Electromagnetic and Nuclear Breakup in Coulomb Dissociation Experiments

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1 Electromagnetic and Nuclear Breakup in Coulomb Dissociation Experiments Excellence Cluster Universe, Technische Universität, München GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt S246 Collaboration 7th ANL/INT/JINA/MSU Annual FRIB Workshop Interfaces between Nuclear Structure and Reactions August 8-12, 2011 Institute for Nuclear Theory, University of Washington Seattle

2 Outline Coulomb Dissociation Method principle theoretical description and analysis of experiments Example: 6 Li Breakup astrophysical motivation experiment at GSI theoretical 6 Li model reaction theory observables, simulation and cross sections Lithium in big-bang nucleosynthesis Computational Tool Fortran code CDXS+ Conclusions Electromagnetic and Nuclear Breakup

3 Coulomb Dissociation (CD) Method breakup of high-energy projectile a in Coulomb field of highly charged target A a + A b + x + A absorption of (virtual) photons a + γ b + x projectile a target A fragments b x inverse of radiative capture reaction b + x a + γ electric field relation of cross sections Electromagnetic and Nuclear Breakup

4 Coulomb Dissociation (CD) Method breakup of high-energy projectile a in Coulomb field of highly charged target A a + A b + x + A absorption of (virtual) photons a + γ b + x projectile a target A fragments b x inverse of radiative capture reaction b + x a + γ electric field relation of cross sections conditions for application negligible nuclear contribution discrimination of multipolarities ideal case: e.g. 8 B small Q-value, E1 multipolarity dominates Electromagnetic and Nuclear Breakup

5 Coulomb Dissociation (CD) Method breakup of high-energy projectile a in Coulomb field of highly charged target A a + A b + x + A absorption of (virtual) photons a + γ b + x projectile a target A fragments b x inverse of radiative capture reaction b + x a + γ electric field relation of cross sections conditions for application negligible nuclear contribution discrimination of multipolarities ideal case: e.g. 8 B small Q-value, E1 multipolarity dominates here: 6 Li suppression of E1 (isospin selection rule) dominance of E2 (large flux of virtual photons!) contribution of nuclear breakup? Electromagnetic and Nuclear Breakup

6 Coulomb Dissociation (CD) Method theoretical description nuclear structure and reaction theory projectile/fragment system and projectile-target system (very) different energy scales (kinematics) standard: simple potential models; better: more microscopic cluster models, ab initio approaches,... combining structure model with reaction theory phenomenological/realistic interactions, (optical) potentials constraints from experiments simplifictions, approximations, relativistic effects? Electromagnetic and Nuclear Breakup

7 Coulomb Dissociation (CD) Method theoretical description nuclear structure and reaction theory projectile/fragment system and projectile-target system (very) different energy scales (kinematics) standard: simple potential models; better: more microscopic cluster models, ab initio approaches,... combining structure model with reaction theory phenomenological/realistic interactions, (optical) potentials constraints from experiments simplifictions, approximations, relativistic effects? analysis of experiments comparison of theoretical results with experimental data (selected) cross sections with corrections due to experimental resolution, efficiency, cutoffs, etc. full Monte Carlo simulation, analysis of theoretical results just as experimental data sufficient statistics of experiment? Electromagnetic and Nuclear Breakup

8 Observation of Primordial Lithium Cosmic Microwave Background + Big-Bang Nucleosynthesis Prediction of Light Element Abundances Observation of Lithium in old halo stars main contribution: 7 Li ( Spite plateau ) factor 4 less than expected from shoulders of absorption lines: 6 Li (Asplund et al. 2006) 6 Li/ 7 Li ratio larger than expected origin of discrepancy? HD solar 6 Li abundance Asplund et al., ApJ 644 (2006) 229 Electromagnetic and Nuclear Breakup

9 Big-Bang Nucleosynthesis of 6 Li and Cross Section key production mechanism: radiative capture reaction 2 H(α,γ) 6 Li relevant energies: 50 kev < E cm < 400 kev expected cross section: σ(100 kev) 30 pb Electromagnetic and Nuclear Breakup

