报告题目: A new doorway to study the fundamental baryon-baryon interaction under flavoured-SU(3): Hypernuclear physics with heavy ion beams and its perspective 

　　报告人：Dr. Take R. Saito 

　　（GSI Helmholtz Center for Heavy Ion Research） 

　　时间：2017年1月10日（星期二）上午10:00 

　　地点：近代物理所工艺楼6楼会议室 

　　报告摘要：Hypernclei, sub-atomic nuclei with bound hyperon(s), have been studied already for longer than a half century. It contributes to understand the fundamental baryon-baryon interaction under the flavoured-SU(3) symmetry. They have experimentally been studied mainly with secondary meson- and primary-electron beams at CERN, BNL, KEK, J-Lab, LNF INFN and J-PARC. Recently, hypernuclei are also studied by using heavy ion beams. The pioneering experiments with induced reactions of heavy ion projectiles has been performed at GSI by the HypHI collaboration which was started and is led by the speaker of this seminar. The first HypHI experiment, so called Phase 0, employed 6Li projectiles at 2 A GeV bombarded on the graphite target to produce light hypernuclei at projectile rapidity region. Produced hypernuclei were studied by means of the invariant mass method. In the analyses, light hypernuclei, 3H(Lambda) and 4H(Lambda) as well as Lambda-hyperons were successfully observed. The lifetime values of 3H(Lambda) and 4H(Lambda) as well as their production cross section and kinematics were deduced. One of the striking results of the HypHI Phase 0 experiment was to observe the significantly short lifetime of 3H(Lambda) than that of the Lambda-hyperon. Since the binding energy of Lambda in 3H(Lambda) was measured in 60’s to be  only approximately 130 keV, it has been believed since then that the lifetime of 3H(Lambda) should be equal to Lambda without any strong experimental evidence, and there are no theoretical calculations to reproduce the short lifetime of 3H(Lambda) observed by the HypHI collaboration so far. Very recently, the shortened 3H(Lambda) lifetime was also observed by the STAR collaboration at RHIC and the ALICE collaboration at LHC. In addition, the HypHI collaboration has observed an indication of the existence of an unknown neutral strange nucleus with two neutrons and Lambda, 3n(Lambda), to which all the theoretical calculations are negative for the existence of the bound state. These puzzles have been newly revealed only by the experiments with heavy ion beams. The hypernuclear experiments with heavy ion beams have opened a new doorway to study hypernuclei and the fundamental interactions with hyperons.