Abstract
Dark Matter experiments searching for Weakly interacting massive particles (WIMPs) primarily use nuclear recoils (NRs) in their attempt to detect WIMPs.
Migdal-induced electronic recoils ...(ERs) provide additional sensitivity to light Dark Matter with (GeV/
c
2
) masses.
In this work, we use Bayesian inference to find the parameter space where future detectors like XENONnT and SuperCDMS SNOLAB will be able to detect WIMP Dark Matter through NRs, Migdal-induced ERs or a combination thereof.
We identify regions where each detector is best at constraining the Dark Matter mass and spin independent cross-section and infer where two or more detection configurations are complementary to constraining these Dark Matter parameters through a combined analysis.
We present measurements of light and charge signals in a dual-phase time projection chamber at electric fields varying from 10 V/cm up to 500 V/cm and at zero field using 511 keV gamma rays from a ...22Na source. We determine the drift velocity, electron lifetime, diffusion constant, and light and charge yields at 511 keV as a function of the electric field. In addition, we fit the scintillation pulse shape to an effective exponential model, showing a decay time of 43.5 ns at low field that decreases to 25 ns at high fields.
Abstract
A characterisation of the Timepix4 pixel front-end with a
strong focus on timing performance is presented. Externally
generated test pulses were used to probe the per-pixel
time-to-digital ...converter (TDC) and measure the time-bin sizes by
precisely controlling the test-pulse arrival time in steps of
10 ps. The results indicate that the TDC can achieve a time
resolution of 60 ps, provided that a calibration is performed to
compensate for frequency variation in the voltage controlled
oscillators of the pixel TDCs. The internal clock distribution
system of Timepix4 was used to control the arrival time of
internally generated analog test pulses in steps of about
20 ps. The analog test pulse mechanism injects a controlled amount
of charge directly into the analog front-end (AFE) of the pixel, and
was used to measure the time resolution as a function of signal
charge, independently of the TDC. It was shown that for the default
configuration, the AFE time resolution in the hole-collecting mode
is limited to 105 ps. However, this can be improved up to about
60 ps by increasing the preamplifier bias-current at the cost of
increased power dissipation. For the electron-collecting mode, an
AFE time resolution of 47 ps was measured for a bare Timepix4
device at a signal charge of 21 ke. It was observed that additional
input capacitance from a bonded sensor reduces this figure to
62 ps.
Monte Carlo (MC) methods can accurately simulate scatter in X-ray imaging. However, when low noise scatter projections have to be simulated these MC simulations tend to be very time consuming. Rapid ...computation of scatter estimates is essential for several applications. The aim of the work presented in this paper is to speed up the estimation of noise-free scatter projections while maintaining their accuracy. Since X-ray scatter projections are often rather smooth, an approach is chosen whereby a short MC simulation is combined with a data fitting program that is robust to projection truncation and noise. This method allows us to estimate the smooth scatter projection rapidly. The speed-up and accuracy achieved by using the fitting algorithm were validated for the projection simulation of a small animal X-ray CT system. The acceleration that can be obtained over standard MC simulations is typically two orders of magnitude, depending on the accuracy required. The proposed approach may be useful for rapid simulation of patient and animal studies and for correction of the image-degrading effects of scatter in tomography.
We performed a detailed study of the timing performance of the LHCb VELO Timepix3 Telescope with a 180 GeV/c mixed hadron beam at the CERN SPS. A twofold method was developed to improve the ...resolution of single-plane time measurements, resulting in a more precise overall track time measurement. The first step uses spatial information of reconstructed tracks in combination with the measured signal charge in the sensor to correct for a mixture of different effects: variations in charge carrier drift time; variations in signal induction, which are the result of a non-uniform weighting field in the pixels; and lastly, timewalk in the analog front-end. The second step corrects for systematic timing offsets in Timepix3 that vary from −2 to 2 ns. By applying this method, we improved the track time resolution from 438(16) ps to 276(4) ps.
