Direct Dark Matter Detection - Part III Julien Billard Institut de - - PowerPoint PPT Presentation

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Direct Dark Matter Detection - Part III Julien Billard Institut de Physique Nuclaire de Lyon / CNRS / Universit Lyon 1 Ecole de GIF September 19-24, 2016 1 Where to look for Dark Matter? 10 - 37 10 - 1 C D D A M 10 - 38 10 - 2 M I S

slide-1
SLIDE 1

Julien Billard Institut de Physique Nucléaire de Lyon / CNRS / Université Lyon 1 Ecole de GIF September 19-24, 2016

1

Direct Dark Matter Detection - Part III

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SLIDE 2

Where to look for Dark Matter?

2

1 10 100 1000 104 10-50 10-49 10-48 10-47 10-46 10-45 10-44 10-43 10-42 10-41 10-40 10-39 10-38 10-37 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 WIMP Mass @GeVêc2D WIMP-nucleon cross section @cm2D WIMP-nucleon cross section @pbD

CDMS II Ge (2009) Xenon100 (2012)

CRESST CoGeNT (2012) CDMS Si (2013)

EDELWEISS (2011)

DAMA

SIMPLE (2012) ZEPLIN-III (2012) COUPP (2012) LUX (2013) D A M I C ( 2 1 2 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

Everywhere !!

Julien Billard (IPNL) - GIF 2016

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SLIDE 3

Where to look for Dark Matter?

3

1 10 100 1000 104 10-50 10-49 10-48 10-47 10-46 10-45 10-44 10-43 10-42 10-41 10-40 10-39 10-38 10-37 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 WIMP Mass @GeVêc2D WIMP-nucleon cross section @cm2D WIMP-nucleon cross section @pbD

CDMS II Ge (2009) Xenon100 (2012)

CRESST CoGeNT (2012) CDMS Si (2013)

EDELWEISS (2011)

DAMA

SIMPLE (2012) ZEPLIN-III (2012) COUPP (2012) LUX (2013) D A M I C ( 2 1 2 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

Everywhere !! … Wait, not so fast !

Julien Billard (IPNL) - GIF 2016

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SLIDE 4

The neutrino background

4

WIMP Neutrino

Based on:

  • J. Billard, L. Strigari and E. Figueroa-Feliciano, PRD 89 (2014)
  • F. Ruppin, J. Billard, L. Strigari and E. Figueroa-Feliciano, PRD 90 (2014)
  • C. O’Hare, J. Billard, E. Figueroa-Feliciano, A. Green and L. Strigari, PRD 92 (2015)

Julien Billard (IPNL) - GIF 2016

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SLIDE 5

Neutrino Energy [MeV]

  • 1

10 1 10

2

10

3

10 ]

  • 1

.MeV

  • 1

.s

  • 2

Neutrino Flux [cm

  • 3

10 1

3

10

6

10

9

10

12

10

13

10

pp pep hep 7Be_384.3keV 7Be_861.3keV 8B 13N 15O 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 5

The neutrino flux at an Earth based detector:

Geo neutrinos are negligible

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 6

Neutrino Energy [MeV]

  • 1

10 1 10

2

10

3

10 ]

  • 1

.MeV

  • 1

.s

  • 2

Neutrino Flux [cm

  • 3

10 1

3

10

6

10

9

10

12

10

13

10

pp pep hep 7Be_384.3keV 7Be_861.3keV 8B 13N 15O 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 5

The neutrino flux at an Earth based detector: Solar neutrinos: pp-chain

Geo neutrinos are negligible

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 7

Neutrino Energy [MeV]

  • 1

10 1 10

2

10

3

10 ]

  • 1

.MeV

  • 1

.s

  • 2

Neutrino Flux [cm

  • 3

10 1

3

10

6

10

9

10

12

10

13

10

pp pep hep 7Be_384.3keV 7Be_861.3keV 8B 13N 15O 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 5

The neutrino flux at an Earth based detector: Solar neutrinos: pp-chain Solar neutrinos: CNO

Geo neutrinos are negligible

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 8

Neutrino Energy [MeV]

  • 1

10 1 10

2

10

3

10 ]

  • 1

.MeV

  • 1

.s

  • 2

Neutrino Flux [cm

  • 3

10 1

3

10

6

10

9

10

12

10

13

10

pp pep hep 7Be_384.3keV 7Be_861.3keV 8B 13N 15O 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 5

The neutrino flux at an Earth based detector: Solar neutrinos: pp-chain Solar neutrinos: CNO DSNB neutrinos

Geo neutrinos are negligible

The neutrino background

Julien Billard (IPNL) - GIF 2016

slide-9
SLIDE 9

Neutrino Energy [MeV]

  • 1

10 1 10

2

10

3

10 ]

  • 1

.MeV

  • 1

.s

  • 2

Neutrino Flux [cm

  • 3

10 1

3

10

6

10

9

10

12

10

13

10

pp pep hep 7Be_384.3keV 7Be_861.3keV 8B 13N 15O 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 5

The neutrino flux at an Earth based detector: Solar neutrinos: pp-chain Solar neutrinos: CNO DSNB neutrinos

  • Atm. neutrinos

Geo neutrinos are negligible

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 10

6

Neutrino interactions with Dark Matter experiment target material

Ν

  • Ν
  • σ: Cross Section
  • Er: Recoil Energy
  • Eν: Neutrino Energy
  • Gf: Fermi Constant
  • QW: Weak Charge ~ A
  • mN: Atomic Mass

Neutral current No flavor-specific terms!!! Same rate for νe, νµ, and ντ Ultimate background to direct detection

Nuclear recoil

  • Coherent neutrino-nucleus elastic scattering (CNS):

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 11

7

Neutrino interactions with Dark Matter experiment target material

  • Coherent neutrino-nucleus elastic scattering (CNS):

Depending on the Energy threshold, the CNS background can be very high!

