1. Fragmentation of relativistic 9 Be and 14 N nuclei in nuclear track emulsion D. A. Artemenkov JINR, Dubna BECQUREL Collaboration web site: http://becquerel.jinr.ru/

2. Contents Introduction Roots Fragmentation of relativistic 9 Be nuclei Fragmentation of relativistic 14 N nuclei Summary

3. Introduction The fragmentation of a large variety of light nuclei was investigated using the emulsions exposed to few A GeV nuclear beams at JINR. In this energy range, the pattern of the relativistic fragmentation loses sensitivity either to the collision energy or to the particular properties of a target nucleus. The results of investigations of the relativistic 9 Be, 14 N nuclei fragmentation in emulsion which entails the production of He fragments are presented. The study of the 9 Be fragmentation at relativistic energies gives the possibility of observing the reaction fragments which are the decay products of unbound 8 Be nuclei(without combinatorial background). The results obtained for the 9 Be, 14 N nuclei are compared with similar data for the 12 C, 16 O and 22 Ne nuclei.

4. Roots The 12 С  3  and 16 O  4  fragmentation at the energy of 3.65 A GeV was studied at JINR Synchrophasotron*. *V.V. Belaga et al., Phys. At. Nucl., vol. 58 1905 (1995) 12 C  3 , 3.65 A GeV

5. The 16 О  4  fragmentation were investigated using a large amount of information (641 events). An analysis of the angular correlations gave evidence that the angular momentum was transferred to the systems of fragments and that the cascade decays via 8 Be and 12 C nuclei were nonessential**. (PAVICOM image) 16 О  4 , 3.65 A GeV **F.A. Avetyan et al., Phys. At. Nucl., vol. 59 №1 (102-108) 1996

6. Fragmentation of relativistic 9 Be nuclei at 1.2 A GeV Nuclear emulsions were exposed to relativistic 9 Be nuclei at the JINR Nuclotron. The beam of relativistic 9 Be nuclei was obtained in the 10 B  9 Be fragmentation reaction with polyethylene target. with heavy fragment of target nucleus “white” star (PAVICOM image) *.mov*.avi *.mov

7. 9 Be 8 Be n 4 He The method of nuclear emulsions used in the present report allows one to observe the charged component of the relativistic 9 Be  2He+n fragmentation channel. Owing to a good angular resolution of this method it is possible to separate the 9 Be fragmentation events which are accompanied by the production of an unstable 8 Be nucleus with its subsequent breakup to two alpha-particles. find: ~200 events of 9 Be  2He fragmentation Angular measurements for 131 events were carried out with an accuracy not worse then 4.5  10 -3 rad.

8. n 4 He Energy Level Diagram 9 Be

9. Opening angle  between two He fragments for the channel 9 Be  2He Θ 9 Be He

10. Excitation energy Q 2  for the channel 9 Be  2  2 +, 8 Be(2. 9 MeV, 1. 5 MeV) 0 +, 8 Be(92 keV, 6.8 еV)

11. Transverse momentum of He fragments (laboratory system ) Transverse momentum of He fragments (c.m.s.) p0 =1.9 A GeV/c A=4 ( in the assumption 4 He )

12. 9 Be  2  12 C  3  22 Ne  5  In this case we clearly see a tendency toward an increase of the mean  particle momentum with increasing their multiplicity. This implies a growth of the total coulomb interaction of  clusters arising in nuclei. ≈24 MeV/c, ≈103 MeV/c ≈141 MeV/c ≈200 MeV/c

13. The  * T velocity distribution in the c.m.s. of  particles

14. Fragmentation of relativistic 14 N nuclei at 2.1 A GeV A stack of layers of BR-2 emulsion of a relativistic sensitivity was exposed to a beam of 14 N nuclei accelerated to an energy of 2.1 A GeV at the Nuclotron (JINR). 14 N  3He+H, 2.1 A GeV find: 950 events of 14 N fragmentation. Angular measurements for 132 events of 14 N  3  +H were carried out. *.avi*.mov

15. Azimuthal angle  * ij of  pairs in the c.m.s. for 14 N  3  +X He 14 N He 8 Be ? 14 N  3 

16. Excitation energy Q 2  for the channel 14 N  3  +X 0 +, 8 Be

17. Excitation energy Q 3  for the channel 14 N  3  +X 1: all events 2: “white” stars

18. Excitation energy Q 3  for the channel 14 N  3  +X (with 8 Be cut) 14 N

19. Summary The results of investigations of inelastic interactions of 9 Be, 14 N nuclei are presented. The main features of 9 Be  2  relativistic fragmentation: In the P* T distribution of  particles there is observed the formation of two peaks with the mean values 24.3 MeV/c and 103.1 MeV/c. In the Q 2  invariant energy distribution of an  particle pair there is observed a separation of virtually all the events over the two energy intervals : from 0 to 1 MeV with a peak at 100 keV and from 2 to 4 MeV. This facts suggests the dominance of the 9 Be  8 Be+n fragmentation accompanied by a 8 Be decay from the ground (0 + ) and the first excited (2 + ) states to two  particles.

20. The  * ij distribution in the c.m.s. of  particles for 14 N is asymmetric with an abundance at 140 – 180 °. The energy scale of the 3 alpha system production has been estimated. According to the available statistics 80% of interactions are concentrated at 10-14 MeV. The fraction of the 14 N→3α+X channel involving the production of an intermediate 8 Be nucleus is about (25-30)%. The results obtained for the 9 Be, 14 N nuclei are compared with similar data for the 12 C, 16 O and 22 Ne nuclei. The data obtained from 9 Be angular measurements can be employed for the estimation of the role of 8 Be in more complicated N  systems.