MEASUREMENTS OF THE (P)OVER-BAR-D ANNIHILATION AT REST

摘要

The measurement of different reactions of (p) over bar 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 = phi pi/omega pi in two regions of proton momenta, P < 200 MeV/c and P > 400 MeV/c: R(phi pi(-)/omega pi(-)) = (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 Delta-resonance was observed among the final-state products of (p) over bar d annihilation. The existence of a broad enhancement in the 4 pi invariant mass at m approximate to 1480 MeV, seen in previous experiments, was confirmed. A approximate to 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 omega, rho and f(2)(1270) did not change with the proton momentum. The following branching ratios were measured: BR((p) over bar d --> pi(-)phi p) = (6.62 +/- 0.49) X 10(-4), for P < 200 MeV/c; BR((p) over bar d --> pi-phi p) = (0.95 +/- 0.22) X 10(-4), for P > 400 MeV/c; BR((P) over bar d --> pi(-)omega p) = (49.7 +/- 8.9) X 10(-4), for P < 200 MeV/c; BR((P) over bar d --> 2 pi(-)omega p) = (8.38 +/- 1.09) X 10(-4) for P > 400 MeV/c; BR((p) over bar d --> 2 pi(-)pi(+)p) = (150 +/- 6) X 10(-4) for P < 200 MeV/c; BR((p) over bar d --> 2 pi(-)pi(+)p) = (16.6 +/- 0.9) X 10(-4), for P > 400 MeV/c; BR((p) over bar d --> 3 pi(-)2 pi(+)p) = (326 +/- 12) X 10(-4), for P < 200 MeV/c; BR((p) over bar d --> 3 pi(-)2 pi(+)p) = (44 +/- 7)x 10(-4), for P > 400 MeV/c; BR((p) over bar d --> Lambda K(+)pi(-)) = (0.96 +/- 0.19) x 10(-4), for P > 400 MeV/c; BR((p) over bar d --> Lambda K(+)pi(-)pi(0)) = (3.5 +/- 0.8) X 10(-4), for P > 400 MeV/c; BR((p) over bar p --> 2 pi(-)2 pi(+)) = (540 +/- 20) X 10(-4); BR((p) over bar p --> 3 pi(-)3 pi(+)) = (251 +/- 21) X 10(-4). [References: 62]