Search

The immersed boundary method has emerged as an efficient approach for the simulation of finite-sized solid particles in complex fluid flows. However, one of the well known shortcomings of the method is the limited support for the simulation of light particles, i.e. particles with a density lower than that of the surrounding fluid, both in terms of accuracy and numerical stability. Although a broad literature exists, with several authors reporting different approaches for improving the stability of the method, most of these attempts introduce extra complexities and are very costly from a computational point of view. In this work, we introduce an effective force stabilizing technique, allowing to extend the stability range of the method by filtering spurious oscillations arising when dealing with light-particles, pushing down the particle-to-fluid density ratio as low as 0.04. We thoroughly validate the method comparing with both experimental and numerical data available in literature.

Co-granulation of teawaste with limestone was investigated using sodium-based lignosulfonate as a binder. A quality by design (QbD) approach was employed to formulate models for predicting the granule mean size, granule strength, limestone and binder uniformity from the process, and formulation variables. The results showed that teawaste volume fraction and liquid to solid ratio had a greater effect than other variables on granule mean size. Increasing teawaste in a binary mixture had a negative effect on granule mean size but positive effect on granule tensile strength. Limestone and binder uniformity could be increased by using higher impeller speed. DEM simulation showed that the impeller speed had a significant effect on the mixing quality and light particle fraction could significantly affect the fluctuation of the mixing index at the equilibrium stage. X-ray micro-computer tomography was applied as a technique to see the internal structure of the granules produced.

We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $$\upmu ^+ \rightarrow \mathrm {e}^+\mathrm {X}, \mathrm {X} \rightarrow \upgamma \upgamma \ $$ μ + → e + X , X → γ γ . This search uses a dataset resulting from $$7.5\times 10^{14}$$ 7.5 × 10 14 stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c$$^2$$ 2 for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c$$^2$$ 2 , down to $${\mathcal {O}}(10^{-11})$$ O ( 10 - 11 ) at 90% confidence level.

Angular correlation spectra of ${e}^{+}{e}^{\ensuremath{-}}$ pairs produced in the $^{3}\mathrm{H}(p,{e}^{+}{e}^{\ensuremath{-}})^{4}\mathrm{He}$ nuclear reaction have been studied at ${E}_{p}=510$, 610, and 900 keV proton energies. The main features of the spectra can be understood by taking into account the internal and external pair creations following the proton capture by $^{3}\mathrm{H}$. However, these processes cannot account for an observed peak around ${115}^{\ensuremath{\circ}}$ in the angular correlation spectra. This anomalous excess of ${e}^{+}{e}^{\ensuremath{-}}$ pairs can be described by the creation and subsequent decay of a light particle during the direct capture process. The derived mass of the particle is ${m}_{\mathrm{X}}{c}^{2}=16.94\ifmmode\pm\else\textpm\fi{}0.12(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.21(\mathrm{syst})$ MeV. According to the mass this is likely the same X17 particle, which we recently suggested [Phys. Rev. Lett. 116, 042501 (2016)] for describing the anomaly observed in the decay of $^{8}\mathrm{Be}$.

149Tb, 152Tb, 155Tb and 161Tb can cover all the modalities of diagnostic and therapeutic purposes of nuclear medicine. The production cross sections and yields of radiotheragnostics terbium from x+152,154,155,156,157,158,160Gd reactions in the energy range 0.001 to 200 MeV are evaluated using TALYS1.9. Some p,d,he3-induced reactions show high yields to produce 149Tb while several p,d,t-induced reactions show larger yields to produce 152Tb. For 155Tb productions, number of p,t-induced reactions have higher production yields. To produce 161Tb, one deuteron and one triton induced reaction show bigger production yields. These calculations are compared with EMPIRE 3.2.2 and TENDL-2017 data for prospective reactions.

The neutrino hypothesis resolved a major puzzle in physics and rescued the sacred principle of energy conservation in physics. But is the neutrino a real particle or just an artifice to satisfy our minds? If the particle were never discovered, it would remain an enigma, and to be sure, there was a lot of skepticism about the neutrino idea. For one thing, according to Pauli’s idea, the neutrino resides inside the nucleus, but how a light particle can stay hidden inside the nucleus was a mystery.

