1. Tatsushi Shima Research Center for Nuclear Physics, Osaka University
Origin of Matter and Evolution of Galaxies, Dec. 4-7, 2007, Sapporo
Experimental Nuclear Astrophysics
with Real Photon Beams
Tatsushi Shima
Research Center for Nuclear Physics, Osaka University
Present Status of Nuclear Astrophysics Studies via Real Photons
Study of Photonuclear Reactions Relevant for Astrophysical
Nucleosynthesis with NewSUBARU LCS g-ray Beam

2. Radiative captures/Photodisintegrations in Astrophysical Nucleosynthesis
Big Bang nucleosynthesis
p(n,g)d, d(p,g)3He, 3H(a,g)7Li, 3He(a,g)7Be, …
Stellar He-burning, s-process
4He(2a,g)12C, 12C(a,g)16O, (n,g)
r-, p-, g-processes
(p,g), (n,g), (g,x)
n-A interactions ; (n,n’x) ⇔ (g,x) ; 4He, 12C, …

3. Photonuclear reactions as a tool for nuclear astrophysics
EM interaction; well-know !
Sensitivity to multi-body channels;
X+Y+Z+…→A+g ⇔ A+g → X+Y+Z+…
ex. 2a+n → 9Be, 3a → 12C
Enhancement of cross sections by
phase space factor
Analogy between g-A and n-A interactions

4. n-A ⇔ g-A
Weak operators (neutral current) ;
EM operators ;

5. Low-energy g-ray sources
Discrete g-rays from radioisotopes
Bremsstrahlung (continuous energy) / tagged photons
e+e- pair annihilation in flight ; monoenergy g + brems.
Laser Compton Scattered g (LCS-g) NEW !
Synchrotron photons from super-conducting wiggler NEW !
--- quasi-Planck spectrum (Utsunomiya, Nucl. Phys. A777)
Coulomb dissociation ; virtual photons, application to RI
7Be(p,g)8B, 3H(a,g)7Li, 14C(n,g)15C, …

6. Laser Compton backscattering
Relativistic electron (Ee)
Laser light (lL)
g (Eg)
Eg(q)
ex. lL=1.064mm, Ee=800MeV
⇒ Eg = 11MeV q

7. Energy distributions e+e- annihilation in flight
Laser Compton-Scattered g
--- needs subtraction of
brems. component
sharp and no BG !!

8. LCS-g ; features Quasi-monochromatic; DE/E ~ a few %, no low-energy BG
Well-collimated; Dq < 0.1 mrad
Highly polarized; linear or circular, P ~ 100%
Continuous or pulsed; Dt < 10ns

9. LCS g-ray facilities in the world
Year
Facility Ee
[GeV]
Laser Eg
[MeV]
Fg [/sec/MeV]
1964
Lebedev
0.6
ruby
~10
~ 106
1965
Harvard / CEA 6
~1000
5×104
1978
Frascati / LADON
1.5
Ar+
5 - 80
~ 105
1985
ETL(AIST) / TERAS
Nd-YAG
2 - 40
103 ~105
1990
BNL / LEGS
2.8
104 ~ 105
1996
Grenoble / GrAAL
1500
~ 4×103
1999
SPring-8 / LEPS 8
~104
TUNL(Duke) / HIgS
FEL
2 - 70
~ 107
2004
LASTI(U. Hyogo) / NewSUBARU
Nd-YVO4
105 ~ 106

10. AIST/LCS g-source LCS beam 1 ~ 40 MeV LCS-3 e- laser light
RF cavity
Kicker
LCS-3
Electron storage ring, “TERAS”:
300 – 800 MeV, 300 mA QF QD QF
Injection BTS e-
Septum
laser light
1 m
2 m

11. Experimental Setup

12. Photodisintegration of 4He
● T. Shima et al.,
PR C72, (2005)
Theoretical calculations :
Londergan and Shakin (1972), Continuum Shell Model
Sandhas et al. (1998), Faddeev-AGS formalism with MT I+III
Gazit et al. (2006), Lorentz integral transform with AV18+UIX
Trini et al. (2007), Refined RGM with AV18+UIX

13. Neutron detector for (g,n) (Konan Univ.)
4p Long counters
Beam dump (NaI(Tl) detector)

14. p(n,g)d astrophysical S-factor
T.S. Suzuki et al., ApJ. Lett. 439, L59 (1995)
Y. Nagai et al., PR C56, 3173 (1997)
K.Y. Hara, H. Utsunomiya et al., PR D68, (2003)

