Radiation Hardness of Thin Low Gain Avalanche Detectors

Low Gain Avalanche Detectors (LGAD) are based on a n++-p+-p-p++ structure where an appropriate doping of the multiplication layer (p+) leads to high enough electric fields for impact ionization. Gain factors of few tens in charge significantly improve the resolution of timing measurements, particularly for thin detectors, where the timing performance was shown to be limited by Landau fluctuations. The main obstacle for their operation is the decrease of gain with irradiation, attributed to effective acceptor removal in the gain layer. Sets of thin sensors were produced by two different producers on different substrates, with different gain layer doping profiles and thicknesses (45, 50 and 80 um). Their performance in terms of gain/collected charge and leakage current was compared before and after irradiation with neutrons and pions up to the equivalent fluences of 5e15 cm-2. Transient Current Technique and charge collection measurements with LHC speed electronics were employed to characterize the detectors. The thin LGAD sensors were shown to perform much better than sensors of standard thickness (~300 um) and offer larger charge collection with respect to detectors without gain layer for fluences <2e15 cm-2. Larger initial gain prolongs the beneficial performance of LGADs. Pions were found to be more damaging than neutrons at the same equivalent fluence, while no significant difference was found between different producers. At very high fluences and bias voltages the gain appears due to deep acceptors in the bulk, hence also in thin standard detectors

Developing approaches to control SARS-CoV-2 in a public hospital

The Territorial Public Health Care Company (in Italian, ASST) of the Saints Paolo e Carlo of Milano includes two large public hospitals, and several outpatients and territorial healthcare services. It employs 5642 workers. The outbreak of novel coronavirus disease 2019 (COVID-19) reached our ASST in the last week of February when a doctor in the Intensive Care Unit of the San Paolo Hospital was diagnosed with COVID-19. Our Occupational Health Unit immediately introduced measures to control the epidemic. Our approach was based on contact tracing and isolation of asymptomatic infected workers. A \u2018close contact\u2019 was defined as a person who had face-to-face contact or spent at least 15 min in an indoor environment with a positive subject (patient, colleague or relative) without any protective equipment (surgical mask). From 27 February to 23 April we tested 2907 workers (51% of the total workforce) with nasopharyngeal swabs (NPS) using rtPCR for SARS-CoV-2 detection [1,2], with positive results in 152 hospital and 33 territorial workers (3% of the total workforce). All the infected workers were asked to fill in a daily electronic data collection form for the duration of the infection. About 50% remained substantially asymptomatic for the quarantine period, which ended when the workers underwent two NPS on two consecutive days with a negative result. The time to recovery took from 12\u201347 days, with a median duration of about 30 days, which is longer than normally expected. Symptomatic workers showed only very mild symptoms; mainly loss/change of smell and taste. Four were hospitalized but none had severe or life-threatening infection. The data suggest that the \u2018active search approach\u2019 is more effective in closed communities such as groups of healthcare workers than generalized testing. We have started a retrospective survey of 100 positive workers studying symptoms, source of exposure and co-morbidities using a modified version of the \u2018WHO novel coronavirus acute respiratory infection clinical characterization data tool\u2019, administered by telephone interview. Finally, in order to prepare for future outbreaks, we are testing a novel telemedicine approach enabling us to follow quarantined workers with a digital platform with a mobile phone app that provides remote video examinations and online symptoms and health parameter checking (body temperature, oxygen saturation, etc.). The platform facilitates rapid intervention. Using this approach, we can follow a large cohort of workers with continuous monitoring. The tool may also be able to reduce the rate of patients\u2019 hospitalization. We are also comparing those with positive and negative swabs using a rapid immunochromatographic assay for the detection of IgG and IgM antibodies to SARS-CoV-2 virus in whole blood to assess potential immunity. Preliminary results are promising for IgG, even though the protective capacity of this immunoglobulin is still unknown

Assessment of penconazole exposure in winegrowers using urinary biomarkers

Penconazole (PEN) is a fungicide used in agriculture. The aim of this work was to evaluate the exposure to PEN in vineyard workers focusing on urinary biomarkers. Twenty-two agricultural workers were involved in the study; they were investigated during PEN applications and re-entry work, performed for 1-4 consecutive working days, for a total of 42 mixing and applications and 12 re-entries. Potential and actual dermal exposure, including hand exposure, were measured using pads and hand washes. Urine samples were collected starting before the first application, continuing during the work shift, and ending 48\u202fh after the last shift. The determination of PEN in dermal samples and PEN metabolites in urine was performed by liquid chromatography tandem mass spectrometry. Dermal potential body exposure and actual total exposure showed median levels ranging from 18 to 3356\ub5g and from 21 to 111\u202f\ub5g, respectively. Urinary monohydroxyl-derivative PEN-OH was the most abundant metabolite; its excretion rate peaked within 24\u202fh after the work shift. In this period, median concentrations of PEN-OH and the carboxyl-derivative PEN-COOH ranged from 15.6 to 27.6\u202f\ub5g/L and from 2.5 to 10.2\u202f\ub5g/L, respectively. The concentration of PEN-OH during the work shift, in the 24\u202fh after and in the 25-48\u202fh after the work shift were correlated with actual body and total dermal exposure (Pearson's r from 0.279 to 0.562). Our results suggest that PEN-OH in the 24\u202fh post-exposure urine is a promising candidate for biomonitoring PEN exposure in agricultural workers

