Mjerni sustav za istraživanje krajnje energije u β+-raspadu

We describe an experimental arrangement for the investigation of β+-decay end-point energies based on the use of a surface barrier silicon detector for β-particles and two Ge(HP) detectors for photons in a three-axes detection geometry. The system was tested using a 58Co source. The positron end-point energy determined by the Fermi plot analysis of the experimental data was found to be in good agreement with the values quoted in the literature.Opisujemo mjerni sustav za istraživanje krajnje enegije u β+-raspadu zasnovan na upotrebi površinskog silicijskog detektora za β+-čestice i dvaju Ge detektora visoke čistoće za fotone, u trokrakom razmještaju. Sustav smo ispitali pomoću izvora 58Co. Krajnju energiju pozitrona odredili smo analizom mjernih podataka primjenom Fermijevog dijagrama, i ustanovili dobro slaganje s ranije objavljenim vrijednostima

CAST constraints on the axion-electron coupling

In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axiorecombination, the "BCA processes." Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling gae and axion-photon interaction strength ga using the CAST phase-I data (vacuum phase). For ma <~ 10 meV/c2 we find ga gae < 8.1 × 10−23 GeV−1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivity into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission

An update on the Axion Helioscopes front: current activities at CAST and the IAXO project

Although they have not yet been detected, axions and axion-like particles (ALPs) continue to maintain the interest (even increasingly so) of the rare-event searches community as viable candidates for the Dark Matter of the Universe but also as a solution for several other puzzles of astrophysics. Their property of coupling to photons has inspired different experimental methods for their detection, one of which is the helioscope technique. The CERN Axion Solar Telescope (CAST) is the most sensitive helioscope built up to date and has recently published part of the latest data taken with the magnet bores gradually filled with 3He, probing the mass range up to 1.17 eV. The International AXion Observatory (IAXO) is being proposed as a facility where different axion studies can be performed, with the primary goal to study axions coming from the Sun. Designed to maximize sensitivity, it will improve the levels reached by CAST by almost 5 orders of magnitude in signal detection, that is more than one order of magnitude in terms of gaγ. Here we will summarize the most important aspects of the helioscopes, and focus mainly on IAXO, based on the recent papers [1, 2]