LEADER 04529nam 22006135 450 001 9910427691003321 005 20200820141548.0 010 $a981-15-6422-1 024 7 $a10.1007/978-981-15-6422-2 035 $a(CKB)4100000011392567 035 $a(DE-He213)978-981-15-6422-2 035 $a(MiAaPQ)EBC6313940 035 $a(PPN)250215357 035 $a(EXLCZ)994100000011392567 100 $a20200820d2020 u| 0 101 0 $aeng 135 $aurnn|008mamaa 181 $ctxt$2rdacontent 182 $cc$2rdamedia 183 $acr$2rdacarrier 200 10$aSearch for the Decay K_L ? ?^0\nu\bar{\nu} at the J-PARC KOTO Experiment /$fby Kota Nakagiri 205 $a1st ed. 2020. 210 1$aSingapore :$cSpringer Singapore :$cImprint: Springer,$d2020. 215 $a1 online resource (XVI, 151 p. 121 illus., 109 illus. in color.) 225 1 $aSpringer Theses, Recognizing Outstanding Ph.D. Research,$x2190-5053 311 $a981-15-6421-3 327 $aIntroduction -- The KOTO Experiment -- Data Taking -- Event Reconstruction -- Monte Carlo Simulation -- Analysis of the KL ??0?? and KL ??0X0 Searches -- Discussion -- Conclusion -- Appendix. 330 $aThis book reports on a new result from the KL??0?? search at the J-PARC KOTO experiment, which sets an upper limit of 3×10-9 for the branching fraction of the decay at the 90% confidence level, improving the previous best limit by an order of magnitude. To explain the matter?antimatter asymmetry in the universe, still unknown new physics beyond the standard model (SM) that breaks CP symmetry is necessary. The rare decay of a long-lived neutral K meson, KL??0??, is a CP-violating decay. It is an excellent probe to search for new physics because new physics can contribute to the decay and change its branching fraction, while the SM is as small as 3×10-11. However, it is extremely difficult to search for because all of the decay products are neutral and two neutrinos are undetectable. The KL??0?? signal is identified by measuring two photons from a ?0 with a calorimeter and confirming the absence of any other detectable particles with hermetic veto counters. The book contributes to the analysis of neutron-induced backgrounds which were the dominant background sources in the search. For the background caused by two consecutive hadronic showers in the calorimeter due to a neutron, the author evaluated the background yield using a data-driven approach. For another background caused by an ? meson production?? decays two photons?by a neutron that hits a veto counter near the calorimeter, the author developed an original analysis technique to reduce it. The book also contributes to the analysis of the normalization modes (KL?3?0, KL?2?0, KL?2?) to measure KL yield, the estimation of the signal acceptance based on a simulation, and the evaluation of the trigger efficiency. As a result, significant improvements in the measurement were achieved, and this is an important step in the continuing higher sensitivity search, which can reach new physics with the energy scales up to O(100-1000 TeV). 410 0$aSpringer Theses, Recognizing Outstanding Ph.D. Research,$x2190-5053 606 $aNuclear physics 606 $aHeavy ions 606 $aParticle acceleration 606 $aElementary particles (Physics) 606 $aQuantum field theory 606 $aNuclear Physics, Heavy Ions, Hadrons$3https://scigraph.springernature.com/ontologies/product-market-codes/P23010 606 $aParticle Acceleration and Detection, Beam Physics$3https://scigraph.springernature.com/ontologies/product-market-codes/P23037 606 $aElementary Particles, Quantum Field Theory$3https://scigraph.springernature.com/ontologies/product-market-codes/P23029 615 0$aNuclear physics. 615 0$aHeavy ions. 615 0$aParticle acceleration. 615 0$aElementary particles (Physics). 615 0$aQuantum field theory. 615 14$aNuclear Physics, Heavy Ions, Hadrons. 615 24$aParticle Acceleration and Detection, Beam Physics. 615 24$aElementary Particles, Quantum Field Theory. 676 $a539.72162 700 $aNakagiri$b Kota$4aut$4http://id.loc.gov/vocabulary/relators/aut$0887772 801 0$bMiAaPQ 801 1$bMiAaPQ 801 2$bMiAaPQ 906 $aBOOK 912 $a9910427691003321 996 $aSearch for the Decay K_L ? ?^0\nu\bar{\nu} at the J-PARC KOTO Experiment$91983069 997 $aUNINA