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 Micromegas Charge Readout PlaneReadout Charge Micromegas 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.