The LUX & LZ Experiments and the Search for Cosmic Dark Matter

Do WIMPs Rule? The LUX & LZ Experiments and the SearchPMT Cabling for andCosmic Installation Dark Matter

" !Carlos HernandezDan Faham Akerib Brown University ! LUX Collaboration Meeting SLAC NationalOctober 22, 2011 Accelerator Laboratory Kavli Insitute for Particle Astrophysics & Cosmology Standard cosmology: An inventory of the universe

SDSS-III / BOSS from Perlmutter, Phys. Today (units of critical density)

supernovae Energy density

Baryon acoustic oscillations

Matter density

3 Kelvin cosmic microwave backgroundWMAP WMAP Tytler & Burles WIMP Hypothesis • Early Universe as Particle Factory • Not enough protons and neutrons produced in the Big Bang Convert energy to mass E=mc2 quark WIMP distance

anti-quark anti-WIMP

time

• A new type of particle: WIMPs = weakly interacting massive particles Massive: source of gravity Weakly-interacting: not star forming cross section → annihilation rate cross section → annihilation rate WIMP freezeout

• WIMP pairs produced in equilibrium Production = Annihilation (T≥mχ)

• Annihilation stops when number Production suppressed (T ΓA~ nχ 〈σA v 〉 → annihilation rate slower than ~exp(-m/T) Hubble expansion (“freeze out”) → mean free time > age

• For Ωχ ≈ 1 ◆ M ∼ 10-1000 GeV

◆ σA ∼ electroweak SUSY/LSP? Comoving Number Density Jungman, Greist, Kamionkowski 1996

1 10 100 1000 mχ / T (time ➜) Dark Matter in Galactic Halos

● data

with dark halo

if only stars and gas

Vera Rubin and Kent Ford, 1978 Scattering experiment 1016 WIMPs/year WIMP

density, speed dark matter halo 10-16 light years

detector Cross section: WIMP scatters 1 light year once in a light year of lead Rate ~ few events / year WIMP search - c.1988: converted neutrino detector • Germanium ionization detector at the Oroville Dam, CA searching for double beta decay - progenitor to Majorana

ruled out heavy neutrinos as DM Event rate

from Jungman et al. (D.O. Caldwell et al.) Recoil energy transfer to nucleus WIMP search - c.1988: converted neutrino detector • Germanium ionization detector at the Oroville Dam, CA searching for double beta decay - progenitor to Majorana-40 10 http://dmtools.brown.edu/ Gaitskell,Mandic,Filippini

-41 10

-42 10 ] (normalised to nucleon) 2

-43 10 log cross section (arb. units) Event rate

Cross-section [cm -44 10 070802080001 1 2 3 10 10 10 WIMP Mass [GeV]

from Jungman et al. (D.O. Caldwell et al.) Recoil energy transfer to nucleus Energy deposition

WIMP

10% energy Ionization

Phonons/heat

100% energy slowest cryogenics

Light

1% energy fastest no surface effects An active ﬁeld with many approaches! WIMP Semiconducting CoGent (HPGe) calorimeters: CDMS, Edelweiss DMTPC (gas dir.) 10% energy DRIFT (gas dir.) Ionization Superheated liquids: Picasso, Simple, Coupp, PICO 2-phase nobles: ZEPLIN, XENON, Phonons/heat WARP, LUX/LZ, ArDM, Darkside 100% energy slowest

Light CRESST II Inorganic scintillators: 1% energy DAMA/LIBRA, KIMS fastest low radioactivity Single-phase liquid nobles: background immunity DEAP, MiniCLEAN, XMASS large mass / stable operation shielded low energy threshold Shielding Gamma Rays Water, 2.6 MeV gammas Water

