Nuclear Theory·nucl-th

Monday·August 19, 2019

2 papers—1 primary·1 cross-listed

01
Nucleon-to-Resonance Form Factors at Large Photon Virtualities
J. Segovia🇪🇸 · C. Chen🇩🇪 · Z.-F. Cui🇨🇳 · Y. Lu🇨🇳 · C.D. Roberts🇺🇸
We present a unified description of elastic and transition form factors involving the nucleon and its resonances; in particular, the $N (1440)$ , $Δ (1232)$ and $Δ (1600)$ . We compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-kindred momentum dependence with results obtained using a confining, symmetry-preserving treatment of a vector $\otimes$ vector contact-interaction in a widely-used leading-order (rainbow-ladder) truncation of QCD's Dyson-Schwinger equations. This comparison explains that the contact-interaction framework produces hard form factors, curtails some quark orbital angular momentum correlations within a baryon, and suppresses two-loop diagrams in the elastic and transition electromagnetic currents. Such defects are rectified in our QCD-kindred framework and, by contrasting the results obtained for the same observables in both theoretical schemes, shows those objects which are most sensitive to the momentum dependence of elementary quantities in QCD.
nucl-thhep-exhep-lathep-ph+1AIP Conf.Proc.(2020)·6 citations
02
One-proton and one-neutron knockout reactions from $N = Z = 28$ $^{56}$ Ni to the $A = 55$ mirror pair $^{55}$ Co and $^{55}$ Ni
M. Spieker · A. Gade · D. Weisshaar · B. A. Brown · J. A. Tostevin · B. Longfellow · P. Adrich · D. Bazin · M. A. Bentley · J. R. Brown · C. M. Campbell · C. Aa. Diget and 6 other authors
We present a high-resolution in-beam $γ$ -ray spectroscopy study of excited states in the mirror nuclei $^{55}$ Co and $^{55}$ Ni following one-nucleon knockout from a projectile beam of $^{56}$ Ni. The newly determined partial cross sections and the $γ$ -decay properties of excited states provide a test of state-of-the-art nuclear structure models and probe mirror symmetry in unique ways. A mirror asymmetry for the partial cross sections leading to the two lowest $3/ 2^{-}$ states in the $A = 55$ mirror pair was identified as well as a significant difference in the $E 1$ decays from the $1/ 2_{1}^{+}$ state to the same two $3/ 2^{-}$ states. The mirror asymmetry in the partial cross sections cannot be reconciled with the present shell-model picture or small mixing introduced in a two-state model. The observed mirror asymmetry in the $E 1$ decay pattern, however, points at stronger mixing between the two lowest $3/ 2^{-}$ states in $^{55}$ Co than in its mirror $^{55}$ Ni.
↳ nucl-exnucl-thPRC(2019)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nucleon-to-Resonance Form Factors at Large Photon Virtualities

One-proton and one-neutron knockout reactions from N=Z=28 56Ni to the A=55 mirror pair 55Co and 55Ni

Affiliations

One-proton and one-neutron knockout reactions from $N = Z = 28$ $^{56}$ Ni to the $A = 55$ mirror pair $^{55}$ Co and $^{55}$ Ni