Neutral Particles Research Articles

Weyl and Majorana for neutral particles

AbstractWe compare various formalisms for neutral particles. It is found that they contain unexplained contradictions. Next, we investigate the spin‐1/2 and spin‐1 cases in different bases. Next, we look for relations with the Majorana‐like field operator. We show explicit incompatibility of the Majorana ansatzen with the Dirac‐like field operators in both the original Majorana theory and its generalizations.

Electromagnetic-Wave Mechanism of Formation and Propagation of Astrophysical Vortex Jets Generated in the Jumper of a Spiral Galaxy

An explanation of the mechanism of generation and acceleration of jets in outer space is given on the basis of experiments in the physics of electrical discharge. The presence of two arms in the spiral Galaxy gives grounds to assume that they have excess charges of the opposite sign. At the moment when the electric field strength between the tips of the arms becomes sufficient, an electrical breakdown occurs, which is accompanied by the movement of the current-plasma leader in the jumper between the tips of the arms. In the head part of the leader there is a flat electric domain of a strong field, which, during its inception, emits intense transverse electromagnetic waves in a direction perpendicular to the direction of the leader’s motion and to the plane of the accretion disk. The electric domain periodically appears and collapses due to the entry of neutral particles. Transverse electromagnetic waves capture charged particles from the discharge region and accelerate them in the direction of wave propagation. The crossed fields of an electromagnetic wave perform the functions of a multistage accelerator. The acceleration of the particles of the plasma produced in the discharge to relativistic energy values in the region of narrow vortex jets occurs under the action of forces caused by the components of the electromagnetic wave fields and the pressure gradient. The charged particles of a vortex jet acquire a significant rotational moment under the action of the Lorentz force. Explanations of the generation of microwave, bremsstrahlung and optical radiation from the region of the jumper between the arms of the Galaxy in the absence of electrical breakdown are also given.

Data Compression Algorithm of the Ion and Neutral Particle Analyzer for the First Chinese Mars Mission

火星离子与中性粒子分析仪共设计10种在轨探测模式，不同探测模式下数据率不同，多种探测模式下数据量远超出最大下行数据率的限制。为降低数据率，利用仪器内部FPGA有限的资源对压缩处理方法进行了详细设计。通过分析仪器数据特点，火星离子与中性粒子分析仪压缩算法采用合并处理、对数压缩和无损压缩三种压缩算法组合。对于每种探测模式，FPGA程序可根据压缩标志选择相应压缩算法，实现三种压缩算法串行使用，或选择其中一种或两种算法。并且压缩标志可通过注入指令改写，实现在轨时根据需求灵活配置。合并处理压缩比为2或4，对数压缩的压缩比为2，无损压缩效率与样本数据间的相关性有关。在此基础上，利用等离子体定标测试系统完成了地面测试。测试结果表明，各探测模式下科学数据经过压缩后数据率满足任务指标要求。

Effect of Cholesterol Content of Lipid Composition in mRNA-LNPs on the Protein Expression in the Injected Site and Liver After Local Administration in Mice

Delivery of messenger RNA (mRNA) using lipid nanoparticles (LNPs) is expected to be applied to various diseases following the successful clinical use of the mRNA COVID-19 vaccines. This study aimed to evaluate the effect of the cholesterol molar percentage of mRNA-LNPs on protein expression in hepatocellular carcinoma-derived cells and in the liver after intramuscular or subcutaneous administration of mRNA-LNPs in mice. For mRNA-LNPs with cholesterol molar percentages reduced to 10 mol% and 20 mol%, we formulated neutral charge particles with a diameter of approximately 100 nm and polydispersity index (PDI) <0.25. After the intramuscular or subcutaneous administration of mRNA-LNPs with different cholesterol molar percentages in mice, protein expression in the liver decreased as the cholesterol molar percentage in mRNA-LNPs decreased from 40 mol% to 20 mol% and 10 mol%, suggesting that reducing the cholesterol molar percentage in mRNA-LNPs decreases protein expression in the liver. Furthermore, in HepG2 cells, protein expression decreased as cholesterol in mRNA-LNPs was reduced by 40 mol%, 20 mol%, and 10 mol%. These results suggest that the downregulated expression of mRNA-LNPs with low cholesterol content in the liver involves degradation in systemic circulating blood and decreased protein expression after hepatocyte distribution.

