Inelastic Collisions Research Articles

F0(980) production in inelastic pp collisions at [formula omitted] = 5.02 TeV

The measurement of the production of f0(980) in inelastic pp collisions at s=5.02 TeV is presented. This is the first reported measurement of inclusive f0(980) yield at LHC energies. The production is measured at midrapidity, |y|<0.5, in a wide transverse momentum range, 0<pT<16 GeV/c, by reconstructing the resonance in the f0(980)→π+π− hadronic decay channel using the ALICE detector. The pT-differential yields are compared to those of pions, protons and ϕ mesons as well as to predictions from the HERWIG 7.2 QCD-inspired Monte Carlo event generator and calculations from a coalescence model that uses the AMPT model as an input. The ratio of the pT-integrated yield of f0(980) relative to pions is compared to measurements in e+e− and pp collisions at lower energies and predictions from statistical hadronisation models and HERWIG 7.2. A mild collision energy dependence of the f0(980) to pion production is observed in pp collisions from SPS to LHC energies. All considered models underpredict the pT-integrated 2f0(980)/(π+ +π−) ratio. The prediction from the canonical statistical hadronisation model assuming a zero total strangeness content of f0(980) is consistent with the data within 1.9σ and is the closest to the data. The results provide an essential reference for future measurements of the particle yield and nuclear modification in p–Pb and Pb–Pb collisions, which have been proposed to be instrumental to probe the elusive nature and quark composition of the f0(980) scalar meson.

Nonlinear waves, modulations and rogue waves in the modular Korteweg–de​ Vries equation

Effects of nonlinear dynamics of solitary waves and wave modulations within the modular (also known as quadratically cubic) Korteweg–de Vries equation are studied analytically and numerically. Large wave events can occur in the course of interaction between solitons of different signs. Stable and unstable (finite-time-lived) breathers can be generated in inelastic collisions of solitons and from perturbations of two polarities. A nonlinear evolution equation on long modulations of quasi-sinusoidal waves is derived, which is the modular or quadratically cubic nonlinear Schrödinger equation. Its solutions in the form of envelope solitons describe breathers of the modular Korteweg–de Vries equation. The instability conditions are obtained from the linear stability analysis of periodic wave perturbations. Rogue-wave-type solutions emerging due to the modulational instability in the modular Korteweg–de Vries equation are simulated numerically. They exhibit similar wave amplification, but develop faster than in the Benjamin–Feir instability described by the cubic nonlinear Schrödinger equation.

Damped-driven system of bouncing droplets leading to deterministic diffusive behavior.

Damped-driven systems are ubiquitous in science, however, the damping and driving mechanisms are often quite convoluted. This paper presents an experimental and theoretical investigation of a fluidic droplet on a vertically vibrating fluid bath as a damped-driven system. We study a fluidic droplet in an annular cavity with the fluid bath forced above the Faraday wave threshold. We model the droplet as a kinematic point particle in air and as inelastic collisions during impact with the bath. In both experiments and the model, the droplet is observed to chaotically change velocity with a Gaussian distribution. Finally, the statistical distributions from experiments and theory are analyzed. Incredibly, this simple deterministic interaction of damping and driving of the droplet leads to more complex Brownian-like and Levy-like behavior.

Geometric Poisson distribution of photons produced in the ultrarelativistic hadronic collisions

We show that the multiplicity distribution of photons produced with enhanced void probability in inelastic proton-proton collisions at sqrt{s} = 900 GeV, 2.76 TeV, and 7 TeV, measured at forward rapidities by the ALICE experiment at LHC, can be described by the geometric Poisson distribution. The traditionally used negative binomial distribution fails to reproduce the enhanced void probability and the shape of the modified combinants simultaneously. Our findings are relevant for the theoretical modeling of photon production processes in high-energy hadronic collisions.

A multimodal neutron-based technique for the elemental analysis of materials in bulk

Neutrons and gamma rays are effective probes for the elemental characterisation of bulk samples. Neutrons interactions with matter are characteristic of the nature of the target nucleus, and the incident neutron energy. Most nuclides exhibit distinctive structure in their total and differential cross sections, thus elements can be differentiated via their total, elastic and inelastic scattering cross sections, and the energies of prompt gamma rays produced in inelastic collisions. In this work we report on the use of the fast neutron transmission analysis technique for the analysis of 12C in graphite. We also present results of prompt gamma ray neutron activation analysis of graphite using 14 MeV neutrons, which was explored for the purpose of developing a multimodal neutron-based technique for elemental analysis of materials in bulk.

