Anomalous spin-1-meson decays from the gauged Wess-Zumino term

Gomm, Harald; Kaymakcalan, O.; Schechter, J.

doi:10.1103/physrevd.30.2345

Cited by 91 publications

(88 citation statements)

References 19 publications

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“…Early applications of MYM successfully describe the tree level masses and decays of the ρ and a 1 mesons [14,17,18]. These studies were extended to finite temperatures [19][20][21] revealing a reduction of the a 1 mass along with an increase in the ρ mass.…”

Section: Introductionmentioning

confidence: 99%

“…In the MYM approach [14,17], the chiral pion Lagrangian is locally gauged under the symmetry group SU (2) L × SU (2) R . In this paper, we will explore both the linear and non-linear realization of this symmetry.…”

Section: The Massive Yang-mills Lagrangianmentioning

confidence: 99%

“…This combines chiral effective theories, which have had considerable success in describing pion driven low-energy properties of QCD [13], with the general field theoretical concept of gauge symmetries. This has been realized in two formalisms, Massive Yang-Mills (MYM) [14] and Hidden Local Symmetry (HLS) [15,16], which have been shown to be on-shell equivalent.…”

Section: Introductionmentioning

confidence: 99%

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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: Introductionmentioning

confidence: 99%

Section: The Massive Yang-mills Lagrangianmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Hohler

Rapp

2016

Annals of Physics

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“…The local-gauge procedure was the method of choice to introduce axial-/vector mesons into chiral pion Lagrangians for many years, via Massive Yang-Mills [23] or Hidden Local Symmetry [24,25] approaches. However, it turned out to be rather challenging to quantitatively describe the vacuum axial-/vector spectral functions in these approaches, as the single gauge coupling constant does not seem to generate enough strength in the axialvector channel.…”

Section: Massive-yang Mills Chiral Lagrangianmentioning

confidence: 99%

Dileptons and Chiral Symmetry Restoration

Hohler

Rapp

2016

Nuclear and Particle Physics Proceedings

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We report on recent work relating the medium effects observed in dilepton spectra in heavy-ion collisions to potential signals of chiral symmetry restoration. The key connection remains the approach to spectral function degeneracy between the vector-isovector channel with its chiral partner, the axialvector-isovector channel. Several approaches are discussed to elaborate this connection, namely QCD and Weinberg sum rules with input for chiral order parameters from lattice QCD, and chiral hadronic theory to directly evaluate the medium effects of the axialvector channel and the pertinent pion decay constant as function of temperature. A pattern emerges where the chiral mass splitting between ρ and a 1 burns off and is accompanied by a strong broadening of the spectral distributions.

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“…[2] we have calculated photon-generating processes including the exchange of a 1 , ρ, and π mesons within the massive Yang-Mills (MYM) approach [3,4], as well as the πρω vertex as given by the Wess-Zumino Lagrangian [5], augmented by standard (dipole) FFs [2,6] that are unity on-shell. The four parameters of the MYM Lagrangian can be fit using measured values [7] of m ρ , m a 1 , ρ→ππ , and a 1 →ρπ , whereas the coupling constant g ωπρ is fixed by the decay ω → πγ .…”

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confidence: 99%

Reply to “Comment on ‘Hadronic production of thermal photons’”

2005

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We address a recent comment by Alam et al. [Phys. Rev. C 71, 059802 (2005)], on our work of thermal photon emission rates from hadronic matter. Specifically, we explain how t-channel ω exchange in the πρ → πγ reaction arises as a dominant contribution to the rates at high energy and why hadronic form factors cannot be neglected in this assessment. [2], namely that t-channel ω exchange is a dominant source of high-energy photons from a thermal hadronic gas. In their reasoning, they intentionally omit the insertion of form factors (FFs) at hadronic vertices to "understand the relative importance of ω and a 1 exchange processes" [1].Hadronic FFs are a conventional way to incorporate finitesize effects in describing hadronic reactions, especially at high momentum transfer, where hadronic substructure becomes important. They arise naturally and are ubiquitous in field theories with emergent degrees of freedom. In Ref.[2] we have calculated photon-generating processes including the exchange of a 1 , ρ, and π mesons within the massive Yang-Mills (MYM) approach [3,4], as well as the πρω vertex as given by the Wess-Zumino Lagrangian [5], augmented by standard (dipole) FFs [2,6] that are unity on-shell. The four parameters of the MYM Lagrangian can be fit using measured values [7] of m ρ , m a 1 , ρ→ππ , and a 1 →ρπ , whereas the coupling constant g ωπρ is fixed by the decay ω → πγ . The latter is an off-shell decay (proceeding via an intermediate ρ meson) with the FF entering the decay width as ω→πγ ∝ (g ωπρ F F ωπρ ) 2 . We obtained g ωπρ = 22.6 GeV −1 (with a typical FF cutoff of 1 GeV), as compared to g ωπρ = 11.93 GeV −1 with F F ωπρ ≡ 1. The presence of the FF clearly and simply increases the coupling constant. Our procedure is corroborated by inspecting the triple-pion ω decay channel. In the gauged Wess-Zumino Lagrangian [5] that reproduces the radiative decay of the ω, the width for ω → πππ is ω→πππ = 5.1 MeV (with FF = 1), whereas the experimental result is 7.49 ± 0.08 MeV. Once the FF is implemented at each vertex of the reaction, we find ω→πππ = 7.47 MeV. The presence of the FF obviously increases the value of the coupling constant g ωπρ , but of course the full effect has to involve both coupling and FF. The net effect is an increase of the width for ω → πππ and this enhancement carries over to the π + ρ → π + γ reaction with ω exchange.As discussed in Ref.[2], for the case of ω exchange an incoherent addition of the s-and t-channel contributions is justified. This is illustrated in the top panel of

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Anomalous spin-1-meson decays from the gauged Wess-Zumino term

Cited by 91 publications

References 19 publications

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

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

Dileptons and Chiral Symmetry Restoration

Reply to “Comment on ‘Hadronic production of thermal photons’”

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