XENONnT
first results on
Electronic Recoil events

IDM2022 Knut Dundas Morå(knut.dundas.moraa@columbia.edu)

1Progress ofXENONnTNew techniques forremoval of impurities
and intrinsic background

Blinded analysis of
the first science data
A probe of theXENON1T excess
IDM2022 Knut Dundas Morå(knut.dundas.moraa@columbia.edu)2

27 institutes:

3167 members!

4

OBSERVABLE SIGNALS IN
LIQUID XENON-

ELECTRONIC RECOIL (ER)e-e5, 10, 15 keV ER

5, 10, 15 keV NRAxions or axion-likeparticles,
Dark PhotonsecS2 [PE]In addition to WIMP darkmatter and backgrounds,
several other dark matter ornew physics candidates cangive a signal:ee- ∼ 1 keV-ee

The XENON detectors wereconceived and designed tosearch for nuclear recoil
signals from WIMPER recoil energy
deposited in the liquid xenon
target is enough to yield acharacteristic scintillation +charge signal

ecS1 [PE]

NUCLEAR RECOIL (NR)ee

Neutrinosee

ELECTRON
EXCITED STATEXE RECOILSe5XENON1T ER SEARCH-Excess electronic recoil events in XENON1TPhys.Rev.D 102 (2020) 7, 072004

XENON1T observed a peakin its ER spectrum below ~7keV- ∼ 3σ-Excess fit to 2.3 keV peak,.
37Ar would be removed by-the online Kr distillation. The
necessary air leak to explain
the excess is > 13 l/y, upper
limit is 0.9 l/year
3H is possible— not as water

but as tritiated hydrogen.
Required rate much greaterthan expected frompurification.

A range of new physics
could be compatible with thepeak: solar axions, dark
photons, a neutrino
magnetic moment and manymore

3H: high raterequired

Review of signals in Snowmass2021 Cosmic
Frontier White Paper: on dark matter
excesses6

THE XENON DETECTORS
96cm

3.5 t liquid xenon in total● 2.0t active target● ~1t after fiducialization●●

248+6 PMTs

M. Schumann (AEC Bern) – XENON

8XENON10XENON100XENON1TXENONnT2005-2007

2008-20162012-20192020-2026 (takingscience data)

14 kg Xe target

62 kg Xe target

2 t Xe target~6 t Xe target, 8.6ttotal

4 ×10-47 cm2

Projection: 1.4×10-48
cm2 for 20 tonneyear~10-43 cm2~10-45 cm2~2000000
background ER
events/(keV t y)

1800 background ER 82 background ERevents/(keV t y)
events/(keV t y)

16.1 backgroundER events/(keV t y)71485 mm

8 mm

TWOPHASE TPC

Anode +4.9 kV
Gate +0.3 kV
FSRs

With XENONnT SR0
numbers

LiquidXenon

Cathode & Bottom
Grid -2.75 kV
PMTs
8Anode +4.9 kV
Gate +0.3 kV
FSRs

With XENONnT SR0
numbers-An Interaction
deposits energy,
scintillation lightand charge isliberated

1485 mm

8 mm

TWOPHASE TPC
LiquidXenon

Cathode & Bottom
Grid -2.75 kV
PMTs
8Anode +4.9 kV
Gate +0.3 kV
FSRs

With XENONnT SR0numbers-An Interaction
deposits energy,scintillation lightand charge isliberated

1485 mm

8 mm

TWOPHASE TPCeee

LiquidXenon

S1 signal reaches
photomultipliers

Cathode & Bottom
Grid -2.75 kV
PMTs
8-An Interaction
deposits energy,
scintillation lightand charge isliberated
S1 signal reaches
photomultipliers

1485 mmAnode +4.9 kVe

Gate +0.3 kVeFSRs

eLiquidXenon

Drift Field 23 V/cm

With XENONnT SR0numbers8 mm

TWOPHASE TPC

Electrons drift tothe surface
Cathode & Bottom
Grid -2.75 kVPMTs8With XENONnT SR0numbers-An Interaction
deposits energy,
scintillation lightand charge isliberated

1485 mm

8 mm

TWOPHASE TPCe

Extraction
Anode+4.9 kV
Field in LXe
2.9 kV/cm
Gate+0.3 kVe

FSRse

LiquidXenon

S1 signal reaches
photomultipliersElectrons drift tothe surface
The extraction field
pulls the electrons
to the gas phase
where they makemore scintillationlight

