Ca+ 12 C, 25 AMeV ( 40 Ca+ 40 Ca, 25 AMeV)

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1 Search for alpha-particle condensation with CHIMERA 40 Ca+ 12 C, 25 AMeV ( 40 Ca+ 40 Ca, 25 AMeV) De-excitation of quasi-projectiles (primary and secondary products) C.R. Badita, B.Borderie, N. Le Neindre, P. Napolitani, Ad. R. Raduta, M.F. Rivet et al. (ISOSPIN COLLABORATION)

2 Nuclear clusters in the medium Condensation only at very low density G. Ropke et al., PRL 80 (1998) 3177

3 Finite nuclei: 8 Be, 12 C R. B. Wiringa et al., PRC 62 (2000)

4 12 C*:Hoyle state Role in the creation of 12 C in stellar nucleosynthesis Predictions: F. Hoyle et al., Phys. Rev. 92 (1953) 1095 Observation: C. W. Cook, W. A. Fowler et al., Phys. Rev. 107 (1957) 508

5 Shell model calculations The most modern no-core shell model calculations predict the at around 17 MeV excitation energy 2 α s in 1S orbit, 1 in 2S 2 α s in 1S orbit, 1 in 1D 3 α s in 1S orbit A. Tohsaki et al., PRL 87 (2001)

6 Alpha cluster wave function A: antisymmetrizer A. Tohsaki et al., PRL 87 (2001)

7 Alpha cluster wave function Without adjustable parameters: 12 C: E(0 2+ ) E thr = theory MeV exp MeV 16 O: E(0 5+ ) E thr = theory MeV exp MeV E(0 6+ ) E thr = theory MeV exp MeV Rms radii calculated => ρ 0 /3 Y. Fusaki et al., PRL 101 (2008)

8 Hoyle state: almost ideal α-particle condensate (70%). Yamada and P. Schuck, EPJA 26 (2005) 185

9 From 12 C to n alphas

10 Alpha particle mean field potential Calculations done with approximation for nα >4 Estimate: maximum of 8-10 αs together in a condensate. Yamada and P. Schuck PRC 69 (2004)

11 CHIMERA experiment 1192 Si-CsI(Tl) telescopes

12 CHIMERA experiment 12 C*, 16 O*: secondary products of quasi-projectiles heavier nα nuclei: primary and secondary products Beam intensity: 10 7 ions/s Angular range used: Ө=1-62 (rings small part of the sphere) => 816 telescopes Percentage of telescopes usable:76% Dedicated alpha calibration for CsI(Tl) using TOF from Orsay

13 Multi-particle correlation function R. Charity et al., PRC 52 (1995) 3126 Alpha particles emitted in the forward part of the cm frame N alphas => determination of the alpha emitter reference frame => E k = E k i Correlation function: 1+R(E k )=Ycorr(E k )/Yuncorr(E k )

14 8 Be E tot =92 kev Exp: 70 kev Two-alpha correlation function (quality of calibration?)

15 three-alpha correlation function M α >=3 12 C second MeV Г=8.5 ev E tot =379 kev Yuncorr(Ek): Alphas in different events 2 alphas in the same event E ex =E tot +Q 3α threshold MeV third MeV

16 M α =3 three-alpha correlation function See also: F. Grenier et al., (INDRA coll.) NPA 811 (2008) 233

17 four-alpha correlation function M α >=4 16 O sixth MeV Г=166 kev E tot =660 kev Yuncorr(Ek): Alphas in different events 2 alphas in the same event + 3 alphas in the same event + 2 alphas in 2 different events 8 Be+ 8 Be threshold MeV 4α threshold MeV 12 C + α threshold MeV

18 Simulation filtered by the detector 12 C* (379 kev) 16 O* (660 kev) 4(+) 5-6+ below

19 INDRA data, Ar+Ni 32 AMeV granularity too bad for 4α

20 Conclusion and perspectives Energy calibrations ok for such studies Limitation of the multi-particle correlation method for excited states with large widths like 6th 0 + of 16 O (partially due to CHIMERA granularity => studies with FAZIA) It is necessary to indroduce intra-event correlation methods used in multifragmentation after selection with the multi-particle correlation method Observables of intra-event correlations: <E k >, σ Ek,<Ө rel > for 16 O and heavier nα nuclei

21 d-alpha and t-alpha correlations 6 Li* MeV 7 Li* 4.63 MeV

22 three-alpha correlation function

23 four-alpha correlation function