Comparative Analysis of the Mechanisms of Fast Light Particle Formation in Nucleus-Nucleus Collisions at Low and Intermediate Energies

The dynamics and the mechanisms of preequilibrium-light-particle formation in nucleus-nucleus collisions at low and intermediate energies are studied on the basis of a classical four-body model. The angular and energy distributions of light particles from such processes are calculated. It is found that, at energies below 50 MeV per nucleon, the hardest section of the energy spectrum is formed owing to the acceleration of light particles from the target by the mean field of the projectile nucleus. Good agreement with available experimental data is obtained.Comment: 23 pages, 10 figures, LaTeX, published in Physics of Atomic Nuclei v.65, No. 8, 2002, pp. 1459 - 1473 translated from Yadernaya Fizika v. 65, No. 8, 2002, pp. 1494 - 150

Study on the reusability of fluorescent nuclear track detectors using optical bleaching

Fluorescent nuclear track detectors (FNTDs) based on Al${_2}$O${_3}$:C,Mg crystals are luminescent detectors that can be used for dosimetry and detection of charged particles and neutrons. These detectors can be utilised for imaging applications where a reasonably high track density, approximately of the order of 1 $\times$ $10^4$ tracks in an area of 100 $\times$ 100 $\mu$m$^2$, is required. To investigate the reusability of FNTDs for imaging applications, we present an approach to perform optical bleaching under the required track density conditions. The reusability was assessed through seven irradiation-bleaching cycles. For the irradiation, the studied FNTD was exposed to alpha-particles from an $^{241}$Am radioactive source. The optical bleaching was performed by means of ultraviolet laser light with a wavelength of 355 nm. Three dedicated regions on a single FNTD with different accumulated track densities and bleaching conditions were investigated. After every irradiation-bleaching cycle, signal-to-noise ratio was calculated to evaluate FNTD performance. It is concluded that FNTDs can be reused at least seven times for applications where accumulation of a high track density is required

Multipolar model of bremsstrahlung accompanying proton-decay of nuclei

Emission of bremsstrahlung photons accompanying proton decay of nuclei is studied. The new improved multipolar model describing such a process is presented. The angular formalism of calculations of the matrix elements is stated in details. The bremsstrahlung probabilities for the $^{157}{\rm Ta}$, $^{161}{\rm Re}$, $^{167}{\rm Ir}$ and $^{185}{\rm Bi}$ nuclei decaying from the $2s_{1/2}$ state, the $^{109}_{53}{\rm I}_{56}$ and $^{112}_{55}{\rm Cs}_{57}$ nuclei decaying from the $1d_{5/2}$ state, the $^{146}_{69}{\rm Tm}_{77}$ and $^{151}_{71}{\rm Lu}_{80}$ nuclei decaying from the $0h_{11/2}$ state are predicted. Such spectra have orders of values similar to the experimental data for the bremsstrahlung photons emitted during the $\alpha$-decay. This indicates on real possibility to study bremsstrahlung photons during proton decay experimentally and perform further measurements.Comment: 14 pages, 6 figure

Hypernuclear event detection in the nuclear emulsion with Monte Carlo simulation and machine learning

This study developed a novel method for detecting hypernuclear events recorded in nuclear emulsion sheets using machine learning techniques. The artificial neural network-based object detection model was trained on surrogate images created through Monte Carlo simulations and image-style transformations using generative adversarial networks. The performance of the proposed model was evaluated using $\alpha$-decay events obtained from the J-PARC E07 emulsion data. The model achieved approximately twice the detection efficiency of conventional image processing and reduced the time spent on manual visual inspection by approximately 1/17. The established method was successfully applied to the detection of hypernuclear events. This approach is a state-of-the-art tool for discovering rare events recorded in nuclear emulsion sheets without any real data for training.Comment: 32 pages, 13 figure

Non-strange Dibaryon Resonances Observed in the γd→π0π0d\gamma d\to \pi^0\pi^0 d Reaction

