DirectDirect DarkDark MatterMatter SearchesSearches –– StatusStatus andand PerspectivesPerspectives

MarcMarc SchumannSchumann UnivUniversityersity ofof FreiburgFreiburg

Particle Physics Seminar, Oxford, February 14, 2017 [email protected] M. Schumann (Freiburg) – Direct Dark Matter Searches 1 Dark Matter: (indirect) Evidence

Particle Dark Matter Candidates: – WIMP → „WIMP miracle“ – Axion – SuperWIMPs – sterile neutrinos – WIMPless dark matter – Gravitino Planck – ...

H. Baer Dark Matter Search

Direct Detection

Indirect Production Detection @Collider

M. Schumann (Freiburg) – Direct Dark Matter Searches 3 Direct WIMP Search

WIMP

Elastic Scattering of WIMPs off target nuclei WIMP  nuclear recoil v ~ 230 km/s Nuclear Recoil ER ~ O(10 keVnr) Detectable Signal

χ χ gamma- and beta-particles (background) interact with the ƒ ƒ atomic electrons → electronic recoil [in keVee]

M. Schumann (Freiburg) – Direct Dark Matter Searches 4 Direct WIMP Search

Xenon Germanium Direct Detection: A² Argon Silicon Er  100 keV R  1 evt/kg/year form factor

m=100 GeV/c²  =4x10–43 cm² ) 4 1

Recoil Energy: 0

WIMP Expectations 2 (

spin-independent interactions 7 6 0

, 8 0 4 1 1 event/kg/yr P

Event Rate: E H

CMSSM J

Detector Local DM Physics 1 event/ton/yr Density

ρχ~0.3 GeV/c² light WIMPs: asymmetric DM, M. Schumann (Freiburg) – Direct Dark Matter Searches sneutrinos, ... 5 WIMP-Nucleon Interactions

A priori, we do not know how dark matter WIMPs interact with ordinary matter

Parametrization of interactions leading Form factors describe to WIMP-nucleus scattering: loss of coherence → mainly for heavy targets coupling to mass coupling to nuclear spin and tail of v-distribution Spin independent Spin dependent PRD 91, 043520 (2015) χ - quark (SI, scalar) χ - quark (SD, axial)

PRD 88, 083516 (2013)

Jungmann et al. '96 Phys.Rep.

often: express SD results in proton-only or neutron-only

M. Schumann (Freiburg) – Direct Dark Matter Searches 6 Direct WIMP Search

Xenon Germanium Direct Detection: A² Argon Silicon Er  100 keV R  1 evt/kg/year form factor

m=100 GeV/c²  =4x10–43 cm² How to build a WIMP detector? ● large total mass, high A )

● 4

low energy threshold 1 0

WIMP Expectations 2 ● ( ultra low background spin-independent interactions 7 6

● 0

good signal / background , 8 0 4

discrimination 1 1 event/kg/yr P E H We are dealing with J ● extremely low rates (O(1) Hz) ● extremely low thresholds (~2 keV) 1 event/ton/yr ● extremely low radioactive backgrounds

M. Schumann (Freiburg) – Direct Dark Matter Searches 7 M. Schumann (Freiburg) – Direct Dark Matter Searches 8 Background Sources muons high-E neutrinos → CNNS bg pp+7Be neutrinos → NR signature → ER signature muon- induced neutrons

neutrons from (α,n) and sf

natural γ-bg

natural γ-bg target-intrinsic bg: α-, β-, γ-radiation, n; neutrons from activation, impurities, (α,n) and sf 2νββ Electronic Recoils Nuclear Recoils (gamma, beta) (neutron, WIMPs)

M. Schumann (Freiburg) – Direct Dark Matter Searches 9 The U and Th Chains

noble gas, present in air

M. Schumann (Freiburg) – Direct Dark Matter Searches 10 Low-background Screening JINST 11, P12017 (2016) Vue des Alpes Laboratory (600 mwe)

A

s

t

r

o

p

a

r

t

.

background:

P

h

~246 cnts/day y

s

.

