Measurement and IsobarModel Analysis of the Doubly Differential Cross Section for the Positive pi Produced in Negative PiProton > Negative PiNeutron
Abstract
The doubly differential cross section. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). for (pi)('+) mesons produced in the reaction (pi)(' )p(>)(pi)('+)(pi)(')n was measured at 203, 230, 256, and 358 MeV with a singlearm magnetic spectrometer. A set of five previous measurements at 254, 280, 292, 331, and 356 MeV were reanalyzed with the new measurements. Integrated cross sections were calculated for the combined data set with unprecedented accuracy for this energy range. The chiralsymmetrybreaking parameter was determined to be (xi) = 0.03 (+OR) 0.26 by extrapolating the mean square modulus of the matrix element to threshold and comparing the threshold matrix element with the prediction of soft pion theory. This value of (xi) is consistent with zero as required by the Weinberg Lagrangian. Measurements at the three highest energies were compared with the results of an isobarmodel analysis of bubblechamber events by an LBLSLAC collaboration. After allowing for an overall normalization difference, the measurements at 331 and 358 MeV were in excellent agreement with the results of their analysis. The measurement at 292 MeV required variation of the PS11((epsilon)N) amplitude, as well as the overall normalization, which could be due to the limited number of bubblechamber events available for the LBLSLAC analysis at this energy. A partialwave analysis of the measurements was also carried out with the VPI isobar model. Within this model, the matrix element contains a background term calculated from a phenomenological (pi)N Lagrangian that is consistent with the hypotheses of current algebra and PCAC. The reaction was found to be dominated by the initial P11 wave. Production of the (DELTA) isobar from initial D waves was found to be significant at the two highest energies.
 Publication:

Ph.D. Thesis
 Pub Date:
 1981
 Bibcode:
 1981PhDT.......188M
 Keywords:

 Physics: Elementary Particles and High Energy