Measurement of the anti-p d annihilation at rest

The measurement of different reactions of ~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 = ~b~r/to~r in two regions of proton momenta, P < 200 MeV/c and P > 400 MeV/c: R(&~r-/toTr-) = (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 A-resonance was observed among the final-state products of ~d annihilation. The existence of a broad enhancement in the 4~r 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 to, p and f2(1270) did not change with the proton momentum. The following branching ratios were measured: BR(~d ~ 7r-~bp) = (6.62 + 0.49) × 10 -4, for P < 200 MeV/c; BR(pd --* zr-~bp) = (0.95 + 0.22) × 10 -4, for P > 400 MeV/c; BR(~d ~ r-top) = (49.7 + 8.9) x 10 -4, for P < 200 MeV/c; BR(~d ~ ~--top) = (8.38 + 1.09) × 10 -4, for P > 400 MeV/c; BR(~d --+ 2~--zr+p) = (150 + 6) × 10 -4, for P < 200 MeV/c; BR(~d --* 2~--zr+p) = (16.6 + 0.9) × 10 -4, for P > 400 MeV/c; BR(~d --* 37r-2~r+p) = (326 + 12) × 10 -4, for P < 200 MeV/c; BR(~d --+ 37r-2~-+p) --- (44 _ 7) × 10 -4, for P > 400 MeV/c; BR(~d ---, AK+~ "-) = (0.96 + 0.19) × 10 -4, for P > 400 MeV/c; BR(pd ~ AK+~--~ "°) ---- (3.5 + 0.8) × 10 -4, for P > 400 MeV/c; BR(~p ~ 2~r-27r +) = (540 + 20) X 10-4; BR(~p --* 3~-3~ "+) = (251 + 21) x 10 -4.