Spin correlations in polarizations of P-wave charmonia χcJ\chi_{cJ} and impact on J/ψJ/\psi polarization

Based on a general form of the effective vertex functions for the decays of P-wave charmonia \chicj, angular distribution formulas for the subsequent decays \chicj\rightarrow \jpsi \gamma and \jpsi \to \mu^+\mu^- are derived. The formulas are the same as those obtained in a different approach in the literature. Our formulas are expressed in a more general form, including parity violation effects and the full angular dependence of \jpsi and muon in the cascade decay \chicj\to\jpsi\gamma\to\mu^+\mu^-\gamma. The \chicj polarization observables are expressed in terms of rational functions of the spin density matrix elements of \chicj production. Generalized rotation-invariant relations for arbitrary integer-spin particles are also derived and their expressions in terms of observable angular distribution parameters are given in the $\chi_{c1}$ and $\chi_{c2}$. To complement our previous direct-\jpsi polarization result, we also discuss the impact on the observable prompt-\jpsi polarization. As an illustrative application of our angular distribution formulas, we present the angular distributions in terms of the tree-level spin density matrix elements of $\chi_{c1}$ and $\chi_{c2}$ production in several different frames at the Large Hadron Collider. Moreover, a reweighting method is also proposed to determine the entire set of the production spin density matrix elements of the $\chi_{c2}$, some of which disappear or are suppressed for vanishing higher-order multipole effects making the complete extraction difficult experimentally.Comment: Version published in PRD, 23 pages, 18 figure

A Novel Transmission Scheme for the KK-user Broadcast Channel with Delayed CSIT

The state-dependent $K$-user memoryless Broadcast Channel~(BC) with state feedback is investigated. We propose a novel transmission scheme and derive its corresponding achievable rate region, which, compared to some general schemes that deal with feedback, has the advantage of being relatively simple and thus is easy to evaluate. In particular, it is shown that the capacity region of the symmetric erasure BC with an arbitrary input alphabet size is achievable with the proposed scheme. For the fading Gaussian BC, we derive a symmetric achievable rate as a function of the signal-to-noise ratio~(SNR) and a small set of parameters. Besides achieving the optimal degrees of freedom at high SNR, the proposed scheme is shown, through numerical results, to outperform existing schemes from the literature in the finite SNR regime.Comment: 30 pages, 3 figures, submitted to IEEE Transactions on Wireless Communications (revised version

Ceramic dielectrics for high energy density capacity application

The objective of this dissertation is to investigate the relationship between the processing parameters, microstructural development, defect chemistry and electrical properties of titanium oxide (TiO₂) dielectrics for high energy density capacitor applications. The effects of aliovalent dopants on the dielectric properties of TiO₂ ceramics were investigated, aiming to further improve the desired dielectric properties especially at elevated temperatures (up to 200°C). Due to the segregation of acceptor type impurities in the starting powders, space charge polarization took place in TiO₂ ceramics with relative large grain size (\u3e̲500nm), leading to high dielectric loss and low energy storage efficiency. Increased ratio of grain boundary resistivity to bulk grain resistivity resulted in lower breakdown strength, as larger electric field was applied on the grain boundaries as they became the most resistive part. Donor doping (e.g phosphorus or vanadium) can effectively remove the space charge layer due to charge neutralization of positively charged defects created by donors and negatively charged defects created by acceptors. Large area, crack free tapes were fabricated by tape-casting method using nano-sized (~40nm) TiO₂ powders. An energy density of ~14 J/cm³ was demonstrated by testing of TiO₂ thick films (~100µm). Studies on dielectric materials were extended to BaTiO₃/SrTiO₃ (BST) ceramics which were processed by lamination of BaTiO₃ and SrTiO₃ green tapes with a 2-2 spatial configuration. Preliminary results showed that BST ceramics are promising dielectrics for energy storage applications and offer compositional flexibility to achieve maximum energy density under specified electric fields --Abstract, page iv