Köln 2004 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 33: Heavy Ions III

HK 33.8: Vortrag

Mittwoch, 10. März 2004, 16:15–16:30, E

T-odd asymmetry in ternary fission of 239Pu(n,f) — •Friedrich Goennenwein¹, Alexei Gagarski², Guenadi Petrov², Peter Jesinger¹, Manfred Mutterer³, and Valeri Nesvishevski⁴ — ¹PIT, U Tuebingen, Germany — ²PNPI, Gatchina, Russia — ³IKP, TU Darmstadt, Germany — ⁴ILL, France

In ternary fission induced by cold polarised neutrons a T-odd asymmetry has recently been observed. In these experiments a triple correlation is measured between the neutron spin pointing parallel to the beam, the momentum of the light fission fragment and the momentum of the light charged particle(LCP), both momenta lying in a plane perpendicular to neutron spin. In the fissile U- and Cm-isotopes the asymmetry of LCP emission relative to the plane formed by neutron spin and fragment momentum is approaching the 0.5% level and hence quite sizable. Surprisingly, in the newly analysed reaction 239Pu(n,f) no asymmetry within the 0.02% error bars is detectable. In theoretical models the T-odd asymmetry is attributed to final state effects between the three outgoing particles. Both in statistical and dynamical models the Pu result may be understood as being due to the small compound spin of 240Pu (0 or 1) while in the U- and Cm isotopes this spin ranges from 2 to 4 Planck units.