用人工神经网络进行多参量模式识别的可行性研究

为了解决Ξ-、Ω等多奇异数重子鉴别效率低的问题,拟用人工神经网络来进行鉴别.这类多奇异数重子的特点是,判定它们所需参量数目很大(>10).用一个简单的蒙特卡洛模型研究了应用神经网络来识别多参量模式时需要解决的几个问题,所得到的结果支持用人工神经网络鉴别多参量模式的可行性.在此基础上,提出了一种混合运用拓扑重构和人工神经网络的混杂(hybrid)方法,作为提高多奇异数重子鉴别效率的一种可能的方法.

多奇异数重子鉴别中信号样本统计性问题的蒙特卡洛法研究

为了解决多奇异数重子两步拓扑重建效率低的问题,利用人工神经网络以较高的效率来一步完成对奇异粒子的鉴别。就高维参数空间中BP神经网络对训练样本高统计量要求的问题,进行了蒙特卡洛法研究,所得结论支持用人工神经网络鉴别多奇异数重子。

HERMES五夸克强子态Θ^+实验探索

一个新的强子态的实验证据在 2 7.6GeV正电子轰击氘靶产生的虚光子产物中被发现 .HERMES通过分析衰变道K0sp→π+π- p ,在K0sp不变质量谱上质量 15 2 8± 2 .6 (stat .)± 2 .1(sys .)MeV处观察到共振峰 .该共振峰可以被解释为理论预言的五夸克强子态Θ+(uudd s) .而K+p不变质量谱上未能观察到共振预示Θ+很可能是同位旋单态 .

Observation of e^(+)e^(-)→pppñπ-+c.c.

Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESⅢdetector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 fb^(-1),the process e^(+)e^(-)→pppñπ+c.c.is observed for the first time with a statistical significance of 11.5σ.The average Born cross sections in the energy ranges of(4.160,4.380)GeV,(4.400,4.600)GeV and(4.610,4.700)GeV are measured to be(21.5±5.7±1.2)fb,(46.3±10.6±2.5)fb and(59.0±9.4±3.2)fb,respectively,where the first uncertainties are statistical and the second are systematic.The line shapes of the pñ and ppπ^(-)invariant mass spectra are consistent with phase space distributions,indicating that no hexaquark or di-baryon state is observed.

Λ_c~* in a coupled-channel baryon-meson scattering

Possible structures and properties of some excited states of ∧^＋c dynamically generated in the coupled-channel P-wave meson-baryon scattering are studied by solving the Bethe-Salpeter（BS） equation in the framework of the Chiral Unitary Approach. It is shown that both ∧^＋c（2765） and ∧^＋c（2940） could be generated dynamically and could be compound states with multi-configuration molecular-like structures. The couplings of the generated states to various reaction channels are also calculated. Moreover, two highly excited states, ∧^＋c（3024） and ∧^＋c（3134）, are predicted.

Photoproduction of multi-meson final states–recent results from the Crystal-Barrel/TAPS experiment at ELSA-

Multi-meson final states such as γp →pπ0π0 and γp →pπ0η have been investigated with the Crystal-Barrel/TAPS experiment at ELSA. Baryon cascades via △π and △η and also via higher mass baryon resonances are clearly observed. Based on this data and on data from other reactions a partial wave analysis has been performed from which partial decay widths of various N＊ and △＊ states into the different pπ0π0 and pπ0η decay channels have been determined, leading partly to unexpected results. In addition, polarisation observables have been investigated. The beam asymmetry X has been determined for both reactions and double polarisation data using a longitudinally polarised target and a circularly or linearly polarised photon beam has been taken. Given the angular coverage of the Crystal-Baxrel/TAPS experiment this data covers almost the full angular range and phase space. This data will provide new and important information for the partial wave analyses and bring us one step closer towards a complete experiment.