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Title: Experimental Study of the Rare Neutral-Kaon Decays at J-PARC: Final Technical Report

Abstract

Understanding the origin of CP violation is currently one of the most forefront issues in elementary particle physics. Together with a better understanding of quark mixing and neutrino mixing phenomena, it is one of the central goals of particle physics, and has been pursued vigorously in many experiments. The very rare decay K_L -> pi^0 nu bar-nu provides one of the best probes for understanding the original of CP violation in the quark sector. Particularly, theoretical uncertainties are very small in the Standard Model (SM) calculations, and the value therefore most suitable to be tested for beyond SM contributions. J-PARC E14 (also known as KOTO) aims to reach Standard Model sensitivity and beyond with Stage-1 and Stage-2. KOTO acquired 100 hours beam data in May 2013 and the result has been accepted for publication. From 2015-16, KOTO increased the data set by a factor of twenty, which will allow a limit to be set at the Grossman-Nir bound. This bound is valid in virtually any extension of the Standard Model. By comparing this model-independent bound and SM prediction, it is clear that there is considerable room for new physics. Analysis on these collected data sets shows neutron interactions which mimicmore » the two-photon signal could become a potential background. To discriminate neutron background from the photon signal, one important tool, as shown in current data, is to perform detailed waveform analysis of the signal from the phototubes. To fully capture the calorimeter pulse shape with best fidelity from 100 out of the 2700 channels of CsI, we built the 500 MSPS (Mega Samples Per Second) with 14-bit digitizers. With KOTO Stage-2 currently in the planning stages, we started R&D work on a full width, but length scalable photon veto barrel detector with detailed layout of active detector elements.« less

Authors:
 [1]
  1. The University of Chicago
Publication Date:
Research Org.:
The University of Chicago
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1490191
Report Number(s):
DOE-CHICAGO-18219
DOE Contract Number:  
SC0018219
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Electromagnetic calorimeter, elementary particle physics, Beyond Standard Model

Citation Formats

Wah, Yau Wai. Experimental Study of the Rare Neutral-Kaon Decays at J-PARC: Final Technical Report. United States: N. p., 2019. Web. doi:10.2172/1490191.
Wah, Yau Wai. Experimental Study of the Rare Neutral-Kaon Decays at J-PARC: Final Technical Report. United States. doi:10.2172/1490191.
Wah, Yau Wai. Thu . "Experimental Study of the Rare Neutral-Kaon Decays at J-PARC: Final Technical Report". United States. doi:10.2172/1490191. https://www.osti.gov/servlets/purl/1490191.
@article{osti_1490191,
title = {Experimental Study of the Rare Neutral-Kaon Decays at J-PARC: Final Technical Report},
author = {Wah, Yau Wai},
abstractNote = {Understanding the origin of CP violation is currently one of the most forefront issues in elementary particle physics. Together with a better understanding of quark mixing and neutrino mixing phenomena, it is one of the central goals of particle physics, and has been pursued vigorously in many experiments. The very rare decay K_L -> pi^0 nu bar-nu provides one of the best probes for understanding the original of CP violation in the quark sector. Particularly, theoretical uncertainties are very small in the Standard Model (SM) calculations, and the value therefore most suitable to be tested for beyond SM contributions. J-PARC E14 (also known as KOTO) aims to reach Standard Model sensitivity and beyond with Stage-1 and Stage-2. KOTO acquired 100 hours beam data in May 2013 and the result has been accepted for publication. From 2015-16, KOTO increased the data set by a factor of twenty, which will allow a limit to be set at the Grossman-Nir bound. This bound is valid in virtually any extension of the Standard Model. By comparing this model-independent bound and SM prediction, it is clear that there is considerable room for new physics. Analysis on these collected data sets shows neutron interactions which mimic the two-photon signal could become a potential background. To discriminate neutron background from the photon signal, one important tool, as shown in current data, is to perform detailed waveform analysis of the signal from the phototubes. To fully capture the calorimeter pulse shape with best fidelity from 100 out of the 2700 channels of CsI, we built the 500 MSPS (Mega Samples Per Second) with 14-bit digitizers. With KOTO Stage-2 currently in the planning stages, we started R&D work on a full width, but length scalable photon veto barrel detector with detailed layout of active detector elements.},
doi = {10.2172/1490191},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {1}
}