Differential cross sections for the elastic scattering of K + mesons on protons have been measured at 12 lab momenta between 130 and 755 MeV/ c using a hydrogen filled bubble chamber. The results are consistent with a repulsive S-wave nuclear force. A phase-shift analysis yielded the following values of the low-energy parameters: a S 1 2 =(0.309±0.002) fm , r S 1 2 =(0.032±0.02) fm a P 1 2 =(0.021±0.002) fm , a P 3 2 =(0.013±0.001) fm 3

Interactions of 683-MeV/c negative pions with protons were investigated using the BNL 14-in. hydrogen bubble chamber in a 17-kG field. Two thousand elastic scatterings were analyzed, yielding a cross section of 18.9±1.0 mb. No evidence for powers of cosθ higher than the second was observed in the elastic angular distribution. The angular distribution obtained was dσdω=(0.384±0.026)+(1.70±0.06)cosθ+(3.36±0.11)cos2θ mb/sr. The single-pion production reactions π−+p→π−+π0+p and π−+p→π−+π++n were studied in detail. A total of 441 π0 productions and 833 π+ productions were analyzed giving cross sections of 3.99±0.50 and 7.50±0.80 mb, respectively. The differential distributions for these inelastic processes are presented and compared with the predictions of the model of Olsson and Yodh. The distribution of events on the Dalitz plots for π0 production is accounted for by the model. However, for the π+ reaction, the model (so far developed) does not describe adequately the distribution of events on the Dalitz plot. In particular, the model fails to account for the enhancement at high (π+π−) effective masses in ππ mass distribution. The center-of-mass angular distributions for π0 and π+ production reactions are presented and compared with the model.

Report on the investigation of interactions in π−p collisions at a pion momentum of 1.59 GeV/c, by means of the 50 cm Saclay liquid hydrogen bubble chamber, operating in a magnetic field of 17.5 kG. The results obtained concern essentially the elastic scattering and the inelastic scattering accompanied by the production of either a single pion in π−p→ pπ−π0 and nπ−π+ interactions, or by more than one pion in four-prong events. The observed angular distribution for the elastic scattering in the diffraction region, can be approximated by an exponential law. From the extrapolated value, thus obtained for the forward scattering, one gets σel= (9.65±0.30) mb. Effective mass spectra of π−π0 and π−π+ dipions are given in case of one-pion production. Each of them exhibits the corresponding ρ− or ρ0 resonances in the region of ∼ 29μ2 (μ = mass of the charged pion). The ρ peaks are particularly conspicuous for low momentum transfer (Δ2) events. The ρ0 distribution presents a secondary peak at ∼31μ2 due probably to the ω0 → π−π+ process. The branching ratio (ω0→ π+π−)/(ω0→ π+π− 0) is estimated to be ∼ 7%. The results are fairly well interpreted in the frame of the peripheral interaction according to the one-pion exchange (OPE) model, Up to values of Δ2/μ2∼10. In particular, the ratio ρ−/ρ0 is of the order of 0.5, as predicted by this model. Furthermore, the distribution of the Treiman-Yang angle is compatible with an isotropic one inside the ρ. peak. The distribution of\(\sigma _{\pi ^ + \pi ^ - } \), as calculated by the use of the Chew-Low formula assumed to be valid in the physical region of Δ2, gives a maximum which is appreciably lower than the value of\(12\pi \tilde \lambda ^2 = 120 mb\) expected for a resonant elastic ππ scattering in a J=1 state at the peak of the ρ. However, a correcting factor to the Chew-Low formula, introduced by Selleri, gives a fairly good agreement with the expected value. Another distribution, namely the Δ2 distribution, at least for Δ2 < 10 μ2, agrees quite well with the peripheral character of the interaction involving the ρ resonance. π− angular distributions in the rest frame of the ρ exhibit a different behaviour for the ρ− and for the ρ0. Whereas the first one is symmetrical, as was already reported in a previous paper, the latter shows a clear forward π− asymmetry. The main features of the four-prong results are: 1) the occurrence of the 3/2 3/2 (ρπ+) isobar in π−p → pπ+π−π− events and 2) the possible production of the ω0→ π+π−π0 resonance in π−p→ pπ−π+π−π0 events. No ρ’s were observed in four-prong events.

