Nuclear Physics for Astrophysics with Radioactive Beams

1. Nuclear Physics for Astrophysics with Radioactive Beams Livius Trache Texas A&M University EURISOL Workshop ECT* Trento, Jan. 2006

2. Nuclear Physics for Astrophysics with Radioactive Beams Indirect methods only! = Seek (structure) information to transform in cross sections at astrophysically relevant energies and reaction rates • For charged part radiative capture: (p,g) or (a, g) reactions - ANC • (p and a) transfer reactions: (7Be,8B), (11C,12N), (13N,14O), (6Li,d), … • breakup:8B, 9C, 23Al, 7Be, etc… • charge symmetry – study mirror nucleus (or reaction): ex. (7Li,8Li) for (7Be,8B) • Coulomb dissociation - B(El), Trojan Horse Method • (other) spectroscopic info: Jp, Eres, G • to estimate direct terms: Jp, l, config mixings … variae • resonances (Jp, Eres, G’s) – variae, including resonant elastic scatt. • Need good, reliable data to make credible predictions: • Optical model parameters for elastic, transfer; breakup S-matrices; masses, lifetimes, level densities, GT strength distributions, etc… More stable beam studies & RNB !

3. Radiative proton capture is peripheral e.g. 7Be(p,g)8B

4. DirectRadiativeproton capture M is: Integrate overξ: LowB.E.: Find:

5. Proton Transfer Reactions A B(A+p) p a(b+p) b A+a->B+b

6. ANC’s measured using stable beams in MDM • 9Be+p«10B* [9Be(3He,d)10B;9Be(10B,9Be)10B] • 7Li + n« 8Li[12C(7Li,8Li)13C] • 12C + p« 13N[12C(3He,d)13N] • 12C + n« 13C[13C(12C,13C)12C] • 13C + p« 14N[13C(3He,d)14N;13C(14N,13C)14N] • 14N + p« 15O[14N(3He,d)15O] • 16O+ p«17F*[16O(3He,d)17F] • 20Ne + p« 21Na[20Ne(3He,d)21Na] • 22Ne + n« 23Ne[13C(22Ne,23Ne)12C] beams»10 MeV/u * Test cases

7. ANC’s at TAMU from radioactive beams @ 10-12 MeV/nucleon • 10B(7Be,8B)9Be,14N(7Be,8B)13C [7Li beam » 130 MeV, 7Be beam »84 MeV] • 14N(11C,12N)13C [11B beam » 144 MeV, 11C beam »110 MeV] • 14N(13N,14O)13C [13C beam » 195 MeV, 13N beam »154 MeV] • 14N(17F,18Ne)13C [work at ORNL with TAMU participation]

8. RB in-flight production 1.5 105 pps (p,xn), (p,pxn) reactions in inverse kinematics

9. “dream”?! Better beam! Transfer reactions for ANCs 10B(7Be,8B)9Be14N(7Be,8B)13C Beam spot ~F=4 mm, Dq=1.8 deg, DE/E~1-1.5% • Beam Study Detector: 1 mm Si strip detector • Reaction Telescopes: • 105 mmSistrip detector • 1 mmSidetector

10. Better beams & sd-shell nuclei 17F (10 MeV/n) on melamine; ORNL experiment J. Blackmon et al, PRC 2005

11. Transfer reactions • Conclusions: • Can extract ANC from proton transfer reactions -> (p,g) rates • E/A ~ 10 MeV/nucleon (peripherality) • better beams – reaccelerated OK! • good detection resolution – magn spectrom at 0 deg. • Need good Optical Model Potentials for DWBA! Double folding. • Study n-transfer and use mirror symmetry: • Sp=Sn => ANCp=const*ANCn • Data further needed for: • Various cases: waiting points, breakout reactions … • CNO cycle • hot CNO • rap • rp-process • H & He-burning in general

13. CI Upgrade (overview) • Re-activateK150 (88”) cyclotron • Build ion guides and produce RIBs • Inject RIBs to K500 cyclotron • Project deliverables (DOE language): Use K150 stand-alone and as driver for secondary rare-isotope beams that are accelerated with K500 cyclotron

