arXiv subjects

S. B. Wang

Publications and source records attributed to S. B. Wang.

11 recordsLinked to original sources

arXiv2026

Sensitivity of neutrinoless double beta decays from a combined analysis of ground and excited states

Next-generation neutrinoless double-beta ($0νββ$) decay experiments, with projected half-life sensitivities approaching $10^{28}$ years, aim to probe the entire parameter space of the inverted neutrino mass ordering in the light-neutrino-exchange scenario. However, this reach remains uncertain by the substantial model dependence of the nuclear matrix elements (NMEs). In this work, we propose a strategy based on a combined analysis of $0νββ$ decays to both the ground state and the first excited $0^+$ state of the daughter nucleus. We show that such a multi-channel approach can significantly enhance experimental sensitivity, depending on the underlying NME predictions. This method is particularly well-suited for large liquid xenon detectors, such as the proposed PandaX-xT and XLZD experiments, which can efficiently identify transitions of $^{136}$Xe to excited states. Our results highlight the importance of exploiting multiple decay channels in future $0νββ$ searches to maximize their discovery potential.

hep-ph↗

arXiv2023

System upgrade for $μ$Bq/m$^3$ level $^{222}$Rn concentration measurement

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multipurpose underground liquid scintillator detector, was proposed for the determination of the neutrino mass hierarchy as primary physics goal. The central detector will be submerged in a water Cherenkov detector to lower the background from the environment and cosmic muons. Radon is one of the primary background sources. Nitrogen will be used in several sub-systems, and a highly sensitive radon detector has to be developed to measure its radon concentration. A system has been developed based on $^{222}$Rn enrichment of activated carbon and $^{222}$Rn detection based on the electrostatic collection. This paper presents the detail of a $μ$Bq/m$^3$ level $^{222}$Rn concentration measurement system and gives detailed information about how the adsorption coefficient was measured and how the temperature, flow rate, and $^{222}$Rn concentration affect the adsorption coefficient.

physics.ins-det↗

arXiv2023

Developing a single phase liquid argon detector with SiPM readout

Liquid argon is used as a target material in several current and planned experiments related to dark matter direct searching and neutrino detection. SiPM is becoming the standard for scintillator detectors because of its advantages over traditional PMT. In this paper, we developed a single-phase liquid argon detector using eight 1 $\times$1 inch$^2$ Hamamatsu S14161-6050HS 4$\times$4 SiPM arrays. The directly measured light yield is 25.7 $\pm$ 1.6 photo-electrons per keV, which corresponds to 12.8 $\pm$ 0.8 photo-electrons primarily generated by the argon scintillation. The rest is contributed by the cross-talk and after-pulse of SiPM. In addition, we provide an experimental method to estimate the effect of crosstalk and afterpulse on light yield using dark noise data. Finally, we quantitatively give the relationship between the light yield and the decay time of the slow component of a liquid argon detector.

physics.ins-det↗

arXiv2019

Fast Multipole Boundary Element Method for Three Dimensional Electromagnetic Scattering Problem

We developed a fast numerical algorithm for solving the three dimensional vectorial Helmholtz equation that arises in electromagnetic scattering problems. The algorithm is based on electric field integral equations and is essentially a boundary element method. Nystrom's quadrature rule with a triangular grid is employed to linearize the integral equations, which are then solved by using a right-preconditioned iterative method. We apply the fast multipole technique to accelerate the matrix-vector multiplications in the iterations. We demonstrate the broad applications and accuracy of this method with practical examples including dielectric, plasmonic and metallic objects. We then apply the method to investigate the plasmonic properties of a silver torus and a silver split-ring resonator under the incidence of an electromagnetic plane wave. We show the silver torus can be used as a trapping tool to bind small dielectric or metallic particles.

physics.comp-ph↗

arXiv2015

Optical force on toroidal nanostructures: toroidal dipole versus renormalized electric dipole

We study the optical forces acting on toroidal nanostructures. A great enhancement of optical force is unambiguously identified as originating from the toroidal dipole resonance based on the source-representation, where the distribution of the induced charges and currents is characterized by the three families of electric, magnetic, and toroidal multipoles. On the other hand, the resonant optical force can also be completely attributed to an electric dipole resonance in the alternative field-representation, where the electromagnetic fields in the source-free region are expressed by two sets of electric and magnetic multipole fields based on symmetry. The confusion is resolved by conceptually introducing the irreducible electric dipole, toroidal dipole, and renormalized electric dipole. We demonstrate that the optical force is a powerful tool to identify toroidal response even when its scattering intensity is dwarfed by the conventional electric and magnetic multipoles.

