1. China-Japan Symposium at Shanghai, May 16-20, 2006 1 Spin-flip excitations studied by high-resolution (p,p’) scattering experiment at foward angles A. Tamii Research Center for Nuclear Physics, Osaka University

2. China-Japan Symposium at Shanghai, May 16-20, 2006 2 Collaborators RCNP, Osaka University A. Tamii, H. Matsubara, T. Adachi, K. Fujita, H. Hashimoto, K. Hatanaka, K. Nakanishi, Y. Sakemi, Y. Shimizu,Y. Tameshige and M. Yosoi Dep. of Phys., Osaka University Y. Fujita Dep. of Phys., Kyoto University H. Sakaguchi and J. Zenihiro CNS, Univ. of Tokyo T. Kawabata and Y. Sasamoto CYRIC, Tohoku University M. Itoh Dep. of Phys., Kyushu University M. Dozono NSCL, Michigan State Univ. Y. Shimbara Univ. of Gent L.A. Popescu IFIC-CSIC, Valencia B. Rubio and A. Perez Univ. of Witwatersrand J. Carter iThembaLABs H. Fujita and F.D. Smit IKP, Darmstadt P. von Neumann-Cosel, A. Richter, I. Poltoratska, V. Ponomarev and K. Zimmer

3. China-Japan Symposium at Shanghai, May 16-20, 2006 3 Motivation

4. China-Japan Symposium at Shanghai, May 16-20, 2006 4 Motivation 1. Systematic study of M1 strengths and quenching for T=0 and T=1 states M1:0 + → 1 +, ΔL=0, ΔS=0 analogous to Gamow-Teller G.M. Crawley et al.,PRC39(1989)311 2. Fragmentation mechanism of M1 Strengths. 4. Nuclear matrix element of neutrino inelastic scattering (, ’) supernovae, nucleosynthesis 3. New or exotic type excitations in nuclei. vortex type excitations? 48 Ca(p,p’) at IUCF at 0 deg., Y. Fujita et al.

5. China-Japan Symposium at Shanghai, May 16-20, 2006 5 Merits of measuring proton inelastic scattering at 0 deg. d  /d  is maximum at 0°for  L=0 excitations.  L can be identified from the angular distribution of d  /d  at forward angles. d  /d  at 0° is approximately proportional to the relevant reduced matrix elements.  S is model-independently identified by measuring polarization transfer coefficients at 0°(  S decomposition of the strengths) High resolution experiment is feasible. Other reaction data such as (d,d’), ( 3 He, t), and (e,e’) provide complementary information on property of excited states. T.Suzuki, PTP103(2000)859 e.g. E1 e.g. M1

6. China-Japan Symposium at Shanghai, May 16-20, 2006 6 Experiment

7. China-Japan Symposium at Shanghai, May 16-20, 2006 7 RCNP Cyclotron Facility proton beam E p =295 MeV

8. China-Japan Symposium at Shanghai, May 16-20, 2006 8

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10. 10 Spectrometers in the 0-deg. experiment setup Intensity : 3 ~ 8 nA Ion optics: Medium under-focus mode As a beam spot monitor in the vertical direction Feb. 14 2006 defense Transport : Dispersive mode

11. China-Japan Symposium at Shanghai, May 16-20, 2006 11 Beam energy spread was checked by 197 Au(p,p 0 ) elastic scattering in the achromatic transport mode 40-60 keV (FWHM) at E p =295 MeV It corresponds to a beam spot size of ~ 3mm (FWHM) on target in the dispersive transport mode. Halo free beam tuning at 0 deg. (achro. beam) Single turn extraction of the AVF cyclotron Tuning of dispersion matching 20 keV (FWHM) at E p =295 MeV It takes ~2 days for the beam tuning. Beam Tuning Beam spot in the dispersive mode

