Pandax-III: Astrophysics

PandaX Dark Matter and Neutrinoless Double Beta Decay Programs

HAN, Ke (韩柯) Shanghai Jiao Tong University July 18, 2018 On Behalf of the PandaX Collaboration

Ke Han for PandaX (SJTU) ISoNF, 07/18 1 PandaX: Particle and Astrophysical Xenon TPC

Dark matter WIMP searches

PandaX-I: 120kg LXe PandaX-II: 500kg LXe PandaX-xT LXe (2009 – 2014) (2014 – 2018) (Future)

Exploring the invisible Universe from deep underground 0νββ searches • Physics beyond the Standard Model. • Interconnects particle physics, nuclear physics, cosmology, and PandaX-III: astrophysics. 200kg - 1 ton HPXe (Future)

Ke Han for PandaX (SJTU) ISoNF, 07/18 2 Dark Matter

• Existence of dark matter is firmly established • Particle nature of dark matter? • WIMP?

Ke Han for PandaX (SJTU) ISoNF, 07/18 3

WIMP searches

Slatyer Tracy Tracy

Direct detection: DM: velocity ~1/1500 c, mass ~100 GeV, KE ~ 20 keV Nuclear recoil (NR): recoiling energy ~10 keV

Ke Han for PandaX (SJTU) ISoNF, 07/18 4 Dual phrase Xe TPC for dark matter

Anode grid

Eextra

Gate grid

Edrift

Cathode

Ke Han for PandaX (SJTU) ISoNF, 07/18 5 PandaX WIMP direct detection

• PandaX-I: 2009-2014 • PandaX-II: 2014-2018 • 60 cm x 60 cm dual-phase xenon TPC • 580 kg LXe in sensitive volume • Dual-phase xenon detectors: • Large monolithic target Phase I: 120 kg • 3D reconstruction and fiducialization 2009-2014 • Good ER/NR rejection • Calorimeter capable of seeing a couple of photons/electrons

Phase II: 580 kg Ke Han for PandaX (SJTU) ISoNF, 07/18 2014-2018 6 PandaX-II Run Status

• Run9 =79.6 days, exposure: 26.2 ton-day • Run10 = 77.1 days, exposure: 27.9 ton-day

Mar. 9 – June 30, Nov. 2016 – Mar. Jul. 2017-Now, a few low background 2017, 2nd distillation months 220Rn/AmBe with 10-fold campaign and runs, followed by reduction of Kr recommissioning DM data taking, 3x (Run9, 79.6 days) stat of Run10

2015 2016 2017 2018

Nov. 22 – Dec. 14, Jul – Oct, ER Apr.22 – July15, Physics commission calibration & dark matter data (Run8, 19.1 days, tritium removal taking (Run10, stopped due to high 77.1 days) Krypton background)

Ke Han for PandaX (SJTU) ISoNF, 07/18 7 Highlights of PandaX-II Results

• 33 ton-day: spin independent search, PRL 117, 121303 (2016)

• 33 ton-day: spin dependent search, PRL 118, 071301 (2017) • 27 ton-day: inelastic scattering search, PRD 96, 102007 (2017) • 27 ton-day: Axion and ALP search, PRL 119, 181806 (2017) • 54 ton-day: spin independent search, PRL 119, 181302 (2017) • 54 ton-day: light mediator search, PRL 121, 021304 (2018) • 54 ton-day: general EFT and spin-dependent search, arXiv:1807.01936

Ke Han for PandaX (SJTU) ISoNF, 07/18 8 WIMP-nucleon SI result update

PRL 119, 181302 (2017)

Linear in mass

2  Improved from PandaX-II 2016 limit about 2.5 time for >30GeV/c -47 2 2  Lowest exclusion at 8.6×10 cm at 40GeV/c 2  Most stringent limit for WIMP-nucleon cross section for mass >100GeV/c when published

Ke Han for PandaX (SJTU) ISoNF, 07/18 9 DM direct direction next step: PandaX-xT

• Larger TPC with more detector mass • Ultra-pure water shielding • Online xenon purification • Dual-range PMT readout • For DM and 0νββ

• Intermediate stage: • PandaX-4T (4-ton target) with SI sensitivity ~10-47 cm2

Ke Han for PandaX (SJTU) ISoNF, 07/18 12 PandaX-4T Large Scale TPC

• Drift region: F ~1.2m，H ~1.2m • Xenon in sensitive region～4 ton, drift field 400 V/cm