1 m water shielding Liquid Xe, 2.6 MeV gammas Liquid Xenon

1 m liquid Xe The Large Underground Xenon Detector

250 kg active LXe @ 170 K S1, S2 event energy S2 event xy location S1-S2 timing z location S2/S1 recoil type

z y

x The LUX Experiment

Inside the LUX/LZ water tank Sanford Underground Research Facility 4850-foot deep Davis Cavern Homestake Gold Mine Lead, SD

photo credits: Matt Kapust, SURF Sanford Underground Research Facility Former Homestake Gold Mine Backgrounds: neutrons

cosmic ray muons Gammas in Water muons down by 10,000,000x

nuclear neutron moderated by disintegration water shield neutron scatter

photo credit: Matt Kapust, Sanford Lab 1964 Nov 2011

2009

LUX Water Tank - Outside View Internal dangers: radioactive 85Kr • 10-y T1/2 beta decay • Can’t self-shield • Noble gas: non-reactive Chromatography • ~130 ppb in purchased Xe • LUX background “ﬂoor” from 122 PMTs ~ 20 ppt Kr/Xe Xe Kr e- He ν

85Kr→85Rb + e- + ν e-

gamma ray Gas charcoal chromatography Kr removal

Xe Kr He 400 kg Xe at Case: 130 ppb to 4 ppt thermosyphon traps dewar

thermosyphon lines (3) gas panel gas control condenser panel charcoal column

sampling RGA feed & recovery Xe recovery bottles pumps graduate student Detection ofChang krypton Lee at the part-per-trillion level

arXiv:1103.2714v3

C. Hall, UMD: Assay with ppt1.5 sensitivity ppt Kr

open leak valve 50 kg / week processed for LUX

4 days (arb units) partial pressure Xe

45 kg feed (mass) Xe Raw signals in LUX Depth from timing difference

z y

Lateral location from top PMT Array Signal production in liquid Xe

e- e- e- e- E ~ keV S2 + Recombination Xe + Xe2 Ion Xe Ionized molecule Xe Xe

Xe* Xe2* VUV photon, 175nm Xe Excitation Heat S1

Electron Recoils Signal production in liquid Xe

e- e- Xe E ~ keV e- S2 + Recombination Xe + Xe2 Ion Xe Ionized molecule Xe Xe

Xe* Xe2* VUV photon, 175nm Xe Excitation Heat S1

Nuclear Recoils Understanding light and charge

Electron recoils

Electric Field

Nuclear recoils

Puzzling low energy behavior Comprehensive model, only 2 ﬁt parameters (Dahl, PhD thesis, 2009) Robust Monte Carlo framework: NEST (M. Szydagis et al., JINST 6, p10002 (2011)) Background and Signal Distinction in situ LUX calibrations Background

Signal More charge, less light charge, More

Internal tritium source (purified away with τ ~ 7 hours) WIMP signal Signal region: a quiet place where low-energy single- • scatter nuclear recoils away from the walls can emerge from among: • external gamma rays into the ﬁducial volume • wall events (206Pb) • dissolved backgrounds (Rn-progeny, 85Kr, 127Xe) • delayed electrons from previous large S2’s

S1 summed across all channels 0.6 1.5 0.5

0.4 1

0.3 0.5 150 0.2 amplitude (phe/10ns) 100 0 amplitude (phe/10 ns) 0.1 50

0 0 50 0 100 150 200 PMT channel2 number ALPHA POPULATIONS−0.2 0 0.2 0.4 IN XY ALPHA POPULATIONStime (µs) IN R Z time (µs)

83mKr injection movie 550 sec 83mKr injection movie 550 sec

Adam Wade Bradley - Case Western Reserve University 6 AWG Mtg 8/21/13 - TAUP Final Approval Adam Wade Bradley - Case Western Reserve University 7 AWG Mtg 8/21/13 - TAUP Final Approval Event selection

