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Coulomb dissociation for astrophysics

Coulomb dissociation for astrophysics. T. Gomi (RIKEN ). 22 Mg(p,γ) 23 Al. Outline ・ Reaction scheme, experimental setup ・ Relation with stellar reaction, Experimental advantage ・ Experimental results, astrophysical implications

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Coulomb dissociation for astrophysics

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  1. Coulomb dissociation for astrophysics T. Gomi (RIKEN) 22Mg(p,γ)23Al Outline ・ Reaction scheme, experimental setup ・ Relation with stellar reaction, Experimental advantage ・ Experimental results, astrophysical implications ・ General questions for C.D. exp.

  2. Collaborators T. Gomi,1 T. Motobayashi,2 Y. Ando,1 N. Aoi,2 H. Baba,1 K. Demichi,1Z. Elekes,3 N. Fukuda,2 Zs. Fulop,3 U. Futakami,1 H. Hasegawa,1 Y. Higurashi,2 K. Ieki,1 N.Imai,2 M. Ishihara,2 K. Ishikawa,4 N. Iwasa,5 H. Iwasaki,6 S. Kanno,1 Y. Kondo,4 T. Kubo,2 S. Kubono,7 M. Kunibu,1 K. Kurita,1 Y. U. Matsuyama,1 S. Michimasa,7 T. Minemura,2 M. Miura,4 H. Murakami,1 T. Nakamura,4 M. Notani,7 S. Ota,8 A. Saito,1 H. Sakurai,6M. Serata,1 S. Shimoura,7 T. Sugimoto,4 E. Takeshita,1 S. Takeuchi,2 Y. Togano,1 K. Ue,6 K. Yamada,1 Y. Yanagisawa,2 K. Yoneda,2 and A.Yoshida2 1 Rikkyo university 5 Tohoku university 2 RIKEN 6 University of Tokyo 3 ATOMKI (Hungary) 7 CNS, University of Tokyo 4 Tokyo Institute of Tokyo 8 Kyoto University

  3. 22Mg 23Al 23Al* p γ Incident beam High-Z target (Pb) Coulomb dissociation method - measurement of the inverse reaction - one of the indirect method for study stellar reactions 22Mg(p,γ)23Al : stellar, radiative capture reaction inverse reaction 23Al(γ,p)22Mg ・ 2 particle in coincidence ・ momentum vector ・ invariant mass → relative energy corresponds to the CM energy inthe stellar reaction photo absorption

  4. stellar 22Mg(p,γ)23Al reaction Resonant capture reaction through the first excited state in23Al 1st excited state is located near Gamow window in typical Novae. Q: The influence is strong ?? or not ?? in stars. Level structure Strength ∝Γγ theoretical prediction NO measurement ! (Nova) Coulomb dissociation

  5. Experimental Setup - RIKEN RIPS beamline - Pb target 87mg/cm2 p 23Al 50AMeV 1m 22Mg Silicon telescope 2.5m NaI(Tl) detector (de-excitation γ-ray from 22Mg) 0.5m Plastic Hodoscope 15cm ・ suitable detectors for each particle ・ momentum vector ・ γ-ray detector (to confirm the final state) Position-sensitive （5mm width strips）

  6. Relation between Coulomb dissociation reaction and stellar capture reaction LARGE ! σC.D. = 4 mb 23Al + 208Pb → 22Mg + p + 208Pb : Coulomb dissociation Virtual photon theory σpeak = 30μb 23Al (γ,p) 22Mg : Photo absorption Detailed valance σpeak= 60 nb 22Mg ( p,γ) 23Al : Proton capture Large cross section of C.D. is …

  7. B + p B + p A A easydifficult 23Al etc… Advantage of Coulomb dissociation Exp. Compared to the capture reaction measurement Nuclear Structure suitable or not ? ・ Large cross section ～ mb ・ Intermediate energy beam (50AMeV) enable us to use thick target (87mg/cm2Pb) ・excited state below Sp ・can not simulate the inverse of stellar reaction, exactly ・ 23Al has simple structure, it’s suitable for C.D. exp. 400counts/3.5days with 104 cps C.D. hasLarge yield ! even ifWEAK beam ! When one measure the capture reaction, one should prepare 22Mg beam with 1013 cps. very intense beam, not attainable!! Up to now,…

