Production of (anti-)$^3\text{He}$ and (anti-)$^3\text{H}$ in p--Pb collisions at $\sqrt{\textit{s}}_{\mathrm{NN}} = 5.02$ TeV measured with ALICE at the LHC
In high-energy ion collisions, a medium governed by strong interactions is created and can be investigated via the particles produced during the evolution of this medium. Also light (hyper-)nuclei and their antiparticles are produced. The underlying production mechanism is not understood but usually described employing two different types of phenomenological models, the coalescence and the statistical hadronization model. The transverse-momentum differential production yields of (anti-)helium-3 and (anti-)triton measured in proton--lead collisions at a center-of-mass energy per nucleon pair of 5.02 TeV with ALICE at the LHC are presented which complement the measurements in proton--proton and lead--lead collisions. The measurements confirm a smooth evolution of the production yields with the size of the produced medium. For the first time, a direct comparison of statistical hadronization and coalescence model predictions with data is performed for the coalescence parameter and the $^3\text{He}$-to-proton yield ratio. In contrast to the expectation of the coalescence model, the coalescence parameter obtained from the measurement of (anti-)$^3\text{He}$ increases with transverse momentum. A new observable, the $^3\text{H}$-to-$^3\text{He}$ yield ratio, is measured and its capability to distinguish between models is discussed. In addition, an upper limit on the production of $^4\overline{\mathrm{He}}$ nuclei based on the non-observation of candidates is reported.