Status of the XENON Dark Matter Project Recent Results from XENON100 and Prospects for Detection with XENON1T

Guillaume Plante

Columbia University

on behalf of the XENON Collaboration

DBD 2014 - Waikoloa, Hawaii - October 5-7, 2014 XENON Program

XENON10 XENON100 XENON1T/XENONnT

2005-2007 2008-2015 2012-2017 / ∼2017-2022

25kg 161kg 3300kg/7000kg

Achieved (2007) Achieved (2011) Projected (2017) / Projected (2022) −44 2 −45 2 −47 2 −48 2 σSI =8.8 × 10 cm σSI =7.0 × 10 cm σSI ∼ 2 × 10 cm / σSI ∼ 3 × 10 cm Achieved (2012) −45 2 σSI =2.0 × 10 cm

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 2 / 35 XENON Collaboration

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 3 / 35 XENON Collaboration

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 3 / 35 Why Xenon?

• Large mass number A (∼131), ex- pect high rate for SI interactions (σ ∼ A2) if energy threshold for nu- clear recoils is low 129 131 −3 A • ∼50% odd isotopes ( Xe, Xe) 10 Si ( = 28) for SD interactions Ar (A = 40) Ge (A = 73) • No long-lived radioisotopes (with the A 136 Xe ( = 131) exception of Xe, T1/2 = 2.1 × 21 10 yr), Kr can be reduced to ppt −4 10 levels • High stopping power (Z = 54, ρ = 3 g cm−3), active volume is self shielding Total Rate [evt/kg/day] −5 10 σ = 1 × 10−44 cm2 • Efficient scintillator (∼80% light χN yield of NaI), fast response 0 10 20 30 40 50 • Scalable to large target masses Eth - Nuclear Recoil Energy [keV] • Nuclear recoil discrimination with si- multaneous measurement of scintilla- tion and ionization

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 4 / 35 Dual Phase TPC Principle

• Bottom PMT array below cathode, fully immersed in LXe to efficiently detect scintillation signal (S1). • Top PMTs in GXe to detect the proportional signal (S2). • Distribution of the S2 signal on top PMTs gives xy coordi- nates while drift time measurement provides z coordinate of the event (XENON100: ∆r < 3mm, ∆z < 300 µm) • Ratio of ionization and scintillation (S2/S1) allows discrim- ination between electron and nuclear recoils.

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 5 / 35 XENON100: Detector

• Goal was to build a detector with a ×10 increase in fiducial mass and a ×100 reduction in background compared to XENON10 • All detector materials and components were screened in a ded- icated low-background counting facility • 161 kg LXe: 62 kg target surrounded by a 99 kg active veto • 15 cm radius, 30 cm drift length active volume • 242 low-activity Hamamatsu R8520-06-Al 1” square PMTs • 98 tubes on top, 80 on bottom, 64 in the active veto • Cathode at -16 kV, drift field of 0.533 kV/cm. Anode at 4.4 kV, proportional scintillation region with field ∼12 kV/cm

• Installed in a 20 cm H2O, 20 cm Pb, 20 cm polyethylene, 5 cm Cu passive shield to suppress external backgrounds

• Aprile et al., Astropart. Phys. 35, 573, 2012

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 6 / 35 XENON100: LNGS

Lab ❤❤❤ ✑ ❤❤❤ ✑ ❤❤❤ ✑ ❤❤❤

Outside Buildings

Tunnel

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 7 / 35 XENON100: Typical Low Energy Event

186 187 188 185 189 184 8 9 190 7 10 183 6 11 191 36 37 38 5 12 182 35 39 192 60 4 34 59 61 40 13 58 62 181 193 3 33 78 79 41 14 57 77 80 63 180 91 194 2 32 56 76 90 92 81 64 42 15 0.40 179 1 31 55 75 89 97 98 93 82 65 43 16 195 0.35 TPC 0.15 S1: 14.1 pe S2: 926.1 pe 30 54 74 88 96 94 83 66 44 17 0.30 0.3 210 95 196 73 87 84 67 0.10 29 53 45 18 0.25 209 86 85 197 0.2 72 68 28 52 46 19 71 70 69 0.20 208 198 0.05 27 51 47 20 0.1 50 49 48 0.15 207 26 21 199 25 22 206 24 23 200 Amplitude [V] 0.10 0.00 0.0 205 201 0.05 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 170 171 172 173 174 175 176 177 204 203 202 0.00

