Observation of Excess Electronic Recoil Events in XENON1T 風間慎吾 (名古屋大学 KMI & 高等研究院) @基研研究会 素粒子物理学の進展２０２０
確率は非常に小さいがWIMPも身の回りの物質(原子核)と相互作用をする(原子核反跳)。 原子核が受け取る反跳エネルギーを検出する(光, 電子, フォノン, etc)。 WIMPの探索方法(直接探索) XENON1T実験 • 液体キセノンを3.2トン(有効体積~1トン)を用いた直接探索実験 • 低質量&高質量の両極限(100MeV - TeV)で、世界で最も厳しい制限を与えている。 • 実験自体は既に終了していて、現在XENONnT実験へとアップグレード中(後述) XENON1T実験のWIMP探索結果 Direct Dark Matter Detection 2
太陽アクシオン: Axio-electric effect (光電効果と似た効果, g ae ) 太陽ニュートリノ: 電子散乱 (elastic scattering ) 太陽アクシオンや太陽ニュートリノの探索方法: 電子反跳 電子反跳事象の探索 • 通常、電子反跳事象はWIMP探索の背景事象(BG) • WIMP searchと比べてBG量が多いので、BGをより精密に評価し、そこからの超過を探す WIMPと原子核の相互作用 (原子核反跳) 太陽アクシオン・太陽ニュートリノ (今回はこちら！) <latexit sha1_base64="IX9cE8LYzUnKEJBcdKQl9h5f6E=">AB7XicdVDLSgNBEJz1GeMr6tHLYBA8LbMxmM0t6MVjBPOAZAmzk04yZnZnmZkVwpJ/8OJBEa/+jzf/xslDUNGChqKqm+6uMBFcG0I+nJXVtfWNzdxWfntnd2+/cHDY1DJVDBpMCqnaIdUgeAwNw42AdqKARqGAVji+mvmte1Cay/jWTBIjqM+YAzaqzUHPYyCtNeoUjcykWpWvUwcf0yIcS3pEp8v+xjzyVzFNES9V7hvduXLI0gNkxQrTseSUyQUWU4EzDNd1MNCWVjOoSOpTGNQAfZ/NopPrVKHw+kshUbPFe/T2Q0noShbYzomakf3sz8S+vk5qBH2Q8TlIDMVsGqQCG4lnr+M+V8CMmFhCmeL2VsxGVFmbEB5G8LXp/h/0iy53rlbuikXa5fLOHLoGJ2gM+ShCqha1RHDcTQHXpAT+jZkc6j8+K8LlpXnOXMEfoB5+0TREOPmQ=</latexit> Direct Dark Matter Detection 3 e g ae e a
水に換算して3600mの深さに実験装置をインストール (active) 220 Rn (ER) - 83m Kr (ER), - Internal calibration - Neutron generator (NR) 241 AmBe (NR) - External calibration structure for TPC Cryostat and support - 84 8-inch PMTs (R5912) Cherenkov Muon Veto LXe mass: 3.2 t(total), 2.0t Water tank Xenon storage - 700 t of pure water Cryogenics, and purification DAQ and slow control (ReStoX), - handling and Kr distillation TPC - 248 3-inch PMTs (R11410-21, QE~34%@178nm) The XENON1T/nT Experiment @ LNGS in Italy 4
昨日、ちょうど液体キセノンをfillし始めた！ 名大、神戸大、IPMUは先月末にDARWINにも参加！ The XENON + DARWIN Program 5
1トン・1keV当たり、約5日待って1電子反跳BG事象あるかないか 1000-1300 XENON1T ~0.02 0.2 0.8 2.6 5.3 ~4000 306 118 34 XENONnT PandaX LUX XENON100 [events/(keV ton day)] Low-energy ER background Fiducial mass [kg] History of LXe TPCs 6 × 4 × 1/10
