CsI calorimeter for the J-PARC KOTO experiment Sato, K.; Lee, J.W.; Banno, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2020, Letnik:
982, Številka:
C
Journal Article
Recenzirano
Odprti dostop
An electromagnetic calorimeter made of undoped CsI crystals is used in the J-PARC KOTO experiment to search for new physics beyond the standard model with the KL→π0νν̄ decay. The calorimeter is ...designed to operate in vacuum of 0.1 Pa and in a high-rate environment where the counting rate due to KL decays is O(100) kHz. A special method to calibrate the calorimeter during the data taking without using a tracking system for charged particles is reported. The energy, position, and timing resolutions of the calorimeter were evaluated in several beam tests, and the resolutions satisfy the required performance. The energy resolution with the total energy E is 0.66⊕1.81∕EGeV% in the inner region of the calorimeter.
The Outer-Edge Veto (OEV) counter subsystem for extra-photon detection from the backgrounds for the KL0→π0νν¯ decay is located at the outer edge of the endcap CsI calorimeter of the KOTO experiment ...at J-PARC. The subsystem is composed of 44 counters with different cross-sectional shapes. All counters are made of lead and scintillator plates and read out through wavelength-shifting fibers. In this paper, we discuss the design and performances of the OEV counters under heavy load (~8tons/m2) in vacuum. For 1-MeV energy deposit, the average light yield and time resolution are 20.9 photo-electrons and 1.5ns, respectively. Although no pronounced peak by minimum-ionizing particles is observed in the energy distributions, an energy calibration method with cosmic rays works well in monitoring the gain stability with an accuracy of a few percent.
The KOTO (
$K^0$
at Tokai) experiment aims to observe the CP-violating rare decay
$K_L \rightarrow \pi ^0 \nu \bar {\nu }$
by using a long-lived neutral-kaon beam produced by the 30 GeV proton beam ...at the Japan Proton Accelerator Research Complex. The
$K_L$
flux is an essential parameter for the measurement of the branching fraction. Three
$K_L$
neutral decay modes,
$K_L \rightarrow 3\pi ^0$
,
$K_L \rightarrow 2\pi ^0$
, and
$K_L \rightarrow 2\gamma $
, were used to measure the
$K_L$
flux in the beam line in the 2013 KOTO engineering run. A Monte Carlo simulation was used to estimate the detector acceptance for these decays. Agreement was found between the simulation model and the experimental data, and the remaining systematic uncertainty was estimated at the 1.4% level. The
$K_L$
flux was measured as
$(4.183 \pm 0.017_{{\rm stat.}} \pm 0.059_{{\rm sys.}}) \times 10^7$
$K_L$
per
$2\times 10^{14}$
protons on a 66-mm-long Au target.
We searched for the CP-violating rare decay of the neutral kaon, KL→π0νν¯, in data from the first 100 hours of physics running in 2013 of the J-PARC KOTO experiment. One candidate event was observed ...while 0.34±0.16 background events were expected. We set an upper limit of 5.1×10−8 for the branching fraction at the 90% confidence level (C.L.). An upper limit of 3.7×10−8 at the 90% C.L. for the KL→π0X0 decay was also set for the first time, where X0 is an invisible particle with a mass of 135 MeV/c2.
A pulse shape difference between photons and neutrons was observed in the output signals of scintillation light from the un-doped CsI calorimeter of the KOTO experiment for the KL→π0νν̄ decay. We ...developed a discrimination method to reject neutrons and to accept photons in the deposited energy range from 0.1 to 2 GeV. The method rejects 67% of neutron-induced single hadronic clusters and 86% of neutron-induced two-cluster events while keeping more than 90% of photon-induced single electromagnetic clusters and two-photon events.
CsI calorimeter for the J-PARC KOTO experiment Sato, K.; Lee, J. W.; Banno, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2020, Letnik:
982, Številka:
C
Journal Article
Recenzirano
Odprti dostop
An electromagnetic calorimeter made of undoped CsI crystals is used in the J-PARC KOTO experiment to search for new physics beyond the standard model with the KL → π 0 νν¯ decay. The calorimeter is ...designed to operate in vacuum of 0.1 Pa and in a high-rate environment where the counting rate due to KL decays is O(100) kHz. A special method to calibrate the calorimeter during the data taking without using a tracking system for charged particles is reported. The energy, position, and timing resolutions of the calorimeter were evaluated in several beam tests, and the resolutions satisfy the required performance. Finally, the energy resolution with the total energy E is 0.66 ⊕ 1.81/ √ EGeV% in the inner region of the calorimeter.
The relationship between left ventricular wall motion worsening (new asynergy; newly developed or worsened asynergy) in the affected part of old myocardial infarction during exercise two-dimensional ...echocardiography and the wall thickness at diastole was evaluated in 20 patients with more than 51% diameter stenosis in only the infarcted related artery using symptom-limited graded supine bicycle exercise test and two-dimensional echocardiography. End-diastolic wall thickness at normal part of the wall (WtdN) and infarcted parts (WtdI) on the parasternal short-axis view at the papillary muscle level at rest were measured and the wall thickness ratio, WtdI/WtdN x 100(%), was calculated. The rate pressure product at the time when new asynergy appeared and the appearance time of new asynergy after starting exercise were measured in seconds. Mean values for the 20 patients were wall thickness ratio of 75.7 +/- 10.0% (mean +/- SD), new asynergy appearance time of 219 +/- 116 sec after exercise and rate pressure product of 14,209 +/- 2,997 mmHg. beat/min. Smaller wall thickness ratio was associated with lower rate pressure product levels (r = 0.696, p < 0.01) and shorter appearance time of new asynergy (r = 0.772, p < 0.01). There was no significant correlation between the percentage diameter stenosis of the infarct-related artery and appearance time of new asynergy or rate pressure product. New asynergy appeared at a specific infarcted part of the wall, and thinner walls were associated with shorter appearance time of new asynergy with lower rate pressure product levels, regardless of the severity of stenosis of the infarct-related artery.
A 48-year-old man was diagnosed with isolated noncompaction of the left ventricular myocardium. He had been suffering from dyspnea during light exercise since early February 1997, which worsened with ...time. Eventually, he visited our hospital on February 14. He was admitted urgently because orthopnea was observed and chest radiogram showed massive left pleural effusion. The diagnoses were pulmonary tuberculosis and tuberculous pleuritis. Echocardiography at admission showed generalized hypokinesis of the left ventricle, so we suspected that his condition was complicated by myocarditis. However, virus antibody levels were not elevated, and no obvious findings compatible with myocarditis or cardiomyopathy were obtained by right ventricular myocardial biopsy. Left ventricular contractility remained low and a trabecular mesh structure was seen at the left ventricular apex. Thus, the diagnosis was isolated noncompaction of the left ventricular myocardium. This disorder has been highlighted in pediatric patients, but few adult cases have been reported.
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