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K L →π 0 νν 探索実験 KEK-PS E391a における Run3 データ解析の現状

K L →π 0 νν 探索実験 KEK-PS E391a における Run3 データ解析の現状. JPS 2008 Spring Meeting Hideki MORII (Kyoto Univ.). Overview. Contents. Introduction E391a Run3 Detector Upgrades in Run3 BA (calibraion plot) APC (calibration / g-tagging) Current Status & Strategy for Run3 analysis

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K L →π 0 νν 探索実験 KEK-PS E391a における Run3 データ解析の現状

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  1. KL→π0νν探索実験 KEK-PS E391aにおけるRun3データ解析の現状 JPS 2008 Spring Meeting Hideki MORII (Kyoto Univ.)

  2. Overview Contents • Introduction • E391a Run3 • Detector Upgrades in Run3 • BA (calibraion plot) • APC (calibration / g-tagging) • Current Status & Strategy for Run3 analysis • calibration • MC development • Run3 data quality check • Optimize cuts • Plan • Summray

  3. Introduction E391a Run3 • E391a • KL→π0νν measurement @ KEK 12GeV PS • pilot experiment for J-PARC E14 • Three data taking • Run1 : Feb 2004 – Jul 2004 • Run2 : Feb 2005 – Apr 2005 • Run3 : Nov 2005 – Dec 2005 • Run3 • Detector Upgrade • new Back Anti (in-beam g veto) • Aerogel Photon Counter (g-tagger) • Data Taking • (almost) stable DAQ condition

  4. Introduction Detector Upgrade in Run3 • aaa Back Anti Upgraded Aerogel Photon Counter (APC) Added

  5. Introduction Back Anti Upgrade • In-beam g veto counter Back Anti construction PWO crystal Upgraded

  6. Introduction e+ γ e- Cerenkov light Aerogel Photon Counter • Prototype of E14 BA Aerogel Photon Counter (APC) Added

  7. Introduction KEK 12GeV PS East Counter Hall A-line C-line E391a Run3 Data • Full Intensity Run (C only mode) • with Be aborber • ~583000 spills • ~70% of Run2 data • Half Intensity Run (A&C mode) • w/o Be absorber • ~98000 spills • ~10% of Run2 data c.f. ) Run2 • with Be absorber • ~860000 spills ※ ※ Be absorber to reduce neutron (betteer n/K ratio) # of KL ~60% / # of n ~ 40% ※

  8. Strategy for Run3 Analysis Strategy for Run3 Analysis Step0 Preparation Calibration [MC] Develop Run3 MC Step1 Confirmation [Data] Data quality check [MC] MC mass production Step2 Optimization kdecay, halo-n, eta [Data] Cut optimization Step3 Physics Output Results

  9. Step0 : Preparation Step0 : Preparation Step0 Preparation Calibration [MC] Develop Run3 MC Step1 Confirmation [Data] Data quality check [MC] MC mass production Step2 Optimization kdecay, halo-n, eta [Data] Cut optimization Step3 Physics Output Results

  10. Step0 : Preparation Step0 : Preparation • Calibration • completed (including upgraded / new detectors) • MC development • detector upgrades are implemented • now under middle-size production : confirming results • preparing for mass-production

  11. Step0 : Preparation Back Anti Upgrade Run2 BA • Upgrade Back Anti • lead plate + plastic scinti. + quartz ->PWO crystal + quartz • segmentation : longitudinal -> transverse • Benefits • better n/g separation (shower shape analysis) • lower rate (typ. 1/2 @ center crystal) beam Run3 BA

  12. Step0 : Preparation MIP peak with Muon Run ADC count Calibration of Back Anti • Calibration • Calibration has been done with Muon Run Muon Run : use m from upstream (with beam shutter closed) MIP peak

  13. Step1 : Confirmation Step1 : Confirmation Step0 Preparation Calibration [MC] Develop Run3 MC Step1 Confirmation [Data] Data quality check [MC] MC mass production Step2 Optimization [Data] Cut optimization kdecay, halo-n, eta Step3 Physics Output Results

  14. Step1 : Confirmation Step1 : Confirmation • Confirm Run3 data quality • compare with Run3 MC : MC middle size production • compare with Run2 data KL-> 3p0-> 6g sample, 4g (KL-> 2p0-> 4g), 2g Invariant Mass of 6g sample Run2 Run3 Mass (GeV/c2) Mass (GeV/c2) Matchs well -> CsI calibration is good in Run3

  15. Step2 : Optimization Step2 : Optimization Step0 Preparation Calibration [MC] Develop Run3 MC Step1 Confirmation [Data] Data quality check [MC] MC mass production Step2 Optimization [Data] Cut optimization kdecay, halo-n, eta Step3 Physics Output Results

  16. Step2 : Optimization Step2 : Optimization • Develop complete BA veto (algorithm, threshold, etc…) • Study with Run2 opened box • to get more acceptance • optimize veto & event selections Acceptance Loss / Rejection Power in Run2 kinematic cut Veto

