SEARCH FOR RARE CLUSTER CONFIGURATION IN 14 C NUCLEUS International Conference on Particle Physics and Astrophysics October 05 – 10, 2015 L.Yu. Korotkova, B.A. Chernyshev, Yu. B. Gurov, S.V. Lapushkin, R.V. Pritula, T.D. Schurenkova National Research Nuclear University “MEPhI” “MEPhI” 1

 S  Study of mechanisms of stopped pion absorption by light nuclei;  S 14 C  Search for rare cluster configurations in light nucleus ( 14 C );  S 12,13 Be  Search for new highly excited states of 12,13 Be isotopes and their rare cluster decays;  S 11 Li  Spectroscopy of the 11 Li halo nucleus 2 Main goals :

14 C cluster structure 14 C = 12 C + 2n = 3 α + 2n AMD model prediction: 14 C = 12 C + 2n = 3 α + 2n [1] 14 C = 10 Be + α For the excited states of 14 C : 14 C = 10 Be + α [2] What if 14 C = 11 Li + 3p ??? 9 Li + 2n 9 Li + 2n [1] T. Suhara and Y. Kanada-En’yo // Journ. of Phys.: Conf. Ser. 321 (2011) [2] P. J. Haigh et al. // Phys. Rev. C 78 (2008)

Advantages of the method:  Formation of residual nuclei with large neutron excess  Absence of uncertainties due to the energy resolution and angular divergence of beam  Ability to study a wide range of nuclei in a single experimental run 4 3-body channels of the stopped pion absorption by nuclei

Beam Targets : 12 C & 14 CRate speed 1/s SCD- telescopeStart identification energy, MeV Е  = 30 MeV (  p/p =  1%) Thickness – 25 mg/sm 2, (135µm), diameter – 26mm, 14 C target: 14 C – 77%, 12 C – 23% 12 C – impurities < 1%  6  10**4 2 Si(Au) Т=100, 450 µm 14 Si(Li) Т=3 mm, Wm.s.  0.1mm S=8 mm 2  =55  15 mster Еp  3.5, Еd  4 5

2-dim Dalitz-plot for 11 В(π ,dt)Х reaction 11 В = 5 Li + 6 He B(π¯,dt) 6 He and 11 B(π¯,dt) 6 He* Е х ( 6 Не*) = MeV 2. and 3. π¯ + 11 В → d + 8 Li* + n → d + t + 5 He + n Е х ( 8 Li*) = MeV (2) and Е х ( 8 Li*) = 6.53 MeV (3). 4. π¯ + 11 В → t + 7 Li* + n → t + d + 5 He + n Е х ( 7 Li*) = MeV 6 11 В(π ,dt)Х Nucleus-2013, Moscow Yu.B. Gurov et al. // BRAS: Phys. 79 (2014) 474. Cluster structure of 11 В

7 12 C admixture in the 14 C target Experimental spectrum (dots with errors) with the 12 C admixture contribution (blue histogram) Experimental spectrum after the subtraction of the 12 C admixture contribution

8 2-dim Dalitz-plot for 14 C(π ,pd)Х reaction C(π¯,pd) 11 Li and 14 C(π¯,pd) 11 Li* 2. π¯ + 14 C → p + 13 Be* d + 11 Li 3. π¯ + 14 C → d + 12 Be* p + 11 Li 14 C = 3 p + 11 Li 14 C = 3 p + 11 Li exotic cluster structure ” 11 Li – spectator” momentum distribution F(р) = (p/p F ) 2 exp(–(p/p F ) 2 ) Search for rare cluster structure

9 Bohlen H.G. et al. // Z. Physik A 351 (1995) 7 Korsheninnikov A.A. et al. // Phys. Rev. Lett. 78 (1997) 2317 Current experimental situation: 11 Li J.H. Kelley et al. // NP A 880 (2012), 88

E r, MeVτ, ms or Г, MeVReaction / Paper g.s.8.75 ± 0.14 ms[1], 14 C(π −, pd)Х 0.9 ± 0.1~ C(π −, pd)Х 1.22 ± ± 0.15[1][1] 2.3 ± 0.3~ C(π −, pd)Х 2.42 ± ± 0.30[1][1] 3.9 ± 0.3< C(π −, pd)Х C(  , pd) 11 Li [1] Kelley J.H. et al. // Nucl. Phys. A 880 (2012) C(  , pd) 11 Li MM spectrum for the 14 C(  , pd) 11 Li reaction

11 Current experimental situation: 12,13 Be E r, MeVDecay mode 10,2 12,8 15,5 α + 8 He 13,5 14,5 6 He + 6 He 25,0 28,0 p + 11 Li Highly excited states of 12 Be [1] of 12 Be [1] Excited states of 13 Be E r, MeV or a s, fmГ, MeVWork -3,4 fm (g.s.)[2] 0,51(1)0,45(3)[2] 2,0[3] 2,39(5)2,4(2)[2] 3,0[3] [1] R.J. Charity et al. // Phys. Rev. C 76 (2007) [2] Y. Kondo et al. // Phys. Lett. B 360 (2010) 245 [3] H. Simon et al. // Nucl. Phys. A 791 (2007) 267

Highly excited states of 12,13 Be C(  ,p) 13 Be 14 C(  ,d) 12 Be 14 C(  ,p) 13 Be MM spectrum for the 14 C(  ,p) 13 Be reaction 14 C(  ,d) 12 Be MM spectrum for the 14 C(  ,d) 12 Be reaction π¯ + 14 C → p + 13 Be* d + 11 Li π¯ + 14 C → d + 12 Be* p + 11 Li E r ≈ 30 MeV

14 C 14 C(  , pd)X;  Search for the rare cluster structure of the 14 C isotope was studied in   - absorption reaction 14 C(  , pd)X; 14 C ( 3 p + 11 Li)  The evidence of the rare cluster structure of the 14 C ( 3 p + 11 Li) was found for the first time; E r ≈ 30 MeV  Indications on highly excited states of 12,13 Be were found with the energy E r ≈ 30 MeV, which decay onto 12 Be → p + 11 Li and 13 Be → d + 11 Li; E r = 3.9 ± 0.3 MeV  Ground state and 3 excited states of 11 Li were found. The most excited level with the energy E r = 3.9 ± 0.3 MeV was found for the first time 13

Thank you Thank you for your attention! for your attention! 14