1. Kinematically complete measurement of Coulomb breakup of Borromean halo nuclei at the SAMURAI facility at RIBF Takashi Nakamura Tokyo Institute of Technology INPC 2013, 2-8 June, Firenze, Italy

2. Ca H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K N=8 N=2 Neutron Drip Line – Boundary of Bound Nuclei 2n halo known 2n/4n halo(skin)? 1n-halo known 19 C 24 O Established only up to Z=8 (O) Halo Structures New/Lost Magic Numbers Exotic Unbound Resonances --- Physics at the bound limit Ｎ Z N=16 N=20 22 C 31 Ne 19 B Island of Inversion 37 Mg N. Kobayashi Session D2 14 Be 11 Li

3. 22 C 0d 5/2 1S 1/2 0d 3/2 16 20  Prominent 2n-Halo? Reaction cross section measurement ( ) 1/2 =5.4(9) fm c.f. ~3.5 fm 11 Li K.Tanaka et al., PRL 104, 062701(2010).  N=16 Magicity? “Inclusive” Nuclear and Coulomb breakup at 240 MeV/nucleon  N=16 Magicity, 2n Halo N.Kobayashi et al.,PRC86, 054604 (2012). A.Ozawa et al., PRL 84, 5493 (2000). Z=8 22 C 20 C 19 C A  R (mb)  Heaviest s-wave dominant 2n Halo?

4. 22 C High-Z Target (Pb) 20 C n  = N E1 (E x ) dB(E1) dE x d  CB dE x 9hc 16  3 Cross section = (Photon Number)x  Transition Probability) Invariant Mass Equivalent Photon Method 22 C* Coulomb Breakup  Photon absorption of a fast projectile  ~0.6 C.A. Bertulani, G. Baur, Phys. Rep. 163,299(1988). n

5. E1 Response of halo nuclei ExEx 10~20MeV 1~2MeV dB(E1) dE x 11 Be Direct Breakup Mechanism B(E1) spectrum  Halo Single particle State (S n, l,C 2 S) N.Fukuda et al., PRC70, 054606 (2004),TN et al.,PLB 331,296(1994), Palit et al., PRC68, 034318(2003)  exp(iqr)| rY 1 m | s 1/2  | 2 dB(E1) dE x  exp(iqr)| rY 1 m |  gs  | 2 Z A  C2SC2S Z A Soft E1 excitation 11 Li TN et al. PRL96,252502(2006). GDR  Two neutron Correlation (  12 ) T.Otsuka,M.Ishihara, M.Fukunishi,TN, M.Yokoyama, et al.,PRC49, R2289 (1994)

6. 22 C+Pb  |(2s 1/2 ) 2 ＞ +  |(1d 3/2 ) 2 ＞ +  |(2p 3/2 ) 2 ＞ +  |(1f 7/2 ) 2 ＞ …. Correlated: 62.5%24.2% 4.7% 3.8% S 2n =500keV 22 C: Theoretical Calculation by K.Hagino |(2s 1/2 ) 2 ＞ 100% Non-Correlated: (s only) 1.05b 1.66b  Kinematically Complete Measurement of Coulomb Breakup n 20 C r  12 n N=16

7. RIKEN RI Beam Factory (RIBF) Completed in 2007 New-Generation RI-beam facility SRC: World Largest Cyclotron (K=2500 MeV) Heavy Ion Beams up to 238 U at 345MeV/u (Light Ions up to 440MeV/u) 48 Ca beam at 345 MeV/nucleon typical ~200pnA (250pnA max.) 238 U beam at 345 MeV/nucleon typical ~12pnA (15pnA max.) 2012 2008 2009 2014 SRC ZDS SAMURAI BigRIPS SHARAQ Rare RI RING SCRIT 2013 2007 SLOWRI 2014

8. 22 C 240MeV/nucleon 20 C n n BDC1 BDC2 Pb Target Experimental Setup at SAMURAI: Superconducting Analyzer for MUlti-particle from RAdio Isotope Beam Super Conducting Magnet 3T