10 Big-Bang Nucleosynthesis of 6 Li and Cross Section key production mechanism: radiative capture reaction 2 H(α,γ) 6 Li relevant energies: 50 kev < E cm < 400 kev expected cross section: σ(100 kev) 30 pb direct measurement difficult so far only for E cm > 700 kev R.G.H. Robertson et al., Phys. Rev. Lett. 47 (1981) 1867 P. Mohr et al., Phys. Rev. C 50 (1994) 1543 direct low-energy measurement at LUNA! Electromagnetic and Nuclear Breakup

11 Big-Bang Nucleosynthesis of 6 Li and Cross Section key production mechanism: radiative capture reaction 2 H(α,γ) 6 Li relevant energies: 50 kev < E cm < 400 kev expected cross section: σ(100 kev) 30 pb direct measurement difficult so far only for E cm > 700 kev R.G.H. Robertson et al., Phys. Rev. Lett. 47 (1981) 1867 P. Mohr et al., Phys. Rev. C 50 (1994) 1543 direct low-energy measurement at LUNA! alternative: Coulomb dissociation early attempt with 26 A MeV 6 Li beam on Pb target J. Kiener et al., Phys. Rev. C 44 (1991) 2195 almost constant S factor at astrophysical energies, larger than expected from theory new GSI experiment with 150 A MeV 6 Li beam on Pb target F. Hammache et al., Phys. Rev. C 82 (2010) Electromagnetic and Nuclear Breakup

Breakup Experiment at GSI 150 A MeV 6 Li beam from SIS-18, purified by transport through FRS 208 Pb target with 200 mg/cm 2 fragments analyzed with kaon spectrometer KaoS identification of 6 Li, 4 He

12 Breakup Experiment at GSI 150 A MeV 6 Li beam from SIS-18, purified by transport through FRS 208 Pb target with 200 mg/cm 2 fragments analyzed with kaon spectrometer KaoS identification of 6 Li, 4 He and 2 H (problem: similar magnetic rigidity) reconstruction of vertex, full kinematic information Monte-Carlo simulation with GEANT3 comparison with theoretical model calculation (using CDXS+) Electromagnetic and Nuclear Breakup

13 Theoretical 6 Li Model simple α-d potential model low-energy S factor input for breakup calculation Jenny et al. (1983) McIntyre et al. (1966) Gruebler et al. (1975) calculation potentials Woods-Saxon form for central and derivative Woods-Saxon form for spin-orbit interaction adjusted to describe binding energy (E = MeV) of bound state (1 +, s-wave) and position of resonances (3 +, 2 + and 1 +, d-waves) Phaseshifts [deg] E rel [MeV] δ 3 2 δ 2 2 δ 1 2 δ 1 0 δ 2 1 δ 1 1 δ 0 1 Electromagnetic and Nuclear Breakup

14 Theoretical 6 Li Model simple α-d potential model low-energy S factor input for breakup calculation Jenny et al. (1983) McIntyre et al. (1966) Gruebler et al. (1975) calculation potentials Woods-Saxon form for central and derivative Woods-Saxon form for spin-orbit interaction adjusted to describe binding energy (E = MeV) of bound state (1 +, s-wave) and position of resonances (3 +, 2 + and 1 +, d-waves) properties of 3 + resonance at 711 kev Phaseshifts [deg] E rel [MeV] theory experiment Γ α 22.1 kev 24 ± 2 kev Γ γ mev ± mev P. Mohr et al., Phys. Rev. C 50 (1994) 1543 δ 3 2 δ 2 2 δ 1 2 δ 1 0 δ 2 1 δ 1 1 δ 0 1 Electromagnetic and Nuclear Breakup

15 Reaction Theory general (c.m.) differential cross section d 3 σ dω LiPb de αd dω = µ2 p f LiPb αd (2π) 2 4 LiPb 1 p i 2J LiPb i +1 M Li M d T fi 2 µ αdp αd (2π ) 3 distorted-wave Born approximation (DWBA) for T-matrix T fi = χ ( ) ( p f LiPb )Ψ( ) αd ( p αdm d ) (V LiPb U LiPb ) Φ Li (J Li M Li )χ (+) ( p i LiPb ) Electromagnetic and Nuclear Breakup

