New articles on Nuclear Experiment

[1] 2402.18876

Transverse asymmetry of individual $γ$-rays in the $^{139}$La($\vec{n}$, $γ$)$^{140}$La reaction

The enhancement of the parity-violating asymmetry in the vicinity of $p$-wave compound nuclear resonances was observed for a variety of medium-heavy nuclei. The enhanced parity-violating asymmetry can be understood using the $s$-$p$ mixing model. The $s$-$p$ mixing model predicts several neutron energy-dependent angular correlations between the neutron momentum $\vec k_n$, neutron spin $\vec\sigma_n$, $\gamma$-ray momentum $\vec k_\gamma$, and $\gamma$-ray polarization $\vec\sigma_\gamma$ in the $(n,\gamma)$ reaction. In this paper, the improved value of the transverse asymmetry of $\gamma$-ray emissions, corresponding to a correlation term $\vec{\sigma}_n\cdot(\vec k_n\times\vec k_\gamma)$ in the $^{139}\mathrm{La}(\vec n,\gamma)^{140}\mathrm{La}$ reaction, and the transverse asymmetries in the transitions to several low excited states of $^{140}\mathrm{La}$ are reported.

[2] 2402.18831

A direct probe of $Λ$ potential in nuclear medium

Using the Li\`{e}ge intranuclear-cascade model together with the ablation model ABLA, an investigation is conducted into the effects of $\Lambda$ potential in $\Lambda$-nucleus and $\Lambda$-hypernucleus-nucleus collisions across various beam energies. The findings show that the angle and transverse-momentum distributions of scattered $\Lambda$ hyperon, the scattering cross section of the $\Lambda$ hyperon in $\Lambda$-nucleus collisions as well as the rapidity distribution of $\Lambda$ hyperon in $\Lambda$-hypernucleus-nucleus collisions are significantly influenced by the strength of the $\Lambda$ potential in these scattering reactions across various beam energies. These demonstrations, unhindered by the uncertainties of $\Lambda$ and hypernuclei productions in nuclear medium, allow for a direct investigation of the $\Lambda$ potential, especially its momentum dependence. The criticality of probing the $\Lambda$ potential is closely associated with the resolution of the "hyperon puzzle" in neutron stars.

[3] 2402.19060

Slicing Pomerons in ultraperipheral collisions using forward neutrons from nuclear breakup

We argue that measurements of forward neutrons from nuclear breakup in inclusive high energy photon-nucleus ($\gamma A$) scattering provide a novel complementary way to study small-$x$ dynamics of QCD in heavy-ion ultraperipheral collisions (UPCs). Using the leading twist approximation to nuclear shadowing, we calculate the distribution over the number of evaporation neutrons produced in $\gamma Pb$ collisions at the LHC. We demonstrate that it allows one to determine the distribution over the number of wounded nucleons (inelastic collisions), which constrains the mechanism of nuclear shadowing of nuclear parton distributions.