S1 summed across all channels S2 summed across all channels 0.6

0.5 8

0.4 6 0.3 4 0.2

amplitude (phe/10 ns) 0.1 amplitude (phe/10 ns) 2

0 0 −0.2 0 0.2 0.4 179 180 181 182 183 184 time (µs) time (µs) 1.5 S1 S1

0.5 150

amplitude (phe/10ns) 100 0 50

0 50 0 100 150 200 PMT channel number time (µs) Requirements for WIMP search candidate events • S2 trigger (at least 2 trigger ch. ≥ 8 phe within 2 µs) [lower threshold than S1] • 2 phe (2-fold coincidence) ≤ S1 ≤ 30 phe [quiet enough to see this in ‘look back’] • 200 phe (8 e-) ≤ S2 ≤ 3300 phe [require good xy measurement] • total area of other pulses in the event < 100 phe [confusion from previous large S2's] LUX WIMP Search, 85 live-days, 118 kg calibration 1.3 keV 2.6 ee ER Calibration 99.6±0.1% leakage below NR 2.4 1.8 mean, so expect 0.64 +/- 0.16 for 160 events

2.2

2 3.5 4.6 1.8 5.9 7.1 /S1) x,y,z corrected b 1.6 (S2

10 1.4 log

1.2

3 6 9 12 15 18 21 24 27 30 keV 1 nr 0 10 20 30 40 50 S1 x,y,z corrected (phe) 0 gate grid 50

s) 100 µ 150 160 events in ER 200 band / 118 kg fiducial drift time ( 250

300 wall face wall corner 350 cathode grid 0 100 200 300 400 500 600 radius2 (cm2) Extended Likelihood Treatment

Observables: x = (S1, log10(S2/S1), r, z)

Parameter of interest: Ns

Nuisance parameters: NCompt, NXe-127, NRn/Kr-85

Modeled WIMP signal, including resolution and efﬁciencies

8 GeV /c2 WIMP 100 GeV /c2 WIMP 2 TeV /c2 WIMP Spin Independent Cross Section Upper Limit

EdelweissZEPLIN II III

) CDMS II Ge 2

−44 10 XENON100(2011)-100 live days

XENON100(2012)-225 live days

−45 10 LUX (2013)-85 live days WIMP − nucleon cross section (cm LUX +/-1σ expected sensitivity

1 2 3 10 10 2 10 m (GeV/c ) Phys. Rev. Lett. 112, 091303 (2014) WIMP Spin Independent Cross Section Upper Limit

−40

) 10 2

−41 10

−42 10

−43 10

−44 10 WIMP − nucleon cross section (cm

−45 10

1 2 3 10 10 10 m (GeV/c2) WIMP Low Mass WIMPs CDMS II Ge )

2 −40 DAMA/LIBRA Favored 10 CoGeNT Favored x CRESST Favored −41 10 CDMS II Si Favored

−42 10

XENON100(2012) 225 live days −43 10 WIMP − nucleon cross section (cm LUX (2013) -85 live days −44 10 5 6 7 8 9 10 12 m (GeV/c2) WIMP w/newest CDMS result

FIG. 3. Small gray dots are all veto-anticoincident single- scatter events within the ionization-partition fiducial volume that pass the data-quality selection criteria. Large encircled FIG. 4. The 90% confidence upper limit (solid black) based on shapes are the 11 candidate events. Overlapping shaded re- all observed events is shown with 95% C.L. systematic uncer- gions (from light to dark) are the 95% confidence contours ex- tainty band (gray). The pre-unblinding expected sensitivity pected for 5, 7, 10 and 15 GeV/c2 WIMPs, after application in the absence of a signal is shown as 68% (dark green) and of all selection criteria. The three highest-energy events occur 95% (light green) C.L. bands. The disagreement between the on detector T5Z3, which has a shorted ionization guard. The limit and sensitivity at high WIMP mass is due to the events band of events above the expected signal contours corresponds in T5Z3. Closed contours shown are CDMS II Si [3](dotted to bulk electron recoils, including the 1.3 keV activation line blue,90%C.L.),CoGeNT[4](yellow,90%C.L.),CRESST-II at a total phonon energy of 3 keV. High-radius events near [5](dashed pink,95%C.L.),andDAMA/LIBRA[34](dash- the detector sidewalls form the⇠ wide band of events with near- dotted tan, 90% C.L.). 90% C.L. exclusion limits shown are zero ionization energy. For illustrative purposes, an approxi- CDMS II Ge [22](dotted dark red), CDMS II Ge low-threshold mate nuclear-recoil energy scale is provided. [17](dashed-dotted red), CDMSlite [20](solid dark red), LUX [35](solid green), XENON10 S2-only [19, 36](dashed dark green), and EDELWEISS low-threshold [18](dashed orange).