3

5

,

4

3

(

2

0

1

1

)

low-background HV connector

Identify materials with lowest radioactivity:

● γ-spectrometry using HPGe Detectors ● mass spectroscopy: ICP-MS, GDMS ● neutron activation analysis ● 222Rn emanation

M. Schumann (Freiburg) – Direct Dark Matter Searches 11 Background Suppression ) 2 1 0 2 ( Avoid Backgrounds 3

7 5

, 5 3

Shielding . s y h P

.

deep underground location t r a p o r large shield (Pb, water, poly) t s active veto (µ,  coincidence) A

self shielding → fiducialization

Use of radiopure materials

Use knowledge about expected WIMP signal

WIMPs interact only once → single scatter selection requires some position resolution Examples: WIMPs interact with target nuclei ● scintillation pulse shape → nuclear recoils ● charge/light ratio exploit different dE/dx from ● ionization yield signal and background

M. Schumann (Freiburg) – Direct Dark Matter Searches 12 Direct WIMP Detection

Crystals (NaI, Ge, Si) Tracking: Cryogenic Detectors DRIFT, DMTPC Liquid Noble Gases MIMAC, NEWS CUORE NEWAGE

Superheated Phonons Liquids: SuperCDMS PICO CRESST SIMPLE EDELWEISS COSINUS

CoGeNT Charge Light CDEX DEAP-3600, CLEAN Malbek XENON, LUX/LZ DAMIC DAMA, KIMS ArDM, Panda-X XMASS, COSINE NEWS (gas) DarkSide, DARWIN ANAIS, SABRE

too many experimental efforts to report on → you will see a biased selection

M. Schumann (Freiburg) – Direct Dark Matter Searches 13 The WIMP Parameter Space

spin-independent WIMP-nucleon interactions coupling unknown

asymmetric dark matter coupling strength unknown Ps ric WIM gene SY) om SU (e.g. fr

WIMP mass unknown

M. Schumann (Freiburg) – Direct Dark Matter Searches 14 Detections?

spin-independent WIMP-nucleon interactions

M. Schumann (Freiburg) – Direct Dark Matter Searches 15 Exclusions?

spin-independent WIMP-nucleon interactions

some results are missing...

M. Schumann (Freiburg) – Direct Dark Matter Searches 16 Annual Modulation: DAMA/Libra

● PMTs coupled to NaI(Tl) Scintillators @ LNGS → extremely clean background necessary

● large mass and exposure: 1.17 t×y

● looks for annual modulation

PRD 33, 3495 (1986)

→ recoil spectrum gets harder and softer during the year → annually modulating signal (3% effect) → does not require many assumptions

M. Schumann (Freiburg) – Direct Dark Matter Searches 17 Annual Modulation: DAMA/Libra

● PMTs coupled to NaI(Tl) Scintillators @ LNGS → extremely clean background necessary

● large mass and exposure: 1.17 t×y

● looks for annual modulation

● DAMA finds annual modulation @ 9.3 CL

● BUT: no ER/NR discrimination! Reconcile DAMA/Libra with the null-results from other experiments assuming leptophilic dark matter? → DAMA might see electronic recoils

Examples: Axial-vector couplings: Kopp et al., PRD 80, 083502 (2009) Changet al., PRD 90, 015011 (2014) Bell et al., PRD 90, 035027 (2014) EPJ C 73, 2648 (2013) Mirror dark matter: Foot, Int.J.Mod.Phys. A29, 1430013 (2014) interpretation as (spin-(in)dependent, inelastic) WIMP- Luminous dark matter: nucleon scattering challenged by many experiments Feldstein et al., PRD 82, 075019 (2010)

M. Schumann (Freiburg) – Direct Dark Matter Searches 18 DAMA vs XENON Science 349, 851 (2015)

Average Rate

XENON100 @ LNGS Astropart. Phys. 35, 573 (2012) XENON100 excludes DAMA as being due to – result from XMASS PLB759, 272 (2016) – WIMP-e axial-vector couplings at 4.4σ → exposure comparable to DAMA – luminous dark matter at 4.6σ → result inconsistent with DAMA – mirror dark matter at 3.6σ M. Schumann (Freiburg) – Direct Dark Matter Searches 19 DAMA vs XENON Modulation arXiv:2017.00769 Detector

