Dark Matter 1-ton Era Cristiano Galbiati Princeton University - - PowerPoint PPT Presentation

Dark Matter 1-ton Era

Cristiano Galbiati Princeton University

Milan Università degli Studi June 30, 2014

200 150 100 50 5 10 15 20 NGC 6530 dark halo disk

vc (km/s)

r (kpc) gas

Fuchs astro-ph/9812048 WMAP 2006

Has gravitational interactions Is long lived Is cold Is not baryonic Feng

e,γ χ,n Attisha

1 10 100 1000 104 1050 1049 1048 1047 1046 1045 1044 1043 1042 1041 1040 1039 1014 1013 1012 1011 1010 109 108 107 106 105 104 103 WIMP Mass GeVc2 WIMPnucleon cross section cm2 WIMPnucleon cross section pb

(Green&ovals)&Asymmetric&DM&& (Violet&oval)&Magne7c&DM& (Blue&oval)&Extra&dimensions&& (Red&circle)&SUSY&MSSM& &&&&&MSSM:&Pure&Higgsino&& &&&&&MSSM:&A&funnel& &&&&&MSSM:&BinoEstop&coannihila7on& &&&&&MSSM:&BinoEsquark&coannihila7on& &

8B

Neutrinos Atmospheric and DSNB Neutrinos C D M S I I G e ( 2 9 ) X e n

• n

1 ( 2 1 2 )

CRESST CoGeNT (2012) CDMS Si (2013)

EDELWEISS (2011)

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 )

SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) CDMS-II Ge Low Threshold (2011)

SuperCDMS Soudan X e n

• n

1 T L Z L U X ( 2 1 3 ) D a r k S i d e G 2 D a r k S i d e 5 DEAP3600 P I C O 2 5

• C

F 3 I PICO250-C3F8 SNOLAB SuperCDMS

7Be

Neutrinos

N EU T RIN O C OH ER EN T S CA T TE R ING N E UT R I N O C O HE REN T S C A T T E R IN G

CDMSlite (2013) SuperCDMS SNOLAB

Z-mediated scattering H

• m

e d i a t e d s c a t t e r i n g Figueroa-Feliciano

What Techniques

• Si/Ge Bolometers
• NaI Scintillating Crystals
• Bubble Chambers
• Noble (Xe/Ar) Scintillators
• Noble (Xe/Ar) Scintillating TPC

Remember!

• It only makes sense if you can guarantee background-free condition

PICO Bubble Chambers and Update on COUPP60

Hugh Lippincott, Fermilab for the PICO Collaboration UCLA DM 2014

1

Why bubble chambers?

• By choosing superheat parameters appropriately

(temperature and pressure), bubble chambers are blind to electronic recoils (10-10 or better)

• To form a bubble requires two things
• Enough energy
• Enough energy density - length scale must be

comparable to the critical bubble size

6

• Electronic recoils never cross the second threshold!

COUPP60

• Collected >3000 kg-days of dark matter search data between 9

and 25 keV threshold

• Good live fraction > 80% (including >95% over the last month)
• No darkening

22

• Analysis still under development
• Good news: Zero multiple bubbles, no
• neutrons. Limit on neutron rate is factor 7

below observed rate in COUPP4

• Bad news: Population of events that sound like

nuclear recoils but are clearly not WIMPs

• Silver lining: statistics - we can actually study

them in detail

• Indications confirm a slightly different

acoustic distribution and similar timing and spatial correlations to COUPP4 background for at least some fraction of events

COUPP60 - the data

27

XMASS,&&

present&and&future&development&

S.&Moriyama& Kamioka&Observatory,& Ins=tute&for&Cosmic&Ray&Research,& The&University&of&Tokyo& 28th&Feb.&2014,&Dark&MaKer&2014,&UCLA&