12. China-Japan Symposium at Shanghai, May 16-20, 2006 12 Targets and Angles 0 ° 2.5 ° 4.5 ° 6 ° 9,12,15,18 °achrom. 0°elasticthickness ( mg/cm 2) nat C ◎ ◎ ◎ ◎ ◎ ◎ ◎ 30 (partly 1.1) mylar ◎ ◎ ◎ － － － － 10 13 CH 2 ○ － － － － － － 0.7 24 Mg ○ － － － － － － 1.8 25 Mg ○ － － － － － － 4.00 26 Mg ◎ ◎ ◎ ◎ － － － 1.55 27 Al ○ － － － － － － 1.8 28 Si ◎ ◎ ◎ ◎ ◎ ◎ ◎ 1.86 (58.5 a part of elastic) 40 Ca ○ － － － － － － 13 48 Ca ◎ ◎ ◎ － － － － 1.9 58 Ni ◎ ◎ ◎ － － － － 4 64 Ni ◎ ◎ ◎ － － － － 4.7 90 Zr △ － － － － － － 1.0 120 Sn △ － － － － － － 2.6 208 Pb △ △ － － － － － 5.2 ○... measured, ◎... good statistics, △... poor statistics, －... not measured

13. China-Japan Symposium at Shanghai, May 16-20, 2006 13 Detailed calibrations have mostly been finished. Calibration of the scattering angle, solid angle.  =0.5-0.8°depending on E x. Calibration for the energy high resolution data.  ~20 keV Background Subtraction worked well Absolute cross section and angular distribution. Analysis

14. China-Japan Symposium at Shanghai, May 16-20, 2006 14 Present Results

15. China-Japan Symposium at Shanghai, May 16-20, 2006 15 Resolution is relatively worse due to the thick target.

16. China-Japan Symposium at Shanghai, May 16-20, 2006 16 Inelastic Scattering from 12 C DWBA calculations using Cohen Kurath W.F. and Franey-Love effective interaction (parameter set at 325 MeV, red line) well reproduce the data without any normalization. DWBA calc. Cohen Kurath Wave Function Franey Love Effective Interaction

17. China-Japan Symposium at Shanghai, May 16-20, 2006 17 Inelastic Scattering from 28 Si at 0 degrees

18. China-Japan Symposium at Shanghai, May 16-20, 2006 18 Present data G.M. Crawley et al, PRC39(1989)311, at Orsay 2000 1500 500 d 2 σ/dωdE [mb/sr/MeV] Excitation energy [MeV] 28

19. China-Japan Symposium at Shanghai, May 16-20, 2006 19 Angular Distribution of IS and IV 1 + excitations From angular distribution, isospin value is identified. ×0.35 ×0.11 Θ cm [deg] ×2.50 ×0.77 Θ cm [deg] Ex = 9.50 MeV ; T=0Ex = 11.45 MeV ; T=1 dσ/dΩ [mb/sr] DWBA, T=1 ; IV DWBA, T=0 ; IS Trans. density : A. Willis et al., PRC 43(1991)5 (by OXBASH in sd shell only ) NN interaction. : Franey and Love, PRC31(1985)488. (325 MeV data) Optical potential : K. Lin, M.Sc. thesis., Simon Fraser U. 1986. DWBA calculation Analyzed by H. Matsubara

20. China-Japan Symposium at Shanghai, May 16-20, 2006 20 Other states identified as 1 + dσ/dΩ [mb/sr] T=1 : IV T=0 : IS Θ CM [deg] 15.94 MeV 13.23 MeV 13.19 MeV 13.04 MeV10.60 MeV 10.73 MeV11.95 MeV 10.90 MeV 12.24 MeV 12.33 MeV 13.32 MeV 14.03 MeV 15.15 MeV 15.50 MeV15.76 MeV dσ/dΩ [mb/sr] Θ CM [deg] 1 +, T=0 states1 +, T=1 states Analyzed by H. Matsubara

21. China-Japan Symposium at Shanghai, May 16-20, 2006 21 Strength distribution shell model calculation: OXBASH + USD interaction

22. China-Japan Symposium at Shanghai, May 16-20, 2006 22 Total sum of the strengths Quenching factor ∑ B(σ) [μ n 2 ] T=0 ; IST=1 ; IV (preliminary) ∑ B(σ) [μ n 2 ] Preliminary Cumulative Sum

23. China-Japan Symposium at Shanghai, May 16-20, 2006 23 W. Steffen et al, NPA404(1983)413; (e,e’) at Darmstadt and Mainz They identified ~19 1 + states though it is very ambiguous.