  • 1 keV threshold -> 100 evt/ton/year on Ge detector

Recoil energy [keV]

  • 3

10

  • 2

10

  • 1

10 1 10

2

10 ]

  • 1

Event rate [(ton.year.keV)

  • 4

10

  • 1

10

2

10

5

10

8

10

pp pep hep 7Be_384.3keV 7Be_861.3keV 8B 13N 15O 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar Total

Energy threshold [keV]

  • 3

10

  • 2

10

  • 1

10 1 10

2

10 ]

  • 1

Number of events [(ton.year)

  • 4

10

  • 2

10 1

2

10

4

10

5

10

pp pep hep 7Be_384.3keV 7Be_861.3keV 8B 13N 15O 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar Total

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 12

Recoil energy [keV]

3 −

10

2 −

10

1 −

10 1 10

2

10 ]

  • 1

Event rate [(ton.year.keV)

4 −

10

1 −

10

2

10

5

10

8

10

2

cm

  • 45

= 4.4x10

  • n

χ

σ ,

2

= 6 GeV/c

χ

WIMP signal: m Total CNS background Weak neutrino-electron

8

Neutrino interactions with Dark Matter experiment target material

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 13

Recoil energy [keV]

3 −

10

2 −

10

1 −

10 1 10

2

10 ]

  • 1

Event rate [(ton.year.keV)

4 −

10

1 −

10

2

10

5

10

8

10

2

cm

  • 45

= 4.4x10

  • n

χ

σ ,

2

= 6 GeV/c

χ

WIMP signal: m Total CNS background Weak neutrino-electron

8

Neutrino interactions with Dark Matter experiment target material Neutrino-electron background

negligible for Ge cryogenic detectors BUT problematic for Xe based detectors

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 14

Recoil energy [keV]

3 −

10

2 −

10

1 −

10 1 10

2

10 ]

  • 1

Event rate [(ton.year.keV)

4 −

10

1 −

10

2

10

5

10

8

10

2

cm

  • 45

= 4.4x10

  • n

χ

σ ,

2

= 6 GeV/c

χ

WIMP signal: m Total CNS background Weak neutrino-electron

8

Neutrino interactions with Dark Matter experiment target material

WIMP or neutrino (8B)??

Neutrino-electron background

negligible for Ge cryogenic detectors BUT problematic for Xe based detectors

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 15

9

WIMP and neutrino equivalence:

➡ Using a maximum likelihood analysis where we fit a WIMP hypothesis to the different

neutrino components we can determine the WIMP-neutrino equivalent models

Xe target, no energy threshold, perfect energy resolution

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 16

10

In the case of a perfect spectral matching, we expect the sensitivity to scale as:

Saturation regime 2 orders of magnitude Discrimination High stats

8B

WIMP discovery potential:

  • 90% probability to get a 3 sigma or more WIMP discovery significance
  • Computed using a profile likelihood ratio test statistic

10-46 10-45 10-44 10-43 10-42 10-2 10-1 100 101 102 103 104 105 106 1e-05 0.0001 0.001 0.01 0.1 1 10 100 1000

SI discovery limit at 6 GeV/c2 [cm2] Number of expected 8B neutrino events

Exposure (ton-year)

∝ 1/√ M  T ∝ 1/MT

1% 2% 5% 10% 15% 20%

The neutrino background

(F. Ruppin et al., PRD 90 (2014))

Julien Billard (IPNL) - GIF 2016

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SLIDE 17

11

The neutrino background

(F. Ruppin et al., PRD 90 (2014))

Julien Billard (IPNL) - GIF 2016

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SLIDE 18

12

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 19

13

How to bypass this neutrino-induced saturation of the sensitivity?

  • 1. Reducing the systematic uncertainties on neutrino fluxes
  • 2. Annual modulation (first studied in J. H. Davis, JCAP 2015)
  • 3. Directional detection (first studied in P. Grothaus et al., PRD 2014)
  • 4. Target complementarity: combining data from several experiments, (F. Ruppin et al., PRD 2014)

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 20

14

Considering target complementarity from different experiments

➡ The additional discrimination power brought by using different targets is related by how

different are the WIMP-neutrino equivalent models

  • Moderate differences in the WIMP mass and in the SI cross sections (SI and CNS are coherent)
  • Huge differences in the SD case -> WIMP hypothesis can’t fit all experiments

Great complementarity in the SD-p case between Ge and F!

5 6 7 8 9 10 11 12 20 40 60 80 100 120 140 160 180

WIMP mass [GeV/c2] Target number of nucleons (A)

W Xe I Ge Ar Ca Si F O C

10-44 10-42 10-40 10-38 10-36 20 40 60 80 100 120 140 160 180

WIMP-nucleon cross section [cm2] Target number of nucleons (A)

W Xe I Ge Ar Ca Si F O C

SI SD p SD n

(F. Ruppin et al., PRD 90 (2014))

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 21

15

Results from target complementarity

  • Considering a 6 GeV WIMP mass and a fixed systematic of 16% for 8B neutrinos
  • Total number of neutrinos equally distributed amongst each target nuclei
  • No more saturation regime in the SD-p case with Xe+Ge+Si -> no waste in exposure!

Upcoming experiments should combine their data

X 3

10-45 10-44 101 102 103 104

SI discovery limit at 6 GeV/c2 [cm-2] Number of expected 8B neutrino events

Background Subtraction Saturation Regime Background Subtraction Xe Xe+Ge Xe+Ge+Si

10-38 10-37 101 102 103 104

SD (proton) discovery limit at 6 GeV/c2 [cm-2] Number of expected 8B neutrino events

Background Subtraction Saturation Regime Background Subtraction Xe Xe+Ge Xe+Ge+Si

X 50

Spin independent Spin dependent (proton)

(F. Ruppin et al., PRD 90 (2014))

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 22
  • [/]
  • []
  • []

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C D M S I I G e ( 2 9 ) X e n

  • n

1 ( 2 1 2 )

CRESST CoGeNT (2012) CDMS Si (2013) DAMA

S I M P L E ( 2 1 2 ) Z E P L I N

  • I

I I ( 2 1 2 ) C O U P P ( 2 1 2 ) L U X ( 2 1 3 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

8B

Neutrinos Atmospheric and DSNB Neutrinos

7Be

Neutrinos

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C R E S S T ( 2 1 4 ) EDELWEISS (2011) D A M I C ( 2 1 2 )

16

(J. Billard et al., PRD 89 (2014))

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 23
  • [/]
  • []
  • []

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C D M S I I G e ( 2 9 ) X e n

  • n

1 ( 2 1 2 )

CRESST CoGeNT (2012) CDMS Si (2013) DAMA

S I M P L E ( 2 1 2 ) Z E P L I N

  • I

I I ( 2 1 2 ) C O U P P ( 2 1 2 ) L U X ( 2 1 3 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

