Measurement and isobar-model analysis of the doubly differential cross section for the. pi. /sup +/ produced in. pi. /sup -/p. -->. pi. /sup +/. pi. /sup -/n

Technical Report · Sun Nov 01 04:00:00 EST 1981

DOI:https://doi.org/10.2172/5700334· OSTI ID:5700334

Manley, D M

The doubly differential cross section d/sup 2/sigma/d..cap omega..dT for ..pi../sup +/ mesons produced in the reaction ..pi../sup -/p ..-->.. ..pi../sup +/..pi../sup -/n was measured at 203, 230, 256, and 358 MeV with a single-arm magnetic spectrometer. A set of five previous measurements at 254, 280, 292, 331, and 356 MeV was reanalyzed with the new measurements. Integrated cross sections were calculated for the combined data set with unprecedented accuracy for this energy range. The chiral-symmetry-breaking parameter was determined to be epsilon = -0.03 +- 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 epsilon is consistent with zero as required by the Weinberg Lagrangian. Measurements at the three highest energies were compared with the results of an isobar-model analysis of bubble-chamber events by an LBL-SLAC 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(epsilonN) amplitude, as well as the overall normalization, which could be due to the limited number of bubble-chamber events available for the LBL-SLAC analysis at this energy. A partial-wave 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.

• Research Organization: Los Alamos National Lab., NM (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5700334
• Report Number(s): LA-9101-T; ON: DE82007042
• Country of Publication: United States
• Language: English

Related Subjects

645104* -- High Energy Physics-- Particle Interactions & Properties-Experimental-- Strong Meson-Induced Interactions-- (-1987)
645206 -- High Energy Physics-- Particle Interactions & Properties-Theoretical-- Strong Interactions
Baryon No. = 1-- (-1987)
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BARYONS
BOSONS
CHIRAL SYMMETRY
CROSS SECTIONS
DATA
DIFFERENTIAL CROSS SECTIONS
ELEMENTARY PARTICLES
ENERGY RANGE
EXPERIMENTAL DATA
FERMIONS
HADRON-HADRON INTERACTIONS
HADRONS
INFORMATION
INTERACTIONS
ISOBAR MODEL
MAGNETIC SPECTROMETERS
MATHEMATICAL MODELS
MATRIX ELEMENTS
MEASURING INSTRUMENTS
MESON-BARYON INTERACTIONS
MESON-NUCLEON INTERACTIONS
MESONS
MEV RANGE
MEV RANGE 100-1000
NEUTRONS
NUCLEONS
NUMERICAL DATA
PARTICLE INTERACTIONS
PARTICLE MODELS
PION MINUS-PROTON INTERACTIONS
PION-NUCLEON INTERACTIONS
PION-PROTON INTERACTIONS
PIONS
PIONS MINUS
PIONS PLUS
PSEUDOSCALAR MESONS
SPECTROMETERS
SYMMETRY
SYMMETRY BREAKING
THEORETICAL DATA