&

&XMASS:&LXe&single&& &&&&&&&phase&detector&

• Many&interes=ng&physics&targets,&including&EM&interac=ons&

– Dark&maKer:&elas=c,&inelas=c&129Xe,&superQWIMPs,&ALP,&HP,&…& – Solar&axions,&2νDEC,&SN,&and&other&unexpected&signal&

• Intrinsic&BG&of&XMASS&I:&O(10Q4)/kg/keVee/d&@40keV&

dominated&by&214Pb,&w/o&part.&ID&(arXiv:&1401.4737)&

• Larger&size&is&advantageous.&Surf.&BG,&Kr,&&&Rn&

important.&

2&

&Key&component&&&& &&&to&see&the&surface&

• One&of&the&most&simple&and&straighforward&way&

to&see&the&surface&events&is&the&use&of&PMTs&with& a&convex,&dome&shape&photocathode.&

• Similar&shape&can&be&seen&in&many&examples.

From PMT handbook (HPK)

4&

&Iden=fica=on& &&&performance&

• 3&PMTs&accept&40Q50%&of&total&
• One&example&of&surface&ID:&

&&&3&PMTs&>&10%&of&total&PE&

• Assume&surface&RI&8mBq&210Pb,&

&&&107&events&~42y.&In&2Q2.5keVee& &&&&0.1&events/y&w/o&dead&tube& &&&&0.3&events/y&w/&15&dead&tubes&

• DM&signal&efficiency&&~&20%&of&all&volume.&

Surface events can be identified and rejected effectively.

6&

BG generated position Hit position (photocathode) 2-2.5keVee 42yrs equiv. surface

&Beyond&the&surface:& &&&solar&ppν,&Kr&and&Rn&

• Internal&background,&future&goal&<10Q5/kg/keVee/d&

– e&scat.&by&solar&pp&ν&~&10Q5/kg/keVee/d&!&irreducible& – 212Pb,&<0.3µBq/kg&~&10Q5/kg/keVee/d=dru&!&1/10& – 85Kr&(Qβ=687keV,&τ1/2=11yr),&1ppt&~10Q5dru&!&1/10& – 214Pb,&10mBq/kg&~&10Q4dru&!&<1/10&

• γ&ray&and&neutron&contribu=on&will&be&evaluated.&
• Predic=on&of&these&background&are&accurate&and&&

will&be&taken&into&account&in&analyses&to&search&for&& DM&signal.&<~10Q46cm2&would&be&searched&for.&

7&

XMASS&in&future

• XMASS-I

DM 100kg FV (800kg) 0.8mφ, 642 PMTs 2007- To discover DM

XMASS-II

DM, solar, ββ& 10ton FV Detailed study of DM pp solar ν& ββ ~30meV(IH)

XMASS-1.5

DM 1ton FV (5ton) 1.5mφ, ~1000 PMTs Requesting budget DM, pp solar ν ~10-46cm2 Annual/spectral info.

10&

Dark-matter Experiment using Argon Pulse Shape Discrimination

Fabrice Retière on behalf of the DEAP collaboration

DEAP-3600 concept

Liquid Argon Ball for dark matter search

• 1 ton Ar fiducial

85 cm radius

• 255 PMTs

No charge readout

• Being installed

Start of operation early 2014

3.6 tonnes of liquid Argon

• Enclosed in 85 cm radius

acrylic ball

• 1 tonne fiducial

Excluding surface events

Scintillation only

• Aka single phase
• Light viewed by 255

photo-multiplier tubes

Feb 28th, 2014 2

Neutron background mitigation

Sited at SNOLAB

• 6000 meter water

equivalent

Inside a water tank ~50cm of light guide acrylic and filler blocks Ultra-low radioactivity acrylic

Feb 28th, 2014 3

TPB wavelength shifter Acrylic vessel Filler block Acrylic light guide PMT Water Liquid Argon

Pulse shape discrimination concept

Feb 28th, 2014 7

Nuclear Recoil Tagged AmBe source Background (

Projected backgrounds

Background Rate/count Mitigation Neutron In 1t LAr < 2 pBq/kg < 0.06 count/year Shielding: 6000 mwe (SNOLAB), Active water shield, light guides and filler blocks Material selection & In 1t LAr < 2 pBq/kg < 0.06 count/year Pulse shape discrimination Material selection (for ) Radon In 1t LAr < 1.4 nBq/kg < 44 count/year* Material selection, SAES getter, cold charcoal radon trap * High energy events, not in ROI Surface In 1t LAr < 0.2 mBq/m2 < 0.6 count/year Material selection (acrylic), sanding of AV (1mm removal), fiducialization.

