20,748 research outputs found

    Nucleon Resonances Near 2 GeV

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    The nucleon resonances near 2 GeV are investigated through the Ξ£\Sigma(1385) and Ξ›(1520)\Lambda(1520) photoproductions within a Regge-plus-resonance approach based on the new experimental data released by the CLAS Collaboration. The Ξ”(2000)\Delta(2000) and the N(2120)N(2120) are found essential to reproduce the experimental data and should be assigned as second [Ξ”5/2+][\Delta 5/2^+] and third [N3/2βˆ’][N3/2^-] in the constituent quark model, respectively. A calculation of the binding energy and decay pattern supports that the N(1875)N(1875), which is listed in the PDG as the third N3/2βˆ’N3/2^- nucleon resonance instead of the N(2120)N(2120), is from the Ξ£(1385)K\Sigma(1385)K interaction rather than a three quark state.Comment: Talk given at the 10th International Workshop on the Physics of Excited Nucleons (NSTAR2015), Osaka, May 201

    DΛ‰Ξ£cβˆ—\bar{D}\Sigma^*_c and DΛ‰βˆ—Ξ£c\bar{D}^*\Sigma_c interactions and the LHCb hidden-charmed pentaquarks

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    Very recently, two hidden-charmed resonances Pc(4380)P_c(4380) and Pc(4450)P_c(4450) consistent with pentaquark states were observed at the LHCb detector. The two PcP_c states locate just below the DΛ‰Ξ£cβˆ—\bar{D}\Sigma^*_c and DΛ‰βˆ—Ξ£c\bar{D}^*\Sigma_c thresholds with mass of gaps about 5 and 15 MeV, respectively. Inspired by this fact we perform a dynamical investigation about the DΛ‰Ξ£cβˆ—(2520)\bar{D}\Sigma_c^*(2520) and DΛ‰βˆ—Ξ£c(2455)\bar{D}^*\Sigma_c(2455) interactions which are described by the meson exchanges. A bound state which carries spin-parity JP=3/2βˆ’J^P=3/2^- is produced from the DΛ‰Ξ£cβˆ—(2520)\bar{D}\Sigma^*_c(2520) interaction, which is consistent with the Pc(4380)P_c(4380) observed at the LHCb detector. From the Dβˆ—Ξ£c(2455)D^*\Sigma_c(2455) interaction, a bound state with 5/2+5/2^+ is produced, which can be related to the Pc(4450)P_c(4450). The results suggest that the Pc(4380)P_c(4380) and Pc(4450)P_c(4450) are good candidates of DΛ‰Ξ£cβˆ—(2520)\bar{D}\Sigma_c^*(2520) and DΛ‰βˆ—Ξ£c(2455)\bar{D}^*\Sigma_c(2455) molecular states, respectively.Comment: 5 pages, 3 figures, published version in Phys. Lett.

    Study of Pc(4457)P_c(4457), Pc(4440)P_c(4440), and Pc(4312)P_c(4312) in a quasipotential Bethe-Salpeter equation approach

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    Very recently, the LHCb Collaboration reported their new results about the pentaquarks at charm energy region. Based on the new experimental results, we recalculate the molecular states composed of a Ξ£c(βˆ—)\Sigma_c^{(*)} baryon and a DΛ‰(βˆ—)\bar{D}^{(*)} meson in a quasipotential Bethe-Salpeter equation approach. The two-peak structure around 4450 MeV can be interpreted as two Ξ£cDΛ‰βˆ—\Sigma_c \bar{D}^* bound states with spin parities 1/2βˆ’1/2^- and 3/2βˆ’3/2^-. The newly observed pentaquark Pc(4312)P_c(4312) can be assigned as a Ξ£cDΛ‰\Sigma_c\bar{D} bound state with spin parity 1/2βˆ’1/2^-. The experimental determination of spin parities will be very helpful to understand the internal structure of these pentaquarks.Comment: 4 pages. Version to be published on EPJ

    A Novel Genetic Algorithm using Helper Objectives for the 0-1 Knapsack Problem

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    The 0-1 knapsack problem is a well-known combinatorial optimisation problem. Approximation algorithms have been designed for solving it and they return provably good solutions within polynomial time. On the other hand, genetic algorithms are well suited for solving the knapsack problem and they find reasonably good solutions quickly. A naturally arising question is whether genetic algorithms are able to find solutions as good as approximation algorithms do. This paper presents a novel multi-objective optimisation genetic algorithm for solving the 0-1 knapsack problem. Experiment results show that the new algorithm outperforms its rivals, the greedy algorithm, mixed strategy genetic algorithm, and greedy algorithm + mixed strategy genetic algorithm
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