• Design goal: • High signal collection efficiency 2 ▪ Top PMT% array, 3” • Uniform E field in a large volume ▪ • Veto facility ▪ Top Cu plate ▪ ▪ Teflon supporter Electrodes and shaping rings S Bottom Cu plate

Bottom PMT2 array % ! Veto System 3” ! 2 Ke Han for PandaX▪ (SJTU) ISoNF, 07/18 13

2 1

2 8 9

S 2

) s ),. m ! 业s ～ s ) m G: A ？～ C r ？ m ～ —？ s — C( r m C( C C( ～ s × r r 两 m C( C m C( s ± C( m s C C( m s C( — Current Status and Schedule

• R&D work-in-progress • 2019-2020: assembly and commissioning

Cooling bus

Inner vessel Krypton measurement

TPC prototype

Ke Han for PandaX (SJTU) PMT test ISoNF, 07/18 DAQ board 14 PandaX-4T Sensitivity study

• Simulated ER and NR events • Detector materials • Radioactivity in xenon: 85Kr, 222Rn, 136Xe • Neutrino • Background in signal region • Total ER background: 0.05 mDRU • Total NR background: 1 event / ton / year • With two-year exposure, SI DM-nucleon sensitivity: 10-47cm2 • About x10 improvement w.r.t. PandaX-II

arXiv:1806.02229 Ke Han for PandaX (SJTU) ISoNF, 07/18 15 July 5, 2012 0:12 WSPC/ INSTRUCTION FILE bb0-hep

July 5, 2012 0:12 WSPC/ INSTRUCTION FILE bb0-hep 14

cases in which cancellations can happen are the following ones in which CP is conser ved:

2i α 12 2i α 13 e 14= − 1and e =+1. The value of m1 for which cancellations suppress |mββ | is slightly decreased by the Daya Bay measurement of ϑ13,because the cases in which c2ancellations can happen are the following ones in which CP is larger valueof sin ϑ13m3 adds to the contribution of m1. Hence, a smaller value conser ved: of m1 is required to cancel the sum of the contributions of m1 and m3 with the 2i α 12 2i α 13 opeposite= c−on1atrnibduetion o=+f m12.. The value of m1 for which cancellations suppress 2i α 12 2i α 13 e = −|m1aββn|diseslightly= d−e1cr.eaTshede bvyaluthe Doaf yma B1 ayfomr ewashuicrehmecnatnocef llaϑ13tio,bnescasuuspeptrheess 2 |mββ |laisrgseligr vahlutlyeoinf scinreaϑs13edmb3yadtdhsetoDtahyeacoBnatyribmuteioasnuorfem1e.nHt eonfceϑ,13a ,bsmaellecaruvsaelutehe of m is requir2ed to cancel the sum of the contributions of m and m with the larger valu1e of sin ϑ13m3 adds to the contribution of m2. He1nce, a la3rger value opposite contribution of m2. of m1 is required to cancel the contribution of m1 with the opposite sum of 2i α 12 2i α 13 e = − 1and e = − 1. The value of m1 for which cancellations suppress contributions of m2 and m3. Neutrinoless double beta decay |mββ | is slightly increased by the Daya Bay measurement of ϑ13,because the e 2 Figurela2rgsehrovwaslutehoaftsintheϑ13twmo3eafdfedcststoletahde ctonatribsliguthiotnwoidf men2in. Hgeonfcet,haelacarngecrellavalutioen of m is required to cancel the contribution of m with the opposite sum of band after the1 Daya Bay measurement of ϑ13. 1 contributions of m2 and m3. • Explores the Majorana nature of neutrinos e Majorana Neutrino 4.2. InvFeigr tuerde 2hisheorwarscthhyat ofthethetwoneeffuecttrsilenaodmtoasa sligesht widening of the cancellation • Tests lepton number conservation band after the Daya Bay measurement of ϑ13. In this case, for the neutrino masses we have • ΔL = +2 2 4.2. Inver2ted hierarchy of2 the neutr i no m2asses ∆ ms 2 • 0νββ is not just a neutrino experiment!m3 ∆ ma ,m1 ∆ ma ,m2 ∆ ma 1+ 2 ∆ ma. (60) In this case, for the neutrino masses we have 2∆ ma • Connects to broad neutrino oscillationIn physicsthe express iopicturen of |m |, the contribution of the term m s2in2 ϑ can be safely 2 ββ 2 2 ∆ m3 s 13 2 m3 ∆ ma ,m1 ∆ ma ,m2 ∆ ma 1+2 2 ∆ ma. (60) neglected. Neglecting also the small contribution of sin ϑ213∆,fmraom Eq. (48) we ﬁnd 2 Example: In the expression of |mββ |, the co2ntribution2 of the te2rm m3 sin ϑ13 can be safely |mββ | ∆ ma 1 − sin 2ϑ12 sin 2α12 . (61) neglected. Neglecting also the small contribution of sin ϑ13,from Eq. (48) we ﬁnd The phase α12 is the only unknown parameter in the expression for the effective 136 136 − 2 2 2 푋푒 → 퐵푎 + 2푒 + 2휈ഥ푒 Majorana mass in the cas|emoβfβ |a inve∆rtmead m1 −assinhie2rϑa12rcshiny. α12 . (61)

