arXiv subjects

Hong Chen

Publications and source records attributed to Hong Chen.

306 records · Page 17Linked to original sources

arXiv2012

Charmonium states in QCD-inspired quark potential model using Gaussian expansion method

We investigate the mass spectrum and electromagnetic processes of charmonium system with the nonperturbative treatment for the spin-dependent potentials, comparing the pure scalar and scalar-vector mixing linear confining potentials. It is revealed that the scalar-vector mixing confinement would be important for reproducing the mass spectrum and decay widths, and therein the vector component is predicted to be around 22%. With the state wave functions obtained via the full-potential Hamiltonian, the long-standing discrepancy in M1 radiative transitions of $J/ψ$ and $ψ^{\prime}$ are alleviated spontaneously. This work also intends to provide an inspection and suggestion for the possible $c\bar{c}$ among the copious higher charmonium-like states. Particularly, the newly observed X(4160) and X(4350) are found in the charmonium family mass spectrum as $M(2^1D_2)= 4164.9$ MeV and $M(3^3P_2)= 4352.4$ MeV, which strongly favor the $J^{PC}=2^{-+}, 2^{++}$ assignments respectively. The corresponding radiative transitions, leptonic and two-photon decay widths have been also predicted theoretically for the further experimental search.

hep-ph↗

arXiv2012

Planar Metamaterial with Toroidal Moment

We observe toroidal response from a planar metamaterial comprised of asymmetric split ring resonators (ASRRs). It is showed that a toroidal-molecule can be constructed through rational arrangement of planar ASRRs as meta-atoms via manipulating structural symmetry of the meta-atoms. Field maps clearly indicate that the toroidal resonance paves new electromagnetic confinement style in a subwavelength scale. Planar scheme of manipulating the coupling among the ASRRs may stimulate research in optical region involving toroidal multipoles. Toroidal geometry together with the Fano resonance made high-Q response will have enormous potential applications in low-threshold lasing, cavity quantum electrodynamics and nonlinear processing.

physics.optics↗

arXiv2012

Advanced Multi-beam Spectrometer for the Green Bank Telescope

A new spectrometer for the Green Bank Telescope (GBT) is being built jointly by the NRAO and the CASPER, University of California, Berkeley. The spectrometer uses 8 bit ADCs and will be capable of processing up to 1.25 GHz bandwidth from 8 dual polarized beams. This mode will be used to process data from focal plane arrays. The spectrometer supports observing mode with 8 tunable digital sub-bands within the 1.25 GHz bandwidth. The spectrometer can also be configured to process a bandwidth of up to 10 GHz with 64 tunable sub-bands from a dual polarized beam. The vastly enhanced backend capabilities will support several new science projects with the GBT.

astro-ph.IM↗

arXiv2011

The possible candidates of tetraquark : $Z_b(10610)$ and $Z_b(10650)$

Using the chromomagnetic interaction Hamiltonian with proper account for the SU(3) flavor symmetry breaking, we have performed a schematic study on the masses of $S-$wave heavy tetraquarks as $bq\bar{b}\bar{q}$ ($q$ denotes $u$, $d$, $s$ quark). It is found that the numeral results for $bu\bar{b}\bar{d}$ or $bd\bar{b}\bar{u}$ with $1^{+}$ quantum number are 10612 MeV and 10683 MeV respectively, which are well compatible with the recent detected charged bottomonium-like $Z_b(10610)$ and $Z_b(10650)$. Theoretically, we also investigate the possible tetraquark states of $1^{++}$ and $2^{+}$ due to the charge conjugation as the potential candidates for the updating experiments.

hep-ph↗

arXiv2011

Low-threshold directional plasmon lasing assisted by spatially coherent surface plasmon polaritons

We theoretically propose directional, low-threshold plasmon lasing in both the near-infrared and visible wavelengths by utilizing spatially coherent surface plasmon polaritons on a meta-surface. The gain strength required for threshold lasing can be tuned down to a large extent through compatible structural parameters. Our calculations show that no more than 65 cm$^{-1}$ at 193.5 THz (1.55 $μ$m) or 267 cm$^{-1}$at 474THz (0.633 $μ$m) of gain coefficient is sufficient to compensate for the dissipation of metal films for threshold lasing; these values are smaller than any reported studies at the same frequencies. These findings present a planar solid-state route for plasmon lasing that is highly efficient and spatially coherent.

physics.optics↗

arXiv2011

Metallic helix array as a broadband wave plate

This study proposes that a metallic helix array can operate as a highly-transparent broadband wave plate in propagation directions perpendicular to the axis of helices. The functionality arises from a special property of the helix array, namely that the eigenstates of elliptically right-handed and left-handed polarization are dominated by Bragg scattering and local resonance respectively, and can be modulated separately with nearly fixed difference between their wavevectors in a wide frequency range. The wave plate functionality is theoretically and experimentally demonstrated by the transformation of polarized states in a wide frequency range.

