Wed·Jul 27, 2022Wednesday·July 27, 2022

1. 01*

   Exclusive dielectron production in ultraperipheral Pb+Pb collisions at $\sqrt{s_{{}_{\text{NN}}}}=5.02$ TeV with ATLAS

   ATLAS Collaboration

   Exclusive production of dielectron pairs, $\gamma \gamma \to e^{+}{e}^{-}$, is studied using ${\mathcal{L}}_{\mathrm{int}}=1.72\mathrm{n}{\mathrm{b}}^{-1}$ of data from ultraperipheral collisions of lead nuclei at $\sqrt{s_{{}_{\text{NN}}}}=5.02$ TeV recorded by the ATLAS detector at the LHC. The process of interest proceeds via photon-photon interaction in the strong electromagnetic fields of relativistic lead nuclei. Dielectron production is measured in the fiducial region defined by following requirements: electron transverse momentum, $p_{\text{T}}^e>2.5$ GeV, absolute electron pseudorapidity, $|{\eta }^e|<2.5$, invariant mass of the dielectron system, $m_{ee}>5$ GeV, and transverse momentum of the dielecton pair, $p_{\text{T}}^{ee}<2$ GeV. Differential cross-sections are measured as a function of $m_{ee}$, average $p_{\text{T}}^e$, absolute rapidity of the dielectron system, $|y_{ee}|$, and scattering angle in the dielectron rest frame, $|\cos {\theta }^{\ast }|$ in the inclusive sample, and also under the requirement of no activity in the forward direction. The total integrated fiducial cross-section is measured to be $215\pm 1{\text{(stat.)}}_{-20}^{+23}\text{(syst.)}\pm 4\text{(lumi.)}\mu$b. Within experimental uncertainties the measured integrated cross-section is in good agreement with the QED predictions from the Monte Carlo programs Starlight and SuperChic, confirming the broad features of the initial photon fluxes. The differential cross-sections show systematic differences with these predictions which are more pronounced at high $|y_{ee}|$ and $|\cos {\theta }^{\ast }|$ values.

   nucl-exJHEP(2023)·53 citations
2. 02*

   Unveiling the dynamics of nucleosynthesis in relativistic heavy-ion collisions

   Kai-Jia Sun🇺🇸 · Rui Wang🇨🇳 · Che Ming Ko🇺🇸 · Yu-Gang Ma🇨🇳 · Chun Shen🇺🇸

   Like nucleosynthesis during the early universe, light nuclei are also produced in relativistic heavy-ion collisions. Although the deuteron ($d$) yields in these collisions can be well described by the statistical hadronization model (SHM), which assumes that particle yields are fixed at a common chemical freezeout near the phase boundary between the quark-gluon plasma and the hadron gas, the recently measured triton (${}^3\text{H}$) yields in Au+Au collisions at $\sqrt{s_{NN}}=7.7-200$ GeV are overestimated systematically by this model. Here, we develop a comprehensive kinetic approach to study the effects of hadronic re-scatterings, such as $\pi NN\leftrightarrow \pi d$ and $\pi NNN\leftrightarrow {\pi }^3\text{H}{(}^3\text{He})$, on $d$, ${}^3\text{H}$, and ${}^3\text{He}$ production in these collisions. We find that these reactions have little effects on the deuteron yield but reduce the ${}^3\text{H}$ and ${}^3\text{He}$ yields by about a factor of 1.8 from their initial values given by the SHM. This finding helps resolve the overestimation of triton production in the SHM and provides the evidence for hadronic re-scattering effects on nucleosynthesis in relativistic heavy-ion collisions.

   ↳ nucl-thnucl-exNature Commun.(2024)·66 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.