High-energy Neutrino Constraints on Cosmic-Ray Reacceleration in Radio Halos of Massive Galaxy Clusters

A fraction of merging galaxy clusters host diffuse radio emission in their central region, termed a giant radio halo (GRH). The most promising mechanism of GRHs is the reacceleration of nonthermal electrons and positrons by merger-induced turbulence. However, the origin of these seed leptons has been under debate, and either protons or electrons can be primarily accelerated particles. In this work, we demonstrate that neutrinos can be used as a probe of physical processes in galaxy clusters and discuss possible constraints on the number of relativistic protons in the intracluster medium with the existing upper limits by IceCube. We calculate radio and neutrino emission from massive (>1014 M ⊙) galaxy clusters using the cluster population model of Nishiwaki & Asano. This model is compatible with the observed statistics of GRHs, and we find that the contribution of GRHs to the isotropic radio background observed with the ARCADE-2 experiment should be subdominant. Our fiducial model predicts the all-sky neutrino flux that is consistent with IceCube's upper limit from the stacking analysis. We also show that the neutrino upper limit gives meaningful constraints on the parameter space of the reacceleration model, such as the electron-to-proton ratio of the primary cosmic rays and the magnetic field; in particular, the secondary scenario, where the seed electrons mostly originate from inelastic pp collisions, can be constrained even in the presence of reacceleration.

Modulated super-Gaussian laser pulse to populate a dark rovibrational state of acetylene.

A pulse-shaping technique in the mid-infrared spectral range based on pulses with a super-Gaussian temporal profile is considered for laser control. We show a realistic and efficient path to the population of a dark rovibrational state in acetylene (C2H2). The laser-induced dynamics in C2H2 are simulated using fully experimental structural parameters. Indeed, the rotation-vibration energy structure, including anharmonicities, is defined by the global spectroscopic Hamiltonian for the ground electronic state of C2H2 built from the extensive high-resolution spectroscopy studies on the molecule, transition dipole moments from intensities, and the effects of the (inelastic) collisions that are parameterized from line broadenings using the relaxation matrix [A. Aerts, J. Vander Auwera, and N. Vaeck, J. Chem. Phys. 154, 144308 (2021)]. The approach, based on an effective Hamiltonian, outperforms today's abinitio computations both in terms of accuracy and computational cost for this class of molecules. With such accuracy, the Hamiltonian permits studying the inner mechanism of theoretical pulse shaping [A. Aerts et al., J. Chem. Phys. 156, 084302 (2022)] for laser quantum control. Here, the generated control pulse presents a number of interferences that take advantage of the control mechanism to populate the dark state. An experimental setup is proposed for in-laboratory investigation.

High-Energy Quantum Dynamics of the 15N + o-14N14N Rovibrational Activation and Isotope Exchange Processes.

We report full quantum reaction probabilities, computed within the framework of time-independent quantum mechanics using hyperspherical coordinates, for the 15N + 14N14N inelastic and reactive collision processes, restricted to total angular momentum J = 0, for kinetic energies up to 4.5 eV. We take advantage of the nonzero (i = 1) nuclear spin of 14N, leading to the existence of two nuclear spin isomers of 14N14N, namely, ortho- and para-14N14N, to restrict the study to the ortho molecular nitrogen species, with even rotational quantum number j = 0, 2, ... states. Specifically, we start with diatomic reagents ortho-14N14N in the initial rotational state j = 0. A comparison with similar works previously published by other groups using time-dependent wave packet and quasi-classical trajectory methods for the 14N + 14N14N fully symmetric collision is given. We find that reactive processes 15N + 14N14N involving atom exchange do not happen for collision energies less than 2.2 eV. Collisions at energies of around 2.0 eV are most effective for populating reactants' rovibrational states, that is, for inelastic scattering, whereas those at energies close to 5.0 eV yield a newly formed 14N15N isotopologue in a wide variety of excited vibrational levels.

