The XENON Dark Matter Project at Gran Sasso National Laboratory - AndreaMolinario PATRAS2019
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The XENON Dark Matter Project at Gran Sasso National Laboratory Andrea Molinario PATRAS 2019
XENON collaboration
~160 scientists
27 institutions
A. Molinario PATRAS 2019 2
Dual-phase Xenon TPC
Liquid Xenon
High density, self-
shielding
Good scintillator
No long-living radioactive
isotope
Time Projection Chamber
3D position
ER/NR discrimination
Multiple scatter rejection
Low energy threshold
A. Molinario PATRAS 2019 Scalable to multi-ton 3
Dual-phase Xenon TPC
Liquid Xenon
High density, self-
shielding
Good scintillator
No long-living radioactive
isotope
Time Projection Chamber
3D position
ER/NR discrimination
Multiple scatter rejection
Low energy threshold
A. Molinario PATRAS 2019 Scalable to multi-ton 4
Dual-phase Xenon TPC
Liquid Xenon
High density, self-
shielding
Good scintillator
No long-living radioactive
isotope
Time Projection Chamber
3D position
ER/NR discrimination
Multiple scatter rejection
Ideal for WIMP and rare processes search Low energy threshold
A. Molinario PATRAS 2019 Scalable to multi-ton 5
Timeline of the project
@ LNGS XENONnT
Background in ROI (events/(ton yr keVee))
104
XENON1T
5.9 ton
2 ton 10
103
Active Mass (kg)
XENON100 σSI~10-48cm2 102
102 XENON10 62 kg σSI~10-47cm2
103
15 kg
104
10 σSI~10-45cm2
105
σSI~10 cm
-43 2
2005 2012 2020
A. Molinario PATRAS 2019 6
XENON1T
Cryogenics
Purification
Electronics
DAQ
Water tank
Muon Veto
Kr distillation
column
Recovery
and
Storage
A. Molinario PATRAS 2019 7
Data taking
278.8 days
1 ton-year
exposure
SR0 SR1
32 days 247 days
Monitoring the stability of the detector and PMTs
A. Molinario PATRAS 2019 8
Electronic recoil background
Initially Kr-dominated
Kr concentration reduced by
distillation from 1 ppb to 0.7 ppt
SR1 ER background dominated
by 222Rn (mainly 214Pb β-decay)
Source Fraction Mitigation strategy ER background in the ROI
[%]
222
Rn 85 S2/S1, material selection 82+5-3(syst) ± 3 (stat)
Solar ν 5 S2/S1 events/(ton yr keVee)
85
Kr 4 S2/S1, distillation
Lowest ER background for
Materials 4 S2/S1, material selection, fiduc. a dark matter detector
136
Xe 1 S2/S1
A. Molinario PATRAS 2019 9
Nuclear recoil background Source Mitigation strategy Radiogenic neutrons (from Material selection, reject multiple scatter, fiducialization materials) CEνNS (mainly 8B solar ν) Cosmogenic neutrons Muon Veto, reject multiple scatter, fiducialization Dedicated search for multiple scatter events found 9 candidates with (6.4±3.2) expected Constrain the expected single- scatter neutron event rate A. Molinario PATRAS 2019 10
Other backgrounds
Accidental coincidences
Random pairing of lone S1 and S2
Background model derived from data
and used in likelihood estimation
Surface events
Rn progeny
222
Charge loss Events
plate-out on the which reduces shifted in
inner surface of S2 size NR band
PTFE panels
Data-driven background model
A. Molinario PATRAS 2019 11Background predictions
ROI corresponds in average to Background model in 4 dimensions:
[4.9, 40.9] keVnr ([1.4, 10.6 ] keVee) S1, S2, R, Z
NR reference region Statistical inference in 1.3 t fiducial
50% NR acceptance with 99.75% ER rejection volume and full (S1, S2) space
A. Molinario PATRAS 2019 12SI-WIMP result
All selection criteria were
defined before unblinding
A. Molinario PATRAS 2019 13SI-WIMP result
Events that pass all cuts are shown
They are shown as pie charts
representing the best-fit probabilities of
the background and signal (200 GeV
WIMP) components at each event
A. Molinario PATRAS 2019 14SI-WIMP result
1.3 t
0.9 t
Performed unbinned profile
likelihood, model uncertainties
included as nuisance parameters
Maximum radius of 1.3 t fiducial
volume set by surface event
contribution.
