Wed·May 20, 2020Wednesday·May 20, 2020

1. 01*

   Novel Penning-trap techniques reveal isomeric states in ${}^{128}$In and ${}^{130}$In for the first time

   D.A. Nesterenko🇫🇮 · A. Kankainen🇫🇮 · J. Kostensalo🇫🇮 · C.R. Nobs · A.M. Bruce · O. Beliuskina🇫🇮 · L. Canete · T. Eronen🇫🇮 · E.R. Gamba🇮🇹 · S. Geldhof🇫🇮 · R. de Groote🇫🇮 · A. Jokinen🇫🇮 and 12 other authors

   Isomeric states in ${}^{128}$In and ${}^{130}$In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing novel ion manipulation techniques, different states were separated and masses of six beta-decaying states were measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the $15^{-}$ isomer in ${}^{128}$Sn has been discovered in ${}^{128}$In at $1797.6(20)$ keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a $16^{+}$ spin-trap isomer. In ${}^{130}$In, the lowest-lying $(10^{-})$ isomeric state at $58.6(82)$ keV was resolved for the first time using the phase-imaging ion cyclotron resonance technique. The energy difference between the $10^{-}$ and $1^{-}$ states in ${}^{130}$In, stemming from parallel/antiparallel coupling of $(\pi 0g_{9/2}^{-1})\otimes (\nu 0h_{11/2}^{-1})$, has been found to be around 200 keV lower than predicted by the shell model. Precise information on the energies of the excited states determined in this work is crucial for producing new improved effective interactions for the nuclear shell model description of nuclei near ${}^{132}$Sn.

   nucl-exPLB(2020)·21 citations
2. 02*

   A two-neutron halo is unveiled in ${}^{29}$F

   S. Bagchi🇨🇦 · R. Kanungo🇨🇦 · Y. K. Tanaka🇩🇪 · H. Geissel🇩🇪 · P. Doornenbal🇯🇵 · W. Horiuchi🇯🇵 · G. Hagen🇺🇸 · T. Suzuki🇯🇵 · N. Tsunoda🇯🇵 · D. S. Ahn🇯🇵 · H. Baba🇯🇵 · K. Behr🇩🇪 and 35 other authors

   We report the measurement of reaction cross sections (${\sigma }_R^{\mathrm{ex}}$) of ${}^{27,29}$F with a carbon target at RIKEN. The unexpectedly large ${\sigma }_R^{\mathrm{ex}}$ and derived matter radius identify ${}^{29}$F as the heaviest two-neutron Borromean halo to date. The halo is attributed to neutrons occupying the $2p_{3/2}$ orbital, thereby vanishing the shell closure associated with the neutron number $N=20$. The results are explained by state-of-the-art shell model calculations. Coupled-cluster computations based on effective field theories of the strong nuclear force describe the matter radius of ${}^{27}$F but are challenged for ${}^{29}$F.

   nucl-exnucl-thPRL(2020)·97 citations
3. 03*

   Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: the subtraction function and moments of unpolarized structure functions

   Jose Manuel Alarcón (Universidad Complutense de Madrid)🇪🇸 · Franziska Hagelstein (AEC Bern)🇨🇭 · Vadim Lensky🇩🇪 · Vladimir Pascalutsa (JGU Mainz)🇩🇪

   The forward doubly-virtual Compton scattering (VVCS) off the nucleon contains a wealth of information on nucleon structure, relevant to the calculation of the two-photon-exchange effects in atomic spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of low-energy VVCS in chiral perturbation theory ($\chi$PT). Here we focus on the unpolarized VVCS amplitudes $T_1(\nu ,Q^2)$ and $T_2(\nu ,Q^2)$, and the corresponding structure functions $F_1(x,Q^2)$ and $F_2(x,Q^2)$. Our results are confronted, where possible, with "data-driven" dispersive evaluations of low-energy structure quantities, such as nucleon polarizabilities. We find significant disagreements with dispersive evaluations at very low momentum-transfer $Q$; for example, in the slope of polarizabilities at zero momentum-transfer. By expanding the results in powers of the inverse nucleon mass, we reproduce the known "heavy-baryon" expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant (B$\chi$PT) and heavy-baryon (HB$\chi$PT) frameworks.

   ↳ hep-phhep-latnucl-exnucl-th+1PRD(2020)·19 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.