Pressure [bar]

Temperature [K]

Analysis

Cut Acceptance

Rate

Multiples (=background)

Singles (=signal)

M. Schumann (Freiburg) – Direct Dark Matter Searches 20 DAMA vs XENON Modulation arXiv:2017.00769

single scatter, low E → signal region (2-6 keV)

multiple scatter, low E

single scatter, low E ● additional data improves upon previous analysis PRL 115, 091302 (2015)

● no significant modulation observed

● Dark matter explanation of DAMA/LIBRA signal excluded @ 5.7σ

M. Schumann (Freiburg) – Direct Dark Matter Searches 21 New NaI Projects to test DAMA

aim at testing the DAMA claim using the same target/detector

→ main challenges: crystal purity, low threshold, target mass

SABRE NIM A 845, 418 (2017) Sodium-iodine with Active Background REjection

Strategy: ● lower background: better crystals ✓, PMTs ● liquid scintillator veto against 40K (factor 10) ● lower threshold (PMTs directly coupled to NaI) ● North (LNGS) and South (Australia)

● Status: proof-of-principle prepared at LNGS (5 kg)

DM-Ice: 17 kg @ South Pole arxiv:1602.05939

COSINE = KIMS+DM-Ice ~100 kg @ Yangyang → start soon

ANAIS: 112 kg @ Canfranc → background ~2-3x DAMA

COSINUS R&D: EPJ C 76, 441 (2016) NaI with bolometric+light readout

M. Schumann (Freiburg) – Direct Dark Matter Searches 22 Cryogenic Detectors measure charge and heat (phonons) in crystals: SuperCDMS @ SNOLAB E deposition → temperature rise ΔT ● selected by NSF-DOE downselection

→ requires detecors at mK temperatures ● ~50 kg (upgrade to 400 kg possible) ● low threshold → focus on 1-10 GeV/c² mass range

● deeper lab, better materials & shield, 600 g improved resolution, electronics, ...

● 100 x 33.3 mm IZPs (1.4 kg Ge, 0.6 kg Si)

First results on low-mass WIMPs P

R

L

1

1

2

,

Crystals: Ge, (Si) cooled to few mK 2

4

1

– low heat capacity ls 3 i 0 o

2 n c

e o – T ~ μK (→ TES) (

2 i R t n 0 a o 1 tr

4 z c i le )

Very good discrimination n E oils o ec

I R lear → BUT: need to reject Nuc surface events Heat

Sensitivity Study: arXiv:1610.00006

M. Schumann (Freiburg) – Direct Dark Matter Searches 23 EDELWEISS-III

● operating 20 kg of Ge detectors in Modane Lab (F) ● 800 g Ge crystals measure ionization and heat (NTD sensors)

apply small voltage to extract charge

● interdigitized electrodes: fiducialization (~600 g) ● simultaneous measurement allows for NR/ER discrimination

JCAP 05, 019 (2016)

9 observed 6 expected

● new low-threshold result: 8 detectors with lowest thresholds (2.5–20 keVnr) → no statistically significant excess → 40× better limit than EDW-II @ 5 GeV/c² BDT: JCAP 05, 019 (2016) PL: EPJ C 76, 548 (2016) M. Schumann (Freiburg) – Direct Dark Matter Searches 24 Ge / Si: Status and Prospects

spin-independent WIMP-nucleon interactions

some projects are missing...

M. Schumann (Freiburg) – Direct Dark Matter Searches 25 Very low WIMP masses

very low threshold for sensitivity to very low-mass WIMPs: amplify signal → HV operation: Neganov-Luke effect to amplify charge signal

convert work done by E-field on e–-hole pairs to phonons

EDELWEISS plans: bias voltage 2017: 350 kg×d in HV mode afterwards:

E join forces with CDMS

SuperCDMS plans: 2018-20: construction initial recoil 3 eV/pair 2020: begin data taking