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27. China-Japan Symposium at Shanghai, May 16-20, 2006 27 Angular distribution of Coulomb E1 (1 - ) excitation is steeper than that of M1 (1 + ). E1 Candidates

28. China-Japan Symposium at Shanghai, May 16-20, 2006 28 Angular distribution of Coulomb E1 (1 - ) excitation is steeper than that of M1 (1 + ). E1 Candidates M1 Candidates

29. China-Japan Symposium at Shanghai, May 16-20, 2006 29 1 + (M1) assignments by (e,e’) E1 Candidates M1 Candidates

30. China-Japan Symposium at Shanghai, May 16-20, 2006 30 48 Ca(p,p’) IUCF at 160 MeV 0 deg. Y. Fujita et al. E p =295 MeV at RCNP E p =160 MeV at IUCF

31. China-Japan Symposium at Shanghai, May 16-20, 2006 31 10,000 hours at Darmstadt W. Mettner et al., NPA473(1987)160. Difference comes from B(  ) and B(M1): orbital contribution Isosopin T of the excited states: T=T 0 and T 0 +1 Excited states other than 1 + in the (p,p’) spectrum

32. China-Japan Symposium at Shanghai, May 16-20, 2006 32 Test measurement of 208 Pb(p,p’) Measurement of 208 Pb(p,p’) reaction including polarization transfer is planned in this year. Natural parity excitations (by Coulomb) and M1 excitations can be decomposed by measuring polarization transfer.

33. China-Japan Symposium at Shanghai, May 16-20, 2006 33 Summary Developing of the experimental technique of high-resolution (p,p’) measurements at forward angles is now close to establishment. It is a very power probe of M1, E1 and other excitations. The data quality is comparable or better than the highest quality data previously obtained. Detailed analysis and extraction of physical quantities is now in progress. The date will be compared with theoretical predictions and the data of other complementary reactions such as EM probes, ( 3 He,t) and beta-decays.

34. China-Japan Symposium at Shanghai, May 16-20, 2006 34 Motivation Gamow-Teller (GT) quenching problem: The observed GT strengths are systematically smaller the sum-rule value. N. Anantaraman et al.,PRL52(1984)1409 G.M. Crawley et al.,PRC39(1989)311 How about M1 strengths? GT sum rule : Common with GT High quality data are required. 1. Systematic study of M1 strengths and their quenching Quenching is observed in T=0,1 M1 strengths in 28 Si. Almost no quenching is observed in 24,26 Mg, 28 Si, 32 S for the sum of T=0 and T=1 strengths. 60 → 90% of the strength is observed in 90 Zr upto E x =50 MeV T. Wakasa et al., PRC55(1997)2909 (p,n) reaction K. Yako et al., PLB615(2005)193 (n,p) reaction G.M. Crawley et al., PRC39(1989)311

35. China-Japan Symposium at Shanghai, May 16-20, 2006 35 2. Mechanism of Fragmentation of M1 Strengths. Many candidates of fragmented M1 strengths in 48 Ca were found. 48 Ca(p,p’) at IUCF at the foot of the prominent 1 + peak at 10.22 MeV. Several small M2 and M1 strengths have been identified from the 48 Ca(e,e’) data at Darmstadt and Mainz W. Steffen NPA404(1983)413. P. von Nuemann-Cosel et al., PRL82(1999)1105. 48 Ca(p,p’) at IUCF at 0 deg. analyzed by Y. Fujita et al.

