Rho Meson Broadening in Hot and Dense Hadronic Matter

The dispersion relation of $\rho$ meson in both timelike and spacelike regimes in hot and dense nuclear medium is analyzed and compared with $\sigma $ meson based on the quantum hadrodynamics model. The pole and screening masses of $\rho $ and $\sigma$ are discussed. The behavior of screening mass of $\rho$ is different from that of $\sigma$ due to different Dirac- and Fermi-sea contributions at finite temperature and density.

The properties of vector mesons in nuclear matter are discussed. Results for the momentum dependence of the $\rho$-meson self energy in matter due to $\rho N$ interactions are presented, and consequences for the production rate of $e^+e^-$ pairs in hot and dense matter are discussed. I also examine the constraints imposed by elementary processes on the widths of $\rho$ and $\omega$ mesons in nuclear matter, and conclude that in recent models the in-medium widths of these meso...

The $\rho$ meson self-energy in nuclear matter from baryonic loops is analysed in the real time formulation of field theory at finite temperature and density. The discontinuities across the branch cuts of the self-energy function are evaluated for an exhaustive set of resonances in the loops considering the fully relativistic thermal baryon propagator including anti-baryons. Numerical calculations show a significant broadening of the $\rho$ spectral function coming from the L...

We study the properties of rho mesons in nuclear matter by means of QCD sum rules at finite density. For increased sensitivity, we subtract out the vacuum contributions. With the spectral function as estimated in the literature, these subtracted sum rules are found to be not well satisfied. We suppose that Landau singularities from higher resonance states in the nearby region in this channel are the cause for this failure.

The mass shift $\Delta m_{\rho}$ and width broadening $\Delta\Gamma_{\rho}$ of $\rho$ mesons produced in heavy ion collisions is estimated using a general formula which relates the in-medium mass shift of a particle to the real part of the forward scattering amplitude ${\rm Re} f(E)$ of this particle on constituents of the medium and $\Delta\Gamma$ to the corresponding cross section. It is found that in high energy ($E/A \ga 100~$GeV) heavy ion collisions the $\rho$ width bro...

Effective spectral functions of the $\rho$ meson are reconstructed by considering the lifetimes inside different media using the hadronic transport SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). Due to inelastic scatterings, resonance lifetimes are dynamically shortened (collisional broadening), even though the employed approach assumes vacuum resonance properties. Analyzing the $\rho$ meson lifetimes allows to quantify an effective broadening of the decay ...

We study $\pi\pi$ scattering in the I=1, $J^P=1^-$ channel at finite temperature in the framework of the extended Nambu-Jona-Lasinio model that explicitly includes vector and axial-vector degrees of freedom in addition to the usual scalar and pseudoscalar sector. The S-matrix in the coupled channels $q\bar q$ and $\pi \pi$ is constructed via $\rho$-exchange in the $s$-channel. The self-energy of the $\rho$-meson contains both quark and pion loop contributions. The analytic st...

We calculate the modification of a rho meson in nuclear matter through its coupling to resonance-hole states. Starting from a recently proposed model, we include all four star resonances up to 1.9 GeV. In contrast to previous works, we include not only resonances that couple to the rho in a relative p-wave, but also those that couple to an s-wave state. In addition, we solve the equation for the rho spectral function self-consistently. We find that s-wave resonances affect th...

We investigate the modification of meson spectral densities in dense nuclear matter at zero temperature. These effects are studied in a fully relativistic mean field model which goes beyond the linear density approximation and also includes baryon resonances. In particular, the role of N*(1520) and N*(1720) on the rho meson spectral density is highlighted. Even though the nucleon-nucleon loop and the nucleon-resonance loop contribute with the opposite sign, an overall reducti...

The excess of low invariant mass dilepton yield in heavy ion collisions arising from reduction in the rho meson mass at finite temperatures is partially suppressed because of the effect on the width of the rho meson induced by Bose enhancement, essentially due to emission of pions in a medium of the pion gas in the central rapidity region. The sensitivity of the effect on the initial temperature of the hadronic phase is also examined.