Frankfurt 2014 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 60: Hadronenstruktur und -spektroskopie
HK 60.2: Vortrag
Freitag, 21. März 2014, 14:30–14:45, HZ 3
Investigation of isospin effects in d p→ 3He π+ π− at ANKE* — •Malte Mielke1, Christopher Fritzsch1, Paul Goslawski1, Alfons Khoukaz1, Michael Papenbrock1, Daniel Schröer1, Alexander Täschner1, and Colin Wilkin2 for the ANKE collaboration — 1Westfälische Wilhelms-Universität, Münster,Germany — 2University College London, U.K.
Two-pion production in nuclear collisions has been the subject of intensive research for more than 50 years, ever since the discovery of the so-called ABC-effect in proton-deuteron collisions. The effect appears as an enhancement at low two-pion invariant masses and is found to be dominantly in the ππ isospin Iππ=0 channel. In the d p → 3He π+ π− reaction, interferences of Iππ=0 and Iππ=1 are allowed, which permits studies on possible contributions of the Roper resonance, especially in the isovector part. These cause the 3He π+ and 3He π− invariant-mass distributions to differ in shape and are therefore experimentally accessible.
The high momentum resolution that is needed to quantify these differences can
be achieved with the ANKE spectrometer at the COoler SYnchrotron (COSY),
where data of the reaction d p → 3He π+
π− were recorded in an excess energy range of 265 to 285 MeV. The use
of kinematically complete events allows a detailed analysis of the invariant
mass distributions to be made and reveals that there must be some
isospin-one ππ production even for relatively low values of Mππ.
Final results will be presented and discussed.
*Supported by the COSY-FFE programme.