The field of dark matter detection is a highly visible and highly competitive one. In this paper, we propose recommendations for presenting dark matter direct detection results particularly suited ...for weak-scale dark matter searches, although we believe the spirit of the recommendations can apply more broadly to searches for other dark matter candidates, such as very light dark matter or axions. To translate experimental data into a final published result, direct detection collaborations must make a series of choices in their analysis, ranging from how to model astrophysical parameters to how to make statistical inferences based on observed data. While many collaborations follow a standard set of recommendations in some areas, for example the expected flux of dark matter particles (to a large degree based on a paper from Lewin and Smith in 1995), in other areas, particularly in statistical inference, they have taken different approaches, often from result to result by the same collaboration. We set out a number of recommendations on how to apply the now commonly used Profile Likelihood Ratio method to direct detection data. In addition, updated recommendations for the Standard Halo Model astrophysical parameters and relevant neutrino fluxes are provided. The authors of this note include members of the DAMIC, DarkSide, DARWIN, DEAP, LZ, NEWS-G, PandaX, PICO, SBC, SENSEI, SuperCDMS, and XENON collaborations, and these collaborations provided input to the recommendations laid out here. Wide-spread adoption of these recommendations will make it easier to compare and combine future dark matter results.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Pulse shape discrimination with pure CsI scintillators is
investigated as a method for separating energy deposits by energetic
neutrons and photons at particle physics experiments. Using ...neutron
data collected near the European XFEL XS1 beam window the pulse
shape discrimination capabilities of pure CsI are studied and
compared to CsI(Tl) using near-identical detector setups, which were
operated in parallel. The inelastic interactions of 100 MeV
neutrons are observed to produce a slower scintillation emission in
pure CsI relative to energy deposits from cosmic muons. By
employing a charge-ratio method for pulse shape characterization,
pulse shape discrimination with pure CsI is shown to be effective
for identifying energy deposits from neutrons vs. cosmic muons,
however, pure CsI was not able resolve the specific type of neutron
inelastic interactions as can be done with CsI(Tl). Using pulse
shape discrimination, the rate of energetic neutron interactions in
a pure CsI detector is measured as a function of time and shown to
be correlated with the European XFEL beam power. The results
demonstrate that pulse shape discrimination with pure CsI has
significant potential to improve electromagnetic vs. hadronic
shower identification at future particle physics experiments.
The proton light output function in electron-equivalent energy of various scintillators based on linear alkylbenzene (LAB) has been measured in the energy range from 1 MeV to 17.15 MeV for the first ...time. The measurement was performed at the Physikalisch–Technische Bundesanstalt (PTB) using a neutron beam with continuous energy distribution. The proton light output data is extracted from proton recoil spectra originating from neutron–proton scattering in the scintillator. The functional behavior of the proton light output is described successfully by Birks’ law with a Birks constant
kB
between (0.0094±0.0002) cm MeV
−1
and (0.0098±0.0003) cm MeV
−1
for the different LAB solutions. The constant
C
, parameterizing the quadratic term in the generalized Birks law, is consistent with zero for all investigated scintillators with an upper limit (95 % CL) of about 10
−7
cm
2
MeV
−2
. The resulting quenching factors are especially important for future planned supernova neutrino detection based on the elastic scattering of neutrinos on protons. The impact of proton quenching on the supernova event yield from neutrino–proton scattering is discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The SuperCDMS SNOLAB dark matter search experiment aims to
be sensitive to energy depositions down to
(1 eV). This imposes requirements on the resolution,
signal efficiency, and noise ...rejection of the trigger system. To
accomplish this, the SuperCDMS level-1 trigger system is implemented
in an FPGA on a custom PCB. A time-domain optimal filter algorithm
realized as a finite impulse response filter provides a baseline
resolution of 0.38 times the standard deviation of the noise,
σ
n
, and a 99.9% trigger efficiency for signal
amplitudes of 1.1 σ
n
in typical noise
conditions. Embedded in a modular architecture, flexible trigger
logic enables reliable triggering and vetoing in a dead-time-free
manner for a variety of purposes and run conditions. The trigger
architecture and performance are detailed in this article.
Recent breakthroughs in cryogenic silicon detector technology allow for the observation of single electron-hole pairs released via particle interactions within the target material. This implies ...sensitivity to energy depositions as low as the smallest band gap, which is ∼ 1.2 eV for silicon, and therefore sensitivity to eV / c2-scale bosonic dark matter and to thermal dark matter at masses below 100 MeV / c2. Various interaction channels that can probe the lowest currently accessible masses in direct searches are related to standard photoelectric absorption. In any of these respective dark matter signal models any uncertainty on the photoelectric absorption cross section is propagated into the resulting exclusion limit or into the significance of a potential observation. Using first-time precision measurements of the photoelectric absorption cross section in silicon recently performed at Stanford University, this article examines the importance having accurate knowledge of this parameter at low energies and cryogenic temperatures for these dark matter searches.
