KOTO K ( ) 1 - PowerPoint PPT Presentation

KOTO 実 験 に よ る K 中 間 子 稀 崩 壊 探 索 南 條 創 ( 京 都 大 学 ) 1

Contents ● Motivation ● KOTO Experiment ● Prospect 2

Motivation 3

New Physics は あ る の か ？ 4

● 2008 : Kobayashi and Maskawa – CP-violation was established. – The size is not enough to explain matter dominant universe. – New CP-violating particle is expected in higher energy scale. ● 2013 : Englert and Higgs – Higgs was discovered but it is far from closing the book. – New physics in high energy scale is expected to stabilize Higgs mass. – SUSY, little Higgs, Compositeness, Extra Dimension, …? – Dark matter? 5

● New Physics は 存 在 す る 。 – 物 質 優 勢 宇 宙 – Dark Matter – ... ● ど う や っ て 探 す ？ 6

New Physics Search ● High Energy Frontier ↔ High Intensity Frontier – High energy frontier → direct production of heavy particle – High intensity frontier → indirect access, high energy reach 一 瞬 の 高 エ ネ ル ギ ー ス ケ ー ル → 稀 な プ ロ セ ス ● 標 準 理 論 の 抑 制 ● GIM, CKM,Helicity...suppression ● 精 密 な 理 論 予 測 ● Multi-process approach 多 方 面 か ら フ レ ー バ 構 造 を 明 ら か に ● Correlation is important. ● CP-violation is another guide. explanation of matter dominant universe 7

Why Kaon? Blanke '13 ● “Generally most powerful” – GIM suppression of u and c quarks – Hierarchical structure of CKM for t quark ● Most suppressed in s → d transition (λ 5 ) – b → d (λ 3 ) , b → s (λ 2 ) u c t d s b 例え B s/d → μμ が SM-like であっても、 s → d は NP でエンハンス可能 8

Bona '07 Ishidori '13 Energy Reach Flavor structure Tree/Strong couple ~1 MFV Generic Loop α S ~0.1 Tree/Strong couple 5 TeV 24000 TeV Loop α W ~0.03 Loop α S 0.5 TeV 2400 TeV Loop α W 0.2 TeV 800 TeV (Bona '07) Generic の 場 合 、 K sector が 最 強 → 10 4 TeV ま で の リ ー チ な ぜ ま だ 見 え な い ？ ↔ Energy scale, Flavor 構 造 Minimal Flavor Violation like な 場 合 、 B と 強 い 相 関 9 (NP で も CKM の 構 造 を 保 持 , 新 し い CPV phase も な い )

● NP > 1 TeV? (ATLAS,CMS) ● Non-MFV like ? (LHCb,CMS) 10 Buras'13

Rare decay ● Strong suppression from CKM Buras '15 – Small theoretical uncertainty ~2% ● – High energy scale Hadron matrix element from tree process Ke3/Kmu3 – Sensitive to new physics beyond the SM CP-violating process ● Related to charged mode ● Grossman-Nir bound : – ● Model-independent inequality w/ iso-spin rotation 11

Status Direct limit 2.6x10 -8 (KEK E391a) 10 -8 Indirect limit 1.5x10 -9 (Grossman-Nir) 10 -9 10 -10 New Physics? SM sensitivity 2.4x10 -11 10 -11 12

SM extension w/ 4 th generation Otto '12 → ruled out Direct search EW precision test Higgs mass 13

from ΔS=2 と ΔS=1 の NP に よ る 変 化 → 同 じ new phase が 支 配 Z'/Z with Left / Right-handed coupling Littlest Higgs with T-parity 14

Buras '15 Input from ε'/ε SM expectation Direct CPV from KL → ππ (Theory) Progress from lattice calculation Left and Right-handed coupling still can enhance Br(KL) MFV Left or Right-handed coupling 15

Buras '15 EW penguin contribute to e'/e in negative interference. Negative correlation btw Br(KL) 16

Buras '15 Left- and right-handed coupling model can enhance Br(KL) 17

Buras '15 18

Littlest Higgs with T-Parity Blanke '15 Symmetry breaking scale 19

Tanimoto, SUSY at 10-50 TeV Yamamoto '15 ● 10 TeV SUSY → still large enhancement on Br(KL) ● Less correlation btw Br(KL) and ε – 50TeV SUSY still have enhancement factor on Br(KL) 20

Weekly-coupled light Z' Fuyuto '14 with Lμ – Lτ coupling ● Explain g-2 with Mz'<400MeV – also relate to B → Kμμ from E949 experiment 21 KOTO already access here.