8B

Neutrinos Atmospheric and DSNB Neutrinos

7Be

Neutrinos

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C R E S S T ( 2 1 4 ) EDELWEISS (2011) D A M I C ( 2 1 2 )

16

  • First detection of CNS!
  • Diversifying toward solar neutrino physics

(J. Billard et al., PRD 91 (2015))

(J. Billard et al., PRD 89 (2014))

The neutrino background

Julien Billard (IPNL) - GIF 2016

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SLIDE 24
  • [/]
  • []
  • []

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C D M S I I G e ( 2 9 ) X e n

  • n

1 ( 2 1 2 )

CRESST CoGeNT (2012) CDMS Si (2013) DAMA

S I M P L E ( 2 1 2 ) Z E P L I N

  • I

I I ( 2 1 2 ) C O U P P ( 2 1 2 ) L U X ( 2 1 3 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

8B

Neutrinos Atmospheric and DSNB Neutrinos

7Be

Neutrinos

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C R E S S T ( 2 1 4 ) EDELWEISS (2011) D A M I C ( 2 1 2 )

17

  • J. Billard et al., PRD 89 (2014)

The neutrino background

Julien Billard (IPNL) - GIF 2016

slide-25
SLIDE 25
  • [/]
  • []
  • []

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C D M S I I G e ( 2 9 ) X e n

  • n

1 ( 2 1 2 )

CRESST CoGeNT (2012) CDMS Si (2013) DAMA

S I M P L E ( 2 1 2 ) Z E P L I N

  • I

I I ( 2 1 2 ) C O U P P ( 2 1 2 ) L U X ( 2 1 3 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

8B

Neutrinos Atmospheric and DSNB Neutrinos

7Be

Neutrinos

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C R E S S T ( 2 1 4 ) EDELWEISS (2011) D A M I C ( 2 1 2 )

17

  • J. Billard et al., PRD 89 (2014)

Low WIMP mass High WIMP mass

The neutrino background

Julien Billard (IPNL) - GIF 2016

slide-26
SLIDE 26
  • [/]
  • []
  • []

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C D M S I I G e ( 2 9 ) X e n

  • n

1 ( 2 1 2 )

CRESST CoGeNT (2012) CDMS Si (2013) DAMA

S I M P L E ( 2 1 2 ) Z E P L I N

  • I

I I ( 2 1 2 ) C O U P P ( 2 1 2 ) L U X ( 2 1 3 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

8B

Neutrinos Atmospheric and DSNB Neutrinos

7Be

Neutrinos

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C R E S S T ( 2 1 4 ) EDELWEISS (2011) D A M I C ( 2 1 2 )

18

  • J. Billard et al., PRD 89 (2014)

Low WIMP mass High WIMP mass

Julien Billard (IPNL) - GIF 2016

High WIMP mass region (10 GeV - 1 TeV)

slide-27
SLIDE 27

19

Basics of direct detection

The « wish list » for a standard direct detection experiment:

  • Low and controlled backgrounds (so that they can be subtracted)
  • Discrimination between signal and background (to further reduce the background)
  • Large exposure (few events per ton-year)
  • Low energy threshold (the lower, the better, especially for low WIMP mass)

Julien Billard (IPNL) - GIF 2016

slide-28
SLIDE 28

19

Basics of direct detection

The « wish list » for a standard direct detection experiment:

  • Low and controlled backgrounds (so that they can be subtracted)
  • Discrimination between signal and background (to further reduce the background)
  • Large exposure (few events per ton-year)
  • Low energy threshold (the lower, the better, especially for low WIMP mass)

Julien Billard (IPNL) - GIF 2016

slide-29
SLIDE 29

20

  • Liquid above LN2 (77K): easy cryogenics
  • Good scintillators (do not absorb its own light), and good electron lifetime
  • Allow for active discrimination: scintillation and ionization (+ pulse shape in Ar)
  • Can be purified to remove radioactive contaminants such as 37Ar, 85Kr, 127Xe, 39Ar
  • « Easy » to scale to tons of detector material

High WIMP mass region (10 GeV - 1 TeV)

Courtesy M. Schumann

slide-30
SLIDE 30

21

High WIMP mass region (10 GeV - 1 TeV)

Dual phase TPC

liquid/gas DEAP MiniCLEAN DarkSide ArDM XMASS XENON-1T,nT LUX LZ PANDAX

Single phase

liquid only

Julien Billard (IPNL) - GIF 2016

slide-31
SLIDE 31

22

  • The recoiling nucleus/electron releases its energy in heat/ionization/scintillation
  • Electrons drifted to the gaseous phase undergo an avalanche process producing light (S2)
  • Recovering the true nuclear recoil energy is not trivial !!!

How is the energy released in a Xe-based experiment?

High WIMP mass region (10 GeV - 1 TeV)

Julien Billard (IPNL) - GIF 2016

Courtesy T. Schutt

slide-32
SLIDE 32

23

High WIMP mass region (10 GeV - 1 TeV)

What is the detection strategy?

  • Measure primary scintillation light (S1)
  • Measure secondary scintillation light from

ionization avalanche (S2)

  • Drift time give the Z-position of the event
  • PMTs give energy information and XY position

Julien Billard (IPNL) - GIF 2016

slide-33
SLIDE 33

23

High WIMP mass region (10 GeV - 1 TeV)

What is the detection strategy?

  • Measure primary scintillation light (S1)
  • Measure secondary scintillation light from

ionization avalanche (S2)

  • Drift time give the Z-position of the event
  • PMTs give energy information and XY position

Julien Billard (IPNL) - GIF 2016

slide-34
SLIDE 34

24

High WIMP mass region (10 GeV - 1 TeV)

What is the detection strategy?

  • S2 is larger for electronic recoils than for nuclear recoils (discrimination)
  • However, rejection efficiency is about 99,5% for a 50% nuclear recoil acceptance
  • Thanks to the XYZ positioning, we can select only events happening in the bulk of the

detector (fiducialization)

Julien Billard (IPNL) - GIF 2016

LUX, IDM2016

slide-35
SLIDE 35

24

High WIMP mass region (10 GeV - 1 TeV)

What is the detection strategy?

  • S2 is larger for electronic recoils than for nuclear recoils (discrimination)
  • However, rejection efficiency is about 99,5% for a 50% nuclear recoil acceptance
  • Thanks to the XYZ positioning, we can select only events happening in the bulk of the

detector (fiducialization)

  • With a larger detector, we can get the bulk region even more quiet (self-shielding)

Julien Billard (IPNL) - GIF 2016

LUX, IDM2016

slide-36
SLIDE 36

25

How do we measure the light S1 and S2?

