APS : First measurement of a long-lived $\pi^+ \pi^-$ atom lifetime

Adeva, B.; Kruglova, L.; Mariñas, C.; Chliapnikov, P.V.; Romero Vidal, A.; Kobayashi, M.; Plo, M.; Penzo, A.; Hons, Z.; Drijard, D.; Trojek, T.; Gorin, A.; Brekhovskikh, V.; Trusov, S.; Iwashita, Y.; Horikawa, S.; Aogaki, S.; Schacher, J.; Sidorov, A.; Kluson, J.; Gritsay, K.; Ryazantsev, A.; Yoshimura, Y.; Pentia, M.; Okada, K.; Gugiu, M.; Rykalin, V.; Rappazzo, G.F.; Cechak, T.; Takeutchi, F.; Dumitriu, D.; Nemenov, L.; Vrba, T.; Smolik, J.; Nikitin, M.; Hansroul, M.; Lanaro, A.; Ovsiannikov, V.; Yazkov, V.; Lamberto, A.; Gorchakov, O.; Fluerasu, D.; Benelli, A.; Anania, A.; Lednicky, R.; Guaraldo, C.; Kulish, E.; Dudarev, A.; Karpukhin, V.; Saborido, J.; Afanasyev, L.; Doskarova, P.; Zrelov, P.; Martincik, J.; Olchevskii, V.; Chiba, M.; Kulikov, A.; Prusa, P.; Kruglov, V.

doi:10.1103/PhysRevLett.122.082003

Article
Report number	arXiv:1811.08659 ; CERN-EP-2018-281 ; DIRAC-PUB-2019-01
Title	First measurement of a long-lived $\pi^+ \pi^-$ atom lifetime
Author(s)	Adeva, B. (Santiago de Compostela U.) ; Afanasyev, L. (Dubna, JINR) ; Anania, A. (INFN, Trieste ; Messina U.) ; Aogaki, S. (Bucharest, IFIN-HH) ; Benelli, A. (U. Zurich (main)) ; Brekhovskikh, V. (Serpukhov, IHEP) ; Cechak, T. (Prague, Tech. U.) ; Chiba, M. (Tokyo Metropolitan U.) ; Chliapnikov, P.V. (Serpukhov, IHEP) ; Doskarova, P. (Prague, Tech. U.) ; Drijard, D. (CERN) ; Dudarev, A. (Dubna, JINR) ; Dumitriu, D. (Bucharest, IFIN-HH) ; Fluerasu, D. (Bucharest, IFIN-HH) ; Gorin, A. (Serpukhov, IHEP) ; Gorchakov, O. (Dubna, JINR) ; Gritsay, K. (Dubna, JINR) ; Guaraldo, C. (Frascati) ; Gugiu, M. (Bucharest, IFIN-HH) ; Hansroul, M. (CERN) ; Hons, Z. (Rez, Nucl. Phys. Inst.) ; Horikawa, S. (U. Zurich (main)) ; Iwashita, Y. (Kyoto U.) ; Karpukhin, V. (Dubna, JINR) ; Kluson, J. (Prague, Tech. U.) ; Kobayashi, M. (KEK, Tsukuba) ; Kruglov, V. (Dubna, JINR) ; Kruglova, L. (Dubna, JINR) ; Kulikov, A. (Dubna, JINR) ; Kulish, E. (Dubna, JINR) ; Lamberto, A. (INFN, Trieste ; Messina U.) ; Lanaro, A. (CERN ; Wisconsin U., Madison) ; Lednicky, R. (Prague, Inst. Phys.) ; Mariñas, C. (Santiago de Compostela U.) ; Martincik, J. (Prague, Tech. U.) ; Nemenov, L. (Dubna, JINR ; CERN) ; Nikitin, M. (Dubna, JINR) ; Okada, K. (Kyoto Sangyo U.) ; Olchevskii, V. (Dubna, JINR) ; Ovsiannikov, V. (Voronezh State U.) ; Pentia, M. (Bucharest, IFIN-HH) ; Penzo, A. (INFN, Trieste) ; Plo, M. (Santiago de Compostela U.) ; Prusa, P. (Prague, Tech. U.) ; Rappazzo, G.F. (INFN, Trieste ; Messina U.) ; Romero Vidal, A. (Santiago de Compostela U.) ; Ryazantsev, A. (Serpukhov, IHEP) ; Rykalin, V. (Serpukhov, IHEP) ; Saborido, J. (Santiago de Compostela U.) ; Schacher, J. (Bern U., LHEP ; U. Bern, AEC) ; Sidorov, A. (Serpukhov, IHEP) ; Smolik, J. (Prague, Tech. U.) ; Takeutchi, F. (Kyoto Sangyo U.) ; Trojek, T. (Prague, Tech. U.) ; Trusov, S. (SINP, Moscow) ; Vrba, T. (Prague, Tech. U.) ; Yazkov, V. (SINP, Moscow) ; Yoshimura, Y. (KEK, Tsukuba) ; Zrelov, P. (Dubna, JINR)
Publication	2019-03-01
Imprint	09 Oct 2018
Number of pages	7
Note	7 pages, 8 figures
In:	Phys. Rev. Lett. 122 (2019) 082003
DOI	10.1103/PhysRevLett.122.082003
Subject category	Particle Physics - Experiment ; nucl-ex ; Nuclear Physics - Experiment ; hep-ex
Accelerator/Facility, Experiment	CERN PS ; DIRAC PS212
Free keywords	QCD ; lifetime ; experimental results ; double-exotic atoms
Abstract	The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogen-like $\pi^+\pi^-$ atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96 mm and got broken up in the 2.1 \textmu{}m thick platinum foil. Analysing the observed number of atomic pairs, $n_A^L= \left.436^{+157}_{-61}\right\|_\mathrm{tot}$, the lifetime of the 2$p$ state is found to be ${\tau_{2p}=(\left.0.45^{+1.08}_{-0.30}\right\|_\mathrm{tot}) \cdot10^{-11}}$s, not contradicting the corresponding QED $2p$ state lifetime ${\tau_{2p}^\mathrm{QED}=1.17 \cdot 10^{-11}}$s. This lifetime value is three orders of magnitude larger than our previously measured value of the $\pi^+\pi^-$ atom ground state lifetime $\tau=(\left.3.15^{+0.28}_{-0.26}\right\|_\mathrm{tot})\cdot 10^{-15}$s. Further studies of long-lived $\pi^+\pi^-$ atoms will allow to measure energy differences between $p$ and $s$ atomic states and so to determine $\pi\pi$ scattering lengths with the aim to check QCD predictions.
Copyright/License	Preprint: © 2018-2024 CERN (License: arXiv nonexclusive-distrib. 1.0) Publication: (License: CC-BY-4.0), sponsored by SCOAP³

$Probability $P_\mathrm{br}^{\mathrm{tot}}(\mathrm{Pt})$ calculated as a function of $\alpha$ (see text). The horizontal lines correspond to the measured value $P_\mathrm{br}^{\mathrm{tot}}(\mathrm{Pt}) = \left. 0.0257^{+0.0097}_{-0.0036}\right|_\mathrm{tot}$ (\ref{eq:pBr}) together with the total errors. The value $\alpha=1$, which corresponds to pure QED calculations, is within the error band of the measurement.$ $Method to investigate long-lived $A_{2\pi}^L$ by means of a breakup foil (side view). $N_A$ is the number of the totally produced $A_{2\pi}$ and $N_A^L$ the number of excited $A_{2\pi}^L$ with $l>0$.$ $Lab momentum spectrum of $A_{2\pi}$ produced in Be, as used in the simulation.$ Show more plots

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