16 Reaction Theory general (c.m.) differential cross section d 3 σ dω LiPb de αd dω = µ2 p f LiPb αd (2π) 2 4 LiPb 1 p i 2J LiPb i +1 M Li M d T fi 2 µ αdp αd (2π ) 3 distorted-wave Born approximation (DWBA) for T-matrix T fi = χ ( ) ( p f LiPb )Ψ( ) αd ( p αdm d ) (V LiPb U LiPb ) Φ Li (J Li M Li )χ (+) ( p i LiPb ) eikonal approximation for projectile-target scattering wave functions optical potentials for 2 H, 4 He and 6 Li interaction with 208 Pb target no systematic potentials available theoretical double-folding potentials tuned to describe elastic scattering of projectile/fragments on target at energies close to 150 A MeV Electromagnetic and Nuclear Breakup

17 Reaction Theory general (c.m.) differential cross section d 3 σ dω LiPb de αd dω = µ2 p f LiPb αd (2π) 2 4 LiPb 1 p i 2J LiPb i +1 M Li M d T fi 2 µ αdp αd (2π ) 3 distorted-wave Born approximation (DWBA) for T-matrix T fi = χ ( ) ( p f LiPb )Ψ( ) αd ( p αdm d ) (V LiPb U LiPb ) Φ Li (J Li M Li )χ (+) ( p i LiPb ) eikonal approximation for projectile-target scattering wave functions optical potentials for 2 H, 4 He and 6 Li interaction with 208 Pb target no systematic potentials available theoretical double-folding potentials tuned to describe elastic scattering of projectile/fragments on target at energies close to 150 A MeV σ el / σ Rutherford σ el / σ Rutherford σ el / σ Rutherford Pb(d,d) Pb (a) E d = 110 MeV 10-3 E d = 140 MeV Pb(α,α) Pb (b) 10-1 E α = 480 MeV E α = 699 MeV Pb( Li, Li) Pb (c) E 6Li = 600 MeV θ c.m. [deg] Electromagnetic and Nuclear Breakup

18 Observables various angular distributions, e.g. θ 6 scattering angle of excited 6 Li θ 24 opening angle between fragments momentum distributions of particles reconstruction of E rel distribution 6 Li 4 He θ 2 H 6 6 Li * 150 simulation before GEANT3 simulation E rel integrated up to 1.5 MeV CD+Nuclear CD Nuclear dσ/dθ 6 (arbitrary units) θ 6 (deg) Electromagnetic and Nuclear Breakup

19 Observables various angular distributions, e.g. θ 6 scattering angle of excited 6 Li θ 24 opening angle between fragments momentum distributions of particles reconstruction of E rel distribution 6 Li 4 He θ 2 H 6 6 Li * for comparison with experiment: full Monte-Carlo simulation with theoretical event distributions (input for GEANT3 simulation) dσ/dθ 6 (arbitrary units) simulation before GEANT3 simulation E rel integrated up to 1.5 MeV CD+Nuclear CD Nuclear θ 6 (deg) Electromagnetic and Nuclear Breakup

20 Observables various angular distributions, e.g. θ 6 scattering angle of excited 6 Li θ 24 opening angle between fragments momentum distributions of particles reconstruction of E rel distribution 6 Li 4 He θ 2 H 6 6 Li * for comparison with experiment: full Monte-Carlo simulation with theoretical event distributions (input for GEANT3 simulation) clear evidence of interference between Coulomb and nuclear breakup contributions dσ/dθ 6 (arbitrary units) simulation before GEANT3 simulation E rel integrated up to 1.5 MeV CD+Nuclear CD Nuclear θ 6 (deg) Electromagnetic and Nuclear Breakup

