Experimentral studies of clustering in multifragmentation of relativistic nuclei

by P. I. Zarubin, JINROn behalf of the BECQUEREL Collaboration

All this and even more is on the Web site

http://becquerel.lhe.jinr.ru

Since 1970Since 1970

A.M. BaldinA.M. Baldin

RelativisticRelativistic Nuclear PhysicsNuclear Physics

Li

Advanced Composition Explorer

Cosmic Ray Isotope Spectrometer

Radioactive Clock isotopes

Abundances of Iron, Cobalt, and Nickel Isotopes

1

Dubna Nuclotron Dubna Nuclotron Few GeV beams of Few GeV beams of Relativistic NucleiRelativistic Nuclei

CClluusstteerriinngg iinn LLiigghhtt NNuucclleeiitt

33HHee

66LLii

77LLii

66HHee

77BBee

88BB

1122CC

1100BB

1122NN

1111BB

1111CC

99BBee

1100CC

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.

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

=0.6 MeV=1.5 MeV

A=5

“Are you Boromean too?”A=6

=0.092 MeV

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.

Advantages of relativistic fragmentation

4.5 A GeV/c 4.5 A GeV/c 1616O O

Coherent DissociationCoherent Dissociation

(PAVICOM image)(PAVICOM image)

4.5A GeV/c 4.5A GeV/c 1616O Coherent O Coherent Dissociation with Dissociation with 88Be like Be like fragmentationfragmentation

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 4.5A GeV/c 2020Ne Peripheral Dissociation into charge stateNe Peripheral Dissociation into charge state

2+2+2+2+2 with 2+2+2+2+2 with 88Be like fragmentsBe like fragments

Charge (>2) Light Fragment Charge, Z Number of Events

  5 4 3 2 1  

9+8+

1 1351  1

8+ - 2 7

7+   - - 1 1 6

7+   - - - 3 2

6+   - - 2 - 5 6+   - - 1 2 1

0+ - - 5 - 3

4.1A GeV/c 4.1A GeV/c 2222NeNe Charge Distribution of Fragments in Projectile Fragmentation Cone (without target excitations). Events: 90

1 event 5+3+2 and 1 event 4+3+31

4.5A GeV/c 4.5A GeV/c 2424Mg Peripheral Dissociation into charge stateMg Peripheral Dissociation into charge state2+2+2+2+2+1+12+2+2+2+2+1+1

4.5A GeV/c 4.5A GeV/c 2424Mg Peripheral Dissociation into charge stateMg Peripheral Dissociation into charge state

2+2+2+2+2+2 with 2+2+2+2+2+2 with 88Be like fragmentsBe like fragments

4.5A GeV/c 4.5A GeV/c 2424Mg Peripheral Dissociation into charge stateMg Peripheral Dissociation into charge state

2+2+2+2+2+2 with 2+2+2+2+2+2 with 88Be and Be and 1212CC** like fragments like fragments

4.5A GeV/c 4.5A GeV/c 2828SiSi Dissociation into charge state 2+2+2+2+2+2+1 Dissociation into charge state 2+2+2+2+2+2+1 (narrow cone) with pair of (narrow cone) with pair of 88Be and triple Be and triple 1212CC** like fragments like fragments

The common topological feature for fragmentation of the Ne, Mg, Si, and S 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

Tn=(M*n - n M )/(4 n ), MeV

0

0.8 1.6 2.4

4.5A GeV/c12C:<T3>=0.4 MeV

22Ne5 24Mg5 +3He

Deuteron-Alpha Clustering in Light Nuclei

10B(19.9%)

6Li(7.5%)

14N(99.634%)

50V(0.25%)

d

++4.5A GeV/c 4.5A GeV/c 66Li Coherent Li Coherent Dissociation (PAVICOM image)Dissociation (PAVICOM image)

66LLii

1A GeV 1A GeV 1010B Coherent B Coherent Dissociation Into 2+2+1Dissociation 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.

