2020 Impact factor 4.590
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

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.

Copyright Società Italiana di Fisica, Springer-Verlag 2000