CDMSlite PRL 116, 071301 (2016) ● 625 g iZIP detector, 70 kg×d exposure ● Vb=69 V, 56 eVee threshold! 14 eVee resolution ● no ionization measured → no ER rejection

keV

M. Schumann (Freiburg) – Direct Dark Matter Searches 26 CRESST: the low-mass record

CRESST-II @ LNGS

- read phonons and scintillation light

- target: CaWO4 → multi-element material

- successful background reduction; data taking 2013-2015, 52 kg×d

- new result EPJ C, 76, 25 (2016) detector with 300 eVnr threshold

EPJ C, 76, 25 (2016) EPJ C, 76, 25 (2016) e/γ

O lowest threshold W lowest background EPJ C 74, 3184 (2014) WIMP ROI

CRESST excludes CRESST

1 GeV/c²

M. Schumann (Freiburg) – Direct Dark Matter Searches 27 CRESST: the low-mass record

CRESST-II @ LNGS

- read phonons and scintillation light

- target: CaWO4 → multi-element material

- successful background reduction; data taking 2013-2015, 52 kg×d

- new result EPJ C, 76, 25 (2016) detector with 300 eVnr threshold

CRESST-III: lower threshold to 100 eVnr arXiv:1503.08065

- smaller crystals (250 g → 24 g) Reindl @ Lake Louise 2016

- all-scintillating detector design → avoid partial energy depositions

- improve signal-to-noise

Status: ● Prototype exceeds design goal: 50 eVnr threshold

● commissioning and calibration started 2016

M. Schumann (Freiburg) – Direct Dark Matter Searches 28 CRESST: Status and Prospects

spin-independent WIMP-nucleon interactions

some projects are missing...

M. Schumann (Freiburg) – Direct Dark Matter Searches 29 Liquid Noble Gases: Detector Concepts

Single Phase Detector PMT

liquid target e d u

t S1 i l p m A Time + no high voltage, very high light yield – M.O(cm) Schumann resolution, (Freiburg) – Directno double Dark Matter scatter Searches rejection 30 Noble Gas: Single Phase Detectors

XMASS @ Kamioka (JP) LXe DEAP-3600 @ SNOLAB (CA) LAr

– 832 kg LXe target, 642 PMTs – light pulse-shape for discrimination – very high light yield, low threshold (0.5 keVee) 3×10–8 achived in 43-86 keVee BUT: no possibility to reject NRs → prediction: 10–10 above 15 keVee in DEAP-3600 – many results: summary: arXiv:1506.08939 – 3.6t liquid argon target; high 39Ar background when using natAr (~1 Bq/kg) – background reduced after commissioning run – data taking right now... high light yield, → stable data taking since >2 years → results expected in spring 2017 – plans towards XMASS-1.5t and XMASS-II (24t) – sensitivity: 1×10–46 cm² @ 100 GeV/c² ) 5 1 0 2

E N I D I L (

e r e i t e R

. F

M. Schumann (Freiburg) – Direct Dark Matter Searches 31 Noble Gas: Single Phase Detectors

XMASS @ Kamioka (JP) LXe DEAP-3600 @ SNOLAB (CA) LAr

– 832 kg LXe target, 642 PMTs – light pulse-shape for discrimination – very high light yield, low threshold (0.5 keVee) 3×10–8 achived in 43-86 keVee BUT: no possibility to reject NRs → prediction: 10–10 above 15 keVee in DEAP-3600 – results: (low-mass) WIMPs, inelastic WIMP scat., – 3.6t liquidAstropart. argon Phys. target; 85, 23 (2016) axions, bosonic superWIMPs, rare decays high 39Ar background when using natAr (~1 Bq/kg) → summary: arXiv:1506.08939 – under commissioning; – background reduced after commissioning run started cool-down and filling with LAr... → stable operation since 2 years – sensitivity: 1×10–46 cm² @ 100 GeV/c² – plans towards XMASS-1.5t and XMASS-II (24t) Nuclear Recoils ) 5 1 0 2

