RNB Cortina d’Ampezzo, July 3th – 7th 2006 Elisa Rapisarda Università degli studi di Catania E.Rapisarda for the Diproton collaboration 18 *

ü Two proton radioactivity is a very exotic decay mode predicted since 1960 Goldansky Nucl. Phys. 19 (1960) N ü It is expected in Z-even PROTON RICH NUCLEI in the vicinity or beyond the proton drip line Mass of nuclei beyond the drip line Pairing in nuclei Sequence of single particle levels Deformation Tunneling process

Two types of 2p emission: - ground-state emission long lived: 45 Fe, 48 Ni, 54 Zn short lived: 6 Be, 12 O, 16 Ne, 19 Mg - emission from excited states β delayed: 22 Al, 31 Ar, … others: 14 O, 18 Ne, 17 Ne, 94 Ag To be measured: proton energies proton-proton angle Sequential emission Three body decay 2 He emission The mass of the Z-even two-proton emitter smaller than the mass of the odd-Z one-proton daughter In two-proton emitter the one- proton emission must be forbidden

ü Medium-mass proton drip-line nuclei are very promising ( 45 Fe, 48 Ni, 54 Zn and 94 Ag) First evidence of two-proton radioactivity in the decay of 45 Fe Phys. Rev. Lett. 89 (2002) GSI GANIL 4 decays 12 decays NO identification of individual protons NO measurements of their energies NO relative emission angle

18 Ne* a good candidate for the observation of diproton decay from excited level Search of 18 Ne* two proton has been already performed Gomez del Campo PRL 86(2001)43 using the fusion reaction 17 F+H at 44 MeV

The measured angular distributions cannot discriminate between direct or two step emission of 2p or 2 He emission 18 *

Search for DI-PROTON DECAY of excited states of 18 Ne 208 Pb 18 Ne 18 Ne* 16 O 2 He 208 Pb 18 Ne 18 Ne* 16 O Proton energy and angle correlations  di-proton emission? ü 35 MeV/A 18 Ne beam will interact on a heavy thick target ü The 6.15 MeV level should be populated by Coulomb excitation (E1 transition)

20 Ne + 9 Be(500  m) at 45 AMeV Degrader Q 1 Q 2 Q 3 Q 4 Q 5 Q 6 Q 7 Q 8 Q 9 D1D1 D2D2 Production Target. Fragment Separator Production Target Q 1,2 18  = 4msr  p/p = +/- 1% Max B  = 2.7 Tm

18 RIBs detected at the final focus Transmission % 20 Ne+ 9 Be 45AMeV 21 Na 20 Ne 19 Ne 18 Ne Ciclope beam line 20 degrees beam line I = 10 enA ü 9% of 18 Ne over the total produced RIBs rate ü 98% of transmission along the beam line

250 enA of primary beam current 60 kHz of secondary beam on the tagging detector  5 kHz of 18 Ne (9% of the total secondary beam)

Secondary Target (ΔE,ToF) (x,y) (A,Z), E Secondary Ion Si-Strip 1616 Tagged Ion 22 Na 21 Na 21 Ne 20 Ne 19 Ne 18 Ne 19 F 18 F 17 F 16 O 15 O 15 N 14 N 13 C 13 N 12 C 11 C 11 B 17 O Si-Strip X-Y Position

88 THREE-FOLD TELESCOPES ARRAY 50  m-300  m-CsI  4.5°  16.5° 81 TWO-FOLD TELESCOPES ARRAY 300  m-CsI  4.5°

21 Na 21 Ne 20 Ne 19 Ne 18 Ne 18 F 17 F 16 O 15 O 14 N 13 C 12 C 11 C 11 B Identification can be checked looking to the  E-E scatter plot in forward detectors

The procedure have been checked for the 16 O 16 v lab v cm E* = E cm + Q val 16 O 12 C + alpha Q val = MeV Energy level of 16 O

250 enA of primary beam current 60 kHz of secondary beam on the tagging detector  5 kHz of 18 Ne (9% of the total secondary beam) Around 100 F+p and 20 O+p+p events analyzed up to now E1 E2 Gomez del Campo et al. PRL 86(2001)43

Details of the three O+p+p events in the 6 MeV region E*=6.01MeV E p1 =.56 MeV E p2 =.88MeV  1 =124°  2 =106°  1 =-42°  2 =-6°  o =36° E*=6.14MeV E p1 =1.3 MeV E p2 =.18MeV  1 =50°  2 =94°  1 =90 E*=6.51MeV E p1 =1.66 MeV E p2 =.22MeV  1 =144°  2 =114°  1 =82°  2 =44°  o =65° (1 -,2 + ) 8.5 (1 -,2 + ) A B C Possible new levels in 18 Ne A.9.9  0.25 (1 -,2 + ) B.10.8  0.5 (1 -,2 + ) C.13.2  0.5 (1 -,2 + )

We are able to identify E1 and E2 resonances (resolution of about 1 MeV in the excitation energy measurement) The observation of 3 events O+2p in the good excitation energy range notwithstanding the not perfect efficiency tell us that the branching ratio of the 2p decay is not too small Observation of three new possible higher energy levels in 18 Ne First example of measurements with exotic beam at intermediate energy at LNS  STATISTICS  Better reconstruction of the reaction kinematics