Absolute differential cross-sections for elastic. pi. sup + p scattering at 30 le T sub. pi. le 140 MeV

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:7235179

Brack, J T

Differential cross sections for elastic {pi}{sup {plus minus}}p scattering have been measured at TRIUMF for 10 incident pion energies in three separate experiments at 66.8 {le} T{sub {pi}} {le} 138.8 MeV, T{sub {pi}} = 66.8 MeV ({pi}{sup +}p only), and 30 {le} T{sub {pi}} {le} 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 {pi}{sup {plus minus}}p results from these three measurements are in good agreement with previous measurements, as are the {pi}{sup {minus}}p results at all energies. However, while the {pi}{sub {plus minus}}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 {pi}{sup {plus minus}}p scattering measurements in that they are incompatible with the currently accepted value of the {pi}N {sigma} term as calculated from the QCD Lagrangian in the chiral limit.

• Research Organization: Colorado Univ., Boulder, CO (United States)
• OSTI ID: 7235179
• Country of Publication: United States
• Language: English

Related Subjects

662340* -- Hadron Interactions-- (1992-)
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ACCELERATORS
BARYONS
COINCIDENCE METHODS
COMPARATIVE EVALUATIONS
COUNTING TECHNIQUES
CROSS SECTIONS
CYCLIC ACCELERATORS
CYCLOTRONS
DATA
DIFFERENTIAL CROSS SECTIONS
DIMENSIONS
ELASTIC SCATTERING
ELEMENTARY PARTICLES
ENERGY RANGE
EVALUATION
FERMIONS
HADRON-HADRON INTERACTIONS
HADRONS
INFORMATION
INTERACTIONS
ISOCHRONOUS CYCLOTRONS
LENGTH
MATHEMATICS
MEASURING INSTRUMENTS
MESON-BARYON INTERACTIONS
MESON-NUCLEON INTERACTIONS
MEV RANGE
MEV RANGE 100-1000
NUCLEONS
PARTICLE INTERACTIONS
PION MINUS-PROTON INTERACTIONS
PION PLUS-PROTON INTERACTIONS
PION-NUCLEON INTERACTIONS
PION-PROTON INTERACTIONS
PROTONS
RADIATION DETECTORS
RECOILS
SCATTERING
SCATTERING LENGTHS
SCINTILLATION COUNTERS
STATISTICS
TARGETS
TIME-OF-FLIGHT METHOD
TRIUMF CYCLOTRON