Topology of multifragmentation of light • relativistic nuclei • by P. I. Zarubin, JINR • On behalf of the BECQUEREL Collaboration • All this and more on the Web site • http://becquerel.lhe.jinr.ru
RelativisticNuclear Physics Since 1970 Li A.M. Baldin
Mg-Si Dissociation into charge state 2+2+2+2+2+1 5 +proton
Advanced Composition Explorer Cosmic Ray Isotope Spectrometer Radioactive Clock isotopes Abundances of Iron, Cobalt, and Nickel Isotopes 1
Clustering building blocks:more than one nucleon bound, stable & no exited states below particle decay thresholds – deuteron, triton, 4He, and 3He nuclei
=0.092 MeV A=6 “Are you Boromean too?”
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.
4.5 A GeV/c 16O Coherent Dissociation (PAVICOM image)
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.
4.5A GeV/c 20Ne Peripheral Dissociation into charge state 2+2+2+2+2 with 8Be like fragments
4.5A GeV/c 24Mg Peripheral Dissociation into charge state 2+2+2+2+2+2 with 8Be and 12C* like fragments
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
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.
dN/dTn 4.5A GeV/c12C:<T3>=0.4 MeV 22Ne5 24Mg5 +3He 0 1.6 2.4 0.8 Tn=(M*n - n M )/(4 n), MeV
Alpha-particle condensation in nucleiP. Schuck, H. Horiuchi, G. Ropke, A. Tohsaki, C. R. Physique 4 (2003) 537-540 At least light nα-nuclei may show around the threshold for nα disintegration, bound or resonant which are of the α-particle gas type, i. e., they can be characterized by a self-bound dilute gas of almost unperturbed α-particles, all in relative s-states with respect to their respective center of mass coordinates and thus forming a Bose condensed state. Such state is quite analogous to the recently discovered Bose condensates of bosonic atoms formed in magnetic traps. The only nucleus, which shows a well-developed α-particle structure in its ground state is 8Be. Other nα-nuclei collapse in their ground states to much denser system where the α-particles strongly overlap and probably loose almost totally their identity. When these nα-nuclei are expanded, at some low densities α-particles reappear forming a Bose condensate. If energy is just right, the decompression may stall around the α-condensate density and the whole system may decay into α-particles via the coherent state. 12C→3 α, ….,40Ca→10 α, 48Cr→3 16O, 32S→16O+4 α
Deuteron-Alpha Clustering in Light Nuclei 50V(0.25%) 14N(99.634%) 10B(19.9%) 6Li(7.5%) d
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.
4.5A GeV/c 14N Coherent Dissociation with 8Be like fragmentation d/p 14N nucleus, like the deuteron, 6Li and 10B belong to a rare class of even-even stable nuclei. It is interesting to establish the presence of deuteron clustering in relativistic 14N fragmentation.
14N dissociation accompanied by 8Be like pair proton 3 after
1.3A GeV 9Be dissociation in 2+2. 10B9Be, Nuclotron, 2004. “white” star with recoil proton with heavy fragment of target nucleus
1A GeV 10B Fragmentation to 8B (PAVICOM image)
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.
Ground states – lowest excitations 12N 11.0 ms 9C 0.1265 s 10C 19.2 s 12C 98.89 % 11C 20.38 m 8B 0.769 s 11B 80.2 % 10B 19.8% 9B 540 eV 7Be 53.3 d 9Be 100% 8Be 6.8 eV 6Li 7.5 % 7Li 92.5 %
Crossing proton stability frontier 6Be, 0.092 MeV 7Be, stable 6Вe pp4He -1.372 MeV 6Вe3He3He +11.48 MeV 8B, 770 ms 7B, 1.4 MeV 7B p6Вe -2.21 MeV 8C, 0.23 MeV 9C, 126.5 ms 8С pp6Be -2.14 MeV
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.
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.
“Triple He Process: pure isotope fusion” The fusion 3He3He3He6Be3He9С is one more option of the “3He process”. In the 9С8C 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
“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
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%
Secondary beams of light radioactive nuclei will be produced mostly via charge exchange reactions. 8B and 9Be beams will be formed via fragmentation reaction of 10B.
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 or loosely bound 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.