Particles In Field Research Articles

QCD running in lepton number violating meson and tau decays

Below the electroweak scale, new physics that violates the lepton number in two units (ΔL=2) and is mediated by heavy particle exchange can be parametrized by a dimension-nine low-energy effective Lagrangian. Operators in this Lagrangian involving first-generation quarks and leptons contribute to the short-range mechanism of neutrinoless double beta decay (0νββ) and therefore they are strongly constrained. On the other hand, operators with other quark and lepton families are bounded by the nonobservation of different lepton number violating meson and tau decays, such as M1−→M2+ℓ1−ℓ2− and τ−→ℓ+M1−M2−. In this work, we calculate renormalization-group-evolution (RGE)-improved bounds on the Wilson coefficients involved in these decays. We calculate QCD corrections to the dimension-nine operator basis and find RGE matrices that describe the evolution of the Wilson coefficients across different energy scales. Unlike the running of operators involved in 0νββ decay, the general flavor structure leads to the mixing of not only different Lorentz structures but also of different quark-flavor configurations. Additionally, operators that vanish for the identical lepton case need to be added to the operator basis. We find new constraints on previously unbounded operators and the enhancement of bounds for specific Wilson coefficients. We also find new bounds coming from the mixing between operators with different quark-flavor configurations. Published by the American Physical Society 2025

The effect of filler particle size on API homogeneity of controlled release formulations via continuous twin-screw wet granulation.

Previous research has shown that controlled release (CR) formulations with hydrox- ypropyl methylcellulose (HPMC) as hydrophilic matrix former produced via twin-screw wet granulation (TSWG) yield granules with an inhomogeneous active pharmaceutical ingredient (API) distribution (Denduyver et al., 2024). This was attributed to the fast hydration and swelling behaviour of HPMC upon addition of granulation liquid, limiting granule breakage and continuous exchange of particles during granule growth. Altering the liquid-to-solid ratio (L/S-ratio), using a more aggressive screw configuration or using fillers with different sol- ubility did not yield granules with a homogeneous API distribution. Therefore, the effect of the filler particle size on the content uniformity and granule growth mechanism of CR granules was studied using filler grades with a smaller and larger particle size distribution (PSD) than the API. As granule growth in TSWG occurs spatially along the granulator unit, a compartmental analysis was performed to collect granules from each zone. The small particle size fillers yielded a more homogeneous API distribution compared to the large particle size fillers in each compartment throughout the granulator unit. However, for lactose-, mannitol- and dicalcium phosphate (DCP)-based formulations, underdosing in the fines fraction (<150 µm) was observed. The small particle size microcrystalline cellulose (MCC)-based formulation yielded a homogeneous API distribution. The inter- play of the swelling behavior of MCC and the smaller particle size facilitated wetting, favoring the homogeneous API distribution over the granule sieve fractions.

Meridional Central Pacific Ocean Depth Section for Pb and Pb Isotopes (GEOTRACES GP15, 152°W, 56°N to 20°S) Including Shipboard Aerosols

AbstractMost oceanic lead (Pb) is from anthropogenic emissions into the atmosphere deposited into surface waters, mostly during the past two centuries. The space‐ and time‐dependent emission patterns of anthropogenic Pb (and its isotope ratios) constitute a global geochemical experiment providing information on advective, mixing, chemical, and particle flux processes redistributing Pb within the ocean. Pb shares aspects of its behavior with other elements, for example, atmospheric input, dust solubilization, biological uptake, and reversible exchange between dissolved and adsorbed Pb on sinking particles. The evolving distributions allow us to see signals hidden in steady‐state tracer distributions. The global anthropogenic Pb emission experiment serves as a tool to understand oceanic trace element dynamics. We obtained a high‐resolution (5° station spacing) depth transect of dissolved Pb concentrations and Pb isotopes from Alaska (55°N) to just north of Tahiti (20°S) near 152°W longitude. The sections reveal distinct sources of Pb (American, Australian, and Chinese), transport of Australian style Pb to the water mass formation region of Sub‐Antarctic Mode Water which is advected northward, columnar Pb isotope contours due to reversible particle exchange on sinking particles from high‐productivity particle veils, and a gradient of high northern deep water [Pb] to low southern deep water [Pb] that is created by reversible exchange release of Pb from sinking particles carrying predominantly northern hemisphere Pb. 208Pb/206Pb versus 206Pb/207Pb isotope relationships show that most oceanic Pb in the North Pacific is from Chinese and American sources, whereas Pb in the South Pacific is from Australian and American sources.