Cathode & Bottom
Grid -2.75 kV
PMTs8UPGRADES TO THEDETECTORSThe new TPC:
• increases the drift length to 1.5 m(from 1m)
• contains a 5.9 t active mass (from 2 t)
• Doubles the number of PMTs to 494,
and has a larger light detection
efficiency (34->36%)• Field shaping ring, tuneable potential
for the top one

A 4m x 3m neutron veto is now
enclosing the TPC, with 120 PMTs
placed inside an enclosure of reflectivepanels• neutron tagging efficiency projected to0.87 with (planned) Gd-doping, 0.68
with current pure water

Daniel Wenz
presented theneutron taggingTuesday9

LIQUID XENON PURIFICATION-G. Plante E. Aprile,J. Howlett, Y. Zhang
e-Print: 2205.07336 [physics.ins-det]

The 1.5 times longer drift
length demands
improvements in removing
electronegative impurities
that dampen the S2 signal
XENONnT uses a new liquid
purification technique withreplaceable filter units withextremely low radon
emanation (in the sciencerun mode).
High flow of 2 liters liquid
xenon / minute— reach very
high purity in less than aweek— 18 h to exchange theentire volume
Full TPCdrift timeelectronlifetime

electrons
surviving a fulldrift length

SR0XENON1T

0.67 ms

0.65 ms

30 %1T- 1ms

XENONnT

2.2 ms

10+ ms

86 % @ 15 ms

10RADON DISTILLATION- Rn222

is the primary sourceof background events inboth XENON1T andXENONnT.

-The newly developed Rn
column can handle large
xenon flows using radonfree compressors and heatexchangers
For the first science run, thecolumn operated in gasonly mode

e− −
e −e

SR0: 1.77 ± 0.01μBq/kg
SR1+: < 1 μBq/kg

currently we have beenable to reach < 1 μBq/kg
in science running mode

M. Murra, D. Schulte, C. Huhmann, C. Weinheimer
e-print: arXiv:2205.11492 [physics.ins-det]

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COMPUTING AND DAQ

Example Waveform
Display:- 100 MHz

XENON data is acquired atin “triggerless”
mode— individual channels
are read out any time they
cross the threshold-The data is reconstructed
and processed with theopen-source Strax+Straxen
frameworke − − 83mKr event
ecS2 = 8838 PE, Z = − 103 cm

cS1a = 263 PE, cS1b = 66 PE
e−2+ orders of magnitude
faster than its XENON1Tpredecessors

Check out Straxen atgithub.com/XENONnT/straxen
The XENON1T Data Acquisition System
JINST 14 (2019) 07, P07016

123
CONTROLLING H--

XENONnT went throughsignificant eﬀorts to reduce
possible sources of a low-energy
excessTwo months of outgassing, andpurification of gaseous xenon
with Zr getters and 3 weeks ofgaseous xenon cleaning reduces
possible hydrogencontamination

Bypassing getters in thepurification loop would increase
the equilibrium hydrogenconcentration in the detector
large uncertainty but a bestestimate of several orders ofmagnitude, and a very
conservative estimate of x10
14.3 days was taken after themain science run to give an extra
handle on a possible excess

Tritium-enhanced data (TED)
sideband data used to look for 3H
bypassing getters

No 3H excess
13FIRST SCIENCE RUN— XENONnT SR0-97.1 days exposure from July 6th-Nov 11th 2021
Rn column in gas-only modeAll but 17 PMTs working, gain stable at 3%220

Rn data-23 V/cm drift field, Extraction Field in LXe 2.9 kV/cmLocalised high single-electron emission occurringseemingly at random, anode ramped down

97.1 days

AmBe data
83m

Kr dataSR0datadata
HotspotTED
37

Ar data14

CALIBRATION AND ANALYSIS-The SR0 analysis eﬀort covers-

Peak and event
reconstruction,“corrections”—
compensating for detector
responses to give goodestimators“raw” S2
S2 corrected for depth
cS2: also corrected forinhomogeneous response

Data quality validation, cuts
against backgrounds
Backgrounds models
Detector response modelling
Inference

15

RECONSTRUCTION EFFICIENCY-

At threshold, S1s may consistof only a handful of photons,
while we require 3 coincident
hits.
Estimated with detailed“waveform simulation” and adata-driven approach drawing
subsamples of photon hits tomake up a pulse
In both cases, given to thereconstruction chain tocharacterise eﬃciency:
probability to reconstruct apeak
Waveform simulation used forthis analysis, data-driven forvalidation— include an
uncertainty band that covers
the diﬀerence between thesemethods.
16CALIBRATION SOURCES-Rn and Ar calibration inreconstructed energy

At low energy, we have two
ER calibration sources:- Ar37, which gives monoenergetic 2.82 keVpeak
used to anchor the lowenergy response andresolution models withhigh statistics-212

Pb from 220Rn gives aroughly flat β-spectrum
to estimate cut
acceptances and alsovalidates our threshold.

