Annihilations of Antiprotons in Hydrogen at Rest Into Two Mesons

Abstract

VOLUME 15, NUMBER 12 PHYSICAL REVIEW LETTERS 20 SEPTEMBER 1965 1.7 1.9 2.1 2.3 MassU-Tr-p) (BeV) 2.5 2.7FIG. 2. (a) Mass of ir~ir + p. (b) Mass of 7r -TT-i >.cay dominantly into any lower mass resonance. The kinetic energies of the proton, TF + and 7r°, were calculated in the center of mass 7T + 77°/) system. The Dalitz plots of the kinetic energy of the if versus the kinetic energy of the proton and the n° versus 7r + were plotted for the events with a TT + TI 0 P mass between (a) 1.65 and 1.69 BeV, (b) 1.69 and 1.725 BeV (the enhancement region), and (c) 1.725 and 1.765 BeV, for the unlikely possibility that a sudden change would occur when passing through the enhancement region. No difference was observed, as was expected due to the complex-ity of the final state.There is no sudden change in the distribution of momentum transfer to the 7r + Tr°p system when the TT + TT°P mass goes through the enhancement region, either. Thus, the only evidence for a resonance is an enhancement in the mass plot of the TT + 7i°p system. Experiments involving the same reaction at neighboring energies have not found any evidence for this enhancement; however, on the basis of their data on the ir + p total cross section, Devlin, Solomon, and Bertsch 1 have recently suggested the existence of a T = § pionnucleon resonance at 1.65 BeV with a width of 0.2 BeV. Their mass is only slightly lower than ours, but their width is much greater.We present in this Letter a tabulation of the rates for the annihilation of antiprotons at rest in hydrogen into various two-body channels. The tabulation is based on an analysis of 9301 two-pronged and 16 700 four-pronged pionic annihilations, and 6768 kaonic annihilations obtained from an exposure of the Columbia-Brookhaven National Laboratory 30-in. hydrogen bub-ble chamber to a separated low-energy antiproton beam at the Brookhaven AGS. The details of the analyses on which this tabulation is based are presented in a series of articles which will be published in the near future. The results are presented in Table I.The fraction of annihilations from the P wave of the pp system was estimated using arguments 532

Hadronic probes of the polarized intrinsic strangeness of the nucleon

“…The polarized intrinsic-strangeness model provides an alternative explanation of the facts (32)- (34), and demonstrates that this selection rule may have the same origin as the preferential production of vector K * 0K * 0 mesons over K * + K * − . This phenomenon has indeed been observed in bubble-chamber experiments [42,43], where it was found that annihilation into two neutral K * dominates over charged K * formation. For instance, according to [42], Y (pp → K * 0K * 0 ) = (30 ± 7) · 10 −4 , whereas Y (pp → K * +K * − ) = (15 ± 6) · 10 −4 .…”

The antinucleon–nucleon interaction at low energy: Annihilation dynamics

“…The Brookhaven results are documented in Refs. [42][43][44][45][46][47][48][49][50]. At CERN, more aspects of the annihilation process were investigated, leading to a larger number of publications.…”

“…The analysis was therefore repeated with the recent value [215] for AF(K s K s , liq.) = (7.0 ± 3.5) × 10 −6 replacing the one [42,114] used in the earlier analysis. An equally good fit was obtained with χ 2 /N = 8.38/9 and a value of BR(K 0 K 0 , 3 P 2 ) consistent with zero.…”

Meson-baryon dynamics in the nucleon-antinucleon system. II. Annihilation into two mesons

“…Knowing the results from the annihilation in liquid hydrogen, the pure 5-wave contributions [5,6,15,16]l and experimental data (Refs. [9,[29][30][31][32][33][34][35]) for selected annihilation channels. Channel SP~A(BOX) KW Ref.…”