Identification of neutron sources and background levels in the polyethylene room of the China Jinping Underground Laboratory

The neutron backgrounds induced by supplementary experimental materials can result in contaminations in rare event search experiments. To address this, we present the neutron background levels arising from ambient materials in the polyethylene room of the China Jinping Underground Laboratory; particularly, we compare simulated spectra with measured neutron spectra unfolded using a genetic algorithm. The genetic algorithm optimizes the continuity of the energy spectra and obtains a reasonable spectral result. A good agreement between the unfolded and simulated spectra is achieved. Moreover, estimated neutron background levels of representative ambient materials such as polyethylene, aluminum, and lead are obtained using an exposure time of 511.27 days via a 28 liter 0.5%-gadolinium-doped liquid scintillator detector. The identification of rare neutron sources can aid in background reduction in next-generation large-scale rare event experiments.

Tentative evidence of spatially extended GeV emission from SS433/W50

We have analyzed ten years of the Fermi Large Area Telescope data toward the SS433/W50 region. With the latest source catalog and diffuse background models, the γ-ray excess from SS433/W50 is detected with a significance of ~6σ in the photon energy range of 500 MeV–10 GeV. Our analysis indicates that an extended flat disk morphology is preferred over a point-source description, suggesting that the GeV emission region is much larger than that of the TeV emission detected by the High Altitude Water Cherenkov (HAWC) telescope. The size of the GeV emission is instead consistent with the extent of the radio nebula W50, a supernova remnant being distorted by the jets, so we suggest that the GeV emission may originate from this supernova remnant. The spectral result of the GeV emission is also consistent with a supernova remnant origin. Furthermore, we derive the GeV flux upper limits on the TeV emission region, which put moderate constraints on the leptonic models to explain the multiwavelength data.

On anomalous localized resonance and plasmonic cloaking beyond the quasi-static limit

In this paper, we give the mathematical construction of novel core-shell plasmonic structures that can induce anomalous localized resonance and invisibility cloaking at certain finite frequencies beyond the quasi-static limit. The crucial ingredient in our study is that the plasmon constant and the loss parameter are constructed in a delicate way that are correlated and depend on the source and the size of the plasmonic structure. As a significant by-product of this study, we also derive the complete spectrum of the Neumann–Poincáre operator associated with the Helmholtz equation with finite frequencies in the radial geometry. The spectral result is the first one in its type and is of significant mathematical interest for its own sake.