The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and $pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The implementation of a central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements. Thus all pion production channels were recorded with 1-4 overconstraints. The total and differential cross sections obtained are compared to previous data and theoretical calculations. Main emphasis is put on the discussion of the $pp\pi^0$ channel, where we obtain angular distributions different from previous experimental results, however, partly in good agreement with recent phenomenological and theoretical predictions. In particular we observe very large anisotropies for the $\pi^0$ angular distributions in the kinematical region of small relative proton momenta revealing there a dominance of proton spinflip transitions associated with $\pi^0$ $s$- and $d$-partial waves and emphasizing the important role of $\pi^0$ d-waves.

New data on the K−p elastic and charge exchange reactions are presented in the K− momentum range between 1.934 GeV/c and 2.516 GeV/c. A conventional energy-dependent partial-wave analysis covering the widerPK- range from 1.6 GeV/c to 2.516 GeV/c is presented together with a p.w.a. in which the duality ands-helicity conservation ideas are explicitly imposed in the fits. Finally the new Y*’s observed in this experiment are classified inSU3 multiplets.

We have measured the cross section at 180° for K + p and K + n elastic scattering in the momentum range 1.0 to 1.5 GeV/ c . The K + n cross section was measured on deuterium and the K + p on hydrogen and deuterium. We were thus able to measure directly the difference between free nucleon (proton) scattering and bound nucleon (proton) scattering at large angles. This difference was found to be small and within our experimental accuracy the K + p(n) cross section should be equal to the K + p (free) cross section at 180°. We found no evidence for an s -channel resonance Z ∗ in either the K + p or K + n system. A comparison of our data and those of other groups with theoretical predictions is given.

The differential cross section for K+p elastic scattering has been measured at several momenta in the interval 200-600 MeV/c within a hydrogen bubble chamber. The data have been fitted with a partial-wave analysis. We obtain solutions which are dominated over the entire momentum range by s-wave scattering, with constructive interference between the nuclear and Coulomb scattering. The effective-range approximation with only s waves yields a K+p scattering length a=−0.314±0.007 F and an effective range r0=0.36±0.007 F. The measured total inelastic cross section at 588 MeV/c is 11−5+9 μb.

Measurements of elastic proton-proton differential cross sections for angles between 65° and 90° c.m.s. have been made at 8, 9, 10, 11, 14, 15 and 21 GeV/c. The shape of the angular distribution is found to change suddenly between 8 and 11 GeV/c. An interpretation of this discontinuous behaviour in terms of the reactive effects of baryon-antibaryon pair production is proposed.

Differential cross sections for π + p elastic scattering were measured for seven incident energies from 65 to 140 MeV at laboratory scattering angles between 93° and 165°. The results are compared with previous results of Bertin et al. and the phase-shift analysis of Arndt and Roper. Agreement between the phase-shift analysis and the data is good.

Twenty-nine proton-proton differential elastic cross sections for lab momenta p0 from 11 to 31.8 BeV/c, at four-momentum transfers squared, −t, from 2.3 to 24.4 (BeV/c)2, have been measured at the Brookhaven alternating gradient synchrotron. The circulating proton beam impinged upon a thin CH2 internal target. Both scattered protons from p−p elastic events were detected by scintillation-counter telescopes which were placed downstream from deflection magnets set at the appropriate angles to the incident beam. The angular correlation of the protons, their momenta, and the coplanarity of the events were determined by the detection system. The results show that at high momentum transfers the differential cross section, dσdt, depends strongly upon the energy; for −t=10 (BeV/c)2, the value of dσdt at p0=30 BeV/c is smaller by a factor∼1000 than at p0=10 BeV/c. At all energies, dσdt falls rapidly with increasing |t| for scattering angles up to about 65° (c.m.), while in the range from 65 to 90° the cross section falls only by a factor of about 2. The smallest cross section measured was 9×10−37 cm2 sr−1 (c.m.), at p0=31.8 BeV/c and −t=20.4 (BeV/c)2; this is about 3×10−12 of the zero-degree cross section at the same energy.