Experimental study of pionic fusion 4He(3He,π0)7Be

Gašparić, Igor (2011) Experimental study of pionic fusion 4He(3He,π0)7Be. Doctoral thesis, Faculty of Science > Department of Physics.

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Abstract

Pionic fusion reactions where two nuclei fuse into a new one by emitting a pion need a highly coherent mechanism and therefore give an insight into the collective motion of nucleons in nuclei. The reaction 4He(3He,π0)7Be has been studied experimentally at beam energies about 10 MeV above the coherent production threshold. The experiment was performed at KVI, Groningen using the AGOR accelerator facility. The created nuclei were detected in a phoswich detector array in the focal plane of the Big-Bite Spectrometer in coincidence with the photons from neutral pion decay which were detected in the Plastic Ball detector. The Plastic Ball contains 552 phoswich detectors covering polar laboratory angles 50◦<0<160◦ in almost the full azimuthal range. To improve the photon detection efficiency an active inner shell of 64 CsI(Tl) crystals is put inside the Plastic Ball. The fused nuclei are identied by a pulse-shape analysis and a time-of- flight measurement. They are clearly correlated with two photons detected in the Plastic Ball at mutually large opening angles corresponding to pion decay. The event selection yields approximately 500 background-free pionic fusion events. The pion angular distribution is corrected for the acceptance and the eciency obtained from Monte Carlo simulations and normalized with the beam current. The measured differential cross section is compared to available theoretical calculations. The Legendre polynomial fit gives the total cross section σ=(53±9) nb.

Item Type: Thesis (Doctoral thesis)
Keywords: pionic fusion ; subthreshold pion production, CsI(Tl) scintillator, phoswich, magnetic spectrometer
Supervisor: Čaplar, Roman
Date: 28 June 2011
Number of Pages: 0
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 21 Dec 2013 23:10
Last Modified: 21 Dec 2013 23:10
URI: http://digre.pmf.unizg.hr/id/eprint/37

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