Modifications of the tensor and spin-orbit interactions and the stretched states inPb208

Abstract

We have reanalyzed the (e, e') and (p, p') data at 318 MeV on the stretched, 12& 2 and 14, states of Pb using the ideas of G. Brown and co-workers on the reduction of meson and nucleon masses in the nuclear medium.The reaction calculations are compared with new, large basis random-phaseapproximation calculations using a residual interaction, also modified, in a consistent way. The resulting interaction, based on the one boson exchange (~+ p) model, has reduced tensor and enhanced spin-orbit strengths. Agreement between electron and proton quenching factors is found for effective masses, m */m =0.79-0.86. The reduction or enhancement factors for the modified interaction are in qualitative agreement with those found in other analyses.PACS number(s): 21.30.+ y, 27.90.+b, 24.10.Ht

Complete set of polarization transfer observables for the16O(p⃗,n⃗)<

“…[49]. Thus the modified tensor-evenṼ TNE and tensor-oddṼ TNO interactions are described in relation to the parameter β as…”

In-mediumscaling law and electron scattering from high-spin states inPb208

“…On the other hand, the value e 1.6 was found to work correctly for the 14 and 12 states in Pb, when only the effective p-meson mass correction was included in the calculations [3]. Our purpose is to investigate if this conclusion is modified or Dot when also the efFective pion coupling constant is put into the play and when the experimental data of Connelly and co-workers [10] concerning the new high-spin states in lead are considered.…”

“…All of them give rise to the required reduction, but its amount is not fully determined yet. In heavy nuclei [3] (actually Pb), the reduction was estimated by putting into agreement the observed quenching factors for (e, e') and (p, p') excitations of the 14 (6.75 MeV) and the two 12 (6.43 MeV and 7.06 MeV) high-spin states. Following the in-medium scaling law of Brown and Rho [9], a value of m'/m~= 0.79 was found to work adequately.…”

?-decay of the particle-hole states with the highest spins in208Pb

“…Simultaneously, because the structure is relatively well known, the reactions on 2~ are used to understand the reaction mechanism and determine free parameters in the reaction theory as the effective charge and magnetic quenching in electron scattering. More fundamental problems might also be accessible in this way; Hintz et al [13] discussed changes of the nucleon mass and nucleon-nucleon interaction as a function of nucleonic density from a comparison of (e, e') and (p,p') to these states, y-spectroscopy of these levels can give complementary information and aid in the interpretation of the inelastic scattering. Even more important although very basic is, that the resolution achieved with y-7 coincidences, can clarify the level scheme.…”