Effect of dusty plasma parameters on the low frequency Hall current instability

The effect of power-law dust size distribution and dust number density on the low frequency hall current instabilities have been studied in and above the equatorial electrojet altitudes using a linear fluid model consisting of electrons, ions and dust particles. The dispersion relation includes electron and ion drift perpendicular to the equilibrium uniform electric and magnetic field, mass and pressure of the charged species and collision between charged and neutral particles. The effect of dust size variation and dust number density on the instability have been investigated by varying the dust-plasma frequency in the dispersion relation. It has been found that in the region of the electrojet altitudes the variation of dust size for the case of broad dust size distribution and dust number density can substantially increase the growth rate and frequency of the instability. However, above the electrojet region where ions become weakly magnetized, the above two dust parameters have a negligible effect on the instability.The present analysis is applicable to the dusty meteor trail plasma of the ionospheric E-region.

Particles Dynamics in Schwarzschild like Black Hole with Time Contracting Horizon

The black holes radiate their mass and energy in the form of gravitational waves and Hawking-radiation, which lead to a decrease in the mass and energy of the black holes. During the formation of gravitational waves and Hawking radiation, the mass and energy of black holes reduce continuously with the passage of time t. For this reason the metric tensor of the black hole should depends on time t. In this work, a time-dependent term is introduced in the horizon of black hole without losing its symmetry structure by using the approximate Noether symmetry equation. The time-dependent term affects the effective potential, effective force, and all the dynamic features of the black hole. They are discussed for neutral and charged particles. Profiles of the escape velocity of colliding particles are also taken into consideration. Lyapunov exponent is used to check the stability of the orbits of the black hole. Hawking temperature, Bekenstein entropy, Komar energy, and specific energy at horizon of the black hole are discussed in this scenario.

Neutron-neutral particle mixing and its observable consequences

In this work, we explore the mixing between neutron ($n$) and elementary neutral particle ($\eta$), which violates both the baryon number ($\mathcal{B}$) and the lepton number ($\mathcal{L}$) by one unit but conserves their difference $(\mathcal{B}-\mathcal{L})$. Such mixing may give rise to non-trivial effects that are different from the Standard Model predictions. We organize our discussions based on two scenarios, roughly depending on whether an interference between oscillation and decay occurs, or whether the new-physics effects associated with the $n$-$\eta$ mixing contribute to the absorptive mixing amplitude. If an oscillation process is not accompanied by an interference between oscillation and decay, or the new-physics interactions do not contribute to the absorptive mixing amplitude, such a process can be classified as pure oscillation. Otherwise, it can be classified as impure oscillation. In the scenario of pure oscillation, CP-violation arising from the Majorana phase can manifest itself through the $n$-$\bar{n}$ oscillation process and may lead to observable effects. In the scenario of impure oscillation, we analyze the testable implications on the masses and lifetimes of the mass eigenstates formed as a result of the $n$-$\bar{n}$ oscillation mediated by $\eta$. In this scenario, we also suggest a unified interpretation of the neutron lifetime anomaly and the $n$-$\bar{n}$ oscillation measurements based on the $n$-$\eta$ mixing. In both scenarios, we present the lower bounds imposed by the experimental searches for $n$-$\bar{n}$ oscillations on the masses of the color multiplet bosons and point out that they could be within the reach of a direct detection at the LHC or future high-energy experiments.

Radiation forces and compression of neutral particles by an optical lens

The ultra-short optical pulses can be used for the confinement of neutral particles by an additional optical longitudinal force, connected with the Poynting vector and the influence of the magnetic field on their polarizability. The Poynting vector is connected also to the intensity of the electromagnetic field. On other hand, the intensity of a laser pulse can be manipulated by an optical lens, and thus, indirectly, the optical force can be increased or decreased or its direction to be changed. This in turn enables a unique possibility for the compression of neutral atoms, molecules, and particles into the focus of the lens. Here, we reported on an experimental study of neutral particle confinement in the focus of femtosecond laser pulses and further confirmed by a theoretical investigation. The findings demonstrate an innovative approach to the compression and confinement of neutral particles within the focal plane of a lens and their further manipulation. Feasible applications could be in the field of cold nuclear fusion and cooling of light-neutral atoms and molecules.