We consider the two Higgs doublet model (2HDM) along with a generation of vector-like lepton doublet and singlet to explain the observed discrepancies in the electron and muon anomalous magnetic moments. The type-X (lepton-specific) 2HDM can allow a light pseudo-scalar which is known to explain the muon anomalous magnetic moment at two-loop. Such a light particle induces a sizable negative contribution to the electron anomalous magnetic moment at one-loop in the presence of vector-like leptons evading all the experimental constraints., Comment: v1: 20 pages, 5 figures. v2: matches the version to appear in JHEP

This paper describes a novel, to the best of our knowledge, approach to build ultrastable interferometers using commercial mirror mounts anchored in an ultralow expansion (ULE) base. These components will play a critical role in any light particle search (ALPS) and will also be included in ground testing equipment for the upcoming laser interferometer space antenna (LISA) mission. Contrary to the standard ultrastable designs where mirrors are bonded to the spacers, ruling out any later modifications and alignments, our design remains flexible and allows the alignment of optical components at all stages to be optimized and changed. Here we present the dimensional stability and angular stability of two commercial mirror mounts characterized in a cavity setup. The long-term length change in the cavity did not exceed 30 nm and the relative angular stability was within 2 µrad, which meet the requirements for ALPS. We were also able to demonstrate 1 p m / H z length noise stability, which is a critical requirement for various subsystems in LISA. These results have led us to design similar opto-mechanical structures, which will be used in ground verification to test the LISA telescope.

We propose a new strategy to directly detect light particle dark matter that has long-ranged interactions with ordinary matter. The approach involves distorting the local flow of dark matter with time-varying fields and measuring these distortions with shielded resonant detectors. We apply this idea to sub-MeV dark matter particles with very small electric charges or coupled to a light vector mediator, including the freeze-in parameter space targeted by low mass direct detection efforts. This approach can probe dark matter masses ranging from 10 MeV to below a meV, extending beyond the capabilities of existing and proposed direct detection experiments.

Recently, the KOTO experiment reported their new preliminary result of searching for the decay $K_L\to\pi^0\nu\bar{\nu}$. Three candidate events were observed in the signal region, which exceed significantly the expectation based on the standard model. On the other hand, the new NA62 and previous BNL-E949 experiments yielded a consistent result and confirmed the standard model prediction in the charged meson decay $K^+\to\pi^+\nu\bar{\nu}$. Furthermore, the two decays are bound by a well-motivated relation from an analysis of isospin symmetry that is hard to break by the new physics of heavy particles. In this work, we study the issue by a systematic effective field theory approach with three of the simplest scenarios, in which the $K_L$ may decay into a new light neutral particle $X$, i.e., $K_L\to\pi^0X$, $K_L\to \gamma\gamma X$, or $K_L\to\pi^0XX$. We assess the feasibility of the scenarios by simulations and by incorporating constraints coming from NA62 and other relevant experiments. Our main conclusion is that the scenario $K\to\pi XX$ for a long lived scalar $X$ seems more credible than the other two when combining distributions and other experimental constraints while the region below the KOTO's blind box provides a good detection environment to search for all three scenarios for a relatively heavy $X$., Comment: 10 pages, with 10 figures and 4 appendices; v2: added 4 refs [9,10,17,35], no changes in wording; v3: proofred version to appear in PRD, many improvements/explanations in response to referees' comments and suggestions, added a new figure 3, conclusions not altered, 11 pages, with 11 figures and 4 appendices

International audience; The behavior of solute atoms in an undersaturated Fe-3.3at.%Ni model alloy upon heavy and light particle irradiations was investigated by Atom Probe Tomography. Whereas the first irradiations, performed using 27 MeV Fe ions at 400°C, highlight significant Ni enrichment on PD clusters, solute-rich features detected after 2.8 MeV protons H+ ions (400°C) and 1 MeV electron (320°C) irradiations are only associated with pre-existent microstructural defects. Nanoindentation tests shows no hardening in light particle irradiated samples, strongly suggesting that no dislocation loop formed. These observations put forward the importance of point defect clusters resulting from displacement cascades in Ni clusters’ formation.

