Abstract: This note reviews the role of superallowed transitions in determining the strength of the weak interaction among the lightest quarks and in searching for new physics beyond the standard electroweak model. The two sets of superallowed decays in nuclei considered here are pure Fermi and mirror transitions. The first have been scrutinized for more than 50 years. The most relevant results are presented and the role of the nucleus-dependent radiative correction and nucleus-independent inner radiative correction are reviewed. In this context, the systematic study of mirror transitions started about 15 years ago. Despite the significant progress made since then, the data is still limited by experimental uncertainties. Combining the results from all superallowed transitions, which are fully consistent, provides a test of unitarity of the first row of the Cabibbo-Kobayashi-Maskawa matrix, which displays a 2 sigma tension with the standardmodel.Superallowed transitions in beta decay are considered to be the “cleanest” ones in terms of hadronic contributions arising from the nuclear medium. These transitions have been identified since the early days in the study of beta decay and have played a crucial role in determining the strength of weak processes involving the lightest u and d quarks. They offer today a sensitive window to search for NP through high precision measurements. This paper reviews the contributions of pure Fermi and mirror superallowed transitions, to determine parameters within the SMor to constrain NP. It relies in particular on the results of four recent reviews and global analyses which can be found in Refs. [1-4]. Although neutron decay is the simplest mirror transition, the recent progress in neutron decay is not covered here besides mentioning the most relevant results.

Abstract: Light sources that emit repetitive subnanosecond pulses are used in neutrino telescopes for time calibration. Optical pulses with an ultra-narrow (subnanosecond) width can replicate the light produced by neutrino interactions, and are an important calibration and test element. By measuring the time-of-flight of the light, it is possible to provide a relative time calibration for all the detector photomultipliers. This work presents the ultra-narrow time optical pulse emitter based on a laser (UNTOPEL), an instrument emitting ultra-short laser optical pulses with a duration of 500 ps, energies per pulse of four microjoules at a wavelength of 532 nm, and a timing precision of 400 ps. The UNTOPEL pulse intensity can be fine-tuned, which is a novelty and a significant advantage in those applications that need to illuminate light detectors located at different distances with the same light intensity. The UNTOPEL pulse intensity can be controlled remotely, allowing for its use in operating conditions where physical access is impossible or difficult. Moreover, it is easy to operate and can be easily controlled through an inter-integrated circuit bus. The UNTOPEL is a sound instrument used when subnanosecond pulses and variable energy emissions are needed.

Abstract: The magnetostatic field of a finite solenoid with infinitely thin walls carrying a dc current oriented in the azimuthal direction is calculated everywhere in space in terms of complete elliptic integrals by direct integration of the Biot-Savart law. The solution is particularized near the solenoid axis and in the midplane perpendicular to the axis obtaining expressions that agree with some typical approximations that are made in introductory courses of electromagnetism or in the technical literature. The range of validity of these approximations has been studied comparing them with the obtained general expression.