Tue·May 20, 2025Tuesday·May 20, 2025

1. 01*

   Unbound neutron $\nu 0d_{3/2}$ strength in ${}^{17}$C and the N=16 shell gap

   J. Lois-Fuentes🇪🇸 · B. Fernández-Domínguez🇪🇸 · F. Delaunay🇫🇷 · X. Pereira-López🇪🇸 · N.A. Orr🇫🇷 · M. Płoszajczak🇫🇷 · N. Michel🇨🇳 · T. Otsuka🇯🇵 · T. Suzuki🇯🇵 · W.N. Catford🇬🇧 · O. Sorlin🇫🇷 · N.L. Achouri🇫🇷 and 52 other authors

   Significant continuum strength has been observed to be populated in ${}^{17}$C produced in the d(${}^{16}$C,p) reaction at a beam energy of 17.2~MeV/nucleon. The strength appears at greater than $\sim$2~MeV above the single-neutron decay threshold and has been identified as arising from transfer into the neutron $0d_{3/2}$ orbital. Guided by shell model predictions the greater majority of the strength is associated with a 3/2${}^{+}$ state at an excitation energy of 4.40${}_{-0.14}^{+0.33}$ MeV and a much weaker 3/2${}^{+}$ level at 5.60${}_{-0.45}^{+1.35}$ MeV. The corresponding total widths were determined to be 3.45${}_{-0.78}^{+1.82}$ and 1.6${}_{-1.4}^{+4.6}$ MeV, respectively. From the backward angle proton differential cross sections and the branching ratios for neutron decay to the ${}^{16}$C(2${}_1^{+}$) level, the corresponding spectroscopic factors to the ground state were deduced to be 0.47$\pm 10$ and $<$0.09. Shell-model calculations employing the phenomenological SFO-tls interaction as well as Gamow Shell-Model calculations including continuum effects are in reasonable agreement with experiment, although the predicted strength lies at somewhat lower energy. The size of the N=16 shell gap (${\epsilon }_{\nu 0d_{3/2}}-{\epsilon }_{\nu 1s_{1/2}}$) was estimated to be 5.08${}_{-0.33}^{+0.43}$~MeV - some 1.3~MeV larger than found in the SFO-tls shell model calculation.

   nucl-exnucl-thPLB(2025)·1 citation
2. 02*

   The ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction -- state of the art, astrophysics, and perspectives

   Andreas Best · Philip Adsley · Ryan Amberger · Umberto Battino🇬🇧 · Thomas Chillery🇮🇹 · Marco La Cognata🇮🇹 · Richard James deBoer🇺🇸 · Daniela Mercogliano🇮🇹 · Shuya Ota🇯🇵 · David Rapagnani🇮🇹 · Ragandeep Singh Sidhu🇩🇪 · Roberta Spartà🇮🇹 · Aurora Tumino🇮🇹 · Michael Wiescher🇺🇸

   One of the most important stellar neutron sources is the ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction, which gets activated both during the helium intershell burning in asymptotic giant branch stars and in core helium and shell carbon burning in massive stars. The ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg reaction serves as the main neutron producer for the weak s-process and provides a short but strong neutron exposure during the helium flash phase of the main s-process, significantly affecting the abundances at the s-process branch points. The cross section needs to be known at very low energies, as close as possible to the neutron threshold at $E_{\alpha }=562$ keV ($Q=-478$ keV), but both direct and indirect measurements have turned out to be very challenging, leading to significant uncertainties. Here we discuss the current status of the reaction, including recent and upcoming measurements, and provide a discussion on the astrophysical implications as well as an outlook into the near future.

   nucl-exEPJA(2025)·4 citations
3. 03*

   Recoil Polarization in $K^{+}Y$ Electroproduction in the Nucleon Resonance Region with CLAS12

   D. S. Carman🇺🇸 · A. D'Angelo🇮🇹 · L. Lanza🇮🇹 · V. I. Mokeev🇺🇸 · P. Achenbach🇺🇸 · J. S. Alvarado🇫🇷 · M. J. Amaryan🇺🇸 · H. Atac🇺🇸 · H. Avakian🇺🇸 · N. A. Baltzell🇺🇸 · L. Barion🇮🇹 · M. Bashkanov🇬🇧 and 118 other authors

