| 博士論文 |
| 2014 | 李 宗垣 | Lee, Jong-won |
| Energy Calibration Method for the KOTO CsI Calorimeter |
| Abstract:
The KOTO experiment aims to observe the rare decay of long lived neutral kaons,KL- > π 0ν ν, with the sensitivity of the Standard Model prediction.
The detectors of the KOTO experiment were constructed at J-PARC. The electromagnetic calorimeter is the only detectorto measure energies and hit positions of gamma which are used for the KL- > π 0ν ν reconstruction.
To guarantee the performance of the calorimeter, an accurate output monitoring method and a precise energy calibration method are required.
I built an output monitoring system using Laser light source, and determined its performance.
For the calibration of the calorimeter, thecalibration sources are limited to the cosmic ray events and KL decay events, because thereare no other detectors which can measure energy or momentum of particles independently.
In addition, the KOTO experiment will run for several years, and thus the calibration has to be done simultaneously with the data taking to secure the reliabilities of data.
Because of these restrictions, I developed and studied a new calibration method which uses KL- > 3π 0 decay events and occasional absolute energy calibration runs.
This method can calibrate the calorimeter with an accuracy less than 1%.
|
| 2012 | 岩井 瑛人 | IWAI, Eito |
| CsI calorimeter for the J-PARC KOTO experiment |
| Abstract:The KOTO experiment was designed and is being prepared at J-PARC (Japan Proton Accelerator Research Complex), to observe the rare decay of long lived neutral kaons, KL- > π 0ν ν
with the sensitivity of the Standard Model prediction. An electromagnetic calorimeter for the
KOTO experiment was upgraded to have a finer granularity and waveform readout capability.
We measured the performance of the calorimeter, and reproduced the obtained performance
based on the first principle. We also developed a new analysis method to discriminate incident
angles by using shower shape information obtained with the finer granularity. By applying the
new method, one of the backgrounds, the KL-> γ γ decay in the beam halo, was estimated to
be suppressed by a factor of 50, and the total number of background events was estimated to
be reduced to less than the number of signal events predicted by the Standard Model. |