Abstract
Monte Carlo simulations are a crucial tool for the analysis and prediction of various background components in liquid xenon (LXe) detectors. With improving shielding in new experiments, the ...simulation of external backgrounds, such as induced by gamma rays from detector materials, gets more computationally expensive. We introduce and validate an accelerated Monte Carlo simulation technique for photon transport in liquid xenon detectors. The method simulates photon-induced interactions within a defined geometry and energy range with high statistics while interactions outside of the region of interest are not simulated directly but are taken into account by means of probability weights. For a simulation of gamma-induced backgrounds in an exemplary detector geometry we achieve a three orders of magnitude acceleration compared to a standard simulation of a current ton-scale LXe dark matter experiment.
We present measurements of the scintillation pulse shape in liquid xenon for nuclear recoils (NR) and electronic recoils (ER) at electric fields of 0 to 0.5 kV/cm for energies <15 keV and <70 keV ...electron-equivalent, respectively. The average pulse shapes are well-described by an effective model with two exponential decay components, where both decay times are fit parameters. We find significant broadening of the pulse for ER due to delayed luminescence from the recombination process. In addition to the effective model, we fit a model describing the recombination luminescence for ER at zero field and obtain good agreement. We estimate the best performance of a combined S2/S1 and pulse shape ER/NR discrimination and show that even with 2 ns time resolution, the improvement over S2/S1 discrimination alone is marginal, so that pulse shape discrimination will likely not be useful for future dual-phase liquid xenon experiments looking for elastic dark matter recoil interactions.
We discuss the consequences of the quantum uncertainty on the spectrum of the electron emitted by the beta-processes of a tritium atom bound to a graphene sheet. We analyze quantitatively the issue ...recently raised by Cheipesh, Cheianov, and Boyarsky Phys. Rev. D 104, 116004 (2021), and discuss the relevant timescales and the degrees of freedom that can contribute to the intrinsic spread in the electron energy. We perform careful calculations of the potential between tritium and graphene with different coverages and geometries. With this at hand, we propose possible avenues to mitigate the effect of the quantum uncertainty.
Abstract
Test beam measurements have been carried out with a 3D sensor on a Timepix3 ASIC and the time measurements are presented. The measurements are compared to those of a thin planar sensor on ...Timepix3. It is shown that for a perpendicularly incident beam the time resolution of both detectors is dominated by the Timepix3 front-end. The 3D detector is dominated by the time-to-digital conversion whereas the analog front-end jitter also gives a significant contribution for the thin planar detector. The 3D detector reaches an overall time resolution of 567 ± 6 ps compared to 683 ± 8 ps for the thin planar detector. For a grazing angle beam, however, the thin planar detector achieves a better time resolution because it has a lower pixel capacitance, and therefore suffers less from jitter in the analog front-end for the low charge signals that mainly occur in this type of measurement. Finally, it is also shown that the 3D and thin planar detector can achieve time resolutions for large clusters of about 100 ps and 250 ps, respectively, by combining many single hit measurements.
Abstract
The PTOLEMY transverse drift filter is a new concept to
enable precision analysis of the energy spectrum of electrons near
the tritium
β
-decay endpoint. This paper details the
...implementation and optimization methods for successful operation of
the filter for electrons with a known pitch angle. We present the
first demonstrator that produces the required magnetic field
properties with an iron return-flux magnet. Two methods for the
setting of filter electrode voltages are detailed. The challenges of
low-energy electron transport in cases of low field are discussed,
such as the growth of the cyclotron radius with decreasing magnetic
field, which puts a ceiling on filter performance relative to fixed
filter dimensions. Additionally, low pitch angle trajectories are
dominated by motion parallel to the magnetic field lines and
introduce non-adiabatic conditions and curvature drift. To minimize
these effects and maximize electron acceptance into the filter, we
present a three-potential-well design to simultaneously drain the
parallel and transverse kinetic energies throughout the length of
the filter. These optimizations are shown, in simulation, to achieve
low-energy electron transport from a 1 T iron core (or 3 T
superconducting) starting field with initial kinetic energy of
18.6 keV drained to < 10 eV (< 1 eV) in about 80 cm. This
result for low field operation paves the way for the first
demonstrator of the PTOLEMY spectrometer for measurement of
electrons near the tritium endpoint to be constructed at the Gran
Sasso National Laboratory (LNGS) in Italy.
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