  • High Quantum Efficiency at 175 nm (~24%)
  • ~10 kV between anode and cathode, 180 V/cm

(LXe) and 6 kV/cm (GXe) for extraction/amplification

  • When going to larger scale TPC, the challenge is to

conserve a good light collection. Need highly efficient PTFE coating

High WIMP mass region (10 GeV - 1 TeV)

XENON, IDM2016

slide-37
SLIDE 37

26

High WIMP mass region (10 GeV - 1 TeV) High WIMP mass region (10 GeV - 1 TeV)

  • XENON-1T installation:
  • Cryogenic system to cool the Xe to its liquid phase @ 165 K
  • Highly complex feedthrough for cryogenics, detector cables and high voltages
  • Purification column to remove radioactive 85Kr from Xe
  • Storage tank of 7600 kg of LXe
  • Cryostat contains the TPC filled with LXe (~3.5 ton) immersed in a gigantic water shield

Julien Billard (IPNL) - GIF 2016

XENON, UCLA Dark Matter 2016

slide-38
SLIDE 38

27

High WIMP mass region (10 GeV - 1 TeV)

Julien Billard (IPNL) - GIF 2016

XENON, UCLA Dark Matter 2016

slide-39
SLIDE 39

28

High WIMP mass region (10 GeV - 1 TeV)

Julien Billard (IPNL) - GIF 2016

XENON, UCLA Dark Matter 2016

slide-40
SLIDE 40

29

High WIMP mass region (10 GeV - 1 TeV)

E W = nγ + ne = S1 g1 + S2 g2

  • W has been measured at 13.7 eV independently, g1 and g2 are derived from Doke plot

How do we measure the true electron recoil energy ?

  • Mono-energetic sources: 83Kr, Cs, Bi and Xe activation
  • Electron recoils all start with the same excitation/ionization ratio
  • Energy-dependent recombination then moves quanta from one category to the other, 1-to-1

g1: light collection efficiency x PMT quantum efficiency ~0.1 phd/photon g2: electron extraction efficiency x single electron response ~12.1 phd/electron

LUX, IDM2016

slide-41
SLIDE 41

30

High WIMP mass region (10 GeV - 1 TeV)

How do we measure the true electron recoil energy ?

  • ER calibration and ER band definition up 18 keV

using CH3T: uniform in detector volume (needed for position correction)

  • Absolute Qy and Ly for electronic recoils by fitting

the tritium beta decay spectrum

Julien Billard (IPNL) - GIF 2016

LUX, IDM2016

slide-42
SLIDE 42

31

High WIMP mass region (10 GeV - 1 TeV)

How do we measure the true nuclear recoil energy ?

  • LUX performed the first in-situ nuclear recoil energy

calibration using a DD mono-energetic source (2.45 MeV) and their ability to recover interaction vertices

Er = E 4mχmN (mχ + mN)2 cos2 θr

LUX, IDM2016

slide-43
SLIDE 43

32

Absolute light yield light collection efficiency times PMT quantum efficiency ~0.1 phd/photon Absolute charge yield electron extraction efficiency times single electron response ~12.1 phd/electron

How do we measure the true nuclear recoil energy ?

High WIMP mass region (10 GeV - 1 TeV)

E-field E-field

Julien Billard (IPNL) - GIF 2016

LUX, IDM2016

2 keV nuclear recoil: S1 = 1 phd, S2 = 200 phd 2 keV electronic recoil: S1 = 5 phd, S2=1000 phd

slide-44
SLIDE 44

33

4 keVnr 8 keVnr 16 keVnr 32 keVnr

How does a WIMP signal look like

  • A WIMP signal would be uniformly distributed

in the detector volume

  • Plot on the right show simulations of mono-

energetic nuclear recoil

  • We see the strong anti-correlation S2/S1
  • We appreciate how bad is the energy

resolution in such experiments !!

  • Plots below show a 8 GeV (left) and 25 GeV

(right) WIMP signal in the S1/S2 plane

High WIMP mass region (10 GeV - 1 TeV)

Julien Billard (IPNL) - GIF 2016

XENON, IDM2016

slide-45
SLIDE 45

34

High WIMP mass region (10 GeV - 1 TeV)

  • Profile likelihood analysis of the new LUX result
  • Fiducial cut to benefit from self-shielding
  • Data-driven background model accounts for activated

Ar and Xe, wall events, remaining gammas and betas

  • WIMP signal model relies on robust calibration and

efficiency estimates

LUX analysis scheme

Julien Billard (IPNL) - GIF 2016

LUX, UCLA Dark Matter 2016

slide-46
SLIDE 46

35

High WIMP mass region (10 GeV - 1 TeV)

World leading limit for standard WIMP searches

Julien Billard (IPNL) - GIF 2016

LUX, UCLA Dark Matter 2016

slide-47
SLIDE 47

36

LUX:

  • 259 kg of LXe (48 cm drift)
  • 61 PMT on top and bottom
  • Purified Xenon (low Kr)
  • Water veto (muons, neutrons)
  • Sanford Lab
  • 33500 kg-days
  • leading limit 0.2 zb @ 50 GeV

PANDAX-II:

  • 500 kg of LXe (60 cm drift)
  • 55 PMT on top and bottom
  • Purified Xenon (low Kr)
  • CJPL Lab
  • 33000 kg-days
  • co-leading limit 0.2 zb @ 50 GeV

XENON-1T

  • 3500 kg of LXe (1m drift)
  • 120 PMT on top and bottom
  • Purified Xenon (low Kr)
  • LNGS (Gran Sasso)
  • cooling down
  • expect 0.01 zb @ 50 GeV (2017)

High WIMP mass region (10 GeV - 1 TeV)

Ongoing Xe dual phase TPC direct detection experiments

Julien Billard (IPNL) - GIF 2016

IDM2016

slide-48
SLIDE 48

37

  • In Kamioka underground lab
  • The detector is filled with 1 ton of LXe
  • 62% coverage with 642 low-radioactivity PMTs —> S1 scintillation only (no discrimination)
  • Strategy: maximal exploit self-shielding with strong fiducial cut (100 kg FV) + water veto
  • Results: 10-43 cm2 at 20 GeV

XMASS: single phase LXe dark matter detector

High WIMP mass region (10 GeV - 1 TeV)

XMASS, IDM2016

slide-49
SLIDE 49

38

  • It is the same scheme as for Xenon except one particularity:
  • There is two excited states that de-excite emitting scintillation light with different time

constants

  • Nuclear recoil lead to a larger singlet/triplet ratio than electronic recoil
  • Nuclear recoil pulses are faster than electronic ones —> pulse shape discrimination

How is the energy released in a Ar-based experiment?