FroThmeEpqh.a(se61α)12weisﬁtnhde otnhlye fuonlloknwoinwng rpaanragmeeftoerr |inmβtβhe|: expression for the effective Majorana mass in the case of a inverted mass hierarchy. 2 2 cos2ϑ12 ∆ m ≤ |mββ | ≤ ∆ m . (62) From Eq. (61) we ﬁnd the followaing range for |mββ |: a

The upper and lower bounds of this2 inequality corr2espond to the caseof cos2ϑ12 ∆ ma ≤ |mββ | ≤ ∆ ma. (62) CP-invariance in the lepton sector. In fact, CP invariance implies that (see The upper and lower bounds of this inequality correspond to the caseof Refs.50,33,59) CP-invariance in the lepton sector. In fact, CP invariance implies that (see Refs.50,33,59) 2i α 12 ∗ e = η2 η1 , (63) e2i α 12 = η η∗ , (63) where ηk = ± i is the CP parity of the Ma2jor1ana neutrino νk .If η2 = η1,we

have αwh12er=0e ηk, π= (±thieisupthpeerCPboupnardityinotfhteheinMeqaujoarlitanya (n6e2u)t)r.inIof νηk2.I=f η−2η=1 weη1,whaeve α12 = ha±vπe/ 2α12(th=0e lo,wπe(rthbeouunpdpeinr btohuendineinquthaelitiny e(q6u2a)lit).y (62)). If η2 = − η1 we have α12 = ± π/ 2 (the lower bound in the inequality (62)). e We are very grateful to Michele Frigerio for pointing out a mist ake in the cancellation band presenteedWein atrhee vﬁrersyt garraXteifvulvetorsMionichoeflethiFrsigpaerpioerfoarndpoiinntiintgs puoutblaishemidst avkeersiinonth(eMcoad.ncePllhatysio.nLbeatnt.dA Ke Han for PandaX (SJTU) ISoNF, 07/1827 (2012)pres1230015)ented in t.he ﬁrst arXiv version of this paper and in its pu16blished version (Mod. Phys. Lett. A 27 (2012) 1230015). Neutrinoless double beta decay

• Measure energies of emitted e- (universal approach) • Electron tracks are a huge plus (unique feature of certain experiments) • Daughter nuclei identification (ultimate

From Physics World dream?)

2νββ

0νββ

T-REX: arXiv:1512.07926

Sum of two electrons energy Simulated track of 0νββ in high pressure Xe

Ke Han for PandaX (SJTU) ISoNF, 07/18 17 PandaX-III: high pressure gas TPC for 0νββ of 136Xe

• TPC: 200 kg scale, symmetric, double-ended charge readout, with 10 bar of 136Xe • Main features: good energy resolution and background suppression with tracking arXiv:1610.08883

Ke Han for PandaX (SJTU) ISoNF, 07/18 18 PandaX-III first TPC

High Pressure High Voltage Feedthrough • ~4m3 inner volume at 10 bar Vessel • Charge-only readout with

MicromegasCharge Readout Plane Microbulk Micromegas • Strip readout; 3 mm pitch e • ~10000 readout channels Mixture of enriched e 136Xe and 1% TMA e E e e Drift electrons

E Field E Field

Field Cage Cathode

Ke Han for PandaX (SJTU) ISoNF, 07/18 19 Scalable Radio-pure Readout Module (SR2M)

• SR2M: Mosaic layout to cover readout planes • Solderless system • Strip and mesh signal readout • Dead-zone-free arrangement • Designed by Zaragoza and SJTU