   Hyperon recoil polarization measurements for the exclusive electroproduction of $K^{+}\Lambda$ and $K^{+}{\Sigma }^0$ final states from an unpolarized proton target have been carried out using the CLAS12 spectrometer at Jefferson Laboratory. The measurements at beam energies of 6.535~GeV and 7.546~GeV span the range of four-momentum transfer $Q^2$ from 0.3 to 4.5~GeV${}^2$ and invariant mass $W$ from 1.6 to 2.4~GeV, while covering the full center-of-mass angular range of the $K^{+}$. These new $\Lambda$ polarization observables extend the existing data in a similar kinematic range but from a significantly larger dataset. However, they represent the first electroproduction measurements of this observable for the ${\Sigma }^0$. These data will allow for better exploration of the reaction mechanism in strangeness production, for further understanding of the spectrum and structure of excited nucleon states that couple to $KY$, and for improved insight into the strong interaction in the non-perturbative domain.

   nucl-exPRC(2025)·2 citations
4. 04*

   Analysis note: measurement of energy-energy correlator in $e^{+}{e}^{-}$ collisions at $91$ GeV with archived ALEPH data

   Hannah Bossi🇺🇸 · Yu-Chen Chen🇺🇸 · Yi Chen🇺🇸 · Jingyu Zhang🇺🇸 · Gian Michele Innocenti🇺🇸 · Anthony Badea🇺🇸 · Austin Baty🇺🇸 · Marcello Maggi🇮🇹 · Chris McGinn🇺🇸 · Yen-Jie Lee🇺🇸

   Electron-positron ($e^{+}{e}^{-}$) collisions provide a clean environment for precision tests of Quantum Chromodynamics (QCD) due to the absence of hadronic initial-state effects. We present a novel analysis of archived ALEPH data from the Large Electron-Positron Collider at the $Z$ pole, leveraging energy-energy correlators (EECs) to study hadronic energy flow with unprecedented precision. The two-point EEC is measured as a function of the angular separation between particles spanning from the collinear to the back-to-back limits in a remarkably differential test of perturbative and non-perturbative QCD. The results are consistent with previous LEP measurements and provide significantly improved precision and finer angular binning resolution, especially at small angles and in the back-to-back limit. Comparisons with \textsc{pythia} 6 simulations show overall agreement, with deviations in key kinematic regions offering insights into hadronization. The measurement performed here connects to new opportunities for precision QCD studies in archived and future collider data.

   ↳ hep-exnucl-ex26 citations
5. 05*

   Nucleon-nucleon correlation functions from different interactions in comparison

   Matthias Göbel🇮🇹 · Alejandro Kievsky🇮🇹

   Correlation functions as they can be observed in heavy-ion collisions using the femtoscopy technique are a powerful tool to study the interaction among different baryons or mesons. Specifically, the multi-nucleon correlation functions have been under intense experimental and theoretical investigation in the recent years. Due to the interest of using this observable as an input in the construction of potentials between hadrons we revisit the nucleon-nucleon correlation function and calculate it using different nuclear interactions at high precision. Since the nucleon-nucleon potential is determined to reproduce the two-nucleon scattering data, we would like to critically evaluate the amount of this information captured by the correlation function. We study the dependence of the correlations on the nuclear force giving detailed insights into the calculations, in particular the convergence behavior in the partial waves. The coupling between the different partial-wave channels is taken into account and the relevance of this effect is quantified. To make contact with precedent studies the results based on the Argonne V18 interaction are presented. Then we consider also the Norfolk NV2-IIa and NV2-IIb chiral EFT interactions. The analysis of the differences between the correlations of the various interactions shows that for momenta between 0 and 500 MeV there are variations of up to 5.9 % for the $nn$ system, of up to 1.8 % for the $np$ system, and of 1.4 % for the $pp$ system.

   ↳ nucl-thnucl-exPLB(2025)·13 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.