Recent PandaX-II Results on Dark Matter Search and PandaX-4T Upgrade - PowerPoint PPT Presentation

Recent PandaX-II Results on Dark Matter Search and PandaX-4T Upgrade Plan Ning Zhou Shanghai Jiao Tong University On behalf of PandaX Collaboration KEK-PH2018, 2018-02-14

Outline • WIMP direct detection • PandaX experiment • PandaX-II operation and results • PandaX-4T upgrade plan • Summary 2

Dark Matter • Strong evidences for the existence of dark matter Collider Indirect production search • DM-SM interaction – Direct detection Direct – Indirection detection search – Collider search 3

Interesting Signatures from Indirect Search • AMS-02 DAMPE 250 ) 2 200 V e G –1 r s 150 –1 s –2 m ( x 100 u DAMPE (this work) l F × H.E.S.S. (2008) 3 H.E.S.S. (2009) E 50 AMS-02 (2014) Fermi-LAT (2017) 0 10 100 1,000 10,000 Energy (GeV) 4

Dark Matter Direct Detection • DM: velocity ~1/1500 c, mass ~100 GeV, KE ~ 20 keV • Nuclear recoil (NR): recoiling energy ~10 keV • Electron recoil (ER): 10 -4 suppression in energy, very difficult to detect 5

China Jinping Underground Laboratory • China Jinping underground laboratory (CJPL) – Deepest (6800 m.w.e )! – Horizontal access! 2430m � 6 �

PandaX Experiment • P article and A strophysical X enon Experiments – Formed in 2009, ~50 people • PandaX-II 580kg results published at PRLs – World-leading exclusion limit • Future: PandaX-xT multi-ton DM experiments Phase II: Phase I: 500 kg DM 120 kg DM 2009-2014 2014-2018 7

PandaX-II: Dual-phase Xenon TPC • Dark matter detection in Xenon detector • Incoming DM collide with Xenon atom – S1 ： scintillation light in LXe upon scattering – S2 ： scintillation light in GXe due to ionized electron • Reconstruct collision energy and 3-D position 8

PandaX-II run history Mar. 9 – June 30, Nov. 2016 – Mar. 2017, 2 nd distillation low background with 10-fold reduction of campaign and Kr (Run9, 79.6 days) recommissioning 2016 2017 2015 Nov. 22 – Dec. 14, Physics Apr.22 – July15, Jul – Oct, ER commission (Run8, 19.1 dark matter data calibration & days, stopped due to high taking (Run10, tritium removal Krypton background) 77.1 days) • Run9 =79.6 days, exposure: 26.2 ton-day • Run10 = 77.1 days, exposure: 27.9 ton-day • Largest reported DM exposure to date 9

Improvement since PandaX-II 2016 results • Run 9 + Run 10: exposure doubles • FPGA-based trigger – real-time programmable noise rejection algorithm – lowering the trigger threshold • Channel-by-channel SPE efficiency (ε ZLE ) – Average efficiency at S1 threshold ~80% JINST 12 (2017) no.08, T08004 • Improved detector ER/NR response model – Calibration 1 • 2.5 times reduction in background 0.8 – Kr85 ↓ 6 times ZLE efficiency 0.6 – Accidental ↓ 3 times Run10 LED – Xe127 ↓ 20 times 0.4 0.2 0 2 3 10 10 10 S1 [PE] 10

Electron Lifetime Electron lifetime on average 800 µ s (1.4 m drift distance) in Run • 10, and generally stable Significantly improved from Run 9 • 1200 1200 1000 1000 s] 800 800 µ Lifetime [ 600 600 - e 400 400 Leak in circulation 200 200 Power failure loop found 0 0 Apr.29 May.29 Apr.24 May.24 Feb.29 Mar.30 Jun.28 Jun.23 Jul.23 2016 2016 2016 2016 2016 2017 2017 2017 2017 11

Calibration ER calibration using tritiated methane (pioneered by LUX) Neutron calibration: AmBe source deployed (Energy Selected data with electron lifetime ~700 µ s, spectrum measured in ~8000 low energy ER events Daya Bay detector) 12

NR & ER data Open Red circles: AmBe data Solid Black dots: Tritium data Solid Blue line: Run9+Run10 median AmBe band median 99.9% NR acceptance from MC Events leaked below the NR median: 0.53(8)% 13

Energy spectrum in Run 10 [0,50] keV DM search range Data and expected background in good agreement 14

Distribution of events (run10) Light blue: Data median and 10%/90% quantile AmBe band median 99.9% NR acceptance from MC • Total events: 177 • Expected background below NR median: 1.8 ± 0.5 evts • Observed: 0 – Appears to have a downward fluctuation of background (p value 7% for run9+10) 15

