arXiv subjects

X. G. Wang

Publications and source records attributed to X. G. Wang.

45 records · Page 3Linked to original sources

arXiv2013

Study on X(3872) from effective field theory with pion exchange interaction

We study $D\bar{D}^*$ ($D^*\bar{D}$) scattering in the framework of unitarized heavy meson chiral perturbation theory with pion exchange and a contact interaction. $^3S_1-$$^3D_1$ mixing effects are taken into account. A loosely bound state X(3872), with the pole position being $M_{pole}=(3871.70-i0.39)\mathrm{MeV}$, is found. The result is not sensitive to the strength of the contact interaction. Our calculation provides a theoretical confirmation of the existence of the $1^{++}$ state X(3872). The light quark mass dependence of the pole position indicates it has a predominately $D\bar{D}^*$ ($D^*\bar{D}$) molecular nature. When the $π$ mass is larger than 142 MeV, the pole disappears which makes impossible the lattice simulation of this state at large quark mass.

hep-ph↗

arXiv2012

Study on $0^+$ states with open charm in unitarized heavy meson chiral approach

We calculate the scattering amplitudes of Goldstone bosons off the pseudoscalar D-mesons in unitarized heavy meson chiral approach. The low energy constants appearing in $\mathcal{O}(p^2)$ chiral Lagrangian are determined by fitting lattice simulations on $S$-wave scattering lengths. $D_{s0}^{*}(2317)$ is obtained as a bound state in $(S,I)=(1,0)$ $DK$ channel. Possible bound states or resonance states in other channels are investigated as well. The quark mass dependence of the mass and binding energy of $D_{s0}^{*}(2317)$ is also investigated, which indicates predominately $DK$ molecular nature.

hep-ph↗

arXiv2012

Pole Analysis of Unitarized One Loop $χ$PT Amplitudes - A Triple Channel Study

In a previous paper (Commun. Theor. Phys. 57 (2012) 841), we proposed a method to distinguish poles of different dynamical origin, in a unitarized amplitude of $ππ\, K\bar K$ system. That is based on the observation that `A Breit-Wigner resonance should exhibit two poles on different Riemann sheets which meet each other on the real axis when $N_c=\infty$'. In this paper, we extend our previous work (Commun.Theor.Phys. 57 (2012) 841) to the $ππ$-$K\bar K$-$ηη$ three channel system. We reconfirm most of the previous predictions. Especially the $f_0(980)$ is of $K\bar K$ molecule nature. Other poles, including the $σ$, are of Breit--Wigner type.

hep-ph↗

arXiv2011

Pole analysis on unitarized $SU(3)\times SU(3)$ one loop $χ$PT amplitudes

We analyze $ππ-K\bar{K}$ and $πη-K\bar{K}$ couple channel [1,1] matrix Padé amplitudes of $SU(3)\times SU(3)$ chiral perturbation theory. By fitting phase shift and inelasticity data, we determine pole positions in different channels ($f_0(980)$, $a_0(980)$,$f_0(600)$, $K_0^*(800)$, $K^*(892)$, $ρ(770)$) and trace their $N_c$ trajectories. We stress that a couple channel Breit--Wigner resonance should exhibit two poles on different Riemann sheets and meet each other on the real axis when $N_c=\infty$. Poles are hence classified using this criteria and we conclude that $K^*(892)$ and $ρ(770)$ are unambiguous Breit--Wigner resonances. For scalars the situation is much less clear. We find that $f_0(980)$ is a molecular state rather than a Breit--Wigner resonance, while $a_0(980)$, though behaves oddly when varying $N_c$, does maintain a twin pole structure.

hep-ph↗

arXiv2009

Investigations on the Property of $f_0(600)$ and $f_0(980)$ Resonances in $γγ\to ππ$ Process

Using dispersion relation technique and experimental data, a coupled channel analysis on $γγ\toππ$ process is made. Di-photon coupling of $f_0(600)$ and $f_0(980)$ resonances are extracted and their dynamical properties are discussed. Especially we study the physical meaning of the coupling constant $g^2_{σππ}$, which maintains a negative real part as determined through dispersive analyses.

hep-ph↗

arXiv2009

Spontaneous symmetry breaking in thermalization and anti-thermalization

The phenomenon of spontaneous symmetry breaking is investigated in the dynamic thermalization of a degenerate quantum system. A three-level system interacting with a heat bath is carefully studied to this end. It is shown that the three-level system with degenerate ground states might have different behaviors depending on the details of the interaction with the heat bath when the temperature approaches zero. If we introduce an external field to break the degeneracy of the ground states and let it approach zero after letting the temperature approach zero, then two possibilities will arise: the steady state is a definite one of the degenerate states independent of the initial state, or the steady state is dependent on the initial state in a complicated way. The first possibility corresponds to a spontaneous symmetry breaking of the system and the second one implies that the heat bath could not totally erase the initial information in certain cases.

quant-ph↗

arXiv2007

Satellite Observations of Separator Line Geometry of Three-Dimensional Magnetic Reconnection

Detection of a separator line that connects magnetic nulls and the determination of the dynamics and plasma environment of such a structure can improve our understanding of the three-dimensional (3D) magnetic reconnection process. However, this type of field and particle configuration has not been directly observed in space plasmas. Here we report the identification of a pair of nulls, the null-null line that connects them, and associated fans and spines in the magnetotail of Earth using data from the four Cluster spacecraft. With di and de designating the ion and electron inertial lengths, respectively, the separation between the nulls is found to be ~0.7di and an associated oscillation is identified as a lower hybrid wave with wavelength ~ de. This in situ evidence of the full 3D reconnection geometry and associated dynamics provides an important step toward to establishing an observational framework of 3D reconnection.

physics.plasm-ph↗

arXiv2007

In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth's magnetotail

Magnetic reconnection is one of the most important processes in astrophysical, space and laboratory plasmas. Identifying the structure around the point at which the magnetic field lines break and subsequently reform, known as the magnetic null point, is crucial to improving our understanding reconnection. But owing to the inherently three-dimensional nature of this process, magnetic nulls are only detectable through measurements obtained simultaneously from at least four points in space. Using data collected by the four spacecraft of the Cluster constellation as they traversed a diffusion region in the Earth's magnetotail on 15 September, 2001, we report here the first in situ evidence for the structure of an isolated magnetic null. The results indicate that it has a positive-spiral structure whose spatial extent is of the same order as the local ion inertial length scale, suggesting that the Hall effect could play an important role in 3D reconnection dynamics.

physics.plasm-ph↗

arXiv2003

Dynamics of the entanglement rate in the presence of decoherence

The dynamics of the entanglement rate are investigated in this paper for pairwise interaction and two special sets of initial states. The results show that for the given interaction and the decoherence scheme, the competitions between decohering and entangling lead to two different results--some initial states may be used to prepare entanglement while the others do not. A criterion on decohering and entangling is also presented and discussed.

quant-ph↗