REVIEW
Meson-Meson interaction in a non-perturbative chiral approach
High Energy Physics - Phenomenology · Submitted 2 Apr 1998 · 48 references
Pith's verdict: The full coupled-channel unitarized ChPT paper behind their PRL — the method holds up and earned its citations, but the fit is reported only as curves, and the σ and κ poles rest on a cutoff that is never varied.
T0 · AI review
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Referee report
The paper
The paper claims
A coupled-channel unitarized chiral Lagrangian with seven fitted fourth-order coefficients describes meson-meson scattering up to about 1.2 GeV and generates poles for the $f_0$, $a_0$, $rho$, $K^*$, $phi$, $sigma$ and $kappa$ resonances.
The reading
What carries the argument
The load-bearing formula is Eq. (16): $$T = T_2 cdot [T_2 - T_4^P - T_2 G T_2]^{-1} cdot T_2,$$ where $T_2$ is the $O(p^2)$ chiral amplitude, $T_4^P$ is the polynomial part of the $O(p^4)$ amplitude, and $G$ is the two-meson loop function whose imaginary part gives the phase space. This is a coupled-channel generalization of the inverse amplitude method: expanding $T^{-1}$ instead of $T$ moves the resonance poles into zeros of the inverse, and the matrix structure keeps unitarity when several channels couple. The toy-model section shows that for an exact Breit-Wigner resonance the same construction reproduces the propagator, which is the paper's explanation for why the method works well in resonant channels.
Extended reading notes
Core claim
The paper claims that a coupled-channel amplitude built from the $O(p^2)$ and $O(p^4)$ chiral Lagrangians, with seven fourth-order coefficients fitted to data and a fixed cutoff $q_{max}=1.02$ GeV, describes meson-meson scattering in seven isospin and angular-momentum channels up to about $1.2$ GeV. The amplitude is not a polynomial fit: it imposes coupled-channel unitarity through the loop function $G$, and its analytic continuation develops poles in the complex energy plane for the $f_0$, $a_0$, $rho$, $K^*$, $phi$, $sigma$ and $kappa$. The paper reports pole positions such as $sigma$ at $442-i227$ MeV, $f_0(980)$ at $994-i14$ MeV, $rho(770)$ at $759-i70$ MeV, $K^*(890)$ at $892-i21$ MeV and $a_0(980)$ at $1055-i21$ MeV, and it reproduces total and partial decay widths, including $f_0 to pi pi$ or $K bar K$ and $a_0 to pi eta$ or $K bar K$. The authors acknowledge that crossed-channel loops and tadpoles are not explicit and are absorbed into the fitted coefficients.
Load-bearing premise
The load-bearing premise is that the fourth-order chiral amplitude can be split as a polynomial plus a loop term, Eq. (15), and that all crossed-channel loops and tadpoles omitted by the calculation can be absorbed into the seven fitted coefficients without changing the amplitude's form.
Editorial extensions
If this is right
- In the $(0,0)$ channel the $f_0(980)$ pole appears only because the $K bar K$ channel is included; a single-channel treatment misses it. The same coupled-channel requirement brings out the $a_0(980)$ in the $(1,0)$ channel.
- The $rho$ and $K^*$ come out as nearly elastic Breit-Wigner resonances, so single-channel treatments of those channels are justified and the coupled-channel corrections are small there.
- The fitted coefficients $hat L_i$ are of the same order as the standard chiral perturbation theory $L_i$ at $mu simeq 1.2$ GeV, giving a quantitative bridge between the low-energy and resonance regions.
- The scheme predicts broad $sigma$ and $kappa$ poles and gives partial widths, for example $f_0$ about $65%$ $pi pi$ and $35%$ $K bar K$, and $a_0$ about $50%$ $pi eta$ and $50%$ $K bar K$.
- The same amplitudes can be inserted into photoproduction, meson-nucleon, nuclear-medium and strongly interacting symmetry-breaking problems.
Reading between the lines
- Because the $sigma$ and $kappa$ poles lie far from the real axis, their exact positions are the least robust output; a full crossed-channel calculation could move them appreciably while still fitting the same data, so their quoted masses and widths should be treated as scheme-dependent.
