Abdenbi KHOUAJA Reaction cross section and strong absorption radius measurements of neutron-rich exotic nuclei in the vicinity of closed shells N=20 and N=28 Reaction cross section and strong absorption radius measurements of neutron-rich exotic nuclei in the vicinity of closed shells N=20 and N=28 I.N.F.N Laboratorio Nazionale del Sud Catania

 Available data of the reaction cross-section

Primary beam Secondary beam Alpha Spectrometer GANIL Degrader 9 Be with thickness of 25µm 48 Ca Energy=60.3A MeV Intensity=4000nAe Production target 181 Ta 22 C 21 C 23 N 17 B 14 Be 11 Li 29 F 32 Ne 35 Na 38 Mg 41 Al 43 Si 44 P 45 S 47 Cl New reaction cross section measurements  Experiment Details

L. Bianchi et al., Nucl. Instr. and Meth. A276 (1989) 509. W. Mittig et al., Bormio, Italy 1986 A. Gillibert et al., Phys. Lett. B176(1986)317. M = Q B  /L.T vol B  = M V/Q  Long flight path = 82m  Time of flight ~ 700ns  s  m/m ~ SISSI SpectromètreAlpha SPEG Silicon Telescope SPEG-GANIL

NaI  Reaction cross-section Direct method developed by A.C.C.Villari (which is a variant of the known transmission method) In this method, the stack of Silicon detectors is used as both : Reaction target Detection system

Masse (MeV)~E tot.T vol 2 Typical mass spectra as a function of the total energy (~ET 2 ) for 25 F (E= 45.5A MeV). Energy resolution ~ 0.23%. Effective resolution Q=2.58MeV Spectrum obtained directly from the silicon detectors Spectrum in coincidence with emitted gammas Spectra (a) : Spectra (b) : reaction probability  Reaction probability P R

Reduced strong absorption radius :  Parametrization of S.Kox Results  More than 70 radii are measured  19 radii are measured for the first time: 27 F, 27, 30 Ne, 33 Na, 28, Mg, Al, Si, P, S, 45 Cl.

 Parametrization of the reduced strong absorption radii: Z≤13 : evolution according to : W.Mittig et al., Phys. Rev. Lett. 59, 1889 (1987) Z≥13 : evolution according to: N.Aissaoui et al., Phys. Rev. C60, (1999) 8 ≤ Z ≤ 18 and 12≤A≤46 : r02r02 T Z /A stability r02r02 r02r02 New parametrization A.Khouaja et al (ENAM04) A.Khouaja et al (EXON04)

17 F 23 Al 27 P 23 O 29 Ne 22 N 24 F

 Strong influence of the isospin is revealed for each isobar,  New parametrization permits : To study the evolution of the matter distribution : efficiently reproduces the skin effect To give a fast indication on the existence of abnormal structures: deformation, halo… for these nuclei: 23 N, 29 Ne, 33 Na, 35 Mg, 44 S, 45 Cl, and 45 Ar 35 Mg 44 S 41 Ar 33 Na 45 Ar 45 Cl

Glauber Model  The effective nuclear matter radii “RMS”  The effective density distributions permits us to deduce:

 Coulomb-modified Glauber Model: Thickness density : : Transparency function : Profile function : T. ZHENG et al., Nucl. Phys. A709, 103 (2002) R.M. Devries et al., Phys. Rev. C22, 1055 (1980)

Standard Glauber model Coulomb-modified Glauber model

Matter radii: Radius Mean Square  Matter distribution: using 2pF density distribution Skin effect where: k=Z or N Two free parameters

. Absence of data at intermediate energy: T.Suzuki et al., Phys. Rev. Lett. 75, 3244 (1995) Presence of data at intermediate energy : We disentangle: and,  The results of T.Suzuki ( Phys. Rev. Lett. 75, 3244 (1995) )  Actual work,

Preliminary results

protons neutrons Si-target C-target

Matter density distributions

Matter Radii Mean Square

L.S. Geng et al, Nucl. Phys. A 730(2004)80

Conclusion  In the same setup, more than 70 reaction cross sections are measured  The measurements, for the first time, of 19 new reaction cross sections  New phenomenological parametrization is suggested for the nuclear radii in the region of closed shells N=8 and N=28, which permits :  to reproduce the skin effect far from stability  to give a current indications on the existence of abnormal structure: 23 N, 29 Ne, 33 Na, 35 Mg, 44 S, 45 Cl, and 45 Ar  We disentangle the effect of nuclear size and surface diffusivity of matter distribution using Glauber model.

Great thanks to MAGNEX’s group: A.Cunsolo, F.Cappuzzelo, J.S.Winfield, C.Nocifiro, A.Khouaja, A.Foti, S. E.A.Orrigo, M.Cavallaro Collaborators: D.Hirata Open University, U.K A.C.C.Villari GANIL, Caen, France M.Benjelloun LPTN, El jadida, Morocco A.Khouaja LNS-INFN, Catania, Italy Participants: H.SAVAJOLS 1, W.MITTIG 1, P.ROUSSEL-CHOMAZ 1, N.ORR 2, S. PITAE 1, C.E.DEMONCHY 1, L.GIOT 1, M.CHARTIER 3, A.GILLIBERT 4, D. BAIBORODIN 5, Y. PENIONZHKEVICH 6, W.CATFORD 7, A.LÉPINE-SZILY 8, Z.DLOUHY 6 1 GANIL (IN2P3/CNRS – DSM/CEA), B.P Caen Cedex 5 France 2 LPC, ISMRA et Université de Caen, F-6704 Caen, France 3 University of Liverpool, Dept. of Physics, Liverpool, L69 7ZE, UK 4 SPHN (DAPNIA/CEA), CEN Saclay, F Gif-sur Yvette, France 5 FLNR, JINR, Dubna, P.O.Box 79, Moscow, Russia 6 Nucl.Phys.Ins., ASCR, Rez, Czech Republic 7 University of Surrey, Stoy Fill, Nuclear Physics Dept, Guilford, GU27XH, UK 8 University of São-Paulo, IFUSP, C.P.66318, São –Paulo, Brazil

MERCI DE VOTRE ATTENTION

avec finite range zero range R.M. Devries et al., Phys. Rev. C22, 1055 (1980) T. ZHENG et al., Nucl. Phys. A709, 103 (2002) S.K Charagi et al., Phys. Rev. C41, 1610 (1990) profile function :

 Discovery of a new magic number, N=16 : A.Ozawa et al., Phys. Rev. Lett. 84, 5493(2000) Possible existence of one-neutron halo structure : 22 N, 23 O, 24 F Appearance of a new magic number N=16 Magic number

 Matter distribution far from stability Halo structure Skin structure  RMF: 1n-halo nuclei: 33 Na, 34 Na and 35 Mg T.Suzuki et al, Nucl. Phys. A616, 286c (1997) J.S.Wang et al., Nucl. Phys. A691, 618(2001) 17 B 14 Be 11 Be 11 Li 8 He 6 He I.Tanihata et al, Phys.Lett. B206, 592 (1988)

 Our results are slightly small to the results of T.Suzuki  The precision of different results are ameliorated  As a preliminary results, the skin effect is revealed in the structure of these nuclei