Michael Finger Jr

Results from the OSQAR photon-regeneration experiment : No light shining through a wall

A new method to amplify the photon-axion conversions in a magnetic field is proposed using a buffer gas at a specific pressure in a photon-regeneration experiment. As a first result, new bounds for mass and coupling constant for laboratory experiments aiming to detect any hypothetical scalars and pseudoscalars, which can couple to photons were obtained, excluding with 95% confidence level, the recently withdrawn PVLAS result.

Multilayer Scintillator Responses for Mo Observatory of Neutrino Experiment Studied Using a Prototype Detector MOON-1

An ensemble of multilayer scintillators is discussed as an option of the high-sensitivity detector MOON (Mo Observatory of Neutrinos) for spectroscopic measurements of neutrinoless double beta decays. A prototype detector MOON-1, which consists of 6-layer plastic scintillator plates, was built to study the photon responses of the MOON-type detector. The photon responses, i.e., the number of scintillation photons collected and the energy resolution, which are key elements for high-sensitivity experiments, are found to be 1835 � 30 photoelectrons for 976 keV electrons and � ¼ 2:9 � 0:1% (� E=E ¼ 6:8 � 0:3% in FWHM) at the Q�� � 3 MeV region, respectively. The multilayer plastic scintillator structure with high energy resolution as well as a good signal for the background suppression of � –� rays is crucial for the MOON-type detector to achieve inverted-hierarchy neutrino-mass sensitivity. It will also be useful for medical and other rare-decay experiments as well.

Cosmic ray study by means of reflected EAS Cherenkov light method with the SPHERE-2 detector

The approach to cosmic ray (CR) study with reflected optical Vavilov-Cherenkov radiation (Cherenkov light) was proposed long ago. At present the SPHERE-2 detector is the only existing apparatus that have detected a significant sample of extensive air showers (EAS) by means of this method. At the same time the recorded data allows detailed reconstruction of EAS lateral distribution function (LDF) used to study primary CR mass composition. We report on the status and results of the SPHERE experiment with the emphasis on the peculiarities of the reflected Cherenkov light technique. Detector response simulation was performed by means of full direct Monte Carlo simulation with account of realistic background and noise patterns recorded during the observational runs. Instrumental acceptance was simulated for various energies, charge numbers and zenith angles of primary nuclei. Primary energy of observed showers was estimated with a typical statistical uncertainty 10-20% depending on the primary nucleus parameters. The typical systematic uncertainty of the estimated energy vs the primary charge number was found to be below 3%. The primary all-nuclei spectrum was reconstructed. The fraction of light nuclei vs energy in the energy range 10-100 PeV was estimated by means of an event-by-event approach using the LDF steepness parameter.

Detector for the ultrahigh energy cosmic rays composition study in Antarctica

The main purpose of the Sphere–Antarctica project is connected to the fundamental problems of the cosmic ray physics and general astrophysics - the determination of the energy and mass composition of cosmic ray particles of ultra high and extremely high energies 1018 − 1020 eV. In the energy region above 6 1019 eV modern experiments (Telescope Array and Pierre Auger Observatory) observed anisotropy and the clustering of arrival directions of cosmic rays in some areas. The scientific importance of this problem stems from the lack of generally accepted acceleration mechanism of the CR particles above 3 1018 eV, the unknown nature of the sources of such particles, the inconsistencies of the results of major experiments in the part of the mass of CR composition and the discrepancy of experimental and model data. Scientific novelty of this project is in the methodology registration of the extensive air showers over a large area ~ 600 km2 from an altitude 30 km, that allows to measure the two optical components of the shower Vavilov–Cherenkov radiation and fluorescence light by the same SiPM sensitive elements of the detector simultaneously.