 (MC stat)) 10-4 • Updated 1996/1997a Re() = (23.2 3.0 (stat) 3.2 (syst) 0.7 (MC stat)) 10-4 • Combined 1996+1997 Result Re() = (20.7 1.5 (stat) 2.4 (syst) 0.5 (MC stat)) 10-4 = (20.7 2.8) 10-4**Measurements of Re()**World ave. Re()= (17.2 ) (confidence level = 13%)**Re() and Im() from Fermilab**Experiments**Conclusions**• KTeV results from 1996+1997 data: Re() = (20.7 1.5 (stat) 2.4 (syst) 0.5 (MC stat)) 10-4 = (20.7 2.8) 10-4 New measurements of m, S, +, and • New world average: Re() = (17.2 ) • Full KTeV data sample (96+97+99) will reduce the statistical error on to ~ 1 10-4 significant work will be required to reduce systematic error to similar level • Theory improvement needed to take full advantage of this precision.

More Related