Gravitational wave radiometry: Mapping a stochastic gravitational wave background

The problem of the detection and mapping of a stochastic gravitational wave background (SGWB), either of cosmological or astrophysical origin, bears a strong semblance to the analysis of CMB anisotropy and polarization. The basic statistic we use is the cross-correlation between the data from a pair of detectors. In order to `point' the pair of detectors at different locations one must suitably delay the signal by the amount it takes for the gravitational waves (GW) to travel to both detectors corresponding to a source direction. Then the raw (observed) sky map of the SGWB is the signal convolved with a beam response function that varies with location in the sky. We first present a thorough analytic understanding of the structure of the beam response function using an analytic approach employing the stationary phase approximation. The true sky map is obtained by numerically deconvolving the beam function in the integral (convolution) equation. We adopt the maximum likelihood framework to estimate the true sky map that has been successfully used in the broadly similar, well-studied CMB map making problem. We numerically implement and demonstrate the method on simulated (unpolarized) SGWB for the radiometer consisting of the LIGO pair of detectors at Hanford and Livingston. We include `realistic' additive Gaussian noise in each data stream based on the LIGO-I noise power spectral density. The extension of the method to multiple baselines and polarized GWB is outlined. In the near future the network of GW detectors, including the Advanced LIGO and Virgo detectors that will be sensitive to sources within a thousand times larger spatial volume, could provide promising data sets for GW radiometry.Comment: 24 pages, 19 figures, pdflatex. Matched version published in Phys. Rev. D - minor change

Characterization of the seismic environment at the Sanford Underground Laboratory, South Dakota

An array of seismometers is being developed at the Sanford Underground Laboratory, the former Homestake mine, in South Dakota to study the properties of underground seismic fields and Newtonian noise, and to investigate the possible advantages of constructing a third-generation gravitational-wave detector underground. Seismic data were analyzed to characterize seismic noise and disturbances. External databases were used to identify sources of seismic waves: ocean-wave data to identify sources of oceanic microseisms, and surface wind-speed data to investigate correlations with seismic motion as a function of depth. In addition, sources of events contributing to the spectrum at higher frequencies are characterized by studying the variation of event rates over the course of a day. Long-term observations of spectral variations provide further insight into the nature of seismic sources. Seismic spectra at three different depths are compared, establishing the 4100-ft level as a world-class low seismic-noise environment.Comment: 29 pages, 16 figure

Improving the sensitivity of future GW observatories in the 1-10 Hz band: Newtonian and seismic noise

The next generation gravitational wave interferometric detectors will likely be underground detectors to extend the GW detection frequency band to frequencies below the Newtonian noise limit. Newtonian noise originates from the continuous motion of the Earth’s crust driven by human activity, tidal stresses and seismic motion, and from mass density fluctuations in the atmosphere. It is calculated that on Earth’s surface, on a typical day, it will exceed the expected GW signals at frequencies below 10 Hz. The noise will decrease underground by an unknown amount. It is important to investigate and to quantify this expected reduction and its effect on the sensitivity of future detectors, to plan for further improvement strategies. We report about some of these aspects. Analytical models can be used in the simplest scenarios to get a better qualitative and semi-quantitative understanding. As more complete modeling can be done numerically, we will discuss also some results obtained with a finite-element-based modeling tool. The method is verified by comparing its results with the results of analytic calculations for surface detectors. A key point about noise models is their initial parameters and conditions, which require detailed information about seismic motion in a real scenario. We will describe an effort to characterize the seismic activity at the Homestake mine which is currently in progress. This activity is specifically aimed to provide informations and to explore the site as a possible candidate for an underground observatory. Although the only compelling reason to put the interferometer underground is to reduce the Newtonian noise, we expect that the more stable underground environment will have a more general positive impact on the sensitivity.We will end this report with some considerations about seismic and suspension noise

Dark Matter Capture in the First Stars: a Power Source and Limit on Stellar Mass

The annihilation of weakly interacting massive particles can provide an important heat source for the first (Pop. III) stars, potentially leading to a new phase of stellar evolution known as a "Dark Star". When dark matter (DM) capture via scattering off of baryons is included, the luminosity from DM annihilation may dominate over the luminosity due to fusion, depending on the DM density and scattering cross-section. The influx of DM due to capture may thus prolong the lifetime of the Dark Stars. Comparison of DM luminosity with the Eddington luminosity for the star may constrain the stellar mass of zero metallicity stars; in this case DM will uniquely determine the mass of the first stars. Alternatively, if sufficiently massive Pop. III stars are found, they might be used to bound dark matter properties.Comment: 19 pages, 4 figures, 3 Tables updated captions and graphs, corrected grammer, and added citations revised for submission to JCA

Snowmass CF1 Summary: WIMP Dark Matter Direct Detection

As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader Particle Physics community to produce this document. The charge to CF1 was (a) to summarize the current status and projected sensitivity of WIMP direct detection experiments worldwide, (b) motivate WIMP dark matter searches over a broad parameter space by examining a spectrum of WIMP models, (c) establish a community consensus on the type of experimental program required to explore that parameter space, and (d) identify the common infrastructure required to practically meet those goals.Comment: Snowmass CF1 Final Summary Report: 47 pages and 28 figures with a 5 page appendix on instrumentation R&