Fragment Charge Events with Q=5

No mesons

% White Stars

%

5 4 3 2 1

1 - - - - 4 4 0 0

- 1 - - 1 2 2 1 3

- - 1 1 - 10 11 5 12

- - - 2 1 60 65 30 73

- - - 1 3 15 16 5 12

- - - - 5 2 2 0 0

Total 93 41

10B Fragmentation Topology

4.5A GeV/c 4.5A GeV/c 1414N Coherent Dissociation with N Coherent Dissociation with 88Be like fragmentationBe 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.

1.3A GeV 9Be dissociation in 2+2. 10B9Be, Nuclotron, 2004.

“white” star

with recoil proton

with heavy fragment of target nucleus

1A GeV 1A GeV 1010B B Fragmentation to Fragmentation to 88BB

(PAVICOM image)(PAVICOM image)

“Triple H&He Process: mixed isotope fusion”

+

12C 98.89 %

One more path to 12C and 4He production

8B 0.769 s 12N 11.0 ms

Toward CNO cycle& burning

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 (10В8B fragmentation) was formed. Information on the 8B interactions in emulsion had been obtained. We plan to determine the probabilities of forming “white” stars in 8B7Bер, 3Hep, 6Lipp, and dpp. In the 8В7В 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.

Triton-Alpha Clustering in Light Nuclei11B7Li

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.

6Be

7Be

8B

9C

Pure 3He Nucleus Clustering in Light Nuclei ?

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.

Fragment Charge White Stars

%

3 2 1

- 1 2 38 51

- 2 - 28 37

1 - 1 7 9

- - 4 2 3

Total 75

7Be Fragmentation Topology

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.

A=7

=1.5 MeV

7Li 92.5 %

7Be 53.3 d

8B 0.769 s

10B 19.8%

11B 80.2 %

12C 98.89 %11C 20.38 m

12N 11.0 ms

9Be 100%

9C 0.1265 s 10C 19.2 s

8Be 6.8 eV

9B 540 eV

6Li 7.5 %

Ground states – lowest excitations

“Triple He Process: pure isotope fusion”

Triple 3He process: 2 4He & 15.88 MeV at the output

+ 9C 0.1265 s

9B 540 eV

13O 8.58 ms

12O 0.4 MeV

6Be & 3He

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.

“3He Process: mixed isotope fusion”

Energy release: 16.59 MeV

+

11C 20.38 m

13O 8.58 ms

6Be & 4He

12N 11.0 ms +

14O 70.6 s

15O 122 s

+ 11B 80.2 %

CNO cycle

12C 98.89 %

7Be 53.3 d

10C 19.2 s

10B 19.8%

14O 70.6 s

Energy release: 9.13 MeV

7Be, stable

8B, 770 ms

9C, 126.5 ms

6Be, 0.092 MeV

7B, 1.4 MeV

8C, 0.23 MeV

6Вe pp4He-1.372 MeV

8С pp6Be-2.14 MeV

7B p6Вe-2.21 MeV

6Вe 3He3He+11.48 MeV

Crossing proton stability frontier

12O 0.4 MeV

9C, 126.5 ms

6Be, 0.092 MeV

+12 MeV

+16 MeV

+38 MeV

Multifragmentation in H&He

11N 1.58 MeV

12O 0.4 MeV

15F 1 MeV

13N 10 min

20Na 448 ms

20Mg 95 ms

Walking along proton stability line

12N 11 ms

16Ne 0.122 MeV

14N 99.6%

13O 8.58 ms 14O 70.6 s

15O 122 s 16O 99.8%

19F 100%

20Ne 90.48%

16F 0.04 MeV17F 64.5 s 18F 110 min

17Ne 109 s 18Ne 1.67 s 19Ne 17.2 s

10C 19.2 s

13O 8.58 ms

16Ne 0.122 MeV

Multifragmentation in H&He

11C 20.38 m

14O 70.6 s

17Ne 109 s

20Mg 95 ms

Multifragmentation in H&He

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.

P A V I C O MP A V I C O M

Relativistic Nuclei in EmulsionFission Fragments in Films