Aumann, T.

Chartier, M.

Chulkov, L.

Lemmon, R.

Panin, V.

Plag, R.

Taylor, J.

Wamers, F.

GSI Repository

Fully Exclusive Measurements of Quasi-Free Knockout Reactions With 12C ∗V. Panin1,2, J. Taylor3, T. Aumann1,2, M. Chartier3, L. Chulkov1, R. Lemmon4, R. Plag1, F. Wamers1,2,and the R3B collaboration1Institut fu¨r Kernphysik, TU Darmstadt, Germany; 2Kernreaktionen und Nukleare Astrophysik, GSI Darmstadt,Germany; 3Physics Department, University of Liverpool, UK; 4STFC Daresbury Laboratory, UKA novel experimental method of measuring quasi-freeknockout reactions in inverse and complete kinematics isbeing developed as an ideal way to study single-particlestructure of exotic nuclei. First results from the obser-vation of (p,2p) reactions with a benchmark 12C beam at400MeV/u were reported previously [1, 2]. The reactionmanifests itself in a strong spatial correlation of the emerg-ing nucleon pair and the residual nuclear system carriesthe information about the single-particle states involved inthe reaction. In particular, the internal momentum of theknocked-out proton can be extracted by measuring the re-coil momentum of the (A-1) fragment. The same infor-mation can be obtained redundantly from the kinematics ofthe outgoing proton pair. Figure 1 illustrates the correlationbetween these two methods applied to the case of a protonknockout from the valence p-shell in 12C. [MeV/c]fragment yP-400 -300 -200 -100 0 100 200 300 400 [MeV/c]proton yP-400-300-200-1000100200300400050100150200250300350400450 [MeV/c]fragment yP-400 -300 -200 -100 0 100 200 300 400 [MeV/c]proton yP-400-300-200-100010020030040002468101214161820Figure 1: Correlation between the internal momentumcomponent reconstructed via outgoing proton pair and therecoil momentum component of 11B fragment from thesame reaction. Top figure shows the kinematical simula-tion and the bottom figure is the experimental data. Thecross-like shape is due to uncertainty of which one of thetwo protons is knocked out.∗Supported by GSI - TU Darmstadt cooperation, HIC for FAIR andBMBF (05P12RDFN8, 06DA7047I)A detailed simulation of the experimental response hasbeen developed based on Geant3 and FAIRroot/R3Brootsoftware packages [3]. The improved geometrical descrip-tion includes aluminum casing of NaI crystals in the Crys-tal Ball detector, which is aimed at the detection of out-going protons. Additionally, copper holding structure forthe silicon trackers, target-wheel motor and other materialssurrounding the reaction target have been introduced intothe simulation. An event generator for quasi-free scatteringreactions with the proper kinematics has been implementedin the simulation code. The results of the simulation arecompared to the experimental data as shown in Figure 2.The absolute efficiency for the simultaneous detection oftwo protons in the Crystal Ball is found to be 62±2 %.Multiplicity of proton clusters in CB0 1 2 3 4 5 6 7 8Percentage %01020304050607080 target (BG subtracted)2HSimulationSize of proton clusters in CB0 1 2 3 4 5 6 7 8 9 10Percentage %01020304050607080Figure 2: Simulated and experimental multiplicity distri-butions of high-energy proton hits (clusters) in the CrystalBall under the condition to observe at least one non-zerosignal in any crystal. The inset figure illustrates the num-ber of crystals forming individual clusters in the case oftwo-proton hits.Further development of the simulations will concern theresponse of the detector with respect to γ-rays accompany-ing the reactions. Theoretical calculations of the reactioncross sections and the momentum distributions are also un-der development.References[1] V. Panin et al, GSI Scientific Report 2010.[2] V. Panin et al, GSI Scientific Report 2011.[3] http://fairroot.gsi.de/GSI SCIENTIFIC REPORT 2012 PHN-ENNA-EXP-27157

Fully Exclusive Measurements of Quasi-Free Knockout Reactions with $^{12}$C

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Fully Exclusive Measurements of Quasi-Free Knockout Reactions with $^{12}$ C

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Fully Exclusive Measurements of Quasi-Free Knockout Reactions with 12^{12}12C

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Fully Exclusive Measurements of Quasi-Free Knockout Reactions with $^{12}$ C