14. K150 Beam Lines MARS Cave MDM Cave NIMROD Cave Light Ion Guide Heavy Ion Guide

15. Nuclear Astrophysics with upgrade - III Study sd-shell nuclei for rp-process • Rare ion beams in MDM at »10 MeV/u - accelerated beams for transfer reactions around 0o [large cross sections and high sensitivity] • Rare ion beams for resonance studies - elastic scattering for resonances with more beams • Rare ion beams into MARS, MDM – study r-process nuclei masses and lifetimes [(d,p) react] (c/o R.E. Tribble)

16. One-nucleon removal can determine ANC (only!) Momentum distributions → nlj Cross section→ ANC Gamma rays → config mixing Need: Vp-target & Vcore-target and reaction mechanism Calc: F. Carstoiu; Data: see later

17. halo 2s1/2 normal Config mixing One-nucleon removal = spectroscopic tool • Example of momentum distributions – all types! • E. Sauvan et al. – PRC 69, 044503 (2004). • Cocktail beam: 12-15B, 14-18C, 17-21N, 19-23O, 22-25F @ 43-68 MeV/nucleon.

18. Summary of the ANC extracted from 8B breakup with different interactions Data from: F. Negoita et al, Phys Rev C 54, 1787 (1996) B. Blank et al, Nucl Phys A624, 242 (1997) D. Cortina-Gil e a, EuroPhys J. 10A, 49 (2001). R. E. Warner et al. – BAPS 47, 59 (2002). J. Enders e.a., Phys Rev C 67, 064302 (2003) Summary of results: The calculations with 3 different effective nucleon-nucleon interactions are kept and shown: JLM (blue squares), “standard” m=1.5 fm (black points) and Ray (red triangles).

19. JLM S17=17.4±2.1 eVb no weights “standard” S17=19.6±1.2 eVb Ray S17=20.0±1.6 eVb Average all: C2tot = 0.483  0.050 fm-1 S17=18.7±1.9 eVb (all points, no weights) Published: LT et al.- PRC 69, 2004 For comparison: ·     (7Be,8B) proton transfer at 12 MeV/u A. Azhari e.a. – two targets: 10B S17(0) = 18.4  2.5 eVb (PRL ’99) 14N S17(0) = 16.9  1.9 eVb (PRC ’99) Average: Phys Rev C 63, 055803 (2001) S17(0) = 17.3  1.8 eVb ·13C(7Li,8Li)12C at 9 MeV/u (LT e.a., PRC 66, June 2003)) C2tot= 0.455  0.047 fm-1 S17(0) = 17.6  1.7 eVb S17astrophysical factor(ours) New: S17(0) = 18.0  1.9 eVb (G Tabacaru ea, 2004) 8B breakup New average: S17(0) = 18.2  1.8 eVb

20. 22Mg(p,g)23Al reaction • Gamma-ray space-based telescopes to detect current (on-going) nucleosynthesis • Astrophysical g-ray emitters 26Al, 44Ti, … and 22Na • Satellite observed g-rays from 26Al (T1/2=7 ·105 y), 44Ti, etc., but not from 22Na (COMPTEL) • 20Ne(p,g)21Na(p,g)22Mg(b,n)22Na • Depleted by 22Mg(p, g)23Al?! • Dominated by direct and resonant capture to first exc state in 23Al

21. 1/2+ 5/2+ 23Ne 23Al 23Al versus23Ne 24Mg(7Li,8He)23Al • Structure of 23Al poorly known: only 2 states, no Jp • Mirror 23Ne has Jp=5/2+ for g.s. and Jp=1/2+ for 1-st exc state (Ex=1.017 MeV) • NNDC says: Jp=3/2+ ? 23Al halo nucleus; level inversion?! J. Caggiano et al., PRC 65, 025802 (2001) X.Z. Cai et al., Phys Rev C 65, 024610 (2002)

22. 22Mg(p,g)23Al reaction in novae • Calculating the astrophysical S-factor in the 2 spin-parity scenarios, if level inversion occurs, the difference is dramatic (upper figure) • The resulting reaction rate is 30-50 times larger in the T9=0.1-0.3 temperature range for the case of a 2s1/2 configuration for 23Al g.s. • This may explain the absence of 22Na thru the depletion of its 22Mg predecessor in 22Mg(p, g)23Al • Direct (2s1/2 or 1d5/2) and resonant capture to first exc state in 23Al (bottom figure).