Electronic Recoils E N I D I L (

e r e i t e R

. F

M. Schumann (Freiburg) – Direct Dark Matter Searches 32 Noble Gas: Single Phase Detectors

XMASS @ Kamioka (JP) LXe DEAP-3600 @ SNOLAB (CA) LAr

– 832 kg LXe target, 642 PMTs – light pulse-shape for discrimination – very high light yield, low threshold (0.5 keVee) 3×10–8 achived in 43-86 keVee BUT: no possibility to reject NRs → prediction: 10–10 above 15 keVee in DEAP-3600 – many results: summary: arXiv:1506.08939 – 3.6t liquid argon target; high 39Ar background when using natAr (~1 Bq/kg) – background reduced after commissioning run – data taking right now... high light yield, → stable operation since 2 years → results expected in spring 2017 – plans towards XMASS-1.5t and XMASS-II (24t) – sensitivity: 1×10–46 cm² @ 100 GeV/c² ) 6 1 0 2

M future: D I (

k DEAP-50T a i

n 150t target z u 50t fiducial K

.

M → 150 m² photo-coverage!

M. Schumann (Freiburg) – Direct Dark Matter Searches 33 Liquid Noble Gases: Detector Concepts

Single Phase Detector Time Projection Chamber

PMT pos HV gas

E

liquid target neg HV e e d d u u t S1 t i i l l S1 S2 p p m m A A Time Time + no high voltage, very high light yield + O(mm) resolution, S2/S1 NR rejection – M.O(cm) Schumann resolution, (Freiburg) – Directno double Dark Matter scatter Searches rejection – technical challenges (HV), less light 34 Dual Phase TPC

P

R

L

1

0

7

,

1

3

1

ER 3

0

2

(

2

0

1

1

NR )

3dim vertex reconstruction Astropart. Phys. 35, 573 (2012) multi-scatter ER rejection charge signal S2

151 µs light signal S1

NR

Figures from XENON100 M. Schumann (Freiburg) – Direct Dark Matter Searches 35 Existing dual phase detectors

LXe LXe LAr PandaX-II @ CJPL (CN) LUX @ SURF (USA) DarkSide-50 @ LNGS (IT) PRL 117, 121303 (2016) PRL 118, 021303 (2017) PRD 93, 081101 (2016)

- 60cm×60cm, 500 kg target - 48cm×48cm, 251 kg target - 46 kg LAr, which is - 2nd largest operational LXe TPC - in-situ NR calibration studies 39Ar-depleted by a factor 1400 arXiv:1608.05381 - 71d×37kg exposure

New result July 2016: New result July 2016: - no event in ROI - combines data from 2 runs - 332d exposure: - taking data (85Kr differs by factor 10) 3.4×104 kg×d 4 - 3.3×10 kg×d = 0.1 t×y exposure = 0.1 t×y - no signal excess - no signal excess - best limit above ~4.5 GeV/c² - 2.2×10–46 cm² - still taking data @ 50 GeV/c² aim for 2 years of data - stopped

PRL 112, 091303 (2014) re-analysis: arXiv 1512.03506

50 PE ~ 25 keVr LXe XENON100 @ LNGS (IT) New: 447 live days PRD 94, 122001 (2016) low-mass WIMPs PRD 94, 092001 (2016) M. Schumann (Freiburg) – Direct Dark Matter Searches 36 Existing dual phase detectors

LXe LXe LAr PandaX-II @ CJPL (CN) LUX @ SURF (USA) DarkSide-50 @ LNGS (IT) PRL 117, 121303 (2016) PRL 118, 021303 (2017) PRD 93, 081101 (2016)

- 60cm×60cm, 500 kg target - 48cm×48cm, 251 kg target - 46 kg LAr, which is - 2nd largest operational LXe TPC - in-situ NR calibration studies 39Ar-depleted by a factor 1400 arXiv:1608.05381 - 71d×37kg exposure

New result July 2016: New result July 2016: - no event in ROI - combines data from 2 runs - taking data - 332d exposure: (85Kr differs by factor 10) 3.4×104 kg×d 4 - proposal for DarkSide-20k - 3.3×10 kg×d = 0.1 t×y exposure = 0.1 t×y → 30t depleted Ar needed - no signal excess - no signal excess - best limit above ~4.5 GeV/c² - 2.2×10–46 cm² - still taking data, @ 50 GeV/c² aim for 2 years of data - stopped 5736 ch, SiPM )

PRL 112, 091303 (2014) 6 1

re-analysis: arXiv 1512.03506 0 2

M D I (

o l l i r o i F

50 PE ~ 25 keVr . LXe G XENON100 @ LNGS (IT) New: 447 live days PRD 94, 122001 (2016) low-mass WIMPs PRD 94, 092001 (2016) M. Schumann (Freiburg) – Direct Dark Matter Searches 37 High WIMP-masses TPC dominated

≥4.5 GeV/c² spin-independent WIMP-nucleon interactions

some projects are missing...