a WIMP-nucleon scattering interpretation of the excess reported by CoGeNT, which also uses a germanium tar- ⇤ Corresponding author: [email protected] get. Similar tension exists with WIMP interpretations [1] J. L. Feng, Ann. Rev. Astro. Astrophys., 48,495(2010). of several other experiments, including CDMS II (Si), [2] M. W. Goodman and E. Witten, Phys. Rev. D, 31,3059 assuming spin-independent interactions and a standard (1985). halo model. New regions of WIMP-nucleon scattering [3] R. Agnese et al. (CDMS Collaboration), Phys. Rev. Lett., for WIMP masses below 6 GeV/c2 are excluded. 111,251301(2013). [4] C. E. Aalseth et al. (CoGeNT Collaboration), Phys. Rev. D, 88,012002(2013). The SuperCDMS collaboration gratefully acknowl- [5] G. Angloher et al., Eur. Phys. J. C, 72,1971(2012). edges the contributions of numerous engineers and tech- [6] R. Bernabei et al., Eur. Phys. J. C, 67,39(2010). nicians. In addition, we gratefully acknowledge assis- [7] D. Hooper and T. Linden, Phys. Rev. D, 84,123005 tance from the sta↵ of the Soudan Underground Lab- (2011). [8] D. B. Kaplan, Phys. Rev. Lett., 68,741(1992). oratory and the Minnesota Department of Natural Re- [9] D. E. Kaplan, M. A. Luty, and K. M. Zurek, Phys. Rev. sources. The iZIP detectors were fabricated in the Stan- D, 79,115016(2009). ford Nanofabrication Facility, which is a member of the [10] A. Falkowski, J. Ruderman, and T. Volansky, J. High National Nanofabrication Infrastructure Network. This Energy Phys., 1105,106(2011). work is supported in part by the National Science Foun- [11] R. R. Volkas and K. Petraki, Int. J. Mod. Phys. A, 28, dation, by the United States Department of Energy, by 1330028 (2013). NSERC Canada, and by MultiDark (Spanish MINECO). [12] K. M. Zurek, (2013), arXiv:1308.0338. [13] R. Essig, J. Kaplan, P. Schuster, and N. Toro, (2010), Fermilab is operated by the Fermi Research Alliance, arXiv:1004.0691. LLC under Contract No. De-AC02-07CH11359. SLAC is [14] C. Cheung, J. T. Ruderman, L.-T. Wang, and I. Yavin, operated under Contract No. DE-AC02-76SF00515 with Phys. Rev. D, 80,035008(2009). the United States Department of Energy. [15] D. Hooper and W. Xue, Phys. Rev. Lett., 110,041302 Next for LUX

DAMA/LIBRA −40 10 ) 2 CoGeNT (2012) −41 CDMS II Si (2013) 10 CRESST II Updated analysis of 85d −42 10 - improved reconstruction lower threshold CDMS II Ge - −43 ZEPLIN III wall distribution into PLR? 10 - - complete DD calibration NEST update −44 - 10 XENON100 LUX 85d (2013) ! 300d run: above + WIMP − nucleon cross section (cm −45 10 - improved extraction field 127 Projected (2014-15)LUX 300 day run - Xe decayed away −46 10 1 2 3 10 10 10 m (GeV/c2) WIMP LZ: LUX + ZEPLIN