The use of cryogenic silicon as a detector medium for dark matter searches is gaining popularity. Many of these searches are highly dependent on the value of the photoelectric absorption cross ...section of silicon at low temperatures, particularly near the silicon bandgap energy, where the searches are most sensitive to low mass dark matter candidates. While such cross section data have been lacking from the literature, previous dark matter search experiments have attempted to estimate this parameter by extrapolating it from higher temperature data. However, discrepancies in the high temperature data have led to order-of-magnitude differences in the extrapolations. In this paper, we resolve these discrepancies by using a novel technique to make a direct, low temperature measurement of the photoelectric absorption cross section of silicon at energies near the bandgap (1.2 eV–2.8 eV).
The Formula omitted-particle light response of liquid scintillators based on linear alkylbenzene (LAB) has been measured with three different experimental approaches. In the first approach, Formula ...omitted-particles were produced in the scintillator via Formula omittedC(n, Formula omitted) Formula omittedBe reactions. In the second approach, the scintillator was loaded with 2 % of Formula omittedSm providing an Formula omitted-emitter, Formula omittedSm, as an internal source. In the third approach, a scintillator flask was deployed into the water-filled SNO+ detector and the radioactive contaminants Formula omittedRn, Formula omittedPo and Formula omittedPo provided the Formula omitted-particle signal. The behavior of the observed Formula omitted-particle light outputs are in agreement with each case successfully described by Birks' law. The resulting Birks parameter kB ranges from Formula omitted to Formula omitted cm/MeV. In the first approach, the Formula omitted-particle light response was measured simultaneously with the light response of recoil protons produced via neutron-proton elastic scattering. This enabled a first time a direct comparison of kB describing the proton and the Formula omitted-particle response of LAB based scintillator. The observed kB values describing the two light response functions deviate by more than Formula omitted. The presented results are valuable for all current and future detectors, using LAB based scintillator as target, since they depend on an accurate knowledge of the scintillator response to different particles.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The extended physics program of the SuperCDMS SNOLAB dark
matter search experiment aims to maximize the sensitivity to
low-mass dark matter. To realize this, an upgrade of the existing
...level-1 trigger of the data acquisition system is proposed by making
use of a recurrent neural network to be implemented on the trigger
FPGA. This provides an improved amplitude estimator and signal-noise
discriminator based on the combined information of filtered traces
from individual detector channels. The architecture and
configuration of this neural trigger are discussed in this article,
and the improvements in key performance indicators such as the
efficiency, resolution, and noise rate are quantified based on
signal simulations and noise data. Based on the findings in this
proof of concept, the trigger threshold is expected to be lowered by
∼ 22%.
SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass particles (with masses ≤10 GeV/c2) that may constitute dark matter by using cryogenic detectors of two types ...(HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections ∼1×10−43 cm2 for a dark matter particle mass of 1 GeV/c2, and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low-energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but cosmogenically produced H3 and naturally occurring Si32 will be present in the detectors at some level. Even if these backgrounds are 10 times higher than expected, the science reach of the HV detectors would be over 3 orders of magnitude beyond current results for a dark matter mass of 1 GeV/c2. The iZIP detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particles with masses ≳5 GeV/c2. The mix of detector types (HV and iZIP), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. Upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the “neutrino floor,” where coherent scatters of solar neutrinos become a limiting background.
Aligning body, mind and spirit, acquiring emotional intelligence, an unshakable belief in their own intuition and producing outcomes in the context of organisational abilities encompass the ...attributes of leaders that emerged from this holistic exploration of leadership development. Emotionally aware leaders demonstrated their authenticity and cared for peaceful process. In this exploration such leaders started at the bottom within their enterprise working their way up over time. Agreeableness and flexibility were the core competencies they developed amongst others. A complex mix of behaviour, thoughts and emotions were the specific leadership attributes that were found to differ for different organisations. These specific leadership attributes needed to fit with the character and dynamics of the organisation. Since leadership development was found to be a holistic character development over time leadership courses are recommended for all scholars and students, with a strong emphasis on self-development. A grounded theory approach to this holistic exploration of leadership development serves the community well, by promoting the emergence of grounded theories which are free from practical impossibilities.
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