218 219 220 Veto 217 221 216 222 1.5 215 223 99 100 101 102 214 224 1.0 103 104 105 106 107 108 109 213 225 110 111 112 113 114 115 116 117 118

212 119 120 121 122 123 124 125 126 127 128 226

Amplitude [V] 0.5 129 130 131 132 133 134 135 136 137 138 211 227 139 140 141 142 143 144 145 146 147 148

0.0 242 149 150 151 152 153 154 155 156 157 158 228

0 20 40 60 80 100 120 140 160 180 159 160 161 162 163 164 165 166 167 241 229 Drift Time [µs] 168 169 170 171 172 173 174 240 230 175 176 177 178 239 231 238 232 237 233 236 235 234

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 8 / 35 XENON100: ER/NR Discrimination

60Co,232Th

AmBe

• Background in the energy region of interest is due to low energy Compton scatters from high energy gamma rays or β decays. • Electronic recoil band calibration performed with high energy gammas from 60Co and 232Th. Nuclear recoil band calibration performed with AmBe neutron source. • Since WIMPs are expected to elastically scatter off of nuclei understanding the behavior of single elastic nuclear recoils in Xe is essential.

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7, 2014 9 / 35 XENON100: Nuclear Recoil Energy Scale

• Nuclear recoil equivalent energy Enr is obtained from the S1 signal 0.35 Arneodo 2000 Bernabei 2001 S1 1 Ser Enr = 0.30 Akimov 2002 Ly,er Leff (Enr) Snr Aprile 2005 0.25 Chepel 2006 • Ly,er = 2.28 ± 0.04 pe/keVee, light Aprile 2009 Manzur 2010 yield of ER from 122 keV γ rays 0.20 Plante 2011 LeffLeff • Ser = 0.58, Snr = 0.95, scintillation 0.15 light quenching due to drift field 0.10 • Relative scintillation efficiency Leff 0.05 Ly,nr (Enr) Leff (Enr)= Ly,er (Eee = 122 keV) 0.00 1 2 3 4 5 6 7 8910 20 30 40 100

π Energy [keVnr] ϕ = 2 2 3 H(d, n) He EJ301 d n • Record fixed-angle elastic scatters of monoenergetic neutrons tagged by organic liquid scintillators with LXe θ n/γ discrimination θ • Measurement performed at Columbia University, low- EJ301 est energy measured 3 keV

≈ mnMXe − et al. Er 2En 2 (1 cos θ) • Plante , Phys. Rev. C 84, 045805 (2011) mn+MXe
GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 10/35 XENON100: Latest WIMP Search Data Released: 225 Days

Radius [cm] S1 [PE] 2 4 6 8 10 12 14 15.3 5 10 15 20 25 30 0 0.4 -5 0.2 -10 0.0 -15

z [cm] -0.2 -20 -0.4 /S1)-ER mean b -25

(S2 -0.6 10 -30

0 50 100 150 200 250 log -0.8 Radius2 [cm2] -1.0

-1.2 5 10 15 20 25 30 35 40 45 50 Energy [keVnr] • 2 candidate events observed within 34 kg fiducial volume • Probability that the background fluctuates to 2 events when expecting 1.0 ± 0.2 is 26.4% • Profile Likelihood analysis cannot reject background-only hypothesis • No evidence for a dark matter signal

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 11/35 XENON100: Spin-Independent Results

−45 2 2 • Exclusion limits derived with profile likelihood method, σSI < 2.0 × 10 cm @ 50 GeV/c • Up until the latest LUX results (10/2013), was the strongest limit over a large WIMP mass range

• Aprile et al., Phys. Rev. Lett. 109, 181301 (2012)