21 Experiment and Simulation simulation accounts for resolution and acceptance counts MeV < E (a) rel < 0.5 MeV Experiment Coulomb+Nuclear Coulomb Nuclear pure Coulomb dissociation does not describe data, nuclear contribution needed MeV < E rel < 0.9 MeV (b) counts Experiment Coulomb+Nuclear Coulomb Nuclear counts MeV < E rel < 1.5 MeV (c) counts θ 24 (deg) θ 6 (deg) Electromagnetic and Nuclear Breakup

22 Differential Cross Section and Nuclear Contribution simulation fits measured cross sections well nuclear contribution stronger at low E rel and lower beam energy (Kiener et al. experiment!) Coulomb dissociation cross section cannot be extracted only upper limit for cross section of radiative capture reaction use well tested theoretical model for astrophysical S factor counts Experiment Coulomb+Nuclear E rel (MeV) Ratio Nuclear/Coulomb dissociation A MeV 150 A MeV E rel (MeV) Electromagnetic and Nuclear Breakup

23 Astrophysical S Factor theoretical model describes well direct data at and above 3 + resonance various theories (very different models) predict similar S factors A.M. Mukhmedzhanov et al., Phys. Rev. C 52 (1995) 3483 P. Mohr et al., Phys. Rev. C 50 (1994) 1543 A. Kahrbach et al., Phys. Rev. C 58 (1998) 1066 K.M. Nollet et al., Phys. Rev. C 63 (2001) K. Langanke, Nucl. Phys. A 457 (1986) 351 calculate reaction rate with theoretical S factor S factor (MeV barn) S factor (MeV barn) Kiener et al. Mohr et al. Robertson et al. This work E1 This work E2 This work total This work total Mukhamedzhanov et al. Mohr et al. Kharbach et al. Nollett et al. Langanke et al. 0 0,5 1 1,5 E rel (MeV) Electromagnetic and Nuclear Breakup

24 Big-Bang Nucleosynthesis and the Li Problem 6 Li production: 2 H(α,γ) 6 Li 6 Li destruction: 6 Li(p,α) 3 He with reasonably well known reaction rate Li/H Li 10-2 Ω B h reaction rate of capture reaction with S factor from our theoretical model is consistent with NACRE compilation HD NACRE high 6 Li WMAP NACRE low GSI New η Electromagnetic and Nuclear Breakup

25 Big-Bang Nucleosynthesis and the Li Problem 6 Li production: 2 H(α,γ) 6 Li 6 Li destruction: 6 Li(p,α) 3 He with reasonably well known reaction rate Li/H Li 10-2 Ω B h reaction rate of capture reaction with S factor from our theoretical model is consistent with NACRE compilation observed 6 Li/ 7 Li ratio is 4 % (if observation can be confirmed!) HD NACRE high NACRE low 6 Li GSI New WMAP primordial ratio should be 10 4! problem with astronomical 6 Li observation? η Electromagnetic and Nuclear Breakup

26 Computational Tool Fortran code CDXS+ (latest version 6.48, approx lines, 33 page manual, unpublished, to be updated), main features: Electromagnetic and Nuclear Breakup

27 Computational Tool Fortran code CDXS+ (latest version 6.48, approx lines, 33 page manual, unpublished, to be updated), main features: projectile/fragments system bound and (low-energy) scattering states in simple potential model wave functions, phase shifts, resonance properties,... photo absorption and radiative capture cross sections/s factors (E1, E2, M1) Electromagnetic and Nuclear Breakup

28 Computational Tool Fortran code CDXS+ (latest version 6.48, approx lines, 33 page manual, unpublished, to be updated), main features: projectile/fragments system bound and (low-energy) scattering states in simple potential model wave functions, phase shifts, resonance properties,... photo absorption and radiative capture cross sections/s factors (E1, E2, M1) projectile-target system (high-energy) elastic scattering with optical potentials S-matrix elements, phase shifts, elastic scattering cross section Electromagnetic and Nuclear Breakup