KOTO Experiment 22

KOTO : K 0 at TOkai Extraction ● J-PARC Accelerator – High power ↔ Statistics of rare process – Slow extraction ↔ Event pile-up due to high rate ● J-PARC 33kW (June 2015) ~ World-highest class 3GeV 30GeV 400MeV 23

Fixed Target Experiment ● High intensity proton beam+ Primary target – High intensity secondary products ● Beam line – Transport particles of interest ● Reduce unwanted particles – Long life to transport. Gold 15mm x 6mm x 66mm 24 30 GeV proton

Particles mass and life time Bottom Tools for fixed target experiment with high intensity proton driver Lower mass Longer life time Strange Collider has bee a special tool Kaon for fixed target experiment (τ 、 D,B,t) Pion Neutrino source Muon source 25

Kaon ● Low mass (0.5 GeV) ● Long life time (15m) ● Strangeness Good for fixed target → Flavor Changing Neutral Current ● s → d transition – Flavor changing neutral current (GIM) – Strong CKM suppression ● K L → π 0 νν (Br 3x10 -11 in SM) – Direct CP-violation 26

Beam line ● 金標的 + proton ● KL beam line ● 電磁石 (charged) ● 20m 長尺 (short-lived) ● コリメータ (beam halo) → 細くシャープな中性ビーム (KL, γ, neutron) “Pencil Beam” 33kW 6sec cycle 立体角 7.8μsr 4x10 13 proton ~10 7 KL ~40%lost by decay 27

2 nd collimator (4.5+0.5m) Beam plug 1 st collimator （ 4m-long ） Dipole magnet 28

Signal Reconstruction ● 2γ+nothing → Calorimeter + Veto detectors ● Beam constraint → “pencil beam” 6.1m 29

Detector ~2m Veto : γ/charged 10 -4 – 10 -6 reduction 30

History 100hours Detector upgrade 31

1st physics run in 2013 CKM2014 Sensitivity : 1.29x10 -8 (Preliminary) ~ E391a sensitivity with only 100-hour run 1 event in the signal box 87 1 87 0.2±0.1 Number of observed data → Well understood. 9 7.2±0.5 32

Main background source in E391a Halo neutron → π 0 at Upstream detector Downstream detector → Largely reduced. E391a Final (5month) KOTO 1 st Physics run(4days) S.E.S : 1.11x10 -8 S.E.S : 1.29x10 -8 87 87 1 0.2±0.1 9 7.2±0.5 33

Background source in KOTO 87 87 1 0.2±0.1 9 7.2±0.5 CC05 CC06 Beam pipe 34 1m

Run in April-June 2015 ● Physics run ● 5.3 times higher POT ↔ run in May 2013 ● Calibration and special runs Calibration, Physics run in 2015 Special runs 33kW 29kW X5.3 26kW 26kW Physics 24kW Integrated POT for May 2013 35

Check with 3π 0 sample • Calorimeter and KL properties consistent with the run in May 2013. • More detailed calibration is on-going • Study to suppress background Black :April-May 2015 Red :May 2013 Area normalized Area normalized 36

To suppress halo neutron ● Upstream beam window – Kapton 125um → 12.5um – Reduce neutron scattering ● Re-alined collimator – Reduce neutron scattering Hadron interaction events on the collimator inner surface 37

Collimator alignment with new beam profle monitor Lead(1.5mm) Mirror Phosphor plate Re-alined collimators 38

To understand hadron interaction events Scattered at the target Core neutron 10 mm thick Al Contribution by Chonbuk Univ. * Removed in physics run Took Al-target data 70 hours Gammas from π 0 Hadron interaction > 15 times higher statics than May 2013 Reconstructed P T (MeV/c) 39 Reconstructed Z vertex Developing BG reduction with cluster shape (mm)

To suppress low P T events CC05 CC06 Beam pipe Plastic scintillator WLS fiber 1m PMT ● Beam pipe (5mm t) SUS → Aluminum ● Installed Beam Pipe Charged Veto – Plastic scintillator 5-mm thick – Wavelength shifting fber readout ~1/60 reduction expected 40

To suppress K L → 2π 0 Added modules X0: 4 → 6.2 Photon punch-through inefficiency → 1/5 Lead and Acrylic Cherenkov detector In-beam photon veto Lead and Aerogel Cherenkov detector 41

Prospect 42

To suppress K L → 2π 0 more • Install inner barrel detector in winter 2015 • Add 5 X0 to 13.5 X0 of current Main Barrel – Suppress punch-through ineffciency by 1/50. Gluing fber to scintillator was mostly fnished. Module assembly will start soon. Will install it in this winter + Maintenance for existing broken channels in vacuum 43

Plan • NA62 will take 100 events toward 2017 for – Push Grossman-Nir limit down. • We will overcome our background and improve our sensitivity 2015 April-June 2015 Fall 2016 2017 44

Long term plan 45