First observation of long-lived pi(+)pi(-) atoms

0454048 - ÚJF 2016 RIV NL eng J - Journal Article
Adeva, B. - Benelli, A. - Čechák, T. - Doškářová, P. - Hons, Zdeněk - Klusoň, J. - Lednický, Richard - Martinčík, J. - Průša, P. - Trojek, T. - Urban, T. - Vrba, T. … Total 64 authors
First observation of long-lived pi(+)pi(-) atoms.
Physics Letters. B. Roč. 751, DEC (2015), s. 12-18. ISSN 0370-2693. E-ISSN 1873-2445
R&D Projects: GA MŠMT(CZ) LG13031
Institutional support: RVO:68378271 ; RVO:61389005
Keywords : DIRAC collaboration * scattering * pi K atoms
Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders; BF - Elementary Particles and High Energy Physics (FZU-D)
Impact factor: 4.787, year: 2015

After observing and investigating the double-exotic (adouble-exotic atom is a bound system, in which both oppositely charged components are unstable particles like mu, pi, K,...) pi(+)pi(-) atom with the ground state lifetime tau of about 3 x10(-15)s, the upgraded DIRAC experiment at the CERN PS accelerator observes for the first time long-lived states of the same atom with lifetimes of about 10(-11)s and more. The number of characteristic pion pairs resulting from the breakup (ionisation) of long-lived pi(+)pi(-) atoms amounts to 436 +/- 61, corresponding to a signal-to-error ratio of better than 7 standard deviations. This observation opens a new possibility to measure energy differences between p and s atomic states and so to determine pi pi scattering lengths.
Permanent Link: http://hdl.handle.net/11104/0254743