2007/10/24 by M. V. Zhabitsky · 12 citations
Physics and Astronomy · #Dirac (video compression format) #Dirac equation #Ground state #High-Energy Particle Collisions Research #Ionization #Momentum (technical analysis) #Nuclear physics research studies #Perturbation theory (quantum mechanics) #Quantum Chromodynamics and Particle Interactions #Spectral line #hep-ph
paper · pdf · doi:10.1134/s1063778808060082
published in Physics of Atomic Nuclei 71(6), 1040-1047 (Pleiades Publishing) · 11 pages, 4 figures; submitted to "Physics of Atomic Nuclei" ("Yadernaya Fizika")
arxiv created 2007/10/24 · openalex publication_date 2008/06/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The goal of the DIRAC experiment at CERN is the lifetime measurement of pionium (π + π − atom). Its lifetime is mainly defined by the charge-exchange process π + π − → π 0 π 0. The value of the lifetime in the ground state is predicted in the framework of chiral perturbation theory with high precision: τ 1S = (2.9 ± 0.1) × 10−15 s. The method used by DIRAC is based on analysis of π + π −-pair spectra with small relative momenta in their center-of-mass system in order to find out the signal from pionium ionization (breakup) in the target. Pioniums are produced in proton-nucleus collisions and have relativistic velocities (γ > 10). For fixed values of the pionium momentum and the target thickness, the probability of pionium ionization in the target depends on its lifetime in a unique way; thus, the pionium lifetime can be deduced from the experimentally defined probability of pionium ionization. On the basis of ionization cross sections of pionium with target atoms, we perform the first direct calculation of the pionium ionization probability in the target.