Dark matter annual modulation withANAIS-112: three years results

María Martínez, ARAID & U. Zaragoza
On behalf of the ANAIS teamLomonosov Conference, August 19-25 2021

OUTLINE• Intro• ANAIS-112 set-up• Detector performance• 3 years results on annual modualation• Projected sensitivity• Conclusions

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 20212

DM annual modulation & DAMA/LIBRA
positive signal
DAMA/NaI & DAMA/LIBRA (LNGS) [since 1995]

DAMA clearly sees an annual modulationcompatible with DM at more than 12𝜎𝜎other very sensitive experiments do not seethe signal, but the comparison is model
dependent-> a model independet confirmation isneeded using the same target
M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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Experimental situation

R. Bernabei
talk

F. Wagner
talk

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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ANAIS-112 experiment
M. Martinez. F. ARAID & U. Zaragoza

Berkeley Lab, July 2, 2021

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ANAIS-112
Annual Modulation with NaI Scintillators
J. Amaré, I. Coarasa, S. Cebrián, D. Cintas, E. García, M. Martínez, M.A. Oliván,
Y. Ortigoza, A. Ortiz de Solórzano, J. Puimedón, A. Salinas, M.L. Sarsa

GOAL:
Independent confirmation of
DAMA/LIBRA modulation signal withthe same target and technique(but different experimental approachand environmental conditions)

WHERE:At Canfranc Underground Laboratory,@ SPAIN (under 2450 m.w.e.)
ANAIS

THE DETECTOR:
3x3 matrix of 12.5 kg NaI(Tl) cylindricalmodules = 112.5 kg of active mass

taking data since August 2017
M. Martinez. F. ARAID & U. Zaragoza

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ANAIS-112: experimental setup• 9 NaI(Tl) cylindricalcrystals (12.5 kg each) in3x3 matrix• Ultrapure NaI powder(Alpha Spectra Inc)
• Each coupled to two
Hamamatsu R12669SEL2
PMT (QE ∼40%)
Anti-Rn box

Muon veto: 16 plastic
scintillators
M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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ANAIS-112: Low energy calibration
Detectors equipped with a Mylar window!
Radon-free system for low energy calibration:• 109Cd sources on flexible wires (radon-free)• Energies: 11.9, 22.6 and 88.0 keV• Simultaneous calibration of the nine modules• Performed every two weeks

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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ANAIS-112: Data acquisition system• Individual PMT signals digitized and fully
processed (14 bits, 2 GS/s)

1 keV• Trigger at phe level for each PMT signal• AND coincidence in 200 ns window• Redundant energy conversion by QDC• Trigger in OR mode among modules• Electronics at air-conditioned-room to decouple
from temperature fluctuations• Muon detection system: tag every muon event tooffline processing

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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ANAIS-112: Slow control• Monitoring environmental parameters since the start of DM run– Monitoring:
Rn content, humidity, pressure, different temperatures, N2 flux, PMT HV, muon rate, …
Data saved every few minutes and alarm messages implemented– Stability checks:
gain, trigger rate, …

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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DETECTOR PERFORMANCE

Amaré et al., Eur. Phys. J. C (2019) 79:228, 1812.01472
M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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Detector Response: duty cycle & stability•

Excellent duty cycle

Live time
94.4%

Down time(calibrations)
2.7%
Dead time
2.9%

100% live time

ANAIS
accumulated
exposure vstime• Good total rate and gain stability
Evolution of 109Cd lines from calibrations
along the whole data-taking (∼ 3 year)
show good stability except for D4 & D5
(HV changed after first year)
Thanks to the periodic calibration we cancorrect the small (few percent) gainvariations
M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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Detector response: light yield & threshold• Excellent light collection ~ 15 photoelectrons / keV (2x DAMA ph1)

• Effectively triggering below 1 keVee checked with internal contaminants 22Na, 40K
bulk 22Na and 40K events
identified by coincidenceswith high energy gammas

M. Martinez. F. ARAID & U. Zaragoza

0.87 keV

3.2 keV

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Blinded analysis
unblinded data (30 days)

ANALYSIS STRATEGY• Multiplicity-1 events in the RoI (1-6 keV)
blinded• We use multiplicity-2 events in the RoIand calibration events to tune thefiltering algorithms and calculate thecut efficiencies• We unblind ∼30 days randomly
distributed along the first year forbackground assessment

Bkg in the ROI dominated bynon-bulk scintillation events!