The effect of relative position on the motion and interactions of particle sedimentation under gravity in a finite-width vertical channel

Understanding the settling behaviour of particles and the interactions between fluid and particles in channelled fluids is crucial for various natural and industrial processes. The research presented in this study focuses on elucidating the sedimentation modes of dual particles within finite-width channels, employing the Arbitrary Lagrangian-Eulerian (ALE) method in conjunction with Hertz contact theory. We aim to understand how the initial relative position affects the dynamic characteristics of particle settlement. The threshold values of α = 35° and gap ratio (the distance between particles relative to their diameter) L/D = 3.5 are deemed critical. The phenomenon of particles ‘kissing’ does not manifest when the initial angle α ≤ 35°. As the α increases, the DKT (Drafting-Kissing-Tumbling) process recurs at earlier stage. In all cases where dual-particle are arranged in a vertically aligned pattern (D P1 = D P2 or DP1> DP2 ), the settling behaviour of particles will eventually achieve a steady state characterized by the DKT process when L/D ≤ 4.0. As the gap ratio (L/D) increases, the time taken for the kissing phenomenon is prolonged. Additionally, the two particles exchange positions and the larger particle taking the lead in the settling process. In scenarios where dual particles are arranged side by side, the kissing phenomenon does not occur. Instead, the trajectory of the particles deviates from the centreline and shifts towards the channel wall due to the Magnus effect when L/D ≤ 2.0. When L/D ≥ 3.0, particles settle as though they were a single particle. In cases involving multiple particles, the hindering effect of the wall becomes significant and can not be ignored, leading to the observation of Rayleigh-Taylor instability development. As a result, the overall settlement pattern tends to be ‘concave’.

Non-Hermitian Topology in Hermitian Topological Matter.

Non-Hermiticity gives rise to distinctive topological phenomena absent in Hermitian systems. However, connection between such intrinsic non-Hermitian topology and Hermitian topology has remained largely elusive. Here, considering the bulk and boundary as an environment and system, respectively, we demonstrate that anomalous boundary states in Hermitian topological insulators exhibit non-Hermitian topology. We study the self-energy capturing the particle exchange between the bulk and boundary, and show that it detects Hermitian topology in the bulk and induces non-Hermitian topology at the boundary. As an illustrative example, we reveal non-Hermitian topology and concomitant skin effect inherently embedded within chiral edge states of Chern insulators. We also identify the emergence of hinge states within effective non-Hermitian Hamiltonians at surfaces of three-dimensional topological insulators. Furthermore, we comprehensively classify our correspondence across all the tenfold symmetry classes of topological insulators and superconductors. Our Letter uncovers hidden connection between Hermitian and non-Hermitian topology, and provides an approach to identifying non-Hermitian topology in quantum matter.

Spectral density of the Wigner path integral operator correlation function representation. Monte Carlo simulation of the fermion dynamic structure factor