9. SAMURAI Superconducting Analyzer for MUlti-particle from RAdio Isotope Beam March 2012

10. 22 C 19 B 17 B 20 C 19 C 23 N 22 N High intense RIBF Beam 22 C: ~15/s (c.f. 10/hour K.Tanaka,PRL2010, RIPS@RIKEN) Gain of ~5000! A/Z EE Particle Identification of RI Beams 22 C+Pb/C  20 C+n+n 19 B+Pb/C  17 B+n+n A/Z 19 B 17 B 20 C 19 B ~100 /s 17 B ~1000 /s 22 C ~15 /s 23 N ~100 /s 48 Ca 150~200pnA (Max 250pnA) A/Z 33.643.83.43.22.8 33.643.83.43.22.8

11. preliminary Counts T. Sugimoto et al., Phys. Lett. B 654, 160 (2007). 14 Be (2 + ) E=68 MeV/nucleon 87(5) keV (1σ) 100 keV (1σ) 14 Be (2 + ) E=213 MeV/nucleon Obtained only in 51min! 14 Be: ~2x10 4 pps Good Resolution as designed ! E rel (MeV) 14 Be+C  12 Be+n+n 14 Be

12. C( 14 Be, 12 Be+2n) Pb( 14 Be, 12 Be+2n) electromagnetic dissociation (sigma_emd = sigma_Pb - 1.8*sigma_C) Preliminary M. Labiche et al., Phys. Rev. Lett. 86, 600 (2001). Pb( 14 Be, 12 Be+2n) 213 MeV/nucleon E rel (MeV) 215 MeV/nucleon 35 MeV/nucleon 14 Be+Pb(C)  12 Be+2n 14 Be

13. Summary Coulomb Breakup – Useful Tool to Probe Halo Structure – single particle state for 1n halo – 2n correlation for 2n halo SAMURAI @ RIBF: Large Acceptance Superconducting Magnet + NEBULA/HI detectors – Powerful facility for kinematically complete measurement of breakup reactions at 100-300 MeV/nucleon Coulomb breakup of 22 C, 19 B, 14 Be: Successfully Done Preliminary Results of Coulomb breakup of 14 Be – Soft E1 peak has been obtained

14. Collaborators Tokyo Institute of Technology: Y.Kondo, T.Nakamura, N.Kobayashi, R.Tanaka, R.Minakata, S.Ogoshi, S.Nishi, D.Kanno, T.Nakashima LPC CAEN: N.A.Orr, J.Gibelin, F.Delaunay, F.M.Marques, N.L.Achouri, S.Leblond Tohoku University : T.Koabayshi, K.Takahashi, K.Muto RIKEN: K.Yoneda, T.Motobayashi,H.Otsu, T.Isobe, H.Baba,H.Sato, Y.Shimizu, J.Lee, P.Doornenbal, S.Takeuchi, N.Inabe, N.Fukuda, D.Kameda, H.Suzuki, H.Takeda, T.Kubo Seoul National University: Y.Satou, S.Kim, J.W.Hwang Kyoto University : T.Murakami, N.Nakatsuka GSI : Y.Togano Univ. of York: A.G.Tuff GANIL: A.Navin Technische Universit¨at Darmstadt: T.Aumann Rikkyo Univeristy: D.Murai Universit´e Paris-Sud, IN2P3-CNRS: M.Vandebrouck SAMURAI Dayone Experiment (May 2012) First experimental campaign for the 3 physics programs 1.Coulomb breakup of 22 C and 19 B (T. Nakamura) 2.Study of unbound states of 22 C, 21 C, 19 B, 18 B (N. A. Orr) 3.Study of unbound nuclei 25 O and 26 O (Y. Kondo)

16. Commissioning in March 2012 Kickoff all the detectors, DAQs for the ( ,n) setup Beam transport to SAMURAI Heavy ion detectors optimization NEBULA calibration –Time-zero with high-energy gamma –Efficiency measurement (inc. 2n cross talk) with 7 Li(p,n) reaction B  scan for rigidity calibration Heavy ion – neutron coincidence measurement – 17 C  16 C+n 17 C  15 B+n – 15 C  14 C+n – 14 Be  12 Be+2n Everything worked perfectly !! Primary Beam: 18 O: 290 MeV/nucleon: 500 pnA

