Juan M. Torres-Rincon

We compute the charm-quark current–current correlation function within the Langevin framework and extract the heavy-quark diffusion coefficient using the Green–Kubo formula. The formalism is further extended to evaluate the correlation function using a generalized Langevin equation that incorporates memory effects via an exponentially decaying memory kernel. We find that while memory effects qualitatively modify the transient structure of the current correlations, the value of the transport coefficient remains unchanged. In addition, we investigate heavy-quark thermalization in the presence of memory and compare the nonequilibrium solution of a generalized Fokker–Planck equation with the one obtained from the generalized Langevin equation in the nonrelativistic limit. We also consider the relativistic case with correlated noise and observe that memory effects can give rise to a damped, oscillatory equilibration of the heavy-quark momentum distribution in a non-Markovian bath.

The capability of the ALICE@LHC and STAR@RHIC experiments to reconstruct D mesons has enabled femtoscopic correlation measurements of open-charm mesons in both small and large systems. In this work, we present a theoretical calculation of the correlation functions of D and D ¯ mesons with nucleons, based on the Koonin-Pratt formalism. We employ an effective Lagrangian to model the interaction between charmed mesons and baryons and apply the TROY formalism to obtain the off-shell T -matrix in coupled channels, incorporating the effect of the Coulomb interaction when the pair involves two charged particles. The resulting full coupled-channel wave function is inserted into the Koonin-Pratt equation with channel weights derived from a thermal model. Additionally, we compute the correlation functions using the Lednický-Lyuboshitz approximation with low-energy scattering parameters extracted from the unitarized amplitudes. We compare these two approaches and provide predictions for different correlated pairs. Our results can be tested against current and future experimental data from the ALICE and STAR Collaborations in both proton-proton and heavy-ion collisions.

We have performed a theoretical study of the correlation functions of K − d and K + d pairs and compared them with those provided by the ALICE Collaboration from Pb-Pb collisions and also from high-multiplicity p-p collisions in the case of K + d . In addition to implementing the effect of the Coulomb force, the K − d and K + d wave functions are derived from the corresponding strong scattering amplitudes that are built employing a unitarized chiral model for the elementary K − N and K + N interactions. We present results for the impulse approximation, which accounts for single-scattering processes of the kaon with the nucleons of the deuteron, as well as for the solution of the Faddeev equations in the so-called fixed center approximation, which includes multiple rescattering effects. The K − d correlation function is shown to be very sensitive to both the size of the source and the relative momentum of the interacting pair, with large deviations from the Coulomb baseline and sizable multistep scattering contributions, effects that are tied to a K ¯ N strong interaction that is dominated by the influence of the subthreshold resonance Λ ( 1405 ) . In contrast, the K + d correlation function only differs appreciably from the Coulomb one for relatively small sources, reflecting the mildly repulsive and elastic behavior of the K N strong force. The calculated correlation functions are found to nicely reproduce the experimental data of the ALICE Collaboration. Our study serves to reinforce the validity of the theoretical models employed and demonstrates the value of femtoscopy as a powerful tool for probing hadronic interactions involving strangeness.

The femtoscopic D D ¯ correlation functions are investigated to predict the signature of the not-yet-established X ( 3700 ) state. Here it is interpreted as a bound state generated by solving the coupled-channel Bethe-Salpeter equations with the local hidden-gauge formalism. We prospect how the relevant properties and observables characterizing this state—like the pole position, scattering lengths and compositeness—might be affected by the variation of the parameters of the model. The amplitudes are then used as input into the momentum correlation functions of the D 0 D ¯ 0 and D + D − pairs. We discuss how their behaviors encode the features of the X ( 3700 ) state.

We present a microscopic dynamical model to study the formation, dissociation, and recombination processes of charmonium states in a heat bath at constant temperature and volume. Within this classical approach, heavy quarks are described as Brownian particles in a background medium of light constituents and can therefore be modeled by a Fokker-Planck equation with constant transport coefficients, which is then implemented through relativistic Langevin simulations. The heavy quarks interact classically via a Coulomb-like screened potential to form a bound state if the relative energy of the pair becomes negative. Dissociation of bound states is possible as a result of screening effects on the potential as well as through scatterings with plasma particles. We demonstrate the full equilibration of the system and show that the resulting equilibrium charmonium yields are in accordance with the Statistical Hadronization Model.

We have generated an updated version of the pΩ potential for low-energy interactions based on an effective field theory approach at leading order. This potential, together with other potentials based either on different parametrizations or lattice QCD calculations, have been used to solve the Schrödinger equation numerically, obtaining the scattering wave functions for different values of the relative momentum. Using these wave functions, we have computed the pΩ femtoscopic correlation functions, comparing the results with those published by the ALICE collaboration.