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arXiv 1011.0882nucl-ex
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ANKE ~ 3 He +η系统的测量

Measurements on the 3He+ηSystem at ANKE

A. Khoukaz

摘要:

在高精度高统计COSY-ANKE实验中测量了dp \to ~ 3 He η反应的微分截面和总截面。实验中采用了能量梯度上升到11.3MeV的连续束流,其接受度基本上为100%。运动学允许Q的平均值被确定为约9千电子伏。发现了Q > 4 MeV的高分波效应的证据。在0.5 MeV的阈值内,总截面迅速上升到最大值,这意味着η 3 He散射长度非常大,因此存在一个非常接近阈值的准束缚态。此外,微分和总截面已被测量在过剩能量为19.5,39.4,和59.4兆电子伏在整个角度范围内。虽然在19.5 MeV的结果可以描述在s-和p-波生产方面,由59.4 MeV更高的分波是必需的。在全局s波和p波拟合中包括19.5 MeV点以及近阈值数据,虽然对应于准束缚或虚拟状态的η 3 He散射振幅中的极点位置几乎没有改变,但对数据的总体描述较差。

英文摘要:

The differential and total cross-sections for the dp \to 3He ηreaction have been measured in a high precision high statistics COSY-ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy Q of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of Q to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for Q > 4 MeV. The very rapid rise of the total cross-section to its maximum value within 0.5 MeV of threshold implies a very large η3He scattering length and hence the presence of a quasi-bound state extremely close to threshold. In addition, differential and total cross-sections have been measured at excess energies of 19.5, 39.4, and 59.4 MeV over the full angular range. While at 19.5 MeV the results can be described in terms of s- and p-wave production, by 59.4 MeV higher partial waves are required. Including the 19.5 MeV point together with the near-threshold data in a global s- and p-wave fit gives a poorer overall description of the data though the position of the pole in the η3He scattering amplitude, corresponding to the quasi-bound or virtual state, is hardly changed.

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