Measurements of the anti-p d Annihilation at Rest

The measurement of different reactions of anti-p d 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) x 10^-3 and (113 ± 30) x 10^-3, respectively. These values are about 30 times greater than the theoretical prediction. For the first time the excitation of the Δ-resonance was observed among the final-state products of anti-p d 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(anti-p d → π- ϕ p) = (6.62 ± 0.49) x 10^-4, for P < 200 MeV/c; BR(anti-p d → π- ϕ p) = (0.95 ± 0.22) x 10^-4, for P > 400 MeV/c; BR(anti-p d → π- ω p) = (49.7 ± 8.9) x 10^-4, for P < 200 MeV/c; BR(anti-p d → π- ω p) = (8.38 ± 1.09) x 10^-4 for P > 400 MeV/c; BR(anti-p d → 2 π- π+ p) = (150 ± 6) x 10^-4 for P < 200 MeV/c; BR(anti-p d → 2 π- π+ p) = (16.6 ± 0.9) x 10^-4, for P > 400 MeV/c; BR(anti-p d → 3π- 2π+ p) = (326 ± 12) x 10^-4, for P < 200 MeV/c; BR(anti-p d → 3π- 2π+ p) = (44 ± 7) x 10^-4, for P > 400 MeV/c; BR(anti-p d → Λ K+ π-) = (0.96 ± 0.19) x 10^-4, for P > 400 MeV/c; BR(anti-p d → Λ K+ π- π0) = (3.5 ± 0.8) x 10^-4, for P > 400 MeV/c; BR(anti-p p → 2π- 2π+) = (540 ± 20) x 10^-4; BR(anti-p p → 3π- 3π+) = (251 ± 21) x 10^-4.