Spectroscopic Factors of Ar isotopes from transfer and knock-out reactions

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1 Spectroscopic Factors of Ar isotopes from transfer and knock-out reactions Betty Tsang ECT workshop: Reactions and Nucleon Properties in Rare Isotopes April 6-10, 2010, Trento, Italy Survey: Extractions of Neutron Spectroscopic Factors using systematic approach from Transfer Reactions Experiment: 34,46 Ar(p,d) Transfer Reactions in Inverse Kinematics Comparisons to knockout results Asymmetry Dependence of Neutron Correlations

2 Questions about spectroscopic factor measurements Is there a clear understanding of the uncertainties (both data and theory)? Are there disagreements in the structure obtained using different reaction probes? How would one get absolute SFs from transfer or is this not possible? Are there specific experiments or theoretical developments that would move us forward?

3 Spectroscopic Factor from experiments Three main experimental techniques SF(expt) p (e,e p) Theory description is clear (plane-wave impulse approximation) x Only stable nuclei, only proton SF e - (d,p) Transfer reaction Stable & exotic nuclei Particle- & hole-state High & low energy Long history (>50 years) x Beam intensity (>10 4 pps) Knockout reaction Exotic nuclei Very low beam intensity (~ 10 2 pps) High energy (>50MeV/A) x So far only hole-state

4 SF s Reduction and Asymmetry Dependence J. Lee et al., PRC73, (2006) 30-40% ΔS = Sn-Sp for n-sf ΔS = Sp-Sn for p-sf (e,e p) -- nuclei near closed shell Constant ~30-50% of SF reduction compared to IPM L. Lapikas, Nucl. Phys. A553, 297c (1993) One-nucleon knockout -- away from stability Measured SF relative to LB-SM strongly depends on the asymmetry A. Gade et al, PC 77, (2008) More reduction experienced by strongly bound valence nucleon How about Transfer Reactions?

5 Experimental SFs from transfer reactions B B-1 Example: 1f 7/2 n SF in 41 Ca = 40 Ca+n Spectroscopic factor (SF) reflects the properties of valence neutron independent of incident energy SF(SM)=1.0 Need systematic approach consistent SFs Past SF analysis are (mis)guided by shell-model! J. Lee et al., PRC75, (2007)

6 Systematic methods for consistent spectroscopic factors dσ dω EXP = SF EXP dσ dω Theo J. Lee et al., PRC75, (2007) Johnson- Soper Adiabatic Distorted Wave (AWD)to take care of d-break-up effects Use global p and n optical potential with standardized parameters (CH89) Include finite range & nonlocality corrections n-potential : Woods-Saxon shape r o =1.25 & a o =0.65 fm; depth adjusted to reproduce experimental binding energy. Compute with TWOFNR code Johnson & Soper, PRC1,976(1970) TWOFNR from Jeff Tostevin (University of Surrey)

7 Quality Control of extracted SFs 80 g.s. SFs for Li to Cr (~ 430 (p,d) and (d,p) angular distributions) B(p,d)A : SF + ; A(d,p)B : SF - J. Lee et al, Phys. Rev. C75 (2007) Ground-state to ground-state transition SF + = SF - (Detailed balance) 18 nuclei have both SF + and SF - -- SF + = SF - Systematic method works -- 20% uncertainty for each measurement Associated uncertainty Standard deviations

8 Comparisons of (e,e p) and (p,d)&(d,p) transfer reactions L. Lapikas, Nucl. Phys. A553, 297c (1993) J. Lee et al., PRC75, (2007) (e,e p) -- nuclei near closed shell Constant ~30-40% of SF reduction compared to IPM Pure single-particle state Beyond IPM

9 Comparisons to IPM M.B. Tsang and J. Lee et al., PRL 95, (2005) Independent Particle Model (IPM) n, l j Magic number N=20 N=8 N=2 H = i 2 pi + U 2m ( r ) mean field created by nucleons from core i Pure single-particle state IPM needs refinement?

10 Survey of Neutron Spectroscopic Factors and Asymmetry Dependence of Neutron Correlations 1f, 2p N=3 1d, 2s N=2 1p N=1 1s, N=0 core correlated motions of valence nucleons Correlations between nucleons Mixing of particle-hole configuration near the fermi surface Weakening of single-particle strengths SF < LB SM SF IPM How good the interaction in LB-SM can describe the nucleus? Large Basis Shell Model (LB-SM) H = 2 p i 2m + U ( r i) + V NN ( r i r j ) U r i i Mean field i< j ( ) Residual interactions i LB-SM description is accurate Some correlations missing in the interactions?

11 Ground-state Spectroscopic Factors of Z=3-24 IPM + Maximal pairing LB-SM predictions (Residual interactions) 20% agreement Most extracted SFs less than IPMplus-pairing predictions Absence of nucleon-nucleon correlations M.B. Tsang and J. Lee et al., PRL 95, (2005) LB-SM code : Oxbash, Alex Brown (MSU)

12 Predictive power of transfer reaction cross sections M.B. Tsang and J. Lee et al., PRL 95, (2005) Ni isotopes - Ground states CH89 approach in ADWA model Ground state ~SF(LB-SM) from good interactions in Hilbert spaces USDA/USDB Excited states GXPF1A Excited states

