LUNA: an underground nuclear astrophysics laboratory: recent results and future perspectives

1. P. Corvisiero (INFN – Italy) on behalf of LUNA collaboration LUNA: an underground nuclear astrophysics laboratory: recent results and future perspectives

2. the ambitious task of Nuclear Astrophysics is to explain the origin and relative abudance of the elements in the Universe 1010 108 106 relative abundance 104 102 1 10-2 0 10 20 30 40 50 60 70 80 90 Atomic number the abundance of the elements in the Universe elements are produced inside stars during their life

3. A<60 M < 8 M star switches off (white black dwarf) M > 8 M star explodes (supernova) Hburning  He relative abundance He burning  C, O, Ne C/O … Si burning  Fe explosive burning Atomic number

4. p, 12C 13N p + p d + e+ + ne - p, d + p 3He + g pp chain CNO cycle 84.7 % 13.8 % 15N 13C 3He +3He a + 2p 3He +4He 7Be+g p, + 0.02 % 13.78 % 15O 14N 7Be+e- 7Li+g +ne 7Be +p 8B+g p, 7Li +p a + a 8B 2a + e++ ne Hydrogen burning produces energy for most of the life of the stars 4p  4He + 2e+ + 2e + 26.73 MeV

5. Maxw. energy distribution function (KT ~ keV) Z1Z2e2  tunneling probability KT << RN <v> = b E E1/2 KT  3He(3He,2p)4He 3He(,)7Be 14N(p,)15O 20 < E0 < 26 keV 8 1 S(E) exp dE  (KT)3/2 0 E0 the Gamow peak….

6. (E) = S(E)·exp(-2) /E S(E) = E·(E)·exp(2) ? 2 = 31.29 Z1 Z2 (/E)0.5 The astrophysical S-factor… extrapolation is needed….

7. but… sometimes extrapolation fails !! S(E) factor ? ?

8. Screening effect of atomic electrons interaction not between “bare” nuclei in the lab: atoms and/or ions interact in the stars: plasma electrons r < Ra: electr = cost  -Z1e/Ra tot = n + electr = Z1e/r - Z1e/Ra for r > Ra: Frepuls=0 Eeff = Z1Z2e2/Rn - Z1Z2e2/Ra Rn/Ra 10-5: negligible correction but if: RC > Ra barrier thickness dramatically changes. the electron screening….

9. measured: Ue=219 eV 3He(d,p)4He Adiab. limit: Ue=119 eV measured: Ue=109 eV d(3He,p)4He Adiab. limit: Ue=54 eV

10. how to overcome these experimental problems ??

11. Indirect methods Direct methods different approaches Coulomb dissociation ANC method (Asymptotic Normalization Coefficient) Trojan Horse method Recoil separator technique (ERNA) (Ecm > EG , but very precise measurement  better extrapolation) Underground experiments (LUNA)

12. spectator s A participant x c a C A VFm a x s Vrel=Va-VFm~ 0 Eax0 astrophysical energies Trojan Horse Method Quasi-free Mechanism 3-body Reaction a + A  c + C + s A cluster x  s to study a + x  c + C of astrophisical interest If: Ea >> Ecoul Coulombeffects (barrier + el. screen) are negligible

13. Trojan Horse Method 3-body cross section measured through coincidence detection c and C “bare” nucleus 2-body cross section of astrophysicalinterest astrophysical  measured  KF= kinematical factor |G(Ps)|2= momentum distribution of s inside A

14. 6Li(d,a)4He  6Li(6Li,a a)4He 6Li =d a Ue=340±51 eV Uth=186 eV (Engstler S. et al.: 1992, Z. Phys., A342, 471) • C.Spitaleri et al.: 2000, sottoposto Phys. Rev. C.) 7Li(p,a)4He  7Li(d,a a)n d =p  n Ue=350 eV Uth=186 eV (Engstler S. et al.: 1992, Z. Phys., A342, 471) •(Spitaleri C. et al.: 1999, Phys. Rev., C60, 055802)

15. coincidence Requirements Advantages Disadvantages • inverse kinematics (gas target) • beam purification (Ycont<<Yreac) • 100% transmission for the selected charge state • well defined recoil charge state (evtl post stripping) • high suppression of the incident beam (Yrec/Yleaky=1, Fsuppr=sNt, no coinc.), e.g. F ~10-15 for s~ 10-9 b • gas target • low background • high detection efficiency: e=F(qrec) • measure stot • background free g-ray spectra • difficult to do Recoil Mass Separator Cn+ B A detection  A C purification detection separation

16. on source Dynamitron tandem accelerator recoil transport Magnetic quadrupole multipletts beam purification g - raydetection gastarget DE-E Detector Wien filter Wien filter recoilseparation 60° dipole magnet ERNA setup

17. 16O recoils SuppressionR~8*10-12 “leaky” beam 12C(a,)16O Ecm=2.5 MeV

18. 12C(a,)16O • Astrophysical motivation: • The cross section at the relevant Gamow-energy, Eo = 0.3 MeV, determines: evolution and nucleosynthesis of massive stars; • dynamics of supernovae; • kind of remnants after supernova explosions.

