Light scalar K0*(700) meson in vacuum and a hot medium

Abstract

The K * 0 (700) meson appears as the lightest strange scalar meson in PDG. Although there were a lot of experimental and theoretical efforts to establish this particle and determine its properties and nature, it still needs confirmation in an experiment and its internal quark-gluon organization needs to be clarified. In this connection, we study some spectroscopic properties of this state in a hot medium as well as a vacuum by modeling it as a usual meson of a quark and an aniquark. In particular, we investigate its mass and coupling or decay constant in terms of the temperature of a hot medium by including the medium effects by the fermionic and gluonic parts of the energy momentum tensor as well as the temperature-dependent continuum threshold, quark, gluon and mixed condensates. We observe that the mass of K * 0 (700) remains unchanged up to T ≃ 0.6 Tc with Tc being the critical temperature, but it starts to diminish after this point and approaches zero near to the critical temperature referring to the melting of the meson. The coupling of K * 0 (700) is also sensitive to T at higher temperatures. It starts to grow rapidly after T ≃ 0.85 Tc. We turn off the medium effects and calculate the mass and coupling of the K * 0 (700) state at zero temperature. The obtained mass is in accord with the average Breit-Wigner mass value reported by PDG. I. MOTIVATIONThe light scalar mesons with a mass below 1 GeV are among particles that are not experimentally well established and their nature needs to be clarified. Their mass and width suffer from large uncertainties. Hence, their investigation constitutes one of the directions of research in high energy physics. There are a lot of models and approaches aiming to clarify their nature and internal quark-gluon organization. The standard quark model for the mesons handling them as bound states of quarks and antiquarks fails to correctly describe the mass hierarchy and the existing large uncertainties on the parameters of these particles. As a result, some of these particles like the light unflavored f 0 (500) state have already been treated as the unconventional exotic states of compact tetraquarks or two-meson molecules [1,2].The lightest scalar strange meson K * 0 (700) appears in PDG with the quantum numbers I(J P ) = 1/2(0 + ) and the qualifier "needs confirmation". The reported average T-matrix pole as well as Breit-Wigner mass and width for this state are [3]:T-matrix pole √ s = (630 − 730) − i(260 − 340) M eV, Breit-Wigner mass = 824 ± 30 M eV, Breit-Wigner width = 478 ± 50 M eV.(1)

Studying the a0(980) tetraquark candidate using K0/sK± interactions in the LHC ALICE collaboration

“…Since then, there have been a number of QCD studies of these mesons that fall in the categories of QCD-inspired models, for example Refs. [3][4][5][6], and lattice QCD calculations, for example Refs. [7][8][9].…”