Amaré et al., Eur. Phys. J. C (2019) 79:228, 1812.01472
M. Martinez. F. ARAID & U. ZaragozaLomonosov Conference, August 19-25 2021

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Event selection & efficiency
TOTAL EFFICIENCY

Procedure fixed before unblinding
CUTS
1. Pulse shape cut to remove
pulses not compatible withNaI(Tl) scintillation constant

2. We remove asymmetric
events (<2 keVee) with origin
in the PMTEFFICIENCY-CORRECTED BACKGROUND
30 daysunblinded data

3. Remove 1 s after a muonpassage
4. Multiplicity > 1 (Reject events

that deposit energy simultaneously inmore than one crystal)

Amaré et al., Eur. Phys. J. C (2019) 79:228, 1812.01472
M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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Stability check with control populations
40K (𝑇𝑇91/2 = 1.28 × 10 𝑦𝑦)[2-5] keV rate in coincidencewith HE gamma compatible withconstant

22Na (𝑇𝑇1/2 = 2.6 𝑦𝑦)[0-2] keV rate in coincidencewith HE gamma compatible with
22Na decay(exponential decay with𝜏𝜏 = 1481 ± 65 d)
M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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Background model
Amaré et al., Eur. Phys. J. C (2019) 79:228, 1812.01472
Geat4 MC simulation including:• activity from external components measured wiht HPGe
• internal and cosmogenic activity directly assessed from data.
At very low energy (<20 keV), main contribution to backgroundfrom internal contamination:• 40K and 22Na (T1/2 = 2.6 y) peaks• 210Pb (bulk+surface) (T1/2 = 22.3 y)• 3H (T1/2 = 12.3 y)Very good agreement with data in
the ROI except between 1-2 keV

Cosmogenic isotopes (3H, 22Na, …) and 210Pb are decaying→ Our MC model reproduce satisfactorily the timeevolution for non-blinded populations
Bkg model

Bkg model

DAMA/LIBRA

Universe 4, 116 (2018),
1805.10486
M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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RESULTS ON ANNUAL MODULATION

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Lomonosov Conference, August 19-25 2021

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Analysis strategy

Phys. Rev. D 103,102005 (2021)

Focus on model independent analysis searching from modulation• In order to better compare with DAMA/LIBRA results• use the same energy regions ([1-6] keV, [2-6] keV)
• fix period 1 year and phase to June 2nd• ChiSquare minimization: 𝜒𝜒 2 = ∑ 𝑛𝑛𝑖𝑖 − 𝜇𝜇𝑖𝑖 2 /𝜎𝜎𝑖𝑖2
where the expected number of events depends on the bkg model (𝜙𝜙𝑏𝑏𝑏𝑏𝑏𝑏 (𝑡𝑡𝑖𝑖 )):𝜇𝜇𝑖𝑖 = 𝑅𝑅0 𝝓𝝓𝒃𝒃𝒃𝒃𝒃𝒃 𝒕𝒕𝒊𝒊 + 𝑺𝑺𝒎𝒎 cos 𝜔𝜔 𝑡𝑡𝑖𝑖 − 𝑡𝑡0

𝑀𝑀Δ𝐸𝐸Δ𝑡𝑡

We need a model for the decreasing bkg!

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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Analysis strategy

Phys. Rev. D 103,102005 (2021)

Focus on model independent analysis searching from modulation• In order to better compare with DAMA/LIBRA results• use the same energy regions ([1-6] keV, [2-6] keV)
• fix period 1 year and phase to June 2nd• ChiSquare minimization: 𝜒𝜒 2 = ∑ 𝑛𝑛𝑖𝑖 − 𝜇𝜇𝑖𝑖 2 /𝜎𝜎𝑖𝑖2
where the expected number of events depends on the bkg model (𝜙𝜙𝑏𝑏𝑏𝑏𝑏𝑏 (𝑡𝑡𝑖𝑖 )):𝜇𝜇𝑖𝑖 = 𝑅𝑅0 𝝓𝝓𝒃𝒃𝒃𝒃𝒃𝒃 𝒕𝒕𝒊𝒊 + 𝑺𝑺𝒎𝒎 cos 𝜔𝜔 𝑡𝑡𝑖𝑖 − 𝑡𝑡0𝑡𝑡𝑖𝑖
𝜙𝜙𝑏𝑏𝑏𝑏𝑏𝑏 𝑡𝑡𝑖𝑖 = 1 + 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 −𝜏𝜏Free parameters: 𝑅𝑅𝑜𝑜 , 𝑓𝑓, 𝜏𝜏 + 𝑆𝑆𝑚𝑚