Insights into the effect of hollow cathode with external injection of fast ions in a sputter-type negative ion source

In sputter-type negative ion sources, the negative ion currents and ionization efficiencies are very dependent upon the creation of a sputter crater and formation of an intense plasma glow. This effect has many similarities with the well-known phenomena of hollow cathode discharges (HCDs). This paper discusses the phenomenological model related to conventional HCDs, including modes with injection of external energetic particles. We propose that HCDs play a major role in sputter-type negative ion sources. In this study, we evaluate the phenomenology of a discharge with a hollow cathode and derive an analytical formula that defines the neutral particle density inside the cathode cavity and substantiates how the classic HCD occurs in sputter-type negative ion sources. The cathode pit geometry was revealed by optical microscopy. Volt–ampere characteristics were investigated in order to compare it to typical discharges with hollow cathodes. In sputter-type negative ion sources, known as SNICS, discharge characteristics and observed light glow inside the cathode pit after its formation were very similar to data published on HCDs. The HCD phenomenon explains how the cathode current increases by orders of magnitude after creation of the cathode pit. The HCD effect in SNICS and similar sputter sources compliments existing mechanisms of negative ion production, especially ion pair production close to the cathode surface due to low energy ionization based on the collision–radiation model. The wealth of information accumulated over the last century on HCDs can be used to describe and explain the phenomenology of physics and operation of sputter negative ion sources.

Parametric Model-Order Reduction for Radiation Transport Simulations Based on an Affine Decomposition of the Operators

This work presents a data-driven, projection-based parametric reduced-order model (ROM) for the neutral particle radiation transport (linear Boltzmann transport) equation. The ROM utilizes the method of snapshots with proper orthogonal decomposition. The novelty of the work is in the detailed proposal to exploit the parametrically affine transport operators to intrusively, yet efficiently, build the reduced transport operators in real time in a matrix-free manner compatible with sweep-based transport solvers. This affine-based ROM is applied to one-dimensional (1-D), two-dimensional (2-D), and 2-D multigroup transport benchmarks and is found to significantly outperform less intrusive ROMs in terms of speed for a desired accuracy level. The ROM has an 18.2 to 89.4 speedup with an error range of 0.0002% to 0.01% for the 1-D benchmark, a 1120× to 4870× speedup with an error range of 0.0009% to 0.01% for the 2-D benchmark, and a 54 600× to 399 800× speedup with an error range of 0.00022% to 0.01% for the multigroup 2-D benchmark. Even higher speedups are expected for three-dimensional multigroup transport problems.

Signatures of Dipolar Dark Matter on indirect detection

In this work, we study the annihilation of fermionic dark matter, considering it as a neutral particle with non-vanishing magnetic (M) and electric (D) dipole moments. Effective cross section of the process is computed starting from a general form of the coupling in the framework of an extension of the Standard Model. By taking into account the annihilation of dark matter pairs into mono-energetic photons, we found that for masses of O(102) GeV, an electric dipole moment ∼10−16 e cm is required to satisfy the current relic density inferences. Additionally, in order to pin down models viable to describe the physics of dark matter at the early Universe, we also constrain our model according to recent measurements of the temperature anisotropies of the cosmic microwave background radiation, and report constraints to the electric and magnetic dipole moments for a range of masses within our model.

High resolution characterization of a sheathed axisymmetric variable supersaturation condensation particle sizer

Diffusive condensation particle counters (CPCs) injecting the aerosol near the symmetry axis within a larger flow of a vapor-containing sheath gas have previously exhibited a size resolving power considerably lower than theoretically expected. We hypothesize that reexamining these instruments with particles of improved uniformity in composition, size and shape should reveal a much better performance, well suited for high resolution particle sizing and basic heterogeneous nucleation studies. Accordingly, we investigate the performance of the Variable Supersaturation Condensation Particle Sizer (VSCPS) of Gallar et al. (2006) with an aerosol of uniform singly charged polyethylene glycol particles (3–9 nm diameter), produced by a bipolar electrospray, and size-selected by a differential mobility analyzer of high resolution. The condensation size resolution obtained with n-butanol vapor almost triples that previously demonstrated for this instrument, exceeds that established for any other CPC, and can apparently be further increased. Flow and temperature field calculations of the maximal supersaturation in the VSCPS would enable basic heterogeneous nucleation studies, as well as high resolution sizing of neutral or charged particles.

