cosine-100 - indico...• culmination of r&d program with alpha spectra ... • separate noise...

COSINE-100Reina Maruyama Yale University

LLWI 2017 February 19 - 25, 2017

Lake Louise 2017

LLWI 2017Reina Maruyama | Yale University

Direct evidence for dark matter particles?The DAMA signal seems incompatible with other experiments

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2013

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CURRENTLIMITS

SuperCDMS

LUX

SuperCDMS

CDMSlite

CRESST

Spin-independent

Excluded

Atmospheric and supernova neutrinos

sola

r 8 B

neu

trin

os

DARWIN

DAMA signal Spin-independent interactions Standard halo model

Excluded

2

Gondolo, IDM 2016

Current status of “Direct” WIMP Searches

ANAISDM-Ice + KIMS

Canfranc

Yangyang

Boulby

113 kg array

Current & Planned NaI(Tl) Experiments

106 kg at Yangyang

Gran Sasso + Australia COSINE-100

SABRE


COSINE-100 Dark Matter Experiment

• 107 kg of NaI(Tl) detectors, former DM-Ice and KIMS collaborations• 14 institutions, ~50 members• Located at Yangyang Underground Laboratory (Y2L), South Korea,

~2100 m.w.e overburden• Taking data since September 2016.

4

http://cosine.yale.edu

http://cosine.yale.edu

5

NaI-001C1

NaI-002C2

NaI-007C3

AS3C4

AS1C5

NaI-011C6

NaI-012C7

AS2C8

COSINE-100

Taking data since Sep. 2016


COSINE-100 NaI(Tl) Crystals• 8 crystals, total 106 kg• Culmination of R&D program with Alpha

Spectra• 40K below DAMA, 210Po very close• Average light yield ~15 p.e./keV • Challenge: putting it all together• Total Background: 2 - 4 x DAMA’s avg.

6

PreliminaryCOSINE-100


COSINE-100 Shielding

7

Lead Shielding (20 cm) Cu Box (3 cm)

NaI(Tl) Crystals

Filled with 2000 L Liquid Scintillator

40 cm

7

Plastic Scintillators


COSINE-100 Construction

88

Dec. 2015 Jan. 2016 Feb. 2016

Mar. 2016 Apr. 2016

May. 2016 Sep. 2016Jun. 2016


Crystal PMT Waveforms

9

• The same events read in two channels: Anode and Dynode

- Anode signal with waveform sensitivity at single-photon level: Primary channel for dark matter search

- Dynode signal for high energy events: helps in understanding better the internal backgrounds in the crystals

Time Bin (2ns)

Anode Waveform (0-120 keV)

Dynode Waveform (50-10,000 keV)

Time Bin (2ns)

ADC count ADC

count


Event Selection: Fast Event Rejection

10

Slow charge fraction (X1)

Fast charge fraction (X2)

Time (ns)

Slow charge fraction (X1)

Fast charge fraction (X2)

Time (ns)

• Separate noise via charge ratio of rising edge vs. falling edge

Preliminary

Noise

Signal


Event Selection: Asymmetry & Charge/Peak

11

• Additional noise reduction cuts have been developed:

- Charge asymmetry between 2 PMTs in each crystal

- Charge/peak: Average charge per SPE

PMT Noise

signal

Average charge per SPE

11


Liquid Scintillator Tagging for 40K

12

• 40K emits 1460 keV γ + 3 keV Auger electron

• Tagging 1460 keV events with LS enables to veto 3 keV background events

γ (1460 keV)

Liquid Scintillator

40Ke- (3 keV)

+ Data (vetoed) – Fit – Subtracted 40K

Preliminary


Low Energy Spectrum

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• 10 days of data, preliminary set of event selection applied

• Variation in background levels, 2 to 4 cnts/keV/kg/day in region of interest

• 210Pb (T1/2 = 22 years) peak visible

• 210Pb on surface dominate the backgrounds in ROI

• 125I (T1/2 = 59 days) still present in newer crystals

ROI

Crystal 1

Preliminary 210Pb

ROI

Crystal 6

Preliminary

125I

210Pb


Energy Spectrum in the ROI

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Single Hit (After vetoed)Vetoed events

Single Hit (After vetoed)Vetoed events

Crystal 7

Crystal 4


NaI Crystal Simulation

15

• Geant4 simulation

• Reproduces data well, cosmogenics etc. depends on crystal

• Surface 210Pb is suspected to be the dominant background, followed by 40K internal to crystal

Simulation within R&D array (C3) Detector Geometry at COSINE-100

DataTotal MCSurface 210Pb

40K

Preliminary


• COSINE-100= DM-Ice + KIMS • Physics run has started on September 2016 • COSINE-100 = 8 crystals, 106 kg, 2000 liters of LAB-based liquid

scintillator veto • Continued R&D for higher purity crystals • ANAIS starting soon, SABRE R&D ongoing • Projected data taking for 2 years. Stay tuned!

Summary

16WIMP Mass (GeV)1 10 210 310

)2SI

WIM

P-nu

cleo

n cr

oss

sect

ion

(cm

-4210

-4110

-4010

-3910

-3810

-3710)σ, 5σDAMA allowed region (90%C.L., 3

COSINE, 2 years of data2-20 keV, Median Sensitivty (90%C.L.)1-20 keV, Median Sensitivity (90%C.L.)

σ 1± σ 2±

COSINE-100 COSINE-100 + ANAIS

cosine-100 - indico...• culmination of r&d program with alpha spectra ... • separate noise...

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