Study of Hyperon-Nucleon Interaction

我们在超核物理学中有了几个发现。在对KEK-E373实验获得的核乳胶进行分析时，我们发现了一些双超核。一个是^6He_ΛΛ核，它的质量得到了精确的测定。由该核的两个Λ的结合能，首次确定了ΛΛ相互作用是弱吸引的。这一结果对重子-重子相互作用模型的建立具有重要意义。超核的高精度γ能谱研究提供了非常丰富的物理结果。最近用Hyperball对^7Li、^9Be和^<16>O超核的测量几乎确定了ΛN自旋相关的相互作用，如自旋-自旋、自旋-轨道和张量相互作用。在KEK-PS上，我们进行了一个1.66GeV/c K- B的实验（E522），得到了一个很好的结果 关于我们 目的是研究可能的H-重子共振和N-重子相互作用。我们采用了最大的数据（K-，K+）反应与纤维活性靶。我们分析了计数器数据和由反射纤维获得的视觉数据。用计算机辅助扫描系统扫描了约40 k个（K-，K+）反应。其中，我们得到了约200个从（K-K+）反应顶点发射两个Λ的事例。两个Λ的不变质量谱在阈值附近出现一个峰，这可能表明H-重子共振的存在。我们在Spring-8上用激光康普顿γ束建立了一个时间投影室（TPC），用于研究超子共振。TPC的特征在于目标位于TPC内部。这使得探测飞行长度只有几厘米的低能超子衰变成为可能。主要目标是用核靶测量Λ（1405），以澄清其结构。我们已经研究了TPC的宇宙射线性质。在Θ和z方向上的位置分辨率分别达到300μm和500μm。2003年底，我们将TPC安装在超导螺线管中，并开始与γ束前向谱仪一起进行数据采集。TPC已经成功地在10^6 Hz的束流速率下运行。初步分析表明，TPC清晰地记录了带电粒子的轨迹。少

We have made several discoveries in hypernuclear physics. During the analysis of the nuclear emulsion obtained by KEK-E373 experiment, we found several double hypernuclei. One is ^6He_ΛΛ nucleus and its mass was precisely determined. From the binding energy of the two Λ of this nucleus, ΛΛ interaction was determined to be weakly attractive for the first time. The result is quite important to construct models of baryon-baryon was interaction. The high precision γray spectroscopy of hypernuclei has provided very rich physics results. Recent measurements with Hyperball for ^7Li,^9Be and ^<16>O hypernuclei have almost determined ΛN spin-dependent interaction, such as spin-spin, spin-orbit and tensor interaction. Especially, spin-orbit interaction determimed by a level splitting of 40kev of spin doublet states of ^9Be hypernucleus was found very weak compared to the nucleon-nucleon case by almost two orders of magnitude.At KEK-PS, we have performed an experiment (E522) with a 1.66GeV/c K- b … More eam to study a possible H-dibaryon resonance and ΞN interaction. We took a largest data for (K-,K+) reactions with a scintillating fiber active target. We have analyzed counter data and visual data obtained by the scintillating fiber. About 40k (K-,K+) reactions were scanned with computer-aided scanning system. Among them we have obtained about 200 events which show emission of two Λ from the (K-K+) reaction vertices. The invariant mass spectrum of the two Λ shows a peak near the threshold which may suggest the existence of H-dibaryon resonance.We have constructed a Time Projection Chamber (TPC) for the study of hyperon resonances with Laser Compton γ beam at Spring-8. The characteristics of the TPC is that a target is located inside the TPC. This makes it possible to detect decays of low energy hyperons which has only a few cm flight length. The primary goal is to measure Λ(1405) with nuclear targets to clarify its structure. We have studied the properties of the TPC with cosmic rays. We have obtained the position resolution of 300μm and 500μm in Θ and z directions, respectively. In the end of 2003, we installed the TPC in a superconducting solenoid and started data taking together with a forward spectrometer with the γbeam. The TPC has been successfully operated at the beam rate of 10^6 Hz. Preliminary analysis shows that charged particle tracks are clearly recorded by the TPC. Less