Theoretical description of decay chains of SHN

Transcription

1 Intern. Symp. on SHN, Texas A&M Univ., March 31 April 2, 2015 Theoretical description of decay chains of SHN A. Sobiczewski NCBJ Warsaw, GSI Darmstadt, JINR - Dubna 1. Introduction 2. Model of description 2a) decay energy Qα 2b) decay half-life Tα 3. Results and discussion 4. Conclusions A. Sobiczewski, Int. Symp. on SHN, 1

2 1. Introduction Illustration of the quality of a simple theoretical model in description of the α-decay energy Qα and half-lives Tα The recent Dubna results for the decay of the nucleus (16 chains) are used for this Illustration of the quality of a few mass models in description of masses of heaviest nuclei, which are taken to calculate Qα. There is a significant progress in increasing this accuracy Predictions for the not-yet observed element120.. A. Sobiczewski, Int. Symp. on SHN, 2

3 2. Model of description a) Decay energy Qα In description of masses of heaviest nuclei (with measured mass) by various models, one finds (A.S., Yu.A. Litvinov, PRC 89, (2014)): Rms (kev) Model DZ FRDM LSD HFB21 WS3+ WS4+ HN (Nnucl) Z,N Z 82, N Z 100, N N. Wang, M. Liu, PRC 84, (R) (2011) [WS3+, WS3+RBF] N. Wang et al., Phys. Lett. B 734, 215 (2014) [WS4+, WS4+RBF] A. Sobiczewski, Int. Symp. on SHN, 3

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6 2. Model of description b) Decay hallf-life Tα A. Sobiczewski, Int. Symp. on SHN, 6

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8 3. Examples of results 1) Already observed chain for predicted: A.S., Acta Phys. Pol. B 41,157 (2010) observed: Yu.Ts. Oganessian et al., PRL 104, (2010) presently: large statistics: Dubna Av. δqα over 3 decays of , , in the chains are: 280,310,260 kev for WS3+, WS4+, HN, respectively Av, Tth/Texp over 3 decays of , , in the chains are: 2.9, 8.5, 6.3 for WS3+, WS4+, HN, respectively 2) Not observed yet: Tth( )=53 µs, 22 µs, 3 µs for WS3+, WS4+, HN, respectively A. Sobiczewski, Int. Symp. on SHN, 8

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13 Conclusions 1. Quality of a simple theoretical model for the α decay is discussed. 2. The model is tested by the recent Dubna exp. data for the nucleus (16 chains) (for the ncleus , only 3 chains were seen). 3. As the input data to the model, the decay energy obtained with the use of recent mass models, describing masses of heaviest nuclei with a high accuracy (rms ~ 120 kev), is taken. 4. The exp. decay energy Qα is reproduced with the average accuracy of about 250 kev and the half-lives Tα within a factor of Predictions made for the element 120 indicate for a chance of its observatiion 6. As the model describes the exp. decay chains of a number of SHN, being not adjusted to them, the description may be considered as a confirmation of the exp. results, and predictions of the model as a helpful guide for experiment. 7. There is a chance of improving the described model by including the transitions changing the structure of a nucleus, without a significant complication of it. A. Sobiczewski, Int. Symp. on SHN, 13

14 2. Model of description a) Decay energy Qα In description of masses of heaviest nuclei (Z 82, N 126; 36 nuclei with measured mass) by various models, one finds: Model DZ FRDM LSD WS3+ WS4+ HN rms (kev): In description of masses of heaviest nuclei (Z 100, N 126; 36 nuclei with measured mass) by various models, one finds: Model DZ FRDM LSD WS3+ WS4+ HN rms (kev): A. Sobiczewski, Int. Symp. on SHN, 14

15 2. Model of description b) Decay half-life Tα In description of masses of heaviest nuclei (Z 82, N 126; 36 nuclei with measured mass) by various models, one finds: Model DZ FRDM LSD WS3+ WS4+ HN rms (kev): In description of masses of heaviest nuclei (Z 100, N 126; 36 nuclei with measured mass) by various models, one finds: Model DZ FRDM LSD WS3+ WS4+ HN rms (kev): A. Sobiczewski, Int. Symp. on SHN, 15

16 2. Model of description a) Decay energy To calculate them, we look for a possibly realistic mass models, especially for heaviest nuclei: Continuing a big exp. activity in SHN reasearch: Dubna, GSI, Berkeley, RIKEN, On the theor. side: intensive works on possibly realistic models, both macr-micr and purely micr, describing the data The realistic models provide us with an interpretation of the data, guide which helps to understand them. When a realistic model is not directly fitted to the data, its results may be considered as an independeny et confirmation of them. When applied to nuclei not-yet observed its results may be helpful as a guide to experiment. A. Sobiczewski, Int. Symp. on SHN, 16

17 2. State of experiments on the element 117 Dubna 16 chains of isotope and 4 of obtained in reaction 249-Bk + 48-Ca (4n and 3n channels) with σmax = 2.4 and 1.1 pb, respectively. The results are summarized in: Yu.Ts. Oganessian et al., PRC 87, (2013). GSI (TASCA): Two chains of ; J. Khuyagbataar et al., PRL 112, (2014). We concentrate on the description of (16 chains obtained in Dubna). A. Sobiczewski, Int. Symp. on SHN, 17

18 2. Model of description b) Decay hallf-life Tα A. Sobiczewski, Int. Symp. on SHN, 18

19 Care for realistic Qα in the region of SHN: In description of masses of heaviest nuclei (with measured mass) by various models, one finds (A.S., Yu.A. Litvinov, PRC 89, (2014)): Rms (kev) Model DZ FRDM LSD HFB21 WS3+ WS4+ HN (Nnucl) Z,N Z 82, N Z 100, N N. Wang, M. Liu, PRC 84, (R) (2011) [WS3+, WS3+RBF] N. Wang et al., Phys. Lett. B 734, 215 (2014) [WS4+, WS4+RBF] A. Sobiczewski, Int. Symp. on SHN, 19

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29 Conclusions. 1. Intensive studies of SHN are continued. 2. In particular, a rather large number (16) of decay chains of the superheavy nucleus were observed in Dubna (for 118, only 3 chains were seen). 3. A very good description of masses of heaviest nuclei was reached by some mass models (rms ~ 120 kev). 4. Simple phenomenological model describes the chains quite accurately, when using these masses. As the model describes the exp. decay chains of a number of SHN, being not adjusted to them, this may be considered as an additional confirmation of the proper interpretation of the described experimental results. A. Sobiczewski, Int. Symp. on SHN, 29

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49 Conclusions 1. Global m-m models are comparable in their accuracy (ms about 600 kev). Also their predictive power is comparable. The worst is FRLDM. 2. Among purely micr models, last version of Sk-HFB is the best. However, it is comparable with m-m models, while much more complicated and time consuming in the calculations. 3. Present version of RMF is rather bad. One can expect, however, that modification discussed by P. Ring (and being used in going on calculations) will lead to much better results. 4. For heavy nuclei, the rms is smaller and comparable between the m-m and also Sk-HFB21 models. The G-HFB and RMF models are much worse. The semi-empirical model is exceptionally good. However, its predictive power is not so good. 5. When going outside of the exp. region, the models show differences, but not so sudden. This suggests that a continuing interaction between experiment and theory, the models may be reasonably fast developed. In this development, the considerations discussed by J. Dudek may appear to be helpful. A. Sobiczewski, Int. Symp. on SHN, 49