M. Schumann (Freiburg) – Direct Dark Matter Searches 38 LXe XENON1T @ LNGS

M. Schumann (Freiburg) – Direct Dark Matter Searches 39 M. Schumann (Freiburg) – Direct Dark Matter Searches 40 M. Schumann (Freiburg) – Direct Dark Matter Searches 41 XENON1T

- largest LXe TPC ever built cylinder: 96 cm active LXe target: 2.0t (3.2t total) 248 PMTs - operating: taking science data

M. Schumann (Freiburg) – Direct Dark Matter Searches 42 M. Schumann (Freiburg) – Direct Dark Matter Searches 43 XENON1T Performance

Water shield filled since Summer...

M. Schumann (Freiburg) – Direct Dark Matter Searches 44 XENON1T Performance

Water shield continuously filled since Summer...

Cerenkov detector sees muons...

M. Schumann (Freiburg) – Direct Dark Matter Searches 45 XENON1T Performance

Recording light (S1) and light signals (S2) from the entire detector

S1: light S2: charge

single scatter interaction

Calibration: external (137Cs, AmBe), internal (83mKr, 220Rn)

Cs137: 83mKr Backgrounds preliminary S1+S2 energy scale ● material background low, self-shielding effective

96cm ● 222Rn background agrees with predictions

● online removal of 85Kr via cryogenic distillation very successful

M. Schumann (Freiburg) – Direct Dark Matter Searches 46 XENON1T Performance

Recording light (S1) and light signals (S2) from the entire detector

S1: light S2: charge

single scatter interaction lowest natKr concentration ever achieved in LXe dark matter detector

Calibration: external (137Cs, AmBe), internal (83mKr, 220Rn)

Cs137: 83mKr Backgrounds preliminary S1+S2 energy scale ● material background low, self-shielding effective

96cm ● 222Rn background agrees with predictions

● online removal of 85Kr via cryogenic distillation very successful

M. Schumann (Freiburg) – Direct Dark Matter Searches 47 XENON1T Sensitivity JCAP 04, 027 (2016) based on detailed background predictions, 2 t×y exposure:

need only few weeks of data to reach current best sensitivity

assumptions: energy interval: 4 – 50 keVr, ER rejection as XENON100: 99.5% @ 50% NR acc. → expected LY is 2x higher than in XENON100!

M. Schumann (Freiburg) – Direct Dark Matter Searches confirmed by measurement! 48 XENON1T → XENONnT JCAP 04, 027 (2016) XENON1T XENONnT - 2t active LXe target - 6t active target - operating - projected to start - science run started end of 2018

Already existing: ● Muon Veto ● Cryostat Support ● Outer Cryostat ● in-LXe Cabling ~140cm ● LXe storage system ● Cryogenic system ● Purification system ● Kr removal ● DAQ ● 95% of Electronics ● Calibration System ● >300 PMTs ● ~8t of LXe ● Screening Facilities M. Schumann (Freiburg) – Direct Dark Matter Searches ● dedicated nT funding49 LZ – LUX/ZEPLIN arXiv:1509.02910

LXe

● LZ = LUX+ZEPLIN selected by 2014 US DOE-NSF downselection

● to be installed @ SURF (USA)

● 50× larger than LUX

10t total LXe mass, 7t active target, 5.6t fiducial target

● 488 R11410 PMTs

● 2015: started procurement of xenon gas, PMTs, ... 04/2020: end of construction

● goal: 2×10–48 cm² @ ~50 GeV/c² after 15 t×y exposure

M. Schumann (Freiburg) – Direct Dark Matter Searches 50 Dark Matter Searches: The Limit

spin-independent WIMP-nucleon interactions

„neutrino floor“ PRD 89, 023524 (2014)

some projects are missing...

