Abstract
In this work we study contributions due to vector and axial-vector meson fluctuations to their in-medium spectral functions in an effective low-energy theory inspired by the gauged linear sigma model. In particular, we show how to describe these fluctuations in the effective theory by massive (axial-)vector fields in agreement with the known structure of analogous single-particle or resonance contributions to the corresponding conserved currents. The vector and axial-vector meson spectral functions are then computed by numerically solving the analytically continued functional renormalization group flow equations for their retarded two-point functions at finite temperature and density in the effective theory. We identify the new contributions that arise due to the (axial-)vector meson fluctuations, and assess their influence on possible signatures of a QCD critical end point and the restoration of chiral symmetry in thermal dilepton spectra.
Highlights
Understanding the phases of strong-interaction matter and the transitions between them is still one of the main goals in theoretical and experimental heavy-ion physics [1,2,3,4]
A rather simple improvement of the unphysically large two-particle thresholds involving decays into ρ and a1 can be obtained by giving up the unified treatment of scalar andvector mesons in the following way: We use the Euclidean input evaluated at the k-dependent minimum σ0;k of the scale-dependent effective potential as we did for the flow of the mass parameters in the last subsection, when solving the analytically continued functional renormalization group (aFRG) flow equations for the ρ and a1 two-point functions Γðρ2=Þa;1RðωÞ
In this paper we have presented our results from computing in-medium vector and axial-vector meson spectral functions within an effective chirally gauged low-energy theory
Summary
Understanding the phases of strong-interaction matter and the transitions between them is still one of the main goals in theoretical and experimental heavy-ion physics [1,2,3,4]. For technical reasons, applications to full QCD [22,23] are nowadays often used to motivate effective low-energy models with the potential to constrain the input parameters at their upper limit of applicability, their ultraviolet (UV) scale From this input, these can be used to describe chiral symmetry restoration [24,25] or model the deconfinement transition [26,27] with two or three quark flavors [28,29,30], and to describe vector mesons [31,32]. To demonstrate the feasibility of this formulation, we compute the ρ and a1 spectral functions from the resulting aFRG flow equations at finite temperature and density, across the critical end point (CEP) in the phase diagram of the model, in parallel with the previous study in [14] but with the fluctuations due to the massive vector and axial-vector mesons included. Further technical details concerning the FRG flow equations and the analytic continuation procedure are provided in Appendixes B and C
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