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S. L. Wan

Publications and source records attributed to S. L. Wan.

10 recordsLinked to original sources
arXiv2007

Structure and decay constant of the ρmeson with Bethe-Salpeter equation

In this article, we study the structure of the ρmeson in the framework of the coupled rainbow Schwinger-Dyson equation and ladder Bethe-Salpeter equation with a confining effective potential. The u and d quark propagators get significantly modified, the mass poles are absent in the timelike region, which implements confinement naturally. The Bethe-Salpeter amplitudes of the ρmeson center around zero momentum and extend to the energy scale about $q^2=1GeV^2$, which happens to be the energy scale of chiral symmetry breaking, strong interactions in the infrared region result in bound state. The numerical results of the mass and decay constant of the ρmeson are in agreement with the experimental data.

hep-ph↗
arXiv2007

Analysis of the vector form factors $f^+_{Kπ}(Q^2)$ and $f^-_{Kπ}(Q^2)$ with light-cone QCD sum rules

In this article, we calculate the vector form factors $f^+_{Kπ}(Q^2)$ and $f^-_{Kπ}(Q^2)$ within the framework of the light-cone QCD sum rules approach. The numerical values of the $f^+_{Kπ}(Q^2)$ are compatible with the existing theoretical calculations, the central value of the $f^+_{Kπ}(0)$, $f^+_{Kπ}(0)=0.97$, is in excellent agreement with the values from the chiral perturbation theory and lattice QCD. The values of the $|f^-_{Kπ}(0)|$ are very large comparing with the theoretical calculations and experimental data, and can not give any reliable predictions. At large momentum transfers with $Q^2> 5GeV^2$, the form factors $f^+_{Kπ}(Q^2)$ and $|f^-_{Kπ}(Q^2)|$ can either take up the asymptotic behavior of $\frac{1}{Q^2}$ or decrease more quickly than $\frac{1}{Q^2}$, more experimental data are needed to select the ideal sum rules.

hep-ph↗
arXiv2006

Analysis of the vertices $D^*D_sK$, $D^*_sDK$,$D_0D_sK$ and $D_{s0}DK$ with the light-cone QCD sum rules

In this article, we analyze the vertices $D^*D_sK$, $D^*_sDK$, $D_0D_sK$ and $D_{s0}DK$ within the framework of the light-cone QCD sum rules approach in an unified way. The strong coupling constants $G_{D^*D_sK}$ and $G_{D^*_sDK}$ are important parameters in evaluating the charmonium absorption cross sections in searching for the quark-gluon plasmas, our numerical values of the $G_{D^*D_sK}$ and $G_{D^*_sDK}$ are compatible with the existing estimations although somewhat smaller, the SU(4) symmetry breaking effects are very large, about 60%. For the charmed scalar mesons $D_0$ and $D_{s0}$, we take the point of view that they are the conventional $c\bar{u}$ and $c\bar{s}$ mesons respectively, and calculate the strong coupling constants $G_{D_0 D_s K}$ and $G_{D_{s0} D K}$ with the vector interpolating currents. The numerical values of the scalar-$D_sK$ and -$DK$ coupling constants $G_{D_0 D_s K}$ and $G_{D_{s0} D K}$ are compatible with the existing estimations, the large values support the hadronic dressing mechanism. Furthermore, we study the dependence of the four strong coupling constants $G_{D^*D_sK}$, $G_{D^*_sDK}$, $G_{D_0D_sK}$ and $G_{D_{s0}DK}$ on the non-perturbative parameter $a_4$ of the twist-2 $K$ meson light-cone distribution amplitude.

