Development of position sensitive Gamma-ray detector

对Λ(14 0 5)辐射衰变的测量可以给出Λ(14 0 5)的结构的重要信息，即是否为Kbar-N束缚态。在这项研究中，我们建议利用超子时间投影室来研制位置灵敏伽马射线探测器来研究Λ(1405)的辐射衰变，该超子投影室正在建设中，以探索J-Parc强子实验装置中H-双重子和三体强子共振的存在。基于GEANT4工具包，对Λ(1405)的分辨率和接受度进行了全面的模拟。根据重建的位置分辨率对伽玛探测器的尺寸进行了优化。假设探测器的段，对辐射衰变的接受率估计为83.3%，本底降低率超过85%。我们利用来自锶-90的β射线获得了时间分辨率与模数转换器增益的关系。MIP的估计时间分辨率约为130ps。然而，由于超导亥姆霍兹线圈的空间限制，人们希望使用薄塑料闪烁体。我们新制造了MPPC板，以优化增益和集光效率。测试板正在测试中，测试板将与TPC望远镜共享。9月在东北大学举行的HYP2015上展示了模拟和测试结果。此外，E42和E45协作会议上也报告了进展情况。

The measurement of radiative decay of the Λ(1405) can give important information of the structure of the Λ(1405), which is the Kbar-N bound state whether or not. In this research, we proposed to develop a position sensitive Gamma-ray-detector to study a radiative decay of the Λ(1405) by using Hyperon Time-Projection-Chamber, which is being built to explore an existence of the H-dibaryon and the 3-body hadronic nucleon resonances at the J-PARC hadron experimental facility.A full simulation was performed to estimate the resolution and acceptance of the Λ(1405) based on the GEANT4 toolkit. The size of the Gamma-ray-detector was optimized based on the reconstructed position resolution. By assuming the 64 segments of the detector, the acceptance of the radiative decay is estimated to be 83.3%, while the background reduction is obtained to be more than 85%.The test bench with 13 mm^2 size of MPPC and 2 x 1 x 80 cm^3 long plastic scintillator was performed. We obtained the timing resolution versus the ADC gain by using beta rays from Sr-90. The estimated timing resolution at MIP is about 130 ps. The thin plastic scintillator, however, is desired, because the space limitation of the super conducting Helmholtz-Coil was come. We newly fabricated new MPPC board to be optimize the gain and light collection efficiency. The board is being tested and the test board will be shared with the TPC hodoscope.The simulation and test results were presented at the HYP2015 at Tohoku University in Sep. In addition, the progress has been reported at the E42 and E45 collaboration meeting.