Ultrafast Dissociation Dynamics Induced in [Fe(CO)5] n Xe m Mixed Clusters by Resonant Femtosecond Infrared Laser Radiation.

Real-time dissociation dynamics induced in [Fe(CO)5] n Xe m mixed molecular clusters by femtosecond IR radiation in the 5 μm region was studied for the first time by means of time-resolved methods based on resonant excitation of C≡O vibrations in the molecular core of the cluster and photoionization probing (λ = 400 nm) of its decay products. It was found that IR-excited clusters in the initially cold particle beam are heated and dissociated as a result of relaxation processes, giving rise to free neutral Xe aggregates and Fe(CO)5 molecules. Thus, the formed particles are the origin of signal variations from Xe+ and Fe(CO)5 + ions, which grow on a picosecond time scale. It is concluded that the initial laser excitation of C≡O vibrations in clusterized molecules is followed by the process of cluster dissociation accompanied with the formation of free neutral particles according to the hierarchy of binding energies: weakly bound shells of Xe atoms are evaporated first and much faster than the Fe(CO)5 molecules from the cluster core. The characteristic times of relaxation processes as well as the cluster temperature were estimated.

On the vertical and horizontal profiles of the atmospheric electric field during thunderstorms

We present the first results of a new experiment on Mt. Aragats for measuring the horizontal profile of atmospheric electric fields during thunderstorms. Networks of advanced particle spectrometers operated on the slopes of Mt. Aragats continuously measure fluxes of charged and neutral particles, periodically registering impulsive enhancements, so-called Thunderstorm Ground Enhancements (TGEs). This gives the possibility to estimate the strength of the electric field in the lower atmosphere. Relativistic Runaway Electron Avalanches (RREAs) are registered by the particle detectors located on the Earth's surface as TGEs sometimes exceeding the fair-weather fluxes up to a hundred times. The strong accelerating electric field can reach 1.7-2.2 kV/cm at altitudes 3-6 km, and extend down to 50-150 m above the Earth's surface. The horizontal extent of the electric field can reach 10 km and more.

Io’s Volcanic Activity and Atmosphere

Driven by tidal heating, Io’s extreme volcanism has created a young, impact crater–free surface dominated by hundreds of active volcanic centres. From these volcanoes erupt voluminous, low-viscosity, high-temperature silicate lavas. Volcanic plumes, from venting gas and mobilised surface ices (primarily SO2 and S), contribute to Io’s thin atmosphere. Away from volcanoes, SO2 ice on the surface alternately sublimes during the daytime and condenses during eclipses and at night, resulting in a strong day/night atmospheric dichotomy. Sunlight and radiation bombardment at high altitude breaks the gas molecules apart, leading to the formation of SO, O, O2, S, K, Na, and Cl. These atoms reside as both neutral and charged particles in clouds that are found along Io’s orbit around Jupiter.

Ionization-induced optical heterogeneity and ion-like direct emission in 1-nm silicon nanoparticle grains: Prospect for fast optical modulation

Silicon, a highly symmetric and homogeneous material, does not exhibit fast optical modulation. Recent classical electrodynamics simulations, however, demonstrated transient optical heterogeneity in silicon nanostructures, in which a high-density of excitonic electron–hole pair plasma and charge is created. The phenomenon, however, requires a specific particle size (∼100 nm diameter) and a high-density (1023/cc) plasma. We examine here the quantum aspect of the heterogeneity in 1-nm Si nanoparticles. Due to the small number of atoms, 1 nm nanoparticles are amenable to the Hartree–Fock first principle atomistic quantum theory simulations procedure, while single ionization events are sufficient to provide high charge density (2 × 1021/cc). The simulations show that the charge distribution in singly charged 1-nm particles is nonlinear and heterogeneous, accompanied with structural distortion that produces an electric dipole moment. Electronically, the simulations show that the single charge induces stationary Coulomb states that riddle the bandgap of the neutral particle, with dipole-allowed transitions, effectively inducing partial conducting-like behavior. Optically, when the charge is produced by ionizing UV radiation, the ionized particle survives and exhibits both extended (wide-band) as well as atomic- or ion-like sharp emission, in agreement with infrared polarimetry and spectroscopy observations in the solar coronal holes, as well as under synchrotron irradiation. Not only do ionized Si nanoparticles (charged nanosilicon grains) afford fast optical modulations, but they may also prove pivotal for understanding features of interstellar medium, observed throughout the Milky Way and other galaxies, including spectroscopic and material composition, as well as neutral hydrogen abundancy.