High WIMP mass region (10 GeV - 1 TeV)

Courtesy T. Schutt

slide-50
SLIDE 50

39

  • Similar detection principle as Dual-phase Xe TPC
  • Primary scintillation (S1) and ionization (S2)
  • Cheap, easy to scale and self-shielding !
  • Can discriminate Electronic recoils from:
  • S1 Vs S2 discrimination
  • Pulse Shape Discrimination (f90)
  • Current phase: DarkSide-50
  • 153 kg of Underground Argon (UAr)
  • 50 kg fiducial mass
  • 38 PMT on bottom and top planes
  • 30-ton B-loaded doped Liquid Scintillator Veto (neutrons)
  • 1-ton Water Cherenkov Veto (muons and neutrons)
  • Installed in LNGS (Gran Sasso)

What is the detection strategy?

High WIMP mass region (10 GeV - 1 TeV)

10 m height 10 m diameter 3 m diameter

DarkSide, IDM2016

slide-51
SLIDE 51

40

What is the detection strategy?

  • Main challenge comes from 39Ar background from:
  • Naturally present in Atmospheric Argon (1 Bq/kg)
  • Supported by cosmogenic activation
  • Need to go underground and use depleted Argon (>1400 reduction)
  • Pulse Shape Discrimination is powerful and even more efficient than S1/S2

/1400

High WIMP mass region (10 GeV - 1 TeV)

Julien Billard (IPNL) - GIF 2016

DarkSide, IDM2016

slide-52
SLIDE 52

41

High WIMP mass region (10 GeV - 1 TeV)

DarkSide-50 results

  • Combining AAr and UAr runs (5900 kg-days)
  • Zero-background strategy enforces high energy threshold (~30 keVnr, 50% eff.)
  • Pulse Shape Discrimination is powerful and even more efficient than S1/S2 (not used)
  • Best Ar-based limit: 10-44 cm2 @ 100 GeV
  • Next step is DarkSide-20k (20-tons) with DAr (Distillation of UAr with 350 m tall column)

DarkSide, IDM2016

slide-53
SLIDE 53

42

  • In SNOLAB underground lab
  • The detector is filled with 3.6 ton of LAr
  • 255 low-background PMTs (32% QE, 75% coverage)
  • Resurfaced « in-situ » to remove Rn contamination
  • Immersed in 8m of water shield with 48 PMTs
  • Strategy: self-shielding, fiducialization and PSD ~10-10
  • Results expected: physics run just started (10-46 cm2 @ 100 GeV)

DEAP-3600: single phase LAr dark matter detector

High WIMP mass region (10 GeV - 1 TeV)

DEAP, IDM2016

slide-54
SLIDE 54

43

  • Results coming soon from G2 experiments: XENON1T (Xe) and DEAP (Ar)
  • G3 experiments aim at reaching the neutrino floor induced by atmospheric neutrinos
  • Limited sensitivity to light (below 10 GeV) WIMP

High WIMP mass region (10 GeV - 1 TeV)

XENON collaboration, arXiv:1512.07501

Julien Billard (IPNL) - GIF 2016

Darwin, IDM2016

slide-55
SLIDE 55

44

High WIMP mass region (10 GeV - 1 TeV)

Julien Billard (IPNL) - GIF 2016

Courtesy R. Gaitskell

slide-56
SLIDE 56
  • [/]
  • []
  • []

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C D M S I I G e ( 2 9 ) X e n

  • n

1 ( 2 1 2 )

CRESST CoGeNT (2012) CDMS Si (2013) DAMA

S I M P L E ( 2 1 2 ) Z E P L I N

  • I

I I ( 2 1 2 ) C O U P P ( 2 1 2 ) L U X ( 2 1 3 ) C D M S l i t e ( 2 1 3 ) S u p e r C D M S L T ( 2 1 4 )

8B

Neutrinos Atmospheric and DSNB Neutrinos

7Be

Neutrinos

C O H E RE NT N E U TR IN O S C A TT E RI N G COHERENT NEU TR I NO S C AT T E R I N G C O H E RE N T N EU TRI NO SCATTERING

C R E S S T ( 2 1 4 ) EDELWEISS (2011) D A M I C ( 2 1 2 )

45

  • J. Billard et al., PRD 89 (2014)

Low WIMP mass High WIMP mass

Julien Billard (IPNL) - GIF 2016

Low WIMP mass region (1 GeV - 10 GeV)

slide-57
SLIDE 57

46

Basics of direct detection

The « wish list » for a standard direct detection experiment:

  • Low and controlled backgrounds (so that they can be subtracted)
  • Discrimination between signal and background (to further reduce the background)
  • Large exposure (few events per ton-year)
  • Low energy threshold (the lower, the better, especially for low WIMP mass)

Julien Billard (IPNL) - GIF 2016

slide-58
SLIDE 58

46

Basics of direct detection

The « wish list » for a standard direct detection experiment:

  • Low and controlled backgrounds (so that they can be subtracted)
  • Discrimination between signal and background (to further reduce the background)
  • Large exposure (few events per ton-year)
  • Low energy threshold (the lower, the better, especially for low WIMP mass)

Julien Billard (IPNL) - GIF 2016

slide-59
SLIDE 59

47

Low WIMP mass region (1 GeV - 10 GeV)

Heat + scintillation Heat + ionization

Thermometer Interleaved electrodes Holding clamps Copper housing

EDELWEISS (18 mK) SuperCDMS (50 mK) Ge target CRESST (18 mK) CaWO4 target

Julien Billard (IPNL) - GIF 2016

slide-60
SLIDE 60

48

Low WIMP mass region (1 GeV - 10 GeV)

  • Cool down to 4K:
  • thanks to pre-cooling LN2 and LHe
  • Reach 1 K thanks to evaporative cooling
  • Done by pumping on LHe in 1K pot
  • Condense the He3/He4 mix
  • Reach 700 mK thanks to Joule-Thompson
  • Below 800 mK: phase separation (rich/poor)
  • 10 mK thanks to He3/He4 dilution
  • Forcing He3 through poor phase is

endothermic

  • Done by pumping on dilute phase (poor)

