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Status of the KEK E391a Experiment. G. Y. Lim IPNS, KEK. 質量起源と超対称性物理の研究 2005 年 3 月 7 日. E391a searching for K L p o nn decay Very clean FCNC process Golden mode for a test of the SM and search for a new physics The first dedicated experiment to the K L p o nn decay. - PowerPoint PPT Presentation
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Status of the KEK E391a Status of the KEK E391a ExperimentExperiment Status of the KEK E391a Status of the KEK E391a ExperimentExperiment
G. Y. LimIPNS, KEK
質量起源と超対称性物理の研究
2005年 3月 7日
IntroductionIntroductionIntroductionIntroduction E391a searching for KL decay
Very clean FCNC process Golden mode for a test of the SM and sear
ch for a new physics The first dedicated experiment to the KL decay
Contents Detection principle Data taking The 1st version of analysis
(M. Doroshenko – Ph.D. theses) Run-II Summary
JPARC, KOPIO
A dream of theorist and a nightmare of experimentalist
Detection PrincipleDetection PrincipleDetection PrincipleDetection Principle
KL
Nothing
pure CsI calorimeter 4 veto system
Clear single 0 with high PT
High High -detection efficiency-detection efficiencyHigh High -detection efficiency-detection efficiency
Expected main background is KL
4veto system without any dead space
Low energy threshold for -detection Noise reduction Accidental hits
Making a correct inefficiency table for -detection
Pencil beam and vacuum systemPencil beam and vacuum system Pencil beam and vacuum systemPencil beam and vacuum system
E391a detector setupE391a detector setupE391a detector setupE391a detector setup
KL beam
E391a detector setupE391a detector setupE391a detector setupE391a detector setup
Data TakingData TakingData TakingData Taking Data taking during 18, Feb ~ 1, July 2004
Detector/ DAQ tuning (44 shifts ) - with low intensity (30 shifts) Beam break due to water leakage of beam line magnets (21 shifts) Additional fine tuning of DAQ, beam line (8 shifts) Start stable data taking from 15th, March
~ 28, April (116 shifts) 19th, May ~ 21th June (71 shifts)
Calibration Run Data with air / production (24 shifts)
6 TB of data Tape library on KEK computer center
Data analysis 1 Day 1 Week (1/10 of the full data) We are trying to understand characteristics of the backgrounds correctly estimate the sensitivity
Fine monitoring channelsFine monitoring channelsFine monitoring channelsFine monitoring channels
MC
data
03K
02K
MC
data
MC
data
MC
data
03K
02KK
Invariant Mass of 6(GeV/c2)
Invariant Mass of 4(GeV/c2)
Reconstructed decay vertex of KL (cm)
6- event sample 4- event sample 2- event sample
Pure data sample for Photo Veto counters
M.C. reproduce data reasonably
KL KL KL
Normalization for the number of KL
Pure signal and background sample for veto counter study
Study of photon veto counters (example)Study of photon veto counters (example)Study of photon veto counters (example)Study of photon veto counters (example)
Two gamma eventsTwo gamma eventsTwo gamma eventsTwo gamma events
Data without tight veto
Reconstructed vertex (cm)
CsI S
urfa
ce
PT(G
eV/c
)
KL KL
KL KL
KL e KL
Hard to explain using KL decay only
M.C. for KL decays ( Without Normalization)
KL Decay
Unexpected Unexpected oo production by Neutrons production by NeutronsUnexpected Unexpected oo production by Neutrons production by Neutrons
Various contributions to the 2-gamma sampleVarious contributions to the 2-gamma sampleVarious contributions to the 2-gamma sampleVarious contributions to the 2-gamma sample
Reconstructed vertex (cm)
Cou
nts
K2
K
Halo n
Core n
Neutron related events are dominant
n/separation
Halo neutron generate 2- in the CsI calorimeter (M.C.)
Example of n/Example of n/separationseparationExample of n/Example of n/separationseparation Shower shape at the calorimeter Distance between gammas
There are varieties in real application in detail.
Current acceptance reduce to 0.14~0.5 due to these additional cuts.
After finishing Photon Veto / Kinematical cutsAfter finishing Photon Veto / Kinematical cutsAfter finishing Photon Veto / Kinematical cutsAfter finishing Photon Veto / Kinematical cuts
B.G. events can be controlled
Acceptance loss
- Shower leakage
- Neutron related events
o production at the detector
To study fiducial region events
More statistics (in progress)
Clearer beam condition(Run-II)
BR(K) < )%90(1091.1 6 CL
@ 1-day statistics
Run-IIRun-IIRun-IIRun-II
Improve sensitivity Increasing statistics by removing the membrane by installation of CC00
Understand B.G. Characterize neutron B.G. by
comparing Run-I and Run-II Clearer condition to understand
backgrounds related to the KL decays
Data taking for 100 shifts from 2nd, Feb. 2005
Run-III in this autumn
Semi-online plots for 2-cluster events
PT (GeV/c) Decay Vertex (cm)
RUN-I RUN-II
RUN-I
RUN-II
SummarySummarySummarySummary The data taking has taken successfully
300 shifts in Run-I (187 shifts for physics data) The first version of analysis (1-day)
Good indication for data quality Identify the nature of background Make a direction for further study (expecting improvements)
Run-II After fixing a hardware trouble Clearer condition to study about the background
Diligent progress in step-by-step to the JPARC New physics search across the Grossman-Nir limit
BR(K) < )%90(1091.1 6 CL