CDMS II data from the five-tower runs at the Soudan Underground Laboratory were reprocessed with an improved charge-pulse fitting algorithm. Two new analysis techniques to reject surface-event ...backgrounds were applied to the 612 kg days germanium-detector weakly interacting massive particle (WIMP)-search exposure. An extended analysis was also completed by decreasing the 10 keV analysis threshold to ~5keV, to increase sensitivity near a WIMP mass of 8GeV/c2. After unblinding, there were zero candidate events above a deposited energy of 10 keV and six events in the lower-threshold analysis. This yielded minimum WIMP-nucleon spin-independent scattering cross-section limits of 1.8×10-44 and 1.18×10-41 at 90% confidence for 60 and 8.6GeV/c2 WIMPs, respectively. This improves the previous CDMS II result by a factor of 2.4 (2.7) for 60 (8.6)GeV/c2 WIMPs.
We present the design and characterization of a cryogenic phonon-sensitive 1-gram Si detector exploiting the Neganov-Trofimov-Luke effect to detect single-charge excitations. This device achieved ...2.65(2) eV phonon energy resolution when operated without a voltage bias across the crystal and a corresponding charge resolution of 0.03 electron-hole pairs at 100 V bias. With a continuous-readout data acquisition system and an offline optimum-filter trigger, we obtain a 9.2 eV threshold with a trigger rate of the order of 20 Hz. The detector's energy scale is calibrated up to 120 keV using an energy estimator based on the pulse area. The high performance of this device allows its application to different fields where excellent energy resolution, low threshold, and large dynamic range are required, including dark matter searches, precision measurements of coherent neutrino-nucleus scattering, and ionization yield measurements.
Abstract Previous research suggests that trauma may contribute to psychosis onset. In this study, we examine the effect of parental loss of a child on the onset of psychotic experience using data ...from the National Comorbidity Survey Replication, hypothesizing that child loss will precede the onset of psychosis and will be associated with a later age of onset. We likewise tested this association for six other psychiatric conditions to demonstrate specificity for psychosis. Individuals with a psychotic disorder who had lost a child had a significantly later age of onset, particularly in males, even when controlling for demographic variables and co-occurring substance abuse and psychiatric disorders. Psychosis onset frequently occurred within a year of child loss. No associations were found between child loss and onset of other psychiatric conditions, supporting specificity of the effect on psychosis. The presented findings implicate child loss as an etiological factor in the onset of psychosis, providing converging evidence with previous studies demonstrating associations between more widely studied trauma exposures (abuse, neglect, and assault) and psychosis.
We measured the nuclear-recoil ionization yield in silicon with a cryogenic phonon-sensitive gram-scale detector. Neutrons from a mono-energetic beam scatter off of the silicon nuclei at angles ...corresponding to energy depositions from 4 keV down to 100 eV, the lowest energy probed so far. The results show no sign of an ionization production threshold above 100 eV. In conclusion, these results call for further investigation of the ionization yield theory and a comprehensive determination of the detector response function at energies below the keV scale.
Future direct searches for low-mass dark matter particles with germanium detectors, such as SuperCDMS SNOLAB, are expected to be limited by backgrounds from radioactive isotopes activated by ...cosmogenic radiation inside the germanium. There are limited experimental data available to constrain production rates and a large spread of theoretical predictions. We examine the calculation of expected production rates, and analyze data from the second run of the CDMS low ionization threshold experiment (CDMSlite) to estimate the rates for several isotopes. We model the measured CDMSlite spectrum and fit for contributions from tritium and other isotopes. Using the knowledge of the detector history, these results are converted to cosmogenic production rates at sea level. The production rates in atoms/(kg · day) are 74 ± 9 for 3H, 1.5 ± 0.7 for 55Fe, 17 ± 5 for 65Zn, and 30 ± 18 for 68Ge.
Nuclear-recoil energy scale in CDMS II silicon dark-matter detectors Agnese, R.; Anderson, A.J.; Aramaki, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2018, Letnik:
905, Številka:
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The Cryogenic Dark Matter Search (CDMS II) experiment aims to detect dark matter particles that elastically scatter from nuclei in semiconductor detectors. The resulting nuclear-recoil energy ...depositions are detected by ionization and phonon sensors. Neutrons produce a similar spectrum of low-energy nuclear recoils in such detectors, while most other backgrounds produce electron recoils. The absolute energy scale for nuclear recoils is necessary to interpret results correctly. The energy scale can be determined in CDMS II silicon detectors using neutrons incident from a broad-spectrum 252Cf source, taking advantage of a prominent resonance in the neutron elastic scattering cross section of silicon at a recoil (neutron) energy near 20 (182)keV. Results indicate that the phonon collection efficiency for nuclear recoils is 4.8−0.9+0.7% lower than for electron recoils of the same energy. Comparisons of the ionization signals for nuclear recoils to those measured previously by other groups at higher electric fields indicate that the ionization collection efficiency for CDMS II silicon detectors operated at ∼4V/cm is consistent with 100% for nuclear recoils below 20keV and gradually decreases for larger energies to ∼75% at 100keV. The impact of these measurements on previously published CDMS II silicon results is small.
•The phonon collection efficiency of nuclear recoils is ∼95% that for electron recoils.•The effect on the WIMP-nucleon cross-section exclusion curve is small.•Nuclear-recoil ionization collection decreases from 100% above 20 keV.
Siblings of persons with mental illness who assume primary caregiving roles experience substantial and tangible economic impacts associated with this responsibility. This study investigated mailed ...survey responses collected from 156 adult siblings of persons with mental illness from New York State to examine instrumental costs associated with providing support to siblings with illness. Genders of both siblings, severity of the relatives' mental illness, and number of surviving parents in the family distinguished those occupying primary caregiving responsibility from those not in primary roles. Current caregivers incurred greater instrumental costs in the form of financial expenses, time spent in care activities, and crisis involvement than did those who were not primary care providers. Additional demographic and behavioral factors related to siblings with and without illness were associated with specific dimensions of instrumental expenditure. As siblings become increasingly engaged in caregiving, social service professionals must assume leadership in promoting programs and policies that meaningfully support family involvement for relatives with mental illness.
The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) searches for interactions between dark matter particles and germanium nuclei in cryogenic detectors. The experiment has ...achieved a low energy threshold with improved sensitivity to low-mass (<10 GeV/c2) dark matter particles. We present an analysis of the final CDMSlite dataset, taken with a different detector than was used for the two previous CDMSlite datasets. This analysis includes a data "salting" method to protect against bias, improved noise discrimination, background modeling, and the use of profile likelihood methods to search for a dark matter signal in the presence of backgrounds. We achieve an energy threshold of 70 eV and significantly improve the sensitivity for dark matter particles with masses between 2.5 and 10 GeV/c2 compared to previous analyses. We set an upper limit on the dark matter-nucleon scattering cross section in germanium of 5.4×10-42 cm2 at 5 GeV/c2, a factor of ~2.5 improvement over the previous CDMSlite result.
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