Capture barrier distributions and superheavy elements

Transcription

1 Capture barrier distributions and superheavy elements Kouichi Hagino Tohoku University, Sendai, Japan 1. Introduction: Fusion reactions for SHE 2. Role of deformation in capture reactions 3. Barrier distribution and C.C. analysis 4. Summary International symposium on RI beam physics in the 21st century: 10th anniversary of RIBF Dec. 4-5, RIKEN

2 New element 113: Nihonium 70 Zn Bi 279 Nh* 278 Nh + n November, 2016 Morimoto-san s talk

3 Future directions Superheavy elements synthesized so far Towards Z=119 and 120 isotopes Towards the island of stability the island of stability? Theoretical issues: to understand the reaction dynamics to make a reliable theoretical prediction for fusion cross sections

4 Fusion reactions for SHE T l Coupled-channels Quasi-fission Langevin equation P CN CN W suv ER n fusionfission Statistical model

5 Fusion reactions for SHE T l Quasi-fission P CN CN indistinguishable W suv ER n fusionfission no data for P CN

6 no experimental data for P CN P CN? large uncertainties W suv challenges : reduction of theoretical uncertainties a good understanding of the reaction dynamics

7 Hot fusion for Z = 119 and 120 Towards Z=119 and 120 isotopes (Pb based) cold fusion (Ca based) hot fusion hot fusion: 48 Ca + actinide targets Dubna: 48 Ca Cf (β 2 = 0.235) 297-x Og (Z=118) + xn role of deformation?

8 Role of deformation in capture cross sections T l Sub-barrier enhancement of capture cross sections deformation

9 Role of deformation in capture cross sections Sub-barrier enhancement of capture cross sections K.H., N. Takigawa, PTP128 ( 12) 1061 θ 154 Sm 16 O

10 Fusion barrier distribution (Rowley, Satchler, Stelson, PLB254( 91)) V b Data: J.R. Leigh et al., PRC52 ( 95) 3151 a nice tool to understand the reaction dynamics K.H., N. Takigawa, PTP128 ( 12) 1061

11 Measurements of barrier distributions with GARIS T. Tanaka, Y. Narikiyo, K. Morita, K. Fujita, D. Kaji, K. Morimoto,..., K.H., J. of Phys. Soc. Japan (JPSJ), in press. Quasi-elastic barrier distribution fusion quasi-elastic a sum of elastic, inelastic, and transfer K.H. and N. Rowley, PRC69 ( 04)

12 Measurements of barrier distributions with GARIS K.H. and N. Rowley, PRC69 ( 04) T. Tanaka et al., K.H., JPSJ, in press.

13 Analysis for a hot fusion reaction 48 Ca Cm K.H. and T. Tanaka (2017) (T. Tanaka et al., K.H., JPSJ in press) 48 Ca Cm (β 2 = 0.297, β 4 = 0.04) Lv * [β 2 and β 4 from P. Moller]

14 Analysis for a hot fusion reaction 48 Ca Cm 48 Ca Cm (β 2 = 0.297, β 4 = 0.04) Lv * K.H. and T. Tanaka (2017) single-channel calculation (spherical 248 Cm)

15 Analysis for a hot fusion reaction 48 Ca Cm 48 Ca Cm (β 2 = 0.297, β 4 = 0.04) Lv * K.H. and T. Tanaka (2017) θ 248 Cm 48 Ca

16 Analysis for a hot fusion reaction 48 Ca Cm 48 Ca Cm (β 2 = 0.297, β 4 = 0.04) Lv * K.H. and T. Tanaka (2017) MeV Ca

17 Analysis for a hot fusion reaction 48 Ca Cm 48 Ca Cm (β 2 = 0.297, β 4 = 0.04) Lv * K.H. and T. Tanaka (2017) 1n transfer 48 Ca Cm 49 Ca Cm (Q gg = MeV)

18 Connection to the ER cross sections T l barrier distribution Quasi-fission P CN CN W suv ER n fusionfission

19 Connection to the ER cross sections 48 Ca Cm Lv *

20 Connection to the ER cross sections 48 Ca Cm Lv *

21 Connection to the ER cross sections notion of compactness: D.J. Hinde et al., PRL74 ( 95) 1295 CN re-sepa -ration = more compact at the touching lower barrier height

22 Connection to the ER cross sections notion of compactness: D.J. Hinde et al., PRL74 ( 95) 1295 CN = more compact at the touching lower barrier height

23 Connection to the ER cross sections the initial (injection) point of a Langevin calculation: s inj (θ) CN Y. Aritomo, K.H., K. Nishio, S. Chiba, PRC85 ( 12)

24 role of orientation angle in ER cross sections Fusion-by-diffusion model (Swiatecki) + deformation K.H., in preparation

25 Towards the island of stability neutron-rich beams: indispensable how to deal with low beam intensity? reaction dynamics of neutron-rich beams? capture: role of breakup and (multi-neutron) transfer? diffusion: neutron emission during a shape evolution? survival: validity of the statistical model? structure of exotic nuclei more studies are required

26 Summary Reaction dynamics for SHE formation reactions Recent measurement of barrier distributions with GARIS 48 Ca Cm coupled-channels analysis notion of compactness: ER formation with side collisions more data coming soon Open problems 48 Ca projectile 50 22Ti, 51 23V, 54 24Cr projectiles etc. how much cross sections will be altered? shape evolution with a deformed target? how does the deformation disappear during heat-up? cf. Nakatsukasa-san s conjecture? reaction dynamics with neutron-rich nuclei?

27 formation of SHE chemistry of SHE the origin of (S)HE reaction dynamics Nuclear Physics (RIBF) Astrophysics sessions in this morning structure of SHE Haba-san s talk interdisciplinary SHE science with physics, chemistry, and astronomy

28

29

30

31 Recent application to SHE : Quasi-elastic B.D. hot fusion reactions 48 Ca + actinide nucleus SHE = deformation fusion quasi-elastic Quasi-elastic barrier distribution reaction dynamics with barrier distributions? Quasi-elastic scattering : reflected flux at the barrier a sum of elastic, inelastic, and transfer easier to measure than capture H. Timmers et al., NPA584( 95)190 K.H. and N. Rowley, PRC69( 04)054610

32 previous attempts 86 Kr+ 208 Pb S.S. Ntshangase et al., PLB651 ( 07) 27 S. Mitsuoka et al., PRL99 ( 07) T. Tanaka et al., JPSJ, submitted ( 17)

33 fusion-by-diffusion model W.J. Swiatecki, K. Siwek-Wilczynska, and J. Wilczynski, PRC71 ( 05)

34 fusion-by-diffusion model 51 V proj.??? W.J. Swiatecki, K. Siwek-Wilczynska, and J. Wilczynski, PRC71 ( 05)

35 Super-heavy nuclei coupled-channels method Langevin approach V.I. Zagrebaev and W. Greiner, NPA944( 15)257 statistical model 10 Evap. resid. cross section (pb) E c.m. (MeV)