Mon·Dec 23, 2019Monday·December 23, 2019

1. 01*

   Early signal of emerging nuclear collectivity in neutron-rich ${}^{129}$Sb

   T.J. Gray🇦🇺 · J.M. Allmond🇺🇸 · A.E. Stuchbery🇦🇺 · C.-H. Yu🇺🇸 · C. Baktash · A. Gargano🇮🇹 · A. Galindo-Uribarri🇺🇸 · D.C. Radford🇺🇸 · J.C. Batchelder🇺🇸 · J.R. Beene · C.R. Bingham · L. Coraggio🇮🇹 and 11 other authors

   Radioactive ${}^{129}$Sb, which can be treated as a proton plus semi-magic ${}^{128}$Sn core within the particle-core coupling scheme, was studied by Coulomb excitation. Reduced electric quadrupole transition probabilities, $B(E2)$, for the $2^{+}$ $\times$ $\pi g_{7/2}$ multiplet members and candidate $\pi d_{5/2}$ state were measured. The results indicate that the total electric quadrupole strength of ${}^{129}$Sb is a factor of 1.39(11) larger than the ${}^{128}$Sn core, which is in stark contrast to the expectations of the empirically successful particle-core coupling scheme. Shell-model calculations performed with two different sets of nucleon-nucleon interactions suggest that this enhanced collectivity is due to constructive quadrupole coherence in the wavefunctions stemming from the proton-neutron residual interactions, where adding one nucleon to a core near a double-shell closure can have a pronounced effect. The enhanced electric quadrupole strength is an early signal of the emerging nuclear collectivity that becomes dominant away from the shell closure.

   nucl-exnucl-thPRL(2020)·22 citations
2. 02*

   (Anti-)(hyper-)nuclei production in Pb-Pb collisions with ALICE at the Large Hadron Collider

   Stefano Trogolo🇮🇹

   In ultra-relativistic heavy-ion collisions a great variety of (anti-)(hyper-)nuclei are produced, namely deuteron, triton, ${}^3$He, ${}^4$He, hypertriton (${}_{\Lambda }^3$H) and their antiparticles. The ALICE experiment is the most suited to investigate the production of (hyper-)nuclei at the LHC, thanks to an excellent particle identification and low-material budget detectors. Recent results on (hyper-)nuclei production as a function of transverse momentum ($p_{\mathrm{T}}$) and charged particle multiplicity (d$N_{\mathrm{ch}}$/d$\eta$) in Pb-Pb collisions are presented. The evolution of the production yields with the system size is also shown, via comparison to the results obtained in small collision systems, like pp and p-Pb. The results on the production of (hyper-)nuclei are also compared with the predictions based on a naive coalescence approach and the statistical hadronization models Furthermore, the latest and currently most precise measurement of the hypertriton lifetime is presented. It is compared with results obtained by different experimental techniques and with theoretical predictions.

   nucl-ex0 citations
3. 03*

   Data-driven study of timelike Compton scattering

   O. Grocholski🇵🇱 · H. Moutarde🇫🇷 · B. Pire🇫🇷 · P. Sznajder🇵🇱 · J. Wagner🇵🇱

   In the framework of collinear QCD factorization, the leading twist scattering amplitudes for deeply virtual Compton scattering (DVCS) and timelike Compton scattering (TCS) are intimately related thanks to analytic properties of leading and next-to-leading order amplitudes. We exploit this welcome feature to make data-driven predictions for TCS observables to be measured in near future experiments. Using a recent extraction of DVCS Compton form factors from most of the existing experimental data for that process, we derive TCS amplitudes and calculate TCS observables only assuming leading-twist dominance. Artificial neural network techniques are used for an essential reduction of model dependency, while a careful propagation of experimental uncertainties is achieved with replica methods. Our analysis allows for stringent tests of the leading twist dominance of DVCS and TCS amplitudes. Moreover, this study helps to understand quantitatively the complementarity of DVCS and TCS measurements to test the universality of generalized parton distributions, which is crucial e.g. to perform the nucleon tomography.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2020)·31 citations
4. 04*

   Constraining resonance properties through kaon production in pion-nucleus collisions at low energies

   Vinzent Steinberg🇩🇪 · Jan Steinheimer🇩🇪 · Hannah Elfner🇩🇪 · Marcus Bleicher🇩🇪

   Hadronic interactions are crucial for the dynamical description of heavy-ion reactions at low collision energies and in the late dilute stages at high collision energies. In particular, the properties and decay channels of resonances are an essential ingredient of hadronic transport approaches. The HADES collaboration measured particle production in collisions of pions with carbon and tungsten nuclei at $E_{\text{kin}}=1.7\text{GeV}$. Such reactions are of high interest, because they allow to probe the properties of baryonic resonances produced in a much cleaner environment than the usual nucleus-nucleus collisions. We study these reactions with two transport approaches: SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) and UrQMD (Ultra relativistic Quantum Molecular Dynamics) which follow the same underlying concept but with different implementations. The differential spectra in rapidity and transverse momentum are used to show how model parameters, as the decay channels of high mass resonances and angular distributions of kaon elastic scattering, can be constrained. It is found that the data favor the production of more particles with lower momentum over the production of few particles with higher momentum in these decays. In addition, the shape of the rapidity distribution of the kaons strongly depends on the angular distribution of the elastic kaon-nucleon cross section.

   ↳ nucl-thhep-phnucl-exJ.Phys.G(2021)·10 citations
5. 05*

   Isobaric-multiplet mass equation in a macroscopic-microscopic approach

   Oleg Klochko · Nadezda A. Smirnova🇫🇷

   We study the a, b and c coefficients of the isobaric-multiplet mass equation using a macroscopic-microscopic approach developed by P. Moeller and his collaborators in ADNDT 59, 185 (1995) and ADNDT 109-110, 1 (2016). We show that already the macroscopic part of the finite-range liquid-drop model (FRLDM) describes the general trend of the a and b coefficients relatively well, while the staggering behavior of b coefficients for doublets and quartets can be understood in terms of the difference of average proton and neutron pairing energies. The sets of isobaric masses, predicted by the full macroscopic-microscopic approaches, are used to explore the general trends of IMME coefficients up to A=100. We conclude that while the agreement for a coefficients is quite satisfactory, the global approaches have less sensitivity to predict the staggering pattern observed for b coefficients of doublets and quartets. The best set of theoretical b coefficients for multiplets up to about A=100 is used to predict masses of proton-rich nuclei based on the known experimental masses of neutron-rich mirror partners, and subsequently to investigate their one- and two-proton separation energies. The estimated position of the proton-drip line is in fair agreement with known experimental data. These masses are important for simulations of the astrophysical rp-process.

   ↳ nucl-thnucl-exPRC(2021)·12 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.