36. China-Japan Symposium at Shanghai, May 16-20, 2006 36 3. New or exotic type of excitations in nuclei Vortex type excitations in nuclei? → Candidates found by Darmstadt ( ,  ’) group by using Quasi-particle Phonon Model 4. Nuclear matrix element of inelastic scattering → Origin of elements (nucleosynthesis) (  ’) processes in supernovae N. Ryezayeva et al., PRL89(2002)272502

37. China-Japan Symposium at Shanghai, May 16-20, 2006 37 Search for toroidal E1 excitations in 208 Pb Prediction of toroidal E1 excitation in 208 Pb by Quasi-particle Phonon Model (QPM) calculations around 6.5-10.5 MeV. QPM is known to well reproduce the E1 distribution measured by 208 Pb( ,  ). By measuring angular distributions of d  /d  and other observables for Coulomb E1 excitations might provide (indirect) evidence of the toroidal E1 mode excitation. N. Ryezayeva et al., RL89(2002)272502 GDR PDR Toroidal DWBA calc. by P. von Neuman-Cosel et al. using QPM wave function and Love-Franey int.

38. China-Japan Symposium at Shanghai, May 16-20, 2006 38 Reconstruction of scattering angles (sieve-slit analysis) B= +1.0%, X fp = -460 mm, E x =~6 MeV at 0deg  = 0.5 deg,  = 0.15 deg ← a sieve-slit was placed at the entrance of GR Image at the focal plane Reconstructed image

39. China-Japan Symposium at Shanghai, May 16-20, 2006 39 Sieve Slit Calibration (Scattering Angle) Sieve slit data by using 58 Ni(p, p 0 ) reaction at 16° Horizontal scattering angle resolution:  = 0.15 deg Vertical scattering angle resolution depends on the F.P. position  = 0.5 deg at low Ex. 0.8 deg at high Ex. calib. by H. Matsubara

40. China-Japan Symposium at Shanghai, May 16-20, 2006 40 Calibration of the aberation of GR Aberation of the ion optics of GR was calibrated as the energy resolution of discrete peaks becomes better. calib. by H. Matsubara

41. China-Japan Symposium at Shanghai, May 16-20, 2006 41 Background Subtraction Vertical positions projected at the vertical focal plane were calculated. Background subtraction was applied by gating the Y position with true+b.g. and b.g. gates. Linear shape of the background in the Y position spectrum is assumed. The background spectrum seems reasonable.

42. China-Japan Symposium at Shanghai, May 16-20, 2006 42 Systematic study of the unit cross section is required σ T=0,1 : unit cross section for B(σ) B(σ) : spin-flip excitation strength F(q,ω) : kinematical factor q : momentum transfer ω : energy transfer = σ T=0,1 F(q,ω) B(σ) present step 1) To determine the unit cross section by DWBA calculations relying on effective interaction and optical potential. 2) Calibration of the unit cross section against b-decay ft values on the assumption of charge symmetry (only for T=1) 12 C, 26 Mg,... 3) Calibration against electro-magnetic probes: ( ,  ’) and (e,e’) (p,p’) --- B(  ) ⇔ B(M1) --- electro-magnetic probes can be well calibrated?

43. China-Japan Symposium at Shanghai, May 16-20, 2006 43 Systematic study of the unit cross section is required σ T=0,1 : unit cross section for B(σ) B(σ) : spin-flip excitation strength F(q,ω) : kinematical factor q : momentum transfer ω : energy transfer = σ T=0,1 F(q,ω) B(σ) present step should be studied as a next step → Systematic study is to be done 1) To determine the unit cross section by DWBA calculations relying on effective interaction and optical potential. 2) Calibration of the unit cross section against b-decay ft values on the assumption of charge symmetry (only for T=1) 12 C, 26 Mg,... 3) Calibration against electro-magnetic probes: ( ,  ’) and (e,e’) (p,p’) --- B(  ) ⇔ B(M1) --- electro magnetic probes can be well calibrated?

