Reaction rates for nucleosynthesys of light and intermediate-mass isotopes

Transcription

1 Reaction rates for nucleosynthesys of light and intermediate-mass isotopes Gianluca Imbriani Physics Department of University of Naples Federico II, Italian National Institute of Nuclear Physics (INFN) and Joint Institute of Nuclear Astrophysics (JINA)

2 but before I would like to remind..

3 s [b] Charged particle reaction in stars nuclear well V E C ~ z 1 z 2 r n z 1 z 2 Example z 1 =p and z 2 =p (e.g. in the Sun) projectile r E ~ kt T ~ 15x10 6 K E = kt ~ 1 kev E C = 550 kev during quiescent burnings: kt << E c reactions occur through TUNNEL EFFECT 1E-04 1E-08 1E-12 1E-16 1E-20

4 S [kev b] Astrophysical factor and Gamow peak σ E S E E exp - 2 η Z Z e 1 2 ν E [kev] reaction Coulomb barrier (kev) E 0 (kev) p + p C O + 16 O Maxwell-Boltzmann distribution Gamow peak Tunneling through Coulomb barrier

5 sub-threshold resonance S(E)-FACTOR many orders of magnitude CROSS SECTION s(e) LOG SCALE Problem of extrapolation resonance E G non-resonant direct measurements S(E) LINEAR SCALE extrapolation needed! extrapolation direct measurement E G low-energy tail of broad resonance non resonant process p+p [kev] 3 He+ 3 He [kev] 3 He+ 4 He [kev] Interaction energy E 7 Be+p [kev] 14 N+p [kev] Most of the reactions of astrophysical interest happen via radiative capture. 3 He(,g) 7 Be, 14 N(p,g) 15 O, 12 C(,g) 16 C... -E r 0 E r interaction energy E

6 Why going underground 1 st 40 K 214 Bi 232 Th Gran Sasso shielding: 3800 m w.e. 40 K 214 Bi 232 Th E>4MeV environmental radioactivity cosmic rays Therefore, the advantage of an underground environment is evident for high Q-value reactions such as 14 N(p,g) 15 O, 15 N(p,g) 16 O, 17 O(p,g) 18 F, 25 Mg(p,g) 26 Al... Radiation muons neutrons LNGS/out

7 Why going underground 2 nd 11 B(p,g) 12 C HpGe spectrum E cm = 230keV «light» Pb shielding Beam induced background 14 N(p,g) 15 O - EPJA 25(2005)

8 LUNA experimental set-ups LNGS Lab LUNA I 50 kv Voltage Range : 1-50 kv Output Current: 1 ma Beam energy spread: 20 ev LUNA II 400 kv Voltage Range : kv Output Current: 500 ma Beam energy spread: 70 ev

9 LUNA program: astrophysical motivation Solar neutrinos: 3 He( 3 He, 2p) 4 He, 3 He(,g) 7 Be, 14 N(p,g) 15 O Big Bang nucleosynthesis: 2 H(p,g) 3 He, 3 He(,g) 7 Be, 4 He(d,g) 6 Li Age of Globular Clusters and C production in AGB: 14 N(p,g) 15 O Light nuclei nucleosynthesis - 17 O/ 18 O abundaces, F origin, 26 Al g-ray in the Galaxy, 26 Mg excess...: 15 N(p,g) 16 O, 17 O(p,g) 18 F(b + ) 18 O, 25 Mg(p,g) 26 Al(b + ) 26 Mg

10 14 N(p,g) 15 O: LUNA results LUNA/NACRE BGO spectrum E cm =70keV HpGe spectrum E cm =110keV D. Bemmer, et al. NuPhyA 779(2006) G. Imbriani, et al., EPJA 25(2005)

11 14 N(p,g) 15 O: astrophysical consequences G. Imbriani, et al., A&A 420(2004) Stellar calculation done with the FRANEC code The age of the oldest Globular Clusters should be increased by about Gyr. The lower limit to the Age of the Universe is 14 ± 1 Gyr. In good agreement with the precise detrmination of WMAP. With 14 N(p,γ) 15 O rate = ½ of NACRE better agreement between observation and calculation.

