The conjecture of Bodmer–Witten–Terazawa suggesting a form of quark matter (Strange Quark Matter) as the ground state of hadronic interactions has been studied in laboratory and astrophysical ...contexts by a large number of authors. If strange stars exist, some violent events involving these compact objects, such as mergers and even their formation process, might eject some strange matter into the interstellar medium that could be detected as a trace signal in the cosmic ray flux. To evaluate this possibility, it is necessary to understand how this matter in bulk would fragment in the form of strangelets (small lumps of strange quark matter in which finite effects become important). We calculate the mass distribution outcome using the statistical multifragmentation model and point out several caveats affecting it. In particular, the possibility that strangelets fragmentation will render a tiny fraction of contamination in the cosmic ray flux is discussed.
The ARAPUCA concept has been proposed as a simple and neat solution for increasing the effective collection area of SiPMs through the shifting and trapping of scintillation light in noble liquids, ...thus with great potential for improving timing and calorimetry resolution in neutrino and dark matter search experiments using time projection chambers. It is expected to achieve a single photon detection efficiency larger than 1%. The initial design consists of a box made of highly reflective internal surface material and with an acceptance window for photons composed of two shifters and a dichroic filter. The first shifter converts liquid argon scintillation VUV light to a photon of wavelength smaller than the dichroic cutoff, so the surface is highly transparent to it. When passing through the dichroic filter, it reaches the second shifter which allows the photon to be shifted to the visible region and be detected by the SiPM nested inside it. When it enters the box, the photon will likely reflect a few times, including on the dichroic filter surface, before being detected. We present a full numerical description of the device using a Monte Carlo framework, including characterization of the acceptance window, models of reflection of different materials, and sensor quantum efficiency, that can now be used to further improve the detection efficiency by comparing different geometries, positions of SiPM and materials. Estimates of simulated efficiencies, number of reflections and acquisition time are presented and compared to analytical calculations. Those are very promising results, giving a total efficiency for the detection of scintillation light in liquid argon of 1.7±0.3%. Comparison of the estimated total efficiency with a preliminary result from an experimental test with an ARAPUCA prototype made in Brazil is also presented.
O conhecimento das estrelas avançou de maneira fundamental no último século, sendo que hoje podemos descrever os processos envolvidos em seu nascimento, evolução e morte. No entanto, a transposição ...do conhecimento científico estelar para a sala de aula não foi feita de maneira ampla ou tem sido feita em geral de forma fragmentada e parcial. Apresentamos aqui um levantamento sobre os trabalhos desenvolvidos nas últimas décadas para o ensino de Astrofísica Estelar (focado no material disponível em língua portuguesa) de modo a organizar e facilitar o trabalho da ampliação da abordagem deste tópico junto a estudantes, em particular no ensino básico, além de algumas sugestões de aplicações que poderão enriquecer o trabalho dos professores. Apresentamos também uma avaliação crítica do panorama dentro do ensino brasileiro.
Our knowledge about stars has fundamentally advanced over the last century and today we can describe the processes involved in their birth, evolution and death. However, the transposition of stellar scientific knowledge into the classroom has not been done in a broad way or has been done in general in a fragmented and partial way. We present here a survey of the work developed in recent decades for the teaching of Stellar Astrophysics (focused on the material available in Portuguese) in order to organize and facilitate the work of expanding the approach to this topic with students, particularly in basic education, in addition to some suggestions for applications that could enrich the work of teachers. We also present a critical assessment of the panorama within Brazilian education.
PDF