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 12/35 XENON100: Response to Nuclear Recoils

104 • Calculate the NR response Data

241 Counts Bezrukov Q • Start with AmBe neutron emis- y Best Fit Qy sion spectrum 103 • Source strength measured (PTB) as 160 ± 4 n/s • Propagate neutrons through a de- 102 tailed Geant4 detector geometry • Convert energy deposits into observ- able S1 and S2 signals using Leff 0 1000 2000 3000 4000 5000 6000 7000 8000 cS2 [PE] and Qy, including thresholds, reso- lutions, and acceptances from data 11 10 Aprile 2006, 0.2 kV/cm Sorensen 2009 /keVnr] - • First step: use the measured Leff from 9 Manzur 2010 [e y 8 Horn 2011 scattering experiments and derive the Q Bezrukov Qy 7 optimum Qy by reproducing the mea- XENON100 (this work) sured S2 spectrum 6 5 • Excellent agreement between MC and 4 measured S2 spectrum 3 2 • E. Aprile et al., Phys. Rev. D 88, 012006 (2013)

2 10 102 Energy [keV ] nr

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 13/35 XENON100: Response to Nuclear Recoils

× 3 3.0 10 • Second step: use the optimum Qy ob- Data tained to calculate the MC S1 spectrum Aprile L Counts 2.5 eff Best Fit L and derive a new Leff eff 2.0 • Excellent agreement between measured S1 spectrum and MC down to 2 pe 1.5

• Indirect Leff obtained consistent with di- 1.0 rect measurements 0.5 • Confirms robustness of the XENON100

L 2 eff parametrization down to 3 keVr 1 10 10 cS1 [PE]

2.6 0.30

Data eff

L Aprile 2009 MC

(cS2/cS1) 2.4 Manzur 2010 10 0.25 Plante 2011

log Horn 2011 2.2 0.20 Aprile 2011 XENON100 (this work) 2.0 0.15 1.8

0.10 1.6 0.040 20 40 60 80 100 120 140 0.02 0.05 0.00 -0.02 -0.04

(MC-Data)/Data 0 20 40 60 80 100 120 140 2 10 102 cS1 [PE] Energy [keV ] nr

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 14/35 XENON100: Axion Searches

• Axions and axion-like particles can couple to electrons via the axio-electric effect 2 2 2/3 gAe 3E β σ = σ (E) 1 − Ae pe 2 β 16παme 3 !

• Analogous to the photoelectric effect with an absorbed axion instead of a photon • Expect electronic recoils from axio-electric interactions Solar axions Galactic axion-like particles Expected Mean Recoil Energy [keV] Expected Mean Recoil Energy [keV] 1 2.5 5 7.5 10 1 5 10 15 20 25 30 35

1 keV/c2 102 102 Events/PE Events/PE 5 keV/c2 2 8 keV/c 10 keV/c2

10 10

20 keV/c2 15 keV/c2 30 keV/c2 1 1 0 5 10 15 20 25 30 0 10 20 30 40 50 60 70 80 90 100 S1 [PE] S1 [PE] 2 Expected signal for mA < 1 keV/c Expected signal assuming ALP constitute −11 −12 and gAe =2 × 10 all of galactic DM and gAe =4 × 10

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 15/35 XENON100: Electronic Recoil Energy Scale

• Obodovskii (1994) Need to know the response of LXe to low energy ER Aprile (2012) NEST (v0.98, 2013) • Two recent measurements of the scintillation yield of 1 ER using the “Compton coincidence technique” 0.8 E − γ Er = Eγ e Eγ 0.6 1 + (1 − cos θ) R me

0.4 Aprile et al., Phys. Rev. D 86, 112004 (2012)

137 Cs 0.2 Compton scatters (this work) 660 Calibration sources (this work) Band used for threshold calculation 650 0 [keV] 0.5 1 2 5 10 20 50 100 200 640

HPGe Energy [keV]