physics.optics↗

arXiv2015

Analytic derivation of electrostrictive tensors and their application to optical force density calculations

Using multiple scattering theory, we derived for the first time analytical formulas for electrostrictive tensors for two dimensional metamaterial systems. The electrostrictive tensor terms are found to depend explicitly on the symmetry of the underlying lattice of the metamaterial and they also depend explicitly on the direction of a local effective wave vector. These analytical results enable us to calculate light induced body forces inside a composite system (metamaterial) using the Helmholtz stress tensor within the effective medium formalism in the sense that the fields used in the stress tensor are those obtained by solving the macroscopic Maxwell equation with the microstructure of the metamaterial replaced by an effective medium. Our results point to some fundamental questions of using an effective medium theory to determine optical force density. In particular, the fact that Helmholtz tensor carries electrostrictive terms that are explicitly symmetry dependent means that the standard effective medium parameters cannot give sufficient information to determine body force density, even though they can give the correct total force. A more challenging issue is that the electrostrictive terms are related to a local effective wave vector, and it is not always obtainable in systems with boundary reflections within the context of a standard effective medium approach.

physics.optics↗

arXiv2014

Lateral Optical Force On Chiral Particles Near a Surface

Light can exert radiation pressure on any object it encounters and that resulting optical force can be used to manipulate particles. It is commonly assumed that light should move a particle forward and indeed an incident plane wave with a photon momentum hk can only push any particle, independent of its properties, in the direction of k. Here we demonstrate using full-wave simulations that an anomalous lateral force can be induced in a direction perpendicular to that of the incident photon momentum if a chiral particle is placed above a substrate that does not break any left-right symmetry. Analytical theory shows that the lateral force emerges from the coupling between structural chirality (the handedness of the chiral particle) and the light reflected from the substrate surface. Such coupling induces a sideway force that pushes chiral particles with opposite handedness in opposite directions.

physics.optics↗

arXiv2013

Microwave induced elastic deformation of a metallic thin film

The microwave induced elastic deformation of a metallic thin film is computed numerically and we found that the deformation can be significantly enhanced at resonance. We show that an analytical transmission line model can reproduce the numerical results almost quantitatively and at the same time reveal the underlying physics.

physics.optics↗

arXiv2011

Sizable electromagnetic forces in parallel-plate metallic cavity

Using a boundary element method to calculate the electromagnetic fields and the Maxwell stress tensor method to compute the electromagnetic forces, we investigate electromagnetic wave induced forces acting on a pair of identical metal plates that forms an electromagnetic resonance cavity. Different frequency regimes are considered, from infrared frequencies with micron scale structures down to the microwave regime which involves millimeter scale structures. We found that at both length scales, the electromagnetic wave induced forces can be significantly stronger than the usual photon pressure exerted by a laser beam if the cavity is excited at resonance although the mechanisms that underlie the strong force are different at different length scales. In the infrared frequency regime, the strong force is induced by field penetration into the metal, whereas in the microwave regime, the electromagnetic force is induced by the leakage of electric field at the edges. At both frequency scales, we compare the results we obtained for Au metal plates with fictitious perfect electric conductor plates so as to understand the effect of field penetration. We also showed that a transmission line model can give simple expressions that can capture the essence of the physics. The effect of surface corrugation and surface roughness is also investigated, and we find that corrugation/roughness generally induces attraction between the plates.

physics.optics↗

arXiv2011

Strong plasmon coupling between two gold nanospheres on a gold slab

In this work, the plasmon coupling effect between two gold nanospheres on a gold slab is investigated. At plasmon resonance frequencies, electrons on the surface of the slab are absorbed into spheres and contribute to plasmon oscillation. This effect can help enhance the local electric field and optical coupling force between the two spheres.

physics.optics↗

arXiv2011

Strong light-induced negative optical pressure arising from the kinetic energy of conduction electrons in plasmonic cavities

We found that very strong negative optical pressure can be induced in plasmonic cavities by LC resonance. This interesting effect could be described qualitatively by a Lagrangian model which shows that the negative optical pressure is driven by the internal inductance and the kinetic energy of the conduction electrons. If the metal is replaced by perfect conductors, the optical pressure becomes much smaller and positive.

physics.optics↗