Measurements of the overlinepd annihilation at rest
Abstract
The measurement of different reactions of overlinepd annihilation at rest in a gaseous target has been performed using the OBELIX spectrometer at LEAR (CERN). A strong deviation from the OZI-rule prediction was found from the measurement of the ratio R = {φπ}/{ωπ} in two regions of proton momenta, P < 200 MeV/ c and P > 400 MeV/ c: R( {φπ -}/{ωπ -}) = (133 ± 26) × 10 -3 and (113 ± 30) × 10 -3, respectively. These values are about 30 times greater than the theoretical prediction. For the first time the excitation of the †-resonance was observed among the final-state products of overlinepd annihilation. The existence of a broad enhancement in the 4π invariant mass at m ≈ 1480 MeV, seen in previous experiments, was confirmed. A ≈ 100 MeV downward shift of the bump position, when the proton momentum increased up to P > 400 MeV/ c, was also observed, while the positions of ω, ϱ and f 2(1270) did not change with the proton momentum. The following branching ratios were measured: BR( overlinepd → π -φ p) = (6.62 ± 0.49) × 10 -4, for P < 200 MeV/ c; BR( overlinepd → π -φ p) = (0.95 ± 0.22) × 10 -4, for P > 400 MeV/ c; BR( overlinepd → π -ω p) = (49.7 ± 8.9) × 10 -4, for P < 200 MeV/ c; BR( overlinepd → π -ω p) = (8.38 ± 1.09) × 10 -4, for P > 400 MeV/ c; BR( overlinepd → 2π -π +p) = (150 ± 6) × 10 -4, for P < 200 MeV/ c; BR( overlinepd → 2π -π +p) = (16.6 ± 0.9) × 10 -4, for P > 400 MeV/ c; BR( overlinepd → 3π -2π +p) = (326 ± 12) × 10 -4, for P < 200 MeV/ c; BR( overlinepd → 3π -2π +p) = (44 ± 7) × 10 -4, for P > 400 MeV/ c; BR( overlinepd → Λ K+π -) = (0.96 ± 0.19) × 10 -4, for P > 400 MeV/ c; BR( overlinepd → Λ K+π -π 0) = (3.5 ± 0.8) × 10 -4, for P > 400 MeV/ c; BR( overlinepp → 2π -2π +) = (540 ± 20) × 10 -4; BR( overlinepp → 3π -3π +) = (251 ± 21) × 10 -4.
- Publication:
-
Nuclear Physics A
- Pub Date:
- February 1995
- DOI:
- 10.1016/0375-9474(94)00523-P
- Bibcode:
- 1995NuPhA.585..577A