Observation of the collinear multi-body decays in the reaction 238 U+ 4 He (40MeV)

1. Observation of the collinear multi-body decays in the reaction 238U+4He (40MeV) Yu. Pyatkov1,2 for HENDES and FOBOS collaborations. 1 Moscow Engineering Physics Institute, Moscow, Russia 2 Joint Institute for Nuclear Research, Dubna, Russia The experiment was performed in JYFL (Jyväskylä, Finland) by the following team: Yu. Pyatkov1, W. Trzaska2, M. Mutterer3, S. Yamaletdinov2, S. Khlebnikov4, Yu. Kopach5, V. Lyapin2, M. Sillanpää 2, V. Tishchenko5, G. Tyurin5 In the data processing took part: A. Tjukavkin5, D. Kamanin5, E. Kuznetsova5, D. Bolgov5. 1. Moscow Engineering Physics Institute, Moscow, Russia 2. Department of Physics of University of Jyväskylä, Finland 3. Technical University, Darmstadt, Germany 4. V.G. Khlopin Radium Institute, St.-Petersburg, Russia 5.Joint Institute for Nuclear Research, Dubna, Russia

2. Introduction 252Cf (sf) ? Ni Ni Ni missing mass Two fragments were detected which fly apart almost collinearly + missing mass is known Ni FOBOS Revealing of the unusual decay channel due to “missing” mass Main goal: to detect all the CCT partners

3. Experiment (JYFL, Finland) 30x30 mm 32 TOF-E channels minimal angel ~ 0.60 target d is lost for simultaneous detection of 2 fragments

4. Experimental setup Total statistics (binary events) ~4*107 Experimental mass resolution (Mte) for one cannel fwhm=2.48 a.m.u. Possible shift between different cannels ~ ± 0.6amu

5. Experimental setup and data processing are presented in : • Yu.Pyatkov, W.Trzaska, M.Mutterer, S.Yamaletdinov, A.Tjukavkin, D.Bolgov, D.Kamanin, S.Khlebnikov, Yu.Kopach, E.Kuznetsova, J.Lavrova, V.Lyapin, M.Sillanpaa, V.Tishchenko, G.Tyurin, • “ Proc. 14th Int. Seminar on Interaction of Neutrons with Nuclei: "Neutron Spectroscopy, Nuclear Structure, Related Topics", Dubna, May 24-27, 2006. Dubna 2007, p. 134-143. • 2. Yu.Pyatkov, W.Trzaska, M.Mutterer, S.Yamaletdinov, A.Tjukavkin, D.Bolgov, D.Kamanin, S.Khlebnikov, Yu.Kopach, E.Kuznetsova, J.Lavrova, V.Lyapin, M.Sillanpaa, V.Tishchenko, G.Tyurin, • “Proc. Int. Symposium On Exotic Nuclei, Khanty-Mansiysk, Russia, 17-22 July 2006, p.144-152”, AIP Press2007

6. Multiplicity 3, preliminary selection of the data W4 Fig.1. Ternary coincident events. Fig.2. Projection of the Ma-Mb distribution shown in fig. 1 onto Ma axis (below thewhite line & Ms<250 amu)

7. Demonstration of experimental mass resolution (Mte)

8. Ternary events with LCP as a partner we have already discussed in: 1. Yu.V. Pyatkov for HENDES and FOBOS collaborations, “Exotic decay modes of 242Pu* from the reaction 238U+4He (40 MeV)”, Proc. VI Int. Conf. no Dynamical Aspects of Nuclear Fission, Smolenice Castle, Slovak Republic, October 2-6, 2006. World Scientifi 2008, p. 248-258. 2. Yu.V. Pyatkov for HENDES and FOBOS collaborations, “Collinear multicluster decays of Pu* isotopes”, 15th International Seminar on Interaction of Neutrons with Nuclei: «Fundamental Interactions & Neutrons, Nuclear Structure, Ultracold Neutrons, Related Topics», Dubna, Russia, May 16-19, 2007 (in press).

9. in each event: Ma> Mb > Mc > Md Reconstruction of the decay scheme 1. Md=242-(Ma+Mb+Mc) 2. Vd=ΔParm / Md 3. Ed=Md*Vd2/2 4. E* =Qs-TKE fragment charge was calculated according Zucd hypothesis missing detected

10. Special case: allthree fragments were detected Momentum conservation law is not met: Ru nucleus undergoes inelastic scattering

11. Three magic clusters in a chain-like configuration in the scission point

12. Presumable scenario of the process Before scission: chain of three magic clusters Clustering of the middle cluster, rupture of a chain-like configuration (binary fission) Inelastic scattering in “start” detectors set free the constituents of each dinuclear molecule

13. Scenario for the events where all conservation laws are met Before scission: chain of three magic clusters Clustering of the middle nucleus, double rupture (sequential fission) which set free the constituents (34Al, 14N) of the middle molecule (48Ca) All the partners of the decay fly apart almost collinearly

14. P1. Pair of magic clusters pair of di-nuclear molecules rupture

15. Presumable scenario of the process Di-nuclear system consisting of two magic clusters In the scission point each “initial” cluster clusterises forming lighter also magic nucleus and nucleus-remainder. Scission results in formation of two long lived “nuclear molecules” (or isomers) Disintegration of such molecule appears to occur via inelastic scattering on the material of the “start” detector.

16. A possible way of decaying of nuclear molecule naive illustration of an inertial effect likely to be decisive for decaying of nuclear molecule

17. 3 * * * A A A C C B B C B Correction of the velocities 2 fragments were formed in the “start” detector but fly in opposite directions 1 2 2 fragments were formed in the target 2 fragments formed in the MCP detector fly in the same direction - no corrections! C Vemis= 66.8 / [56.6/ C Vexp - 5.1(1/ Vb-1/ Va)] B Vemis= 61.6/(56.6/ B Vexp + 5.1/ Vc) * recalculated mass *recalculated mass

18. Conclusion 1.Treating of the ternary events from the reaction 238U+4He (40MeV) proposed is based on the hypothesis that proper i.e. unshifted velocity values were measured. It is hard to believe in manifestation of stable and strong correlations observed due to random coincidences. 2. In the frame of such approach two modes of collinear multibody decay of 242Pu* were revealed. The yield of unusual events (low limit ) is about 10-6/binary fission. Prescission shape of the decaying system looks like a chain consisting of two or three magic clusters respectively. 3. Scission results in formation of long lived “nuclear molecules” (or isomers) based on magic nucleus and light cluster. 4. Disintegration of such molecule appears to occur via inelastic scattering on the target backing or “start” detector. 5. We estimate our results as strong indication of new effect. Bearing in mind principal uncertainties in velocity measurements on HI-beam mentioned above, an improved methods are needed in order to exhaust the problem in forthcoming experiments.