Berlin 2005 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 31: Elektromagnetische und Hadronische Proben
HK 31.3: Talk
Tuesday, March 8, 2005, 17:00–17:15, TU MA004
Two-Pion Production and the Question of Isospin Breaking and/or Bose-Einstein correlations∗ — •T. Skorodko, M. Bashkanov, H. Clement, E. Doroshkevich, M. Kaskulov, O. Khakimova, F. Kren, R. Meier, and G. J. Wagner — Physikalisches Institut, Universität Tübingen
The ππ production in pp collisions has been measured at CELSIUS in
the
energy range Tp = 775 − 1360 MeV exclusively using the WASA 4π
detector
with hydrogen pellet target.
At energies close to threshold the data on the ppπ+ π− channel can
be
well described by either the Roper resonance concept or a dynamic formation
of
the σ meson. At higher energy the formation of the ΔΔ
system
becomes increasingly dominant. In particular the data are consistent with
the
special configuration (ΔΔ)0+.
The ppπ0 π0 channel basically shows a very similar behavior as
expected
from isospin invariance. However, Mπ0 π0 shows systematically
an
enhancement at small invariant masses. The deduced correlation function
resembles very much that for Bose-Einstein correlations (BEC).
two
Alternatively the observed
enhancements could be indicative of a (dynamic) isospin breaking possibly
due
to ππ rescattering in the σ channel.
In order to discriminate both scenarios we have investigated also
pd → 3Heππ.
In contrast to Mπ+π−, Mπ0π0 exhibits again a strong
enhancement at low masses,
this time even substantially larger than 2, the BEC limit, favoring thus an
isospin breaking scenario for the observed effects.
∗ supported by BMBF (06 TU 201), DFG
(Europ. Graduiertenkolleg), and Landesforschungsschwerpunkt (Quasiteilchen)