We report on a search for electronic recoil event rate modulation signatures in the XENON100 data accumulated over a period of 4 yr, from January 2010 to January 2014. A profile likelihood method, ...which incorporates the stability of the XENON100 detector and the known electronic recoil background model, is used to quantify the significance of periodicity in the time distribution of events. There is a weak modulation signature at a period of 431_{-14}^{+16} day in the low energy region of (2.0-5.8) keV in the single scatter event sample, with a global significance of 1.9σ; however, no other more significant modulation is observed. The significance of an annual modulation signature drops from 2.8σ, from a previous analysis of a subset of this data, to 1.8σ with all data combined. Single scatter events in the low energy region are thus used to exclude the DAMA/LIBRA annual modulation as being due to dark matter electron interactions via axial vector coupling at 5.7σ.
Xenon dual-phase time projection chambers designed to search for weakly interacting massive particles have so far shown a relative energy resolution which degrades with energy above
∼
200 keV due to ...the saturation effects. This has limited their sensitivity in the search for rare events like the neutrinoless double-beta decay of
136
Xe
at its
Q
value,
Q
β
β
≃
2.46
MeV
. For the XENON1T dual-phase time projection chamber, we demonstrate that the relative energy resolution at
1
σ
/
μ
is as low as (
0.80
±
0.02
) % in its one-ton fiducial mass, and for single-site interactions at
Q
β
β
. We also present a new signal correction method to rectify the saturation effects of the signal readout system, resulting in more accurate position reconstruction and indirectly improving the energy resolution. The very good result achieved in XENON1T opens up new windows for the xenon dual-phase dark matter detectors to simultaneously search for other rare events.
The XENON1T dark matter experiment aims to detect weakly interacting massive particles (WIMPs) through low-energy interactions with xenon atoms. To detect such a rare event necessitates the use of ...radiopure materials to minimize the number of background events within the expected WIMP signal region. In this paper we report the results of an extensive material radioassay campaign for the XENON1T experiment. Using gamma-ray spectroscopy and mass spectrometry techniques, systematic measurements of trace radioactive impurities in over one hundred samples within a wide range of materials were performed. The measured activities allowed for stringent selection and placement of materials during the detector construction phase and provided the input for XENON1T detection sensitivity estimates through Monte Carlo simulations.
We detail the sensitivity of the proposed liquid xenon DARWIN observatory to solar neutrinos via elastic electron scattering. We find that DARWIN will have the potential to measure the fluxes of five ...solar neutrino components:
pp
,
7
Be,
13
N,
15
O and
pep
. The precision of the
13
N,
15
O and
pep
components is hindered by the double-beta decay of
136
Xe and, thus, would benefit from a depleted target. A high-statistics observation of
pp
neutrinos would allow us to infer the values of the electroweak mixing angle,
sin
2
θ
w
, and the electron-type neutrino survival probability,
P
ee
, in the electron recoil energy region from a few keV up to 200 keV for the first time, with relative precision of 5% and 4%, respectively, with 10 live years of data and a 30 tonne fiducial volume. An observation of
pp
and
7
Be neutrinos would constrain the neutrino-inferred solar luminosity down to 0.2%. A combination of all flux measurements would distinguish between the high- (GS98) and low-metallicity (AGS09) solar models with 2.1–2.5
σ
significance, independent of external measurements from other experiments or a measurement of
8
B neutrinos through coherent elastic neutrino-nucleus scattering in DARWIN. Finally, we demonstrate that with a depleted target DARWIN may be sensitive to the neutrino capture process of
131
Xe.
The XENON1T experiment aims for the direct detection of dark matter in a detector filled with 3.3 tons of liquid xenon. In order to achieve the desired sensitivity, the background induced by ...radioactive decays inside the detector has to be sufficiently low. One major contributor is the
β
-emitter
85
Kr which is present in the xenon. For XENON1T a concentration of natural krypton in xenon
nat
Kr
/
Xe
<
200
ppq
(parts per quadrillion,
1
ppq
=
10
-
15
mol
/
mol
) is required. In this work, the design, construction and test of a novel cryogenic distillation column using the common McCabe–Thiele approach is described. The system demonstrated a krypton reduction factor of
6.4
·
10
5
with thermodynamic stability at process speeds above 3 kg/h. The resulting concentration of
nat
Kr
/
Xe
<
26
ppq
is the lowest ever achieved, almost one order of magnitude below the requirements for XENON1T and even sufficient for future dark matter experiments using liquid xenon, such as XENONnT and DARWIN.
We report the results of a search for the inelastic scattering of weakly interacting massive particles (WIMPs) in the XENON1T dark matter experiment. Scattering off 129Xe is the most sensitive probe ...of inelastic WIMP interactions, with a signature of a 39.6 keV deexcitation photon detected simultaneously with the nuclear recoil. Using an exposure of 0.83 tonne-years, we find no evidence of inelastic WIMP scattering with a significance of more than 2σ. A profile-likelihood ratio analysis is used to set upper limits on the cross section of WIMP-nucleus interactions. We exclude new parameter space for WIMPs heavier than 100 GeV=c2, with the strongest upper limit of 3.3 × 10−39 cm2 for 130 GeV=c2 WIMPs at 90% confidence level.
We present first results on the scalar coupling of weakly interacting massive particles (WIMPs) to pions from 1 t yr of exposure with the XENON1T experiment. This interaction is generated when the ...WIMP couples to a virtual pion exchanged between the nucleons in a nucleus. In contrast to most nonrelativistic operators, these pion-exchange currents can be coherently enhanced by the total number of nucleons and therefore may dominate in scenarios where spin-independent WIMP-nucleon interactions are suppressed. Moreover, for natural values of the couplings, they dominate over the spin-dependent channel due to their coherence in the nucleus. Using the signal model of this new WIMP-pion channel, no significant excess is found, leading to an upper limit cross section of 6.4×10^{-46} cm^{2} (90% confidence level) at 30 GeV/c^{2} WIMP mass.
The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are ...reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and
222
Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background (
∼
17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected
222
Rn activity concentration in XENONnT is determined to be 4.2 (
-
0.7
+
0.5
)
μ
Bq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system.
Multiple viable theoretical models predict heavy dark matter particles with a mass close to the Planck mass, a range relatively unexplored by current experimental measurements. We use 219.4 days of ...data collected with the XENON1T experiment to conduct a blind search for signals from multiply interacting massive particles (MIMPs). Their unique track signature allows a targeted analysis with only 0.05 expected background events from muons. Following unblinding, we observe no signal candidate events. This Letter places strong constraints on spin-independent interactions of dark matter particles with a mass between 1×10^{12} and 2×10^{17} GeV/c^{2}. In addition, we present the first exclusion limits on spin-dependent MIMP-neutron and MIMP-proton cross sections for dark matter particles with masses close to the Planck scale.
We perform a blind search for particle signals in the XENON1T dark matter detector that occur close in time to gravitational-wave signals in the LIGO and Virgo observatories. No particle signal is ...observed in the nuclear recoil and electronic recoil channels within ±500 seconds of observations of the gravitational-wave signals GW170104, GW170729, GW170817, GW170818, and GW170823. We use this null result to constrain monoenergetic neutrinos and axion-like particles emitted in the closest coalescence GW170817, a binary neutron star merger. We set new upper limits on the fluence (time-integrated flux) of coincident neutrinos down to 17 keV at the 90% confidence level. Furthermore, we constrain the product of the coincident fluence and cross section of axion-like particles to be less than 10 −29 cm 2 /cm 2 in the 5.5–210 keV energy range at the 90% confidence level.
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