Recent results from PandaX- II and status of PandaX-4T

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1 Recent results from PandaX- II and status of PandaX-4T Jingkai Xia (Shanghai Jiao Tong University) On behalf of PandaX Collaboration August 2-5, 2018/8/4 1

2 Outline Dark Matter direct detection PandaX program in China PandaX-II recent results PandaX-4T plan Summary August 2-5, 2018/8/4 2

3 Outline Dark Matter direct detection PandaX program in China PandaX-II recent results PandaX-4T plan Summary August 2-5, 2018/8/4 3

4 Detect Dark Matter in universe Collider production Indirect search Direct search August 2-5, 2018/8/4 4

5 Direct Detection with Dual-phase Xenon TPC Advantages: Liquid Xenon: large atomic mass, excellent self-shielding; TPC: 3D positon reconstruction and fiducialization; Dual-phase: good nuclear/electron recoil discrimination with S2/S1 ratio. August 2-5, 2018/8/4 5

6 Outline Dark Matter direct detection PandaX program in China PandaX-II recent results PandaX-4T plan Summary August 2-5, 2018/8/4 6

7 PandaX collaboration PandaX: Particle and Astrophysical Xenon Experiments (started from 2009) A group of ~50 people Shanghai Jiao Tong University Peking University Shandong University Nankai University Shanghai Institute of Applied Physics Yalong Hydropower Company University of Maryland University of Science & Technology of China China Institute of Atomic Energy Sun Yat-Sen University Lawrence Berkeley National Lab Alternative Energies & Atomic Energy Commission University of Zaragoza Suranaree University of Technology August 2-5, Mini-Workshop@SJTU 2018/8/4 7

8 PandaX location: China Jinping Underground Laboratory 2400m rock 1µ/week/m 2 Horizontal access August 2-5, Mini-Workshop@SJTU 2018/8/4 8

9 PandaX experiments Finished: PandaX-I, , 120kg Running: PandaX-II, 2014 to now, 580kg PandaX-II detector: 60 cm * 60 cm cylindrical TPC 580 kg LXe in sensitive region 55 top + 55 bottom 3 target PMTs 24 top + 24 bottom 1 veto PMTs PandaX-I PandaX-II August 2-5, Mini-Workshop@SJTU 2018/8/4 9

10 PandaX-II detector August 2-5, 2018/8/4

11 Outline Dark Matter direct detection PandaX program in China PandaX-II recent results PandaX-4T plan Summary August 2-5, 2018/8/4 11

12 PandaX-II run history Mar. 9 June 30, low background with -fold reduction of Kr (Run9, 79.6 days) Nov Apr 2017, 2 nd distillation campaign and recommissioning July 2017 Now, 220 Rn/AmBe runs, followed by blinded DM search Nov. 22 Dec. 14, Physics commission (Run8, 19.1 days, stopped due to high Krypton background) Jul Oct, ER calibration & tritium removal Apr.22 July15, dark matter data taking (Run, 77.1 days) Run9 =79.6 days, exposure: 26.2 ton-day Run =77.1 days, exposure: 27.9 ton-day 54 ton-day August 2-5, Mini-Workshop@SJTU 2018/8/4 12

13 PandaX-II Results Previous results: 33 ton-day: spin independent(si) search, PRL 117, (2016) 33 ton-day: spin dependent(sd) search, PRL 118, (2017) 27 ton-day: inelastic scattering search, PRD 96, 2007 (2017) 27 ton-day: axion and ALP search, PRL 119, (2017) 54 ton-day: spin independent(si) search, PRL 119, (2017) Very recent results from collaboration with theorists: (new!) 54 ton-day: light mediator search, PRL 121, (2018) (new!) 54 ton-day: general EFT and spin-dependent search, arxiv: August 2-5, 2018/8/4 13

14 Previous SI and SD results Run8+9(33 t-day) SD Results PRL 118, (2017) Run9+(54 t-day) SI Results PRL 119, (2017) Minimum -n SD cross section limit: Minimum elastic SI cross section limit: 4.1x -41 cm 2 at 40 GeV/c 2 8.6x -47 cm 40 GeV/c 2 August 2-5, Mini-Workshop@SJTU 2018/8/4 14

15 Light Mediator DM-SM Interaction Heavy mediator EFT contact interaction Foundation of main SI/SD results in direct detection Light mediator: mediator m f is compared to or smaller than q Different signal spectrum 1 m 2 φ + q 2 m φ q 1 m φ 2 August 2-5, Mini-Workshop@SJTU 2018/8/4 15

16 New Constraints on DM-nucleon From 54-ton-day exposure data Constraints on DM-nucleon cross section are significantly weakened for light mediator interaction August 2-5, 2018/8/4 16

17 Constraints on Self-Interacting DM Self-interacting DM model can have light mediator mixing with SM particles Mixing parameter e Fine structure in dark sector a Phys.Rept. 730 (2018) 1-57 August 2-5, Mini-Workshop@SJTU 2018/8/4 17

18 General EFT DM-SM Interaction The traditional SI/SD approach: take only leading-order terms in a WIMP-nucleon interaction present a simple treatment on nuclear structure A more sophisticated EFT approach for WIMP scattering was developed: Consider all leading-order and next-to-leading order operators. Combination of four basic terms: Relative perpendicular velocity between the WIMP and the nucleon (v ) Momentum transfer (q) Spins of WIMP (S χ ) Spins of nucleon (S N ) August 2-5, Mini-Workshop@SJTU 2018/8/4 18

