Precise test of low energy QCD by measuring scattering lengths of pi+ pi- atoms -Lamb shift measurement of long lived pi+ pi- atoms in advanced DIRAC experiment -

2016 Fiscal Year Final Research Report

• Project/Area Number: 24340058
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Kyoto Sangyo University
• Principal Investigator: OKADA Kenji 京都産業大学, 名誉教授 (90093385)
• Co-Investigator(Kenkyū-buntansha): 岩下 芳久 京都大学, 化学研究所, 准教授 (00144387) ; 千葉 雅美 首都大学東京, 理工学研究科, 客員研究員 (60128577) ; 外山 政文 京都産業大学, コンピュータ理工学部, 教授 (60180189) ; 神谷 好郎 東京大学, 素粒子物理国際研究センター, 助教 (90434323)
• Co-Investigator(Renkei-kenkyūsha): KOBAYASHI Masaaki 高エネルギー加速器研究機構, 素粒子原子核研究所, 名誉教授 (40013388)
• Research Collaborator: TAKEUTCHI Fujio 京都産業大学, 名誉教授
• Project Period (FY): 2012-04-01 – 2017-03-31
• Keywords: ππ原子・πK原子 / ππ散乱長・πK散乱長 / ラムシフト / カイラル摂動計算 / 低エネルギー領域のQCD検証 / ππ原子・πK原子の寿命測定 / 準安定P状態 / CERN-PS加速器

Outline of Final Research Achievements

After investigating the pi+pi- atom with the ground state lifetime of 3.15×10－15 s, the DIRAC spectrometer was upgraded in order to study simultaneously pi+pi- and piK atoms.
The experiment at the CERN PS observed for the first time long-lived states of the pi+pi- atoms. The number of pion pairs resulting from the breakup of long-lived pi+pi- atoms amounts to 436 ± 61, corresponding to sigma=7.1. This observation opens a new possibility to measure energy differences between P and S atomic states (Lamb-shift) and so to determine another combination of pi-pi scattering lengths. The piK atoms are produced by 24 GeV/c protons interacting with Pt or Ni foil targets. The breakup of piK atoms in the targets yields characteristic piK pairs with small relative momenta in the pair center of mass system. The experiment observed 349 ± 62 such atomic piK pairs, corresponding to sigma= 5.6. This is the first statistically significant observation of the strange dimesonic piK atom.

Free Research Field

原子核素粒子実験物理学