2019 Impact factor 4.389
Particles and Fields
Eur. Phys. J. C 10, 249-263
DOI 10.1007/s100529900113

Comprehensive evidence for a narrow ${\mathrm {p}}\overline{\mathrm {p}}$ state
of mass 2.02GeV/c2

A. Ferrer1 - A.A. Grigoryan2 - V.F. Perepelitsa3,4 - P. Sonderegger4

1 Departamento de Física Atómica Molecular y Nuclear, University of Valencia and IFIC, Centro Mixto University of Valencia - CSIC, Avda. Dr. Moliner 50, E-46100 Burjassot, Valencia, Spain
2 Theoretical Department, YerPhI, Yerevan Physics Institute, Br. Alikhanian st. 2, 375036 Yerevan, Armenia
3 ITEP, B. Cheremushkinskaya 25, 117259 Moscow, Russia
4 CERN, CH-1211 Geneva 23, Switzerland

Received: 26 May 1998 / Revised version: 26 March 1999 / Published version: 3 August 1999

We review earlier results, and add new evidence, on the existence of a narrow ${\mathrm {p}}\overline{\mathrm {p}}$ state at a mass of 2.02GeV/c2, which is seen in six different final states, produced via baryon exchange in $\pi^+{\mathrm {p}}$ $(\pi^-{\mathrm {p}})$ interactions at 20 (12)GeV/c. The data come from a new analysis of the WA56 experiment done at the CERN Omega spectrometer. The 2020 peak is produced near mid-rapidity, in a kinematic region not explored before in baryon exchange processes. Agreement is found with an earlier observation of this state, and its absence in a series of unsuccessful searches is explained. Very low upper limits on mesonic decays of this state favor its interpretation as a baryonium candidate.

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