Thu·Aug 15, 2024Thursday·August 15, 2024

1. 01*

   Experimental signatures of a new channel of the DD reaction at very-low energy

   R. Dubey🇿🇦 · K. Czerski · Gokul Das H · A. Kowalska · N.Targosz-Sleczka · M. Kaczmarski · M. Valat

   The discovery of a new, strong reaction channel of the deuteron-deuteron fusion at very low energies might have major consequences for the construction of a future clean and efficient energy source. Following the first theoretical and experimental indications for the existence of the deuteron-deuteron threshold resonance in the ${}^4$He nucleus and its dominant decay by the internal $e^{+}{e}^{-}$ pair creation, we present here an extensive experimental study confirming emission of high-energy electrons and positrons. A simultaneous use of Si charged particle detectors of different thicknesses and large volume NaI(Tl) and HPGe detectors has allowed for the first time to determine the branching ratio between emitted protons, neutrons and $e^{+}{e}^{-}$ pairs for deuteron energies down to 5 keV. The high-energy positrons could be unambiguously detected by their bremsstrahlung spectra and annihilation radiation, supported by the Monte Carlo Geant4 simulations. The theoretical calculations, based on a destructive interference between the threshold resonance and the known broad resonance in ${}^4$He, agree very well with experimentally observed increase of branching ratios for lowering projectile energies. The partial width of the threshold resonance for the $e^{+}{e}^{-}$ pair creation should be at least 10 times larger than that of the proton channel.

   nucl-exPRX(2025)·4 citations
2. 02*

   Study of the Log-third-difference method for the computation of even-odd staggering in fission yields

   Belén Montenegro Viñas · Manuel Caamaño🇪🇸

   The even-odd staggering in fission fragments yield distributions is an important observable to address the role of intrinsic excitations in the fission process. However, its computation as a function of the fragment split is an ill-posed problem that is usually solved through certain assumptions. Arguably, the most widely used method for its computation is the Log-third-difference method, which assumes an underlying local Gaussian distribution. Experimental data of the even-odd effect show sharp features and peaks that are a challenge for the Log-third difference method (or any method for that matter). This paper presents a detailed study of the performance of the Log-third difference method and describes three strategies for improving the precision and accuracy around these sharp features. The best results are obtained with an iterative application of the method and with the use of a multi-Gaussian fit. In regions with a smooth behaviour, the direct application of the Log-third-difference method remains the best option.

   ↳ nucl-thnucl-exEPJA(2024)·0 citations
3. 03*

   Dihadron azimuthal asymmetry and light-quark dipole moments at the Electron-Ion Collider

   Xin-Kai Wen🇨🇳 · Bin Yan🇨🇳 · Zhite Yu🇺🇸 · C.-P. Yuan🇺🇸

   We propose a novel method to probe light-quark dipole moments by examining the azimuthal asymmetries between a collinear pair of hadrons in semi-inclusive deep inelastic lepton scattering off an unpolarized proton target at the Electron-Ion Collider. These asymmetries provide a means to observe transversely polarized quarks, which arise exclusively from the interference between the dipole and the Standard Model interactions, thereby depending linearly on the dipole couplings. We demonstrate that this novel approach can enhance current constraints on light-quark dipole operators by an order of magnitude, free from contamination of other new physics effects. Furthermore, it allows for a simultaneous determination of both the real and imaginary parts of the dipole couplings, offering a new avenue for investigating potential $CP$-violating effects at high energies.

   ↳ hep-phhep-exnucl-exnucl-thSCPMA(2026)·31 citations
4. 04*

   Survival Probabilities of Compound Superheavy Nuclei Towards Element 119

   Yu Qiang🇨🇳 · Xiang-Quan Deng · Yue Shi🇨🇳 · C.Y. Qiao · Junchen Pei🇨🇳

   To synthesize superheavy element 119 is becoming highly concerned as several experimental projects in major laboratories are being pursued. This work studied the survival probabilities of compound superheavy nuclei after multiple neutron emissions based on microscopic energy dependent fission barriers, demonstrating a significant role of triaxial deformation in decreasing the first fission barriers in the heaviest region. Together with the fusion cross sections by the dinuclear system model, the optimal energy and the residual cross section of ${}^{243}$Am(${}^{48}$Ca, 3$n$)${}^{288}$Mc are reproduced. Finally the cross sections and optimal beam energies of ${}^{243}$Am+${}^{54}$Cr and ${}^{249}$Bk+${}^{50}$Ti reactions are estimated, providing clues for the synthesis of new elements.

   ↳ nucl-thnucl-exPLB(2024)·3 citations
5. 05*

   Anti-flow of Mesons in the High Baryon Density Region

   Zuo-Wen Liu🇨🇳 · Shusu Shi🇨🇳

   The E895 and STAR experiments demonstrate that the slopes of directed flow with respect to rapidity ($d{v}_1/dy{|}_{y=0}$) of mesons are negative in the low transverse momentum ($p_T$) region, $p_T<0.8$ GeV/$c$, in Au + Au collisions at $\sqrt{s_{NN}}=3.0-3.9$ GeV. Using the transport model JAM, we investigate the directed flow of ${\pi }^{\pm }$, $K^{\pm }$, and $K^0$ as functions of rapidity, $p_T$, and collision energy in Au + Au collisions at the same energies as those in the E895 and STAR experiments. We find that the JAM model can qualitatively reproduce the anti-flow of $K_S^0$ observed in the E895 experiment. The $v_1$ slopes of pions and kaons are analyzed as functions of the $p_T$ window, revealing a strong $p_T$ dependence of the $v_1$ slopes. Negative $v_1$ slopes are observed in the low $p_T$ region, $p_T<0.8$ GeV/$c$, while positive slopes are shown in the higher $p_T$ region. We find that the shadowing effect from spectators is crucial in generating the anti-flow of mesons at low $p_T$ in the high baryon density region.

   ↳ nucl-thnucl-exPRC(2024)·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.