20-fold scale-up from LUX • reductions in PMT radioactivity achieved recently, so that other components will become more prominent in the overall background budget and therefore must meet more stringent radiopurity requirements (such Two-component asouter the PTFE used in reflecting surfaces). Secondly, an important enhancement beyond LUX is the • treatment of the skin layer of LXe located between the active TPC region and the inner cryostat wall, as detector system well as the region beneath the bottomHV PMT array. Once instrumentedscintillator with PMTs, this skin detector works in unison with the surrounding veto system, taking advantage of thedetector high scintillation yield of LXe to • 0.75 m thick Gd-loadeddetect radioactive backgrounds. LAB Lastly, LZ must surpass previous achievements in HV delivery to the scintillator shieldLXe space (c.f.: to ensure Daya reasonably strong electric fields in the WIMP target; our strategy is that voltages on insulating surfaces must be actively managed (graded) to prevent long-term buildup of electrostatic Bay) charge. In this section, we describe the baseline design of the detector and how these challenges have been addressed. • InstrumentedTPC Xedesign “skin” 7 ton The WIMP target is configured as a double-phase TPC containingLXe 7 tonnes of active LXe. The design is • Effective for neutronsmostly based on and the LUX detector, which has demonstrated excellent operational performance at the gammas 300 kg scale. The LZ TPC will be made from 2-cm-wide PTFE ringsTPC with 146 cm inner diameter, stacked to the same total height of 146 cm.water Hexagonal arrays of 3-inch phototubes (241 units each) are placed in the liquid, facing up, and in the gasshield phase, facing down, to detect the vacuum ultraviolet (VUV) light emitted when a particle interacts in the detector. The nominal operating pressure is 1.6 bar(a),

ﬁts in Davis Cavern

Figure1.6.5.1SchematicviewsoftheXedetector.The7tonneactiveregioniscontainedintheTPCfieldcage betweenthecathodeandgateelectrodes,viewedbyPMTarraysinthevaporandliquidphases.S2signal generationisachievedbetweentheliquidsurfaceandtheanode(shownright).TheHVconnectiontothecathode (left)usesadedicatedconduitleadingoutsideofthewatertank.BelowtheTPC,thereversefieldregiondegrades thecathodepotentialtolowvoltage.ThelateralskinPMTreadoutisshownoutsideoftheTPCfieldcage.

16 SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) !39 CDMS-II Ge Low Threshold (2011) Updated from !3

10 PICO250-C3F8 10 CDMSlite CoGeNT Snowmass Community Summer Study 2013 !40 (2013) (2012) CF1: WIMP Dark Matter Detection !4 10 CDMS Si 10 (2013)

# !41 !5 2 10 DAMA SIMPLE (2012) 10

COUPP (2012) pb # ! LZ Reach and cm ! !42 CRESST !6 10 ZEPLIN-III (2012) 10 S u pe !43 rCD CDMS II Ge (2009) !7 10 M EDELWEISS (2011) 10

S section S Xenon100 (2012) Snowmass section N N OL EU AB TR LUX (2013) !44 IN !8 10 O DarkSide 50 10 7Be C TT SuperCDMS Soudan OHE SCA ER cross

cross R T I EN 8 N PICO250-CF3I !45 Neutrinos B G LUX 300-day !9 10 10 Neutrinos Xenon1T DEAP3600 SuperCDMS SNOLAB 10!46 DarkSideLZ G2 10!10 nucleon nucleon

! ! !47 !11 10 (Green&ovals)&Asymmetric&DM&& 10 (Violet&oval)&Magne7c&DM& RING ATTE !48 (Blue&oval)&Extra&dimensions&& NT SC !12