29 Computational Tool Fortran code CDXS+ (latest version 6.48, approx lines, 33 page manual, unpublished, to be updated), main features: projectile/fragments system bound and (low-energy) scattering states in simple potential model wave functions, phase shifts, resonance properties,... photo absorption and radiative capture cross sections/s factors (E1, E2, M1) projectile-target system (high-energy) elastic scattering with optical potentials S-matrix elements, phase shifts, elastic scattering cross section projectile breakup on target electromagnetic and nuclear contributions eikonal DWBA calculation, relativistic and non-relativistic Coulomb excitation various (more or less differential) cross sections in c.m. system Electromagnetic and Nuclear Breakup

30 Computational Tool Fortran code CDXS+ (latest version 6.48, approx lines, 33 page manual, unpublished, to be updated), main features: projectile/fragments system bound and (low-energy) scattering states in simple potential model wave functions, phase shifts, resonance properties,... photo absorption and radiative capture cross sections/s factors (E1, E2, M1) projectile-target system (high-energy) elastic scattering with optical potentials S-matrix elements, phase shifts, elastic scattering cross section projectile breakup on target electromagnetic and nuclear contributions eikonal DWBA calculation, relativistic and non-relativistic Coulomb excitation various (more or less differential) cross sections in c.m. system simulation and analysis conversion of cross sections to event distributions in lab. system (four-momenta of particles) consideration of resolution effects histogram preparation Electromagnetic and Nuclear Breakup

31 Conclusions Coulomb dissociation method theoretical models for structure and reactions at different energy scales phenomenological potentials need to be constrained by experimental data combination of more microscopic structure models with reaction description? Electromagnetic and Nuclear Breakup

32 Conclusions Coulomb dissociation method theoretical models for structure and reactions at different energy scales phenomenological potentials need to be constrained by experimental data combination of more microscopic structure models with reaction description? Comparison of Theoretical Results with Experimental Data conversion of theoretical cross sections to event distributions and analysis as experimental data use many observables, highly-differential cross sections Electromagnetic and Nuclear Breakup

33 Conclusions Coulomb dissociation method theoretical models for structure and reactions at different energy scales phenomenological potentials need to be constrained by experimental data combination of more microscopic structure models with reaction description? Comparison of Theoretical Results with Experimental Data conversion of theoretical cross sections to event distributions and analysis as experimental data use many observables, highly-differential cross sections Example: 6 Li breakup strong nuclear contributions experimental evidence for Coulomb-nuclear interference Coulomb contribution low-energy S factor cannot be extracted unambiguously probably no solution of primordial 6 Li abundance problem by nuclear physics (details: F. Hammache et al., Phys. Rev. C 82 (2010) ) Electromagnetic and Nuclear Breakup

34 S246 Collaboration F. Hammache, O. Sorlin, IPN, IN2P3-CNRS, Orsay, France M. Heil, S. Typel, F. Attallah, H. Geissel, M. Hellström, P. Koczon, E. Schwab, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany K. Schwarz, P. Senger, K. Sümmerer F. Uhlig, D. Galaviz, P. Mohr, Technische Universität, Darmstadt, Germany A. Coc, J. Kiener, V. Tatischeff, J. P. Thibaud, CSNSM, IN2P3-CNRS, Orsay, France D. Cortina, M. Caamano, Universidade Santiago de Compostela, Spain N. Iwasa, Tohoku University, Aoba, Sendai, Miyagi, Japan B. Kohlmeyer, Philipps Universität, Marburg, Germany F. Schümann, Ruhr-Universität, Bochum, Germany E. Vangioni, Institut d Astrophysique des Paris, France W. Walus, Jagiellonian University, Krakow, Poland A. Wagner Forschungszentrum Rossendorf, Dresden, Germany Electromagnetic and Nuclear Breakup

New measurement of the cross section of the Big Bang nucleosynthesis reaction D(α,γ) 6 Li and its astrophysical impact

New measurement of the cross section of the Big Bang nucleosynthesis reaction D(α,γ) 6 Li and its astrophysical impact F. Hammache 1,2, D. Galaviz 3, K. Sümmerer 2, S.Typel 2, F. Uhlig 2, A. Coc 4, F.