direct detection - cern indico

M. Schumann (Freiburg) – Dark Matter 1

Direct DetectionStatus and Prospects of mid- to high-mass WIMP searches

Marc Schumann U Freiburg

ZPW 2019 „A new look to dark mattter“ Zurich, January 09, 2019

[email protected]

mailto:[email protected]

M. Schumann (Freiburg) – Direct Detection 3

Direct WIMP Search

Nuclear RecoilER ~ O(10 keVnr)

WIMP

WIMP

v ~ 230 km/s

Elastic Scattering of WIMPs off target nuclei nuclear recoil

Detectable Signal

Electronic Recoil

A²

form factor

XenonGermanium

ArgonSilicon

m=100 GeV/c² = 1x10–47 cm²

χ χ

ƒ ƒ

10–1

Rat

e [e

vent

s/(t

y k

eV)]

10–2

10–1

10–3

RecoilSpectra:


Direct WIMP Search

Nuclear RecoilER ~ O(10 keVnr)

WIMP

WIMP

v ~ 230 km/s

Elastic Scattering of WIMPs off target nuclei nuclear recoil

Detectable Signal

Electronic Recoil

A²

form factor

XenonGermanium

ArgonSilicon

m=100 GeV/c² = 1x10–47 cm²

χ χ

ƒ ƒ

10–1

Rat

e [e

vent

s/(t

y k

eV)]

10–2

10–1

10–3

tiny!

tiny! low mass → low threshold

RecoilSpectra:


Annual Modulation

Ethresh

3% of total rate


Current Status

spin-independent WIMP-nucleon interactions

some results are missing...


Current Status



Low-mass WIMPs→ see talk by Federica

0.1 0.5 4000


DAMA/LIBRA: New Resultsspin-independent WIMP-nucleon interactions

11.9σ CL

DAMA/LIBRA: Universe 4 (2018) 116

Phase 1Phase 2

~250 kg NaI(Tl)

New data: – 1 keVee threshold– 6 annual cycles


DAMA/LIBRA: New Resultsspin-independent WIMP-nucleon interactions

Phase 1Phase 2

I

Na

Phys.Lett. B789 (2019) 262


Exclusion by COSINE-100

COSINE-100– 106 kg of NaI(Tl)– 2000L liquid scint. veto → suppress 40K bckgnd– BUT: low-E background still 3x DAMA/LIBRA– no excess above background in 60 day run

Nature 564 (2018) 83

DAMA signal


Exclusion by COSINE-100

COSINE-100– 106 kg of NaI(Tl)– 2000L liquid scint. veto → suppress 40K bckgnd– BUT: low-E background still 3x DAMA/LIBRA– no excess above background in 60 day run4,

99 c

m

DM-nucleon scattering excluded by 5 orders of magnitude!

Nature 564 (2018) 83

DAMA signal


Annual Modulation Searches

– dark matter–electron scattering

– 2-phase LXe TPCs operated stably over long periods

XENON100: 4 yearsLUX: 2 years

– challenges DAMA/LIBRAXENON100: 5.7σLUX: 9.2σ

XENON100: PRL 118, 101101 (2017)

LUX: PRD 98, 062005 (2018)


Current Status


liquid noble gas TPCs:best results above ~1.8 GeV/c²


TPC = time projection chamber

Dual-Phase TPC

Time

Am

plitu

de

S2 – Charge→ proportional scintillation

neg HVE~0.5 kV/cm

pos HVE~10 kV/cm

TimeA

mpl

itude

Time

Am

plitu

de

S1 – Light

Dark Matter WIMP= single scatter nuclear recoil

Background (β, γ)

Background (neutron)

● 3d position reconstruction → target fiducialization

● background rejection

M. Schumann (Freiburg) – Dark Matter 15

Electronic Recoils Nuclear Recoils(gamma, beta) (neutron, WIMPs)

muons

natural γ-bg

neutrons from(α,n) and sf

target-intrinsic bg:β-radiation;activation, impurities,2νββ


muon-inducedneutrons

natural γ-bg

pp+7Be neutrinos→ ER signature

high-E neutrinos→ CNNS bg→ NR signature

Background Sources

natural γ-bg


muons

muon-inducedneutrons

(for ton-scale detectors)


ER Background Rejection

PR

L 107, 131

302 (2011)

ER

NR

Nuclear Recoils

Electronic Recoils

Astropart. Phys. 85, 23 (2016)Pulse shape discrimination (PSD):Lifetimes of singlet and triplet states:

Ar: 5 ns, 1.6 µsXe: 4 ns, 22 ns

Ratio Ntrip/Nsing depends on dE/dx→ the interaction type

LAr: excellent ~3×10–8

PRC 78, 035801 (2008)

LXe: irrelevant ~1×10–1

NIM A 612, 328 (2010), arXiv:1803.07935

Charge-Light-Ratio (S2/S1):Signal partition in light/charge depends → works for LXe and LAr (2-phase)on dE/dx → the interaction type → significant loss of acceptance

Edrift [kV/cm] LY @ 122 keV[PE/keV]

NR acc[%]

ER rej[%]

XENON100 0.53 3.8 40 2.5×10–3

XENON100 0.53 3.8 30 1×10–3

LUX 0.18 8.8 50 1..10×10–3

ZEPLIN-III 3.4 4.2 50 1.3×10–4

K. Ni APP14 0.2-0.7 10 50 <1×10–4

high thresholdrequired

works down tolow-E threshold


<5 GeV/c²: DarkSide-50PRL 121 (2018) 081307

Charge-only Analysis

– no light signal (S1) required → reduce threshold → give up z-fiducialization, ER rejection via PSD, S2/S1