To reach 10 mK we need to use He3/He4 dilution refrigerator

4 K 1.4 K 700 mK 100 mK 10 mK

slide-61
SLIDE 61

49

Low WIMP mass region (1 GeV - 10 GeV)

MC ~ 10 mk Still ~ 1k 2nd stage ~ 4k 1st stage ~ 50k Cold stage ~ 0.1 k Detector

  • Standard « wet » cryostats are expensive
  • LHe cost is ~1000 euros for a week
  • Cryofree fridges are the future
  • Pulse tube to reach 4 K
  • But they vibrate !!!
  • Pulse tube have to be de-coupled mechanically
  • ~ 1 micro-g/sqrt(Hz) level achieved
  • <100 nm (RMS) !!
  • E. Olivieri, J. Billard and M. De Jesus, to be submitted

Julien Billard (IPNL) - GIF 2016

slide-62
SLIDE 62

24 selected events averaged template

50

How do we measure heat (phonons)?

Low WIMP mass region (1 GeV - 10 GeV)

Sensor

(sensitivity α)

Crystal

(Heat capacity C)

Cryostat

(Tbath)

Gleak Gsensor

∆T = E C

τrise ∼ C/Gsensor

τdecay ∼ C/Gleak

  • Basic principle:
  • Need to work at low temperature as heat capacity goes as T3
  • Need to have Gsensor >> Gleak such that sensor isothermal with crystal to maximize heat signal
  • We want Csensor << Ccrystal and largest possible α
  • The time response of the detector is fixed by the total heat capacity and the leak to the bath
  • Two types of sensors NTD (EDELWEISS) and TES (CDMS and CRESST)

∆V ∝ α∆T

∆V ∝ α∆T

slide-63
SLIDE 63

51

EDELWEISS heat sensor - NTD

Low WIMP mass region (1 GeV - 10 GeV)

∆T

∆R

R(T) = R0e

q

T0 Te

  • NTD: Neutron Transmutation Dopped germanium
  • Resistivity as a function of temperature follows Efros’ law
  • T0 depends on the neutron dose, R0 on the NTD geometry
  • At working point, NTD resistance ~1-100 MOhm
  • Current biased (α<0) with big bias resistors (Rb ~ 1 GOhm)
  • Ip has to be optimized: too big -> heats up, too small -> no gain
  • NTD readout are cheap and simple
  • Thermal measurement: they are slow (~500 ms) and limited

by the heat capacity of the crystal

  • High impedance: sensitive to microphonic noise
  • Limited to 100 eV (RMS) resolution for 800 g Ge detector

α = d ln R d ln T ∼ −10

VNT D = RNT DIp

Julien Billard (IPNL) - GIF 2016

slide-64
SLIDE 64

52

CRESST and CDMS heat sensor - TES

Low WIMP mass region (1 GeV - 10 GeV)

  • TES: Transition Edge Sensor (in Tungsten)
  • Sharp (α~100) transition supra/normal at Tc
  • Sensitive to athermal phonons (above the Al gap 340 µeV)
  • Voltage biased (α>0), readout by SQUIDs amplifier
  • Complex and expensive
  • Very sensitive to EM pick ups
  • At first order not limited by crystal heat capacity (decoupled)
  • Very fast, position sensitive, could reach few eV resolution

α = d ln R d ln T ∼ 100

Julien Billard (IPNL) - GIF 2016

slide-65
SLIDE 65

53

EDELWEISS and CDMS strategy: heat + ionization

  • In Soudan mine, but now being un-installed to

be installed in SNOLAB

  • Upgrade from CDMS II, in continuous
  • peration since spring 2012, stopped in 2016
  • 600g Germanium detectors measure ionization

and non-equilibrium phonons

  • 15 detectors = 9 kg target mass
  • In Modane Underground Laboratory
  • Upgrade from EDELWEISS II, in continuous
  • peration since summer 2014
  • 850g Germanium detectors measure ionization

and thermal phonons

  • 36 detectors = 20 kg target mass (largest array)

EDELWEISS SuperCDMS

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-66
SLIDE 66

54

WIMP WIMP E field

Charge/Phonon sensors Charge/Phonon sensors

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS and CDMS strategy: heat + ionization

Julien Billard (IPNL) - GIF 2016

slide-67
SLIDE 67

55

e- e- h+

E field

prompt phonons

Charge/Phonon sensors Charge/Phonon sensors

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS and CDMS strategy: heat + ionization

Julien Billard (IPNL) - GIF 2016

slide-68
SLIDE 68

56

e- e- h+

E field

prompt phonons

Charge/Phonon sensors Charge/Phonon sensors

Etotal = Erecoil + Eluke = Erecoil + EionΔV

1 3 eV

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS and CDMS strategy: heat + ionization

Julien Billard (IPNL) - GIF 2016

slide-69
SLIDE 69

133Ba

calibration γ

252Cf

calibration n

57

Electron recoils have a higher ionization yield than nuclear recoils

Y = Eq/Er

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS and CDMS strategy: heat + ionization

Julien Billard (IPNL) - GIF 2016

slide-70
SLIDE 70

133Ba

calibration γ

252Cf

calibration n

57

133Ba

surface events Electron recoils have a higher ionization yield than nuclear recoils Surface events have a reduced ionization yield and can mimic nuclear recoils

Y = Eq/Er

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS and CDMS strategy: heat + ionization

Julien Billard (IPNL) - GIF 2016

slide-71
SLIDE 71

58

C1 +4 V V1 -1.5 V

NTD NTD

V2 +1.5 V C2 -4 V

EDELWEISS and CDMS strategy: heat + ionization

  • The two detector technologies have interleaved bias lines to trap charges created at the

surfaces —> Fiducialization !