17. SAMURAI Commissioning Experiment 1 n p nat Li ・ Quasi-monoenergetic ・ Single Neutron ・ Cross Section is well known → TOF Resolution, Efficiency p 7 Li(p,n) 7 Be(g.s.+0.43 MeV) 200 MeV & 250 MeV NEBULA SAMURAI Magnet B max =3T, superconducting Obtained as 2ndary beam: ~2x10 5 pps

18. Time of Flight Resolution Threshold level = 6 MeVee θ lab < ±40 mrad Counts TOF(measured) - TOF(calculate) (ns) σ TOF =335(5) ps 7 Li(p,n) 7 Be(g.s.+0.43MeV) 6 Li(p,n) 6 Be (4.4%) 7 Be other excited states + scattered neutrons total Intrinsic Resolution: σ TOF =263(6) ps All effects not related to NEBULA taken into account cf.) ~300 ps (designed value) E n :194MeV

19. Efficiency Counts E n (MeV) 7 Li(p,n) 7 Be(g.s.+0.43MeV) 6 Li(p,n) 6 Be (1.4%) 7 Be other excited states + scattered neutrons total 32.3(4) % ~6% correction for neutron flux loss, etc. Intrinsic Efficiency: 34.7±0.4(stat.)±1.0(syst.)% E th =6 MeVee θ lab < ±40 mrad cf.) 37% Geant4 with INCLXX 40% DEMONS

20. Cross-talk spectrum in 7 Li(p,n) data  12 /   Counts Pulse Height (MeVee) for the 2 nd hit 11 n    12 Scattering at 1 st Wall 22 3 4 3 Cosmic Rays from the back4 Cosmic Rays from the front n    12 Evapolation/ Preequilibrium at 2 nd Wall Cosmic Ray Events can be excluded Almost Cross-talk free  12 /    12 /     Cross talk: mostly excluded Iwamoto et al.,J. KPS, 59, 1753 (2011).

21. SAMURAI Commissioning Experiment 2 ・ 2-neutron event → cross-talk rejection C( 14 Be, 12 Be+n+n) 220 MeV/A NEBULA 14 Be n n 12 Be C Pb SAMURAI Magnet B max =3T, superconducting

22. preliminary Counts T. Sugimoto et al., Phys. Lett. B 654, 160 (2007). 14 Be (2 + ) E=68 MeV/nucleon 87(5) keV (1σ) 100 keV (1σ) 14 Be (2 + ) E=213 MeV/nucleon Obtained only in 51min! 14 Be: ~2x10 4 pps Good Resolution as designed ! E rel (MeV)

23. C( 14 Be, 12 Be+2n) Pb( 14 Be, 12 Be+2n) electromagnetic dissociation (sigma_emd = sigma_Pb - 1.8*sigma_C) Preliminary M. Labiche et al., Phys. Rev. Lett. 86, 600 (2001). Pb( 14 Be, 12 Be+2n) 213 MeV/nucleon E rel (MeV) 215 MeV/nucleon 35 MeV/nucleon

24. Development of Neutron Simulator

25. ✔ Simulator for neutron detector array is Not established for E n ~ 250 MeV neutron → ・ developed new simulator with Geant4 ・ compare with SAMURAI commissioning data 7 Li(p,n) 7 Be(g.s.+0.43 MeV) ✔ Simulation is Needed for Analysis and Development of Neutron Detector ・ response function ・ acceptance ・ efficiency etc. Development of Simulator (E n =200 MeV)

26. Evaluation of neutron Simulators with GEANT4 Compare three physics models for n+plastic scintilator ・ BERT (intranuclear cascade model) ・ INCLXX (intranuclear cascade model) ・ MENATE_R (treat each reaction channel) c.f. Z. Kohley et al., Nucl. Instr. and Meths. A 682, 59 (2012).