– depleted Ar target (46 kg) 39Ar reduced by >3 orders of magnitude– exposure 0.02 t×y threshold: 0.1 keVee– background:

1.5 kg–1d–1keV–1 = 5.5 × 105 t–1y–1keV–1 – background understood down to ~7 electrons (~1.2 keVnr)

→ no excess observed


>5 GeV/c²: XENON1T

→ ER background: 85 t–1y–1keV–1

→ no statistically significant excess observed in 1t×y

200 GeV/c²

largest LXe TPC ever built cylinder: 96 cm active LXe target: 2.0t (3.2t total)

248 PMTs

PRL 121 (2018) 111302


Status Spin-Dependent Couplings● coupling of WIMP to unpaired nucleon spins

● traditionally separated in proton-only and neutron-only

● same parameter space explored by indirect and collider searches

WIMP-proton WIMP-neutron

*XENON1T curves estimated by scaling SI-result


PICO-60– 52 kg bubble chamber filled with C

3F

8

(„octafluoropropane“)– threshold detector– „immune“ to gamma/beta radiation– acoustic rejection of alphas

– 1167 kg×d exposure (efficiency corrected) = 3.2 × 10–3 t × y– 3.3 keVnr threshold

→ no excess observed

PICO-500 with 500L C3F

8 chamber

willl be built at SNOLAB

PRL 118 (2017) 251301


Upcoming Projects


Low-mass WIMPs→ see talk by Federica

0.1 0.5



Consolidation of the FieldZEPLIN-III0.01t

LUX0.25t

XENON1000.06t

XENONnT6.0t

PandaX-4t4.0t

XENON1T2.0t

DarkSide-500.04t

DEAP-36003.3t

ArDM0.8t

DarkSide-20k30t

PandaX-II0.5t

LZ7.0t

XMASS0.8t

LXe LAr

now


DarkSide-20k– scale up DS-50 by factor 400: 30t LAr total

20t fiducial

– focus on high-mass region >400 GeV/c²

– aim for background-free 100 t×y exposure → depleted underground Ar (URANIA+ARIA)→ pulse-shape discrimination → high LY needed→ liquid scintillator n-veto → NEW: LAr n-veto

– start @ LNGS within 2021

Readout by two arrays of grouped SiPMs: 14 m² total

Requirements: – PDE: 45% – Dark Count Rate:

0.1 Hz/mm²

G. Fiorillo @ UCLA-DM 2018Eur. Phys. J. Plus (2018) 133


PandaX-4t

– to be installed at CJPL-II; scale-up by factor 8

– 4t LXe target with 6×10–48 cm² sensitivity to SI interactions @ 40 GeV/c²

– assembly and commissioning: 2019-2020

Sci. China Phys. Mech. Astron. 62 (2019) 31011

368 PMTs


LZ – LUX/ZEPLIN

● 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,

● 494 R11410 PMTs

● spring 2020: first science data

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

arXiv:1703.09144


JCAP 04, 027 (2016)XENONnT

- @ LNGS using existing XENON1T systems(existing µ-veto + new Gd-based n-veto)

- 3x larger than XENON1T5.9t active LXe target ~8.5t total mass

- 494 R11410 PMTs (XENON1T+new)- start science by mid 2019- goal: ~2×10–48 cm² @ ~40 GeV/c²

~135cm

~150cm


XENON1T Stopped10.Dec 2018, 15:06:04 h

Last recorded event Water shield accessible again


The ultimate Limit


„neutrino floor“PRD 89, 023524 (2014)



The ultimate Limit


„neutrino floor“PRD 89, 023524 (2014)


some results are missing...some results are missing...

Interactions from coherent neutrino-nucleus scattering (CNNS) will dominate→ ultimate background for direct detection

JCAP 01, 044 (2014)


LXe-based

DARWIN The ultimate WIMP Detector

1 ty

20 ty

200 ty

Exposure

DARWIN

darwin-observatory.org


LXe-based

DARWIN The ultimate WIMP Detector

darwin-observatory.org

Baseline scenario~50t total LXe mass R&D started ~40 t LXe TPC~30 t fiducial mass

260 cm

JCAP 11, 017 (2016)

spin-dependent couplings (n-only)

JCA

P 1

0,

01

6 (

20

15

)


LXe: Radon Background WIMP ROI: 1–12 keV interval

XENON1T JCAP 04, 027 (2016)

Strategy XENONnT → DARWIN– avoid Rn by material selection– avoid Rn by detector design– NEW: active Rn removal

– cryogenic distillation XENON1T distillation column installed @ XENON100 → demonstrated reduction factor >27 (@ 95% CL) → dedicated column under development @ Münster

EPJ C 77, 358 (2017)

DARWIN goal:ER background dominatedby solar neutrinos

222Rn factor 100 below XENON1T→ this is the main

background challenge

(DEAP-3600 achieved 0.18 µBq/kg)


LXe: Krypton Removal

P R E L I M I N A R Y

– DARWIN goal: 0.03 ppt (~ 0.1 × pp-neutrinos)– removal by cryogenic distillation

XENON1T: custom designed distillation column EPJ. C 77, 275 (2017)natKr/Xe = (0.6±0.1) ppt achieved

by novel online distillation→ lowest value in LXe experiments ever

XENON1T column has produced gas sample <0.026 ppt = 2.6×10–14 (90% CL) → DARWIN goal achieved


Exciting Times for Direct Detection

● very diverse experimental landscape – many different projects

● 4 multi ton-scale experiments will get online in the next years

● very good prospects to reach neutrino floor in next decade

direct detection - cern indico

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