  17. Plan Plan Step0 Preparation Calibration Completed OK [MC] Develop Run3 MC Almost done Step1 Confirmation [Data] Data quality check Ongoing (~1-2 month) [MC] MC mass production Step2 Optimization ~4-5 month kdecay, halo-n, eta [Data] Cut optimization In parallel with MC mass prod. Step3 Physics Output Results

  18. Summary Summary • E391a Run3 • Data : ~70% of Run2 (~80% with A&C mode) • Detector Upgrade • Upgraded Back Anti (BA) : in-beam g-veto • New Aerogel Photon Counter : prototype of E14 BA • both worked well • Current Status • calibration is completed • finalizing MC development • Now checking data quality • Future Plan • Develop BA veto • Precise study with Run2 opened box for more acceptance

  19. backup

  20. The E391a experiment • KL production with KEK 12GeV PS • Slow extraction • K0 beamline in the East Counter Hall • Intensity • 2 x 1012 protons on target (POT) per 2sec spill, 4sec cycle • production angle: 4°, KL peak momentum 2GeV/c, n/KL ratio: ~40 • Physics runs • Run I: February to July of 2004 • “Express” analysis with 10% data published in PRD (2006) • Run II: February to April of 2005 • The main topic of this seminar • Full data analysis • Integrated protons: 1.4x1018 POT • ~ 32 days without break • Run III: October - December of 2005 • Calibration ready, MC development in progress

  21. halo/core ~10-5 5cm Principle of the experiment • require 2 photons • Hermetic veto system • measure the photon energies and positions • reconstruct the decay vertex on the beamline assuming M2γ = Mπ0 • require missing PT and the vertex in the fiducial region • “Pencil” beam lineto improve PT resolution • 8cm diameter @ 16m from the target

  22. Features of E391a apparatus CsI calorimeter Front Barrel (FB) • Decay region • High vacuum: 10-5 Pa • to suppress the backgroundfrom interactions w/ residual gas • Detector components • Set in the vacuum: 0.1 Pa • separating the decay regionfrom the detector regionwith “membrane”: 0.2mmt film Charged Veto (CV) Main Barrel (MB)

  23. Step0 : Preparation e+ γ e- Cerenkov light Aerogel Photon Counter • Aerogel Photon Counter (APC) • Aerogel Cherenkov counter : only sensitive to fast particle • insensitive to neutrons / sensitive to g shower • Can be used as photon tag counter (for BA study) • prototype of E14 BA Pb convertor : 2mm thick (~0.3 X0) Aerogel : 30cm(x) x 30cm(y) x 5cm(z)

  24. Step0 : Preparation Calibration of Aerogel Photon Counter • Light yield • calibrated with Muon Run • MIP peak appears clearly • Photon Tagging • checked with KL decay • 2 MIPs (= e+e-) peak seen Muon Run Physics Run (KL decay sample) MIP peak ~300count 2 MIPs peak ~ 600 count ADC count ADC count

  25. Response to photons (3) • Clear peak around 15 p.e. is observed. • Response to photon is well reproduced by MC. • Tagging quality is 94 % (#p.e. > 10).  will be improved by using (for example) 5 g sample. 15 p.e. N-cluster trigger Accidental trigger (TMON) (Black) – (Red)

  26. Mechanism of CV Background odd even+extra fusion 1g from p0 + extra and 2g extra

  27. Mechanism of CV background • removing Veto : odd & p01g+extra • removing g-selection : even+extra • with bifurcation for each mechanism, even+extra is dominant tighten loosen

  28. Analog each out Electronics and DAQ Digital out for timing PMT • Number of channels • CsI calorimeter: ~600ch • Veto counters: ~400ch • “AmpDiscri” Module • Discrimination for TDC • Set near the detector • low noise • min. threshold: ~0.5 mV (ex. ~0.7MeV for CsI) • 8ch sum for the trigger • Trigger • Logic • CsI hardware clustering (thres. 80MeV) + Veto (20-100MeV) • ~300 events / 2 sec spill = 150Hz • DAQ live time • ~90% 8ch PMT AmpDiscri Analog sum out CsI Veto Trigger logic FASTBUS ADC FASTBUS ADC TKO TDC FASTBUS-VME FASTBUS-VME TKO-VME GbE Event Builder Storage

  29. Problems in Run-I • core neutron background • hitting on the membranesagging into the beam-line

  30. Result from Run-I 1week • Using 10% of Run-I data • set new limit • Br < 2.1x10-7 (@90%C.L.)(PRD 74:051105, 2006)

  31. Strategy for Run3 Analysis Can we speed up MC mass production? • Halo-n needs large amount of MC • needed 3 months in Run2 halo-n MC • in Run2 analysis, we used bifurcation method for CV bg • Recycling Method • collect only BG-like events with strong online-veto (discard “safe” events in production stage) • then, full simulation for “dangerous” events

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