MODEL 2: Use MC simulation
ϕMCbkg (kpd/kg/keV)

MODEL 1: assume exponential decay

𝑀𝑀Δ𝐸𝐸Δ𝑡𝑡

𝑀𝑀𝑀𝑀
𝜙𝜙𝑏𝑏𝑏𝑏𝑏𝑏 𝑡𝑡𝑖𝑖 = 1 + 𝑓𝑓𝜙𝜙𝑏𝑏𝑏𝑏𝑏𝑏𝑡𝑡𝑖𝑖

Free parameters:
𝑅𝑅𝑜𝑜 , 𝑓𝑓 + 𝑆𝑆𝑚𝑚

NOTE: the constant term in both equations represent any nonvarying rate, including the unmodulated termof an hypothetical WIMP component.
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3 years results (313.95 kgxy)[1-6] keV
MODEL 1[2-6] keV
MODEL 1

[1-6] keV
MODEL 2[2-6] keV
MODEL 2M. Martinez. F. ARAID & U. Zaragoza

Phys. Rev. D 103,102005 (2021)

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ANAIS-112 vs DAMA/LIBRA

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Improving data description

Phys. Rev. D 103,102005 (2021)

MODEL 3: Simultaneous fit using data and bkg model separately for every detector
𝑀𝑀𝑀𝑀
𝜇𝜇𝑖𝑖,𝑑𝑑 = 𝑅𝑅0,𝑑𝑑 (1 + 𝑓𝑓𝑑𝑑 𝜙𝜙𝑏𝑏𝑏𝑏𝑏𝑏,𝑑𝑑𝑡𝑡𝑖𝑖 + 𝑺𝑺𝒎𝒎 cos 𝜔𝜔 𝑡𝑡𝑖𝑖 − 𝑡𝑡0

𝑀𝑀𝑑𝑑 Δ𝐸𝐸Δ𝑡𝑡

19 Free parameters: 𝑅𝑅𝑜𝑜,𝑑𝑑 , 𝑓𝑓𝑑𝑑 + 𝑆𝑆𝑚𝑚
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3 years results (313.95 kgxy)Phys. Rev. D 103,102005 (2021)

MODEL 3: Simultaneous fit using data and bkg model separately for every detector[1-6] keV[2-6] keV

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3 years results (313.95 kgxy)Phys. Rev. D 103,102005 (2021)

MODEL 3: Simultaneous fit using data and bkg model separately for every detector[1-6] keV[2-6] keV

We are improving our filter
protocols in 1-2 keVResults soon!

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 202125

3 years results (313.95 kgxy)Phys. Rev. D 103,102005 (2021)

ANAIS-112 results:
123123Prog. Part. Nucl. Phys. 114 (2020) 103810• Compatible results for 3 different background descriptions/ fit approaches• Data supports the null hypothesis (lower p-value for [1-6]keV mainly due to detectors 1 and 5)• For the modulation hypothesis, we obtain in all cases best
fit modulation amplitudes compatible with zero at 1σ.
Best fit incompatible with DAMA/LIBRA at 3.3 (2.6) σ.
• As expected (Eur. Phys. J. C (2019) 79:233), Model 3 givesslightly slower 𝜎𝜎(𝑆𝑆𝑚𝑚 ) and is taken to quote final result
M. Martinez. F. ARAID & U. Zaragoza

Current sensitivity: 2.5σ [1−6] keV
2.7σ [2−6] keV

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Consistency checks• Time binning: negligible effect on results

Phys. Rev. D 103,102005 (2021)• Toy MC to check fit unbiasedness

Fit unbiased!

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Phase free analysis

Phys. Rev. D 103,102005 (2021)

DAMAANAIS
MODEL 1

MODEL 2

MODEL 3

Fit is non linear in the parameters
𝑀𝑀𝑀𝑀
𝜇𝜇𝑖𝑖 = 𝐴𝐴 𝑹𝑹𝟎𝟎 (1 + 𝒇𝒇𝜙𝜙𝑏𝑏𝑏𝑏𝑏𝑏
𝑡𝑡𝑖𝑖 + 𝑺𝑺𝒎𝒎 cos 𝜔𝜔 𝑡𝑡𝑖𝑖 − 𝒕𝒕𝟎𝟎