E WIMP HER WIMP 10 (Red&circle)&SUSY&MSSM& CO 10 RINO The dominant background arises from &&&&&MSSM:&Pure&Higgsino&& NEUT !49 !13 10 &&&&&MSSM:&A&funnel& Atmospheric and DSNB Neutrinos 10 solar-neutrino-induced ERs that leak &&&&&MSSM:&BinoEstop&coannihila7on& !50 &&&&&MSSM:&BinoEsquark&coannihila7on& !14 into the NR region. In the ER band 10 & 10 1 10 100 1000 104 and energy range of 1.5-6.5 keVee, we expect a mean of 234 ER from WIMP Mass GeV c2 neutrinos originating predominantly in the pp fusion process in the sun, and scattering in LZ off of atomic ! " # electrons. The flux of pp neutrinos is 3 year run, limited primarily by predicted by solar models to better than 1%, assuming the solar (electron recoil) background of pp luminosity constraint, but there is uncertainty that arises from atomic solar neutrinos binding effects of electrons in the Xe atom, resulting in a pessimistic limited by nuclear scatter background? estimate of 270 ER from pp neutrinos. reach to 10-49 cm2 neutrino floor depends The ultimate level of ER from solar neutrinos in the LXe TPC will be well on rejecting pp solar constrained by studies of the “sideband” in ER energy extending Figure 4.1.1.3. The same information as Figure 4.1.1.2, very recent from 6.5-20 keVee, before 2ν double- SUSY theoretical expectations included. The green-colored regions beta decay from 136Xe dominates the are favored by recent scans of the five-parameter CMSSM, which spectrum of ER events. After applying include the most current constraints from LHC results [7]. The rose our baseline of 99.5% discrimination, and beige points are pMSSM models, where 15 parameters are this source of background has an scanned [8]. The number of standard deviations (σ) that quantify expectation value of 1.2(1.4) events in consistency are higher for models that are more inconsistent with the NR band in our acceptance region very recent LHC data. 1 picobarn is 10-36 cm2. (pessimistic estimate in parenthesis), contributing about two-thirds of the total background to a WIMP signal. The second largest source of background is the as-yet-unobserved coherent nuclear scattering from atmospheric neutrinos and neutrinos from the diffuse supernova neutrino background (DSNB), which contribute a mean of 0.3(0.45) events in the NR band. Nuclear recoils from the coherent scattering of solar neutrinos fall below the LZ energy threshold for the standard S1+S2 analysis. The third largest source of background is beta-decay electrons, generating ERs, emitted from 85Kr and the 222Rn chain, and we expect a mean contribution of 46(234) events prior to application of the 99.5% discrimination, and 0.23(1.2) events after. The pessimistic value in this case is substantially higher than for other expected background, and reflects the consequences of additional radon emanation. The ultimate level of radon in the TPC will be very well constrained by the measurement of alpha-particles in the radon decay chain. The other two sources in Table 4.1.1.2 contribute less than 10% of the total expected background. We use the backgrounds described in the third column of Table 4.1.1.2 to derive the projected sensitivity of LZ to WIMPs. The resulting sensitivity plot is shown in Figure 4.1.1.2 along with the current LUX limit and the projected LUX sensitivity. The best (lowest) sensitivity shown, at a mass of 50 GeV/c2, is 2 ×10-48 cm2, which is 2 ×10-12 pb. The discovery potential for evidence at 3 standard deviations is also shown in Figure 4.1.1.2. Figure 4.1.1.3 redisplays the information in Figure 4.1.1.2, but includes regions and points in the same parameter space that are consistent with very recent evaluations made with SUSY models, which have

4-4 Test platform for LZ prototyping Lab Activities at SLAC and long-term R&D Fundamental measurements

45 cm

80 cm Test TPC in 100 kg LXe @ 170 K Puriﬁcation Tower

HV feedthrough LXe vessels w/200 kV (drift ﬁeld) feedthrough ports for LZ system test

high-ﬂow pneumatically controlled Xe circulation & Removal of trace radioactive 85Kr puriﬁcation panel thermosyphon w/gasdewar charcoal chromatography

thermosyphon lines (3)

gas control condenser panel charcoal column sampling RGA feed & recovery Xe recovery bottles pumps

graduate student Former BaBar “IR2” complex Repurposed electronics hut: LZ / liquid nobles test stand

