The Coulomb dissociation of 14Be 宋玉收 哈尔滨工程大学 上海

Contents The background and the motivation The objective The contents of the experimental research Experiment solution Beam application

The background and the motivation Low-lying dipole excitation mechanism; Scarcity of experimental results and large uncertainty of existed experimental data (14Be); Theoretical calculation need more experimental support –Different from 11Li and 6He, three-body model or five-body model; –valence neutron and excited-core configuration ; Coulomb excitation has larger cross section and is feasible for drip-line nuclei research at RIBLL;

68Ni 、 130,132Sn M. Labiche et. al, prl Coulomb dissociation

prl Large uncertainty of the exp. data; 2.No quantitative spectroscopic factor discussion in detail; 3.The peak position and integration of the energy spectrum deviate from the theoretical result; 4.No 2-n correlation discussion; 1.Invariant mass spectrum; 2.Large (2s 1/2 ) 2 admixture; prl , npa Enhanced low-lying strength of E1;

Microscopic calculations (Cluster dynamics) prc , prc Quantum Monte Carlo A-nucleon calculations (Many-body problem) npa c.1999 semi-phenomenological description (npa ) S 2n (exp.) andR rms (exp.) → S 2n =0.9MeV spectrum (exp.) peak position+ model

The narrow B(E1) shape is quite different from other Borromean halo nuclei; vary the binding energy, the radius, and the admixture of different components of WF; initial and final state WF considered; S 2n =0.9MeV S 2n =1.34MeVS 2n =1.34MeV, R rms =3.10±0.15fm spectrum (exp.) peak position+ model

Integration of the excitation strength Similar as 8He and more complicated than 11Li, 6He.

s01/2 0p3/2 0p1/2 1s1/2 0d5/2 n complicated core structure should be considered closed p shell 14Be S 2n 13Be 0d5/2 13Be s-wave bound state closed p shell? magic number loss or excited core?

In 2000’s 14Be Coulomb break up (14Be+Pb) prl Be nuclear break up (14Be+C, 14Be+p) R rms =3.25±0.11fm, npa The first 2+ state of 14Be, plb cluster breakup of 14Be, prc systematic study of 14Be+C, npa Coulomb dissociation of Heavier nuclei close to neutron drip line 31Ne Coulomb Breakup,PRL 103, (2009) 19,20,22C Nuclear Breakup, N.Kobayashi et al., PRC, in press Kinematically complete measurement of Coulomb Breakupof 22C, 19B, Production of 25,26O May 2012

The objective The correlation (spatial) of two valence neutrons by sum rule; Spectroscopic factor of 2s 1/2 and 1d 5/2 ; To verify the two-neutron bonding energy S 2n ; To discuss the reasonability of 3-body and 5-body14Be model by the energy spectrum and neutron-removal cross section; 12Be core is inert or not; To understand systematically about the soft E1 excitation of 2-n halo nuclei like 6He, 11Li, 14Be; npa

The contents of the experimental research The kinematically complete measurement of the break up of 14Be on Pb target; The angular distribution of 12Be+n+n in mass center coordinate; Angular distribution of valence neutrons; To reconstruct the invariant mass spectrum of 14Be; To eliminate the nuclear interaction contribution from the transition strength by neglecting non-peripheral collision; To obtain the reduce transition strength B(E1) by the virtual photon model;

12 Be n n 14 Be 12 Be n n n n Pb (high Z target )  Invariant Mass M 14Be 14Be* 12Be+n+n  Excitation Energy E*

EMD reconstruction 11Li

Spectroscopic factor Energy weighted sum rule (EWSR, non-model dependent) prc

Non-correlated (independent particle model,  12 =90 。 ) r 1 =r 2 =r (3-body cluster calculation )  12 =?90 degree 2n correlated? Non-energy weighted sum rule (NEWS) npa EMD on Pb simulation M. Labiche et. al, prl n-n correlated

jkps Inert core? npa , R m exp =3.25±0.11fm discrepancy

S 2n core-excited probability the relation between binding energy, spectroscopic factor, and deformation coefficient .

Experiment solution Experimental setup –PPAC –Forward ion telescope –MunCos Pb target PPAC SiCsI MuNCos

level scheme of 12Be Some problems to be pay more attention –No gamma detector presented; –14Be 、 12Be particle identification, and coincidence between production ions and neutrons; –The influence of neutrons produced in the telescope on the detection of the break-up neutrons; –Position resolution and efficiency of detectors ahead target; –Target thickness

Beam application 200enA 的 18O 作为入射初级束， 3500um 的 9Be 作为初级靶，降能器为 2000um 的 Al ，分离提纯后的 14Be ，能量为 35AMeV ，能量展宽约 8MeV （ ~1.6% ），流强约为 20 pps. 14.4/hour*200hour=2880

Thanks