19ΛF 로부터의 감마선 측정 연구

학위논문(박사)--서울대학교 대학원 :자연과학대학 물리·천문학부,2016. 8. 최선호, Kiyoshi Tanida.A study of ΛN interaction is considered as the first step to extend the nucleon-nucleon world to the general baryon-baryon world. Due to short lifetime of Λ, spectroscopies of Λ hypernuclei have been the most powerful tool for the ΛN interaction study. Especially, excited energy levels of s-shell and p-shell Λ hypernuclei were precisely measured by gamma-ray spectroscopies, and it provided crucial information of the spin-dependent ΛN interaction. However, the experiments have been limited to light hypernuclei, so far. We performed a gamma-ray spectroscopy of 19ΛF, which is the first experiment of sd-shell hypernuclei. The experiment were carried out at K1.8 beamline in J-PARC hadron hall facility from May to June in 2015. 19ΛF hypernuclei were produced via (K-, pi-) reaction with the beam momentum 1.8 GeV/c and liquid CF4 target. The produced 19ΛF hypernuclei were idendified using Superconducting Kaon Spectrometer (SKS) and K1.8 beam line spectrometer. At the same time, gamma rays from the 19ΛF were detected by using a new germanium detector system (Hyperball-J). Four gamma rays from 19ΛF are observed at 315 keV, 895 keV, 1266 keV, and 953 keV. From the gamma rays, the energy spacing between the ground state spin doublet of 19ΛF is determined, and it is well represented by shell-model calculation estimated from ΛN spin-dependent interaction in p-shell hypernuclei. We expect the measured excitation energies of 19ΛF will provide important information of the spin-dependent interaction, especially the radial dependence of spin-spin interaction. The experiment will be also a guide for future experiments of heavier Λ hypernuclei.Chapter 1. Introduction 1 Chapter 2. Experimental Setup 14 Chapter 3. Analysis1 35 Chapter 4. Analysis2 60 Chapter 5. Results 76 Chapter 6. Discussion 100 Chapter 7. Conclusion 102 Bibliography 103 국문 초록 107Docto

Efficient Register Mapping and Allocation in LaTTe, an Open-Source Java Just-in-Time Compiler

IEEE Transactions on Parallel and Distributed Systems Volume 18 , Issue 1 (January 2007) Pages: 57-69Java just-in-time (JIT) compilers improve the performance of a Java virtual machine (JVM) by translating Java bytecode into native machine code on demand. One important problem in Java JIT compilation is how to map stack entries and local variables to registers efficiently and quickly, since register-based computations are much faster than memory-based ones, while JIT compilation overhead is part of the whole running time. This paper introduces LaTTe, an open-source Java JIT compiler that performs fast generation of efficiently register-mapped RISC code. LaTTe first maps "all local variables and stack entries into pseudoregisters, followed by real register allocation which also coalesces copies corresponding to pushes and pops between local variables and stack entries aggressively. Our experimental results indicate that LaTTe's sophisticated register mapping and allocation really pay off, achieving twice the performance of a naive JIT compiler that maps all local variables and stack entries to memory. It is also shown that LaTTe makes a reasonable trade-off between quality and speed of register mapping and allocation for the bytecode. We expect these results will also be beneficial to parallel and distributed Java computing 1) by enhancing single-thread Java performance and 2) by significantly reducing the number of memory accesses which the rest of the system must properly order to maintain coherence and keep threads synchronized

High resolution spectroscopy of the “Σ

We present a new proposal, J-PARC E90, to measure a missing-mass spectrum near the ΣN threshold for the d(K−, π−) reactions at 1.4 GeV/c. While many previous experiments support apparent enhancement near the ΣN thresh-old, the dynamical origin of this so-called “ΣN cusp” remains yet unsolved. The enhancement suggests either a cusp structure or a weakly bound state. One of the keys to making it clear is improving the missing-mass resolution and statistics. Our new experiment can achieve the missing-mass resolution of 0.4 MeV in σ using the K1.8 beam line and S-2S spectrometers at J-PARC. Further-more, we can suppress quasi-free background processes with the time projection chamber (HypTPC), which operated nicely for the H-dibaryon search experi-ment (J-PARC E42). The J-PARC E90 aims to extract the scattering length of the ΣN system with isospin T = 1/2 and spin-triplet channels