Feb 28th, 2014 11

Total of <0.6 events in ROI in 3 years for a spin-independent WIMP-nucleon cross section sensitivity of 10-46 cm2 at 100GeV. Assuming 8PE per keV

Challenge for Scintillating Detectors

Nuclear Instruments and Methods in Physics Research A 568 (2006) 700–709

Time and space reconstruction in optical, non-imaging, scintillator-based particle detectors

• C. Galbiati, K. McCarty

aPhysics Department, Princeton University, Princeton, NJ 08544, USA

Received 22 April 2005; received in revised form 25 July 2006; accepted 29 July 2006 Available online 24 August 2006

ARTICLE IN PRESS

www.elsevier.com/locate/nima

Challenge for Noble Scintillators

t.o.f.: ∂x = cσ n 3 N diffusive propagation: ∂x = R 2 3 N

Scintillating Noble TPCs

∂z ≈1 mm ∂ x,y

( ) ≈1− 3 cm

LU

• T. Shutt - NygrenFest, May 3, 2014

How a two-phase Xe TPC is a perfect way to look for WIMPs

• T. Shutt

Case Western Reserve University

1

1

LU

• T. Shutt - NygrenFest, May 3, 2014

Dual phase Time Projection Chamber

• Liquid Xe - large

signal, strong shielding of external backgrounds

• 3D event position
• Charge (S2) / light (S1)

distinguishes electron recoil backgrounds

• Single electrons and

photons

7

LUX

7

LU

• T. Shutt - NygrenFest, May 3, 2014

Self-shielding in liquid xenon

17

• MeV gammas and

neutrons: λ ~10 cm

P(L) ∼ = L λ e− L

λ

PMT

Single, low-energy Compton scatter

300 kg LUX

fiducial

7 Ton LZ

pp solar ν

17

100 200 300 400 500 600 350 300 250 200 150 100 50 radius2 (cm2) drift time (µs)

cathode grid gate grid wall face wall corner

10 20 30 40 50 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 log10(S2b/S1) x,y,z corrected S1 x,y,z corrected (phe)

3 6 9 12 15 18 21 24 27 30 keVnr 1.3 1.8 3.5 4.6 5.9 7.1

keVee

What is a DRU?

• DRU = Dark matter Rate Unit
• 1 DRU = 1 count / [keVee × kg × day]
• Next generation Xe experiments need to contain their background

within a few μDRU

LU

• T. Shutt - NygrenFest, May 3, 2014

Future directions

• LZ is not quite at neutrino limit
• Background rejection might or might not be sufficient to

defeat pp solar neutrino background

• Get rid of PMT radioactivity

— Would enable simultaneous ßß-decay and DM search

• Please buy LED light bulbs

32

32

Future Directions of Xe Scintillating TPC

• XENON-1t at LNGS (2016?)
• LZ at Sanford Lab (?)
• XENON-nt at LNGS (?)

