We develop and validate a new algorithm called
primary track recovery
(ptr) that effectively deconvolves known physics and detector effects from nuclear recoil tracks in gas time projection chambers ...(TPCs) with high-resolution readout. This gives access to the primary track charge, length, and vector direction (helping to resolve the “head-tail” ambiguity). Additionally, ptr provides a measurement of the transverse and longitudinal diffusion widths, which can be used to determine the absolute position of tracks in the drift direction for detector fiducialization. Using simulated helium recoils in an atmospheric pressure TPC with a 70:30 mixture of
He:CO
2
we compare the performance of ptr to traditional methods for all key track variables. We find that the algorithm reduces reconstruction errors, including those caused by charge integration, for tracks with mean length-to-width ratios 1.4 and above, corresponding to recoil energies of 20 keV and above in the studied TPCs. We show that ptr improves on existing methods for head-tail disambiguation, particularly for highly inclined tracks, and improves the determination of the absolute position of recoils on the drift axis via transverse diffusion. We find that ptr can partially recover charge structure integrated out by the detector in the
z
direction, but that its determination of energy and length have worse resolution compared to existing methods. We use experimental data to qualitatively verify these findings and discuss implications for future directional detectors at the low-energy frontier.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Mitigation of beam backgrounds via collimators is critical for the success of the Belle II experiment at the SuperKEKB electron-positron collider. We report on an improved simulation methodology, ...which includes a refined physical description of the collimators and beam pipe, our first implementation of collimator tip scattering, and in which the existing beam particle tracking software has been embedded into a new sequential tracking framework. These improvements resolve longstanding discrepancies between measured and predicted Belle II background levels, and significantly reduce the computing time required to optimize the collimation system in simulation. Finally, we report on collimator aperture scans, which confirm the accuracy of the simulation and suggest a new method for aligning the collimators.
Abstract
Directional detection of nuclear recoils is broadly desirable in nuclear and particle physics. At low recoil energies, this capability may be used to confirm the cosmological origin of a ...dark matter signal, to penetrate the so-called neutrino floor, or to distinguish between different neutrino sources. Gas Time Projection Chambers (TPCs) can enable directional recoil detection if the readout granularity is sufficiently high, as is the case when micro-pattern gaseous detectors (MPGDs) are utilized. A key challenge in such detectors is identifying and rejecting background electron recoil events caused by gamma rays from radioactive contaminants in the detector materials and the environment. We define new observables that can distinguish electron and nuclear recoils, even at keV-scale energies, based on the simulated ionization's topology. We perform a simulation study that shows these observables outperform the traditionally used discriminant, d
E
/d
x
, by up to three orders of magnitude. Furthermore, these new observables work well even at ionization energies well below 10keV and remain robust even in the regime where directionality fails.
Status of the Belle silicon vertex detector Natkaniec, Z.; Aihara, H.; Asano, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2006, Letnik:
560, Številka:
1
Journal Article
Recenzirano
The old silicon vertex detector (SVD1) of the Belle detector, operating at the high-luminosity asymmetric energy e+e− collider KEKB, was replaced by an upgraded version (SVD2) in 2003. The new ...detector has modified geometry and redesigned readout electronics, providing a larger polar angle acceptance, better vertex resolution, improved radiation hardness and reduced dead time. The operation of the detector started successfully in October 2003. The basic concepts of the SVD2 design as well as its performance after 10 months of data taking are described in this paper.
Tests of gases in a mini-TPC with pixel chip readout Vahsen, S.; Oliver-Mallory, K.; Lopez-Thibodeaux, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2014, Letnik:
738
Journal Article
Recenzirano
Gases for potential use as targets for directional dark matter detection were tested in a prototype detector using two sequential Gas Electron Multipliers, or GEMs. The sensitive volume consists of a ...mini-TPC of 12cm length and 7.5cm diameter. An FEI3 pixel chip, developed for the ATLAS experiment, was used to produce spatial measurements with high resolution. An Fe55 source produced photoelectrons by X-ray conversions in the sensitive volume, and images of these were recorded by the chip. Spatial resolution plots are shown for the gases, which include the practical electron range of the photoelectrons and the effects of diffusion in the mini-TPC. Avalanche gain and gain resolution measurements were made for the four gases tested, at atmospheric and sub-atmospheric pressures: Ar(70)/CO2(30), CF4, He(80)/CF4(20) and He(80)/isobutane(20).
Directional information in the direct dark matter searches is believed to be able providing a clear discovery of the galactic WIMP dark matter, together with a further potential to investigate the ...properties of the dark matter. CYGNUS is a concept to detect the galactic WIMP dark matter particles with directionality. In this paper, physics motivation and technological R&D status will be reviewed.
We present avalanche gain and associated resolution measurements recorded with a 4He:CO2 (70:30) gas mixture and pure SF6, a Negative Ion (NI) gas. SF6 is of particular interest to the directional ...dark matter detection community, as its low thermal diffusion helps to retain recoil ionization track features over long drift lengths. With the aid of a general form of the reduced first Townsend coefficient (RFTC), multiple GEM-based detector data sets are used to study the high-gain behavior of the 4He:CO2 gas mixture. The high-gain data is well described purely in terms of the reduced electric field strength and the number of GEMs, and the robust relationship between the RFTC and the average, reduced, electric field strength across the GEMs is emphasized. The associated (pulse-height) resolution measurements are used to discuss the variance of the avalanche distribution and to describe and estimate the lower limits of energy resolution one should expect to measure using a simple relationship with the RFTC. In the end, a description of avalanche gain, its effect on energy resolution, and the contributing experimental parameters in GEM-based detectors is developed over a broad parameter space for further use.
The Directional Dark Matter Detector (D3) Vahsen, S.E.; Feng, H.; Garcia-Sciveres, M. ...
EAS publications series,
2012, 2012-00-00, 20120101, Letnik:
53
Journal Article
Gas-filled Time Projection Chambers (TPCs) with Gas Electron Multipliers (GEMs) and pixels appear suitable for direction-sensitive WIMP dark matter searches. We present the background and motivation ...for our work on this technology, past and ongoing prototype work, and a development path towards an affordable, 1-m3-scale directional dark matter detector, D3. Such a detector may be particularly suitable for low-mass WIMP searches, and perhaps sufficiently sensitive to clearly determine whether the signals seen by DAMA, CoGeNT, and CRESST-II are due to low-mass WIMPs or background.
Cosmological observations indicate that most of the matter in the Universe is Dark Matter. Dark Matter in the form of Weakly Interacting Massive Particles (WIMPs) can be detected directly, via its ...elastic scattering off target nuclei. Most current direct detection experiments only measure the energy of the recoiling nuclei. However, directional detection experiments are sensitive to the direction of the nuclear recoil as well. Due to the Sun’s motion with respect to the Galactic rest frame, the directional recoil rate has a dipole feature, peaking around the direction of the Solar motion. This provides a powerful tool for demonstrating the Galactic origin of nuclear recoils and hence unambiguously detecting Dark Matter. Furthermore, the directional recoil distribution depends on the WIMP mass, scattering cross section and local velocity distribution. Therefore, with a large number of recoil events it will be possible to study the physics of Dark Matter in terms of particle and astrophysical properties. We review the potential of directional detectors for detecting and characterizing WIMPs.
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