The radiation environment above the lunar surface is shaped not only by galactic cosmic rays interacting with the regolith, but also by secondary particles produced and transported in the near-surface vacuum region. In this work, Geant4 simulations were performed to investigate the production, transport, and decay of secondary particles above the lunar surface under galactic cosmic-ray background conditions. The model includes a lunar-soil target and a vacuum column extending from the surface up to 50 km altitude, with primary galactic cosmic-ray nuclei generated for a solar modulation potential of 500 MV. The analysis focuses on upward and downward fluence-rate components, electron and positron production mechanisms, and parent-particle contributions. From the near-surface layer to 50 km, the upward fluence rate increases by similar to 25% for electrons and by similar to 69% for positrons. At 1 m above the surface, the downward component represents about 14% of the total electron fluence rate and about 28% of the total positron fluence rate. The production analysis indicates that neutron beta decay is responsible for the low-energy electron component, whereas muon decay produces the higher-energy electron and positron components. Near the surface, kaon decay also provides a non-negligible contribution to local electron-positron production. As a complementary analysis, the annual effective-dose estimates are approximately 1.06 mSv yr-1 for the downward electromagnetic component at 1 m and 2.24 mSv yr-1 for the upward fluence-rate excess at 50 km relative to 1 m. These values characterize only the electromagnetic component produced within the modeled vacuum region and do not represent the total lunar effective dose. Overall, the results show that decays of unstable secondary particles within the vacuum column modify the directional and spectral structure of the electron-positron field between the lunar surface and low altitudes, contributing to a more complete characterization of the secondary-particle environment above the Moon.
A gaseous charged anisotropic compact star model is developed by combining conformal symmetry with near-linear Chaplygin effects. The Chaplygin equation of state is useful in describing behaviour of exotic dark energy that believed to be the source of late accelerated universe expansion. Tolman ansatz is employed with a specific form of electric field to solve the Einstein-Maxwell field equations. Detailed analysis of the physical relativistic conditions is then conducted for model validation. The matter variables satisfy the regularity and energy conditions. The model's stability through adiabatic indexes, equations of state parameters, speed of sound and ratio of mass to central density is satisfied. The balancing of the natural physical forces for equilibrium is obeyed as well. The mass-radius ratio and surface redshift are within acceptable ranges. The generated class of solution regained masses and radii of some well-known observed stars including 4U 1538-52, SMC X-1, and Her X-1. The strategy of employing conformal Killing vector with near-linear Chaplygin effects provides new insights in stellar modelling of relativistic stars.
We investigate whether cosmogenic gamma rays and neutrinos from ultra-high-energy cosmic rays (UHECRs) produced in hadronically active blazars can significantly contribute to the observed spectral energy distribution (SED), and examine the potential of the Cherenkov Telescope Array Observatory (CTAO) to detect and discriminate this component. For four nearest neutrino bright blazars modeled by Rodrigues et al. (2024), specifically AP Librae, TXS 1700+685, PKS 2326-502, and PKS 2345-16, we constrain the UHECR luminosity by requiring that the total emission does not overshoot available multi-wavelength data, assuming acceleration in the optically thin large scale jet, propagate UHECRs through realistic Galactic and extragalactic magnetic fields, and forecast CTAO performance. We find that cosmogenic gamma rays contribute up to about 7.5% of the total gamma-ray emission at the highest energies (1020 eV), and thus remain subdominant in the SED. In contrast, the associated neutrino emission, at approximately 1044 to 1046 erg s-1, offers a robust propagation signature of hadronic acceleration. Our simulations of 50 h CTAO exposures show that the observatory can accurately reconstruct the intrinsic gamma ray spectrum, enabling strong constraints on the hadronic origin and propagation of UHECRs. These results demonstrate the power of combining CTAO gamma-ray measurements with neutrino observations to probe blazar hadronic processes.
Observations of cosmic gamma rays with energies above the 1012 electronvolts (TeV) regime are often a direct probe of events where our theoretical predictions are challenged by extreme conditions. Because high energetic cosmic gamma rays are rare, one needs collection areas with the size of roughly a dozen football fields (105m2) or more to gather significant counting statistics in a short time. The imaging atmospheric Cherenkov telescope detects cosmic gamma rays in such large areas and currently offers the best reconstruction power for the cosmic particle’s type, energy, and direction in particular.However, with only about 1,000hours of dark and clear nights every year, the imaging atmospheric Cherenkov telescope only has a duty cycle of about 12%. To overcome this limitation, we propose a novel imaging atmospheric radio telescope. By observing radio emission in the 10GHz regime from air showers, the imaging atmospheric radio telescope could observe 24/7, independent of the day night cycle, and almost independent of the weather. The novelty here is the high resolution imaging of the air shower’s radio emission which might result in high resolution images as one finds them in imaging atmospheric Cherenkov telescopes. We present a technique to simulate the image formation in the radio telescope using wave mechanics instead of conventional ray tracing. The imaging atmospheric radio telescope could increase our duty-cycle more than eightfold for high energy gamma ray observations. Further, the imaging atmospheric radio telescope might also eightfold the observation power for cosmic neutrinos in the so called Earth-skimming technique.
As SuperCDMS SNOLAB is getting ready to search for low mass dark matter particles, using cryogenic Ge and Si detectors, a set of six of the new SuperCDMS High Voltage (HV) detectors (four Ge and two Si) were tested in the Cryogenic Underground TEst facility (CUTE) at SNOLAB. This provided the first opportunity to gain experience with this new detector type and assess their performance thoroughly under low background conditions. Here we describe the SuperCDMS HV detector concept and discuss some of the newly developed analysis methods and approaches. Focusing on the Ge detectors, we investigate the detector performance under voltage bias (up to 90 V), exercise the low energy (keV to sub-keV range) calibration based on the electron capture peaks generated by the decay of 71Ge, assess the detector resolution, and demonstrate the unexpected (and encouraging) ability of these detectors to also measure high energy interactions in the hundreds of keV range with good resolution (better than 3% at 356 keV).
