Determination of f0−σf_0-\sigma mixing angle through Bs0→J/Ψ f0(980)(σ)B_s^0 \to J/\Psi~f_0(980)(\sigma) decays

We study $B_s^0 \to J/\psi f_0(980)$ decays, the quark content of $f_0(980)$ and the mixing angle of $f_0(980)$ and $\sigma(600)$. We calculate not only the factorizable contribution in QCD facorization scheme but also the nonfactorizable hard spectator corrections in QCDF and pQCD approach. We get consistent result with the experimental data of $B_s^0 \to J/\psi f_0(980)$ and predict the branching ratio of $B_s^0 \to J/\psi \sigma$. We suggest two ways to determine $f_0-\sigma$ mixing angle $\theta$. Using the experimental measured branching ratio of $B_s^0 \to J/\psi f_0(980)$, we can get the $f_0-\sigma$ mixing angle $\theta$ with some theoretical uncertainties. We suggest another way to determine $f_0-\sigma$ mixing angle $\theta$ using both of experimental measured decay branching ratios $B_s^0 \to J/\psi f_0(980) (\sigma)$ to avoid theoretical uncertainties.Comment: arXiv admin note: substantial text overlap with arXiv:0707.263

Universal Thermoelectric Effect of Dirac Fermions in Graphene

We numerically study the thermoelectric transports of Dirac fermions in graphene in the presence of a strong magnetic field and disorder. We find that the thermoelectric transport coefficients demonstrate universal behavior depending on the ratio between the temperature and the width of the disorder-broadened Landau levels(LLs). The transverse thermoelectric conductivity $\alpha_{xy}$ reaches a universal quantum value at the center of each LL in the high temperature regime, and it has a linear temperature dependence at low temperatures. The calculated Nernst signal has a peak at the central LL with heights of the order of $k_B/e$, and changes sign near other LLs, while the thermopower has an opposite behavior, in good agreement with experimental data. The validity of the generalized Mott relation between the thermoelectric and electrical transport coefficients is verified in a wide range of temperatures.Comment: 4 pages, 4 figures, published versio

The study of B→J/Ψη(′)B\to J/\Psi \eta^{(\prime)} decays and determination of η−η′\eta-\eta^{\prime} mixing angle

We study $B\to J/\Psi \eta^{(\prime)}$ decays and suggest two methods to determine the $\eta-\eta^{\prime}$ mixing angle. We calculate not only the factorizable contribution in QCD facorization scheme but also the nonfactorizable hard spectator corrections in pQCD approach. We get the branching ratio of $B\to J/\Psi \eta$ which is consistent with recent experimental data and predict the branching ratio of $B\to J/\Psi \eta^{\prime}$ to be $7.59\times 10^{-6}$. Two methods for determining $\eta-\eta^{\prime}$ mixing angle are suggested in this paper. For the first method, we get the $\eta-\eta^{\prime}$ mixing angle to be about $-13.1^{\circ}$, which is in consistency with others in the literature. The second method depends on less parameters so can be used to determine the $\eta-\eta^{\prime}$ mixing angle with better accuracy but needs, as an input, the branching ratio for $B\to J/\Psi \eta^{\prime}$which should be measured in the near future.Comment: 16pages,4figure

CW-pumped telecom band polarization entangled photon pair generation in a Sagnac interferometer

A polarization entangled photon pair source is widely used in many quantum information processing applications such as teleportation, quantum swapping, quantum computation and high precision quantum metrology. Here, we report on the generation of a continuous-wave pumped degenerated 1550 nm polarization entangled photon pair source at telecom wavelength using a type-II phase-matched periodically poled KTiOPO4 crystal in a Sagnac interferometer. Hong-Ou-Mandel-type interference measurement shows the photon bandwidth of 2.4 nm. High quality of entanglement is verified by various kinds of measurements, for example two-photon interference fringes, Bell inequality and quantum states tomography. The wavelength of photons can be tuned over a broad range by changing the temperature of crystal or pump power without losing the quality of entanglement. This source will be useful for building up long-distance quantum networks