An important mathematical function that describes the interparticle correlations and their time evolution is the dynamic structure factor (DSF). According to Van Hove the dynamic structure factor (DSF) is the space and time Fourier transform of the density-density correlation function of the unperturbed system. In the case of classical systems, computations of the DSF typically employ classical molecular dynamics techniques. However, the present study focuses on quantum systems, in particular on the quantum dynamic structure factor. The main idea of this article is to employ the Wigner formulation of quantum mechanics to derive a new path integral description of the quantum DSF. The next important idea is to consider paths in this representation as stationary random processes and apply the Wiener–Khinchin theorem to express the DSF through the expected values of the power spectrum of trajectories in this representation. To calculate the DSF, spin-resolved radial distribution functions (RDFs) and other thermodynamic parameters of a 3D system of soft sphere fermions we developed a Wigner Path Integral Monte Carlo (WPIMC) method. The observed peaks on the RDFs and DSFs were attributed to wave interference resulting from a multiple-scattering and perturbation effects due to particle exchange and interaction. This phenomenon, observed in a soft sphere scattering system, may serve as a precursor to Anderson localisation, a mechanism in which wave interference across multiple scattering channels prevents wave propagation.

Exploring Gluconamide-Modified Silica Nanoparticles of Different Sizes as Effective Carriers for Antimicrobial Photodynamic Therapy.

Antimicrobial resistance (AMR), a consequence of the ability of microorganisms, especially bacteria, to develop resistance against conventional antibiotics, hampering the treatment of common infections, is recognized as one of the most imperative health threats of this century. Antibacterial photodynamic therapy (aPDT) has emerged as a promising alternative strategy, utilizing photosensitizers activated by light to generate reactive oxygen species (ROS) that kill pathogens without inducing resistance. In this work, we synthesized silica nanoparticles (NPs) of different sizes (20 nm, 80 nm, and 250 nm) functionalized with the photosensitizer Rose Bengal (RB) and a gluconamide ligand, which targets Gram-negative bacteria, to assess their potential in aPDT. Comprehensive characterization, including dynamic light scattering (DLS) and photophysical analysis, confirmed the stability and effective singlet oxygen production of the functionalized nanoparticles. Although the surface loading density of Rose Bengal was constant at the nanoparticle external surface, RB loading (in mg/g nanoparticle) was size-dependent, decreasing with increasing nanoparticle diameter. Further, the spherical geometry of nanoparticles favored smaller nanoparticles for antibacterial PDT, as this maximizes the surface contact area with the bacteria wall, with the smallest (20 nm) and intermediate (80 nm) particles being more promising. Bacterial assays in E. coli revealed minimal dark toxicity and significant light-activated phototoxicity for the RB-loaded nanoparticles. The addition of gluconamide notably enhanced phototoxic activity, particularly in the smallest nanoparticles (RB-G-20@SiNP), which demonstrated the highest phototoxicity-to-cytotoxicity ratio. These findings indicate that small, gluconamide-functionalized silica nanoparticles are highly effective for targeted aPDT, offering a robust strategy to combat AMR.

A log story short: running contributions to radiative Higgs decays in the SMEFT

We investigate the renormalization of the radiative decays of the Higgs to two gauge bosons in the Standard Model Effective Field Theory at mass dimension eight. Given that these are loop-level processes, their one-loop renormalization can be phenomenologically important when triggered by operators generated through the tree-level exchange of heavy particles (assuming a weakly coupled UV model). By computing the tree-level matching conditions of all relevant extensions of the Standard Model, we demonstrate that this effect is indeed present in the h → γZ decay at dimension eight, even though it is absent at dimension six. In contrast, the h → gg and h → γγ decays can only be renormalized by operators generated by one-loop processes. For UV models with heavy vectors, this conclusion hinges on the specific form of their interaction with massless gauge bosons which is required for perturbative unitarity. We study the quantitative impact of the possible logarithmic enhancement of h → γZ, and we propose an observable to boost the sensitivity to this effect. Given the expected increased precision of next-generation high-energy experiments, this dimension-eight contribution could be large enough to be probed and could therefore give valuable clues about new physics by revealing some of its structural features manifesting first at dimension eight.