Coherent double neutral-pion photoproduction on the deuteron, $\gamma{d}${$\to$}$\pi^0\pi^0{d}$, has been experimentally studied at incident photon energies ranging from 0.75 to 1.15 GeV. The total cross section as a function of the $\gamma{d}$ center-of-mass energy shows resonance-like behavior, which peaks at approximately 2.47 and 2.63 GeV. The measured angular distribution of deuteron emission is rather flat, which cannot be reproduced by the kinematics of quasi-free $\pi^0\pi^0$ production with deuteron coalescence. In $\pi^0d$ invariant-mass distributions, a clear peak is observed at $2.14{\pm}0.01$ GeV$/c^2$ with a width of $0.09{\pm}0.01$ GeV$/c^2$. The spin-parity of this state is restricted to $1^+$, $2^+$ or $3^-$ from the angular distributions of the two $\pi^0$s. The present work shows strong evidence for the existence of an isovector dibaryon resonance with a mass of 2.14 GeV$/c^2$. The $2^+$ assignment is consistent with the theoretically predicted ${\cal{D}}_{12}$ state, and also with the energy dependence of the $\pi{d}$ partial-wave amplitude $^3\!P_2$ for the $\pi^{\pm}d${$\to$}$\pi^{\pm}d$ and $\pi^+d${$\to$}${pp}$ reactions.Comment: 12 pages, 6 figure

An Earth-sized Planet around an M5 Dwarf Star at 22 pc

We report on the discovery of an Earth-sized transiting planet (R p = 1.015 ± 0.051 R ⊕) in a P = 4.02 day orbit around K2-415 (EPIC 211414619), an M5V star at 22 pc. The planet candidate was first identified by analyzing the light-curve data obtained by the K2 mission, and it is here shown to exist in the most recent data from TESS. Combining the light curves with the data secured by our follow-up observations, including high-resolution imaging and near-infrared spectroscopy with IRD, we rule out false-positive scenarios, finding a low false-positive probability of 2 × 10−4. Based on IRD’s radial velocities of K2-415, which were sparsely taken over three years, we obtain a planet mass of 3.0 ± 2.7 M ⊕ (M p < 7.5 M ⊕ at 95% confidence) for K2-415b. Being one of the lowest-mass stars (≈0.16 M ⊙) known to host an Earth-sized transiting planet, K2-415 will be an interesting target for further follow-up observations, including additional radial velocity monitoring and transit spectroscopy

Effects of light environment during growth on the expression of cone opsin genes and behavioral spectral sensitivities in guppies (Poecilia reticulata)

BACKGROUND: The visual system is important for animals for mate choice, food acquisition, and predator avoidance. Animals possessing a visual system can sense particular wavelengths of light emanating from objects and their surroundings and perceive their environments by processing information contained in these visual perceptions of light. Visual perception in individuals varies with the absorption spectra of visual pigments and the expression levels of opsin genes, which may be altered according to the light environments. However, which light environments and the mechanism by which they change opsin expression profiles and whether these changes in opsin gene expression can affect light sensitivities are largely unknown. This study determined whether the light environment during growth induced plastic changes in opsin gene expression and behavioral sensitivity to particular wavelengths of light in guppies (Poecilia reticulata). RESULTS: Individuals grown under orange light exhibited a higher expression of long wavelength-sensitive (LWS) opsin genes and a higher sensitivity to 600-nm light than those grown under green light. In addition, we confirmed that variations in the expression levels of LWS opsin genes were related to the behavioral sensitivities to long wavelengths of light. CONCLUSIONS: The light environment during the growth stage alters the expression levels of LWS opsin genes and behavioral sensitivities to long wavelengths of light in guppies. The plastically enhanced sensitivity to background light due to changes in opsin gene expression can enhance the detection and visibility of predators and foods, thereby affecting survival. Moreover, changes in sensitivities to orange light may lead to changes in the discrimination of orange/red colors of male guppies and might alter female preferences for male color patterns. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12862-016-0679-z) contains supplementary material, which is available to authorized users

WASA-FRS experiments in FAIR Phase-0 at GSI

We have developed a new and unique experimental setup integrating the central part of the Wide Angle Shower Apparatus (WASA) into the Fragment Separator (FRS) at GSI. This combination opens up possibilities of new experiments with high-resolution spectroscopy at forward and measurements of light decay particles with nearly full solid-angle acceptance in coincidence. The first series of the WASA-FRS experiments have been successfully carried out in 2022. The developed experimental setup and two physics experiments performed in 2022 including the status of the preliminary data analysis are introduced