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
-
Upload
ila-barrett -
Category
Documents
-
view
41 -
download
3
description
Transcript of 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
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
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
Overview
3
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 veto)• Aerogel Photon Counter (-tagger)
– Data Taking• (almost) stable DAQ condition
Introduction
4
Detector Upgrade in Run3
• aaa
Introduction
Aerogel Photon Counter(APC)
Upgraded
Added
Back Anti
5
Back Anti UpgradeIntroduction
PWO crystalconstruction
• In-beam veto counter
Back AntiUpgraded
6
Aerogel Photon CounterIntroduction
• Prototype of E14 BA
Aerogel Photon Counter(APC)
Added
γ
e+
e-
Cerenkov light
7
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
Introduction
KEK 12GeV PS East Counter Hall
E391aC-line
A-line
Be absorber to reduce neutron (betteer n/K ratio) # of KL ~60% / # of n ~ 40%
※
※
※
8
Strategy for Run3 AnalysisCalibration
kdecay,halo-n, eta
Strategy for Run3 Analysis
Results
Step1Confirmation
Step2 Optimization
Step0Preparation
Step3Physics Output
[MC] Develop Run3 MC
[Data] Data quality check
[Data] Cut optimization
[MC] MC mass production
9
Step0 : PreparationCalibration
kdecay,halo-n, eta
Step0 : Preparation
Results
Step1Confirmation
Step2 Optimization
Step0Preparation
Step3Physics Output
[MC] Develop Run3 MC
[Data] Data quality check
[Data] Cut optimization
[MC] MC mass production
10
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
Step0 : Preparation
11
Back Anti Upgrade• Upgrade Back Anti
– lead plate + plastic scinti. + quartz
PWO crystal + quartz– segmentation :
longitudinal
transverse
• Benefits– better n/ separation
(shower shape analysis)– lower rate
(typ. 1/2 @ center crystal)
Run2 BA
beam
Run3 BA
Step0 : Preparation
12
Calibration of Back Anti
• Calibration– Calibration has been done
with Muon Run
ADC count
MIP peak with Muon Run
Muon Run : use from upstream (with beam shutter closed)
MIP peak
Step0 : Preparation
13
Step1 : ConfirmationCalibration
kdecay,halo-n, eta
Step1 : Confirmation
Results
Step1Confirmation
Step2 Optimization
Step0Preparation
Step3Physics Output
[MC] Develop Run3 MC
[Data] Data quality check
[Data] Cut optimization
[MC] MC mass production
14
Step1 : Confirmation• Confirm Run3 data quality
– compare with Run3 MC : MC middle size production– compare with Run2 data
KL 30 6sample, 4(KL 20 4, 2
Step1 : Confirmation
Run2 Run3
Mass (GeV/c2) Mass (GeV/c2)
Invariant Mass of 6 sample
Matchs well CsI calibration is good in Run3
15
Step2 : OptimizationCalibration
kdecay,halo-n, eta
Step2 : Optimization
Results
Step1Confirmation
Step2 Optimization
Step0Preparation
Step3Physics Output
[MC] Develop Run3 MC
[Data] Data quality check
[Data] Cut optimization
[MC] MC mass production
16
Step2 : Optimization• Develop complete BA veto (algorithm, threshold, etc…)
• Study with Run2 opened box– to get more acceptance– optimize veto & event selections
Step2 : Optimization
Veto kinematic cut
Acceptance Loss / Rejection Power in Run2
17
PlanCalibration
kdecay,halo-n, eta
Plan
Results
Step1Confirmation
Step2 Optimization
Step0Preparation
Step3Physics Output
[MC] Develop Run3 MC
[Data] Data quality check
[Data] Cut optimization
[MC] MC mass production
Completed
Almost done
Ongoing (~1-2 month)
OK
~4-5 month
In parallel withMC mass prod.
18
Summary• E391a Run3
– Data : ~70% of Run2 (~80% with A&C mode)– Detector Upgrade
• Upgraded Back Anti (BA) : in-beam -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
Summary
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
Principle of the experiment
1. require 2 photons– Hermetic veto system
2. measure the photon energies and positions
3. reconstruct the decay vertex on the beamline assuming M2γ = Mπ0
halo/core ~10-5
5cm
4. require missing PT and the vertex in the fiducial region• “Pencil” beam line
to improve PT resolution- 8cm diameter @ 16m
from the target
22
Features of E391a apparatus
• 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
CsI calorimeterCsI calorimeter
Charged Veto (CV)Charged Veto (CV)Main Barrel (MB)Main Barrel (MB)
Front Barrel (FB)Front Barrel (FB)
23
Aerogel Photon Counter• Aerogel Photon Counter (APC)
– Aerogel Cherenkov counter : only sensitive to fast particle• insensitive to neutrons / sensitive to 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)
γ
e+
e-
Cerenkov light
Step0 : Preparation
24
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)
ADC count ADC count
MIP peak ~300count 2 MIPs peak
~ 600 count
Step0 : Preparation
25
Response to photons (3)
N-cluster trigger
Accidental trigger (TMON)
(Black) – (Red)
15 p.e.
• 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 sample.
26
Mechanism of CV Background
• even+extra odd
and 2 extra
fusion 1 from 0 + extra
27
Mechanism of CV background• removing Veto : odd & 01+extra• removing g-selection : even+extra• with bifurcation for each mechanism, even+extra is dominant
setup + box + selection + veto
-veto - selection all cuts
all 3277 44 6 0 (.081)
even+extra 306 4 2 0 (.026)
odd 210 26 0 0 (0.0?)
fusion 226 3 1 0 (.013)
1+ extra
2525 11 3 0 (.013)
extra 2clustr 10 0 0 0 (0.0?)
tighten
loosen
28
Electronics and DAQ• 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%
PMT
PMT
8ch
Analog each out
Analog sum out
Digital outfor
timing
Trigger logic
CsI
FASTBUS-VME
FASTBUS ADC
Veto
FASTBUS ADC
AmpDiscri
FASTBUS-VME
TKO TDC
TKO-VME
GbE
Event BuilderStorag
e
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
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
Strategy for Run3 Analysis