First Measurement of a Long-Lived π+π Atom Lifetime

Adeva, B. (Santiago de Compostela University, Santiago de Compostela, Spain) ; Afanasyev, L. (JINR, Dubna, Russia) ; Anania, A. (INFN, Sezione di Trieste and Messina University, Messina, Italy) ; Aogaki, S. (IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest, Romania) ; Benelli, A. (Czech Technical University in Prague, Prague, Czech Republic) ; Brekhovskikh, V. (IHEP, Protvino, Russia) ; Cechak, T. (Czech Technical University in Prague, Prague, Czech Republic) ; Chiba, M. (Tokyo Metropolitan University, Tokyo, Japan) ; Chliapnikov, P. V. (IHEP, Protvino, Russia) ; Doskarova, P. (Czech Technical University in Prague, Prague, Czech Republic) ; Drijard, D. (CERN, Geneva, Switzerland) ; Dudarev, A. (JINR, Dubna, Russia) ; Dumitriu, D. (IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest, Romania) ; Fluerasu, D. (IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest, Romania) ; Gorin, A. (IHEP, Protvino, Russia) ; Gorchakov, O. (JINR, Dubna, Russia) ; Gritsay, K. (JINR, Dubna, Russia) ; Guaraldo, C. (INFN, Laboratori Nazionali di Frascati, Frascati, Italy) ; Gugiu, M. (IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest, Romania) ; Hansroul, M. (CERN, Geneva, Switzerland) ; Hons, Z. (Nuclear Physics Institute ASCR, Rez, Czech Republic) ; Horikawa, S. (Zurich University, Zurich, Switzerland) ; Iwashita, Y. (Kyoto University, Kyoto, Japan) ; Karpukhin, V. (JINR, Dubna, Russia) ; Kluson, J. (Czech Technical University in Prague, Prague, Czech Republic) ; Kobayashi, M. (KEK, Tsukuba, Japan) ; Kruglov, V. (JINR, Dubna, Russia) ; Kruglova, L. (JINR, Dubna, Russia) ; Kulikov, A. (JINR, Dubna, Russia) ; Kulish, E. (JINR, Dubna, Russia) ; Lamberto, A. (INFN, Sezione di Trieste and Messina University, Messina, Italy) ; Lanaro, A. (CERN, Geneva, Switzerland) (University of Wisconsin, Madison, Wisconsin USA) ; Lednicky, R. (Institute of Physics ASCR, Prague, Czech Republic) ; Mariñas, C. (Santiago de Compostela University, Santiago de Compostela, Spain) ; Martincik, J. (Czech Technical University in Prague, Prague, Czech Republic) ; Nemenov, L. (JINR, Dubna, Russia) (CERN, Geneva, Switzerland) ; Nikitin, M. (JINR, Dubna, Russia) ; Okada, K. (Kyoto Sangyo University, Kyoto, Japan) ; Olchevskii, V. (JINR, Dubna, Russia) ; Ovsiannikov, V. (Voronezh State University, Voronezh, Russia) ; Pentia, M. (IFIN-HH, National Institute for Physics and Nuclear Engineering, Bucharest, Romania) ; Penzo, A. (INFN, Sezione di Trieste, Trieste, Italy) ; Plo, M. (Santiago de Compostela University, Santiago de Compostela, Spain) ; Prusa, P. (Czech Technical University in Prague, Prague, Czech Republic) ; Rappazzo, G. F. (INFN, Sezione di Trieste and Messina University, Messina, Italy) ; Romero Vidal, A. (Santiago de Compostela University, Santiago de Compostela, Spain) ; Ryazantsev, A. (IHEP, Protvino, Russia) ; Rykalin, V. (IHEP, Protvino, Russia) ; Saborido, J. (Santiago de Compostela University, Santiago de Compostela, Spain) ; Schacher, J. (Albert Einstein Center for Fundamental Physics, LHEP, Bern, Switzerland) ; Sidorov, A. (IHEP, Protvino, Russia) ; Smolik, J. (Czech Technical University in Prague, Prague, Czech Republic) ; Takeutchi, F. (Kyoto Sangyo University, Kyoto, Japan) ; Trojek, T. (Czech Technical University in Prague, Prague, Czech Republic) ; Trusov, S. (Skobeltsin Institute for Nuclear Physics of Moscow State University, Moscow, Russia) ; Urban, T. (Czech Technical University in Prague, Prague, Czech Republic) ; Vrba, T. (Czech Technical University in Prague, Prague, Czech Republic) ; Yazkov, V. (Skobeltsin Institute for Nuclear Physics of Moscow State University, Moscow, Russia) ; Yoshimura, Y. (KEK, Tsukuba, Japan) ; Zrelov, P. (JINR, Dubna, Russia)

01 March 2019

Abstract: The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogenlike π+π atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96 mm between the target and a 2.1 μm thick platinum foil, in which most of them dissociated. Analyzing the observed number of atomic pairs, nAL=43661+157|tot, the lifetime of the 2p state is found to be τ2p=(0.450.30+1.08|tot)×1011 s, not contradicting the corresponding QED 2p state lifetime τ2pQED=1.17×1011 s. This lifetime value is three orders of magnitude larger than our previously measured value of the π+π atom ground state lifetime τ=(3.150.26+0.28|tot)×1015 s. Further studies of long-lived π+π atoms will allow us to measure energy differences between p and s atomic states and so to discriminate between the isoscalar and isotensor ππ scattering lengths with the aim to check QCD predictions.


Published in: Physical Review Letters 122 (2019)
Published by: APS
DOI: 10.1103/PhysRevLett.122.082003
arXiv: 1811.08659
License: CC-BY-4.0



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