light ( S2 ) - Primary scintillation light ( S1 ) is produced promptly at the 1m ~8kV/cm ~0.1kV/cm - Z position: electron drift time, Δt (s1, s2 ) - X,Y position: S2 hit-pattern in top PMT array - Event vertex reconstruction in 3D space region, where they form secondary proportional scintillation - Others are extracted above the liquid surface into gas phase - Some recombine with ions ̶> more scintillation light ( S1 ) electric field - Ionization electrons drift up through the LXe in the applied interaction site 7 LXe TPC: Working Principle Dark Matter Detection with LXe TPCs Energy - S1 area - S2 area Position - x-y (S2 signal) - z (drift time) Interaction type - S2/S1 ratio ( ER / NR ) - Particle type discrimination: (S2/S1)γ,e > (S2/S1)WIMP Electric Recoil Nuclear Recoil S2( 電子信号 ) [PE] N i escape proportional ionization ionization scintillation e - drift, recombination acceleration (S2) in gas phase excitation de-excitation E 0 N ex scintillation atomic motion Electric Recoil (S1) Nuclear Recoil heat S1( 光信号 ) [PE] 7
Most stringent result on WIMP Dark Matter down to 3 GeV/c 2 masses One ton-year of search for WIMPs induced nuclear recoils threshold: ~5 keV nr XENON1T WIMP Searches - 2018 (NR Search) 8
検出器部材からの放射線(ガンマ線)を除くため、有効体積はWIMPより小さい。 - 電子反跳BGの絶対量を減らす - 既知のBG(放射性ラドン・クリプトンなど)を精密に評価し、超過を探す threshold: ~1 keV ee 太陽アクシオンやALPs, Dark Photon探索における戦略 XENON1T Solar-Axion / ALPs Searches - 2020 (ER Search) 9
S1, S2はPMTで測定される量! <latexit sha1_base64="d6IcuMqTVy/aBIabuKEG5iEtPeM=">ACL3icbVDLSsNAFJ34rPUVdelmsAgVoSRF0I1QFMWVLQPaEKYTCbt0MmDmYlQv7Ijb/SjYgibv0LJ21Ab0wcO453LnHjdmVEjDeNUWFpeWV1ZLa+X1jc2tbX1nty2ihGPSwhGLeNdFgjAakpakpFuzAkKXEY67vAy1zuPhAsahQ9yFBM7QP2Q+hQjqShHv76C57B6TxIPHUAGSHUELe5GEnVyfI5wem9mad/MHUVfV39x+noFaNmTArOA7MAFVBU09HlhfhJChxAwJ0TONWNop4pJiRrKylQgSIzxEfdJTMEQBEXY6uTeDh4rxoB9x9UIJ+zviRQFQowCVzkDJAdiVsvJ/7ReIv0zO6VhnEgS4ukiP2FQRjAPD3qUEyzZSAGEOV/hXiAVCBSRVxWIZizJ8+Ddr1mGjXz7qTSuCjiKIF9cACqwASnoAFuQBO0AZPYAzewLv2rL1oH9rn1LqgFTN74E9pX9+4qXp</latexit> <latexit sha1_base64="d6IcuMqTVy/aBIabuKEG5iEtPeM=">ACL3icbVDLSsNAFJ34rPUVdelmsAgVoSRF0I1QFMWVLQPaEKYTCbt0MmDmYlQv7Ijb/SjYgibv0LJ21Ab0wcO453LnHjdmVEjDeNUWFpeWV1ZLa+X1jc2tbX1nty2ihGPSwhGLeNdFgjAakpakpFuzAkKXEY67vAy1zuPhAsahQ9yFBM7QP2Q+hQjqShHv76C57B6TxIPHUAGSHUELe5GEnVyfI5wem9mad/MHUVfV39x+noFaNmTArOA7MAFVBU09HlhfhJChxAwJ0TONWNop4pJiRrKylQgSIzxEfdJTMEQBEXY6uTeDh4rxoB9x9UIJ+zviRQFQowCVzkDJAdiVsvJ/7ReIv0zO6VhnEgS4ukiP2FQRjAPD3qUEyzZSAGEOV/hXiAVCBSRVxWIZizJ8+Ddr1mGjXz7qTSuCjiKIF9cACqwASnoAFuQBO0AZPYAzewLv2rL1oH9rn1LqgFTN74E9pX9+4qXp</latexit> <latexit