Welding process stability in narrow-gap oscillating laser-MIG hybrid welding of titanium alloys with various oscillating patterns

Revealing the mechanism of laser oscillating patterns on the laser-MIG hybrid welding process stability was of great significance for improving weld formation and controlling porosity defect of titanium alloys. Convex welds were formed with poor surface formation using linear, 8-shaped and infinity oscillating laser. A circular oscillating laser with more uniform energy distribution favored the formation of concave weld. Weld porosity decreased by approximately 60 % when compared to laser with linear oscillating pattern. A keyhole with the maximum opening size was formed and fluctuated slightly. More laser-induced plasma (LIP) was ejected from the keyhole, which favored the enhancement of electric channel. Particle exchange between the arc and LIP was enhanced. Additionally, the arc burnt stably. The wire melting was accelerated to form smaller droplets, and the droplet transfer frequency increased by about 9.2 % compared with that via linear oscillating laser. Furthermore, the droplet impact force decreased by about 27.3 %. The liquid ridge (LR), formed by the droplet impact, was cushioned by the circular flow of molten metal. The droplet disturbance impact on keyhole wall was suppressed. Besides, when laser oscillated with circle pattern, the liquid metal was sufficiently diffused to rear part of molten pool, thereby suppressing convex welds.

Defect-rich In2S3/CoS2 heterostructure for rapid storage of sodium ions

Aiming to accelerate sodium-ion transport kinetics and improve electrochemical cyclability of batteries, an In2S3/CoS2 bimetallic sulfide heterostructure was synthesized as anodes of sodium-ion batteries (SIBs) in this paper by a feasible ion exchange and subsequent hydrothermal vulcanization technique based on a cobalt metal-organic skeleton (ZIF-67) precursor. As-prepared In2S3/CoS2 composite exhibited an excellent rate capability of 453.8 mAh g-1 at 10 A g-1 and outstanding cyclability of 464.06 mAh g-1 after 600 cycles at 2 A g-1. The built-in electric filed between heterogeneous interface of In2S3 and CoS2 plays a dominant contribution on improvement of electronic conductivity and charge transfer kinetics. Beyond that abundant defects derived from ion exchange and nanocrystallization of composite particles also have a positive synergistic effect on inducing additional active centers for adsorption of Na+ and shortening ion transport distance for further accelerating reaction kinetics. Based on exploring conversion and alloying mechanism of In2S3/CoS2 composite via ex situ XRD and TEM, high-performance SIBs with heterostructure bimetallic sulfide anodes may be a prospective strategy.

Availability, storage capacity, and diffusion: Stationary states of an asymmetric exclusion process connected to two reservoirs.

We explore how the interplay of finite availability, carrying capacity of particles at different parts of a spatially extended system, and particle diffusion between them control the steady-state currents and density profiles in a one-dimensional current-carrying channel connecting the different parts of the system. To study this, we construct a minimal model consisting of two particle reservoirs of finite carrying capacities connected by a totally asymmetric simple exclusion process (TASEP). In addition to particle transport via TASEP between the reservoirs, the latter can also directly exchange particles via Langmuir kinetics-like processes, modeling particle diffusion between them that can maintain a steady current in the system. We calculate the steady-state density profiles and the associated particle currents in the TASEP lane. The resulting phases and the phase diagrams are quite different from an open TASEP, and are characterized by the model parameters defining particle exchanges between the TASEP and the reservoirs, direct particle exchanges between the reservoirs, and the filling fraction of the particles that determines the total resources available. These parameters can be tuned to make the density on the TASEP lane globally uniform or piecewise continuous, and can make the two reservoirs preferentially populated or depopulated.

An Update of the Hypothetical X17 Particle

Recently, when examining the differential internal pair creation coefficients of 8Be, 4He and 12C nuclei, we observed peak-like anomalies in the angular correlation of the e+e− pairs. This was interpreted as the creation and immediate decay of an intermediate bosonic particle with a mass of mXc2≈ 17 MeV, receiving the name X17 in subsequent publications. In this paper, our latest results obtained for the X17 particle are presented by investigating the e+e− pair correlations in the decay of the Giant Dipole Resonance (GDR) of 8Be. Our results initiated a significant number of new experiments all over the world to detect the X17 particle and determine its properties. In this paper, we will also conduct a mini-review of the experiments whose results are already published, as well as the ones closest to being published.