physics.optics↗

arXiv2011

Determining the strange and antistrange quark distributions of the nucleon

The difference between the strange and antistrange quark distributions, $δs(x)=s(x)-\sbar(x)$, and the combination of light quark sea and strange quark sea, $Δ(x)=\dbar(x)+\ubar(x)-s(x)-\sbar(x)$, are originated from non-perturbative processes, and can be calculated using non-perturbative models of the nucleon. We report calculations of $δs(x)$ and $Δ(x)$ using the meson cloud model. Combining our calculations of $Δ(x)$ with relatively well known light antiquark distributions obtained from global analysis of available experimental data, we estimate the total strange sea distributions of the nucleon.

hep-ph↗

arXiv2011

Radiative vertex $VPγ$ and $η-η'$ mixing in light-cone sum rules

In this work, we calculate radiative vertex $VPγ$ ($V=ϕ,ω,ρ$ and $P=η,η'$) by utilizing $ω-ϕ$ mixing scheme and taking into account the contributions of the three-particle twist-4 distribution amplitudes of the photon in QCD sum rules on light cone. According to experimental data of $V\rightarrow Pγ$ and $P\rightarrow Vγ$ from PDG, a value of the $η-η^\prime$ mixing angle, $ϕ=(40.9\pm0.5)^\circ$, is extracted in the framework of the quark-flavor basis to describe the $η-η^\prime$ system.

hep-ph↗

arXiv2010

Spatially coherent surface resonance states derived from magnetic resonances

A thin metamaterial slab comprising a dielectric spacer sandwiched between a metallic grating and a ground plane is shown to possess spatially coherent surface resonance states that span a large frequency range and can be tuned by structural and material parameters. They give rise to nearly perfect angle-selective absorption and thus exhibit directional thermal emissivity. Direct numerical simulations show that the metamaterial slab supports spatially coherent thermal emission in a wide frequency range that is robust against structural disorder.

physics.optics↗

arXiv2010

Ferrimagnetic-like surface resonance from hybrid metamaterial slab

We show that a hybrid metamaterial slab comprising of an one-dimensional array of two different types of cavities exhibits ferrimagnetic-like surface resonances which can be used to realize interesting phenomena such as directive emission as a consequence of strong angle-dependent reflection phase and the selective coupling of a Gaussian incident beam into a higher order diffractive channel, giving rise to the phenomenon of negative reflection and retro-directive backtracking. The findings are verified by experiments in the microwave regime.

physics.optics↗

arXiv2008

Repulsive and restoring Casimir forces with left-handed materials

We investigate repulsive Casimir force between slabs containing left-handed materials with controllable electromagnetic properties. The sign of Casimir force is determined by the electric and magnetic properties of the materials, and it is shown that the formation of the repulsive force is related to the wave impedances of two slabs. The sign change of the Casimir force as a function of the distance is studied. Special emphasis is put on the restoring Casimir force which may be found to exist between perfectly conducting material and metamaterial slabs. This restoring force is a natural power for the system oscillation in vacuum and also can be used for system stabilization.

quant-ph↗

arXiv2007

Study of X(1812) as a $(K^\bar K^)$ Molecular State

We investigate the decay and the production mechanism of the resonance X(1812) recently observed in the $\jp\toγX(1812), X(1812)\toωϕ$ at BESII. The decay widths of $X(1812)\toηη'$,$ ηη$,$ ωϕ$,$ K^+K^-$,$ ρ^+ρ^-$, $ ωω$,$ K^{*+}K^{*-}$ and $π^+π^-$ are evaluated based on the scenario of the X(1812) as a candidate of $(\ksks)$ molecule. It turns out that the quark exchange mechanism plays an important role in the understanding of the large decay width for the $X(1812)\toωϕ$. It is also found that the decay widths for $X(1812)\toηη'$ and $ηη$ are enhanced by the quark exchange mechanism. These channels are suggested to be the tools to test the molecular scenario in experiment. The branching fraction of $Br(X\toωϕ)$ is evaluated to be about 4.60%. Searches for additional evidence about the X(1812) in $\jp$ radiative decays are reviewed. In the molecular scenario, the X(1812) production rate is also evaluated to be $Γ(\jp\toγX)/Γ(\jp\toγK^{*+}K^{*-})=2.13^{+7.41}_{-1.85}$, which is close to the measured value $2.83\pm0.92$.

