Search for the Decay K_L → π^0\nu\bar{\nu} at the J-PARC KOTO Experiment / by Kota Nakagiri.

Format:

Book

Author/Creator:

Nakagiri, Kota, author.

Contributor:

SpringerLink (Online service)

Series:

Physics and Astronomy (SpringerNature-11651)

Springer Theses, Recognizing Outstanding Ph.D. Research,. 2190-5053

Springer Theses, Recognizing Outstanding Ph.D. Research, 2190-5053

Language:

English

Subjects (All):

Nuclear physics.

Heavy ions.

Particle acceleration.

Particles (Nuclear physics).

Quantum field theory.

Nuclear Physics, Heavy Ions, Hadrons.

Particle Acceleration and Detection, Beam Physics.

Elementary Particles, Quantum Field Theory.

Local Subjects:

Nuclear Physics, Heavy Ions, Hadrons.

Particle Acceleration and Detection, Beam Physics.

Elementary Particles, Quantum Field Theory.

Physical Description:

1 online resource (XVI, 151 pages) : 121 illustrations, 109 illustrations in color.

Edition:

First edition 2020.

Contained In:

Springer Nature eBook

Place of Publication:

Singapore : Springer Singapore : Imprint: Springer, 2020.

System Details:

text file PDF

Summary:

This book reports on a new result from the KL→π0νν search at the J-PARC KOTO experiment, which sets an upper limit of 3×10-9 for the branching fraction of the decay at the 90% confidence level, improving the previous best limit by an order of magnitude. To explain the matter-antimatter asymmetry in the universe, still unknown new physics beyond the standard model (SM) that breaks CP symmetry is necessary. The rare decay of a long-lived neutral K meson, KL→π0νν, is a CP-violating decay. It is an excellent probe to search for new physics because new physics can contribute to the decay and change its branching fraction, while the SM is as small as 3×10-11. However, it is extremely difficult to search for because all of the decay products are neutral and two neutrinos are undetectable. The KL→π0νν signal is identified by measuring two photons from a π0 with a calorimeter and confirming the absence of any other detectable particles with hermetic veto counters. The book contributes to the analysis of neutron-induced backgrounds which were the dominant background sources in the search. For the background caused by two consecutive hadronic showers in the calorimeter due to a neutron, the author evaluated the background yield using a data-driven approach. For another background caused by an η meson production-η decays two photons-by a neutron that hits a veto counter near the calorimeter, the author developed an original analysis technique to reduce it. The book also contributes to the analysis of the normalization modes (KL→3π0, KL→2π0, KL→2γ) to measure KL yield, the estimation of the signal acceptance based on a simulation, and the evaluation of the trigger efficiency. As a result, significant improvements in the measurement were achieved, and this is an important step in the continuing higher sensitivity search, which can reach new physics with the energy scales up to O(100-1000 TeV).

Contents:

Introduction

The KOTO Experiment

Data Taking

Event Reconstruction

Monte Carlo Simulation

Analysis of the KL →π0νν and KL →π0X0 Searches

Discussion

Conclusion

Appendix.

Other Format:

Printed edition:

ISBN:

978-981-15-6422-2

9789811564222

Access Restriction:

Restricted for use by site license.