Neutral Vector Mesons and the Hadronic Electromagnetic Current

Kroll, N.; Lee, T. D.; Zumino, Bruno

doi:10.1103/physrev.157.1376

Cited by 662 publications

(282 citation statements)

References 26 publications

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“…This includes the addition of kinetic terms for the EW fields, new chirally and gauge invariant interactions between the EW and meson fields of a form similar to the Kroll, Lee, and Zumino coupling [31], i.e., F EW L F L , as well as interactions of the form of the non-minimal terms. All couplings associated with the external fields are dictated by gauge symmetry and related to the parameters in Eq.…”

Section: The Massive Yang-mills Lagrangianmentioning

confidence: 99%

Massive Yang–Mills for vector and axial-vector spectral functions at finite temperature

Hohler

Rapp

2016

Annals of Physics

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The hadronic mechanism which leads to chiral symmetry restoration is explored in the context of the ρπa1 system using Massive Yang-Mills, a hadronic effective theory which governs their microscopic interactions. In this approach, vector and axial-vector mesons are implemented as gauge bosons of a local chiral gauge group. We have previously shown that this model can describe the experimentally measured vector and axial-vector spectral functions in vacuum. Here, we carry the analysis to finite temperatures by evaluating medium effects in a pion gas and calculating thermal spectral functions. We find that the spectral peaks in both channels broaden along with a noticeable downward mass shift in the a1 spectral peak and negligible movement of the ρ peak. The approach toward spectral function degeneracy is accompanied by a reduction of chiral order parameters, i.e., the pion decay constant and scalar condensate. Our findings suggest a mechanism where the chiral mass splitting induced in vacuum is burned off. We explore this mechanism and identify future investigations which can further test it.

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Section: The Massive Yang-mills Lagrangianmentioning

confidence: 99%

Massive Yang–Mills for vector and axial-vector spectral functions at finite temperature

Hohler

Rapp

2016

Annals of Physics

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“…A suitable chiral effective Lagrangian can be obtained by, e.g., introducing the vector fields as local gauge fields into the chiral pion Lagrangians and implementing the photon field via vector dominance [34,35],…”

Section: ρ Mesonmentioning

confidence: 99%

Dilepton radiation at the CERN super-proton synchrotron

2008

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A quantitative evaluation of dilepton sources in heavy-ion reactions is performed taking into account both thermal and non-thermal production mechanisms. The hadronic thermal emission rate is based on an electromagnetic current-correlation function with a low-mass region (LMR, M 1 GeV) dominated by vector mesons (ρ, ω, φ) and an intermediate-mass region (IMR, 1 GeV ≤ M ≤ 3 GeV) characterized by (the onset of) a multi-meson continuum. A convolution of the emission rates over a thermal fireball expansion results in good agreement with experiment in the low-mass spectra, confirming the predicted broadening of the ρ meson in hadronic matter in connection with the prevalence of baryon-induced medium effects. The absolute magnitude of the LMR excess is mostly controlled by the fireball lifetime, which in turn leads to a consistent explanation of the dilepton excess in the IMR in terms of thermal radiation. The analysis of experimental transversemomentum (qT ) spectra reveals discrepancies with thermal emission for qT 1 GeV in noncentral In-In collisions, which we address by extending our calculations by: (i) a refined treatment of ρ decays at thermal freezeout, (ii) primordially produced ρ's subject to energy-loss, (iii) Drell-Yan annihilation, and (iv) thermal radiation from t-channel meson exchange processes. We investigate the sensitivity of dilepton spectra to the critical temperature and hadro-chemical freezeout of the fireball. The ρ broadening in the LMR turns out to be robust, while in the IMR Quark-Gluon Plasma radiation is moderate unless the critical temperature is rather low.

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“…Experimentally, the cleanest information is obtained from electromagnetic probes which penetrate the medium almost undisturbed. In the vector dominance model (VDM) [1,2] electromagnetic processes are mediated by neutral vector mesons (ρ 0 , ω and φ). Therefore the medium modifications of vector mesons are of particular interest.…”

Section: Introductionmentioning

confidence: 99%