Study of repulsive nature of optical potential for high energy 12 C+ 12 C elastic scattering (Effect of the tensor and three-body interactions) Gaolong Zhang School of Physics and Nuclear Energy Engineering Beihang University

School of Physics and Nuclear Energy Engineering Report contents  Introduction  Research contents  Experimental setup  Summary

School of Physics and Nuclear Energy Engineering ✦ Understanding the interactions between composite nuclei (AA interactions), starting from NN interaction: Introduction (1) One of the fundamental subject in nuclear physics (2) One of the key issue to understand various nuclear reactions: * optical potentials: elastic scattering * distorting potentials as a doorway to various reactions (inelastic, transfer, breakup, etc.) (3) Important to survey unknown nuclear structures/reactions of unstable nuclei far from the stability lines.

School of Physics and Nuclear Energy Engineering The self-consistent nuclear mean field for finite-nuclear system is an attractive potential as a whole. The optical potentials for low energy nucleons scattered by finite nuclei are known to have an attractive real part together with an absorptive imaginary part. T. Furumoto, Y. Sakuragi, and Y. Yamamoto, Phys. Rev. C 79 (2009) R. The effect of TBF is clearly seen in the real part of FMP over the whole range of internuclear distance. Whereas the effect on the imaginary part is small except at distances less than 3 fm.

School of Physics and Nuclear Energy Engineering The optical potential for nucleons is highly dependent on the incident energy, and the depth of the attractive real part become shallower as the energy increases. Finally, the potential changes its sign from negative (attractive) to positive (repulsive). T. Furumoto, Y. Sakuragi, and Y. Yamamoto, Phys. Rev. C 82 (2010)

School of Physics and Nuclear Energy Engineering NN tensor force also plays an important role in the attractive to repulsive transition of the AA potentials Decompose the DFM potential into Spin (S) and isospin (T) components V ST ♦ (S,T)=(0,0) and (0,1) do not include the tensor force ♦ (S,T)=(1,0) and (1,1) include the tensor force T. Furumoto, Y. Sakuragi, and Y. Yamamoto, Phys. Rev. C 82 (2010) ST=01,10 and 00,11 become less attractive and more repulsive, respectively. V 11 has a largest energy dependence. Mainly from two origins: one is the factor (2S+1)(2T+1); The other is the tensor force contribution.

School of Physics and Nuclear Energy Engineering 12 C+ 12 C elastic scattering at E/A= MeV real potential change to: repulsive at E/A= MeV T. Furumoto, Y. Sakuragi, and Y. Yamamoto, Phys. Rev. C 82 (2010)

School of Physics and Nuclear Energy Engineering T. Furumoto, Y. Sakuragi, and Y. Yamamoto, Phys. Rev. C 82 (2010)

School of Physics and Nuclear Energy Engineering ❖ This results preserve our hope to get clear evidence of the repulsive nature of nucleus-nucleus optical potentials by measuring the elastic scattering angular distributions in this energy range Research contents ❖ No experimental evidence exists so far for the repulsive nature of heavy-ion optical potentials in this energy range. Therefore, on the basis of the present analyses, we propose the experimental measurements of elastic scattering angular distributions in the 12 C+ 12 C system, particularly the careful measurements of the characteristic evolution of the diffraction pattern with the increase of the incident energy in the range of E/A= MeV.

School of Physics and Nuclear Energy Engineering ❖ We will explore the tensor force effect, which plays an important role for lowering the attractive to repulsive energy. ❖ We will observe the diffraction pattern caused by the interference between the nearside and the farside amplitude. Such experiments will provide us with decisive evidence for the repulsive nature of heavy-ion optical potentials as well as the information about the energy region where the attractive to repulsive transition occurs.

School of Physics and Nuclear Energy Engineering ❖ The experimental determination of the transition energy through elastic scattering provides quite important information about the TBF effect (particularly, its repulsive component), which is one of the most important medium effects in high density nuclear matter, and its energy dependence, in addition to the role of tensor force.

Brief Introduction  The simulation software is “Data Desk”.

Simulation purpose Relation between scattered angle and scattered kinetic energy Purpose Distribution of the scattered 12 C particles on the MWPC

Beam Inside target Out of target Beam size (5  5mm) Normal distribution (x,y) Energy loss Elastic and inelastic scatter Multiple scatter Flight distance (L) Time of flight (TOF) Distribution on MWPC Simulation process

Analysis Thickness Ratio of excited state Detector resolutions Energy & TOF Flight distance Spacing of MWPC Beam size Factors Guo Chenlei et al., is accepted by Chin. Phys. C The angular range: 0.5-5, the angular resolution: 0.2, the beam size: 5mm, so the distance is about 3m from the target center to detector center. The coverage of detector is 30cm  30cm.

School of Physics and Nuclear Energy Engineering Experimental setup Experimental setup

School of Physics and Nuclear Energy Engineering Target: 2mm thickness T1: plastic scintillation detector, 2 parts, one part: 20cm  10cm  3mm T2: plastic scintillation detector, 3 parts, one part: 30cm  10cm  5mm MWPC: 30cm  30cm, wire space<5mm CsI: 30cm  30cm, 4  4 array, one part: 7cm  7cm  25cm Target: 2mm thickness T1: plastic scintillation detector, 2 parts, one part: 20cm  10cm  3mm T2: plastic scintillation detector, 3 parts, one part: 30cm  10cm  5mm MWPC: 30cm  30cm, wire space<5mm CsI: 30cm  30cm, 4  4 array, one part: 7cm  7cm  25cm

School of Physics and Nuclear Energy Engineering scattering chamber and detector setup

CsI detector

Monitor detector

School of Physics and Nuclear Energy Engineering Summary  Physics: Study an effect of tensor forces and three- body interactions in heavy-ion reactions.  Experiment: 12 C + 12 C elastic scattering at beam energies from 200A to 400A MeV.  We observe the transition energy where the optical potential changes from attraction to repulsion.  This transition energy depend strongly on tensor force and three-body interactions.

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