hep-ph↗
arXiv2006

Ground state mass spectrum for scalar diquarks with Bethe-Salpeter equation

In this article, we study the structures of the pseudoscalar mesons $π$, $K$ and the scalar diquarks $U^a$, $D^a$, $S^a$ in the framework of the coupled rainbow Schwinger-Dyson equation and ladder Bethe-Salpeter equation with the confining effective potential. The $u$, $d$, $s$ quarks have small current masses, and the renormalization is very large, the mass poles in the timelike region are absent which implements confinement naturally. The Bethe-Salpeter wavefunctions of the pseudoscalar mesons $π$, $K$ and the scalar diquarks $U^a$, $D^a$, $S^a$ have the same type (Gaussian type) momentum dependence, center around zero momentum and extend to the energy scale about $q^2=1GeV^2$ which happen to be the energy scale for the chiral symmetry breaking, the strong interactions in the infrared region result in bound (or quasi-bound) states. The numerical results for the masses and decay constants of the $π$, $K$ mesons can reproduce the experimental values, the ground state masses of the scalar diquarks $U^a$, $D^a$, $S^a$ are consistent with the existing theoretical calculations. We suggest a new Lagrangian which may explain the uncertainty of the masses of the scalar diquarks .

hep-ph↗
arXiv2006

Structure of the $D_{s0}(2317)$ and the strong coupling constant $g_{D_{s0} D K}$ with the light-cone QCD sum rules

In this article, we take the point of view that the charmed scalar meson $D_{s0}(2317)$ is the conventional $c\bar{s}$ meson and calculate the strong coupling constant $g_{D_{s0} D K}$ within the framework of the light-cone QCD sum rules approach. The numerical values for the large scalar-$DK$ coupling constant $g_{D_{s0} D K}$ support the hadronic dressing mechanism. Just like the scalar mesons $f_0(980)$ and $a_0(980)$, the $D_{s0}(2317)$ may have small scalar $c\bar{s}$ kernel of the typical $c\bar{s}$ meson size. The strong coupling to the hadronic channels (or the virtual mesons loops) may result in smaller mass than the conventional scalar $c\bar{s}$ meson in the constituent quark models, and enrich the pure $c\bar{s}$ state with other components. The $D_{s0}(2317)$ may spend part (or most part) of its lifetime as virtual $ D K $ state.

hep-ph↗
arXiv2006

Visualizing high-temperature spin dynamics in La1-xCaxMnO3 from a mapping of EPR linewidth and g factor

This paper presents an analysis of electron paramagnetic resonance parameters, i.e., g factor, linewidth, and intensity on powder samples of La1-xCaxMnO3 at the commensurate carrier concentrations of x = N/8 (N = 1, 2, 3, 4, 5, 6, and 7). We demonstrate that the mapping of EPR parameters offers a powerful tool to investigate high-temperature spin dynamics in the phase diagram of colossal magnetoresistance (CMR) manganites. Our results convince that the spin-spin relaxation mechanism should dominate the high-temperature paramagnetic regime in CMR manganites.

cond-mat.str-el↗
arXiv2005

A new approach for calculating the Nambu-Gorkov propagator in color superconductivity theory

In this article, we propose a new approach to calculate the Nambu-Gorkov propagator intuitively with some linear algebra techniques in presence of the scalar diquark condensates. With the help of energy projective operators, we can obtain relatively simple expressions for the quark propagators, which greatly facilitate the calculations in solving the Schwinger-Dyson equation to obtain the gap parameters.

hep-ph↗
arXiv2002

Calculation of the quark condensate through Schwinger-Dyson equation

In this letter, we clarify the algebra expression for calculating the quark condensate based on the non-perturbative quark propagator calculated through Schwinger-Dyson equation. The quark condensates, which characterize the low energy QCD vacuum, should not get a divergent quantity at large energy scale; the re-normalization group evolution behaviour at large energy scale therefore should be interpreted as "smeared collective effects" for it contains both perturbative and non-perturbative parts. We prefer the integral expression and get a quantity which is both convergent and scale dependent.

hep-ph↗
arXiv2002

Dynamical symmetry breaking, confinement with flat-bottom potential

In this article, we calculate the dressed quark propagator with the flat bottom potential in the framework of the rain-bow Schwinger-Dyson equation. Then based on the nonperturbative dressed quark propagator, we calculate the $π$ decay constant and the quark condensate. The $π$ decay constant is an important parameter in describing the interplay between dynamical symmetry breaking and confinement, while the quark condensate is an order parameter for dynamical chiral symmetry breaking. To implement confinement, we prove that the dressed quark propagator has no poles on the real timelike $p^2$ axial, the absence of Kallen-Lehmann spectral representation obviously precludes the existence of free quarks.

hep-ph↗