Fri·Jul 5, 2024Friday·July 5, 2024

1. 01*

   Suppressed Electric Quadrupole Collectivity in ${}^{49}$Ti

   T. J. Gray🇺🇸 · J. M. Allmond🇺🇸 · C. Benetti · C. Wibisono🇺🇸 · L. Baby · A. Gargano🇮🇹 · T. Miyagi🇩🇪 · A. O. Macchiavelli🇺🇸 · A. E. Stuchbery🇦🇺 · J. L. Wood · S. Ajayi🇺🇸 · J. Aragon and 25 other authors

   Single-step Coulomb excitation of ${}^{46,48,49,50}$Ti is presented. A complete set of $E2$ matrix elements for the quintuplet of states in ${}^{49}$Ti, centered on the $2^{+}$ core excitation, was measured for the first time. A total of nine $E2$ matrix elements are reported, four of which were previously unknown. ${}_{22}^{49}$Ti${}_{27}$ shows a $20\%$ quenching in electric quadrupole transition strength as compared to its semi-magic ${}_{22}^{50}$Ti${}_{28}$ neighbour. This $20\%$ quenching, while empirically unprecedented, can be explained with a remarkably simple two-state mixing model, which is also consistent with other ground-state properties such as the magnetic dipole moment and electric quadrupole moment. A connection to nucleon transfer data and the quenching of single-particle strength is also demonstrated. The simplicity of the ${}^{49}$Ti-${}^{50}$Ti pair (i.e., approximate single-$j$ $0f_{7/2}$ valence space and isolation of yrast states from non-yrast states) provides a unique opportunity to disentangle otherwise competing effects in the ground-state properties of atomic nuclei, the emergence of collectivity, and the role of proton-neutron interactions.

   nucl-exnucl-thPLB(2024)·5 citations
2. 02*

   Revealing the nature of yrast states in neutron-rich polonium isotopes

   R. Lică🇷🇴 · A. N. Andreyev🇬🇧 · H. Naïdja🇩🇿 · A. Blazhev🇩🇪 · P. Van Duppen🇧🇪 · B. Andel🇸🇰 · A. Algora🇪🇸 · S. Antalic🇸🇰 · J. Benito🇪🇸 · G. Benzoni🇮🇹 · T. Berry🇬🇧 · M. J. G. Borge🇪🇸 and 34 other authors

   Polonium isotopes having two protons above the shell closure at $Z=82$ show a wide variety of low-lying high-spin isomeric states across the whole chain. The structure of neutron-deficient isotopes up to ${}^{210}$Po ($N=126$) is well established as they are easily produced through various methods. However, there is not much information available for the neutron-rich counterparts for which only selective techniques can be used for their production. We report on the first fast-timing measurements of yrast states up to the 8${}^{+}$ level in ${}^{214,216,218}$Po isotopes produced in the ${\beta }^{-}$ decay of ${}^{214,216,218}$Bi at ISOLDE, CERN. In particular, our new half-life value of 607(14) ps for the 8${}_1^{+}$ state in ${}^{214}$Po is nearly 20 times shorter than the one available in literature and comparable with the newly measured half-lives of 409(16) and 628(25) ps for the corresponding 8${}_1^{+}$ states in ${}^{216,218}$Po, respectively. The measured $B(E2;8_1^{+}\to 6_1^{+})$ transition probability values follow an increasing trend relative to isotope mass, reaching a maximum for ${}^{216}$Po. The increase contradicts the previous claims of isomerism for the $8^{+}$ yrast states in neutron-rich ${}^{214}$Po and beyond. Together with the other measured yrast transitions, the $B(E2)$ values provide a crucial test of the different theoretical approaches describing the underlying configurations of the yrast band. The new experimental results are compared to shell-model calculations using the KHPE and H208 effective interactions and their pairing modified versions, showing an increase in configuration mixing when moving towards the heavier isotopes.

   nucl-exnucl-thPRL(2025)·3 citations
3. 03*

   Analysis of Iterative Deblurring: No Explicit Noise

   Sinethemba Neliswa Mamba (AIMS-RW) · Pawel Danielewicz (Michigan State U and AIMS-RW)🇺🇸

   Iterative deblurring, notably the Richardson-Lucy algorithm with and without regularization, is analyzed in the context of nuclear and high-energy physics applications. In these applications, probability distributions may be discretized into a few bins, measurement statistics can be high, and instrument performance can be well understood. In such circumstances, it is essential to understand the deblurring first without any explicit noise considerations. We employ singular value decomposition for the blurring matrix in a low-count pixel system. A strong blurring may yield a null space for the blurring matrix. Yet, a nonnegativity constraint for images built into the deblurring may help restore null-space content in a high-contrast image with zero or low intensity for a sufficient number of pixels. For low-contrast images, control over null-space content can be achieved through regularization. When regularization is applied, the blurred image is, in practice, restored to one that is still blurred but less than the starting image.