A. Molinario PATRAS 2019 15SI-WIMP result
E. Aprile et al., Phys. Rev. Lett. 121, 111302 (2018)
Median sensitivity 7
times better than
previous experiments
No significant excess
(>3σ) in the 1.3 tons
fiducial volume at any
WIMP mass
σSISD-WIMP result
E. Aprile et al., Phys. Rev. Lett. 122, 141301 (2019)
Neutron-only Proton-only
Same event selection criteria
for a SD search
Most stringent limit on WIMP-
neutron scattering cross section
Exclude new parameter space in isoscalar
theory with axial-vector mediator
A. Molinario PATRAS 2019 17WIMP-Pion coupling
E. Aprile et al., Phys. Rev. Lett. 122, 071301 (2019)
Coupling of WIMP with virtual pion-current between two nucleons
Same falling exponential differential recoil spectrum as WIMP-nucleon interaction
Limit setting as in SI analysis
A. Molinario PATRAS 2019 18124
Xe Double Electron Capture
124
Xe + 2e- → 124Te + 2νe
Detection of X-rays and
Auger electrons
Total energy (64.3±0.6) keV
Background from
125
I produced by Blinded [56-72] keV
124
Xe activation region
A. Molinario PATRAS 2019 19124
Xe Double Electron Capture
124
Xe DEC
124
Xe + 2e- → 124Te + 2νe
Detection of X-rays and 125
I at 67.3 keV
Auger electrons
Total energy (64.3±0.6) keV
Detected peak at (64.2±0.5) keV with 4.4σ significance
Measured half-life of the process T1/2 = (1.8 ± 0.5stat ± 0.1sys) x 1022 y
E. Aprile et al., Nature 568 (2019), no.7753, 532535
A. Molinario PATRAS 2019 20124
Xe Double Electron Capture
:2 5
1 2
a t
a DECy
r dXe
i
124
n F
n o
124
Xe + 2e- → 124Te + 2νe a n
Detection of X-rays and d em
L in 125
I at 67.3 keV
Auger electrons
S .
y keV
Total energy (64.3±0.6)
b
al k
d t
Detected peak
a t e at (64.2±0.5) keV with 4.4σ significance
ic
d half-life of the process T1/2 = (1.8 ± 0.5stat ± 0.1sys) x 1022 y
e
Measured
D
E. Aprile et al., Nature 568 (2019), no.7753, 532535
A. Molinario PATRAS 2019 21Ongoing analysis S2-only analysis WIMP search with Migdal effect ALPs, Super WIMPs, Dark photons, Solar Axions Annual modulation 0νββ of 136Xe 37 Ar calibration A. Molinario PATRAS 2019 22
Ongoing analysis S2-only analysis WIMP search with Migdal effect Low energy Electronic Recoils ALPs, Super WIMPs, Dark photons, Solar Axions Annual modulation 0νββ of 136Xe 37 Ar calibration A. Molinario PATRAS 2019 23
Tests after SR1
Upgrade of purification system
New magnetic pump
Increased purification of gas flow
1 ms electron lifetime reached
Rn-removal
With new magnetic pump Radon reduced by
45%
Rn distillation tested, another 30% reduction
Factor 4 above XENONnT goal (1μBq/kg)
37
Ar calibration
Test of new calibration source for
low energy ER (2.8 keV, 0.27 keV)
A. Molinario PATRAS 2019 24XENONnT A. Molinario PATRAS 2019 25
New features XENONnT
NEW TPC LXE PURIFICATION
494 PMTs Much faster
purification
1.5 m height speed
1.3 m diameter Possible to purify
the 8 t of Xe in a
reasonable time
RADON NEUTRON
DISTILLATION VETO
COLUMN
Goal 1 μBq/kg 0.2% Gd-
Rn contamination doped
water
Rn distillation 120 additional
already tested PMTs around
in XENON1T cryostat
A. Molinario PATRAS 2019 26Conclusions
XENON1T reached 1 ton-year exposure with the lowest ER
background for a dark matter detector
Most stringent limit for WIMP-nucleon SI cross section
was set for WIMP masses greater than 6 GeV/c2
First detection of double electron capture of 124
Xe, longest
half-life ever measured
Upgrade to XENONnT is ongoing, expected to start data
taking by the end of 2019
A. Molinario PATRAS 2019 27A. Molinario PATRAS 2019 28
Calibrations (1) A. Molinario PATRAS 2019 29
Calibrations (2) A. Molinario PATRAS 2019 30
Data – MC matching A. Molinario PATRAS 2019 31
SI-WIMP result A. Molinario PATRAS 2019 32
0νββ decay A. Molinario PATRAS 2019 33
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