LSST Clean Room

pump shed

Xe storage LZ / liquid nobles test stand

LN thermosyphon and controls

Phase I & II system test

Re-furbished LUX Kr removal for R&D Kr removal: reduction to 0.015 ppt ~ 10% pp solar ν 10 tons / 60 days @ 200 kg/day X 2 passes 500 SLPM He 250 SLPM He 500 mbar (Fluitron compressor) (dry backing pump) 100 mbar 16 kg thermosyphon

charcoal LN Xe 500 kg cryocooler

U RGA cooled Kr trap ﬁlter sampling 50 SLPM Xe 10 mbar 2 bar 80 bar Xe/Kr 250 SLPM He chromatography (Roots booster) Xe storage feed/purge ~ 120 min He Xe Xe recovery ~ 120 min

condensers

200 kg capacity 24 hour cycle (per condenser) automation of all 3 cycles 10 Direct Detection Program Roadmap 39

SuperCDMS Soudan CDMS-lite SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) 10!39 CDMS-II Ge Low Threshold (2011) 10!3 CoGeNT PICO250-C3F8 !40 (2012) !4 10 CDMS Si 10 (2013)

# !41 !5 Summary 2 10 DAMA SIMPLE (2012) 10

COUPP (2012) pb # cm !

! !42 CRESST !6 10 ZEPLIN-III (2012) 10 SuperCDMS !43 CDMS II Ge (2009) !7 10 EDELWEISS (2011) 10 SNOLAB SuperCDMS Soudan section section N EU TR Xenon100 (2012) !44 IN DarkSide 50 !8 10 O 10 7Be C TT LUX OHE SCA ER cross cross R NT I Neutrinos E 8 N !45 B G PICO250-CF3I !9 10 Neutrinos 10 Xenon1T Dark matter !46 DEAP3600 !10 10 DarkSide G2 10 LZ nucleon nucleon

• ! ! !47 !11 10 (Green&ovals)&Asymmetric&DM&& 10 (Violet&oval)&Magne7c&DM& ING detection - TER AT !48 (Blue&oval)&Extra&dimensions&& NT SC !12

E WIMP HER WIMP 10 (Red&circle)&SUSY&MSSM& CO 10 RINO &&&&&MSSM:&Pure&Higgsino&& NEUT !49 !13 10 &&&&&MSSM:&A&funnel& Atmospheric and DSNB Neutrinos 10 exciting future &&&&&MSSM:&BinoEstop&coannihila7on& !50 &&&&&MSSM:&BinoEsquark&coannihila7on& !14 10 & 10 1 10 100 1000 104 Liquid xenon WIMP Mass GeV c2 −40 ! " # • Figure10 26. A compilation of WIMP-nucleon spin-independent cross section limits (solid curves), hints )

for WIMP2 signals (shaded closed contours) and projections (dot and dot-dashed curves) for US-led direct TPCs playing detection experiments that are expected to operate over the next decade. Also shown is an approximate band where−41 coherent scattering of 8B solar neutrinos, atmospheric neutrinos and di↵use supernova neutrinos with nuclei10 will begin to limit the sensitivity of direct detection experiments to WIMPs. Finally, a suite of key role theoretical model predictions is indicated by the shaded regions, with model references included. −42 10 We believe that any proposed new direct detection experiment must demonstrate that it meets at least one of the following two criteria: −43 10 300-day data set Provide at least an order of magnitude improvement in cross section sensitivity for some range of • • WIMP masses−44 and interaction types. 10 Demonstrate the capability to confirm or deny an indication of a WIMP signal from another experiment. for LUX ~ 4-5x • WIMP − nucleon cross section (cm −45 The US has10 a clear leadership role in the field of direct dark matter detection experiments, with most major collaborations having major involvement of US groups. In order to maintain this leadership role, and to reduce the risk inherent in pushing novel technologies to their limits, a variety of US-led direct search −46 10 1 2 3 LZ approaches 10 10 10 m (GeV/cCommunity2) Planning Study: Snowmass 2013 • WIMP neutrino floor Thank you…

110 researchers from 17 institutions and 3 countries

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