12 H-shell Solar neutrinos: 3 He( 3 He, 2p) 4 He, 3 He(,g) 7 Be 14 N(p,g) 15 O Big Bang nucleosynthesis: 2 H(p,g) 3 He, 3 He(,g) 7 Be, 4 He(d,g) 6 Li Age of Globular Clusters and C production in AGB : 14 N(p,g) 15 O Light nuclei nucleosynthesis - 17 O/ 18 O abundaces, F origin, 26 Al g-ray in the Galaxy, 26 Mg excess...: 15 N(p,g) 16 O, 17 O(p,g) 18 F(b + ) 18 O, 25 Mg(p,g) 26 Al(b + ) 26 Mg,

13 15 N(p, )/(p,g): first branch of the CNO cycle S(0) kevb DIRECT MEASUREMENTS Hebbard 60 NuPhy 15(1960) Rolfs 74 NuPhy A 235(1974) LUNA-ND PRC 82(2010) INDIRECT MEASUREMENTS Mukhamedzhanov et al. PRC 78(2008) 32 ± 6 64 ± ± ± y 13 C 10 m 13 N 12 C e + n y CN 2 m (p, y 14 N y 15 O 15 N e + n (p, NO 17 O e + n 64 s 17 F 16 O (p, 18 F e + n 108 m 18 O P.J. Le Blanc, et al., PRC 82 (2010) The leakage from CN to NO reduces of a factor 2: every about 2000 cycles of the main CN cycle, one goes to NO cycle. Before every 1000 cycles was the value recommended by the NACRE compilations (Angulo et al., 1999)

14 25 Mg(p,g) 26 Al Astrophysical motivations E x (kev) J 25 Mg 26Al Q = 6306 kev 25 Mg+p 26 Al 0 26 Al m Al level scheme T ½ = y << galactic time scale b+ E x (kev) Mg g- ray 1.8 MeV e + n 7 s 25 Al 24 Mg (p, e + n 6 s 26 Mg 27 Al 27 Si 26 Mg excess in meteorites Evidence that 26 Al nucleosynthesis is still active (WR stars, SN and NOVAE) Signature of 26 Mg production during the Hydrogen burning (RGB, AGB)

15 E CM (kev) E x (kev) (4 + ) J Novae explosive Burning (T 9 >0.1) AGB or W-R Stars (T 9 ~0.05) 25 Mg(p,g) 26 Al Astrophysical motivations No direct strength resonance data (level structure derived from the single particle transfer reaction: 25 Mg( 3 He,d) 26 Al) LUNA energy window Q Mg+p isomeric state Al m (t 1/2 = 6s) Al 0 (t 1/2 = y) Al b

16 25 Mg(p,g) 26 Al - HPGe spectra E R = 190 kev 75 C Iliadis et al, 1990

17 25 Mg(p,g) 26 Al - HPGe spectra E R = 190 kev 75 C wg [ev] LUNA HPGe wg [ev] LUNA BGO wg [ev] Iliadis et al (9.0 ± 0.7) 10-7 (9.0 ± 0.8) 10-7 (7.4 ± 1.0) 10-7 BR 0 = (75 ± 2) %

18 25 Mg(p,g) 26 Al - BGO spectra E R = 92 kev the lowest ever directly measured resonance strength wg [10-10 ev] LUNA wg [10-10 ev] NACRE ind. Background run E p = 86.5 kev 2.9 ± E x (kev) J Mg+p 26 Al m 26 Al Al level scheme BR 0 = ( ) % The BGO g-ray total sum spectrum on the 92 kev 25 Mg(p,g) 26 Al resonance (E p = 100 kev). 1. The shaded area envinromental background 2. Thin solid line 25 Mg(p,g) 26 Al simulation varying the primaries branchings. 3. Solid red line total yield fit including background and simulation.

19 25 Mg(p,g) 26 Al - Astrophysical consequences 50 MK < T < 140 MK 50 MK < T < 140 MK % larger factor 5 larger About factor 2 larger Straniero, Imbriani, Strieder et al. ApJ 2013 LUNA results fully cover the temperature range of core massive main sequence stars (Wolf-Rayet) as well as the H-burning shell of RGB and AGB stars.

