Fri·Apr 12, 2024Friday·April 12, 2024

1. 01*

   Exclusive four pion photoproduction in ultraperipheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. In particular, it allows for the investigations of excited, light-flavour vector mesons. The measurement of coherently photoproduced ${\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ final states in ultraperipheral Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is presented for the first time. The cross section, d$\sigma$/d$y$, times the branching ratio ($\rho \to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^{-}$) is found to be $47.8\pm 2.3(stat.)\pm 7.7(syst.)$ mb in the rapidity interval $|y|<0.5$. The invariant mass distribution is not well described with a single Breit-Wigner resonance without an interference term. Including interference with a non-resonant contribution results in the mass and width values being too far from those reported in PDG, while the production of two interfering resonances, $\rho (1450)$ and $\rho (1700)$, also provides a good description of the data. The values of the masses ($m$) and widths ($\Gamma$) of the resonances extracted from the fit assuming two interfering resonances are $m_1=1385\pm 14(stat.)\pm 3(syst.)$ MeV/$c^2$, ${\Gamma }_1=431\pm 36(stat.)\pm 82(syst.)$ MeV/$c^2$, $m_2=1663\pm 13(stat.)\pm 22(syst.)$ MeV/$c^2$ and ${\Gamma }_2=357\pm 31(stat.)\pm 49(syst.)$ MeV/$c^2$, respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions.

   nucl-exhep-exPLB(2026)·9 citations
2. 02*

   Multifractal Dimension Spectrum Analysis for Nuclear Density Distribution

   Weihu Ma🇨🇳 · Yu-Gang Ma🇨🇳 · Wanbing He🇨🇳 · Bo Zhou🇨🇳

   We present an integral density method for calculating the multifractal dimension spectrum for the nucleon distribution in atomic nuclei. This method is then applied to analyze the non-uniformity of the density distribution in several typical types of nuclear matter distributions, including the Woods-Saxon distribution, the halo structure and the tetrahedral $\alpha$ clustering. The subsequent discussion provides a comprehensive and detailed exploration of the results obtained. The multifractal dimension spectrum shows remarkable sensitivity to the density distribution, establishing it as an effective tool for studying the distribution of nucleons in nuclear multibody systems.

   ↳ nucl-thnucl-exChaos(2024)·3 citations
3. 03*

   A new scheme for isomer pumping and depletion with high-power lasers

   C.-J. Yang🇷🇴 · K. M. Spohr · M. Cernaianu🇷🇴 · D. Doria · P. Ghenuche🇷🇴 · V. Horny🇫🇷

   We propose a novel scheme for the population and depletion of nuclear isomers. The scheme combines the $\gamma$-photons with energies $\gtrsim 10$ keV emitted during the interaction of a contemporary high-intensity laser pulse with a plasma and one or multiple photon beams supplied by intense lasers. Due to nonlinear effects, two- or multi-photon absorption dominates over the conventional multi-step one-photon process for an optimized gamma flash. Moreover, this nonlinear effect can be greatly enhanced with the help of externally supplied low-energy photons coming from another laser. These low-energy photons act such that the effective cross-section experienced by the $\gamma$-photons becomes tunable, growing with the intensity $I_0$ of the beam. Assuming $I_0\sim 10^{18}$ Wcm${}^{-2}$ for the photon beam, an effective cross-section as large as $10^{-21}$ cm${}^2$ to $10^{-28}$ cm${}^2$ for the $\gamma -$photon can be achieved. Thus, within state-of-the-art 10 PW laser facilities, the yields from two-photon absorption can reach $10^6$ to $10^9$ isomers per shot for selected states that are separated from their ground state by E2 transitions. Similar yields for transitions with higher multipolarities can be accommodated by multi-photon absorption with additional photons provided.

   ↳ nucl-thnucl-exMatter Radiat.Extremes(2025)·6 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.