Metrological aspects of determining the electron concentration and the conductivity of a melt using a conductivity sensor

For radiophysics, research into plasma physics is of great interest. During the movement of a hypersonic aircraft, the main physical phenomenon, which radically affects the conditions for the propagation of electromagnetic waves in its vicinity is the formation of a plasma shell around the apparatus due to the ionization of neutral particles. The resulting plasma around a hypersonic aircraft has a very high concentration of electrons and prevents the propagation of electromagnetic waves in space, partially absorbing them and reflecting them from its surface. When measuring the electron concentration, it is necessary to take into account the measurement error. In this article, the error is measured on the basis of expressions obtained for a transmission line whose longitudinal dimension exceeds the wavelength propagating in it. Mathematical model for finding the error in determining the electron concentration and melt conductivity is considered, and an analysis of the optimal combination of sensors is carried out.

Error of determination of radio-brightness temperature and temperature of plasma electrons

In our time, plasma physics is a hot topic of research. During the movement of a hypersonic aircraft, the main physical phenomenon, which radically affects the conditions for the propagation of electromagnetic waves in its vicinity is the formation of a plasma shell around the apparatus due to the ionization of neutral particles. When measuring the radio-brightness temperature and the temperature of plasma electrons, it is necessary to take into account the measurement error. In this article, these measurements are carried out, and the dependence of the root-mean-square relative error of temperature measurement on the power division factor is also given.

Large Ion-neutral Drift Velocities and Plasma Heating in Partially Ionized Coronal Rain Blobs

In this paper we present a numerical study of the dynamics of partially ionized coronal rain blobs. We use a two-fluid model to perform a high-resolution 2D simulation that takes into account the collisional interaction between the charged and neutral particles contained in the plasma. We follow the evolution of a cold plasma condensation as it falls through an isothermal vertically stratified atmosphere that represents the much hotter and lighter solar corona. We study the consequences of the different degrees of collisional coupling that are present in the system. On the one hand, we find that at the dense core of the blob there is a very strong coupling and the charged and neutral components of the plasma behave as a single fluid, with negligible drift velocities (of a few cm s−1). On the other hand, at the edges of the blob the coupling is much weaker and larger drift velocities (of the order of 1 km s−1) appear. In addition, frictional heating causes large increases of temperature at the transition layers between the blob and the corona. For the first time we show that such large drift velocities and temperature enhancements can develop as a consequence of ion-neutral decoupling associated to coronal rain dynamics. This can lead to enhanced emission coming from the plasma at the coronal rain-corona boundary, which possesses transition region temperature.

Nanoscale crystal growth processes triggered by captured solid impurity particles

Atomic force microscopy (AFM) was used to study the influence of solid neutral particles on dynamics and kinetics of surface growth on nanoscale. The experiment involved real-time observations of the hydroxymethylquinoxalinedioxide (C10H10N2O4) surface capturing micrometer tourmaline particles of no particular shape and with low adhesiveness to the material of the host crystal. It was made possible to visualize in detail a hillock formation on a screw dislocation triggered by a captured particle, as well as dislocation propagation through the overgrowing macrostep.Out of the multitude of similar size particles, only one of them generated a long-term screw dislocation – that was the particle in whose area a Frank-Read dislocation had been triggered even before the particle cavities were sealed. A detailed scanning showed that the wellknown phenomenon of a dislocation propagating through the overgrowing layers manifests itself as creation of a new screw hillock with monomolecular steps exactly above the lower hillock axis.The author’s method of statistical processing of AFM data was used to compile an array of average tangential and average normal growth rates and their fluctuations. In spite of the matter in the solution not being refilled, the normal and tangential rates showed constant and significant increase.The results were compared with the data from several earlier experiments with and without special impact during the growth process. It was established that the growth rate in the experiment with incorporation of impurities has small and almost stable fluctuations just like in the experiments without any impact.