Branching Ratio and Polarization of B→ρ(ω)ρ(ω)B\to\rho(\omega)\rho(\omega) Decays in Perturbative QCD Approach

In this work, we calculated the branching ratios, polarization fractions and CP asymmetry of decay modes $B\to\rho(\omega)\rho(\omega)$ in the Perturbative QCD approach, which is based on $\mathbf{k}_T$ factorization. After calculation, we find the the branching ratios of $B^0 \to \rho^+ \rho^-$, $B^+ \to \rho^+ \rho^0$ and $B^+ \to \rho^+ \omega$ are at the order of $10^{-5}$, and their longitudinal polarization fractions are more than 90%. The above results agree with BarBar's measurements. We also predict the branching ratios and polarizations of $B^0 \to \rho^0 \rho^0$, $B^0 \to \rho^0 \omega$ and $B^0 \to \omega \omega$, which will be measured in future. We predicted the CP asymmetry of $B^0 \to \rho^+ \rho^-$ and $B^+ \to \rho^+ \rho^0$, which will play important role in determining angle $\alpha$.Comment: 13 pages, 4 figure

Performance Analysis of Millimeter Wave Massive MIMO Systems in Centralized and Distributed Schemes

This paper considers downlink multi-user millimeter-wave massive multiple-input multiple-output (MIMO) systems in both centralized and distributed configurations, referred to as C-MIMO and D-MIMO, respectively. Assuming the fading channel is composite and comprised of both large-scale fading and small-scale fading, a hybrid precoding algorithm leveraging antenna array response vectors is applied into both the C-MIMO system with fully connected structure and the D-MIMO system with partially connected structure. First, the asymptotic spectral efficiency (SE) of an arbitrary user and the asymptotic average SE of the cell for the C-MIMO system are analyzed. Then, two radio access unit (RAU) selection algorithms are proposed for the D-MIMO system, based on minimal distance (D-based) and maximal signal-to-interference-plus-noise-ratio (SINR) (SINR-based), respectively. For the D-MIMO system with circular layout and D-based RAU selection algorithm, the upper bounds on the asymptotic SE of an arbitrary user and the asymptotic average SE of the cell are also investigated. Finally, numerical results are provided to assess the analytical results and evaluate the effects of the numbers of total transmit antennas and users on system performance. It is shown that, from the perspective of the cell, the D-MIMO system with D-based scheme outperforms the C-MIMO system and achieves almost alike performance compared with the SINR-based solution while requiring less complexity.Peer reviewe

Simultaneous observation of small- and large-energy-transfer electron-electron scattering in three dimensional indium oxide thick films

In three dimensional (3D) disordered metals, the electron-phonon (\emph{e}-ph) scattering is the sole significant inelastic process. Thus the theoretical predication concerning the electron-electron (\emph{e}-\emph{e}) scattering rate $1/\tau_\varphi$ as a function of temperature $T$ in 3D disordered metal has not been fully tested thus far, though it was proposed 40 years ago [A. Schmid, Z. Phys. \textbf{271}, 251 (1974)]. We report here the simultaneous observation of small- and large-energy-transfer \emph{e}-\emph{e} scattering in 3D indium oxide thick films. In temperature region of $T\gtrsim100$\,K, the temperature dependence of resistivities curves of the films obey Bloch-Gr\"{u}neisen law, indicating the films possess degenerate semiconductor characteristics in electrical transport property. In the low temperature regime, $1/\tau_\varphi$ as a function of $T$ for each film can not be ascribed to \emph{e}-ph scattering. To quantitatively describe the temperature behavior of $1/\tau_\varphi$, both the 3D small- and large-energy-transfer \emph{e}-\emph{e} scattering processes should be considered (The small- and large-energy-transfer \emph{e}-\emph{e} scattering rates are proportional to $T^{3/2}$ and $T^2$, respectively). In addition, the experimental prefactors of $T^{3/2}$ and $T^{2}$ are proportional to $k_F^{-5/2}\ell^{-3/2}$ and $E_F^{-1}$ ($k_F$ is the Fermi wave number, $\ell$ is the electron elastic mean free path, and $E_F$ is the Fermi energy), respectively, which are completely consistent with the theoretical predications. Our experimental results fully demonstrate the validity of theoretical predications concerning both small- and large-energy-transfer \emph{e}-\emph{e} scattering rates.Comment: 5 pages and 4 figure