Tue·Dec 1, 2020Tuesday·December 1, 2020

1. 01*

   Comment on "Transverse Wobbling in ${}^{135}$Pr [Phys. Rev. Lett. 114, 082501 (2015)]"

   S. Guo🇨🇳

   In [J. T. Matta et al., Phys. Rev. Lett. 114, 082501 (2015)] a transverse wobbling band was reported in ${}^{135}$Pr. The critical experimental proof for this assignment is the E2 dominated linking transitions between the wobbling and normal bands, which are supported by two experiments performed with Gammasphere and INGA. However, the M1 dominated character cannot be excluded based on the reported experimental information, indicating that the wobbling assignment is still questionable.

   nucl-ex2 citations
2. 02*

   Comment on "Longitudinal wobbling in ${}^{133}$La [Eur. Phys. J. A 55, 159 (2019)]"

   W. Hua🇨🇳 · S. Guo🇨🇳 · C. M. Petrache🇫🇷

   In [S. Biswas et al., Eur. Phys. J. A 55, 159 (2019)] a longitudinal wobbling band was reported in ${}^{133}$La. The critical experimental proof for this assignment is the E2 dominated linking transitions between the wobbling and normal bands, which are supported by angular distribution and linear polarization measurements. However, severe problems are found in the reported experimental information, indicating that the assignment of wobbling band was not firmly established.

   nucl-ex2 citations
3. 03*

   Form Factors of the Nucleon Axial Current

   Chen Chen🇩🇪 · Christian S. Fischer🇩🇪 · Craig D. Roberts🇨🇳 · Jorge Segovia🇪🇸

   A symmetry-preserving Poincaré-covariant quark+diquark Faddeev equation treatment of the nucleon is used to deliver parameter-free predictions for the nucleon's axial and induced pseudoscalar form factors, $G_A$ and $G_P$, respectively. The result for $G_A$ can reliably be represented by a dipole form factor characterised by an axial charge $g_A=G_A(0)=1.25(3)$ and a mass-scale $M_A=1.23(3)m_N$, where $m_N$ is the nucleon mass; and regarding $G_P$, the induced pseudoscalar charge $g_p^{\ast }=8.80(23)$, the ratio $g_p^{\ast }/g_A=7.04(22)$, and the pion pole dominance Ansatz is found to provide a reliable estimate of the directly computed result. The ratio of flavour-separated quark axial charges is also calculated: $g_A^d/g_A^u=-0.16(2)$. This value expresses a marked suppression of the size of the $d$-quark component relative to that found in nonrelativistic quark models and owes to the presence of strong diquark correlations in the nucleon Faddeev wave function -- both scalar and axial-vector, with the scalar diquark being dominant. The predicted form for $G_A$ should provide a sound foundation for analyses of the neutrino-nucleus and antineutrino-nucleus cross-sections that are relevant to modern accelerator neutrino experiments.

   ↳ hep-phhep-exhep-latnucl-ex+1PLB(2021)·32 citations
4. 04*

   Fusion reaction of a weakly-bound nucleus with a deformed target

   Ki-Seok Choi · K. S. Kim🇰🇷 · Myung-Ki Cheoun🇰🇷 · W. Y. So · K. Hagino🇯🇵

   We discuss the role of deformation of the target nucleus in the fusion reaction of the ${}^{15}$C + ${}^{232}$Th system at energies around the Coulomb barrier, for which ${}^{15}$C is a well-known one-neutron halo nucleus. To this end, we construct the potential between ${}^{15}$C and ${}^{232}$Th with the double folding procedure, assuming that the projectile nucleus is composed of the core nucleus, ${}^{14}$C, and a valance neutron. By taking into account the halo nature of the projectile nucleus as well as the deformation of the target nucleus, we simultaneously reproduce the fusion cross sections for the ${}^{14}$C + ${}^{232}$Th and the ${}^{15}$C + ${}^{232}$Th systems. Our calculation indicates that the net effect of the breakup and the transfer channels is small for this system.

   ↳ nucl-thnucl-exPRC(2021)·6 citations
5. 05*

   Charged-particle multiplicity dependence of charm-baryon-to-meson ratio in high-energy proton-proton collisions

   Yu Chen🇨🇳 · Min He🇨🇳

   We propose that the charged-particle multiplicity dependence of the charm-baryon-to-meson ratio observed in high-energy $pp$ collisions can be explained by canonical treatment of quantum charges in the statistical hadronization model (SHM). Taking the full particle listings of PDG complemented by additional charm-baryon states from relativistic quark model predictions, we evaluate the canonical partition function and the charm-hadron chemical factors that measure the canonical suppression arising from the requirement of strict conservation of quantum charges. We demonstrate that, while charm number conservation induces common suppression on the production of both charm-baryons and -mesons, baryon (strangeness) number conservation causes further suppression on charm-baryons (charm-strange mesons) relative to nonstrange charm-mesons, thereby resulting in a decreasing ${\Lambda }_c/D^0$ ($D_s/D^0$) ratio toward smaller multiplicity events. The charm-hadron thermal densities thus computed are then used as pertinent weights to perform charm-quark fragmentation simulations yielding $p_T$-dependent ${\Lambda }_c/D^0$ and $D_s/D^0$ ratios at varying multiplicities in fair agreement with ALICE measurements.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2021)·25 citations
6. 06*

