In-medium effects in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ϕ</mml:mi></mml:math> meson production in heavy-ion collisions from subthreshold to relativistic energies
Taesoo Song, Joerg Aichelin, Elena Bratkovskaya
Abstract
We investigate the hidden strange $\ensuremath{\phi}$ meson production in heavy-ion collisions from subthreshold (${E}_{\text{kin}}\ensuremath{\approx}1A$ GeV) to relativistic (${E}_{\text{kin}}\ensuremath{\approx}21A$ TeV) energies as well as its coupling to the open strange mesons (kaons, antikaons) and their productions. Our study is based on the off-shell microscopic parton-hadron-string dynamics (PHSD) transport approach which is applicable for the dynamical description of strongly interacting hadronic and partonic degrees-of-freedom created in heavy-ion collisions. Implementing novel meson-baryon and meson-hyperon production channels for $\ensuremath{\phi}$ mesons, calculated within a $T$-matrix coupled-channel approach based on the extended SU(6) chiral effective Lagrangian model, along with the collisional broadening of the $\ensuremath{\phi}$-meson in-medium spectral function, we find a substantial enhancement of $\ensuremath{\phi}$ meson production in heavy-ion collisions, especially at sub- and near-thresholds. This allows us to describe the experimentally observed strong enhancement of the $\ensuremath{\phi}/{K}^{\ensuremath{-}}$ ratio at low energies without including hypothetical decays of heavy baryonic resonances to $\ensuremath{\phi}$ as in alternative approaches. Moreover, we show that in spite of a stronger contribution from enhanced $\ensuremath{\phi}$ to ${K}^{\ensuremath{-}}$ production, the majority of the experimental data for different $A+A$ systems at low energies favor the scenario with in-medium modifications of the kaon and antikaon properties in the hot and dense environment. Moreover, we study the influence of the final-state interactions of $K,\phantom{\rule{0.16em}{0ex}}\overline{K}$ mesons on the reconstruction of $\ensuremath{\phi}\text{'}\mathrm{s}$ by the invariant-mass method.