Upgraded DIRAC spectrometer at CERN PS for the investigation of ππ and πK atoms

详细信息    查看全文

• 作者：B. Adeva^a ; L. Afanasyev^b ; Y. Allkofer^c ; C. Amsler^d ; A. Anania^e ; S. Aogaki^f ; A. Benelli^h ; V. Brekhovskikh^g ; Gh. Caragheorgheopol^f ; T. Cechak^h ; M. Chibaⁱ ; P. Chliapnikov^g ; C. Ciocarlan^f ; S. Constantinescu^f ; C. Detraz^j ; P. Doskarova^h ; D. Drijard^j ; A. Dudarev^b ; M. Duma^f ; D. Dumitriu^f ; D. Fluerasu^f ; A. Gorin^g ; O. Gorchakov^b ; K. Gritsay^b ; C. Guaraldo^k ; M. Gugiu^f ; M. Hansroul^j ; Z. Hons^l ; S. Horikawa^c ; Y. Iwashita^m ; V. Karpukhin^b ; J. Kluson^h ; M. Kobayashiⁿ ; V. Kruglov^b ; L. Kruglova^b ; A. Kulikov^b ; E. Kulish^b ; A. Kuptsov^b ; A. Lamberto^e ; A. Lanaro^o ; R. Lednicky^p ; C. Mariñ ; as^a ; J. Martincik^h ; L. Nemenov^b ; ^j ; M. Nikitin^b ; K. Okada^q ; V. Olchevskii^b ; M. Pentia^f ; A. Penzo^r ; M. Plo^a
• 关键词：Upgraded DIRAC spectrometer ; CERN PS ; ππ and πK atoms ; Life-time measurement ; Long-lived excited states of ππ atoms
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2016
• 出版时间：11 December 2016
• 年：2016
• 卷：839
• 期：Complete
• 页码：52-85
• 全文大小：6079 K

文摘

The DIRAC spectrometer installed at CERN PS was upgraded in order to study simultaneously A_2π and A_πK atoms, namely the bound states of two π mesons, and of π and K mesons, respectively. The detector system can now accept a high intensity beam of 2–6×10¹¹ primary protons per second. The electronics and the data-acquisition system can handle a very large amount of data to identify π, K, p, e and µ, allowing the selection of ππ and πK pairs in the offline analysis. The resolution of the longitudinal and transverse components of the relative momentum Q of each meson pair in their center-of-mass system with respect to the direction of the pair was substantially improved. The analysis of their distributions allowed an reliable separation between the meson pairs originating from hadronic atoms and the backgrounds permitting the measurement of the lifetimes of hadronic atoms in the ground state and π–π, π–K s-wave scattering lengths. The upgraded setup also allowed the study of the long-lived excited states of ππ atoms.