27. ・ MENATE_R (treat each reaction channel) MENATE_R(GEANT4): neutron detector simulator (Originally MENATE(FORTRAN))

28. BERT, INCLXX (Geant4 built in class) ・ BERT : Bertini Intranuclear Cascade Model (Bertini: H. W. Bertini) - M. P. Guthrie, R. G. Alsmiller and H. W. Bertini, Nucl. Instr. Meth, 66, 1968, 29. - widely used ・ INCLXX : INCL++ → c++ version of INCL INCL: Liege Intranuclear Cascade Model (Liege: the Belgian city) - developed and validated for recent data - typical users are from the nuclear physics community studying spallation processes Nuclear Instruments and Methods in Physics Research A 491 (2002) 492–506 Model limit ~200 MeV < E n < ~10 GeV (Journal of Physics: Conference Series 119 (2008) 032024)

29. Evaluation of Simulator INCLXX MENATER Experiment BERT Light Output (MeVee) Counts compare three physics models for n+plastic scintilator ・ BERT (intranuclear cascade model) ・ INCLXX (intranuclear cascade model) ・ MENATE_R (treat each reaction channel) Z. Kohley et al., Nucl. Instr. and Meths. A 682, 59 (2012). Area normalized to experiment

30. INCLXX gives best agreement Evaluation of Simulator BERT INCLXX MENATER Light Output Threshold (MeVee) Efficiency(sim.) / Efficiency(exp.) w/o 12 C(n,p) 12 B MENATER compare three physics models for n+plastic scintilator ・ BERT (intranuclear cascade model) ・ INCLXX (intranuclear cascade model) ・ MENATE_R (treat each reaction channel) Z. Kohley et al., Nucl. Instr. and Meths. A 682, 59 (2012). Light Output Threshold (MeVee) Efficiency (%) MENATER BERT INCLXX Experiment

31. Results for the Heavy Ion Fragments

32. Momentum Resolution of the fragment @Commisioning Experiment Use of 10--14 Be, 10-17 C beams with well-defined magnetic rigidity B  : reconstructed from tracking with 4 drift chambers BDC1,BDC2: incoming vector to define the target vertex FDC1: outgoing vector (after the target, before the bending) FDC2: outgoing vector (after the target, after the bending) Scattering Angular Resolution  0.9mrad (rms) B  Resolution  1/1500  5  mass resolution for A=100 B  : by particle tracing using Runge-Kutta Method for the best Position matching, Magnetic Field: calculated by TOSCA

33. Counts Mass number 23 O 22 O 24 O 26 F+C  A O ~10  separation! Clear Particle identification!  High resolving power of the SAMURAI spectrometer Mass identification preliminary 21 22 24 23 Courtesy of Yosuke Kondo

34. Summary SAMURAI  Large Acceptance, Multi-Purpose Spectrometer with Neutron/Heavy ion/proton detectors  A Variety of Opportunities for RI-Beam Science SAMURAI Commissioning March 2012 Successfully Done ! --- Momentum Resolution ~1/1500  5  separation for A=100 --- NEBULA: Large Acceptance Neutron detector array Good neutron detection efficiency 35% for 1n Good timing resolution 263(6)ps Good position resolution ~3cm Good selection of 2n events --- Simulator based on GEANT4+INCLXX developed: Work Well --- 14 Be  2n+ 12 Be : Proved good performance of a whole system Day-One Campaign Experiments: May 2012 Coulomb/nuclear breakup of 22 C/ 19 B, Unbound heavy oxygen isotopes  Successfully Done A variety of Experimental Programs in the near future with TPC, proton detectors, MINOS,  -ray calorimeter (Funded/being Constructed)

