Perturbative QCD analysis of Dalitz decays J/ψ→η(′)ℓ+ℓ−J/\psi\rightarrow\eta^{(\prime)}\ell^{+}\ell^{-}

In the framework of perturbative QCD, we study the Dalitz decays $J/\psi\rightarrow\eta^{(\prime)}e^{+}e^{-}$ with large recoil momentum. Meanwhile, the soft contributions from the small recoil momentum region and the VMD corrections have also been taken into account. The transition form factors $f_{\psi\eta^{(\prime)}}(q^{2})$ including the hard and soft contributions as well as the VMD corrections are calculated for the first time. By analytical evaluation of the involved one-loop integrals, we find that the transition form factors are insensitive to both the light quark masses and the shapes of $\eta^{(\prime)}$ distribution amplitudes. With the normalized transition form factors, our results of the branching ratios $\mathcal{B}(J/\psi\rightarrow\eta^{(\prime)}e^{+}e^{-})$ and their ratio $R_{J/\psi}^{e}=\mathcal{B}(J/\psi\rightarrow\eta e^{+}e^{-})/\mathcal{B}(J/\psi\rightarrow\eta^{\prime}e^{+}e^{-})$ are in good agreement with their experimental data. Furthermore, by the ratio $R_{J/\psi}^{e}$, we extract the mixing angle of $\eta-\eta^{\prime}$ system $\phi=34.0^{\circ}\pm0.6^{\circ}$ and comment on this result briefly. Inputting the mixing angle $\phi$ extracted from $R_{J/\psi}^{e}$, we predict the branching ratios $\mathcal{B}(J/\psi\rightarrow\eta\mu^{+}\mu^{-})=3.64\times10^{-6}$, $\mathcal{B}(J/\psi\rightarrow\eta^{\prime}\mu^{+}\mu^{-})=1.52\times10^{-5}$ and their ratio $R_{J/\psi}^{\mu}=23.9\%$.Comment: 14 pages, 9 figures and 5 table

Factorisable Multitask Quantile Regression

A multivariate quantile regression model with a factor structure is proposed to study data with many responses of interest. The factor structure is allowed to vary with the quantile levels, which makes our framework more flexible than the classical factor models. The model is estimated with the nuclear norm regularization in order to accommodate the high dimensionality of data, but the incurred optimization problem can only be efficiently solved in an approximate manner by off-the-shelf optimization methods. Such a scenario is often seen when the empirical risk is non-smooth or the numerical procedure involves expensive subroutines such as singular value decomposition. To ensure that the approximate estimator accurately estimates the model, non-asymptotic bounds on error of the the approximate estimator is established. For implementation, a numerical procedure that provably marginalizes the approximate error is proposed. The merits of our model and the proposed numerical procedures are demonstrated through Monte Carlo experiments and an application to finance involving a large pool of asset returns

Confidence Corridors for Multivariate Generalized Quantile Regression

We focus on the construction of confidence corridors for multivariate nonparametric generalized quantile regression functions. This construction is based on asymptotic results for the maximal deviation between a suitable nonparametric estimator and the true function of interest which follow after a series of approximation steps including a Bahadur representation, a new strong approximation theorem and exponential tail inequalities for Gaussian random fields. As a byproduct we also obtain confidence corridors for the regression function in the classical mean regression. In order to deal with the problem of slowly decreasing error in coverage probability of the asymptotic confidence corridors, which results in meager coverage for small sample sizes, a simple bootstrap procedure is designed based on the leading term of the Bahadur representation. The finite sample properties of both procedures are investigated by means of a simulation study and it is demonstrated that the bootstrap procedure considerably outperforms the asymptotic bands in terms of coverage accuracy. Finally, the bootstrap confidence corridors are used to study the efficacy of the National Supported Work Demonstration, which is a randomized employment enhancement program launched in the 1970s. This article has supplementary materials

A Novel Three-Point Modulation Technique for Fractional-N Frequency Synthesizer Applications

This paper presents a novel three-point modulation technique for fractional-N frequency synthesizer applications. Convention modulated fractional-N frequency synthesizers suffer from quantization noise, which degrades not only the phase noise performance but also the modulation quality. To solve this problem, this work proposes a three-point modulation technique, which not only cancels the quantization noise, but also markedly boosts the channel switching speed. Measurements reveal that the implemented 2.4 GHz fractional-N frequency synthesizer using three-point modulation can achieve a 2.5 Mbps GFSK data rate with an FSK error rate of only 1.4 %. The phase noise is approximately -98 dBc/Hz at a frequency offset of 100 kHz. The channel switching time is only 1.1 μs with a frequency step of 80 MHz. Comparing with conventional two-point modulation, the proposed three-point modulation greatly improves the FSK error rate, phase noise and channel switching time by about 10 %, 30 dB and 126 μs, respectively

Use of Devolved Controllers in Data Center Networks

In a data center network, for example, it is quite often to use controllers to manage resources in a centralized man- ner. Centralized control, however, imposes a scalability problem. In this paper, we investigate the use of multiple independent controllers instead of a single omniscient controller to manage resources. Each controller looks after a portion of the network only, but they together cover the whole network. This therefore solves the scalability problem. We use flow allocation as an example to see how this approach can manage the bandwidth use in a distributed manner. The focus is on how to assign components of a network to the controllers so that (1) each controller only need to look after a small part of the network but (2) there is at least one controller that can answer any request. We outline a way to configure the controllers to fulfill these requirements as a proof that the use of devolved controllers is possible. We also discuss several issues related to such implementation.Comment: Appears in INFOCOM 2011 Cloud Computing Worksho

Development Of Ultra High Frequency Energy Harvester Using Circular Spiral Array With Corporate Feeding

This thesis is to design an alternative antenna structure that will increase gain of the antenna, the amount of harvested energy and provide high power during rectification. The research works generate a steady output at a frequency of 956 MHz for RF energy harvesting system. The design of the circular spiral antenna is performed using Computer Simulation Technology (CST) and Advanced Designed System (ADS). The circular spiral antenna is integrated with the rectifying circuit to efficiently convert the input RF signal from alternating current (AC) to direct current (DC). Three configurations of the antenna designs were proposed namely single circular spiral antenna, 1x2 circular spiral antenna and 2x4 circular spiral antenna. The proposed antenna that had been developed is based on the basic antenna characteristic such as return loss, radiation pattern and gain. The 1x2 array antennas and 2x4 array antenna were designed using the corporate feed method that will increase the gain and enhanced the RF harvesting output voltage. The rectification of RF to DC energy used zero bias schottky diode that convert the incoming harvested energy. The results show that all the three design posses gain of 2.3 dBi, 3.2 dBi and 5 dBi, while the output voltage generated were 17 mV, 59.4 mV and 79 mV respectively. It is found also that the circular spiral antenna can provide a constant output DC voltage which is useful for UHF application