-Also used to define
our blinding region

220Rn calibrationin cS1, cS2
Below band; wall and AC events
17

CALIBRATION AND ELECTRIC
FIELD SIMULATION VALIDATION
Kr is injected every 14- days83m- T = 1.83 hDecays slowly enough( 1/2) to distribute
uniformly in the detector,
used to compute:-LUX describing the field method: Phys. Rev.
D 96, 112009(2017)

the S1 light collection
eﬃciency as function ofposition
The S2 light collection
eﬃciency as function ofhorizontal position
The position
reconstruction distortion
induced by our field

Validated COMSOL field
simulation using observed
83mKr signal ratio

Field Simulation
validation
using krypton data

S(32.1 keV)/S(9.4 keV)18

ENERGY SCALE CALIBRATION,YIELD STABILITY-For ER sources, the entire
deposited energy goes toobservable light and charge
quanta:E = 13.7eV × (cS1/g1 + cS2/g2)
Mono-energetic peaks withenergies relevant to our ER search(1 − 140 keV).

- Ar- Kr- Xe- Xe37

g1 = (0.151 ± 0.001)PE/phg2 = (16.5 ± 0.6)PE/e−83m

129m

131m

-

The observed bias in energies fromour reconstruction, between 1-2%
is included in the modelling.
We monitor the stability of the lightand charge yield over SR0 using
the calibration sources, 222Rn αs
and material γs

See Henning Schulze Eißings
poster (216)!

ΔLy = 1 %ΔQy = 1.9 %19

RARE SIGNAL BECOMES A
VALIDATION TOOL-XENON1T first observed thedouble-electron capture
signature from 124Xe— longest
half-life directly detected

XENON1T

In XENONnT, appears as avery clear peak over the
lower background, with a ratecompatible with previous
measurements, left free inbackground.
DEC used to cross-check g1/g2 fit

2νECEC
T1/2= (1.15 ± 0.13stat ± 0.14sys) × 1022yr

XENON1T observation of Double-Weak Decaysof 124Xe and 136Xe, arXiv:2205.04158

DEC rate/ nominal

20

RARE SIGNAL BECOMES A
VALIDATION TOOL-XENON1T first observed thedouble-electron capture
signature from 124Xe— longest
half-life directly detected
In XENONnT, appears as avery clear peak over thelower background, with a ratecompatible with previous
measurements, left free inbackground.
DEC used to cross-check g1/g2 fit

2νECEC
T1/2= (1.15 ± 0.13stat ± 0.14sys) × 1022yr

XENON1T observation of Double-Weak Decaysof 124Xe and 136Xe, arXiv:2205.04158

DEC rate/ nominal

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DATA QUALITY CUTS-

Events are required to passa range of quality cuts:
The S1 and S2 peakshould each havepatterns, top/bottom
ratios etc. consistent
with real events-Average total cut
acceptance: 86%

An S2 width consistent
with the expected
diﬀusion
An S2 over 500 PE
Not within < 300 ns of aneutron veto event

Events must be within ERband
Fiducial volume cut selects
a mass of (4.37 ± 0.14) tonnes
with low backgrounds
21

BACKGROUNDS-The low-energy ER spectrum is dominated by 214Pb at thevery lowest energy, plus contributions for materials, 136Xeand solar neutrinos.