Ship Power System Network Reconfiguration Based on Swarm Exchange Particle Swarm Optimization Algorithm

As one of the important components of a ship, the ship’s integrated power system is an important safeguard for ships. In order to improve the service life of the ship’s power grid, the power system should be able to realize rapid reconstruction to ensure continuous power supply of important loads when the ship is attacked or fails suddenly. Therefore, it is of vital importance to study the reconfiguration technology of the ship’s integrated power system to ensure that it can quickly and stably cope with all kinds of emergencies in order to guarantee the safe and reliable navigation of the ship. This paper takes the ship’s ring power system as the research object and sets up the maximum recovery load and the minimum number of switching operations. The load is divided uniformly and the generator efficiency is balanced for the reconstruction of comprehensive function. It also sets up the system capacity, topology, and branch current limitations of the constraints to establish a mathematical model. The load branch correlation matrix method is used for branch capacity calculation and generator efficiency equalization calculation, and the load backup power supply path matrix is added on the basis of the matrix to judge the connectivity of some loads before reconfiguration. In this paper, for the network reconfiguration of the ship circular power system, which is a discrete nonlinear problem with multiple objectives, multiple time periods, and multiple constraints, we choose to use the particle swarm algorithm, which is suitable for global optimization, with a simple structure and fewer parameters; improve the particle swarm algorithm using the swarm exchange strategy by setting up two main and auxiliary swarms for global and local search; and exchange some of the particles with the golden ratio in order to keep the diversity of the populations. The simulation results of the network reconfiguration of the ship power system show that the improved algorithm can solve the power system network reconfiguration problem more effectively and provide a feasible reconfiguration scheme in a shorter time compared with the chaotic genetic algorithm under the same fault case test, and it also proves that the use of the swarm exchange particle swarm algorithm greatly improves the performance of reconfiguring the power grid of the ship.

Low-virtuality splitting in the Standard Model

When the available collision energy is much above the mass of the particles involved, scattering amplitudes feature kinematic configurations that are enhanced by the much lower virtuality of some intermediate particle. Such configurations generally factorise in terms of a hard scattering amplitude with exactly on-shell intermediate particle, times universal factors. In the case of real radiation emission, such factors are splitting amplitudes that describe the creation or the annihilation — for initial or final state splittings — of the low-virtuality particle and the creation of the real radiation particles. We compute at tree-level the amplitudes describing all the splittings that take place in the Standard Model when the collision energy is much above the electroweak scale. Unlike previous results, our splitting amplitudes fully describe the low-virtuality kinematic regime, which includes the region of collinear splitting, of soft emission, and combinations thereof. The splitting amplitudes are compactly represented as little-group tensors in an improved bi-spinor formalism for massive spin-1 particles that automatically incorporates the Goldstone Boson Equivalence Theorem. Simple explicit expressions are obtained using a suitably defined infinite-momentum helicity basis representation of the spinor variables. Our results, combined with the known virtual contributions, could enable systematic predictions of the leading electroweak radiation effects in high-energy scattering processes, with particularly promising phenomenological applications to the physics of future colliders with very high energy such as a muon collider.

Symmetry Oscillations in Strongly Interacting One-Dimensional Mixtures.

Multicomponent quantum mixtures in one dimension can be characterized by their symmetry under particle exchange. For a strongly interacting Bose-Bose mixture, we show that the time evolution of the momentum distribution from an initially symmetry-mixed state is quasiconstant for a SU(2) symmetry conserving Hamiltonian, while it displays large oscillations in time for the symmetry-breaking case where inter- and intraspecies interactions are different. Using the property that the momentum distribution operator at strong interactions commutes with the class-sum operator, the latter acting as a symmetry witness, we show that the momentum distribution oscillations correspond to symmetry oscillations, with a mechanism analogous to neutrino flavor oscillations.

