(Brand-)New CRESST-II results on low-mass dark matter ... fileTES heat bath heat bath thermal coupling. 15 Transition Edge Sensor Temperature (mK) R e s i s t a n c e ΔT ΔR 0 10

MPP Colloquium Munich, September 08, 2015

(Brand-)New CRESST-II results on low-mass dark

matter particles

Florian Reindl Max-Planck-Institute for Physics Munich

for the CRESST Collaboration

2

Dark Matter

5%27%

68%Dark matter

Dark energy

Atoms Astronomy There is a lot of dark

matter in the Universe!

(Astro-) Particle PhysicsWhat is it made of?

3

Motivation for low-mass dark matter

WIMP “Miracle”

● Thermally produced in early Universe

● Weak scale yields correct relic density

● 10GeV/c2 ~ 1TeV/c2

4


WIMP “Miracle”




Asymmetric Dark Matter

● ΩDM/ΩB~5: Why?

● Link asymmetries for baryons and DM in early Universe

● 0.1GeV/c2 ~10GeV/c2

ΧΧ ΧAnnihilation

ΧBB

5


WIMP “Miracle”




Asymmetric Dark Matter

● ΩDM/ΩB~5: Why?

● Link asymmetries for baryons and DM in early Universe

● 0.1GeV/c2 ~10GeV/c2

ΧΧ ΧAnnihilation

ΧBB

6

Prospects in low mass dark matterMPI, Nov. 30 – Dec 1 2015

“The workshop aims to (…) open up the new area of low mass dark matter search.”

https://indico.mpp.mpg.de/event/dmworkshop

7

Detection Channels

8

Direct Dark Matter Detection

Most common scenario: dark matter particle scatter● off nuclei● elastically● coherently: ~A2

● (spin-independent)

Detection Techniques

CRESST-II (CaWO4)

DAMA/LIBRA (NaI)

(Super)CDMS (Ge,Si)EDELWEISS (Ge)

CoGeNT (Ge)

XMASS (Xe)

DEAP-3600 (Ar)

DAMIC (Si)

PICO (C3F8, CF3I)

CDEX (Ge)

10

The CRESST Collaboration

11

Laboratori Nazionali del Gran Sasso

3600 m.w.e.

12

The Cryogenic Rare Event Search with Superconducting

Thermometers

aims to detect elastic dark matter particle-nucleus scattering

uses scintillating CaWO4 crystals as target

13

Detector Module

Particle interaction in the crystal

Phonon signaldeposited energy

Scintillation lightparticle discrimination

14

Detector Module

Particle interaction in the crystal

Phonon signaldeposited energy

Scintillation lightparticle discrimination

reflective and scintillating housing

light detector (with TES)

target crystal

TES

heat bath

heat bath

heat bath

heat bath

thermal coupling

15

Transition Edge Sensor

Temperature (mK)

Re

sist

an

ce

ΔT

ΔR

0

10

16

17

Event Discrimination

light yield=light signalphonon signal

18

Event Discrimination

light yield=light signalphonon signal

ROI: Region of Interest for dark matter search

19

CRESST-II: Current Phase 2

● Data taking from July 2013

to August 2015

● Result discussed today

– Single module Lise

– 52 kg days of exposure

– Blind analysis

arXiv:1509.01515

http://arxiv.org/abs/1509.01515

20

Low Threshold Analysis - Motivation

WIMP Mass (GeV)1 10 210 310

Cou

nts

per k

g d

and

pb

10

210

310

410

510

10

O

W

Ca

1-40keV10-40keV10-40keV

21

Expectation

Energythreshold

Selectioncriteria

Acceptance region

22

Lise - Energy Threshold

Eth= 307eV

σ = 82eV (in agreement with gamma lines)

Precisely measured with pulses injected to the heater

Pile-Up probability: 5.6%

23

Lise - Energy Threshold

Eth= 307eV

σ = 80eV (in agreement with gamma lines)

Precisely measured with pulses injected to the heater

Pile-Up probability: 5.6%

Permanently Injected

24

Trigger: Long-term Stability

Trigger operating stably throughout entire data taking

25

Expectation

Energythreshold

Selectioncriteria

Acceptance region

26

Signal Survival Probability Determination

randomly sampled empty baseline

standard pulse

artificial pulse with randomly sampled

noise level and known energy

27

Signal Survival ProbabilityResult

● Acceptance down to threshold

● Rise-Time cut introduces energy-dependence

28

TES-Carrier (Composite Design)

Carrier crystal

TES

Absorber crystal

● Discrimination of events in carrier via pulse shape

● Challenging when approaching low energies

➔ CRESST-III: directly evaporate TES onto absorber

29

Expectation

Energythreshold

Selectioncriteria

Acceptance region

30

Data

e-/γ

O

W

31

Acceptance Region

e-/γ

O

W

50% of oxygenrecoils below

99.5% of tungstenrecoils above

32

Expectation

Energythreshold

Selectioncriteria

Acceptance region

Standard DM halo

Helm form factors

33

Observation

Data Acceptance region

34

Overall Background

179Ta (M1)

Cu (Kα)55FeLinear decrease

Flat background down to threshold!

