Probing properties of the nuclear force in extreme conditions

Transcription

1 Probing properties of the nuclear force in extreme conditions O. Sorlin (GANIL, Caen, rance) PART 1: Testing the spin-orbit force with a bubble nucleus PART 2: Proton-neutron forces at the drip-line May the force be with you Obi-Wan Kenobi Star Wars ARIS, Tokyo, June 2014

2 Part I: Test of the spin- orbit interac4on by using the doubly- magic bubble nucleus 34 Si 34 Si doubly magic: High 2 + energy, low B(E2), weak ρ(e0) Ibbotson et al. PRL 80 (1998) 2081, Rotaru et al. PRL 109 (2012) Enders et al. PRC 65 (2002) talk S. Grévy

3 Proton density deple4on in 34Si? C2S Proton orbits 1d3/ s1/ d5/2 6 (2s1/2) between 36S and 34Si using (-1p) reaction ρp(r) 36S 36S 20 36S(d,3He)35P Khan et al. PLB 156 (1985) C2S Proton orbits ρp(r) 1d3/2 2s1/2 0.17(3) 1d5/2 5.76(7) 34Si 20 34Si(-1p)33Al Mutschler et al. in prep. 34Si J.P. Ebran DDME2 interaction NSCL/S800 with Gretina Gamma-gated p// of fragments

4 Proton occupancies in 34 Si using (- 1p) reac4on Gamma-ray spectrum at Si (-1p) 33 Al 33 Al 2.5±.4 1/2 +, L=0 L= ±2 1± L=2 L=2 L=0 L=2 p // g.s. 1649, 4037 p // g.s. 1649, 3922 ΣC 2 S(L=2)= 5.76(6) ΣC 2 S(L=0)=0.17 (3) 73±2 33 Al 5/2 +, L=2 So far very small L p =0 knock-out observed -> in agreement with a bubble nucleus

5 ρ(r) $ V s ρ τ (r) = W τ (r) 1 % & r Density dependence The spin- orbit (SO) interac4on +W 2 ρ τ ' τ (r) r ' ( ) s l,s splitting + ½( l + 1) j - l/2 j V ls (r) r Normal nucleus Bubble nucleus (SHE) r Asymmetric splihng of j orbits Isospin dependence W 1 2W 2 (M) W 1 W 2 (RM) No isospin dependence in RM Reduced SO splihng in bubble nucleus for orbits probing the interior of the nucleus such as L=1 Looking at neutron p 3/2 - p 1/2 SO evolu4on when deple4ng the proton central density - > test density and isospin dep. of SO

6 34 Si(d,p) reac4on in inverse kinema4cs at GANIL 34 Si 10 5 pps 20A.MeV GANIL Tracking detectors (CATS) S1 p EXOGAM γ CD 2 target 2.6mg cm - 2 CHIO + plas4c GANIL, IPN Orsay, CEA Saclay IPHC Strasbourg MUST2 EXOGAM Ioniza4on chamber (CHIO) Annular detector (S1)

7 Spin-orbit splittings in 35 Si using 34 Si(d,p) 35 Si S n 1134 E*<1.5 MeV E*>1.5 MeV L assignments from proton angular distributions Accurate energy of states with γ-ray detection G. Burgunder et al., Phys. Rev. Letters 112 (2014)

8 Evolution of the p 3/2 -p 1/2 SO splitting ρ p (r) 40 Ca Z=20 ρ p (r) 36 S 4 protons d 3/2 Z=16 ρ p (r) 34 Si 2 protons s 1/2 Z=14 No change in p 3/2 - p 1/2 splihng between 41 Ca and 37 S Large reduc4on of p 3/2 - p 1/2 splihng between 37 S and 35 Si, no change of f 7/2 - f 5/2

9 Density and Isospin dependence of the SO interac4on Evolution of the p SO splitting as a function of central depletion ΔSO(p)/SO (%) S iso. indep. iso. dep. exp RM DDME2 RM NL3 Determin Preliminary 46 Ar Gogny D1S 34 Si SGII Density dependence Isospin dependence of the SO inter. RM does not have the proper isospin dependence of the SO interaction Consequences for predicting shell gaps formed by the SO interaction in SHE ρ p (r) M. Bender et al. PRC 60 (1999) Δ(2s 1/2 ) 46 Ar: Gaudefroy et al. PRL 99 (2007) 34 Si: Burgunder et al. PRL 112 (2014) r(fm)

10 Part II: Proton-neutron interactions at the drip-line

11 Proton-neutron interactions at the drip-line d 5/2 25 p 24 O n O Σ (2J+1) int(j) V pn (2J+1) J=1,2,3,4 15MeV π d 5/2 ν d 3/2 -> Study of MeV d 3/2 Int(J) (MeV) exp S n Determine the d 5/2 - d 3/2 proton- neutron force in 26 Compare to Shell Model calcula4ons constrained closer to stability Compare to models using realis4c interac4ons 4 experiments to determine the energy of the J=1-4 states! J=1, Mass g.s.: Jurado et al., PLB 649 (2007) J=2, excited state in beam Stanoiu et al. PRC 85 (2012) J=3, unbound state rank et al., PRC 84 (2011) + a new one J=4, M3 isomer Lepailleur et al. PRL 110 (2013) J 24,25 O Hoffman et al. PLB 672(2009), PRL 100(2008)

12 Discovery of a 4 + isomer in 26 <2ms others β- gated Energy Loss Nγ M (1)ms Time of flight Time (ms)

13 Lepailleur et al. Phys. Rev. LeU. 110 (2013)

14 Unbound states in 26 studied at GSI/LAND 40 Ar beam // 27 Ne Dipole magnet ALADIN Gfi 1n 25 LAND TW 1d 3/2 2s 1/2 1d 5/2 Proton Ne neutrons Counts/ 250 kev J=3 + J=2, rom the widths of p // and neutron peak - > Excellent candidate for J=3 + state at 550 kev M. Vandebrouck, preliminary

15 Proton-neutron interaction d 5/2 -d 3/2 in 26 d 5/2 p 24 O n 26 d 3/2 Excellent agreement with coupled cluster calcula4ons (con4nuum not yet implemented) pn interac4on slightly reduced as compared to Shell Model. Shell model Weak change energies of states in con4nuum Centrifugal barrier? it with data into con4nuum? exp (2,3 + ) 3 + Lepailleur et al., PRL 110 (2013) Vandebrouck, preliminary rank et al., PRC 84 (2011) previous Coupled cluster 2 +

16 Conclusions/ Outlooks PART I: 34 Si good candidate for proton bubble, normal neutron density Reduction of neutron p 3/2 -p 1/2 splitting with proton s 1/2 depletion Points to density and isospin dependence of SO interaction PART II: Spectroscopy of bound and unbound states in 26 No drastic change with SM calculations Benchmark for testing realistic forces up to continuum But Atomic mass of 26 to be confirmed. Special thank s to: GANIL/IPNO: G. Burgunder, A. Lepailleur, A. Mutschler, M. Vandebrouck, A. Lemasson The LAND team: T. Aumann, C. Caesar,. Wamers. D. Rossi. The NSCL/S800/Gretina teams: D. Weisshar,. Recchia, D. Bazin, A. Gade, K Wimmer Theory:. Nowacki, T. Otsuka, J. P. Ebran, G. Hagen, G. Jansen, A. Brown