Constraints on simplified dark matter models involving an s-channel mediator with the ATLAS detector in pp collisions at s=13 TeV

This paper reports a summary of searches for a fermionic dark matter candidate in the context of theoretical models characterised by a mediator particle exchange in the s-channel. The data sample considered consists of pp collisions delivered by the Large Hadron Collider during its Run 2 at a centre-of-mass energy of s=13TeV and recorded by the ATLAS detector, corresponding to up to 140 fb-1. The interpretations of the results are based on simplified models where the new mediator particles can be spin-0, with scalar or pseudo-scalar couplings to fermions, or spin-1, with vector or axial-vector couplings to fermions. Exclusion limits are obtained from various searches characterised by final states with resonant production of Standard Model particles, or production of Standard Model particles in association with large missing transverse momentum.

Understanding Relaxation in the Kob-Andersen Liquid Based on Entropy, String, Shoving, Localization, and Parabolic Models.

We assess the validity of a range of models of glass formation based on molecular dynamics simulation results of the Kob-Andersen (KA) model system under a wide range of constant volume and constant pressure conditions. These models include the Adam-Gibbs model emphasizing configurational entropy, the string model emphasizing collective particle exchange motion, the shoving model emphasizing material elasticity, the localization model emphasizing dynamical free volume, and parabolic models based on the ideas of dynamic facilitation and, alternatively, the hypothesis that glass formation involves an avoided critical point. We demonstrate that these seemingly disparate models all provide a reasonable description of structural relaxation and diffusion data for the KA model system under all simulation conditions considered. Hence, the present study points to some unity in our understanding of the relationship between leading models of glass formation, supporting inferences drawn from previous studies of polymeric glass-forming liquids.

Intermediate mass-range particles from small scales: Nonperturbative techniques for cosmological collider physics from large-scale structure surveys

Intermediate mass-range particles from small scales: Nonperturbative techniques for cosmological collider physics from large-scale structure surveys

Loop corrections versus marginal deformations in celestial holography

Four-dimensional all-loop amplitudes in quantum electrodynamics and gravity exhibit universal IR singularities with a factorization structure. This structure is governed by tree amplitudes and a universal IR-divergent factor representing the exchange of soft particles between external lines. This Letter offers a precise dual interpretation of these universal IR-divergent factors within celestial holography. Considering the tree amplitude as the foundation of the celestial conformal field theory (CCFT), these universal factors correspond to marginal deformations with a construction in the CCFT. Remarkably, a novel geometric representation of these deformations through topological gauging provides an exact description of transitions within bulk vacuum moduli spaces which extends the celestial holography beyond the perturbative level. Our findings establish a concrete dictionary for celestial holography and offer a holographic lens to understand loop corrections in scattering amplitudes. Published by the American Physical Society 2024

Impact of the Out‐Of‐Plane Flow Shear on Magnetic Reconnection at the Flanks of Earth's Magnetopause

AbstractMagnetic reconnection changes the magnetic field topology and facilitates the energy and particle exchange at magnetospheric boundaries such as the Earth's magnetopause. The flow shear perpendicular to the reconnecting plane prevails at the flank magnetopause under southward interplanetary magnetic field conditions. However, the effect of the out‐of‐plane flow shear on asymmetric reconnection is an open question. In this study, we utilize kinetic simulations to investigate the impact of the out‐of‐plane flow shear on asymmetric reconnection. By systematically varying the flow shear strength, we analyze the flow shear effects on the reconnection rate, the diffusion region structure, and the energy conversion rate. We find that the reconnection rate increases with the upstream out‐of‐plane flow shear, and for the same upstream conditions, it is higher at the dusk side than at the dawn side. The diffusion region is squeezed in the outflow direction due to magnetic pressure which is proportional to the square of the Alfvén Mach number of the shear flow. The out‐of‐plane flow shear increases the energy conversion rate , and for the same upstream conditions, the magnitude of is larger at the dusk side than at the dawn side. This study reveals that out‐of‐plane flow shear not only enhances the reconnection rate but also significantly boosts energy conversion, with more pronounced effects on the dusk‐side flank than on the dawn‐side flank. These insights pave the way for better understanding the solar wind‐magnetosphere interactions.