Hypernuclear study at Φ-Factoy

在2003年10月至2004年3月期间，利用意大利DafneΦ工厂的FINUDA探测器系统，积累了^6Li、^7Li、^&lt；12&gt；C、^&lt；27&gt；Al和^&lt；51&gt；V靶的超核数据，积分光度250PB；ΦK^-K^衰变产生的16 MeV几乎单色K束在超薄(~200 mg/cm~2)靶中被阻止。所有数据都被带回日本，并独立于意大利合作者进行分析。每个探测器的校准都在进行中。尽管加载室的位置分辨率仍未达到最佳值，但与K_&lt；μ2&gt；和K_&lt；π2&gt；衰变相对应的校准峰给出了正确的动量和相当好的动量分辨率。我们预计，该决议在未来的分析中可能会进一步完善。对于(K^-&lt；Stop&gt；，π^-)反应谱，我们得到了能量分辨率为1.45 MeV半高宽的ΛC激发能谱。到目前为止，这是世界上实现的最好的能源解决方案。一些峰结构是首次观察到的。即使对于较重的目标，也可以在束缚区域观察到事件。我们希望在未来的分析中能够解决几个激发态。在FINUDA探测器中，通过质子在Λ^-中的不变质量分布，成功地探测到了(K^-&lt；Stop&gt；，π^-)反应中的π超子。此外，我们还观察到一个Λ超子伴随着一个背靠背方向发射的质子。Λ-质子对的不变质量分布表明它们是从K_pp束缚系统中锥出来的。该体系的结合能为~115 MeV。与正常的核结合相比，这个值非常大，可能意味着系统中可能形成了高密度的核环境。Σ超核的产生也是通过标记来自强转换过程ΛNΣN的→Λ超子来搜索的。

The hypernuclear data on ^6Li, ^7Li, ^<12>C, ^<27>Al, and ^<51> V targets were accumulated during the fast data taking period from October 2003 to March 2004 with the FINUDA detector system at the DAFNE Φ-Factory in Italy The integrated luminosity of 250 pb^<-1> was delivered as scheduled. Almost mono-chromatic K- beam at 16 MeV produced from the ΦK^-K^+ decay was stopped in the very thin (〜200 mg/cm^2) targets. All the data were brought back to Japan and analyzed independently from the Italian collaborators. Calibrations for each detector have been in progress. Although the position resolutions of the tiadking chambers are still not at the optimum values, the calibration peaks corresponding to the K_<μ2> and K_<π2> decays gave us the correct momenta and reasonably good momentum resolutions. We expect the resolution could be further improved in the future analysis. As for the (K^-_<stop>,π^-) reaction spectroscopy, we have obtained ^<12>_ΛC excitation energy spectrum with the energy resolution of 1.45 MeV FWHM. This is as good as so-far the best energy resolution achieved it the world. A few peak structures were observed for the first time. Even for the heavier targets, events were observed in the bound region. We expect several excited states to be resolved in the future analysis.Λ hyperons in the (K^-_<stop>,π^-) reactions were successfully detected in the FINUDA detector from the invariant mass distribution of proton mid π^-. Further we have observed a Λ hyperon accompanied by a proton emitted in the back to-back direction. The invariant mass distribution of the Λ-proton pair indicates that they are coning out from a K_-pp bound system. The binding energy of the system was found to be〜115 MeV. This value is very large as compared to the normal nuclear binding and might imply a possible formation of high density nuclear environment in the system. Production of Σ hypernuclei was also searched by tagging the Λ hyperon from a strong conversion process ΣN→ΛN.