  • This way surface event can be rejected by asking that non of the veto electrodes see a signal

(EDELWEISS) or if there is a charge asymmetry between the top and bottom surfaces

  • Rejection power is over 105 while keeping a high NR acceptance down to a few keV
  • Only EDELWEISS has a full coverage and readouts all electrodes (best rejection)
  • BUT, SuperCDMS iZIP detectors can perform event fiducialization using phonon information

EDELWEISS FID800 SuperCDMS iZIP

Low WIMP mass region (1 GeV - 10 GeV)

slide-72
SLIDE 72

ptNF [keV] 3 4 5 6 7 8 9 10 20 30 Charge [keV]

  • 1

10 × 5 1 5

C.L. < 68% 68% < C.L. < 95% 95% < C.L. < 99% C.L. > 99% Measurement Lindhard Best fit

T2Z2

Charge model for T2Z2 ionization energy [keVee] total phonon energy [keV]

2 4 6 8 10 12 14 −2 −1 1 2 3 4 5 6 total phonon energy [keV] ionization energy [keVee]

ionization energy [keVee] total phonon energy [keV]

252Cf calibration data

Et = Er + EL Er = Et - EQ(Et)ΔV

1 3 eV

  • Fit mean ionization energy as a function
  • f total phonon energy for nuclear recoils

from 252Cf or AmBe neutron calibration

  • Most detectors consistent with or slightly

below Lindhard theory

59

charge propagation recoil phonons Luke phonons

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS and CDMS strategy: heat + ionization

slide-73
SLIDE 73

for illustration (FID837 subset)

60

No fiducial cut W I M P s i g n a l

EDELWEISS and CDMS low-energy backgrounds

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-74
SLIDE 74

61

Gamma + activation lines

  • Internal radioactivity from

shielding and cryostat

  • Cosmogenic activation lines: K/

L-shell capture from 68,71Ge,

65Zn, 68Ga

B u l k Surface

for illustration (FID837 subset)

No fiducial cut W I M P s i g n a l

EDELWEISS and CDMS low-energy backgrounds

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-75
SLIDE 75

62

210Pb “surface events”

  • betas and 206Pb nuclei from

210Pb decay chain

  • events are located on detector

face and sidewall surfaces from

222Rn contamination

210Pb 210Po 206Pb 210Bi

22.3 y 5.01 d 138.4 d

80%: β 17.0 keV 20%: β 63.5 keV 100%: β 1161.5 keV 100%: α 5.3 MeV 13.7%: conv. e 42.5 keV + Auger e 3.5%: conv. e 45.6 keV + Auger e 4.3%: γ 46.5 keV 103 keV 58.1%:

  • conv. e 30.2 keV + Auger e’s

+ 22.0%: x-rays 9.4-15.7 keV

for illustration (FID837 subset)

No fiducial cut W I M P s i g n a l

EDELWEISS and CDMS low-energy backgrounds

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-76
SLIDE 76

63

Heat only

  • Dominating background at

low-energy

  • Not seen in CDMS
  • Origin under investigation

highest priority of the EDELWEISS collaboration

for illustration (FID837 subset)

No fiducial cut W I M P s i g n a l

EDELWEISS and CDMS low-energy backgrounds

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-77
SLIDE 77

64

  • Tritium beta decay will become one of the

major background component for next generation Ge experiments

  • Thanks to its impressively low gamma

background (<0.1 DRU) and exquisite ionization energy resolution (200 eV RMS)

  • EDELWEISS-III is the first Ge experiment

to observe the intrinsic tritium beta background convincingly and measure its production rate

EDELWEISS Coll., arXiv:1607.04560

EDELWEISS and CDMS low-energy backgrounds

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-78
SLIDE 78
  • 1
  • 0.5

0.5 1

Number of events / 0.04

1 10

2

10

Data WIMP Pb

206

Sidewall Bi

210

Pb+

210

Sidewall Bi

210

Pb+

210

Face 1.3 keV line Comptons

BDT score

  • 1
  • 0.5

0.5 1 Residual

  • 40
  • 20

20 40

p-value = 0.26

65

EDELWEISS-III

  • 8 detectors with lowest thresholds:

(2.4 keVnr - 3.6 keVnr)

  • 582 kg-d of fiducial exposure
  • BDT analysis with 4 electrodes, 2 heat

sensors and heat only monitoring rate

  • No significant excess over back. expect.

Low energy analysis techniques: BDT

  • E. Armengaud, JCAP 05 (2016)
  • R. Agnese et al., PRL 112 (2014)

SuperCDMS-LT

  • 7 detectors with lowest thresholds:

(1.6 keVnr - 5 keVnr)

  • 577 kg-d of exposure
  • BDT analysis with heat and ionization

energies, radial and vertical phonon partition

  • No significant excess over back. expect.

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-79
SLIDE 79

]

2

WIMP Mass [GeV/c 4 5 6 7 8 9 10 20 30 ]

2

WIMP-nucleon cross section [cm

44 −

10

43 −

10

42 −

10

41 −

10

40 −

10

39 −

10

38 −

10

66

DAMIC DAMA/LIBRA C D M S I I

  • S

i CRESST 2015 CRESST 2012 EDELWEISS-III EDELWEISS-II S u p e r C D M S

  • L

T CDMSLITE LUX CoGeNT 2012 CRESST 2014

EDELWEISS collaboration, arXiv:1603.05120

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-80
SLIDE 80

67

  • We developed a detailed model of our heat signals that fits very well observed pulses
  • Sensitivity to ballistic phonons and presence of a parasitic heat capacity
  • Optimized sensors, to be tested this year, should reach 100 eV baseline resolution
  • HEMT R&D for ionization signal also ongoing in collaboration with SuperCDMS to

reach 100 eVee baseline resolution A. Phipps et al., J. Low Temp. Phys. (2016)

PJA PapA Pax PapB PJB Pab IpA IpB GepA GapA GapB GepB Gab Gax NTD-A NTD-B Parasitic Cryostat Crystal Tb TeA, CeA, R0A, T0A TpA, CpA Ta, Ca TpB, CpB Tx, Cx TeB, CeB, R0B, T0B

!x !B !A

Time [s] 1 1.5 2 Voltage [V]

8 −

10

7 −

10

6 −

10

5 −

10

Data: NTD-A Data: NTD-B Model: NTD-A Model: NTD-B

Ba events: FID 837 @ 18 mK - MCMC3

  • J. Billard et al., J. Low Temp. Phys. (2016)

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS and CDMS towards lower thresholds

slide-81
SLIDE 81

68

  • Use the energy deposited in ionization to boost the total heat signal
  • Loose ER/NR discrimination as heat ~ ionization
  • Working up to 100 V leading to a boost factor of ~35
  • Lowest threshold achieved of 60 eVee (300 eVnr) - achieved by both CDMS and EDELWEISS

Et = Er + EQΔV

1 3 eV

Ba calibration 356 keV line Luke-Neganov effect

EDELWEISS and CDMS towards lower thresholds

Julien Billard (IPNL) - GIF 2016

Low WIMP mass region (1 GeV - 10 GeV)

slide-82
SLIDE 82

69

  • Operated stably at 70V or 24x

amplification (only 12x due to electronics limitations) for 2 months

  • Acquired 70 kg-days
  • Ionization energy calibration with EC

lines at 1.3 keVee and 10.4 keVee

  • Must assume NR energy scale
  • 60 eVee threshold => 300 eVnr
  • No ER/NR discrimination but phonon fiducialization !