M. Schumann (Freiburg) – Direct Dark Matter Searches 51 Dark Matter Searches: The Limit

spin-independent WIMP-nucleon interactionsJCAP 01, 044 (2014)

„neutrino floor“ Interactions from coherent neutrino-nucleus PRD 89, 023524 (2014) scattering (CNNS) will dominate → ultimate background for direct detection

M. Schumann (Freiburg) – Direct Dark Matter Searches 52 DARWIN The ultimate WIMP Detector

spin-independent WIMP-nucleon interactions

Exposure 0.1 ty 2 ty „neutrino floor“ 20 ty PRD 89, 023524 (2014) 200 ty IN DARW

some projects are missing...

M. Schumann (Freiburg) – Direct Dark Matter Searches 53 DARWIN The ultimate WIMP Detector JCAP 11, 017 (2016) LXe

● aim at sensitivity of a few 10–49 cm², limited by irreducible ν-backgrounds

● international consortium, 21 groups

→ R&D ongoing

Baseline scenario 260 cm ~50t total LXe mass ~40 t LXe TPC ~30 t fiducial mass

● Timescale: start after XENONnT

www.darwin-observatory.org

M. Schumann (Freiburg) – Direct Dark Matter Searches 54 DARWIN Backgrounds

high-E neutrinos Remaining background sources: → CNNS bg – Neutrinos (→ ERs and NRs) pp+7Be neutrinos → NR signature → ER signature – Detector materials (→ γ, n) – Xe-intrinsic isotopes (→ e–)

(assume 100% effective shield (~15m) against µ-induced background) JCAP 10, 016 (2015)

γ-bg materials

Xe-intrinsic bg: 222Rn, 85Kr, 2νββ neutrons from (α,n) and sf Electronic Recoils Nuclear Recoils (gamma, beta) (neutron, WIMPs)

M. Schumann (Freiburg) – Direct Dark Matter Searches only single scatters55 DARWIN WIMP Sensitivity

JCAP 10, 016 (2015) ● exposure: 200 t × y; all backgrounds included ● likelihood analysis ● 99.98% ER rejection @ 30% NR acceptance, S1+S2 combined energy scale, LY=8 PE/keV, 5-35 keVnr energy window spin-independent couplings spin-dependent couplings (n-only)

200 t×y: σ < 2.5 x 10–49 cm² @ 40 GeV/c² excellent complementarity to LHC searches

Phys.Dark Univ. 9-10, 51 (2015). M. Schumann (Freiburg) – Direct Dark Matter Searches 56 SUSY Dark Matter

plots: Sven Heinemeyer (MasterCode 2015) SUSY under pressure because not found at LHC? → true for some very constraint models (CMSSM etc.) but looks different when more parameters are left unconstrained

Example: pMSSM10 ← 10 SUSY parameters, e.g. EPJ C75, 422 (2015)

IN RW DA WIMP

mneutralino ≈ mchargino

WIMP out of reach of HL-LHC (best-fit regions not covered), but accessible by DARWIN

M. Schumann (Freiburg) – Direct Dark Matter Searches 57 WIMP Detection

ER-like (background) solar neutrinos, 85Kr, 222Rn, 2νββ, materials discrimination variable; based on S2/S1

WIMP: 30 GeV/c², =2×10–48 cm² 27 signal events in box NR-like (signal) CNNS+neutrons reconstructed energy, based on S1 and S2 signal

M. Schumann (Freiburg) – Direct Dark Matter Searches 58 WIMP Spectroscopy

Reconstruction: 2×10–47 cm² Target Complementarity

200 t×y

JCAP 11, 017 (2016) PRD 83, 083505 (2011) Capability to reconstruct WIMP parameters Reconstruction improves considerably ● m =20, 100, 500 GeV/c² by adding Ge-data to Xe. χ ● 1σ/2σ CI, marginalized over Only minimal improvement for Ar. astrophysical parameters ● due to flat WIMP spectra, no target can reconstruct masses >500 GeV/c²

M. Schumann (Freiburg) – Direct Dark Matter Searches 59 DARWIN The ultimate WIMP Detector

other than WIMPs

260 cm What (else) can we do with these instruments?

