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Register a new userLarge-mass single-electron-resolution detector for dark matter and neutrino elastic interaction searches
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Large mass single-electron-resolution solid state detectors are desirable to search for low mass dark matter candidates and to measure coherent elastic neutrino nucleus scattering (CE$ u$NS). Here, we present results from a novel 100 g phonon-mediated Si detector with a new interface architecture. This detector gives a baseline resolution of $sim 1 e^{-}/h^{+}$ pair and a leakage current on the order of $10^{-16}$ A. This was achieved by removing the direct electrical contact between the Si crystal and the metallic electrode, and by increasing the phonon absorption efficiency of the sensors. The phonon signal amplification in the detector shows a linear increase while the signal to noise ratio improves with bias voltage, up to 240 V. This feature enables the detector to operate at a low energy threshold which is beneficial for dark matter and CE$ u$NS like searches.
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In the near future there will be the request for very large liquid Xenon (LXe) detectors for Dark Matter (DM) searches in the 50-ton range. To avoid an impractically long, single drift space of a dual-phase detector, it seems beneficial to use the single-phase technique. Since electrons then can drift in any direction, we can segment the homogeneous medium and thus avoid an excessive maximum drift path of order 4 m. The shorter detector length has several benefits, e.g. requiring a lower cathode voltage for the same drift field. We can easily split the TPC into two regions with the cathode in the center and two anodes at the top and bottom. One also can use multiple TPCs stacked on top of each other in the same liquid volume to reduce the maximum drift length even further. A further division of the drift space by installing an additional anode in the center would require S2 photons to traverse the liquid for several times the Rayleigh scattering length in LXe, which is only 30 - 40 cm. This seems to be excessive for good x - y localization. We therefore suggest a geometry of two independent TPCs with two drift spaces each. Despite earlier publications concerns persisted about the effect of shadowing. A detailed FEM model of the anode regions shows that with an aligned wire arrangement the drifting electrons impinge sideways on the anode in a narrow angular range of width 15$^{circ}$ - 20$^{circ}$. Most S2 photons are emitted in full view of the close-by PMT array. About 37% of the S2 photons are shadowed by the anode wire out of which 30% will be reflected back again on the gold plating of the wires. Thus we can observe 74% of the total S2 light. Compared to a dual-phase detector, however, we do not suffer from the extraction efficiency, sometimes reported as low as 50%.
We report the first demonstration of a phonon-mediated silicon detector technology that provides a primary phonon measurement in a low-voltage region, and a simultaneous indirect measurement of the ionization signal through Neganov-Trofimov-Luke amplification in a high voltage region, both in a monolithic crystal. We present characterization of charge and phonon transport between the two stages of the detector and the resulting background discrimination capability at low energies. This new detector technology has the potential to significantly enhance the sensitivity of dark matter and coherent neutrino scattering experiments beyond the capabilities of current technologies that have limited discrimination at low energies.
Determination of the neutrino mass hierarchy using a reactor neutrino experiment at $sim$60 km is analyzed. Such a measurement is challenging due to the finite detector resolution, the absolute energy scale calibration, as well as the degeneracies caused by current experimental uncertainty of $|Delta m^2_{32}|$. The standard $chi^2$ method is compared with a proposed Fourier transformation method. In addition, we show that for such a measurement to succeed, one must understand the non-linearity of the detector energy scale at the level of a few tenths of percent.
Muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based $ u_mu$ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to $sim$ 10% due to uncertainties in hadron production and focusing. We have isolated a sample of 135 $pm$ 17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI $ u_mu$ flux from 9% to 6%. Our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.
The detection of low-energy deposition in the range of sub-eV through ionization using germanium (Ge) with a bandgap of $sim$0.7 eV requires internal amplification of charge signal. This can be achieved through high electric field which accelerates charge carriers to generate more charge carriers. The minimum electric field required to generate internal charge amplification is derived for different temperatures. A point contact Ge detector provides extremely high electric field in proximity to the point contact. We show the development of a planar point contact detector and its performance. The field distribution is calculated for this planar point contact detector. We demonstrate the required electric field can be achieved with a point contact detector.
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