Masses and decay constants of the heavy tensor mesons with QCD sum rules

In this article, we calculate the contributions of the vacuum condensates up to dimension-6 in the operator product expansion, study the masses and decay constants of the heavy tensor mesons $D_2^*(2460)$, $D_{s2}^*(2573)$, $B_2^*(5747)$, $B_{s2}^*(5840)$ using the QCD sum rules. The predicted masses are in excellent agreement with the experimental data, while the ratios of the decay constants $\frac{f_{D_{s2}^*}}{f_{D_{2}^*}}\approx\frac{f_{B_{s2}^*}}{f_{B_{2}^*}}\approx\frac{f_{D_{s}}}{f_{D}}\mid_{\rm exp}$, where the exp denotes the experimental value.Comment: 13 pages, 13 figure

Analysis of the scalar, axialvector, vector, tensor doubly charmed tetraquark states with QCD sum rules

In this article, we construct the axialvector-diquark-axialvector-antidiquark type currents to interpolate the scalar, axialvector, vector, tensor doubly charmed tetraquark states, and study them with QCD sum rules systematically by carrying out the operator product expansion up to the vacuum condensates of dimension 10 in a consistent way, the predicted masses can be confronted to the experimental data in the future. We can search for those doubly charmed tetraquark states in the Okubo-Zweig-Iizuka super-allowed strong decays to the charmed meson pairs.Comment: 23 pages, 29 figures. arXiv admin note: substantial text overlap with arXiv:1708.0454

Analysis of the DDˉ∗KD\bar{D}^*K system with QCD sum rules

In this article, we construct the color singlet-singlet-singlet interpolating current with $I\left(J^P\right)=\frac{3}{2}\left(1^-\right)$ to study the $D\bar{D}^*K$ system through QCD sum rules approach. In calculations, we consider the contributions of the vacuum condensates up to dimension-16 and employ the formula $\mu=\sqrt{M_{X/Y/Z}^{2}-\left(2{\mathbb{M}}_{c}\right)^{2}}$ to choose the optimal energy scale of the QCD spectral density. The numerical result $M_Z=4.71_{-0.11}^{+0.19}\,\rm{GeV}$ indicates that there exists a resonance state $Z$ lying above the $D\bar{D}^*K$ threshold to saturate the QCD sum rules. This resonance state $Z$ may be found by focusing on the channel $J/\psi \pi K$ of the decay $B\longrightarrow J/\psi \pi \pi K$ in the future.Comment: 9 pages, 4 figure

Implicit pension debt, transition cost, options, and impact of China's pension reform : a computable general equilibrium analysis

The main problems with China's pension system--the pension burdens of state enterprises and the agency of the population--have deepened in recent years. Using a new computable general equilibrium model that differentiates between three types of enterprise ownership and 22 groups in the labor force, the authors estimate the effects of pension reform in China, comparing various options for financing the transition cost. They examine the impact that various reform options would have on the system's sustainability, on overall economic growth, and on income distribution. The results are promising. The current pay-as-you-go system, with a notional individual account, remains unchanged in the first scenario examined. Simulations show this system to be unsustainable. Expanding coverage under this system would improve financial viability in the short run but weaken it in the long run. Other scenarios assume that the transition cost will be financed by various taxes and that a new, fully funded individual account will be established in 2001. The authors compare the impact of a corporate tax, a value-added tax, a personal income tax, and a consumption tax. They estimate the annual transition cost to be about 0.6 percent of Gross Domestic Product (GDP) between 2000 and 2010, declining to 0.3 percent by 2050. Using a personal income tax to finance the transition cost would best promote economic growth and reduce income inequality. Levying a social security tax and injecting fiscal resources to finance the transition costs would help make the reformed public pillar sustainable. To finance a benefit of 20 percent of the average wage, a contribution rate of only 10 percent-12.5 percent would be enough to balance the basic pension pillar. Gradually increasing the retirement age would further reduce the contribution rate.Pensions&Retirement Systems,Environmental Economics&Policies,Banks&Banking Reform,Economic Stabilization,National Governance

Electron-phonon coupling and superconductivity in LiB1+x_{1+x}C1−x_{1-x}

By means of the first-principles density-functional theory calculation and Wannier interpolation, electron-phonon coupling and superconductivity are systematically explored for boron-doped LiBC (i.e. LiB$_{1+x}$C$_{1-x}$), with $x$ between 0.1 and 0.9. Hole doping introduced by boron atoms is treated through virtual-crystal approximation. For the investigated doping concentrations, our calculations show the optimal doping concentration corresponds to 0.8. By solving the anisotropic Eliashberg equations, we find that LiB$_{1.8}$C$_{0.2}$ is a two-gap superconductor, whose superconducting transition temperature, T$_c$, may exceed the experimentally observed value of MgB$_2$. Similar to MgB$_2$, the two-dimensional bond-stretching $E_{2g}$ phonon modes along $\Gamma$-$A$ line have the largest contribution to electron-phonon coupling. More importantly, we find that the first two acoustic phonon modes $B_1$ and $A_1$ around the midpoint of $K$-$\Gamma$ line play a vital role for the rise of T$_c$ in LiB$_{1.8}$C$_{0.2}$. The origin of strong couplings in $B_1$ and $A_1$ modes can be attributed to enhanced electron-phonon coupling matrix elements and softened phonons. It is revealed that all these phonon modes couple strongly with $\sigma$-bonding electronic states.Comment: 7 pages, 10 figures, accepted for publication in EP