sha1_base64="d6IcuMqTVy/aBIabuKEG5iEtPeM=">ACL3icbVDLSsNAFJ34rPUVdelmsAgVoSRF0I1QFMWVLQPaEKYTCbt0MmDmYlQv7Ijb/SjYgibv0LJ21Ab0wcO453LnHjdmVEjDeNUWFpeWV1ZLa+X1jc2tbX1nty2ihGPSwhGLeNdFgjAakpakpFuzAkKXEY67vAy1zuPhAsahQ9yFBM7QP2Q+hQjqShHv76C57B6TxIPHUAGSHUELe5GEnVyfI5wem9mad/MHUVfV39x+noFaNmTArOA7MAFVBU09HlhfhJChxAwJ0TONWNop4pJiRrKylQgSIzxEfdJTMEQBEXY6uTeDh4rxoB9x9UIJ+zviRQFQowCVzkDJAdiVsvJ/7ReIv0zO6VhnEgS4ukiP2FQRjAPD3qUEyzZSAGEOV/hXiAVCBSRVxWIZizJ8+Ddr1mGjXz7qTSuCjiKIF9cACqwASnoAFuQBO0AZPYAzewLv2rL1oH9rn1LqgFTN74E9pX9+4qXp</latexit> <latexit sha1_base64="d6IcuMqTVy/aBIabuKEG5iEtPeM=">ACL3icbVDLSsNAFJ34rPUVdelmsAgVoSRF0I1QFMWVLQPaEKYTCbt0MmDmYlQv7Ijb/SjYgibv0LJ21Ab0wcO453LnHjdmVEjDeNUWFpeWV1ZLa+X1jc2tbX1nty2ihGPSwhGLeNdFgjAakpakpFuzAkKXEY67vAy1zuPhAsahQ9yFBM7QP2Q+hQjqShHv76C57B6TxIPHUAGSHUELe5GEnVyfI5wem9mad/MHUVfV39x+noFaNmTArOA7MAFVBU09HlhfhJChxAwJ0TONWNop4pJiRrKylQgSIzxEfdJTMEQBEXY6uTeDh4rxoB9x9UIJ+zviRQFQowCVzkDJAdiVsvJ/7ReIv0zO6VhnEgS4ukiP2FQRjAPD3qUEyzZSAGEOV/hXiAVCBSRVxWIZizJ8+Ddr1mGjXz7qTSuCjiKIF9cACqwASnoAFuQBO0AZPYAzewLv2rL1oH9rn1LqgFTN74E9pX9+4qXp</latexit> reconstruct energy of each event extract g1/g2 from calibration data, use it to g1 and g2: detector-specific gain constants <latexit sha1_base64="I+WtHbz3tmGrDshBRDeMZK46pMs=">AB9XicdVBNSwMxEJ31s9avqkcvwSJ4KrtVcb0VvXisYD+gXUs2zbah2WxIskpZ+j+8eFDEq/Fm/GtF1BR8MPN6bYWZeKDnTxnU/nIXFpeWV1cJacX1jc2u7tLPb1EmqCG2QhCeqHWJNORO0YZjhtC0VxXHIaSscXU791h1VmiXixowlDWI8ECxiBsr3XalSqRJkOhlcjplcpuxZ0BWXLu+37VEs+vnro+8nKrDnqvdJ7t5+QNKbCEI617niuNEGlWGE0mxm2oqMRnhAe1YKnBMdZDNrp6gQ6v0UZQoW8Kgmfp9IsOx1uM4tJ0xNkP925uKf3md1ER+kDEhU0MFmS+KUo7sn9MIUJ8pSgwfW4KJYvZWRIZYWJsUEUbwten6H/SrFa840r1+qRcu8jKMA+HMAReHAGNbiCOjSAgIHeIJn595dF6c13nrgpP7MEPOG+fPk2TAg=</latexit> where W = 13.7 eV/quanta <latexit sha1_base64="798E/ml8/AhDrg4V6USVIu0t2/Q=">AB9HicdVBNSwMxEJ31s9avqkcvwSJ4KrtVcb0VvXisYD+gXUo2zbah2WRNsoWy9Hd48aCIV3+MN/+NabuCij4YeLw3w8y8MOFMG9f9cJaWV1bX1gsbxc2t7Z3d0t5+U8tUEdogkvVDrGmnAnaMxw2k4UxXHIaSscXc/81pgqzaS4M5OEBjEeCBYxgo2Vgm6iZGIkEr2MTnulsltx50CWXPq+X7XE86vnro+83CpDjnqv9N7tS5LGVBjCsdYdz01MkGFlGOF0WuymiaYjPCAdiwVOKY6yOZHT9GxVfoksqWMGiufp/IcKz1JA5tZ4zNUP/2ZuJfXic1kR9kTCSpoYIsFkUpR/bNWQKozxQlhk8swUQxeysiQ6wMTanog3h61P0P2lWK95pXp7Vq5d5XEU4BCO4AQ8uIAa3EAdGkDgHh7gCZ6dsfPovDivi9YlJ585gB9w3j4BZauShQ=</latexit> Energy Reconstruction with LXe TPC 10 E = ( N ph + N e ) · W = ( S 1 g 1 + S 2 g 2 ) · W S1 S2 ∝ n ph ∝ n e
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