γ LXe E detector 630 PMTs 0.080 5 10 15 20 25 30 35 40 Compton scatters (this work) ] o -1 0.07 θ HPGe = 8.6 Calibration sources (this work) ′ 0.06 ± 1.2 Manalaysay (2010) γ Eer = 8.2 1.0 keV 0.05 Aprile (2006) NEST (v0.98, 2013) 0.04 E = [653,654] keV HPGe 1 θ 0.03 0.02

dN/dE [events keV 0.01 0.8 0 HPGe 0 5 10 15 20 25 30 35 40 detector (450) Recoil Energy [keV] q 0.6

0.4 • At zero field, scintillation yield decreases below 60 keV 0.2 Baudis et al., Phys. Rev. D 87, 115015 (2013) • Field quenching ∼0.75 at low energies 0 0.5 1 2 5 10 20 50 100 200 • XENON100 energy threshold 2.04 ± 0.21 keV Energy [keV]

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 16/35 XENON100: First Axion Search Results

• Uses the same 225 days data as for spin-independent WIMP search • Profile Likelihood analysis cannot reject background-only hypothesis • Ultra-low background and low energy threshold enable XENON100 to set competitive limits • Analysis made possible by recent measurements of scintillation yield and field quenching of ERs

Solar axions Galactic axion-like particles 10-9 10-9 Si(Li) KSVZ Solar ν -10 DFSZ -10 10 XMASS 10 Solar ν CDMS EDELWEISS CoGeNT

Ae -11 Ae -11 EDELWEISS

g 10 g 10

XENON100 KSVZ 10-12 10-12 Red giant XENON100

10-13 10-13 10-5 10-4 10-3 10-2 10-1 1 1 2 3 4 5 6 7 8 910 20 30 2 2 mA [keV/c ] mA [keV/c ]

E. Aprile et al., Phys. Rev. D 90, 062009 (2014)

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 17/35 XENON100: Status

• Upcoming analysis results • Electronic recoil rate stability analysis • Light dark matter (“few electrons” S2-only analysis) • WIMP-nucleus inelastic interactions • 154 days of new DM data in 2013 (blinded) under analysis

• Improvements in detector characterization • Calibrations with AmBe at different drift fields • Measurement of low-energy (<5 keVr) NRs from YBe

• Continuing data acquisition • Online Rn removal tests • Novel calibration methods

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 18/35 XENON1T: (Very Near) Future

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 19/35 XENON1T: (Very Near) Future

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 19/35 From XENON100 to XENON1T: A Few of the Challenges

XENON100 XENON1T LXeMass(kg) 161kg 3300kg − − ER Bkgnd (evts/keV/kg/d) 5 × 10 3 ∼5 × 10 5 Kr Concentration (ppt) (19 ± 4) < 0.5 Rn Concentration ( µBq/kg) ∼65 ∼1 Charge drift (cm) 30 100 Cathode HV (kV) −16 −100 LXePurification SeveralMonths FewMonths Cryogenics ∼1 year run ∼2+ year run Storage/Recovery GXe LXe

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 20/35 XENON1T: Construction Milestones

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 21/35 XENON1T: Construction Milestones

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 22/35 XENON1T: Construction Milestones

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 23/35 XENON1T: Construction Milestones

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 24/35 XENON1T: Water Cherenkov Muon Veto

• Water tank 10m high and 9.6m diameter • Interior lined with 3M specular reflector foil • Water tank construction completed 2013/12 • 84 high QE 8” Hamamatsu R5912 PMTs • µ-induced neutron background < 0.01 evt/yr • Trigger efficiency > 99.5% for neutrons with µ in water tank, ∼78% with µ outside

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 25/35 XENON1T: Cryostat, TPC

• Double-wall vacuum insulated cryostat, con- structed from selected low-activity stainless steel • Outer vessel 2.4m high, 1.6m diameter, inner vessel ∼2m high, 1.1m diameter • 3.3 tons LXe, ∼1m3 TPC, fiducial mass be- tween 1 and 1.5 tons • 248 3” PMTs Hamamatsu R11410-21, 36% average QE, < 1mBq/PMT in U/Th • Background ×100 lower than XENON100 • Custom low-activity high voltage feedthrough

