Publication Date:
1994
abstract:
This paper reports new experimental results on the annihilation of antiprotons stopped in a
4He gas target. The measurement was carried out with the Obelii spectrometer installed at the
LEAR machine of CERN. Main results can be summarized as follows. (i) The invariant mass
distribution of 2rr+2& produced at rest is similar to those from hydrogen and deuterium
targets: the peak seen in recent experiments around 1150 MeV/c’ is absent. (ii) 2rr angular
correlations are very close to those found for hydrogen. The nuclear structure does not modify
remarkably the pion production and emission. (iii) gp and pp angular correlations are strongly
peaked close to 180 O, in qualitative agreement with INC model predictions. (iv) The pp
invariant mass distribution reveals events which may be due to q(w) absorption; the estimated
upper limit for probabili~ of q and o absorption is about 3 x 10m3. (v) Events having features
~mpatible with do-nucleon annihiIations with production of heavy mesonic systems are
detected both in the 2rr+ 2~r- and the 27r- T+ channels. The production rate of the 2nC 2?rchannel
is of the order of 5 X 10W3.
Iris type:
1.1 Articolo in rivista
List of contributors:
A., Adamo a; M., Agnello b; F, ; Balestra, G; G., Belli ‘; G_ Bendiscioli, D; A., Bertin ‘; P., Boccawio f; G. C., Bonazzola g; T., Bressani S; M., Bruschi e; M. P., Bussa g; L., Busso g; D., Calve g; M., Capponi e; P., Cerello g; C., CieaM a; S., Costa g; S., De Castro e; F. D’Isep pl A., Donzella ‘; L., Fava g; A., Feliciello; L., Ferrer0 8; A., Filippi g; V. Fiiippi~i., D; D. GaIIi et R., Ga~agnini g; Gastaldi f, I. J.; P. Gia~otti gI A., Grasso g; C. GuaraIdo it F., Iazzi b; Kharzeev d, D. E.; 2, ; A., Lanaro i; E., Lodi Rizzini ‘; M., ~m~ardi f; V., Lucheriui i; A., Maggiora g; S., Marcell~ 8; Marconi e, I. J.; G. V., ~argagliotti j; G., Maron ‘; A., Masoni a; I., Massa ‘; B., Minetti b; Montagna, PAOLO MARIA; M., Morando k; F., Nichitiu i91; D., Panzieri g; P., Pauli j; M., Piccinini e; G., Piragino g; M., Poli m; G. Puddu 81 R. A., Ricci f7k; E., Rossetto O; Rotondi, Alberto; A. M., R~zhdens~ens~ *; A., Saino ‘; P., Salvini; L., Santi ‘; M. G. Sapozhnik~v., T; N., Semprini Cesari e; S, ; Semi, *; R., Spighi ‘; P. P., Temnikov a; S., Tessaro j; F., Tosello g; V. I., Tretyak dvi; G. L., IJsai ‘; L., Vannucci f; S., Vecchi ‘; G., Vedovato f; L., Venturelli ‘; M., Villa e; A., Vitale e; A., Zenoni h; A., Zoccoli e; G., Zosi
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