DarkSide A scalable, zero-background technology

• Pulse shape of scintillation provides powerful discrimination for NR vs. EM

events: Rejection factor ≥108 for >60 photoelectrons: proposed by Boulay & Hime, AstropartPhys 25, 176 (2006) demonstrated by WARP AstropartPhys 28, 495 (2008)

• Ionization:scintillation ratio a semi-independent discrimination mechanism:
• Great spatial resolution from ionization drift localizes events, allowing rejection
• f multiple interactions, "wall events", etc.
• Underground argon

39Ar abatement factor ≥150

Beta/Gamma Nuclear Recoil

Argon Scintillating TPC

S1 [PE] 60 80 100 120 140 160 180 200 F90 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

total_s1_corr_f90_after_lsv_cuts_hist

Entries 2.119474e+07 Mean x 131.2 Mean y 0.3062 RMS x 40.52 RMS y 0.05257

100 200 300 400 500 600 700

total_s1_corr_f90_after_lsv_cuts_hist

Entries 2.119474e+07 Mean x 131.2 Mean y 0.3062 RMS x 40.52 RMS y 0.05257

50%

280 kg×day Exposure with Atmospheric Argon

65% 80% 90%

70 PE~35 keVr 125 PE~57 keVr

DarkSide-50 Prospects

• Good news: 4,365 kg×day exposure (active: before fiducialization) collected

as of May 24, 2014

• Equivalent to 50 years of 39Ar decays in DarkSide-50 with underground argon
• Equivalent to 1/2 year of 39Ar decays in DarkSide-G2 with underground argon
• For comparison:
• LUX: 10,030 kg×day (85 days × 118 kg, Phys. Rev. Lett. 112, 091303

(2014))

• XENON-100: 7,650 kg×day (225 days × 34 kg, Phys. Rev. Lett. 109,

181301 (2012))

• CDMS+Edelweiss: 614 kg×day (Phys. Rev. D 84, 011102(R) (2011))

[GeV]

• M

2

10 10

3

10 ]

2

[cm

• 45

10

• 44

10

• 43

10

• 42

10

Experimental limits DarkSide50 - 3 y DarkSide50 - 2.6 y Xenon100 LUX pMSSM (post LHC)

DarkSide-50 Expected Sensitivity

Threshold 35 keVr! Fiducial mass 44.1 kg (95%)! LY=8.0 PE/keVee @ null field! NR Quenching from SCENE! F90 acceptance energy dependent

total_s1_corr [PE] 80 100 120 140 160 180 200 total_f90 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Entries 2.454012e+09 Mean x 141 Mean y 0.303 RMS x 34.93 RMS y 0.05026

• 1

10 1 10

2

10

3

10

4

10

5

10

Entries 2.454012e+09 Mean x 141 Mean y 0.303 RMS x 34.93 RMS y 0.05026

50% 65% 80% 90%

G2 Exposure (5 Years)

100 PE~47 keVr 120 PE~55 keVr

Full G2 statistics model based on DS-50 data

[GeV]

• M

2

10 10

3

10

4

10 ]

2

[cm

• 47

10

• 46

10

• 45

10

• 44

10

• 43

10

• 42

10

Experimental limits DarkSide50 - 3 y (th 35) DarkSideG2 - 5 y (th 47) DarkSideG2 - 5 y (th 55)

DarkSide-G2 Expected Sensitivity

24

Detector Element Electron Recoil Radiogenic Neutron Backgrounds Recoil Backgrounds After Cuts After Cuts and PSD Raw After Cuts and PSD

39Ar (<6.5 mBq/kg)

4.2⇥108

<0.1

– – R11065-G2 PMT’s 2.5⇥106

<0.01

280 0.05 Cryostat & Insulation 8.2⇥106

<0.01

580 0.05

222Rn and Daughters <1.7⇥105

⌧0.01

– – pp Solar Neutrinos 2.7⇥103

⌧0.01

– – Total

<0.1

0.1 TABLE II: A summary of the expected nuclear- and electron-recoil backgrounds depositing 55–240 keVr in a 18 tonne-year exposure of DarkSide-G2. We assume 39Ar at our measured upper limit [28]. For PMT’s, we use the expected background in the R11065-G2’s, based on measurements reported by Hamamatsu and

• ur ongoing R&D. For the cryostat, we use detailed measurements of the steel used for the DarkSide-50
• cryostat. “After cuts” includes fiducial, energy, and multi-hit cuts. “Raw” is the total number of emitted

neutrons in 5 years.