Diffusion of muonic hydrogen in hydrogen gas and the measurement of the 1$s$ hyperfine splitting of muonic hydrogen

The CREMA collaboration is pursuing a measurement of the ground-state hyperfine splitting (HFS) in muonic hydrogen (\muμp) with 1 ppm accuracy by means of pulsed laser spectroscopy. In the proposed experiment, the \muμp atom is excited by a laser pulse from the singlet to the triplet hyperfine sub-levels, and is quenched back to the singlet state by an inelastic collision with a H_22 molecule. The resulting increase of kinetic energy after this cycle modifies the \muμp atom diffusion in the hydrogen gas and the arrival time of the \muμp atoms at the target walls. This laser-induced modification of the arrival times is used to expose the atomic transition. In this paper we present the simulation of the \muμp diffusion in the H_22 gas which is at the core of the experimental scheme. These simulations have been implemented with the Geant4 framework by introducing various low-energy processes including the motion of the H_22 molecules, i.e. the effects related with the hydrogen target temperature. The simulations have been used to optimize the hydrogen target parameters (pressure, temperatures and thickness) and to estimate signal and background rates. These rates allow to estimate the maximum time needed to find the resonance and the statistical accuracy of the spectroscopy experiment.

Influence of plasma parameters on low-k SiCOH film grown by plasma-enhanced chemical vapor deposition using dimethyldimethoxysilane

Here, we report the influence of the electron density and the electron temperature on the reduction of dielectric constant in the SiCOH thin film using dimethyldimethoxysilane (DMDMS) as a function of pressure. The measured electron density and electron temperature decreased as increasing the pressure. The decrease in the measured electron density with increasing pressure can be attributed to local electron kinetics. Moreover, the decreasing electron temperature is caused by increased inelastic collisions between electrons and neutral species in the chamber. It is identified that CH3 radicals are less dissociated from DMDMS molecular at higher pressure by a quadrupole mass spectroscopy. As increasing pressure, the increase of the Si–CH3 bonds in SiCOH thin films is confirmed by Fourier transform infrared spectroscopy. As a result, the dielectric constant and refractive index of the SiCOH films are reduced at low electron density and electron temperature.

Atmospheric Microplasma Treatment Based on Magnetically Controlled Fe–Al Dynamic Platform for Organic and Biomaterials Surface Modification

By exploiting the physical effect of the electron emission from a thermionic source in combination with a magnetically controlled Fe–Al dynamic platform to assist electrical discharge, we generated atmospheric microplasma (AM). The electrical characteristics of microplasma discharge-induced cold atmospheric plasma in combination with a magnetically controlled Fe–Al dynamic platform in open air were evaluated. The surface analysis of organic wheat seeds was investigated at two steps: (1) the coating effect of an Al nanoparticle with an electrons drift toward the seed surface along the direction of an electric field and (2) inelastic collision with secondary electrons moving from the cathode in the presence of an electric field. Using SEM microscopy analysis, it was found that plasma affects seed surface topography and apparent contact angle (ACA). The effect of atmospheric microplasma treatment leads to seed surface modification by the manifestation of fine mesh structures on the seed surface. Well-established AM technology will garner interest in agriculture and biomaterials coatings applications.

Evaluation of the effectiveness of energetic thermal electrons on the excitation of the ionospheric red 6300 Å airglow

In this paper we use previously calculated ionosphere electron temperatures Te in order to estimate the 6300 Å (red) airglow intensity enhancements attributed to thermal electrons from the tail of a Maxwellian electron distribution of sufficiently increased electron temperature. Then, we compare our results with the relevant observed measurements and we comment on the quality of the comparison and the possible causes of the differences. We also calculate the airglow intensity characteristic rise and decay times and compare them to the experimental ones, and we investigate the origin of the electrons which excite the red airglow. In the end, we assess the departure of the ionosphere electron energy distribution from a purely Maxwellian one, and the role of the electron elastic and inelastic collisions with the other components of the ionospheric F-region.

Microwave-activated Cu-doped zirconium metal-organic framework for a highly effective combination of microwave dynamic and thermal therapy

Percutaneous microwave ablation (PMA) is a thermoablative method used as a minimally invasive treatment for liver cancer. However, the application of PMA is limited by its insufficient ROS generation efficiency and thermal effects. Herein, a new microwave-activated Cu-doped zirconium metal-organic framework (MOF) (CuZr MOF) used for enhanced PMA has a significantly improved microwave sensitizing effect. Owing to the strong inelastic collisions between ions confined in numerous micropores, CuZr MOF has strong microwave sensitivity and high thermal conversion efficiency, which can significantly improve microwave thermal therapy (MTT). Moreover, because of the existence of Cu2+ ions, a further benefit of CuZr MOF is their Fenton-like activity, in particular, microwaves used as an excitation source for microwave dynamic therapy (MDT) can improve the Fenton-like reaction to maximize the synergistic effectiveness of cancer therapy. Importantly, CuZr MOF can inhibit the production of heat shock proteins (HSPs) by producing abundant ROS to enhance tumor destruction. Mechanistically, we found that CuZr MOF + MW treatment modulates ferroptosis-mediated tumor cell death by targeting the HMOX1/GPX4 axis. In summary, this study develops a novel CuZr MOF microwave sensitizer with great potential for synergistic treatment of liver cancer by MTT and MDT.

