Dresden 2013 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 6: Hadronenstruktur und -spektroskopie

HK 6.5: Vortrag

Montag, 4. März 2013, 12:15–12:30, HSZ-304

Status of the Investigations of the I(J^P) = 0(3⁺) Resonance Structure in the Two-Baryon-System^*. — •Mikhail Bashkanov — Physikalisches Institut der Universität Tübingen

The double-pionic fusion reaction pn → dπ⁰π⁰ has been observed [1] to be dominated by a resonance structure at √s = 2.37 GeV with Γ ≈ 70 MeV and I(J^P) = 0(3⁺), which is tightly correlated with the so-called ABC effect, an intriguing low-mass enhancement in the spectrum of the ππ inavriant mass. In order to reveal the nature of this structure we have measured its possible decay channels dπ⁺π⁻, ppπ⁰π⁻, np π⁰π⁰, NNπ and pn by pd collisions in the quasi-free reaction mode utilizing WASA at COSY.

The isospin decomposition of the dπ⁺π⁻ data confirms that the resonance shows up in the isoscalar (dπ⁰π⁰), but not in the isovector (dπ⁺π⁰) fusion channel.

The ppπ⁰π⁻ data are consistent with a decay branch also into this channel. The impact of this observation onto the vertex formfactor used in the description [1] of the dπ⁰π⁰ channel will be discussed.

The pn decay channel, the experimentum crucis, as well as the np π⁰π⁰ channel have been meausred by use of vector-polarized deuterons in inverse kinematics. The data analysis of this beamtime is in progress, its status will be reported.

[1] P. Adlarson et al., Phys. Rev. Lett. 106 242302 (2011)

^*supported by BMBF and COSY-FFE (FZ Jülich)