Light nucleus clustering in fragmentation above 1 A GeV

1. Light nucleus clustering in fragmentation above 1 A GeV N. P. Andreevaa, D. A. Artemenkovb,V. Bradnovab, M. M. Chernyavskyc, A. Sh. Gaitinova, S. P. Kharlamovc, A. D. Kovalenkob, М. Haiducd, S. G. Gerasimovc, L. A. Goncharovac, V. G. Larionovac, F. G. Lepekhine, A. I. Malakhovb, A. A. Moiseenkof, G. I. Orlovac, N. G. Peresadkoc, N. G. Polukhinac, P. A. Rukoyatkinb, V. V. Rusakovab, V. R. Sarkisyanf, T. V. Schedrinab, B. B. Simonove, E. Stane, R. Stanoevag, I. Tsakovg, S. Vokalh, P. I. Zarubinb, I.G Zarubinab aInsitutute of Physics and Technology, Almaty, Kazakhstan bJoint Institute for Nuclear Research, Dubna, Russia cP. N. Lebedev Physical Institute, RAS, Moscow, Russia dInstitute of Space Sciences, Bucharest-Magurele, Romania ePetersburg Institute of Nuclear Physics, RAS, Gatchina, Russia fErevan Physical Institute, Erevan, Armenia gInsttitute for Nuclear Research and Nuclear Energy, BAS, Sofia, Bulgaria hP. J. Safarik University, Kosice, Slovakia

2. 4.5A GeV/c 28Si Dissociation into charge state 2+2+2+2+2+2+1 (narrow cone) with pair of 8Be and triple 12C* like fragments

3. Clustering building blocks:more than one nucleon bound, stable & no exited states below particle decay thresholds – deuteron, triton, 4He, and 3He nuclei

4. =0.092 MeV A=6

5. Advantages of relativistic fragmentation 1. a limiting fragmentation regime is set in, 2. the reaction takes shortest time, 3. fragmentation collimated in a narrow cone – 3D images, 4. ionization losses of the reaction products are minimum, 5. detection threshold is close to zero.

6. 4.5 A GeV/c 16O Coherent Dissociation (PAVICOM image)

7. 4.5A GeV/c 16O Coherent Dissociation with 8Be like fragmentation The reliable observation of charged relativistic fragments is a motivation to apply emulsion technique (0.5 micron resolution). Requirements of conservation of the electric charge and mass number of a projectile fragments are employed in the analysis. Measurements of multiple scattering angles make it possible to estimate the total momentum of hydrogen and helium projectile fragments and thereby to determine their mass.

8. 4.5A GeV/c 20Ne Peripheral Dissociation into charge state 2+2+2+2+2 with 8Be like fragments

9. 4.5A GeV/c 24Mg Peripheral Dissociation into charge state 2+2+2+2+2+2 with 8Be and 12C* like fragments

10. The common topological feature for fragmentation of the Ne, Mg, and Si nuclei consists in a suppression of binary splitting to fragments with charges larger than 2. The growth of the fragmentation degree is revealed in an increase of the multiplicity of singly and doubly charged fragments up to complete dissociation with increasing of excitation. This circumstance shows in an obvious way on a domination of the multiple cluster states having high density over the binary states having lower energy thresholds.

11. Mg-Si Dissociation into charge state 2+2+2+2+2+1 5 +proton

12. dN/dTn 4.5A GeV/c12C:<T3>=0.4 MeV 22Ne5 24Mg5 +3He 0 1.6 2.4 0.8 Tn=(M*n - n M )/(4 n), MeV

13. Deuteron-Alpha Clustering in Light Nuclei 50V(0.25%) 14N(99.634%) 10B(19.9%) 6Li(7.5%) d

14. 4.5A GeV/c 6Li Coherent Dissociation (PAVICOM image) +

15. 1A GeV 10B Coherent Dissociation Into 2+2+1 In 65% of such peripheral interactions the 10B nucleus is disintegrated to two double charged and a one single-charged particles. A single-charged particle is the deuteron in 40% of these events and (2He+d)/(2He+p) 1 like in case of 6Li.

16. 1.3A GeV 9Be dissociation in 2+2. 10B9Be, Nuclotron, 2004. “white” star with recoil proton with heavy fragment of target nucleus

17. 56 events Invariant excitation energy for 1.3 A GeV9Be24He

18. 14N Dissociation with 8Be like fragmentation proton 3 after

19. 2.9A GeV/c 14N Dissociation E*, MeV Invariant excitation energy for 9Be24He

20. Triton-Alpha Clustering in Light Nuclei 7Li 11B 7Li clustering.About 7% of all inelastic interactions of 7Li nuclei are peripheral interactions (80 events), which contain only the charged fragments of a relativistic nucleus. Half of these events are attributed to a decay of 7Li nucleus to -particle and a triton(40 events). The number of decays accompanied by deuterons makes up 30%, and by protons – 20%. The isotopic composition points to the fact that these events are related to the dissociating structure of -particle and the triton clusters. 11B clustering. Analysis is in progress now.

21. Secondary beams of light radioactive nuclei will be produced mostly via charge exchange reactions. 8B and 9Be beams has been formed via fragmentation reaction of 10B.

22. 1.2A GeV 7Be dissociation in emulsion. Upper photo: splitting to two He fragments with production of two target-nucleus fragments. Below: “white” stars with splitting to 2 He, 1 He and 2 H, 1 Li and 1 H, and 4H fragments.