M. Schumann (Freiburg) – Direct Dark Matter Searches 60 Interactions in LXe Detectors

scattering off atomic electrons, excitations etc. → electronic recoil

● rare processes detectable if ER background is low

coherent scattering off xenon nucleus → nuclear recoil

● Dark Matter ● CNNS

Many science channels are accessible with a multi-ton DARWIN detector thanks to its extremly low ER background.

M. Schumann (Freiburg) – Direct Dark Matter Searches 61 Solar Axions, Dark Matter ALPs

JCAP 11, 017 (2016)

Solar axions Galactic ALPs

Axion Axions and ALPs couple to xenon arises naturally in the Peccei-Quinn solution via axio-electric-effect of the strong CP-problem → well-motivated dark matter candidate

→ axion ionizes a Xe atom Axion-like particle (ALP) generalization of the axion concept, but without addressing strong CP problem (ALPs = Nambu-Goldstone bosons from breaking of some global symmetry)

M. Schumann (Freiburg) – Direct Dark Matter Searches 62 M. Schumann (Freiburg) – Direct Dark Matter Searches 63 Low-E solar Neutrinos

Low-energy solar Neutrinos: pp, 7Be

→ vast majority of solar neutrinos; help to understand how the Sun works → very low energetic, hard to detect → mainly pp-neutrinos o n i x e r o B

: e g a m I

M. Schumann (Freiburg) – Direct Dark Matter Searches 64 pp-Neutrinos in DARWIN a background for the WIMP search JCAP 11, 017 (2016)

Differential Recoil Spectrum in Xe Neutrino interactions

● neutrinos interact with Xe electrons ● ER rejection efficiencies ~99.98% at →electronic recoil signature 30% NR efficiency are required to ● continuous recoil spectrum reduce to sub-dominant level → largest rate at low E

M. Schumann (Freiburg) – Direct Dark Matter Searches 65 pp-Neutrinos in DARWIN a new physics channel! JCAP 11, 017 (2016)

Differential Recoil Spectrum in Xe Neutrino interactions

● neutrinos interact with Xe electrons ● 30t target mass, 2-30 keV window →electronic recoil signature → 2850 neutrinos per year (89% pp) ● continuous recoil spectrum → achieve 1% statistical precision → largest rate at low E on pp-flux (→Pee) with 100 t x y ~0.26 ν evts/t/d in low-E region (2-30 keV)

M. Schumann (Freiburg) – Direct Dark Matter Searches 66 136Xe: 0ν double-beta Decay

JCAP 01, 044 (2014)

2νββ 0νββ

6t fiducial mass no 136Xe enrichment! EXO-200 limit

Background (6t): 4.6 evts/t/y in ±3σ

● σ/E~1% at Qββ, combined E-scale

● 25 signal in plot assumes T1/2=1.6 x 10 y 214 Bi 26 ● (95% CL, 6t x 5y) sensitivity: T1/2=5.6 x 10 y

● ultimate sensitivity (limited by intrinsic bg): 27 (95% CL, with 14t x 10y) T1/2=8.5 x 10 y

M. Schumann (Freiburg) – Direct Dark Matter Searches 67 0ν Double-beta Decay

JCAP 11, 017 (2016)

M. Schumann (Freiburg) – Direct Dark Matter Searches 68 M. Schumann (Freiburg) – Direct Dark Matter Searches 69 Supernova Neutrinos

Chakraborty et al., PRD 89, 013011 (2014) Lang et al., PRD 94, 103009 (2016)

● ν from supernovae could be detected via CNNS as well

● signal fom accretion phase of a ~18 Msun supernova @ 10 kpc is clearly visible in DARWIN

● signal: NRs plus precise time information

● challenge: theshold

accretion phase

M. Schumann (Freiburg) – Direct Dark Matter Searches 70 The WIMP Landscape today t n e s e r P

M. Schumann (Freiburg) – Direct Dark Matter Searches 71 Exciting times ahead of us

axions/ALPs solar neutrinos 0νββ

SN neutrinos t n e s

CNNS e r P

+more rare processes

e

r

u t u F

M. Schumann (Freiburg) – Direct Dark Matter Searches 72