No abstract

unpublished). The accuracy of the coding of the amplitudes and the relevant kinematics into the fitting program was checked in a variety of ways. The isobar-model amplitudes were calculated for a set: of standard events and compared with the amplitudes calculated by other programs independently coded at Lawrenco Berkeley Laboratory, Berkeley; SLAC, Stanford; and CEN, Saelay. In addition, Monte Carlo events were used to generate a variety of mass and angular distributions fom: each wave of Table 111, and these were checked to be physically consistent with the quantum numbers. The polarization calculations were checked explicitly by hand for several events.article Data Group, 9ev. Mod. Phys. 43, S l (1971).'O~he following masses were used to calculate the mixing angle: nzN =I515 515, mx=1670 k10, mA =1690*10, mx=1832-t37, and mA=1518 *2 MeV. "R. Barloutaud (private communication).2 2~h e analysis of Ref. 5 uses an expression for this ratio which yields 3.3. We believe that the expression incorrectly normalizes the Breit-Wigner weight used to calculate an average 8(1385) momentum over the Dalitz plot. Tka normalization of this weight should be independent of the incident momentum. Zf this change i s made, their expression yields a result consistent with ours.

pucker, Phys. Rev. Lett. 16, 746 (1966).A number of experimental studies have been made of the momentum dependence of the total cross section for the reaction ir'p -AK° in the region of incident pion momentum extending from threshold up to and beyond that corresponding to the thresholds for H°K° and Z"if + production. 1 " 8 These studies have sought to clarify the mechanism for AK production near threshold, to search for new resonances, and to find evidence for the predicted cusplike behavior of the total cross section in the region of the UK thresholds. A limitation in previously published studies has been imposed by the uncertainty in the incident pion momentum, typically ±2%, which places a lower limit on the characteristic width of detectable structure of ~20 MeV/c. In the present experiment, the width of detectable structure in the momentum dependence of the total cross section for AK production is reduced to ±1 MeV/c by the use of a spark-chamber spectrometer in the incident pion beam. This apparatus, described elsewhere, 9 permits determination of the momentum of individual incident pions with a relative precision better than ±0.1 %, and with an absolute calibration obtained from kinematic event fitting near the A°K° and H°K° thresholds.

No abstract

Diffraction dissociation of both the beam and target particles has been observed in 150-GeV/c .ir--p interactions in the Fermilab 30-in.-bubble-chamber--proportional-wirechambe hybrid spectrometer. The dissociations are observed as recoil systems opposite leading particles, the signals of which are separated from background where appropriate by a variant of the Van Hove sector cut, thus allowing the high-mass portion of the spectrum to be observed. Pion dissociation has a cross section of 1758-t. 105 pb, divided among two-, four., and six-prong events; some p0 production is seen and comes primarily from the n--t2n-.ir + channel. The proton dissociation cross section is 1726, 100 pb, again divided among two-, four-, and six-prong events. The final state contains a neutron more frequently than a proton in the twoand six-prong events, a proton more frequently in the four-prong events. Production of A + + is observed in the p +p.irf T -dissociations. transferring four-momenhim to other particles,