×41

Ke Han for PandaX (SJTU) ISoNF, 07/18 20 Xe +TMA (trimethylamine) mixture

Gonzalez-Diaz, et al. NIMA 804 8 (2015) • Better energy resolution Cebrián, S., et al. JINST • Extrapolated from 511keV 8 (2013): P01012. and 1.2MeV peaks: 3% FWHM (@Q 0νββ) Pure Xe • Better tracks Pure Xe • TMA suppress electron diffusion Xe + 1%TMA

• Better operation 22.1 keV • TMA as a quencher gas

With TMA W/o TMA

T-REX: arXiv:1512.07926 Ke Han for PandaX (SJTU) ISoNF, 07/18 21 Electronics

• Front-end electronics close to TPC: reads and digitizes strip and mesh signals (arXiv:1806.09257) • Based on AGET ASIC chips from CEA-Saclay • Back-end above water shielding: triggering and data transmission to DAQ (arXiv:1806.07618)

FEC

Ke Han for PandaX (SJTU) Backend ISoNF, 07/18 22 Background budget

Two independent Geant-4 based MC packages: RESTG4 and BambooMC • Treat PandaX-III as a simple calorimeter • Then add detector response • Calculate signal efficiency and background rejection • ×35 background reduction from topological analysis • Track reconstruction and blob identification at both ends • Convolutional neural network

232Th Raw spectrum

Ke Han for PandaX (SJTU) ISoNF, 07/18 23 Cut-based track classification

Define key parameters (such as energy deposition in a certain blob) and refine cuts

MC truth W/ diffusion Signal pulses

XZ projection Grouped Connected dE/dx along

the track Normalized Energy Normalized

J. Galan, Neutrino 2018 Steps

Ke Han for PandaX (SJTU) ISoNF, 07/18 24 Convolutional Neural network (CNN) for track classification

• XZ, YZ 2D snapshots of an event as input of R and G channels of an image and then rely on CNN to spill out an index of signal/background • Prepare image collections for CNN training, validation, and classification. • No track reconstruction needed.

47.5%

0.6%

H. Qiao, et al arXiv:1802.03489 Ke Han for PandaX (SJTU) ISoNF, 07/18 25 Sensitivity projection

• First 200-kg module: • Microbulk Micromegas for charge readout • 3% FWHM, 1 x 10-4 c/keV/kg/y in the ROI • Ton-scale: • Four more modules with upgraded charge readout and better low-background material screening. • 1% FWHM, 1 x 10-5 c/keV/kg/y in the ROI arXiv:1610.08883

Ke Han for PandaX (SJTU) ISoNF, 07/18 26 Future energy resolution improvement

• TopMetal Direct Charge Sensor – Direct pixel readout without gas amplification – Active development at CCNU and Berkeley

• Alternative Micromegas technologies (Saclay) – Microbulk technology with segmented mesh for true X and Y strips – Bulk technology with better uniformity and less dead area

Ke Han for PandaX (SJTU) ISoNF, 07/18 27 Prototype TPC at Shanghai

• To see MeV electron tracks and demonstrate required energy resolution with a large-scale high pressure TPC • Field cage: 66 cm diameter, 78 cm drift length, single- ended • 600 L of inner volum16 kg of xenon at 10 bar

• 7 Microbulk Micromegas modules Micromegas To electronics Top flat flange module

Charge readout plane

Electric field

shaping cage Electron Electron drift direction

Cathode

Ports for high voltage, pumping, gas filling, SS pressure etc vessel Ke Han for PandaX (SJTU) ISoNF, 07/18 28 Some example tracks

Ke Han for PandaX (SJTU) ISoNF, 07/18 29 Data with 1 Micromegas

Energy spectrum detected of 241Am at 1 bar Ar:iso • Excellent gain of 7000 with 1 bar Ar:iso • 9.3% FWHM at 26.3keV • 11.2% at 20.6keV • Improvement of run quality • 11.9% at 17.8keV • 17.1% at 16.8keV (multiple lines) with 5 bar Xe:TMA is on- • 12.5% at 13.9keV going • Current FWHM: 14.1% at 59.5 keV

241Am at 5 bar Xe:TMA

arXiv:1804.02863 Ke Han for PandaX (SJTU) ISoNF, 07/18 30 CJPL – Deepest underground lab in the world

Science Mag.