~8.5 counts per (kg keV day)

External 55Fe source

Data-driven back-ground model

35

Overall Background

179Ta (M1)

Cu (Kα)55FeLinear decrease

Flat background down to threshold!

~8.5 counts per (kg keV day)

External 55Fe source

Data-driven back-ground model

Survival Probability

36

Overall Background – Zoom Out

37

Detector: Long-term Stability

Detector operating stably throughout entire data taking

38

Observation

Data Acceptance region

39

Acceptance Region

e-/γ

O

W

50% of oxygenrecoils below

99.5% of tungstenrecoils above

40

Accepted Events

41

Result

Expected energyspectrum

Observed energy spectrumYellin optimum interval

(one-dimensional)

42

CDMS

LUX

XENON-100

CR

ES

ST-II 2014

This analysis (2015)

CDMSlite

43

Multi-Element Target

above 3Gev/c2: W dominates

below 3Gev/c2: O dominates

44

Conclusions

● Blind analysis of detector with lowest threshold (307eV) operated in phase 2

● Significant improvement of 2014 limit below 2GeV/c2

● Exploring new parameter space down to 0.5GeV/c2

● Hunting light dark matter requires a low threshold!

45

CDMS

LUX

XENON-100

CR

ES

ST-II 2014

This analysis (2015)

CDMSlite

46

CRESST-II: Current Phase 2

● Result published in 2014:

– Single module TUM40


– Nonblinded 2013 dataset

● Result discussed today

– Single module Lise


– Blind analysis

47

Detector Designs



target crystal

TES

holding clamps

2015 - LiseConventional

block-shaped target crystal (with TES)


CaWO4 sticks(with holding clamps)


2014 - TUM40Stick

48

Detector Designs



target crystal

TES

holding clamps

● Veto for recoil backgrounds







2014 - TUM40Stick

49

Detector Designs



target crystal

TES

holding clamps


● Background level:

~8.5 counts / (keV kg day)









2014 - TUM40Stick

com

mer

cial

self-

grow

n

50

Detector Designs



target crystal

TES

holding clamps




● 307eV threshold

● 62eV resolution








~3.5 counts / (keV kg day)● 603eV threshold

● 100eV resolution

2014 - TUM40Stick

51

Detector Designs



target crystal

TES

holding clamps



~8 counts / keV kg day● 307eV threshold

● 62eV resolution








~3.5 counts / keV kg day● 603eV threshold

● 100eV resolution

2014 - TUM40Stick

Lowest trigger threshold

Superioroverall performance

52

Lise vs. TUM40 - Conclusions

● Self-grown crystals offer superior

radiopurity

● Hunting light dark matter requires a low threshold!

● Threshold independent of holding concept

53

New Modules for CRESST-III





Design goal:

Threshold of 100eV

How?

smaller crystals of available quality

250g → 24g

54

New Modules for CRESST-III

Design goal:

Threshold of 100eV

How?

smaller crystals of available quality

250g → 24g

Prototype(s) successfully tested (@MPI & @LNGS)

55

On the road to CRESST-III

● Prototype(s) successfully tested● Production of ~15 modules running full-steam

➔ Start of CRESST-III end of 2015

56

Projection for CRESST-III Phase 1&2

Phase 1● 50kg days: 10

modules, 1 year

arXiv:1503.08065

CRESST-II 2014



57

Projection for CRESST-III Phase 1&2

Phase 2● 1 tonne days:

100 modules, 2 years

● background improved by ~100

arXiv:1503.08065

CRESST-II 2014



58

Expos u

rePer

form

ance

CRESST has outstanding potential to explore the

low mass regime

Final Statement

Documents

(Brand-)New CRESST-II results on low-mass dark matter ... fileTES heat bath heat bath thermal coupling. 15 Transition Edge Sensor Temperature (mK) R e s i s t a n c e ΔT ΔR 0 10