23. 23Al breakup experiment Proposed to measure @GANIL: Momentum distributions for 12C(23Al,22Mg) @50 MeV/u Calculated in the two scenarios: nlj=2s1/2 (top) or 1d5/2 (bottom). One-proton-removal cross section is about 2x larger for the 2s1/2 case. Detectg-rays in coincidence with 22Mg to determine the core excitation contributions. Determine Jp from mom distrib Determine Asymptotic Normalization Coefficients for 23Al from cross sections and from there the astrophysical S-factor for proton radiative capture leading to 23Al in O-Ne novae.

24. Conclusions - Breakup Can do proton-breakup for ANC! Need: • E/A ~ 30-100 MeV/nucleon (peripherality and model) • Better data to test models and parameters!!! Can extract ANC from breakup of neutron-rich nuclei, but the way to (n,g) cross sections more complex. Need extra work here.

25. MARS In-flight RB production 24Mg 48A MeV 23Al 40A MeV Purity: 99% Intensity: ~ 4000 pps First time - very pure & intense 23Al Primary beam 24Mg @ 48 MeV/A – K500 Cycl Primary target LN2 cooled H2 gas p=1.6 atm Secondary beam 23Al @ 39.5 MeV/A (p,2n) reaction

26. b decay study of pure RB samples

27. 23Al - coincidence spectrum 5/2+ 7/2+ IAS

28. Tighe ea, LBL 1995 Perajarvi ea, JYFL 2000 22Mg(p,g)23Al 5/2+√ 1/2+ 23Al 0.446(4)s Qec=12240keV Proton br. total=1.1% β+ 0.25% β+ 0.48% 9548 8456 8164 8003 7877 IAS: ft=2140 s +/-5% p 7803IAS 5/2+ 7787 (5,7/2)+ 6985 5/2+ 6575 5/2+ 2905 (3,5/2)+ 2359 1/2+ NO! 20517/2+ 4505/2+ 0 3/2+ 0.38% 22Na Qp=7580 keV 22Na(p,g)23Mg resonances Preliminary results! Y Zhai thesis VE Iacob, et al. 23Mg

29. Conclusions – “other methods” • Useful to have various methods/tools at hand • Medium size facilities useful: • may get things done sooner and cheaper! • Valuable for (hands-on) education of students and postdocs! • Competition is healthy and necessary!

30. 14O + p Resonant Elastic Scattering – thick targets, inverse kinematics Beam quality – crucial (no impurities)! E < 10 MeV/nucleon • Will work on: • a resonant elastic scattering • (a,p) reactions, etc. V. Goldberg, G. Tabacaru e.a. – Texas A&M Univ., PRC 2004

31. Nuclear physics for astrophysics.Summary Indirect methods • transfer reactions (proton or neutron) • 5-10 MeV/nucleon • Better beams (energy resol, emittance) • Magnetic spectrometers at 0° – resolution, large acceptance, raytrace reconstr. • breakup • ~ 30-100 MeV/nucleon • Can neutron breakup be used for (n,g)?! (yes, but need n-nucleus potentials) • Spectroscopic info • Jp, Eres, G, (masses, etc…) – a variety of tools at hand • Resonant elastic scattering: E<10 MeV/nucleon. H2 and He targets. • Better models: structure and reaction theories • Need more checks between indirect methods and direct measurements! • Better models/data to predict OMP, make Glauber calc, spectroscopy… Direct methods: inverse kinematics measurements on windowless gas targets with direct detection of product (magnetic separation). E=0-5 MeV/nucleon. All nucleonic species.