19. 12C(a,)16O: present situation 2+ (2.68 MeV)  (relative units) 1- (2.4 MeV) Ecm [MeV]

20. go underground…

21. Shower on LNGS GranSasso underground halls Background reduction in LNGS (shielding  4000 m w.e.) Cosmic shower

22. LUNA logo Luna logo LaboratoryUndergroundNuclearAstrophysics " Some people are so crazy that they actually venture into deep mines to observe the stars in the sky ". (Naturalis Historia - Plinio, 23-79 B.C.)

23. LUNA 1 50 kV LUNA 2 400 kV LUNA underground Laboratories LUNA site

24. p + p d + e+ + ne d + p 3He + g pp chain 84.7 % 13.8 % 3He +3He a + 2p 3He +4He 7Be+g 0.02 % 13.78 % 7Be+e- 7Li+g +ne 7Be +p 8B+g 7Li +p a + a 8B 2a + e++ ne LUNA results

25. 3He(3He,2p)4He

26. p + p d + e+ + ne d + p 3He + g pp chain 84.7 % 13.8 % 3He +3He a + 2p 3He +4He 7Be+g 0.02 % 13.78 % 7Be+e- 7Li+g +ne 7Be +p 8B+g 7Li +p a + a 8B 2a + e++ ne LUNA results

27. d(p,)3He

28. ----- IA IA + … +  sizeable effect of non nucleonic degrees of freedom Viviani et al.: PRC61 (2000) 064001

29. allowed beams : protons, alphas Vmax = 50 - 400kV Imax = 650 A Energy spread : 72eV • Total uncertainty • 300 eV between Ep=100400 keV precise knowledge of the energy calibration of the accelerator LUNA II Foto LUNA 400 kV at LNGS:

30. experimental program in progress Emin~140 keV: published 14N(p,)15O Emin~70 keV: coming soon… Short term program 4He(3He,)7Be 25Mg(p, )26Al Long term program new scientific proposal new machine (?)

31. p, 12C 13N - p, CNO cycle 15N 13C p, + 15O 14N p, (15O) 1,141 (13N) 1,140.85 14N(p,)15O Determines neutrino flux from CNO cycle

32. S 14,1 /5 S 14,1 x5 Standard CF88 CNO pp-chain 14N(p,)15O Turn Off luminosity The onset of the CNO

33. + Solid target HpGe detector • single transitions • angular distribution • low efficiency • high density- pointlike • high resolution Gas target + BGO summingcrystal • total S(E) target purity • low resolution • target stability • high efficiency 2 experimental approaches Emin~140 keV Emin ~ 70 keV

34. earth surface Yield 3MeV < Eg < 8MeV 0.5 Counts/s Yield Underground 3MeV < Eg < 8MeV 0.0002 Counts/s 410-8 counts/s/keV HpGe background

35. ECM (keV) Ex (keV) 893 3/2+ 8284 259 7556 1/2+ Q = 7297 6790 -507 6176 -1121 5180 -2117 0 0+ 15O 14N(p,g)15O is the bottleneck of the CNO cycle and regulates the release of energy and the H consumption.

36. Level structure of 15O Ep [keV] Ex [keV] Jp 8284 3/2+ 1058 278 7556 1/2+ 7276 7/2+ 7297 14N+p 6793 3/2+ -504 6176 3/2- 5183 1/2+ 0 1/2-

37. Ground state transition

38. Ground state transition

39. Ground state transition

40. Ground state transition

41. Ground state transition

42. S0tot = 1.7 ± 0.1 keV b LUNA (’04) (Phys. Letter B) GC age increased by 0.7-1 Gyr • CNOneutrino flux • reduced by a factor  2 Conclusions from the first phase of the experiment

43. Good agreement between LUNA and LENA !!

44. beam current calorimeter gas target beam Second phase: BGO and gas target

46. Gas target results (preliminary) four orders of magnitude !! LUNA gas target LUNA solid target • gas target data • solid target data Schroeder PRELIMINARY 71 keV

47. S - factor (preliminary) PRELIMINARY

48. p, 12C 13N p + p d + e+ + ne - p, d + p 3He + g pp chain CNO cycle 84.7 % 13.8 % 15N 13C 3He +3He a + 2p 3He +4He 7Be+g p, + 0.02 % 13.78 % 15O 14N 7Be+e- 7Li+g +ne 7Be +p 8B+g p, 7Li +p a + a 8B 2a + e++ ne future program @ LUNA

49. Eg =1585 keV + Ecm (DC  0); Eg = 1157 keV + Ecm (C  0.429) Eg = 429 keV E = 478 keV 3He(a,)7Be(e,n)7Li*()

50. 3He(a,)7Be(e,n)7Li*() SEATTLE 98 S34=(0.572±0.026) keV·b [5%] S34=(0.507±0.016) keV·b [3%] Adopted S34=(0.53±0.05) keV·b [9%] NACRE 99 S34=(0.54±0.09) keV·b [16%]