35. SAMURAI Construction Team T.Kobayashi a, N.Chiga a, T.Isobe b, Y.Kondo c, T.Kubo b, K.Kusaka b,T.Motobayashi b, T.Nakamura c, J.Ohnishi b, H.Okuno b, H. Otsu b, T.Sako c, H.Sato b, Y.Shimizu b, K.Sekiguchi a, K.Takahashi a,R. Tanaka c, Y.Yoneda b a)Tohoku Univeristy b)RIKEN Nishina Center c)Tokyo Institute of Technology

36. Collaborators Tokyo Institute of Technology: Y.Kondo, T.Nakamura, N.Kobayashi, R.Tanaka, R.Minakata, S.Ogoshi, S.Nishi, D.Kanno, T.Nakashima LPC CAEN: N.A.Orr, J.Gibelin, F.Delaunay, F.M.Marques, N.L.Achouri, S.Leblond Tohoku University : T.Koabayshi, K.Takahashi, K.Muto RIKEN: K.Yoneda, T.Motobayashi,H.Otsu, T.Isobe, H.Baba,H.Sato, Y.Shimizu, J.Lee, P.Doornenbal, S.Takeuchi, N.Inabe, N.Fukuda, D.Kameda, H.Suzuki, H.Takeda, T.Kubo Seoul National University: Y.Satou, S.Kim, J.W.Hwang Kyoto University : T.Murakami, N.Nakatsuka GSI : Y.Togano Univ. of York: A.G.Tuff GANIL: A.Navin Technische Universit¨at Darmstadt: T.Aumann Rikkyo Univeristy: D.Murai Universit´e Paris-Sud, IN2P3-CNRS: M.Vandebrouck SAMURAI Dayone Experiment (May 2012) First experimental campaign for the 3 physics programs 1.Coulomb breakup of 22 C and 19 B (T. Nakamura) 2.Study of unbound states of 22 C, 21 C, 19 B, 18 B (N. A. Orr) 3.Study of unbound nuclei 25 O and 26 O (Y. Kondo)

38. Magnetic Field Calculated from TOSCA Scaling factors: +0.10% for 3T +0.35% for 2.5T +0.45% for 2T Resolution: 0.06% (1/1500) at 3Tesla Deviation 0.1%(1/1000) (which can be corrected) T.Kobayashi et al.

40. Efficiency correction 6.9% (E n = 200 MeV) 6.2% (E n = 250 MeV) ~ 6-7% correction ・ neutron flux loss by materials - Li target - neutron window - air between neutron window and NEBULA ・ scattered neutrons ~3%

41. 26.0(7) mbar/sr @ 200 MeV → 2.7 %

42. Efficiency E n = 200 MeV Threshold level = 6 MeVee θ lab < ±40 mrad Counts E n (MeV) 7 Li(p,n) 7 Be(g.s.+0.43MeV) 6 Li(p,n) 6 Be (4.4%) 7 Be other excited states + scattered neutrons total 32.3(4) % NEBULA's intrinsic efficiency: count right part of energy dist. → 20508 counts full fit procedure → 20191 counts 1.5% difference (FWHM)

43. 1-Neutron Event Pb( 15 C, 14 C+n) β 01 /β 12 Counts fake 2-neutron Crosstalk 2-Neutron Event C( 14 Be, 12 Be+n+n) Inelastic Scattering of 14 Be β 01 /β 12 Counts 2-neutron Crosstalk (+ 2-neutron) 13% 43% (0 MeV < E rel <1 MeV) BG ~1/20 contribution Coulomb Breakup of 15 C:

44. TOF resolution correction

45. DEMONS

46. A. Del Guerra, Nucl. Instr. and Meths. 135, 337 (1976). Cross section (mb) n+C Inelastic== Not elastic

47. A. Del Guerra, Nucl. Instr. and Meths. 135, 337 (1976). DEMONS

48. A. Del Guerra, Nucl. Instr. and Meths. 135, 337 (1976). MENATE_R

49. A. Del Guerra, Nucl. Instr. and Meths. 135, 337 (1976). MENATE_R w/o 12 C(n,p) 12 B

50. A. Del Guerra, Nucl. Instr. and Meths. 135, 337 (1976). G4NEUTRONXS ・ one of built in cross section ・ used in new simulator