Bilinear form, auto-Bäcklund transformations, Pfaffian, soliton, and breather solutions for a (3 + 1)-dimensional extended shallow water wave equation

Study of the water waves remains central to fluid physics, ocean dynamics, and engineering. In this paper, a (3 + 1)-dimensional extended shallow water wave equation is investigated via symbolic computation. Bilinear form and two kinds of the bilinear auto-Bäcklund transformations with some solutions are given via the Hirota method. The Nth-order Pfaffian solutions are worked out by means of the Pfaffian technique, where N is a positive integer. N-soliton solutions are exported through the Nth-order Pfaffian solutions. By virtue of the asymptotic analysis, elastic and inelastic interactions between the two solitons on some periodic backgrounds are discussed. Interaction among the three solitons is illustrated graphically. The higher-order breather solutions are investigated via the complex parameter relation. Elastic and inelastic interactions between the two breathers on the periodic backgrounds are depicted graphically. Hybrid solutions consisting of the solitons and breathers are obtained. Interaction between the one soliton and one breather on a periodic background is presented.

Scattering cross sections and collision integrals for N(4S)–N+(3P) and N(4S)–N+(1D) interactions

Collisions between nitrogen (N) and nitrogen ion (N+) are fundamental phenomena in the Earth and planetary atmospheres. In this work, we carried out a theoretical study of collision data for N(4S)–N+(3P) and N(4S)–N+(1D) interactions, including scattering cross sections and collision integrals. Potential energy curves of N2+ are obtained using the state-of-the-art ab initio method and then used to provide the input for calculations of resonant charge exchange and elastic cross sections. The inelastic (corresponding to the resonant charge exchange process), elastic, and total collision integrals for N(4S)–N+(3P) and N(4S)–N+(1D) interactions are computed at 500 − 50 000 K. An analysis of the collision integrals shows that the elastic collision process should not be neglected for odd-order collision interactions at low temperatures and still makes a small contribution at high temperatures. Note that this is the first time that the cross sections and collision integrals for the N(4S)–N+(1D) interaction are calculated using ab initio potential energy points. The obtained cross sections and collision integrals are essential to model the transport properties of the related plasmas.

Tracer diffusion coefficients in a moderately dense granular suspension: Stability analysis and thermal diffusion segregation

The diffusion transport coefficients of a binary granular suspension where one of the components is present in tracer concentration are determined from the (inelastic) Enskog kinetic equation. The effect of the interstitial gas on the solid particles is accounted for in the kinetic equation through two different terms: (i) a viscous drag force proportional to the particle velocity and (ii) stochastic Langevin-like term defined in terms of the background temperature. The transport coefficients are obtained as the solutions of a set of coupled linear integral equations recently derived for binary granular suspensions with arbitrary concentration [Gómez González et al., “Enskog kinetic theory for multicomponent granular suspensions,” Phys. Rev. E 101, 012904 (2020)]. To achieve analytical expressions for the diffusion coefficients, which can be sufficiently accurate for highly inelastic collisions and/or disparate values of the mass and diameter rations, the above integral equations are approximately solved by considering the so-called second Sonine approximation (two terms in the Sonine polynomial expansion of the distribution function). The theoretical results for the tracer diffusion coefficient D0 (coefficient connecting the mass flux with the gradient of density of tracer particles) are compared with those obtained by numerically solving the Enskog equation by means of the direct simulation Monte Carlo method. Although the first-Sonine approximation to D0 yields, in general, a good agreement with simulation results, we show that the second-Sonine approximation leads to an improvement over the first-Sonine correction, especially when the tracer particles are much lighter than the granular gas. The expressions derived here for the diffusion coefficients are also used for two different applications. First, the stability of the homogeneous steady state is discussed. Second, segregation induced by a thermal gradient is studied. As expected, the results show that the corresponding phase diagrams for segregation clearly differ from those found in previous works when the effect of gas phase on grains is neglected.

