Dissertation / PhD Thesis

GSI-2013-01035

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Fully exclusive measurements of quasi-free single-nucleon knockout reactions in inverse kinematics.

Panin, V. (Corresponding author)GSI*

2012
ULB Darmstadt Darmstadt

Please use a persistent id in citations: urn:nbn:de:tuda-tuprints-31705

Abstract: This thesis will present a novel experimental method for investigating proton-induced single-nucleon knockout reactions at relativistic energies. For the first time this type of reactions is studied in complete and inverse kinematics, using a 12C beam at an energy of 400 MeV/u impinged on a plastic CH2 target, where the reactions on hydrogen take place. It is shown that the reaction mechanism is dominated by quasi-free proton-nucleon scattering process of a type (p,2p) or (p,pn) within the nucleus, that is reflected in a strong spatial correlation between the two outgoing nucleons. The reactions are foreseen as an ideal way to explore single-particle and cluster structure of nuclei and will become an important part of the physics program at the future R3B (Reactions with Relativistic Radioactive Beams) experiment at FAIR, which will be based on kinematically complete measurements of the reactions with neutron-proton asymmetric nuclei. The benchmark experiment, which is discussed in this work, was performed at a prototype LAND-R3B setup at GSI, Germany. The total cross section of 30.5±2.3 mb has been measured for the 12C(p,2p)11B reaction in inverse kinematics, and the cross section of 18.1±2 mb has been extracted for the removal of a proton from the p-shell in 12C. Employing the in-flight γ-ray spectroscopy, the following exclusive (p,2p) cross sections are determined for individual low-lying p-hole states in the residual 11 B nucleus: 12.7±1.5 mb for the ground state, 3.1±0.4 mb for the first excited state 2.125 MeV (1/2− ) and 2.2±0.3 mb for the excited state 5.02 MeV (3/2− ). The excitation energy of deep-hole particle-unstable states is reconstructed via invariant-mass measurements of mainly two-body decays of the 11B residue. A broad peak at around 15 MeV in the excitation spectrum of 11B is observed and interpreted as a proton knockout from strongly bound s-shell in 12C. The internal momentum distribution of protons, which are removed from the p-shell in 12C, is measured redundantly using two methods: the detection of residual 11B fragments and the angular and energy measurements of scattered proton pairs. The momentum width of 105 MeV/c is extracted using both methods. A similar value of 106 MeV/c is obtained for the internal momentum width of p-state neutrons probed through the 12C(p,pn)11C reaction. The momentum width of 132 MeV/c is determined for deeply bound s-shell protons via the measurements of scattered protons. Detailed simulations of the experimental response have been developed as a part of the analysis.

Keyword(s): Dissertation

Note: Dissertation, Technische Universität Darmstadt, 2012

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Contributing Institute(s):

1. Kernreaktionen (KRA)

Research Program(s):

1. 533 - Exotic Nuclei and Nuclear Astrophysics (ENNA) (POF2-533) (POF2-533)
2. R3Bsetup-detectors - R3B Setup/Detektoren (R3Bsetup-detectors) (R3Bsetup-detectors)
3. HGF-IVF-VH-GS-201 - HGS-HIRe : (HGF-IVF-VH-GS-201) (HGF-IVF-VH-GS-201)

Appears in the scientific report 2012

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