44. China-Japan Symposium at Shanghai, May 16-20, 2006 44 E p =295 MeV at RCNP

45. China-Japan Symposium at Shanghai, May 16-20, 2006 45 E p =160 MeV at IUCF

46. China-Japan Symposium at Shanghai, May 16-20, 2006 46 E p =295 MeV at RCNP E p =160 MeV at IUCF

47. China-Japan Symposium at Shanghai, May 16-20, 2006 47 G.M. Crawley et al, PLB127(1983)322; (p,p’) at Orsay, E p =201 MeV 7 of the states identified by (e,e’) : observed. 11 of them: not observed 8 additional peaks were observed

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51. China-Japan Symposium at Shanghai, May 16-20, 2006 51 J  assignments by ( ,  ’) at Gent, F. Bauwens et al., PRC62(2000)024302

52. China-Japan Symposium at Shanghai, May 16-20, 2006 52 J  assignments by ( ,  ’) at Gent, F. Bauwens et al., PRC62(2000)024302

53. China-Japan Symposium at Shanghai, May 16-20, 2006 53 Prediction of the M1 strengths in 208 Pb with 1p-1h basis 1p-1h excited states of protons  h 9/2 -h 11/2 -1 }  and neutrons  i 11/2 -i 13/2 -1 }  strongly couples to each other due to spin-orbit splittings of p and n orbits are similar orbital angular momentum l’s are similar and yield a lower-lying state at ~ 5.4 MeV with B(M1) ~ 1  N 2 a higher-lying state at ~ 7.5 MeV with B(M1) ~ 50  N 2 in Tamm-Dancoff approximation. see e.g. J.D. Vergados, Phys. Lett. 36B (1971) 12. Bohr and Mottelson, Nuclear Structure vol II (1975)636.

54. China-Japan Symposium at Shanghai, May 16-20, 2006 54 Fragmentation of the M1 strengths in 208 Pb The low-lying strength is considered to be exhausted by a state located at 5.846 MeV. observed by (p,p’) S.I. Hayakawa et al., PRL49(1982)1624, (e,e’), and (d,d’). The higher-lying strength is fragmented into many tiny states by mechanisms: core-polarization or g.s. correlation coupling to 2p-2h states coupling to  -h states meson exchange current Experimentally, only a strength of ~10  N 2 has been observed (until 1988) comparing with theoretical predictions of ~10  N 2. → “Missing M1 strength in 208 Pb” calc. by Lee and Pittel PRC11(1975)607. 1p-1h 1p-1h and 2p-2h

55. China-Japan Symposium at Shanghai, May 16-20, 2006 55 Prediction of the M1 strengths in 208 Pb Many theoretical works have been done for reproducing the observed M1 strengths spreading by the coupling to 2p-2h states:20% of reduction ground state correlation:20% of reduction coupling to  -h states and MEC:20% of reduction If all the meachanisms additively contribute, “the best that be expected from theoretical predictions is 20  N 2 ” I.S. Towner, Phys. Rep 155 (1987) 263.

56. China-Japan Symposium at Shanghai, May 16-20, 2006 56 Search for M1 strengths by experiments Experimentally many reactions have been used to observe the M1 strengths: 208 Pb( ,  ), 208 Pb( ,n), 207 Pb(n,n), 207 Pb(n,  ), 208 Pb(e,e’), and 208 Pb(p,p’) In 1988, R.M. Laszewsky et al. have identified 8.8  N 2 below Sn by a 208 Pb( ,  ) measurement. In total the higher-lying strength became 15.6  N 2 which came closer to the “best” theoretical prediction. Still the search for M1 strengths in 208 Pb is an important job to experimentally determine the M1 strengths and their E x distribution. R.M. Laszewski et al, PRL61(1988)1710