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The absolute light yield of a scintillator, defined as the number of scintillation photons produced per unit energy deposited, is a useful quantity for scintillator development, research, and applications. Yet, literature data on the absolute light yield of organic scintillators are limited. The goal of this work is to assess the suitability of the EJ-204 plastic scintillator from Eljen Technology to serve as a reference standard for measurements of the absolute light yield of organic scintillators. Four EJ-204 samples were examined: two manufactured approximately four months prior and stored in high-purity nitrogen, and two aged approximately eleven years and stored in ambient air. The scintillator response was measured using a large-area avalanche photodiode calibrated using low energy $\gamma$-ray and X-ray sources. The product of the quantum efficiency of the photodetector and light collection efficiency of the housing was characterized using an experimentally-benchmarked optical photon simulation. The average absolute light yield of the fresh samples, 9100 $\pm$ 400 photons per MeV, is lower than the manufacturer-reported value of 10400 photons per MeV. Moreover, the aged samples demonstrated significantly lower light yields, deviating from the manufacturer specification by as much as 26\%. These results are consistent with recent work showcasing environmental aging in plastic scintillators and suggest that experimenters should use caution when deploying plastic scintillators in photon counting applications., Comment: 12 pages, 9 figures

In the context of the metric-affine Chern-Simons gravity endowed with projective invariance, we derive analytical solutions for torsion and nonmetricity in the homogeneous and isotropic cosmological case, described by a flat Friedmann-Robertson-Walker metric. We discuss in some details the general properties of the cosmological solutions in the presence of a perfect fluid, such as the dynamical stability and the emergence of big bounce points, and we examine the structure of some specific solutions reproducing de Sitter and power law behaviours for the scale factor. Then, we focus on first-order perturbations in the de Sitter scenario, and we study the propagation of gravitational waves in the adiabatic limit, looking at tensor and scalar polarizations. In particular, we find that metric tensor modes couple to torsion tensor components, leading to the appearance, as in the metric version of Chern-Simons gravity, of birefringence, characterized by different dispersion relations for the left and right circularized polarization states. As a result, the purely tensor part of torsion propagates like a wave, while nonmetricity decouples and behaves like a harmonic oscillator. Finally, we discuss scalar modes, outlining as they decay exponentially in time and do not propagate., version accepted for publication in JCAP

The CKM unitarity precision test of the Standard Model requires a systematic treatment of electromagnetic and strong corrections for semi-leptonic decays. Electromagnetic corrections require the renormalization of a semileptonic four-fermion operator. In this work we calculate the $\mathcal{O}(\alpha\alpha_s)$ perturbative scheme conversion between the $\bar{\rm MS}$ scheme and several momentum-space subtraction schemes, which can also be implemented on the lattice. We consider schemes defined by MOM and SMOM kinematics and emphasize the importance of the choice of projector for each scheme. The conventional projector, that has been used in the literature for MOM kinematics, generates QCD corrections to the conversion factor that do not vanish for $\alpha=0$ and which generate an artificial dependence on the lattice matching scale that would only disappear after summing all orders of perturbation theory. This can be traced to the violation of a Ward identity that holds in tha $\alpha =0$ limit. We show how to remedy this by judicious choices of projector, and prove that the Wilson coefficients in those schemes are free from pure QCD contributions. The resulting Wilson coefficients (and operator matrix elements) have greatly reduced scale dependence. Our choice of the $\bar{\rm MS}$ scheme over the traditional $W$-mass scheme is motivated by the fact that, besides being more tractable at higher orders, unlike the latter it allows for a transparent separation of scales. We exploit this to obtain renormalization-group-improved leading-log and next-to-leading-log strong corrections to the electromagnetic contributions and study the (QED-induced) dependence on the lattice matching scale., Comment: 1+22 pages

Background and aim: On January 9, 2020, the World Health Organization (WHO) declared that Chinese health authorities had identified a new coronavirus strain never before isolated in humans, the 2019-nCoV later redefined SARS-CoV-2, that still today represent a public health problem. The present survey started on 10 February 2020 with the aim of a) assessing the risk perception in healthcare workers and young students, following the evolution of attitudes, perception and knowledge over time, b) provide useful information to the general population during survey. Results: A study sample consisting of 4116 Italian in-dividuals of both sexes was enrolled. High levels of risk perception, low perception of self-efficacy and low levels of knowledge scores (24.55 ± 5.76 SD) were obtained indicating the need for continuous population monitoring as well as further communication strategies carried out at institution levels. Conclusion: The results of the present study could help public health authorities in carrying out informative campaigns for general population and could be an important tool in evaluating public knowledge and misperceptions during the management of the COVID-19. (www.actabiomedica.it).

In recent years, scintillators based on glass matrices proved to be a valid alternative to several crystals; in particular, rare-earth doped silica glasses prepared by sol-gel route using high purity precursors turned out to be suitable materials for the realization of scintillating optical fibers , with application perspectives in real-time medical dosimetry as well as high-energy physics experiments. In this framework, Ce-doped silica fibers have recently been explored as candidates for the dual-readout calorimetry approach, exploiting the simultaneous detection of scintillation and Cherenkov light . A fundamental stage in the scintillation process is the transport to the luminescent centers of free carriers generated upon the interaction between ionizing radiation and the scintillating material; it is often largely affected by the presence of trapping sites, which can capture migrating charge carriers and thus either delay their radiative recombination or decrease the overall scintillation efficiency, according to the characteristics of the traps involved . Although preparation technologies are continuously improved, the presence of a certain amount of lattice defects is very common even for a material synthesized in very controlled conditions. In this work, we study the role of trapping defects and their close interplay with luminescent activators in the recombination processes governing the scintillation emission in 0.05 mol% Ce-doped silica optical fibers. In particular, we present a thorough investigation of the tight correlation existing between delayed scintillation processes and defects acting as carrier traps, as well as of the competition between trapping centers and luminescent ions in free carrier capture. To these purposes, steady-state radio-luminescence as a function of both temperature and cumulated X-ray dose is combined with time-resolved scintillation measurements and wavelength-resolved thermally stimulated luminescence (TSL). The presence of a wide distribution of trap levels, typical of amorphous materials, is revealed and the calculated thermal energies turn out to range from 0.1 eV to 0.8 eV. Besides, the delayed components in the scintillation decay become more intense with increasing temperature and can thus be ascribed to the temperature-dependent recombination of carriers from a progressively increasing portion of the continuous trap distribution. Moreover, a detailed analysis of both scintillation decays and TSL signals puts in evidence the additional occurrence of an athermal tunneling mechanism between traps and luminescent centers. A good agreement between the TSL results and the analysis of the delayed contributions of the scintillation process is thus demonstrated. Therefore, the effectiveness of this investigation approach, previously exploited only for crystalline systems, is demonstrated also in amorphous materials.