25

Detector XENON100 LUX DEAP-1 DarkSide-50

222Rn Activity .21 µBq/kg [67] (15±2) µBq/kg [68] (16–26) µBq/kg [69] <0.85 µBq/kg

TABLE III: 222Rn activity in DarkSide-50, compared to similar xenon- and argon-based detectors. The DarkSide-50 analysis was performed with the delayed coincidence method first introduced for the CTF of Borexino [31] and then extended to noble liquid TPCs as described in [67–69]. Present sensitivity to 222Rn is limited by statistics, hence we quote the 90% C.L. upper limit.

Control of background from 222Rn will be among the decisive factors of success for G2 and G3 detectors, due to β/γ’s decays as well as α’s decays part of the 222Rn

• chain. LXe G2 detectors will require 0.1 μBq/kg or 0.6 mBq total (see Shutt at

Snowmass Cosmic Frontier), two orders of magnitude below current limits. DarkSide- G2 could tolerate much higher background due to better rejection.

!

DarkSide-50 demonstrated the capability of argon detectors to reach very low levels

• f contamination from 222Rn. The lower temperature of LAr and the “all cold” design
• f the DarkSide-50 cryostat results in a very low effective emanation, already meeting

the requirements for DarkSide-G2 and for LXe G2. It will not be as easy for the xenon based detectors due to the much higher LXe temperature.

Counts/10 p.e.

Liquid Argon TPC & Cryostat

4-m Diameter Liquid Scintillator Neutron Veto

10-m high 11-m Diameter Water Tank

Class 100 Clean Room Radon < 5mBq/m3

Outer Shell Notes

• 1. Total LAr: 5T
• 2. Active LAr: 3.3T
• 3. Fiducial LAr: 2.8T
• 4. 3" PMTs: 558 ea.

Fused Silica Plate ector Cu Field Cage

• n Insulator

Fused Silica Plate w/ Gas Pocket 279 ea. 3"PMTs provide 48% cathold coverage two places, top & bottom Inner Shell

7Li(p,n) on thin LiF target to generate low energy, pulsed, monochromatic neutron beam Triple coincidence between pulse proton beam, LAr TPC, liquid scintillator detectors for detection of scattered neutrons SCENE

SCENE Recoil Energy [keV] 10 20 30 40 50 60 Kr(0V/cm)

83m

S1 Relative to 0.14 0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0 V/cm 100 V/cm 200 V/cm 300 V/cm 1000 V/cm

SCENE Recoil energy [keV] 10 20 30 40 50 60 S2 yield [PE/keV] 2 4 6 8 10 12 14 16 50 V/cm 100 V/cm 200 V/cm 300 V/cm 500 V/cm /keV]

• S2 yield [e

1 2 3 4 5

SCENE Drift electric field [V/cm] 200 400 600 800 1000 S1 yield relative to 0 field 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 57.2 keV

d

ε Parallel to

d

ε Perpendicular to

NEST

Summary

• Bubble Chambers
• Mystery background, speculation on ultra-fine particulate. If issue resolved, modular

construction of ton-scale detectors potentially very cheap. Very limited spectral sensitivity.

• Noble (Xe/Ar) Scintillators
• Strong potential limited by intrinsically small position resolution.
• Xe Scintillating TPC
• Kills external background. Issues with internal background. Very significant cost of

target ($5M/ton, need 20 tons for G3).

• Ar Scintillating TPC
• Kills external and internal background other than 39Ar. Statistical rejection of 39Ar for G2

and G3 detectors still to be established. Funding for plant for extraction of underground argon at 100 kg/day rate received. Directionality?

The End

Like the jelly beans in this jar, the Universe is mostly dark: 96 percent consists of dark energy (about 70%) and dark matter (about 26%). Only about four percent (the same proportion as the lightly colored jelly beans) of the Universe - including the stars, planets and us - is made

• f familiar atomic matter.