   ↳ math.NAcs.NAhep-exnucl-exOpen Phys.(2025)·1 citation
4. 04*

   Three-dimensional Imaging of Pion using Lattice QCD: Generalized Parton Distributions

   Heng-Tong Ding🇨🇳 · Xiang Gao🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Qi Shi🇨🇳 · Sergey Syritsyn🇺🇸 · Yong Zhao🇺🇸

   In this work, we report a lattice calculation of $x$-dependent valence pion generalized parton distributions (GPDs) at zero skewness with multiple values of the momentum transfer $-t$. The calculations are based on an $N_f=2+1$ gauge ensemble of highly improved staggered quarks with Wilson-Clover valence fermion. The lattice spacing is 0.04 fm, and the pion valence mass is tuned to be 300 MeV. We determine the Lorentz-invariant amplitudes of the quasi-GPD matrix elements for both symmetric and asymmetric momenta transfers with similar values and show the equivalence of both frames. Then, focusing on the asymmetric frame, we utilize a hybrid scheme to renormalize the quasi-GPD matrix elements obtained from the lattice calculations. After the Fourier transforms, the quasi-GPDs are then matched to the light-cone GPDs within the framework of large momentum effective theory with improved matching, including the next-to-next-to-leading order perturbative corrections, and leading renormalon and renormalization group resummations. We also present the 3-dimensional image of the pion in impact-parameter space through the Fourier transform of the momentum transfer $-t$.

   ↳ hep-lathep-phnucl-exnucl-thJHEP(2025)·38 citations
5. 05*

   Examination of the evidence for a proton halo in ${}^{22}$Al

   K. Y. Zhang🇨🇳 · C. Pan🇨🇳 · Sibo Wang🇨🇳

   More and more halo nuclei or candidates have been identified or suggested in experiments in recent years. It was declared that the halo structure of ${}^{22}$Al is revealed by the large isospin asymmetry in ${}^{22}$Si/${}^{22}$O mirror Gamow-Teller transitions [Phys. Rev. Lett. 125, 192503 (2020)]. We highlight that a significant mirror asymmetry already exists between wave functions of the likely unbound nucleus ${}^{22}$Si and the doubly-magic nucleus ${}^{22}$O, which largely explains the observed asymmetry in the transitions. Furthermore, these transitions involve only the $1^{+}$ excited states of the daughter nuclei ${}^{22}$Al and ${}^{22}$F. The $1^{+}$ state of ${}^{22}$Al cannot be considered a halo state due to its proton-unbound nature. An analysis of the spin-parity suggests that a weakly bound $2s_{1/2}$ valence proton in the ground state of ${}^{22}$Al is improbable. To investigate the shell structure for the ground state of ${}^{22}$Al, we employ the state-of-the-art deformed and triaxial relativistic Hartree-Bogoliubov theories in continuum. We find that a small $s$-wave component of $5\%$ appears for the weakly bound valence proton in ${}^{22}$Al only when triaxial deformation is considered. While the examination of densities and rms radii indicates that this small $s$-wave component is insufficient to form a discernible proton halo in ${}^{22}$Al, slightly larger $2s_{1/2}$ occupations have been reported in other recent theoretical results. The question of how many low-$\ell$ components are sufficient to form a proton halo in the presence of the Coulomb barrier remains open. Thus, future measurements of reaction or interaction cross sections and momentum distributions of breakup fragments are highly desirable to verify whether ${}^{22}$Al is a halo nucleus.

   ↳ nucl-thnucl-exPRC(2024)·25 citations
6. 06*

   Role of clustered nuclear geometry in particle production through p-C and p-O collisions at the Large Hadron Collider

   Aswathy Menon K R🇮🇳 · Suraj Prasad🇮🇳 · Neelkamal Mallick🇮🇳 · Raghunath Sahoo🇮🇳

   Long-range multi-particle correlations in heavy-ion collisions have shown conclusive evidence of the hydrodynamic behavior of strongly interacting matter and are associated with the final-state azimuthal momentum anisotropy. In small collision systems, azimuthal anisotropy can be influenced by the hadronization mechanism and residual jet-like correlations. Thus, one of the motives of the planned p--O and O--O collisions at the LHC and RHIC is to understand the origin of small system collectivity. As the anisotropic flow coefficients ($v_n$) are sensitive to the initial-state effects including nuclear shape, deformation, and charge density profiles, studies involving ${}^{12}$C and ${}^{16}$O nuclei are transpiring due to the presence of exotic $\alpha$ (${}^4$He) clusters in such nuclei. In this study, for the first time, we investigate the effects of nuclear $\alpha$--clusters on the azimuthal anisotropy of the final-state hadrons in p--C and p--O collisions at $\sqrt{s_{\mathrm{NN}}}=9.9$~TeV within a multi-phase transport model framework. We report the transverse momentum ($p_{\mathrm{T}}$) and pseudorapidity ($\eta$) spectra, participant eccentricity (${ϵ}_2$) and triangularity (${ϵ}_3$), and estimate the elliptic flow ($v_2$) and triangular flow ($v_3$) of the final-state hadrons using the two-particle cumulant method. These results are compared with a model-independent Sum of Gaussians (SOG) type nuclear density profile for ${}^{12}$C and ${}^{16}$O nuclei.

   ↳ nucl-thhep-exhep-phnucl-exEPJA(2025)·10 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.