RESUMEN
We present an apparatus for detection of cyclotron radiation yielding a frequency-based ß^{±} kinetic energy determination in the 5 keV to 2.1 MeV range, characteristic of nuclear ß decays. The cyclotron frequency of the radiating ß particles in a magnetic field is used to determine the ß energy precisely. Our work establishes the foundation to apply the cyclotron radiation emission spectroscopy (CRES) technique, developed by the Project 8 Collaboration, far beyond the 18-keV tritium endpoint region. We report initial measurements of ß^{-}'s from ^{6}He and ß^{+}'s from ^{19}Ne decays to demonstrate the broadband response of our detection system and assess potential systematic uncertainties for ß spectroscopy over the full (MeV) energy range. To our knowledge, this is the first direct observation of cyclotron radiation from individual highly relativistic ß's in a waveguide. This work establishes the application of CRES to a variety of nuclei, opening its reach to searches for new physics beyond the TeV scale via precision ß-decay measurements.
RESUMEN
The absolute scale of the neutrino mass plays a critical role in physics at every scale, from the subatomic to the cosmological. Measurements of the tritium end-point spectrum have provided the most precise direct limit on the neutrino mass scale. In this Letter, we present advances by Project 8 to the cyclotron radiation emission spectroscopy (CRES) technique culminating in the first frequency-based neutrino mass limit. With only a cm^{3}-scale physical detection volume, a limit of m_{ß}<155 eV/c^{2} (152 eV/c^{2}) is extracted from the background-free measurement of the continuous tritium beta spectrum in a Bayesian (frequentist) analysis. Using ^{83m}Kr calibration data, a resolution of 1.66±0.19 eV (FWHM) is measured, the detector response model is validated, and the efficiency is characterized over the multi-keV tritium analysis window. These measurements establish the potential of CRES for a high-sensitivity next-generation direct neutrino mass experiment featuring low background and high resolution.
RESUMEN
The pathogenicity of a clinical isolate of Cladosporium sphaerospermum was determined in a murine model. BALB/c mice were given two intraperitoneal injections of 150 mg/kg cyclophosphamide or normal saline on days 4 and 1 preinoculation, and were then challenged with 0.2 ml of C. sphaerospermum inoculum (2 × 10(7) CFU/ml) by topical application on an abrasive wound or by subcutaneous or intravenous injection. Histopathology and inverse fungal culture were performed on the skin lesions and viscera, and pulmonary fungal burden was also determined. Inoculated skin developed localized infections after dermabrasive or subcutaneous challenge in all mice, but the maximum area and number of positive cultures from skin lesions were higher for immunocompromised mice. In the intravenously inoculated mice, all immunocompetent animals survived for the 4-week period of the experiment, while 60% of immunocompromised animals died by 5 days postinoculation. The incidence of disseminated infection and the pulmonary fungal burden of immunosuppressed mice were higher than those of immunocompetent animals. Cutaneous and systemic infections can be established by subcutaneous and intravenous challenge with C. sphaerospermum in BALB/c mice, with the lungs being the most susceptible tissue in systemic infection.