Tue·Feb 9, 2021Tuesday·February 9, 2021

1. 01*

   Quasi-free Neutron Knockout Reaction Reveals a Small $s$-orbital Component in the Borromean Nucleus ${}^{17}$B

   Z. H. Yang🇯🇵 · Y. Kubota🇯🇵 · A. Corsi🇫🇷 · K. Yoshida🇯🇵 · X.-X. Sun🇨🇳 · J. G. Li🇨🇳 · M. Kimura🇯🇵 · N. Michel🇨🇳 · K. Ogata🇯🇵 · C. X. Yuan🇨🇳 · Q. Yuan🇨🇳 · G. Authelet🇫🇷 and 64 other authors

   A kinematically complete quasi-free $(p,pn)$ experiment in inverse kinematics was performed to study the structure of the Borromean nucleus ${}^{17}$B, which had long been considered to have neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for $1s_{1/2}$ and $0d_{5/2}$ orbitals, and a surprisingly small percentage of 9(2)$\%$ was determined for $1s_{1/2}$. Our finding of such a small $1s_{1/2}$ component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in ${}^{17}$B. The present work gives the smallest $s$- or $p$-orbital component among known nuclei exhibiting halo features, and implies that the dominant occupation of $s$ or $p$ orbitals is not a prerequisite for the occurrence of neutron halo.

   nucl-exPRL(2021)·89 citations
2. 02*

   Ground-state and decay properties of neutron-rich 106Nb

   A. J. Mitchell🇦🇺 · R. Orford🇨🇦 · G. J. Lane🇦🇺 · C. J. Lister🇺🇸 · P. Copp🇺🇸 · J. A. Clark🇺🇸 · G. Savard🇺🇸 · J. M. Allmond🇺🇸 · A. D. Ayangeakaa🇺🇸 · S. Bottoni🇺🇸 · M. P. Carpenter🇺🇸 · P. Chowdhury🇺🇸 and 8 other authors

   The ground-state properties of neutron-rich 106Nb and its beta decay into 106Mo have been studied using the CARIBU radioactive-ion-beam facility at Argonne National Laboratory. Niobium-106 ions were extracted from a 252Cf fission source and mass separated before being delivered as low-energy beams to the Canadian Penning Trap, as well as the X-Array and SATURN beta-decay-spectroscopy station. The measured 106Nb ground-state mass excess of -66202.0(13) keV is consistent with a recent measurement but has three times better precision; this work also rules out the existence of a second long-lived, beta-decaying state in 106Nb above 5 keV in excitation energy. The decay half-life of 106Nb was measured to be 1.097(21) s, which is 8% longer than the adopted value. The level scheme of the decay progeny, 106Mo, has been expanded up to approximately 4 MeV. The distribution of decay strength and considerable population of excited states in 106Mo of J >= 3 emphasises the need to revise the adopted Jpi = 1- ground-state spin-parity assignment of 106Nb; it is more likely to be J => 3.

   nucl-exPRC(2021)·4 citations
3. 03*

   Quasi-elastic scattering of proton with 1 GeV energy on eight-nucleon cluster inside nucleus

   O. V. Miklukho🇷🇺 · A. Yu. Kisselev🇷🇺 · G. M. Amalsky🇷🇺 · V. A. Andreev🇷🇺 · G. V. Fedotov🇷🇺 · G. E. Gavrilov🇷🇺 · A. A. Izotov🇷🇺 · N. G. Kozlenko🇷🇺 · P. V. Kravchenko🇷🇺 · V. I. Murzin🇷🇺 · D. V. Novinskiy🇷🇺 · A. V. Shvedchikov🇷🇺 · V. A. Stepanov🇷🇺 · A. A. Zhdanov🇷🇺

   Available data on the polarization of the secondary proton (as a function of its momentum $K$) in the inelastic ({\it p, p${}^{\prime }$}) reactions with the ${}^9$Be, ${}^{12}$C, and ${}^{40}$Ca nuclei and differential cross section data (the momentum distributions) for the reactions at the initial proton energy 1 GeV and scattering angles $\Theta$=21${}^{\circ }$ and $\Theta$=24.5${}^{\circ }$ were analysed in a range of the high momenta $K$ close to the momentum corresponding to the proton elastic scattering off the investigated nucleus. A structure in the polarization and momentum distribution data at the high momenum $K$, related probably to quasi-elastic scattering off a ${}^8$Be-like nucleon cluster inside the nuclei, was observed.

   nucl-ex0 citations
4. 04*

   Spectroscopy of $A=9$ hyperlithium by the $(e,e^{\prime }{K}^{+})$ reaction

   T. Gogami🇯🇵 · C. Chen🇺🇸 · D. Kawama🇯🇵 · P. Achenbach🇩🇪 · A. Ahmidouch🇺🇸 · I. Albayrak🇺🇸 · D. Androic🇭🇷 · A. Asaturyan🇦🇲 · R. Asaturyan🇦🇲 · O. Ates🇺🇸 · P. Baturin🇺🇸 · R. Badui🇺🇸 and 75 other authors

