20,748 research outputs found

### Nucleon Resonances Near 2 GeV

The nucleon resonances near 2 GeV are investigated through the $\Sigma$(1385)
and $\Lambda(1520)$ photoproductions within a Regge-plus-resonance approach
based on the new experimental data released by the CLAS Collaboration. The
$\Delta(2000)$ and the $N(2120)$ are found essential to reproduce the
experimental data and should be assigned as second $[\Delta 5/2^+]$ and third
$[N3/2^-]$ in the constituent quark model, respectively. A calculation of the
binding energy and decay pattern supports that the $N(1875)$, which is listed
in the PDG as the third $N3/2^-$ nucleon resonance instead of the $N(2120)$, is
from the $\Sigma(1385)K$ 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

### $\bar{D}\Sigma^*_c$ and $\bar{D}^*\Sigma_c$ interactions and the LHCb hidden-charmed pentaquarks

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

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

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 $\Sigma_c^{(*)}$ baryon and a
$\bar{D}^{(*)}$ meson in a quasipotential Bethe-Salpeter equation approach. The
two-peak structure around 4450 MeV can be interpreted as two $\Sigma_c
\bar{D}^*$ bound states with spin parities $1/2^-$ and $3/2^-$. The newly
observed pentaquark $P_c(4312)$ can be assigned as a $\Sigma_c\bar{D}$ bound
state with spin parity $1/2^-$. 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

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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