19 Non-relativistic EFT operators Parametrizing the WIMP-nucleus interaction in terms of 14 operators, O i : SI The EFT interaction would take the form: SD Each EFT operator has independent couplings to protons and neutrons The framework allows interference between certain operators Following the convention from N. Anand et al, Phys. Rev. C89, (2014). August 2-5, Mini-Workshop@SJTU 2018/8/4 19

20 Relativistic EFT Operators Four dimension-4 effective interactions corresponding to the possible relativistic vector/axial-vector interactions (left) Dim-4 Dim-5 Dimension-5 operators coupling the WIMP magnetic moment or electric dipole moment with the nucleon's vector current (first two in right) Dimension-6 operator coupling WIMP and nucleon magnetic moments (last in right) Dim-6 August 2-5, 2018/8/4 20

21 Relativistic EFT Operators Dramatically different spectra q and v dependence Isospin scalar vs isospin vector [1/kg/day/keV] dr/de R isoscalar L int 7 L int 13 L int 15 L int m C =40GeV isoscalar isoscalar isoscalar isovector isovector isovector isovector L int isoscalar isovector L int isoscalar isovector 17 L int isoscalar isovector m C =400GeV m C =40GeV m C =400GeV August 2-5, Mini-Workshop@SJTU E [kev] 2018/8/4 21 R

22 Constraints on EFT Couplings 54-ton-day data, signal window selection same as SI To be further optimized for various EFT in the future Constraints strongly depending on the operator/isospin Dimensionless Coupling L int isoscalar 7 isoscalar L int 13 L int 15 L int isoscalar isoscalar isovector isovector isovector isovector Dimensionless Coupling L int isoscalar L int isoscalar 17 L int isoscalar isovector isovector isovector Dim-4 2 WIMP mass (GeV/c ) WIMP mass (GeV/c ) August 2-5, Mini-Workshop@SJTU 2018/8/ Dim-5, Dim

23 Constraints on Spin-Dependent Interaction O 4 SD EFT operator: Full basis shell-model GCN5082 Largely suppressed for proton-only coupling in Xe nucleus ) 2 SD WIMP-neutron cross section (cm neutron-only 2 PandaX-II full SM PandaX-II chiral EFT LUX XENON0 3 WIMP mass (GeV/c ) WIMP mass (GeV/c ) August 2-5, Mini-Workshop@SJTU 2018/8/4 23 ) 2 SD WIMP-proton cross section (cm proton-only PandaX-II full SM PandaX-II chiral EFT LUX XENON0 2 3 PICO60 IceCube(n + n - SuperK(t + t ) CMS ATLAS - ) 4 2 5

24 Outline Dark Matter direct detection PandaX program in China PandaX-II recent results PandaX-4T plan Summary August 2-5, 2018/8/4 24

25 PandaX update plan A multi-ton (~4 ton) Dark Matter search experiment is proposed PandaX-I (120kg) PandaX-II (580kg) PandaX-4T (4-ton) August 2-5, Mini-Workshop@SJTU 2018/8/4 25

26 New Experiment Hall at CJPL-II Hall: 14m(H)x14m(W)x65m(L) Water Shielding 5000-ton pure water U/Th < -14 g/g Water Pool PandaX Experiment Hall August 2-5, 2018/8/4 26

27 PandaX-4T: Large scale TPC Characteristics: Sensitive region: ~4-ton Xenon Drift region: Ф~1.2m, H~1.2m Challenges: 1.2m-scale large and uniform electric field High signal efficiency and low background Large amount of Xe handling August 2-5, 1-inch veto PMTs Top 3-inch PMTs Teflon supporter Electrodes Shaping rings Bottom 3-inch PMTs 2018/8/4 27

28 PandaX-4T R&D Krypton measurement Inner vessel TPC prototype PMT test Cooling bus DAQ board August 2-5, 2018/8/4 28

29 PandaX-4T Background Simulation Simulate the ER and NR events Detector materials Radioactivity in xenon: 85 Kr, 222 Rn, 136 Xe Neutrino Background in signal region Total ER background: 0.05 mdru Total NR background: 1 event / ton / year arxiv: August 2-5, Mini-Workshop@SJTU 2018/8/4 29

30 PandaX-4T Expected Sensitivity With two-year exposure, x improvement on sensitivity could be achieved. SI DM-nucleon sensitivity: -47 cm 2 SD DM-neutron: -42 cm 2 SI SD neutron only SD proton only August 2-5, Mini-Workshop@SJTU 2018/8/4 30

31 Summary PandaX-II has reached the world frontier of dark matter direct detection Continues data-taking smoothly Recently, light mediator and EFT results are obtained More results are expected The future PandaX-4T experiment is under R&D Expected sensitivity to SI interaction could reach -47 cm 2 Detector assembly and commissioning is scheduled in August 2-5, Mini-Workshop@SJTU 2018/8/4 31

32 Thank you! August 2-5, 2018/8/4 32

33 backups August 2-5, 2018/8/4 33

34 Backup-effect of drift field Field dependence of scintillation and ionization yield in LXe for 122 kev electron recoils (Ers), 56.5 kev r nuclear recoils (NRs) and 5.5 MeV alphas, relativeto the yield with no drift field (Aprile et al., 2006). Energy resolution and collected charge for 570 kev gamma rays in LXe as a function of electric field (Aprile, Mukherjee, and Suzuki, 1991a). Electron drift velocity in gaseous and liquid xenon and argon, as a function of reduced electric field (Pack et al.,, 1962; Miller et al.,, 1968; Yoshino et al.,, 1976). August 2-5, Mini-Workshop@SJTU 2018/8/4 34

35 Background level in PandaX-II August 2-5, 2018/8/4 35

36 PandaX-III prototype Looking for 136 Xe 0nbb decay Lepton number violation 200-kg High pressure Xe detector August 2-5, 2018/8/4 36