[en] Differential cross sections for elastic π^±p scattering have been measured at TRIUMF for 10 incident pion energies in three separate experiments at 66.8 ≤ T_π ≤ 138.8 MeV, T_π = 66.8 MeV (π⁺p only), and 30 ≤ T_π ≤ 66.8 MeV, using three independent techniques. Typical statistical accuracies are 1-3% and normalization uncertainties are 1.2-3.0%. Extensive experimental checks were employed to minimize systematic errors. All measurements used solid targets. Thin scintillators and time-of-flight (TOF) techniques were used to count and identify particles incident on the targets and to detect the scattered pions. Recoil protons were detected in coincidence with the scattered pions in two of the three experiments. At incident pion energies of 100 MeV and above, all π^±p results from these three measurements are in good agreement with previous measurements, as are the π^-p results at all energies. However, while the π_±p results of these three experiments are consistent within experimental error at the overlapping energy of 66.8 MeV, they are 10-25% lower than predicted by recent phase shift analyses and the previous data on which they are based, forcing the conclusion that these previous measurements are in error by several times their stated experimental uncertainties. The scattering lengths determined from the present cross sections are three standard deviations higher than those deduced from pionic atom studies, and support previous π^±p scattering measurements in that they are incompatible with the currently accepted value of the πN σ term as calculated from the QCD Lagrangian in the chiral limit

[en] The Canadian high acceptance orbit spectrometer (CHAOS) is a unique magnetic spectrometer system recently commissioned for studies of pion induced reactions at TRIUMF. It is based on a cylindrical dipole magnet producing vertical magnetic fields up to 1.6 T. The scattering target is located in the center of the magnet. Charged particle tracks produced by pion interactions there are identified using four concentric cylindrical wire chambers surrounding the target. Particle identification and track multiplicity are determined by cylindrical layers of scintillation counters and lead glass Cerenkov counters, which also provide a first level trigger. A sophisticated second level trigger system permits pion fluxes in excess of 5 MHz to be employed. The detector subtends 360^o in the horizontal plane, and ±7^o out of this plane for a solid angle coverage approximately 10% of 4π sr. The momentum resolution delivered by the detector system is 1% (σ). (author). 16 refs., 12 figs

[en] A two-dimensional readout system for streamer tube chambers using a passive chip delay line on the anode wires and cathode strips is described. The prototype system with 96 wires per delay line shows good timing resolution and wire efficiencies independent of the position on the delay line. (author)

[en] Short note

[en] Short note

[en] Total cross sections for the H(π⁺,π⁺π⁺)n reaction have been measured at pion kinetic energies of 180, 184, 190 and 200 MeV. The threshold value for the matrix element; a(π⁺π⁺), as well as the s-wave, isospin 2, ππ scattering length, a₂⁰, were determined. The results were found to be in agreement with chiral perturbation theory and inconsistent with the model of dominance by quark loop anomalies (QLAD). (author)

[en] Measurements of π/sup +- /p elastic differential cross sections have been made at seven incident pion energies from 66.8 to 138.8 MeV. These measurements have statistical accuracy of 1.5--3.3Xfor π⁺ and 2.7--19.0Xfor π^-. The absolute normalization uncertainties are 1.2--2.5Xfor π⁺ and 1.2--3.2Xfor π^-. Extensive tests were made to ensure that systematic errors were properly evaluated

[en] Design considerations for a pion spectrometer being built at TRIUMF led to the development of a thin, low mass, single plane cylindrical drift chamber with a simple cell structure consisting of alternating anode and cathode wires. To date no solution to the left-right ambiguity in chambers of this type has been found which works in high magnetic field environments and for arbitrary incident track angles. We hypothesized that the left-right ambiguity could be resolved in a chamber of this type by comparing the induced charge on cathode strips which are parallel to the sense wire and located in diagonally opposed corners of the cell. Measurements with prototype chambers in magnetic fields up to 1.6 T show that the left-right ambiguity is indeed resolved well for tracks with incident angles between -45deg to +45deg. The measured intrinsic chamber resolution for tracks at normal incidence at B=1 T is 150 μm (σ). (orig.)

[en] Absolute π±p differential cross sections have been measured at incident pion energies of 30.0, 45.0, and 66.8 MeV, using active targets of scintillator plastic (CH_1.1) to detect recoil protons in coincidence with scattered pions. Statistical uncertainties are typically ±3%; systematic uncertainties are ±2%. The results are consistent with two earlier measurements by this group employing different experimental techniques at 67 MeV and higher incident pion energies. The π^-p cross sections are in good agreement with currently accepted phase-shift analyses, but the corresponding π⁺p predictions are typically 15% higher at large angles than the π⁺p data reported here

[en] Differential cross sections for /sup 13/C(π/sup +- /,π/sup +- /)/sup 13/C/sup */ were measured at an incident pion energy of 65 MeV. Data were gathered for several states up to 11.8 MeV in excitation energy. The experimental results are compared to distorted wave impulse approximation calculations and to other pion scattering data from the same nucleus at higher beam energies. The striking enhancement of π^- over π⁺ scattering to the 9.5 MeV (9/2⁺ state observed in previous studies at resonance energies is found to persist at 65 MeV