We study the deuteron production via the deuteron pion and nucleon catalysis reactions, $\pi pn\leftrightarrow \pi d$ and $Npn\leftrightarrow Nd$, by employing stochastic multiparticle reactions in the hadronic transport approach SMASH for the first time. This is an improvement compared to previous studies, which introduced an artificial fake resonance $d^{\prime }$ to simulate these $3\leftrightarrow 2$ reactions as a chain of $2\leftrightarrow 2$ reactions. The derivation of the stochastic criterion for multiparticle reactions is presented in a comprehensive fashion and its implementation is tested against an analytic expression for the scattering rate and the equilibrating particle yields in box calculations. We then study Au $+$ Au collisions at $\sqrt{s_{NN}}=7.7$ GeV, where we find that multiparticle collisions substantially reduce the time required for deuterons to reach partial chemical equilibrium with nucleons. Subsequently, the final yield of $d$ is practically independent from the number of $d$ at particlization, confirming the results of previous studies. The mean transverse momentum and the integrated elliptic flow as a function of centrality are rather insensitive to the exact realization of the $2\leftrightarrow 3$ reactions.

Hadron femtoscopy has turned into a powerful tool for accessing space-time information of heavy-ion collisions as well as for studying final-state interactions of hadrons. Recently, heavy-flavor femtoscopy has become feasible using the ALICE detector at the LHC. We compute the correlation function of $D$ mesons and light mesons using an off-shell $T$-matrix approach to access the two-meson wave function, and predict the correlation functions involving charged $D^{+},D^{*+},D_s^{+}$, and $D_s^{*+}$ with ${\pi }^{\pm }$ and $K^{\pm }$. From the obtained results—all of them accessible in $p+p$ collision experiments—we point up the case of $D^{+}{\pi }^{-}$, which is sensitive to the lower state of the two-pole $D_0^{*}(2300)$ system. The presence of such poles imprints a depletion on the correlation function, which could potentially be detected in experiments. While preliminary ALICE data do not show evidence of this effect, we suggest to look into the $D_s^{+}{K}^{-}$ system to explore the higher pole of the $D_0^{*}(2300)$, as the depletion in the correlation function is more pronounced. Using heavy-quark spin symmetry we also propose exploring the effect of the two poles of the $D_1(2430)$ and predict similar structures in the correlation functions of the $D^{*+}{\pi }^{-}$ and $D_s^{*+}{K}^{-}$ pairs.

We study clustering of baryons at the freeze-out point of relativistic heavy-ion collisions. Using a Walecka-Serot model for the nucleon-nucleon ($NN$) interaction we analyze how the modified critical $\sigma$ mode—responsible for the $NN$ attraction—allows for clustering of nucleons when the system is close to a possible critical point of QCD. We investigate clusters of few nucleons, and also the internal cluster configuration when the system is long lived. For realistic heavy-ion collisions we study to what extent light clusters, such as ${}^4\mathrm{He}$, can be formed in several $\mathrm{fm}/c$, and perform the statistical analysis of proton cumulants and higher-order moments (skewness and kurtosis) for collisions at the beam energy scan of the Relativistic Heavy-Ion Collider.

We show that the on-shell effective theory (OSEFT) is the quantum field theory counterpart of a Foldy-Wouthuysen diagonalization of relativistic quantum mechanics for massless fermions. Thus, it is free of the Zitterbewegung oscillations that would yield an ill-defined meaning to the semiclassical transport approach at short distances if derived from the pure Dirac picture. We present a detailed derivation of the collision terms in the chiral kinetic theory using the OSEFT. Collision integrals are derived up to order $1/E$, where $E$ is the energy of an on-shell fermion. At this order, the collision terms depend on the spin tensor of the fermion, and in the presence of chiral imbalance, it describes how a massless fermion of a given helicity interacts differently with the transverse photons of different circular polarization. In order to back up our results, we check that they allow us to reproduce the fermion decay rate in an ultradegenerate plasma with a chiral imbalance computed directly from QED.

Vacuum and thermal properties of pseudoscalar and vector charm mesons are analyzed within a self-consistent many-body approach, employing a chiral effective field theory that incorporates heavy-quark spin symmetry. Upon unitarization of the vacuum interaction amplitudes for the scattering of charm mesons off light mesons in a fully coupled-channel basis, new dynamically generated states are searched. The imaginary-time formalism is employed to extend the calculation to finite temperatures up to $T=150\mathrm{MeV}$. Medium-modified spectral shapes of the $D$, $D^{*}$, $D_s$, and $D_s^{*}$ mesons are provided. The temperature dependence of the masses and decay widths of the nonstrange $D_0^{*}(2300)$ and $D_1^{*}(2430)$ mesons, both showing a double-pole structure in the complex-energy plane, is also reported, as well as that of the $D_{s0}^{*}(2317)$ and $D_{s1}^{*}(2460)$ resonances and other states not yet identified experimentally. Being the first calculation incorporating open-charm vector mesons at finite temperature in a self-consistent fashion, it brings up the opportunity to discuss the medium effects on the open-charm sector under the perspective of chiral and heavy-quark spin symmetries.