Multi-degree-of-freedom kinetic model and its applications in simulation of three-dimensional nonequilibrium flows

A multi-degree-of-freedom (MDOF) kinetic model is developed to simulate three-dimensional nonequilibrium flows. By modifying collision term of Boltzmann model equation, a multi-scale molecular collision mechanism with translational, rotational and vibrational degrees of freedom is indicated by three coupled relaxation processes. Molecular vibration is modeled by harmonic oscillator. As a result, the degree of freedom of vibration may be directly related to temperature. Internal energy of various degrees of freedom are computed based on the equipartition theorem, and equilibrium distribution functions for each relaxation step are calculated. The present MDOF kinetic model is beneficial for assessing multi-scale evolutions of internal energy and molecular inelastic collisions. Several three-dimensional flow cases, including lid-driven cavity flow and hypersonic flows around a blunt cone at varying angles of attack, are simulated using the current MDOF technique. All numerical results were consistent with the reference data. It was shown that the proposed MDOF kinetic model well explains the vibration–rotation-translation energy exchange of polyatomic molecules in high-temperature gas, and that the current computational technique is a useful engineering tool for nonequilibrium aerodynamic research.

Search for Light Dark Matter from the Atmosphere in PandaX-4T.

We report a search for light dark matter produced through the cascading decay of η mesons, which are created as a result of inelastic collisions between cosmic rays and Earth's atmosphere. We introduce a new and general framework, publicly accessible, designed to address boosted dark matter specifically, with which a full and dedicated simulation including both elastic and quasielastic processes of Earth attenuation effect on the dark matter particles arriving at the detector is performed. In the PandaX-4T commissioning data of 0.63 tonne·year exposure, no significant excess over background is observed. The first constraints on the interaction between light dark matter generated in the atmosphere and nucleus through a light scalar mediator are obtained. The lowest excluded cross section is set at 5.9×10^{-37} cm^{2} for a dark matter mass of 0.1 MeV/c^{2} and mediator mass of 300 MeV/c^{2}. The lowest upper limit of η to the dark matter decay branching ratio is 1.6×10^{-7}.

Influence of Damping Particles on the Vibration of Spur Gear Transmission Using Numerical Modelization

The article numerically simulates the vibration reduction of a spur gear transmission by using damping particles placed in technological holes designed on the gear itself. The vibration of the gear transmission is reduced based on friction and inelastic collision which eliminates the vibrational energy by the loss during the motion of the damping particles within the technological holes. The kinematic processing of the gear system is analyzed using Adams software. The displacement acceleration data at the survey site is obtained from the Adams instrument which is valuable for evaluating the vibration level of the gear transmission. The interaction between the damping particles as well as the interaction between the particles with the gear model is simulated using EDEM software based on the discrete element method. The vibration of the gear transmission is assessed by the acceleration of the driven gear’s center of mass. The results show that the center of mass acceleration is remarkably reduced when particles are used at the rotation speed of 500 rpm and of 700 rpm. However, at the rotation speed of 1000 rpm, the vibration reduction is not much. This can be explained by the high speed and high inertia which cause the damping particles to rotate along with the gear, resulting in almost no collision between damping particles. The study also assesses the vibration reduction efficiency of the gear transmission according to the number of damping particles in each cavity and found that the number of particles accounting for 45.5% to 47.2% of the fill volume would reduce vibration most effectively. The three-millimeter diameter damper particles provide the most effective damping effect, at second place are the particles in four-millimeter diameter, and the least effective are those with two-millimeter diameter.

A novel Minkowski sum contact algorithm for arbitrarily shaped particles constructed by multiple dilated DEM models

Nonspherical granular materials are widely used in various industrial fields. Because the simulation of mixed granular flows consisting of arbitrarily shaped particles with smooth surfaces modeled by multiple discrete element models remains difficult for practical applications, a novel Minkowski sum contact algorithm in the CUDA-GPU architecture was proposed. In this algorithm, super-ellipsoidal equations, spherical harmonic functions, and polyhedrons were used to model differently shaped particles with smooth surfaces using the Fibonacci and Minkowski sum algorithms. Subsequently, single or multiple contact points between arbitrarily shaped particles were determined using the Minkowski sum contact algorithm. The automatic mesh simplification and GPU parallel computing methods were employed to improve the calculation efficiency of the discrete element method. The conservation, accuracy, and robustness of the proposed algorithm were verified by four sets of numerical examples: elastic collisions between particles, inelastic collisions between particles, accumulation of multiple particles, and dynamic granular flows. The relative DEM results show good agreement with the analytical solution, which indicates that the proposed Minkowski sum contact algorithm can accurately reflect the dynamic properties of arbitrarily shaped granular materials containing differently dilated DEM models.