15. Duke/HIgS (High Intensity g-ray Source)
Intra-cavity Compton Backscattering of FEL photons
by electrons circulating in the 1.2GeV Duke Storage Ring
Eg = 2~70 MeV, DEg/Eg ~ 1%, Fg ~ 107 /MeV/s (→ 109 )
Time interval of g-ray pulses ; 170ns

16. M1/E1 ratio in d(g,p)n

17. NewSUBARU Lab. of Adv. Sci. and Tech. for Industry,
University of Hyogo, Japan

18. NewSUBARU/LCS “Top-up” mode ⇓ stable Eg , Fg Linac e- 1.0GeV
K. Aoki, S. Miyamoto, et al. NIM A516 (2004)
Linac e-
1.0GeV
“Top-up” mode ⇓
stable Eg , Fg
Eg ; MeV, Fg = 104~6 photons/MeV/s, DEg/Eg ~ 3%

19. 4He Neutrino-heating in SN via 4He(n,n’p)3H, 4He(n,n’n)3He
Production of 7Li, 11B in hellium shell via
4He(n,n’p)3H, 4He(n,n’n)3He
4He(n,n’p)3H(a,g)7Li(a,g)11B
4He(n,n’n)3He(a,g)7Be(e-,ne)7Li

20. Neutrino neutral reaction rate on 4He

21. Previous data have been obtained by means of
monochromatic g, bremsstrahlung, radiative capture...

22. Experiment with quasi-monochromatic g at NewSUBARU (Hyogo, Japan)
Laser-Compton backscattered g-ray :
Eg = 16 ~ 40MeV, Fg ~2×104 /sec, FWHM~3%, P~100%

23. Real photon beam + Active target
LCS-g :
• high resolutions of Eg, direction, and time (pulsed)
→ no low-energy BG g, good signal-to-noise ratio
• high polarization; ~100% → E1/M1 separation
TPC : He +CH4 (CD4) ; active target
• W ~ 4p , e 100%
→ little uncertainties in detector sensitivity
• track shape, dE/dx → reliable event ID
• capability to simultaneous measurements of
two-body and multi-body reaction channels

24. g-ray intensity Fg = 23000 /s l = 532nm, Ee = 0.974GeV
Eg(max) = 32.8MeV
Flux monitor; plastic scintillator
Fg = /s

25. Event Identification
4He photodisintegrations
4He(g,p)3H
4He(g,n)3He

26. 12C photodisintegrations
12C(g,p)11B
12C(g,n)11C

27. Three-body decays
4He(g,pn)2H
12C(g,2a)4He

28. Backgrounds
a from natural RI
Photoelectrons

29. D(g,p)n

30. 4He(g,n)3He / D(g,n)p ; energy loss spectra

31. Distribution of reaction point

32. Efficiency check by D(g,p)n (preliminary)

33. 4He(g,p)3H (preliminary)
● RCNP-AIST2005 (PRC72, ) ; l=351nm (3rd), Ee=0.8GeV
● RCNP-NewSUBARU; l=532nm (2nd), Ee=0.97GeV
● RCNP-NewSUBARU; l=1064nm (fund.), Ee≤1.46GeV
● RCNP-AIST2005 (PRC72, ) ; l=351nm (3rd), Ee=0.8GeV

34. 4He(g,n)3He (preliminary)
● RCNP-AIST2005 (PRC72, ) ; l=351nm (3rd), Ee=0.8GeV
● RCNP-NewSUBARU; l=532nm (2nd), Ee=0.97MeV
● RCNP-NewSUBARU; l=1064nm (fund.), Ee≤1.46GeV
● Lund (PRC75, ) ; tagged photons

35. 4He(g,pn)d (preliminary)

36. Summary Laser Compton Scattered g is a useful technique for
high-precision studies of nuclear reactions induced by
photons and also neutrinos.
The LCS g-source at NewSUBARU is now in operation, and
several works for nuclear astrophysics have been performed
successfully.
ex. Measurement of half-life of 184Re populated by LCS-g,
T. Hayakawa et al., PRC74, (2006)
4He: excitation functions are measured up to 37MeV.
Smallness of the cross sections below 30MeV was confirmed.
GDR peak was found to locate at ~32.5MeV.
Light elements (12C, 16O) and heavier p-nuclei are to be studied.

37. Collaborators H. Utsunomiya, H. Akimune
Department of Physics, Konan University
T. Mochizuki, S. Miyamoto, K. Horikawa
Laboratory for Advanced Science and Technology for Industry,
University of Hyogo
T. Hayakawa, T. Shizuma
Kansai Photon Science Institute, Japan Atomic Energy Agency
M. Fujiwara
Research Center for Nuclear Physics, Osaka University
Y. Nagai
Nuclear Science and Engineering Directorate,
Japan Atomic Energy Agency