利用WASA-at-COSY和COSY-TOF装置生产η-介子核的可行性研究
Feasibility study of η-mesic nuclei production by means of the WASA-at-COSY and COSY-TOF facilities
摘要：
尽管早在1986年就提出了η介子与轻核通过强相互作用结合的η介子核的存在，但至今尚未得到实验证实。发现这种新的奇异的核物质是非常重要的，因为它可能有助于更好地理解η介子的结构及其与核子的相互作用。利用WASA探测系统，在德国于利希研究中心的COSY加速器上进行了η-氦束缚态的研究。对~ 4 He-η束缚态的自由产生进行了高统计和高接受度的搜索。同时也考虑了利用COSY-TOF装置在准自由反应中寻找η-氚。本文给出了η-氦束缚态和η-氚束缚态的蒙特卡罗模拟结果并进行了讨论。分别测定了WASA-at-COSY和COSY-TOF探测器对自由和准自由η介子核产生反应的接受度。此外，还比较了原子核内核子动量分布的三种不同模型和所考虑的束缚态宽度的三种不同值的可接受性。在COSY-TOF探测器中，当束流动量p_beam =3.1GeV/c时，可获得对准自由dd -> p_sp（T-η）_bs -> p_sp dpπ-反应的最有效测量。
英文摘要：
Despite the fact that existence of η-mesic nuclei in which the η meson might be bound with the light nucleus by means of the strong interaction was postulated already in 1986, it is still not experimentally confirmed. Discovering of this new kind of an exotic nuclear matter is very important as it might allow for better understanding of η meson structure and its interaction with nucleons. The search of the η-helium bound states is carried out at the COSY accelerator in the Research Center Juelich in Germany, by means of the WASA detection system. The search are conducted with high statistic and high acceptance for the free production of the 4He-η bound states. It is also considered to search for η-tritium in quasi free reaction which might be realised with COSY-TOF facility. In this thesis the results of the Monte Carlo simulations of the η-helium bound states and η-tritium bound state are presented and discussed. The acceptances of the WASA-at-COSY and COSY-TOF detectors for the free and quasi-free η-mesic nuclei production reactions were determined, respectively. Furthermore acceptances were compared for three different models of nucleon momentum distribution inside atomic nuclei and three different values of width of a considered bound states. In case of COSY-TOF detector it was established that the most effcient measurement of quasi-free dd --> p_sp (T-η)_bs --> p_sp dpπ- reaction can be done at beam momentum of p_beam =3.1GeV/c.
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