Test of $\overline{N}$N potential models: Isospin relations in $\overline{p}$d annihilations at rest and the search for quasinuclear bound states

The CRYSTAL BARREL Collaboration:     A. Abele - et al.

doi:doi:10.1007/s100520000492

2021 Impact factor 4.991

Particles and Fields

Eur. Phys. J. C 17, 583-592
DOI 10.1007/s100520000492

Test of $\overline{{\mbox N}}$ N potential models: Isospin relations in $\overline{{\mbox p}}$ d annihilations at rest and the search for quasinuclear bound states

The CRYSTAL BARREL Collaboration
A. Abele⁸ - J. Adomeit⁷ - C. Amsler¹⁶ - C.A. Baker⁵ - B.M. Barnett³ - C.J. Batty⁵ - M. Benayoun¹³ - S. Bischoff⁸ - P. Blüm⁸ - K. Braune¹² - T. Case¹ - V. Credé³ - K.M. Crowe¹ - T. Degener² - M. Doser⁶ - W. Dünnweber¹² - D. Engelhardt⁸ - M.A. Faessler¹² - P. Giarritta¹⁶ - R.P. Haddock¹⁰ - F.H. Heinsius¹ - M. Heinzelmann¹⁶ - A. Herbstrith⁸ - N.P. Hessey¹² - P. Hidas⁴ - C. Holtzhaußen⁸ - D. Jamnik¹² - H. Kalinowsky³ - P. Kammel¹ - J. Kisiel⁶ - E. Klempt³ - H. Koch² - M. Kunze² - U. Kurilla² - M. Lakata¹ - R. Landua⁶ - H. Matthäy² - C.A. Meyer¹⁴ - F. Meyer-Wildhagen¹² - R. Ouared⁶ - K. Peters² - B. Pick³ - M. Ratajczak² - C. Regenfus¹² - W. Roethel¹² - S. Spanier¹⁶ - H. Stöck² - U. Strohbusch⁷ - M. Suffert¹⁵ - J.S. Suh³ - U. Thoma³ - M. Tischhäuser⁸ - I. Uman¹² - C. Völcker¹² - S. Wallis-Plachner¹² - D. Walther² - U. Wiedner⁶ - K. Wittmack³

¹ University of California, LBNL, Berkeley, CA 94720, USA
² Universität Bochum, 44780 Bochum, Germany
³ Universität Bonn, 53115 Bonn, Germany
⁴ Academy of Science, 1525 Budapest, Hungary
⁵ Rutherford Appleton Laboratory, Chilton, DidcotOX110QX, UK
⁶ CERN, 1211 Geneva 4, Switzerland
⁷ Universität Hamburg, 22761 Hamburg, Germany
⁸ Universität Karlsruhe, 76021 Karlsruhe, Germany
⁹ University of California, Los Angeles, CA 90024, USA
¹⁰ Universität München, 80333 München, Germany
¹¹ LPNHE Paris VI, VII, 75252 Paris, France
¹² Carnegie Mellon University, Pittsburgh, PA 15213, USA
¹³ Centre de Recherches Nucléaires, 67037 Strasbourg, France
¹⁴ Universität Zürich, 8057 Zürich, Switzerland

Received: 28 January 2000 / Published online: 23 October 2000 - © Springer-Verlag 2000

Abstract
We have determined branching ratios for antiproton annihilations at rest on protons or neutrons in liquid deuterium which we compare to frequencies of isospin-related processes in antiproton-proton annihilations. Using the annihilation rates into $\pi^0\pi^0$ and $\pi^-\pi^0$ where the annihilation took place on the proton or neutron, respectively, we discuss the fraction of S-wave and P-wave annihilation in liquid D₂. The frequencies for $\pi^-\omega$ and $\rho^-\pi^0$ , and $\pi^-\eta$ and $\pi^-\eta'$ and the corresponding frequencies for $\overline{{\mbox p}}$ p annihilations are used to determine isoscalar and isovector contributions to the protonium wave function. The isospin decomposition of the annihilating $\overline{{\mbox p}}$ p system in the ³S₁ or ¹S₀ state is consistent with both, pure $\overline{{\mbox p}}$ p initial wave function and with the predictions of $\overline{{\mbox N}}$ N potential models. For the ³P₀ state of the $\overline{{\mbox p}}$ p atom we find consistency with a pure $\overline{{\mbox p}}$ p system at annihilation while $\overline{{\mbox N}}$ N potential models predict large $\overline{{\mbox n}}$ n contributions. We observe $\rho$ - $\omega$ interference in $\overline{{\mbox p}}$ p $\rightarrow \pi^+\pi^-\eta$ and $\pi^+\pi^-\pi^0$ annihilation which we compare to $\rho$ - $\omega$ interference in e⁺e^- annihilation. The interference patterns show striking similarities due to similar phase relations; the interference magnitude depends on the $\omega$ - $\rho$ production ratio. The similarity of the phase in all 3 data sets demonstrates that isovector and isoscalar parts of the protonium ( $\overline{{\mbox p}}$ p atomic) wave function are relatively real, again in conflict with $\overline{{\mbox N}}$ N potential models. The annihilation rate for $\overline{{\mbox p}}$ d $\rightarrow$ K^-K⁰p confirms the dominance of the isovector contribution to $\overline{{\mbox N}}$ N $\rightarrow$ K $\overline{{\mbox K}}$ annihilations. No complications due to initial state interactions are required by the data. Furthermore, we searched for narrow quasinuclear bound states close to the $\overline{{\mbox N}}$ N threshold, also predicted by $\overline{{\mbox N}}$ N potential models, but with negative outcome. We conclude that $\overline{{\mbox N}}$ N potential models are not suited to provide insight into the dynamics of the annihilation process.