We study the three-body systems of K¯(*)B(*)B¯(*) by solving the Faddeev equations in the fixed-center approximation, where the light particle K¯(*) interacts with the heavy bound states of BB¯ (B*B¯*) forming the clusters. In terms of the very attractive K¯*B and K¯*B* subsystems, which are constrained by the observed Bs1(5830) and Bs2*(5840) states in experiment, we find two deep bound states, containing the hidden-bottom components, with masses 11002±63 MeV and 11078±57 MeV in the K¯*BB¯ and K¯*B*B¯* systems, respectively. The two corresponding states with higher masses of the above systems are also predicted. In addition, using the constrained two-body amplitudes of K¯B(*) and K¯B¯(*) via the hidden gauge symmetry in the heavy-quark sector, we also find two three-body K¯BB¯ and K¯B*B¯* bound states.

Conventional imaging methods could not distinguish processes within the ventral and dorsal streams. The application of Fourier time series analysis was helpful to segregate changes in the ventral and dorsal streams of the visual system in male and female mice. The present study measured the accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in the mouse brain using small animal positron emission tomography and magnetic resonance imaging (PET/MRI) during light stimulation with blue and yellow filters, compared to during conditions of darkness. Fourier analysis was performed using mean standardized uptake values (SUV) of [18F]FDG for each stimulus condition to derive spectral density estimates for each condition. In male mice, luminance opponency occurred by S-peak changes in the sub-cortical retino-geniculate pathways in the dorsal stream supplied by ganglionic arteries in the left visual cortex, while chromatic opponency involved C-peak changes in the cortico-subcortical pathways in the ventral stream perfused by cortical arteries in the left visual cortex. In female mice, there was resonance phenomenon at C-peak in the ventral stream perfused by the cortical arteries in the right visual cortex during luminance processing. Conversely, chromatic opponency caused by S-peak changes in the subcortical retino-geniculate pathways in the dorsal stream supplied by the ganglionic arteries in the right visual cortex. In conclusion, Fourier time series analysis uncovered distinct mechanisms of color processing in the ventral stream in males, while in female mice color processing was in the dorsal stream. It demonstrated that computation of colour processing as a conscious experience could have a wide range of applications in neuroscience, artificial intelligence and quantum mechanics.

We present detailed results of a theoretical investigation on the production of evaporation residue nuclei obtained in a heavy ion reaction when charged particles (proton and $\alpha$-particle) are also emitted with the neutron evaporation along the deexcitation cascade of the formed compound nucleus. The almost mass symmetric $^{82}$Se+$^{138}$Ba reaction has been studied since there are many experimental results on individual evaporation residue (ER) cross sections after few light particle emissions along the cascade of the $^{220}$Th compound nucleus (CN) covering the wide 12--70 MeV excitation energy range. Our specific theoretical results on the ER cross sections for the $^{82}$Se+$^{138}$Ba are in good agreement with the available experimental measurements, but our overall theoretical results concerning all possible relevant contributions of evaporation residues are several times greater than the ERs measured in experiment. The discrepancy could be due to the experimental difficulties in the identification of ER nuclei after the emission of multiple neutral and charged particles, nevertheless the analysis of ER data is very important to test the reliability of the model and to stress the importance on the investigation of ER nuclei also obtained after charged particle emissions., Comment: 16 pages, 4 figures, Accepted for publication in Nucl. Phys. A

Synopsis Fully differential cross sections for the single ionization of the 1b 1 and 3a 1 orbitals of H2O by electron- and positron-impact are calculated by means of the CDW-EIS model at an impact energy of 81 eV. A proper average procedure over molecular orientations is performed. Main differences between positron- and electron-impact are observed for coplanar geometries in the binary structures. In addition, an enhancement of the binary region and a decrease of the recoil lobe are observed for positron-impact.