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 26/35 XENON1T: Cryostat, TPC

• Double-wall vacuum insulated cryostat, con- structed from selected low-activity stainless steel • Outer vessel 2.4m high, 1.6m diameter, inner vessel ∼2m high, 1.1m diameter • 3.3 tons LXe, ∼1m3 TPC, fiducial mass be- tween 1 and 1.5 tons • 248 3” PMTs Hamamatsu R11410-21, 36% average QE, < 1mBq/PMT in U/Th • Background ×100 lower than XENON100 • Custom low-activity high voltage feedthrough

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 26/35 XENON1T: Cryogenics

• Design based on experience acquired by operating XENON10, XENON100, and XENON1T Demonstrator • Heat load below 50 W (without circulation) • Redundant 200 W pulse tube refrigerators • One PTR can be serviced while the other is in operation • Backup liquid nitrogen cooling • Circulation at ∼100 slpm through heat ex- changers

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 27/35 XENON1T: Xe Storage

• Double-wall, high-pressure (70 atm), vacuum insulated, LN2 cooled sphere • Designed to store ∼7.6 tons of xenon, in liquid form at −100◦C or in gaseous form at room temperature • Detector can be filled with liquid xenon di- rectly instead of condensing xenon gas • In case of emergency, liquid xenon from the detector can be recovered in a few hours

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 28/35 XENON1T: Purification

• Continuous GXe circulation at ∼100 slpm • Purification using high-flow heated getters • Two parallel circulation pumps and purifica- tion circuits • GXe purity in-situ analytics • Continuous monitoring of impurity concentra- tions (e.g. H2O)

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 29/35 XENON1T: Kr Removal

• Building custom designed cryogenic distilla- tion column for Kr removal • XENON1T Kr/Xe concentration requirement is < 0.5 ppt, aim at < 0.1 ppt with the col- umn • High throughput, 3kg/hr at 104 separation • 3.5 tons in ∼1.8 months (single pass) • Custom gas purity diagnostics (online, 83mKr tracer, and offline, ATTA, RGMS, RGA + cold trap)

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 30/35 XENON1T: Expected Backgrounds

ER background from PMTs, Cryostat ER background after discrimination

Preliminary

• Single scatters, 1 ton fiducial volume, • Full MC simulation of the detector (TPC, [2, 12] keVee, [5, 50] keVr, 99.75% S2/S1 PMTs, cryostat, water shield) with GEANT4 discrimination, 40% NR acceptance to predict ER background Source Background(evts/yr) • Neutrons from (α,n) calculated with ERfrommaterials 0.05 SOURCES-4A 85Kr (0.2 ppt natKr) 0.07 222 • Total ER background rate expected to be Rn (1 µBq/kg) 0.08 −5 Solarneutrinos 0.08 below 5 × 10 evts/keVee/kg/day before 2ν2β 0.02 S2/S1 discrimination NRfrommaterials 0.24 Total 0.54

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 31/35 XENON1T: Sensitivity

• Spin-independent WIMP-nucleon interaction cross section sensitivity of 2 × 10−47 cm2 for WIMPs with a mass of 50 GeV/c2

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 32/35 XENONnT: Upgraded XENON1T Detector

• Rapid deployment possibility: no modifications to infrastructure required, only construction of a larger inner vessel and TPC • Additional ∼200 PMTs and DAQ electronics channels for the upgraded TPC • Target mass of ∼6 tons, sensitivity to spin- independent WIMP-nucleon elastic scattering cross sections of 3 × 10−48 cm2

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 33/35 Conclusion

• XENON100 recent results on axion searches, stay tuned for more results • XENON100 is still taking data, continuing to improve detector characterization • XENON1T is under construction at LNGS, water tank completed, service building completed • Integration and commissionning of primary systems (cryostat, cryogenics, storage, purification) underway, detector installation by mid-2015 • Detector commissionning in 2015, first science run starts in 2015 • XENONnT, possibility of a rapid upgrade path included in the XENON1T design

GuillaumePlante-XENON DBD2014-Waikoloa,Hawaii-October5-7,2014 34/35