  8. Stellar reactions studied by Coulomb dissociation using radioactive isotope beams Steady burning ⇒ recent result GSI (254AMeV) RIKEN, MSU (50～80AMeV) Notre Dome (3AMeV) Solar neutrino 7Be(p,γ)8B CNO cycle 14N(p,γ)15O RIKEN (100AMeV) (Coulomb excitation, sub-threshold state) Explosive burning 12C(p,γ)13N RIKEN (78AMeV) 13N(p,γ)14O RIKEN (88AMeV), GANIL (70AMeV ) hot CNO cycle 8B(p,γ)9C RIKEN (70AMeV) 11C(p,γ)12N GANIL,RIKEN (70AMeV) 12N(p,γ)13O RIKEN (84AMeV) hot pp mode 22Mg(p,γ)23AlRIKEN (50AMeV) 26Si(p,γ)27P RIKEN (50AMeV) rp-process r-process 8Li(n,γ)9Li MSU (40AMeV) Neutron capture 14C(n,γ)15C GSI (605AMeV), RIKEN (70AMeV), MSU (35AMeV) neutron induced CNO cycle r-process 18C(n,γ)19C RIKEN (67AMeV) → T.Nakamura

  9. GSI experiment : 7Be(p,γ)8B by F. Shumann, K. Suemmerer, et al. Lehrstuhl für Physik mit Ionenstrahlen (EP III) Arbeitsgruppe Nukleare Astrophysik Prof. Dr. C. Rolfs Talk: 21st Brussels Meeting 2004 Monday, 13.12.2004 Indirect determination of the astrophysical S-factor of 7Be(p,g)8B via high-energy Coulomb Dissociation of 8B Frank Schümann I will show the final result only

  10. S17 - Factor Descouvemont modell leads to S17(0)=20.4  1.2  1.0 eV-b. Recently, the experimental data was improved (blue circle) . and Descouvemount model leads to S17 (0)-factor. This agrees with the direct measurement data (triangle) by Junghans et al. (S17 (0)=22.3±0.7±0.5 eV・b) This results demonstrate that C.D. is an alternative method to determine S17-factor.

  11. Extension of the field of Coulomb dissociation experiment (p,γ) reaction sd-shell region Far from the stability p-shell region 22Mg(p,γ)23Al Back to ….

  12. Experimental result Relative energy spectrum 22Mg(p,γ)23Al Higher excited state 1st excited state (objective state) Counts /150keV continuum component: E1 , constant astrophysical S -factor 1000 2000 3000 4000 0 Relative energy [keV] ・ energy resolution 170keV (Erel = 400keV) ・ identify the reaction through the first excited state clearly.

  13. 0.528 (1/2+ : shell model) 22Mg g.s. (5/2+ : shell model) 23Al * 23Al P 23Al = (7.2 ±1.7) × 10-7 eV Angular distribution Coulomb + Nuclear l = 2 l = 1 consistent “βC”= “βN” distorted-wave calculation optical potential : 17O+208Pb (84AMeV) collective (vibrational) model Small “Nuclear” component : 8 % l = 2 Coulomb ONLY Coulomb and nuclear response is considered as same deformation parameter. Coulomb + Nuclear Compatible with the predicted value by J.A. Caggiano et.al. 5.49×10-7 eV Nuclear ONLY Astrophysical implications

  14. 106 104 ρ [g/cm3] 102 100 0.1 0.2 0.5 1.0 2.0 T [GK] 22Mg(p,γ)23Al Astrophysical implication our experimental data →reaction rate → competition with βdecay Nucleosynthesis in explosive hydrogen burning (Novae, X-ray bursts) Which? Nova Model M1 : J.Jose et al Astrophys. J. 520 347 (1999) M2 : C. Iliadis et.al. Astrophys. J. Supp. 142 105 (2002) Cosmic γ-emitter Ne nova M.Wiescher et.al. Phil. Trans. R. Soc. Lond. (1998) βdecay is favored rather than (p,γ) reaction

  15. Questions for Coulomb dissociation in general ・ Sensitivity depends on the transition type (E1, E2, M1,….) due to different fluxes of photons ・ For low-Z nuclei, “nuclear” component is not small. ・ Higher order processes (post acceleration, ….) To solve… Reaction mechanism etc.. → K. Ogata Experiments give various data. ・ incident beam with different energy ex: 3AMeV– 250AMeV ・ Low-Ztarget (probe) instead of Pb ex: p,α,C,… ・ angular or momentum distribution ・ selection of impact parameter ・ and so on. →T. Nakamura Theory Experiment

  16. Summary Coulomb dissociation method is useful to study astrophysical (p,γ), (n,γ) reactions. ・ measurement of the inverse reaction of the stellar reaction ・ advantage (large cross section, thick target) → large yields → we can access stellar reactions which direct measurement cannot. ・ 22Mg(p,γ)23Al - rp-process – resonant reaction rate through the first excited state reaction network (competition with βdecay) ・ This method has some questions theory + experiment will give the solution.

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