Münster 2002 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 46: Electromagnetic and Hadronic Probes VI
HK 46.5: Vortrag
Donnerstag, 14. März 2002, 17:30–17:45, D
Total cross section of the π− p → π0 n charge exchange reaction — •J. Breitschopf1, H. Clement1, M. Cröni1, H. Denz1, E. Friedman2, P. Jesinger1, R. Meier1, and G. J. Wagner1 — 1Physikalisches Institut, Universität Tübingen — 2Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
The mass difference of up- and down-quarks is the origin
of isospin violation in the strong interaction. Isospin
breaking can in principle be tested in a number of ways
in the pion-nucleon system.
Currently experimentally accessible is the comparison
of elastic scattering of positively and negatively charged
pions from protons with the charge exchange reaction
π− p → π0 n (SCX). Analyses of this
system, based on the existing scattering data base,
found unexpectedly large isospin breaking in s-waves
for pion energies below 100 MeV. These analyses probably are
not suffficiently restricted by the low amount of
SCX data. Therefore, further measurements of SCX cross sections
and analyzing powers are needed to test this result.
A measurement of the SCX total cross section in the energy
region from 30 to 250 MeV has been started at PSI. The experiment
employs a transmission technique using a 4π box detector
consisting of thin plastic scintillators. A first beam
time covered the high energy part from 60 to 250 MeV, a second
beam time in 2002 will take data from 30 to 90 MeV.
The measuring procedure and the status of the experiment
are discussed. This work is supported by BMBF (06Tü987I)
and DFG (Europäisches Graduiertenkolleg Basel-Tübingen).