Tue·Mar 28, 2023Tuesday·March 28, 2023

1. 01*

   Soft dipole resonance in ${}^8$C and its isospin symmetry with ${}^8$He

   Takayuki Myo🇯🇵 · Kiyoshi Kato

   We investigate the soft dipole resonance in the proton-rich nucleus ${}_6^8$C${}_2$, which is a collective dipole oscillation of four valence protons against the $\alpha$ core,and discuss the isospin symmetry with the mirror nucleus ${}_2^8$He${}_6$. We use the $\alpha +N+N+N+N$ five-body cluster model and many-body resonances are obtained using the complex-scaling method. The $1^{-}$ resonance of ${}_6^8$C${}_2$ is confirmed at the excitation energy of 13 MeV with a large decay width of 24 MeV, and its structure is similar to the soft dipole resonance in ${}_2^8$He${}_6$, such as the configuration mixing and the spatial properties. These results indicate a good isospin symmetry in the soft dipole resonances of two nuclei with a common collective excitation of multiproton and multineutron, while the ground states of two nuclei show different properties due to the Coulomb repulsion of valence protons in ${}_6^8$C${}_2$, leading to the symmetry breaking. In conclusion, the appearance of the isospin symmetry differs depending on the states of ${}_6^8$C${}_2$ and ${}_2^8$He${}_6$.

   ↳ nucl-thnucl-exPRC(2023)·5 citations
2. 02*

   Chiral symmetry breaking and the masses of hadrons: a review

   Su Houng Lee🇰🇷

   The masses of hadrons in the vacuum, where the chiral symmetry is restored, and in the medium are in general different even when the changes in the order parameters of chiral symmetry are the same. Here, we first discuss the relation between the hadron masses and the chiral symmetry breaking in approaches based on operator product expansion (OPE). We then discuss what additional changes occur to the hadron masses when going from the chiral symmetry restored vacuum to nuclear medium and/or finite temperature. The work will highlight how we can identify the effects of chiral symmetry restoration from experimental observations.

   ↳ hep-phnucl-exnucl-thSymmetry(2023)·18 citations
3. 03*

   Constraining nuclear symmetry energy with the charge radii of mirror-pair nuclei

   Rong An🇨🇳 · Shuai Sun🇨🇳 · Li-Gang Cao · Feng-Shou Zhang🇨🇳

   The nuclear charge radius plays a vital role in determining the equation of state of isospin asymmetric nuclear matter. Based on the correlation between the differences in charge radii of mirror-partner nuclei and the slope parameter ($L$) of symmetry energy at the nuclear saturation density, an analysis of the calibrated slope parameter $L$ was performed in finite nuclei. In this study, relativistic and non-relativistic energy density functionals were employed to constrain the nuclear symmetry energy through the available databases of the mirror-pair nuclei ${}^{36}$Ca-${}^{36}$S, ${}^{38}$Ca-${}^{38}$Ar, and ${}^{54}$Ni-${}^{54}$Fe. The deduced nuclear symmetry energy was located in the range 29.89-31.85 MeV, and $L$ of the symmetry energy essentially covered the range 22.50-51.55 MeV at the saturation density. Moreover, the extracted $L_s$ at the sensitivity density ${\rho }_s=0.10{\mathrm{fm}}^{-3}$ was located in the interval range 30.52-39.76 MeV.

   ↳ nucl-thhep-exnucl-exNucl.Sci.Tech.(2023)·30 citations
4. 04*

   Thermalization at the femtoscale seen in high-energy Pb+Pb collisions

   Rupam Samanta🇵🇱 · Somadutta Bhatta🇺🇸 · Jiangyong Jia🇺🇸 · Matthew Luzum🇧🇷 · Jean-Yves Ollitrault🇫🇷

   A collision between two atomic nuclei accelerated at a speed close to that of light creates a dense system of quarks and gluons. Interactions among them are so strong that they behave collectively like a droplet of fluid of ten-femtometer size, which expands into the vacuum and eventually fragments into thousands of particles. We report a new manifestation of thermalization in recent data from the Large Hadron Collider. Our analysis is based on results from the ATLAS Collaboration, which has measured the variance of the momentum per particle across Pb+Pb collision events with the same particle multiplicity. This variance decreases steeply over a narrow multiplicity range corresponding to central collisions. We provide a simple explanation of this newly-observed phenomenon: For a given multiplicity, the momentum per particle increases with increasing impact parameter. Since a larger impact parameter goes along with a smaller collision volume, this in turn implies that the momentum per particle increases as a function of density, which is a generic consequence of thermalization. Our analysis provides the first direct evidence of this phenomenon at the femtoscale.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2024)·36 citations
5. 05*

   Charmoniumlike tetraquarks in a chiral quark model

   Gang Yang🇨🇳 · Jialun Ping🇨🇳 · Jorge Segovia🇪🇸

   The lowest-lying charmonium-like tetraquarks $c\bar{c}q\bar{q}$ $(q=u,d)$ and $c\bar{c}s\bar{s}$, with spin-parity $J^P=0^{+}$, $1^{+}$ and $2^{+}$, and isospin $I=0$ and $1$, are systematically investigated within the theoretical framework of complex-scaling range for a chiral quark model that has already been successfully applied in former studies of various tetra- and penta-quark systems. A four-body $S$-wave configuration which includes meson-meson, diquark-antidiquark and K-type arrangements of quarks, along with all possible color wave functions, is comprehensively considered. Several narrow resonances are obtained in each tetraquark channel when a fully coupled-channel computation is performed. We tentatively assign theoretical states to experimentally reported charmonium-like signals such as $X(3872)$, $Z_c(3900)$, $X(3960)$, $X(4350)$, $X(4685)$ and $X(4700)$. They can be well identified as hadronic molecules; however, other exotic components which involve, for instance, hidden-color channels or diquark-antidiquark structures play a considerable role. Meanwhile, two resonances are obtained at $4.04$ GeV and $4.14$ GeV which may be compatible with experimental data in the energy interval $4.0-4.2$ GeV. Furthermore, the $X(3940)$ and $X(4630)$ may be identified as color compact tetraquark resonances. Finally, we also find few resonance states in the energy interval from $4.5$ GeV to $5.0$ GeV, which would be awaiting for discovery in future experiments.

   ↳ hep-phhep-exhep-latnucl-ex+1EPJC(2023)·14 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.