External constraints are included for-85Kr,

2 × 10−11 of (56 ± 36) ppq using RGMS

material γs, (2.1 ± 0.4) events/(t × yr × keV) fromGEANT4 and screening measurements
136Xe from RGA anduncertainty

T1/2 measurements, with a shapesolar neutrinos have a 10% rate uncertainty given theBorexino measurements of the flux.
AC is constrained from its data-driven model

214Pb

Number ofevents inER band
1-140 keV
980 ± 12085Kr

91 ± 58

5.8 ± 3.7

Materials

267 ± 5116.2 ± 3.1136Xe

1523 ± 54

8.7 ± 0.3

Solarneutrino

298 ± 2924.5 ± 2.4

124Xe

256 ± 28

2.6 ± 0.3

Accidental
0.71 ± 0.03
coincidence

0.71 ± 0.03

Expected< 10 keV

56 ± 7133Xe

163 ± 63083mKr80 ± 16022

COLLECTED DATA
-97.1 days exposure from July 6th-Nov 11th 2021
Rn column in gas-only modeAll but 17 PMTs working, gain stable at 3%

220Rn data

-23 V/cm drift field, Extraction Field in LXe 2.9 kV/cmLocalised high single-electron emission occurringseemingly at random, anode ramped down

97.1 days

AmBe data
83m

Kr dataSR0datadata
Single electron spot
TED
37

Ar data23

THE XENONnT ELECTRONIC RECOIL SPECTRUM
2nd order weakprocesses dominating
spectral shape!

136Xe

124Xe

2νββ2νECEC

24

THE XENONnT ELECTRONIC RECOIL SPECTRUM

NR Still Blinded(Peak is DEC)

25

COMPARISON WITH THE 1T EXCESS

26

Key conclusions
Exposure: 1.16 tonne − years

Background rate:∼ × 2 XENON1T ER search(0.65 tonne-years)(16.1 ± 0.3) events/(t × yr × keV)

∼ × 0.2 XENON1TBest-fit signal strength: 0XENONnT rejects a XENON1T-size
peak at 8.6σ

Exclusion of XENON1T excess(2.3 keV) peak.

Measurements
incompatible at ~4σ

in 1-30 keV range

Most likely explanation of XENON1T excess is a small 3H contamination.
XENONnT, taking steps to reduce tritium outgassing sees no excess
27

LIMITS ON ALPS AND DARK PHOTONS
ALPs-Dark γ

A search for a peak from axion-like particles or dark photons sees no significant excess,but places new stringent limits between 1-140 keVSince the 83mKr rate is left unconstrained, we do not place limits at 41.5 keV

28

LIMITS ON SOLAR AXIONS-XENONnT is compatible with background-only and places new limits on theaxion-electron, γ and nucleon couplings.
Axion signal assumes axio-electric eﬀect and reverse Primakoﬀ eﬀect;
described by gae, gaγ, gan
90% upper limit on 57Fe solar axion component is 20.4 events/(t × yr)
29

LIMITS ON NEUTRINO MAGNETIC MOMENTLaboratory

Astrophysical-

A magnetic moment is implied by neutrinos being massive— if new physics
raises this magnetic moment, it may cause an enhanced neutrino scatteringrateUpper limit at μν < 6.3 × 10−12μB

30Summary> 10 ms electron lifetime,
1.77 ± 0.01 μBq/kg
radon concentration

Blinded analysis of ER
data (double-blinded?)
Excellent agreementwith our background
model
31

XENONnT lowER
paper online
arXiv imminent

Until then:xenonexperiment.org/
later today

IDM2022 Knut Dundas MoråIDM2022 KNUT DUNDAS MORÅ(knut.dundas.moraa@columbia.edu)(KNUT.DUNDAS.MORAA@COLUMBIA.EDU)

32

More toCome!
The combined liquid+gas
Rn removal will further
reduce the background level

Further analysis channels
and deeper detector
knowledge

Nuclear recoil search
results soon
IDM2022 Knut Dundas MoråIDM2022 KNUT DUNDAS MORÅ(knut.dundas.moraa@columbia.edu)(KNUT.DUNDAS.MORAA@COLUMBIA.EDU)

33

More toCome!
The combined liquid+gas
Rn removal will further
reduce the background level

Further analysis channels
and deeper detector
knowledge

And farther in the future:xlzd.org

DNuclear recoil search
results soon
IDM2022 Knut Dundas MoråIDM2022 KNUT DUNDAS MORÅ(knut.dundas.moraa@columbia.edu)(KNUT.DUNDAS.MORAA@COLUMBIA.EDU)

33

More toCome!
The combined liquid+gas
Rn removal will further
reduce the background level

Further analysis channels
and deeper detector
knowledge

Nuclear recoil search
results soon
IDM2022 Knut Dundas MoråIDM2022 KNUT DUNDAS MORÅ(knut.dundas.moraa@columbia.edu)(KNUT.DUNDAS.MORAA@COLUMBIA.EDU)

33