From Yue Qian CJPL-I

CDEX PandaX

Ke Han for PandaX (SJTU) ISoNF, 07/18 31 PandaX hall at CJPL-II

• PandaX projects • CDEX WIMP/ 0νββ search • JUNA (accelerator) • Geo/Solar neutrino detector • Other 0νββ activities • ……

PandaX at Hall B2 • ~ 900 m2 • Extra excavation for the water shielding pool (finished) • Shared facility of DM and 0νββ searches

Ke Han for PandaX (SJTU) ISoNF, 07/18 32 Recent activities at PandaX hall 2016

• Beneficial occupation started in 2017 for PandaX-II xenon distillation, etc. • Infrastructure work in progress.

Ke Han for PandaX (SJTU) ISoNF, 07/18 33 Conclusions and outlook

• PandaX-II with 580kg xenon has • PandaX-III aims to build multiple reached the world frontier of dark 200-kg scale high pressure xenon matter direct detection. TPC for NLDBD search at CJPL. • PandaX-4T reaches an expected • A 20-kg scale prototype TPC is under sensitivity to SI interaction of 10-47 commissioning. cm2 with 2 year live time. • First 200 kg module: 2020 • Assembly and commissioning: 2019-2020

Ke Han for PandaX (SJTU) ISoNF, 07/18 34 PandaX Collaboration

• Particle and Astrophysical Xenon Experiments • Formed in 2009, ~50 people Shanghai Jiao Tong University Peking University Shandong University Nankai University Shanghai Institute of Applied Physics Yalong Hydropower Company University of Science & Technology of China China Institute of Atomic Energy Sun Yat-Sen University University of Maryland Lawrence Berkeley National Lab CEA Saclay University of Zaragoza Suranaree University of Technology

Ke Han for PandaX (SJTU) ISoNF, 07/18 35 Ke Han for PandaX (SJTU) ISoNF, 07/18 36 Ke Han for PandaX (SJTU) ISoNF, 07/18 37 Ke Han for PandaX (SJTU) ISoNF, 07/18 38 PandaX vs. NEXT

PandaX-III first TPC NEXT-100

200 kg Xe(enriched) + 1% TMA Detector medium 100 kg pure Xe (enriched)

Primary + electroluminescence ------Light light readout by PMTs

Micromegas Charge/Tracking SiPM

3% Projected energy resolution 0.7%

3 mm Tracking pitch size 1 cm

X,Y Fiducialization X,Y,Z

Since 2015 Since ~2008

Ke Han for PandaX (SJTU) ISoNF, 07/18 39 Summary and Outlook

• PandaX experiment with 580kg Xenon has reached the world frontier of dark matter direct detection. • PandaX-II continues data-taking smoothly. • Recently, light mediator and EFT results are obtained • More results are expected.

• The future PandaX-4T experiment R&D is work-in-progress. • Expected sensitivity to SI interaction could reach 10-47 cm2 • Detector assembly and commissioning is scheduled in 2019-2020

• PandaX-III 0nbb search detector is in preparation.

• Thank you!

Ke Han for PandaX (SJTU) ISoNF, 07/18 40 Ke Han for PandaX (SJTU) ISoNF, 07/18 41 Ke Han for PandaX (SJTU) ISoNF, 07/18 42 Constraints on Spin-Dependent Interaction

• O4 SD EFT operator -35 )

2 10 m

c -36 (

• Full basis shell-model GCN5082 10

n o

i -37 t

c 10

e s

• For proton-only coupling in Xe nucleus -38 s

s 10 o

r -39 c • 10

O4 SD EFT interaction largely suppressed n o

r -40 t

u 10

e n - -41 PandaX-II full SM

P 10

PandaX-II chiral EFT M

I -42

10 LUX W

-43 XENON100 D • S 10 neutron-only “Standard” SD calculation: 10-44 10 102 103 104 105 • chiral EFT WIMP mass (GeV/c2) • O4 + O6 + two nucleon pion-exchange

-30 )

2 10

PandaX-II full SM PICO60 m

c + -

( PandaX-II chiral EFT IceCube(n n ) -32 -

n 10 LUX SuperK(t+t )

o i

t XENON100 CMS c

e -34

s ATLAS

s o

r -36 c

o t

o -38

r 10

p -

P -40 M

I 10 W -42 D 10 S proton-only 10-44 10 102 103 104 105 neutron-only proton-only WIMP mass (GeV/c2) Ke Han for PandaX (SJTU) ISoNF, 07/18 43