   Probing the nature of the conjectured low-spin wobbling bands in atomic nuclei

   S. Guo🇨🇳 · X. H. Zhou🇨🇳 · C. M. Petrache🇫🇷 · E. A. Lawrie🇿🇦 · S. Mthembu🇿🇦 · Y. D. Fang🇨🇳 · H. Y. Wu🇨🇳 · H. L. Wang · H. Y. Meng🇨🇳 · G. S. Li · Y. H. Qiang🇨🇳 · J. G. Wang and 19 other authors

   Precession is a unique motion in which the orientation of the rotational axis of a rotating body is not fixed but moving, and it generally exists in the Universe from giant stars through tiny atomic nuclei. In principle, the precession of an atomic nuclide can be approximately described as wobbling motion, arising from the coupling of a rotation and a harmonic vibration. Recently, a number of wobbling bands were reported at low spin, which violate the wobbling approximation that can be valid only at high spin. Here we explore the nature of the reported low-spin wobbling bands. Via a new experiment, we demonstrate that one such band in ${}^{187}$Au is generated by dominant single-particle excitation rather than by the excitation of a wobbling phonon. We point out that the imperfect research paradigm used previously would lead to unreliable identification of low-spin wobbling bands. Consequently, new experimental approaches should be developed to distinguish among the different excitation mechanisms that can give rise to the observed low-spin bands in odd-even nuclei.

   ↳ nucl-thnucl-exPLB(2022)·19 citations
7. 07*

   Central exclusive production of charged particle pairs in proton-proton collisions at $\sqrt{s}=200$ GeV with the STAR detector at RHIC

   Rafal Sikora · for the STAR Collaboration

   The measurement of the central exclusive production of charged hadron pairs $h^{+}{h}^{-}$ ($h=\pi ,K,p$) by the STAR experiment at RHIC is reported. The data from proton-proton collisions at $\sqrt{s}=200$ GeV were used in this study. The pairs of charged hadrons produced in the reaction $pp\to p^{\prime }+h^{+}{h}^{-}+p^{\prime }$ were reconstructed from the tracks in the central detector, while the forward-scattered protons were measured in the Roman Pot system. Differential cross sections were measured in the fiducial region determined by the geometrical acceptance of the experimental setup. They were compared to phenomenological predictions based on the Double Pomeron Exchange model. The fiducial ${\pi }^{+}{\pi }^{-}$ cross section was extrapolated to the Lorentz-invariant region, which allowed decomposition of the invariant mass spectrum into continuum and resonant contributions.

   ↳ hep-exnucl-exPoS(2021)·3 citations
8. 08*

   Alpha-induced inelastic scattering and alpha-transfer reactions in ${}^{12}$C and ${}^{16}$O within the Algebraic Cluster Model

   J. Casal🇮🇹 · L. Fortunato🇮🇹 · E. G. Lanza🇮🇹 · A. Vitturi🇮🇹

   The molecular algebraic model based on three and four alpha clusters is used to describe the inelastic scattering of alpha particles populating low-lying states in ${}^{12}$C and ${}^{16}$O. Optical potentials and inelastic formfactors are obtained by folding densities and transition densities obtained within the molecular model. One-step and multi-step processes can be included in the reaction mechanism calculation. In spite of the simplicity of the approach the molecular model with rotations and vibrations provides a reliable description of reactions where $\alpha$-cluster degrees of freedom are involved and good results are obtained for the excitation of several low-lying states. Within the same model we briefly discuss the expected selection rules for the $\alpha$-transfer reactions from ${}^{12}$C and ${}^{16}$O.

   ↳ nucl-thnucl-exEPJA(2021)·13 citations
9. 09*

   Present Status of Nuclear Shell-Model Calculations of Neutrinoless Double-Beta Decay Matrix Elements

   L. Coraggio🇮🇹 · N. Itaco🇮🇹 · G. De Gregorio🇮🇹 · A. Gargano🇮🇹 · R. Mancino🇮🇹 · S. Pastore🇺🇸

   Neutrinoless double beta decay searches are currently among the major foci of experimental physics. The observation of such a decay will have important implications in our understanding of the intrinsic nature of neutrinos and shed light on the limitations of the Standard Model. The rate of this process depends on both the unknown neutrino effective mass and the nuclear matrix element associated with the given neutrinoless double-beta decay transition. The latter can only be provided by theoretical calculations, hence the need of accurate theoretical predictions of the nuclear matrix element for the success of the experimental programs. This need drives the theoretical nuclear physics community to provide the most reliable calculations of the nuclear matrix elements. Among the various computational models adopted to solve the many-body nuclear problem, the shell model is widely considered as the basic framework of the microscopic description of the nucleus. Here, we review the most recent and advanced shell-model calculations of the nuclear matrix elements considering the light-neutrino-exchange channel for nuclei of experimental interest. We report the sensitivity of the theoretical calculations with respect to variations in the model spaces and the shell-model nuclear Hamiltonians.

   ↳ nucl-thhep-exnucl-exUniverse(2020)·15 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.