114 research outputs found
The He-4(pi+,pi-) reaction at low energies
No full textUsing the CHAOS spectrometer at TRIUMF the total cross sections and outgoing pion momentum distributions for the 4He(π+,π−) reaction were measured for π+ kinetic energies from 70 to 130 MeV. At energies around 100 MeV the total cross sections show an excess by a factor 3 over conventional model calculations which could be ascribed to a contribution from a hypothetical d′ dibaryon
pi pi --> pi pi cross-sections near threshold
No full textAn analysis of new data for the reaction p6p!p6p1n at incident energies between 223 and 284 MeV is
presented. p1p2 cross sections are obtained via Goebel-Chew-Low techniques by extrapolation to the pion
pole using the pseudoperipheral approximation. A consistency check between the present experimental results
and previous experiments at higher energies is made using Roy equations. The isospin 0, S-wave pp scattering
length was obtained using a variety of methods. The result obtained from a threshold expansion is a0 0
50.20460.014 ~statistical! 60.008 ~systematic! in inverse pion mass units. It is shown that there are significant
differences between the reaction mechanisms for the (p2p1) and (p1p1) channels
Pion absorption in C-12
No full textWe 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
Exclusive measurements of pi+- p --> pi+ pi+- n near threshold
No full textThe pion induced pion production reactions π±p⃗π+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
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