13 Suppression of Spectroscopic Factors in Transfer Reactions Jeff Tostevin J. Lee, J.A. Tostevin et al., PRC 73, (2006) Global CH89 + ro=1.25 fm with minimum assumption consistent SF with LB-SM Predictive power for experimental x-sections & Astrophysics rates! ~SF(LB-SM) from good interactions in Hilbert spaces CH89 approach in ADWA model JLM optical potential + bound n- radii constrained with HF geometry Overall ~30% reduction in SFs r o =1.25 fm HF rms radius Global CH89 microscopic nucleon-nucleon JLM + HF densities

14 Neutron transfer reactions for neutron rich and proton rich Ar isotopes n-rich p-rich 46 Ar p( 34 Ar,d) 33 Ar p( 46 Ar,d) 45 Ar Inverse kinematics at 33MeV/u 34 Ar NSCL Expt (Oct 19-30, 2007) Thesis (2010) Jenny Lee

15 L-matching desirable but not necessary L Q R = K in -K out R Condition is well-matched transferred momentum is bound by the condition to ~ ±1 nucleon-transfer probability to that particular state would be relative large J. Lee, NSCL Thesis (2010) contributions from other reaction channels are negligible A-1 A simple one-step DWBA description to the data is valid

16 Asymmetry dependence of neutron correlations Transfer Reactions 34,36,46 Ar + p d + 33,35,45 Ar Inverse kinematics at 33MeV/A Goal: neutron spectroscopic factors Observables: deuteron differential cross sections deuteron MCP's 34,36,46 Ar Beam Primary Devices θ (CH 2 ) n Target Φ To S800 Spectrograph 33,35,45 Ar P,E,Φ 1. High Resolution Array 2. S800 Spectrograph 3. Micro-Channel Plates Complete kinematics measurement First transfer reaction experiment using HiRA with S800 + MCP at NSCL

17 Experimental Setup Focal Plane Target Chamber S800

18 High Resolution Array (HiRA) t d p 16 HiRA telescopes efficiency ~40% 1.5mm Si t d p 65μm Si CsI(Tl) 1024 pixels (2mm x2mm) 0.16 at 35 cm setup Energy resolution: DE ~50 kev; EF ~ 70keV

19 Experimental results Kinematics & Q-value (A+p B+d+Q) p( 34 Ar,d) 33 Ar p( 36 Ar,d) 35 Ar p( 46 Ar,d) 45 Ar θ lab (deg) θ lab (deg) θ lab (deg) p( p( Ar,d) Ar g.s. 500 kev FWHM p( 36 Ar,d) 35 Ar g.s. 470 kev FWHM (θ lab <19 ) p( 46 Ar,d) 45 Ar g.s. 410 kev FWHM The observed resolutions are reproduced by GEANT4 simulations (finite beam spot, energy + angular straggling, detector resolutions) J. Lee et al., PRL104, (2010).

20 J. Lee et al., PRL104, (2010).

21 Summary III: Asymmetry dependence of neutron correlations Transfer SF s depend less strongly on the neutron-proton asymmetry than do those measured in knockout reactions. J. Lee et al., PRL104, (2010).

22 Summary I: Predictive power of transfer reaction cross-sections Ground states MB. Tsang et al., PRL 95, (2005) J. Lee, et al., PRC 75, (2007) J.Lee, et al.,. Rev. C79, (2009) sd shell M.B. Tsang, et al., PRL. 102, (2009). Results indicate that dσ ( ) dω dσ dω Exp = SFLB SM ( ) ADWA Important for astrophysical applications Systematics can be used to test SM interactions & spin assignments confirmations. fp shell M.B. Tsang, et al., PRL. 102, (2009).

23 Summary II: SF s depends on choice of OMP and bound state geometry J. Lee et al., NSCL Thesis (2010) c c J. Lee, J.A. Tostevin et al., PRC 73, (2006)

24 Are there specific experiments or theoretical developments that would move us forward? J. Lee et al., Phys. Rev. Lett. 104, (2010). p( 34 Ar,d) 33 Ar & p( 46 Ar,d) 45 Ar at 33MeV/A Charity: Application of the DOM to (p,d) and (d,p) reactions. HiRA Perform 34Ar(p,d) at E/A=70 MeV; 32Ar? Theory development: Ron Johnston & others

25 Acknowledgements Jenny Lee ( 李曉菁 ) HiRA group: Andy Rogers, Vladimir Henzl, Daniela Henzlova, Daniel Coupland; Micha Kilburn, Alisher Sanetullaev, Mike Youngs, Sun Zhiyu ( ) Betty Tsang ( 曾敏兒 ); Bill Lynch ( 連致標 ) HiRA Collaborators: Lee Sobotka, Bob Charity, Jon Elson (WU in St. Louis) Sylvie Hudan (Indiana University) Mike Famiano (Western Michigan University) Dan Shapira (ORNL) Jolie Cizewski, Bill Peters, Patrick O'Malley (Rutgers University) Kate Jones, Kyle Schmitt, Andy Chae (University of Tennesee) Hoi Kit Cheung ( 張凱傑 ) (Chinese University of Hong Kong) Theory & SF survey Collaborators: Alex Brown, Angelo Signoracci, Hang Liu ( 刘航 ), Scott Warrant (NSCL) Jeff Tostevin (University of Surrey) Mihai Horoi (Central Michigan University) Ming-chung Chu( 朱明中 ), Shi Chun Su( 蘇士俊 ), Jiayan Dai( 戴家琰 ) (Chinese University of Hong Kong)