SuperCDMS - CDMSLite 2

  • R. Agnese et al., PRL 116 (2016)

EDELWEISS and CDMS towards lower thresholds

Julien Billard (IPNL) - GIF 2016

Low WIMP mass region (1 GeV - 10 GeV)

slide-83
SLIDE 83

]

2

WIMP Mass [GeV/c

1 −

10 × 7 1 2 3 4 5 6 7 8 9 10 20 ]

2

WIMP-nucleon cross section [cm

46 −

10

45 −

10

44 −

10

43 −

10

42 −

10

41 −

10

40 −

10

39 −

10

38 −

10

70

DAMIC DAMA/LIBRA C D M S I I

  • S

i CRESST 2015 CRESST 2012 EDELWEISS-III S u p e r C D M S

  • L

T CDMSLITE LUX CoGeNT 2012

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS-HV

  • ngoing

Julien Billard (IPNL) - GIF 2016

slide-84
SLIDE 84

]

2

WIMP Mass [GeV/c

  • 1

10 × 7 1 2 3 4 5 6 7 8 910 20 ]

2

WIMP-nucleon cross section [cm

  • 46

10

  • 45

10

  • 44

10

  • 43

10

  • 42

10

  • 41

10

  • 40

10

  • 39

10

  • 38

10

71

  • Q. Arnaud et al., J. Low Temp. Phys. (2016)

Neutrino background

  • J. Billard et al., Phys. Rev. D (2014)

100V, 100 eV heat, 100 eV ion 100V, 500 eV heat, 100 eV ion 8V, 500 eV heat, 100 eV ion EDW-III backgrounds, 350 kg-day Projections for 2017 Background free sensitivities

EDELWEISS and CDMS towards lower thresholds

Julien Billard (IPNL) - GIF 2016

Low WIMP mass region (1 GeV - 10 GeV)

slide-85
SLIDE 85

72

  • Going to SNOLAB and to lower temperatures (20 mK)
  • 3 Ge iZIP towers (50 kg)/ 1 Si iZIP tower (4 kg)
  • 4 HV Ge (5.6 kg)/ 2 HV Si (1.4 kg)
  • Construction planned for 2018 and data taking starts in 2020
  • S. Golwala, UCLA Dark Matter (2016)

Low WIMP mass region (1 GeV - 10 GeV)

slide-86
SLIDE 86

73

5 yrs at 80% duty cycle

  • S. Golwala, UCLA Dark Matter (2016)

Julien Billard (IPNL) - GIF 2016

Low WIMP mass region (1 GeV - 10 GeV)

slide-87
SLIDE 87

74

  • CRESST is installed in LNGS.
  • Low radioactivity environment with the

usual Pb/poly/Cu shields and muon veto

  • Phase two started in August 2015 with

new scintillating clamps —> infamous DM hint

  • 18 detector modules working at 14 mK

corresponding to a total mass of 5 kg of CaWO4 that can measure heat and light

Low WIMP mass region (1 GeV - 10 GeV)

CRESST strategy: heat + scintillation

slide-88
SLIDE 88

75

CRESST strategy: heat + scintillation

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-89
SLIDE 89

76

CRESST strategy: heat + scintillation

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-90
SLIDE 90

77

Light yield calibration

  • To define the WIMP acceptance band, the

CRESST collaboration did a detailed characterization of their detector’s response to neutron induced nuclear recoils

  • Information power is very low, large

systematics at low energy

  • But, scintillation is only a few percent so not

really needed to recover Er

Coincidences only for W

  • R. Strauss et al., Eur.Phys.J. C74 (2014) 2957

Low WIMP mass region (1 GeV - 10 GeV)

slide-91
SLIDE 91

78

  • Total of 52 kg-days of exposure with a single

detector module (LISE) chosen for its lower energy threshold (307 eV).

  • Acceptance band defined as everything

below the median of the O recoils and up to W endpoint.

  • Strong Fe line as a source was left on the

module accidentally, but doesn’t hurt the limit too much

  • The limit has been derived thanks to optimal

interval method, i.e. no background subtraction but signal-to-noise optimization

CRESST-II analysis

Low WIMP mass region (1 GeV - 10 GeV)

  • G. Angloher, Eur.Phys.J. C76 (2016) 25

Julien Billard (IPNL) - GIF 2016

slide-92
SLIDE 92

]

2

WIMP Mass [GeV/c

1 −

10 × 7 1 2 3 4 5 6 7 8 9 10 20 ]

2

WIMP-nucleon cross section [cm

46 −

10

45 −

10

44 −

10

43 −

10

42 −

10

41 −

10

40 −

10

39 −

10

38 −

10

79

DAMIC DAMA/LIBRA C D M S I I

  • S

i CRESST 2015 CRESST 2012 EDELWEISS-III S u p e r C D M S

  • L

T CDMSLITE LUX CoGeNT 2012

Low WIMP mass region (1 GeV - 10 GeV)

Julien Billard (IPNL) - GIF 2016

slide-93
SLIDE 93

80

Low WIMP mass region (1 GeV - 10 GeV)

  • The CRESST collaboration is now fully dedicated to low-mass WIMPs
  • They are lowering their threshold by reducing the size of the crystals 250 g -> 24 g such that

the threshold has gone from 500 eV to 100 eV as the athermal phonon collection efficiency gets larger and better match to the sensor bandwidth

  • Reduce crystal contamination from radio active isotopes by ~ 10
  • Actively reject events from the sticks: iStick
  • New run ongoing with a target exposure of 50 kg-days with 10 modules

Next step?

CRESST collaboration, IDM 2016

Julien Billard (IPNL) - GIF 2016

slide-94
SLIDE 94

Low WIMP mass region (1 GeV - 10 GeV)

EDELWEISS-III results 2016 EDW-III goals 2017 35 ton-days

CRESST-3 phase 1 CRESST-3 phase 2 SuperCDMS@SNOLAB

Julien Billard (IPNL) - GIF 2016