   Missing mass spectroscopy with the $(e,e^{\prime }{K}^{+})$ reaction was performed at Jefferson Laboratory's Hall C for the neutron rich $\Lambda$ hypernucleus ${}_{\Lambda }^9\mathrm{Li}$. The ground state energy was obtained to be $B_{\Lambda }^{g.s.}=8.84\pm 0.17^{stat.}\pm 0.15^{sys.}\mathrm{MeV}$ by using shell model calculations of a cross section ratio and an energy separation of the spin doublet states ($3/2_1^{+}$ and $5/2_1^{+}$). In addition, peaks that are considered to be states of [${}^8\mathrm{Li}(3^{+})\otimes s_{\Lambda }=3/2_2^{+},1/2^{+}$] and [${}^8\mathrm{Li}(1^{+})\otimes s_{\Lambda }=5/2_2^{+},7/2^{+}$] were observed at $E_{\Lambda }(no.2)=1.74\pm 0.27^{stat.}\pm 0.11^{sys.}\mathrm{MeV}$ and $E_{\Lambda }(no.3)=3.30\pm 0.24^{stat.}\pm 0.11^{sys.}\mathrm{MeV}$, respectively. The $E_{\Lambda }(no.3)$ is larger than shell model predictions by a few hundred keV, and the difference would indicate that a ${}^5\mathrm{He}+t$ structure is more developed for the $3^{+}$ state than those for the $2^{+}$ and $1^{+}$ states in a core nucleus ${}^8\mathrm{Li}$ as a cluster model calculation suggests.

   nucl-exPRC(2021)·18 citations
5. 05*

   Cross sections for neutron-induced reactions from surrogate data: revisiting the Weisskopf-Ewing approximation for $(n,n^{\prime })$ and $(n,2n)$ reactions

   Oliver C. Gorton🇺🇸 · Jutta E. Escher🇺🇸

   Earlier work has demonstrated that cross sections for neutron-induced fission and radiative neutron capture can be determined from a combination of surrogate reaction data and theory. For the fission case, it was shown that Weisskopf-Ewing approximation, which significantly simplifies the implementation of the surrogate method, can be employed. Capture cross sections cannot be obtained, and require a detailed description of the surrogate reaction process. In this paper we examine the validity of the Weisskopf-Ewing approximation for determining unknown $(n,n^{\prime })$ and $(n,2n)$ cross sections from surrogate data. We find that peak cross sections can be estimated using the Weisskopf-Ewing approximation, but the shape of the $(n,n^{\prime })$ and $(n,2n)$ cross sections, especially for low neutron energies, cannot be reliably determined without accounting for the angular-momentum differences between the neutron-induced and surrogate reaction. To obtain reliable $(n,n^{\prime })$ and $(n,2n)$ cross sections from surrogate reaction data, a detailed description of the surrogate reaction mechanisms is required. To do so for the compound-nucleus energies and decay channels relevant to these reactions, it becomes necessary to extend current modeling capabilities.

   ↳ nucl-thnucl-exPRC(2023)·5 citations
6. 06*

   Radiative corrections to nucleon weak charges and Beyond Standard Model impact

   Leendert Hayen🇺🇸

   The nucleon axial charge is a central ingredient in nuclear and particle physics, and a key observable in precision tests of the electroweak Standard Model sector and beyond. We report on the first complete calculation of its electroweak quantum corrections up to $\mathcal{O}(\alpha )$, using a combination of current algebra techniques and QCD sum rules. We find a substantial enhancement due to the weak magnetism contribution in the elastic channel, and include higher-twist and target mass corrections at low $Q^2$ to find ${\Delta }_R^A=0.02881(22)$. Using analogous methods, we determine a new value for the vector charge renormalization, ${\Delta }_R^V=0.02474(27)$, and show how the two most recent calculations can be brought into agreement. This allows us to determine a corrected experimental $g_A^0=1.2730(13)$, which is a $>2\sigma$ shift away from the commonly quoted value. We use this new result to set constraints on exotic right-handed currents by comparing to lattice QCD results, and resolve a double-counting issue in the $|V_{ud}|$ extraction from mirror decays.

   ↳ hep-phnucl-exnucl-th11 citations
7. 07*

   High Energy Behaviour of Light Meson Photoproduction

   Moskov J. Amaryan (ODU)🇺🇸 · William J. Briscoe (GWU)🇺🇸 · Michael G. Ryskin (PNPI)🇷🇺 · Igor I. Strakovsky (GWU)🇺🇸

   We evaluated recent CLAS Collaboration measurements for the $90^{\circ }$ meson photoproduction off the nucleon using a tagged photon beam spanning the energy interval $s=3-11$ GeV${}^2$. The results are compared with the "Quark Counting Rules" predictions.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2021)·6 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.