23. Relativistic 7Be fragmentation: 2+2 The 7Вe*3He decay is occured in 22 “white stars” with 2+2 topology. In the latter, 5 “white” stars are identified as the 7Вe*(n) 3He3He decay. Thus, a 3He clustering is clearly demonstrated in dissociation of the 7Be nucleus.

24. Toward stability frontier =1.58 MeV 11N =0.23 MeV 8C =1.4 MeV 7B =0.092 MeV 6Be =1.5 MeV 5Li

25. 1A GeV 10B Fragmentation to 8B (PAVICOM image)

26. “Triple H&He Process: mixed isotope fusion” One more path to 12C and 4He production Toward CNO cycle&  burning 12C 98.89 % 8B 0.769 s 12N 11.0 ms + The 10B nuclei with a momentum of 2.0 GeV/c per nucleon and an intensity of about 108 nuclei per cycle were accelerated at the JINR nuclotron and a beam of secondary nuclei of a magnetic rigidity corresponding to Z/A = 5/8 (10В8B fragmentation) was formed. Information on the 8B interactions in emulsion had been obtained. We plan to determine the probabilities of forming “white” stars in 8B7Bер, 3Hep, 6Lipp, and dpp. In the 8В7В fragmentation, a crossing of the limits of proton stability also takes place. Thus, there arises a possibility of studying the decay channels 7B p3He3He (an analog to 9B) and ppp4He.

27. “Triple He Process: pure isotope fusion” The fusion 3He3He3He6Be3He9С is one more option of the “3He process”. In the 9С8C fragmentation, a crossing of the boundary of proton stability takes place. In this case, there arises a possibility in studying nuclear resonances by means of multiple 8C pppp4He and 8C pp3He3He decay channels, which possess a striking signature. It is quite possible that the study of these resonances would promote further development of the physics of loosely bound nuclear systems. 12C nuclei with momentum 2.0 GeV/c per nucleon and intensity of about 109nuclei per cycle were accelerated at the JINR nuclotron and a beam of secondary nuclei with a magnetic rigidity corresponding to the ratio Z/A=6/9 was formed. The information obtained was used to analyze 9C nucleus interactions in emulsion. + 9C 0.1265 s 9B 540 eV 13O 8.58 ms 6Be & 3He Triple 3He process: 2 4He & 15.88 MeV at the output 12O 0.4 MeV

28. “3He Process: mixed isotope fusion” 12C 98.89 % Energy release: 9.13 MeV + 12N 11.0 ms 11C 20.38 m 14O 70.6 s CNO cycle 7Be 53.3 d 15O 122 s + 11B 80.2 % Energy release: 16.59 MeV + 10B 19.8% 10C 19.2 s 14O 70.6 s 6Be & 4He 13O 8.58 ms

29. Walking along proton stability line 20Mg 95 ms 20Na 448 ms 16Ne 0.122 MeV 17Ne 109 s 18Ne 1.67 s 19Ne 17.2 s 15F 1 MeV 20Ne 90.48% 12O 0.4 MeV 13O 8.58 ms 14O 70.6 s 17F 64.5 s 19F 100% 16F 0.04 MeV 18F 110 min 11N 1.58 MeV 15O 122 s 16O 99.8% 12N 11 ms 13N 10 min 14N 99.6%

30. Multifragmentation in H&He 6Be, 0.092 MeV +12 MeV 9C, 126.5 ms +16 MeV 12O 0.4 MeV +38 MeV

31. Multifragmentation in H&He 10C 19.2 s 13O 8.58 ms 16Ne 0.122 MeV

32. Multifragmentation in H&He 11C 20.38 m 14O 70.6 s 17Ne 109 s 20Mg 95 ms

33. Fragmentation of relativistic nuclei provides an excellent quantum “laboratory” to explore the transition of nuclei from the ground state to a gas-like phase composed of nucleons and few-nucleon clusters having no excited states, i. e. d, t, 3He, and . The research challenge is to find indications for the formation of quasi-stable systems significantly exceeding the sizes of the fragments. Search for such states on the nuclear scale is of undoubted interest since they can play a role of intermediate states ("waiting stations") for a stellar nuclear fusion due to dramatically reduced Coulomb repulsion. The fragmentation features might assist one to disclose the scenarios of few-body fusions as processes inverse to fragmentation.

34. We are sincerely grateful to the Management of the G. N. Flerov Laboratory rendered urgent support in acquisition of the last emulsion stack made in Russia.

35. The observations of the multifragmentation of light relativistic nuclei carried out by means of emulsions have been reviewed. The characteristic feature of the charge topology in the fragmentation of Ne, Mg, and Si is a suppression of binary splitting to fragments with charges larger than 2. The growth of the nucleus fragmentation degree is revealed in an increase of the multiplicity of Z= 1,2 fragments. The features of systems involving , d and t have been determined in fragmentation of Li, Be, B, C, N, and O. Clustering in the form of deuterons in 6Li and 10B fragmentation, as well as of tritons in the 7Li case has been revealed. The 3-body dissociation is found to be important for these nuclei. Emulsions exposed to relativistic 14N and 11B isotopes are being analyzed with the aim to study clustering of these types. The 3He clustering can be detected in neutron-deficient Be, B, C and N dissociation. Irradiation of emulsions by 7Be, 8B, and 9C nuclei has been performed. Irradiation by 10C, 11C, and 12N are planned. An analysis of the “white” stars from 7Be nuclei demonstrates the 3He clustering. Emulsions provide a unique basis for reconstructing relativistic multiparticle systems. Some of these systems are expected to play the role of the initial or intermediate loosely bound states in a fusion of more than two nuclei in nucleosynthesis in stars. The described observations be employed as a ground in the investigations of such states.