52,200 research outputs found

    Formation of \eta'(958)-mesic nuclei and axial U_A(1) anomaly at finite density

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    We discuss the possibility to produce the bound states of the η(958)\eta'(958) meson in nuclei theoretically. We calculate the formation cross sections of the η\eta' bound states with the Green function method for (γ\gamma,p) reaction and discuss the experimental feasibility at photon facilities like SPring-8. We conclude that we can expect to observe resonance peaks in (γ\gamma,p) spectra for the formation of η\eta' bound states and we can deduce new information on η\eta' properties at finite density. These observations are believed to be essential to know the possible mass shift of η\eta' and deduce new information of the effective restoration of the chiral UA(1)U_A(1) anomaly in the nuclear medium.Comment: 4 pages, 3 figure

    Differential symmetry breaking operators I : General theory and F-method

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    Determination of polarized parton distribution functions

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    We study parametrization of polarized parton distribution functions in the \alpha_s leading order (LO) and in the next-to-leading order (NLO). From \chi^2 fitting to the experimental data on A_1, optimum polarized distribution functions are determined. The quark spin content \Delta\Sigma is very sensitive to the small-x behavior of antiquark distributions which suggests that small-x data are needed for precise determination of \Delta\Sigma. We propose three sets of distributions and also provide FORTRAN library for our distributions.Comment: 1+5 pages, LATEX, aipproc.sty, 4 eps figures. Talk given at the 14th International Spin Physics Symposium, Osaka, Japan, October 16-21, 200

    Quantum network coding for quantum repeaters

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    This paper considers quantum network coding, which is a recent technique that enables quantum information to be sent on complex networks at higher rates than by using straightforward routing strategies. Kobayashi et al. have recently showed the potential of this technique by demonstrating how any classical network coding protocol gives rise to a quantum network coding protocol. They nevertheless primarily focused on an abstract model, in which quantum resource such as quantum registers can be freely introduced at each node. In this work, we present a protocol for quantum network coding under weaker (and more practical) assumptions: our new protocol works even for quantum networks where adjacent nodes initially share one EPR-pair but cannot add any quantum registers or send any quantum information. A typically example of networks satisfying this assumption is {\emph{quantum repeater networks}}, which are promising candidates for the implementation of large scale quantum networks. Our results thus show, for the first time, that quantum network coding techniques can increase the transmission rate in such quantum networks as well.Comment: 9 pages, 11figure

    A tight analysis of Kierstead-Trotter algorithm for online unit interval coloring

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    Kierstead and Trotter (Congressus Numerantium 33, 1981) proved that their algorithm is an optimal online algorithm for the online interval coloring problem. In this paper, for online unit interval coloring, we show that the number of colors used by the Kierstead-Trotter algorithm is at most 3ω(G)33 \omega(G) - 3, where ω(G)\omega(G) is the size of the maximum clique in a given graph GG, and it is the best possible.Comment: 4 page

    Lepton Energy Asymmetry and Precision SUSY study at Hadron Colliders

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    We study the distribution of lepton pairs from the second lightest neutralino decay \tilde{\chi}^0_2-->\tilde{l}l followed by \tilde{l}\to \tilde{\chi}^0_1 l. The distribution of the ratio of lepton transverse momenta A_T shows peak structure if m_{ll}< m^{max}_{ll}/2 is required. The peak position A_T^{peak} is described by a simple function of the ino and slepton masses in the m_{ll}\sim 0 limit. When a moderate m_{ll} cut is applied, A_T^{peak} depends on the \tilde{\chi}^0_2 velocity distribution, but the dependence would be corrected by studying the lepton P_T distribution. A_T^{peak} and the edge of m_{ll} distributions are used to determine the mass parameters involved in the decay for parameters of interest to LHC experiments. For some cases the ino and slepton masses may be determined within 10% by the lepton distribution only independent of model assumptions. Correct combinations of A_{T}^{peak} and m_{ll}^{edge} would be identified even if different \tilde{\chi}^0_2 decay chains are co-existing. The analysis could be extended to the Tevatron energy scale or other cascade decays.Comment: 31 pages, 15 figure