Absolute π±p elastic scattering differential cross sections have been measured at five incident pion energies between 87 and 139 MeV. An active target of scintillator material (CH1.1) was used to detect recoil protons in coincidence with scattered pions. Pions were detected at forward angles between 27 and 98°c.m. where the low-energy recoil protons stop in the target. The cross sections, typically 5–10% lower than phase shift predictions for π+p and 10–20% lower for the π−p cross sections, are consistent with earlier measurements by this group.
No description provided.
No description provided.
No description provided.
The pion induced pion production reactions π±p→π+π±n were studied at projectile incident energies of 223, 243, 264, 284, and 305 MeV, using a cryogenic liquid hydrogen target. The Canadian High Acceptance Orbit Spectrometer was used to detect the two outgoing pions in coincidence. The experimental results are presented in the form of single differential cross sections. Total cross sections obtained by integrating the differential quantities are also reported. In addition, the invariant mass distributions from the (π+π−) channel were fitted to determine the parameters for an extended model based on that of Oset and Vicente-Vacas. We find the model parameters obtained from fitting the (π+π−) data do not describe the invariant mass distributions in the (π+π+) channel.
Total cross sections were obtained by integrating the differential cross section over all three variables: M(pi,pi)**2, t, Cos(Theta(pi)).
Total cross sections were obtained by integrating the differential cross section over all three variables: M(pi,pi)**2, t, Cos(Theta(pi)).
We have studied the two reactions 12C(π+,pp) and 12C(π+,ppp) in one experiment, using the CHAOS spectrometer at TRIUMF, at incident pion energies of 200, 240, and 280 MeV. In both cases, we are able to distinguish between reaction mechanisms involving only the detected protons, and those in which additional nucleons must have participated, on the basis of missing momentum. In the case of 12C(π+,ppp), we identify events due to the two step process of π+p quasielastic scattering followed by two-nucleon absorption. Estimates are made for the total cross sections for the various absorption mechanisms.
The total observed cross sections are not corrected for limited experimental acceptance. No errors are given. The comments (C=MNKO), (C=2NP), and (C=GT2NP) stand for multy nucleon knockout, 2 nucleons participated, and more than 2 nucleons participated, respectively.
Analyzing powers for πp elastic scattering were measured using the CHAOS spectrometer at energies spanning the Δ(1232) resonance. This work presents π+ data at the pion kinetic energies 117, 130, 139, 155, 169, 180, 193, 218, 241, and 267 MeV and π− data at 87, 117, 193, and 241 MeV, covering an angular range of 50°<~θc.m.<~180° at the higher energies and 90°<~θc.m.<~180° at the lower energies. Unique features of the spectrometer acceptance were employed to reduce systematic errors. Single-energy phase shift analyses indicate the resulting S11 and S31 phases favor the results of the SM95 phase shift analysis over that of the older KH80 analysis.
Measurement of the PI+ analysing power at 117 MeV.. The data were collected in the conventional mode and may be independently floated within the systematic error.
Measurement of the PI+ analysing power at 139 MeV.. The data were collected in the conventional mode and may be independently floated within the systematic error.
Measurement of the PI- analysing power at 87 MeV.. The data were collected in the conventional mode and may be independently floated within the systematic error.
Absolute π±d differential cross sections and charge asymmetries have been measured at incident pion energies of 30 and 50 MeV, using an active target of scintillator plastic to detect recoil deuterons in coincidence with scattered pions. In addition, a small set of data at 65 MeV was collected for comparision with the results of an earlier experiment performed by this group. Measurements at 50 MeV from the earlier experiment are compared with the results of the present experiment.
No description provided.
No description provided.
No description provided.
New experimental results on the π + d → π + π − pp and π + d → π + π + nn reactions at T π 1 = 283 MeV are presented. In-plane coincidence data were taken with the CHAOS spectrometer using pions from the M11 channel at TRIUMF. Because of the quasi-free nature of the pion-production reaction, the present study is equivalent to studying the elementary π + N → π + π ± N reactions on protons and neutrons simultaneously. These exclusive measurements provide a set of many-fold differential cross sections which are an ideal testing ground for microscopic models describing the πN → ππN reaction. The interpretation of the data relies on a model which is based on effective chiral Lagrangians to describe the piece of the reaction that includes only π's and N 's, and on effective Lagrangians to account for intermediate Δ's and N ∗ ' s . The measured many-fold differential cross sections are used to constrain some parameters of the model (ξ, f Δ , C, g N ∗ Δπ and g N ∗ Nπ ). Finally, the π + π ± invariant mass distributions display no evidence of strongly interacting pion pairs in either the I = J = 0 or the I = 2 J = 0 channels.
No description provided.
No description provided.
Analyzing powers for π−p elastic scattering have been measured at TRIUMF using the CHAOS spectrometer and a spin-polarized target. These data were collected at a bombarding energy of Tπ=279MeV and cover an angular range of 53<~θc.m.π<~180°. There is good agreement between these data and the latest partial wave analysis from the VPI/GWU group.
Analysing power measurement.
Integral cross sections for the scattering of pions by protons into angles greater than 30° (lab) have been measured at a wide range of energies spanning the delta resonance using liquid hydrogen targets. Cross sections were measured for π+p scattering at 40 energies from 39.8 to 283.9 MeV and for π−p at 15 energies from 80.0 to 283.9 MeV. Comparisons with phase shift predictions from the Karlsruhe group show good agreement on resonance but significant deviations below 100 MeV.
The uncertainties shown include statistical and systematic contributions.
The uncertainties shown include statistical and systematic contributions.
Analyzing powers for πp elastic scattering at bombarding energies below the Δ(1232) resonance were measured at TRIUMF using the CHAOS spectrometer and a polarized spin target. This work presents π− data at six incident energies of 57, 67, 87, 98, 117, and 139 MeV, and a single π+ data set at 139 MeV. The higher energy measurements cover an angular range of 72°<~θc.m.<~180° while the lower energies were limited to 101°<~θc.m.<~180°. There is a high degree of consistency between this work and the predictions of the VPI/GWU group’s SM95 partial wave analysis.
Analysing power measurements for a 139 GeV PI+ beam (standard track).
Analysing power measurements for a 139 GeV PI- beam (standard track).
Analysing power measurements for a 117 GeV PI- beam (standard track).
Differential cross sections for pi- p and pi+ p elastic scattering were measured at five energies between 19.9 and 43.3 MeV. The use of the CHAOS magnetic spectrometer at TRIUMF, supplemented by a range telescope for muon background suppression, provided simultaneous coverage of a large part of the full angular range, thus allowing very precise relative cross section measurements. The absolute normalisation was determined with a typical accuracy of 5 %. This was verified in a simultaneous measurement of muon proton elastic scattering. The measured cross sections show some deviations from phase shift analysis predictions, in particular at large angles and low energies. From the new data we determine the real part of the isospin forward scattering amplitude.
Elastic PI- P cross section for incident kinetic energy 43.3 MeV for the rotated target data. Errors shown are statistical only.
Elastic PI- P cross section for incident kinetic energy 43.3 MeV. Errors shown are statistical only.
Elastic PI- P cross section for incident kinetic energy 37.1 MeV. Errors shown are statistical only.
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