20 25 Mg(p,g) 26 Al - Astrophysical consequences WR stars: N A <sv> total factor 2 > NACRE and Iliadis N A <sv> isomeric factor 5 > NACRE and Iliadis the expected production of 26 Al gs in stellar H- burning zones is lower than previously estimated. This implies a reduction of the estimated contribution of WR stars to the galactic production of 26 Al. Presolar grains originated in AGB stars: the most important conclusion is that the deep AGB extramixing, often invoked to explain the large excess of 26 Al in some O-rich grains, does not appear a suitable solution for 26 Al/ 27 Al> Mg-Al anti-correlation in Globular Clusters stars: the substantial increase of the total reaction rate makes the Globular Cluster self-pollution caused by massive AGB stars a more reliable scenario for the reproduction of the Mg-Al anti-correlation.

21 17 O(p,g) 18 F - Astrophysical motivation Classical Novae nucleosythesis (T= GK): 1. production of light nuclei ( 17 O/ 18 O abundances...); 2. observation of 18 F g-ray signal (annihilation 511 kev).

22 Caciolli et al., submitted to EPJ A 17 O(p,g) 18 F LUNA experiment 100% 90% 80% DC/tot 183/tot 65/tot 489.9/tot 556 kev 767 kev Broad resonaces DC component Total N A <ss>i/n A <sv> tot 70% 60% 50% 40% 30% 529.9/tot Broad res/tot 20% 10% 0% 1.00E E E+09 T [K] LUNA is directly investigating this energy window

23 17 O(p,g) 18 F On and off resonance spectra Off-Resonance On-Resonance New transitions observed on resonance!

24 New Transitions Observed E x (kev) E p = 193 kev 5789 On Resonance Black = Previously Observed Blue = First Observation Off Resonance 200<E<370 E p E x (kev) 17 O+p O+p F 18 F

25 Total reaction Cross section measured between E cm ke Resonance Strength of E p =193 kev resonance measured within an uncertainty of 8%. (~factor 2 higher accuracy). Activation: ωγ193 = (1.67 ± 0.12 ) μev ωγ193= (1.2±0.2)μeV FOX ωγ193= (2.2±0.4)μeV CHAFA Preliminary 17 O(p,g) 18 F Results results LUNA experiment LUNA experiment Newton et al. Hager et al.

26 17 O(p,g) 18 Preliminary F Reaction Results Novae T five-fold reduction in reaction rate uncertainty. D. Scott et al.

27 NeNa CYCLE LUNA 400 kv outlook 13 C 14 N e + n 10 m y y e + n (p, y y 13 N 15 O CN 2 m (p, 12 C 15 N NO 17 O e + n 64 s 17 F 16 O CNO CYCLE (p, (,g 18 F e + n 108 m 18 O 19 F 22 s 21 Ne e + n 21 Na 3 yr 22 Na 22 Ne 20 Ne 23 Na (p, e + n 25 Mg 7 s e + n 25 Al 24 Mg 400 kv 2008 (p, 26Al 6 s 26 Mg 27 Al e + n MgAl CYCLE 27 Si

28 The Luna Collaboration INFN, Laboratori Nazionali del Gran Sasso INFN, Section of Genoa INFN, Section of Milan INFN, Section of Naples INFN, Section of Padua INFN, Section of Roma 1 INFN, Section of Turin INAF, Teramo observatory Ruhr-Universität Bochum, Germany Forschungszentrum Dresden-Rossendorf, Germany Atomki Debrecen, Hungary The University of Edinburgh, UK A. Formicola, M. Junker F. Cavanna, P. Corvisiero, P. Prati A. Guglielmetti (SP), D. Trezzi A. Di Leva, G. Imbriani, E. Roca and F. Terrasi C. Broggini, A. Caciolli, R. De Palo,R.Menegazzo C. Gustavino G. Gervino O. Straniero C. Rolfs, F. Strieder, H. P. Trautvetter M. Anders, D. Bemmerer, Z. Elekes Zs. Fulop, Gy. Gyurky, E. Somorjai,T. Szucs M. Aliotta, T. Davinson, D. A. Scott