The fit with phase free is biased!!
𝝅𝝅
𝑬𝑬 𝑺𝑺𝒎𝒎 =𝝈𝝈𝟐𝟐Toy MC:• Best fit ANAIS 3𝜎𝜎 away from DAMA result• Considering bias, in most cases compatible at 1𝝈𝝈 with absence of modulation
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Frequency analysis

Phys. Rev. D 103,102005 (2021)

Least-squared periodogram:for every frequency, fit to null and modulation hypothesis and compute 𝜒𝜒02 − 𝜒𝜒 2MODEL 1

MODEL 2

→ No statistically significant modulation at any frequency

M. Martinez. F. ARAID & U. Zaragoza

MODEL 3Lomonosov Conference, August 19-25 2021

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Expected sensitivity
See details in Coarasa et al., Eur. Phys. J. C (2019) 79:233, 1812.02000
The experimental sensitivity isgiven by the standard deviation ofthe modulation amplitude 𝝈𝝈(𝑺𝑺𝒎𝒎 ),that can be calculated analyticallyfrom :- Updated background- Efficiency estimate and its error- Live time distribution
We quote our sensitivity to
DAMA/LIBRA result as the ratio
𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷
𝑆𝑆𝑚𝑚/𝜎𝜎(𝑆𝑆𝑚𝑚 )M. Martinez. F. ARAID & U. Zaragoza

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Experimental sensitivity
See details in Coarasa et al., Eur. Phys. J. C (2019) 79:233, 1812.02000

3y2y
1.5 y
3y

1.5 y

2y

M. Martinez. F. ARAID & U. Zaragoza

3 data releases ANAIS-112:• 1.5y: Phys. Rev. Lett. 123, 031301(2019)• 2y: J. Phys. Conf. Ser. 1468, 012014(2020)• 3y: arXiv: Phys. Rev. D 103, 102005(2021)

data confirm our sensitivity
projection
sensitivity @ 3 years: 2.5𝝈𝝈(2.7𝝈𝝈) in [1-6] ([2-6]) keV
3𝝈𝝈 sensitivity at reach inabout 1 year from now
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Corollary
Is this a model independent test of the DAMA/LIBRA result?
Using same target material -> direct comparison in electron recoil energy
In a scintillator, an ER produces much
more light than a NR of the same energy!

ERNRγMod Amplitude
WIMP 50 GeV

M. Martinez. F. ARAID & U. Zaragoza

The spectra are calibrated with X/𝛾𝛾 sources,
so are given in keVee(*). In order to beinterpreted as NR, 𝑸𝑸𝑭𝑭 has to be measured
to correct the energy scale:
𝑸𝑸𝑸𝑸 =

𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑙𝑙𝑁𝑁𝑁𝑁 /𝑘𝑘𝑘𝑘𝑘𝑘
𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑙𝑙𝐸𝐸𝐸𝐸 /𝑘𝑘𝑘𝑘𝑘𝑘(*) keVee: electron-equivalent keV

I recoil

𝑸𝑸𝑭𝑭𝑰𝑰 = 𝟎𝟎. 𝟎𝟎𝟎𝟎

the response ofdifferent detectors
to DM particles
could differ if QF isdifferent

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Corollary
Is this a model independent test of the DAMA/LIBRA result?
-> Need to improve our knowledge on NR response function
Does the QF depend on the crystal?
- Impurities- Tl level- Crystal quality- …
Or the spread in QF measurements isdue to systematics?

To answer this question,
Anais + Yale QF measurements @ TUNL (Duke Univ.)
different NaI(Tl) crystals (ANAIS & COSINE) in thesame setup

Results soon!

M. Martinez. F. ARAID & U. Zaragoza

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Summary• Currently, many efforts trying to provide an independent confirmation ofDAMA/LIBRA signal with the same target. ANAIS-112 and COSINE-100 in datataking.
• ANAIS-112: is taking data in stable condition @ LSC since 3rd August 2017 withexcellent performances. Up to now it has accumulated more than 300 kg×yexposure.
• ANAIS-112 results up to now are compatible with absence of modulation andincompatible with DAMA/LIBRA at 3.3(2.6)σ. Present sensitivity : 2.7σ (2.5σ) in[1-6] ([2-6]) keV after 3 years of data-taking. 3σ sensitivity at reach in about 1year from now.
• Work ongoing on improving filter protocols with machine learning techiniques• We are analyzing quenching factor on NaI crystals to discard systematic
uncertainties in the comparison.
• Plan to make ANAIS data public after use to allow independent analysis .

M. Martinez. F. ARAID & U. Zaragoza

Lomonosov Conference, August 19-25 2021

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