SI WIMP (Run9+Run10) PRL 119, 181302 (2017) • Improved from PandaX-II 2016 limit about 2.5 time for mass>30 GeV • Lowest exclusion at 8.6 × 10 -47 cm 2 at 40GeV/c 2 • Most stringent limit for WIMP-nucleon cross section for mass >100GeV 16

Spin Dependent WIMPs • Only 129 Xe (J =1/2) and 131 Xe (J =3/2) are sensitive to the SD interaction. 17 • × 10 4 •

SD WIMP (Run8+Run9) • Spin-dependent WIMP-nucleon scattering • 3.3x10 4 kg-day exposure • Constraints at 4.1x10 -41 cm 2 on WIMP-neutron for 40 GeV WIMP Phys. Rev. Lett. 118, 071301 (2017) 18

Axion (Run9) • Solar Axion and Axion-like Particles 90 Total background Data 80 Xe127 Kr85 + other ER • ER signal, E < 25 keV ee Accidental NR 70 -5 10 keV/cc SA 16 keV/cc ALPs Events/1 keV 60 • Leading upper limits are set, paper is 50 being prepared. 40 30 20 Phys. Rev. Lett. 119, 181806 (2017) 10 0 0 5 10 15 20 25 E (keV ) Solar Axion comb ee Galactic Axion-like Particle 19

Inelastic scattering • Mass splitting δ between two different state of WIMPs • Limited phase space due to the minimal velocity • The signal rate decreases with the increasing of the mass splitting. • Minimal recoil mass exists. • Signal band moves to higher energy region with the increasing of mass splitting. 20

Detection efficiency for Inelastic Scattering • Expand the S1 signal window to (3, 100) PE. – 68.6 keV nr (18.3 keV ee ) Better efficiency for high energy event with the expansion of signal window. 21

Inelastic (Run9) • Inelastic DM beyond 1TeV in mass Squares from the interpretation of the CRESST high recoil energy events. WIMP mass = 1 TeV WIMP mass = 10 TeV Phys. Rev. D96, 102007 (2017) 22

PandaX – in Future • PandaX-4T for DM search • PandaX-III for 0vbb search Pa Pand ndaX-II: II: 500 k kg Pand Pa ndaX-xT xT: : Pand Pa ndaX-III: III: 200 k kg t to Pa Pand ndaX-I: I: 120 k kg DM e experiment DM e experiment multi-ton ( mu (~4-T) T) 1 t ton H HP g gas 13 136 Xe Xe 2009 2009-20 2014 2014-20 20 2018 DM e experiment 0vDBD e experiment Fu Future Future Fu CJPL-I CJPL-II 23

CJPL-II 8 experimental Halls, 14(H)x 14(W)x65(L) m each. • Dark matter, 0vDBD, nuclear astrophysics, low background experiments • PandaX CDEX 24

New Experiment Hall at CJPL-II Water Shielding • Experiment Hall – 5000Ton pure water – U/Th <10 -14 g/g Rn ctrl. • – <1mBq/m 3 in water; – ~10Bq/m 3 in the cave Fresh air • Water Tank 25

PandaX-4T ������ �� • Drift region: F ~1.2m ， H ~1.2m – Xenon in sensitive region ~4ton ������������ �������2���� Top PMT array, 3” �������� �������%� ���������� Top Cu plate ���� ���������� ��������� ����� Teflon supporter ����������� ��� ����� Electrodes and shaping rings ��� ������ Bottom Cu plate ���� ��S��� �������� ������ �� �������� ���� �������2���� ������������ Bottom PMT array 3” �������%� ! Veto System 26 ���2����� ������ �������� ����2���� ��1������ � ������2 � ������8�� ��9����� �S����2 ��� ����������� ����������� ����� � ��)������������������s������ ),. �m� �����业s���～���������������s������ � ) ��m��� G:�A� ���？��～����������������C� ��r��������������？�����������m������ �����～���—？��s������—�������������� ���C( ��rm�� C( ������ C��C( ������������～� �s�×��������r��������r���两�m������ C( ��� C� ���������������m��������������� �������C(��s�±������������C(��������m ��sC� � C( �������������������������m��� �������������������sC( ������—�������

R&D in progress • 27

Background Simulation • Simulate the ER and NR backgrounds – Detector materials: inner/outer vessels, flanges, copper plates, electrodes, PTFE materials, PMTs etc – Radioactivity in xenon: 85 Kr, 222 Rn, 136 Xe – Neutrino: electron scattering and coherent nucleus scattering NR from materials ER from materials 28