11,973 research outputs found

    Nuclear suppression of ϕ\phi meson yields with large pTp_T at the RHIC and the LHC

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    We calculate ϕ\phi meson transverse momentum spectra in p+p collisions as well as their nuclear suppressions in central A+A collisions both at the RHIC and the LHC in LO and NLO with the QCD-improved parton model. We have included the parton energy loss effect in hot/dense QCD medium with the effectively medium-modified ϕ\phi fragmentation functions in the higher-twist approach of jet quenching. The nuclear modification factors of ϕ\phi meson in central Au+Au collisions at the RHIC and central Pb+Pb collisions at the LHC are provided, and a nice agreement of our numerical results at NLO with the ALICE measurement is observed. Predictions of yield ratios of neutral mesons such as ϕ/π0\phi/\pi^0, ϕ/η\phi/\eta and ϕ/ρ0\phi/\rho^0 at large pTp_T in relativistic heavy-ion collisions are also presented for the first time.Comment: 7 pages, 8 figure

    Optimization and Analysis of Wireless Powered Multi-antenna Cooperative Systems

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    In this paper, we consider a three-node cooperative wireless powered communication system consisting of a multi-antenna hybrid access point (H-AP) and a single-antenna relay and a single-antenna user. The energy constrained relay and user first harvest energy in the downlink and then the relay assists the user using the harvested power for information transmission in the uplink. The optimal energy beamforming vector and the time split between harvest and cooperation are investigated. To reduce the computational complexity, suboptimal designs are also studied, where closed-form expressions are derived for the energy beamforming vector and the time split. For comparison purposes, we also present a detailed performance analysis in terms of the achievable outage probability and the average throughput of an intuitive energy beamforming scheme, where the H-AP directs all the energy towards the user. The findings of the paper suggest that implementing multiple antennas at the H-AP can significantly improve the system performance, and the closed-form suboptimal energy beamforming vector and time split yields near optimal performance. Also, for the intuitive beamforming scheme, a diversity order of (N+1)/2 can be achieved, where N is the number of antennas at the H-AP

    Surrogate-Based Optimization

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