hep-ph↗

arXiv2006

Rescattering effects of baryon and antibaryon in heavy quarkonium decays

Rescattering effects of baryon and antibaryon in heavy quarkonium decays are investigated by studying their angular distributions. The rescattering amplitudes are phenomenologically evaluated by modeling the intermediate range interaction as a $σ$ or pion meson exchange between $\qqbar$ quarks. The results show that the rescattering effects play an important role in determination of the angular distribution in heavy quarkonium decays. Especially, for $J/psi$ and $ψ'$ decays into $Λ\bar Λ$, $Σ^0\bar Σ^0$ and $Ξ^-\bar Ξ^+$ the angular distribution parameters could turn to be negative values in the limit of helicity conservation. These results provide us a possible explanation for understanding the negative sign of the angular distribution parameter measured for $J/psi \toΣ^0\barΣ^0$, namely, {\it it might come from the baryonic SU(3)$_F$ symmetry breaking by incorporating rescattering effects

hep-ph↗

arXiv2005

Negative and Positive Lateral Shift of a Light Beam Reflected from a Grounded Slab

We consider the lateral shift of a light beam reflecting from a dielectric slab backed by a metal. It is found that the lateral shift of the reflected beam can be negative while the intensity of reflected beam is almost equal to the incident one under a certain condition. The explanation for the negativity of the lateral shift is given in terms of the interference of the reflected waves from the two interfaces. It is also shown that the lateral shift can be enhanced or suppressed under some other conditions. The numerical calculation on the lateral shift for a realistic Gaussian-shaped beam confirms our theoretical prediction.

physics.optics↗

arXiv2003

Spin-polarized reflection of electrons in a two-dimensional electron system

We present a method to create spin-polarized beams of ballistic electrons in a two-dimensional electron system in the presence of spin-orbit interaction. Scattering of a spin-unpolarized injected beam from a lithographic barrier leads to the creation of two fully spin-polarized side beams, in addition to an unpolarized specularly reflected beam. Experimental magnetotransport data on InSb/InAlSb heterostructures demonstrate the spin-polarized reflection in a mesoscopic geometry, and confirm our theoretical predictions.

cond-mat.mes-hall↗

arXiv2002

Nonadiabatic approach to dimerization gap and optical absorption coefficient of the Su-Schrieffer-Heeger model

An analytical nonadiabatic approach has been developed to study the dimerization gap and the optical absorption coefficient of the Su-Schrieffer-Heeger model where the electrons interact with dispersive quantum phonons. By investigating quantitatively the effects of quantum phonon fluctuations on the gap order and the optical responses in this system, we show that the dimerization gap is much more reduced by the quantum lattice fluctuations than the optical absorption coefficient is. The calculated optical absorption coefficient and the density of states do not have the inverse-square-root singularity, but have a peak above the gap edge and there exist a significant tail below the peak. The peak of optical absorption spectrum is not directly corresponding to the dimerized gap. Our results of the optical absorption coefficient agree well with those of the experiments in both the shape and the peak position of the optical absorption spectrum.

cond-mat.str-el↗

arXiv2001

Spin-Peierls transition in an anisotropic two-dimensional XY model

The two-dimensional Jordan-Wigner transformation is used to investigate the zero temperature spin-Peierls transition for an anisotropic two-dimensional XY model in adiabatic limit. The phase diagram between the dimerized (D) state and uniform (U) state is shown in the parameter space of dimensionless interchain coupling $h$ $(=J_{\perp}/J)$ and spin-lattice coupling $η$. It is found that the spin-lattice coupling $η$ must exceed some critical value $η_c$ in order to reach the D phase for any finite $h$. The dependence of $η_c$ on $h$ is given by $-1/\ln h$ for $h\to 0$ and the transition between U and D phase is of first-order for at least $h>10^{-3}$.

cond-mat.str-el↗

arXiv1992

Lattice QCD with 8 Light Quark Flavors

QCD with eight flavors is studied on $16^3\times N_t$ lattices with $N_t=4$, 6, 8, 16 and 32, a dynamical quark mass $ma=0.015$ and lattice coupling $β=6/g^2$ between 4.5 and 5.0. For $N_t=16$ and 32, hadron masses and screening lengths are computed for a variety of valence quark masses. The previously observed, strong, first-order transition for $N_t=4$, 6 and 8 is seen, for $N_t=16$, to become a $β$-independent, zero-temperature transition characterized by a factor of $\approx 3$ change in lattice scale. This strong, first-order transition restores chiral symmetry, at least for $N_t=4$, 6 and 8, producing a chirally symmetric, weak-coupling phase. However, as $N_t$ increases to 16, the chiral symmetry properties of the weak-coupling side of the zero-temperature transition are unclear and offer a hint of a normal, finite-temperature, chiral symmetry breaking transition in the weak-coupling phase.

hep-lat↗