- The $phi$ pole appears about $30$ MeV below its physical mass with zero width because three-pion coupling is omitted; adding that small coupling is a sharp test of whether the fitted parameters survive when a new channel is opened.
- The breakdown above $1.2$ GeV is a natural place to look for the omitted $eta eta$ and multi-pion channels; if adding them leaves the seven coefficients nearly unchanged, the two-meson truncation is better justified than the paper's own caveat suggests.
Original abstract
A non-perturbative method which combines constraints from chiral symmetry breaking and coupled channel unitarity is used to describe the meson-meson interaction up to about 1.2 GeV. The approach uses the O(p^2) and O(p^4) chiral Lagrangians. The seven free parameters of the O(p^4) Lagrangian are fitted to the data. The results are in good agreement with a vast amount of experimental analyses. The amplitudes develop poles in the complex plane corresponding to the f0, a0, rho, K*, phi, sigma and kappa resonances; the latter two, very broad. The total and partial decay widths of the resonances are also well reproduced. Further extensions and applications of this chiral non-perturbative scheme are also discussed.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
A non-perturbative method which combines constraints from chiral symmetry breaking and coupled channel unitarity is used to describe the meson-meson interaction up to about 1.2 GeV. The approach uses the O(p^2) and O(p^4) chiral Lagrangians. The seven free parameters of the O(p^4) Lagrangian are fitted to the data. The results are in good agreement with a vast amount of experimental analyses. The amplitudes develop poles in the complex plane corresponding to the f0, a0, rho, K*, phi, sigma and kappa resonances; the latter two, very broad. The total and partial decay widths of the resonances are also well reproduced. Further extensions and applications of this chiral non-perturbative scheme are also discussed.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | A non-perturbative method which combines constraints from chiral symmetry breaking and coupled channel unitarity is used to describe the meson-meson interaction up to about 1.2 GeV. | method 0.80 | 0.90 | 0.22 | asserted 1.00 |
| s1 | The approach uses the O(p^2) and O(p^4) chiral Lagrangians. | method 1.00 | 0.64 | 0.03 | asserted 1.00 |
| s2 | The seven free parameters of the O(p^4) Lagrangian are fitted to the data. | method 0.99 | 0.88 | 0.05 | asserted 1.00 |
| s3 | The results are in good agreement with a vast amount of experimental analyses. | result 0.92 | 0.75 | 0.35 | asserted 1.00 |
| s4 | The amplitudes develop poles in the complex plane corresponding to the f0, a0, rho, K*, phi, sigma and kappa resonances; the latter two, very broad. | result 1.00 | 0.89 | 0.24 | asserted 1.00 |
| s5 | The total and partial decay widths of the resonances are also well reproduced. | result 1.00 | 0.87 | 0.13 | asserted 1.00 |
| s6 | Further extensions and applications of this chiral non-perturbative scheme are also discussed. | future work 1.00 | 0.53 | 0.04 | asserted 0.85 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
Figures
Figures reproduced from arXiv:hep-ph/9804209 by the authors.
References
How later papers used it
134 later papers cite it
3 later papers by other authors are listed below: 2 used its method or tool and 1 used its data or values.
Uses its method or tool 2 of 48 papers with this label
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Briefly introduced the inverse amplitude method of this paper and showed its fit to meson-meson partial waves with special weight on the (ηK, πK) system.
Finite volume effects in pion-kaon scattering and reconstruction of the kappa(800) resonance (2011) · 0.97 · paraphrased: the licence does not allow quoting
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Extracted resonance parameters using a unitary chiral perturbation theory model based on this paper.
Rho resonance parameters from lattice QCD (2016) · 1.00 · paraphrased: the licence does not allow quoting
Uses its data or values 1 of 5 papers with this label
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Used the two-pion decay width Γ(f0→ππ)=19.5 MeV derived in this paper within a chiral unitarity approach to estimate the effective coupling gKK̅ππ around 10 GeV.
f0(980) meson as a K bar K molecule in a phenomenological Lagrangian approach (2007) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
117 arXiv papers cite this in 216 sentences
Papers citing it · 122 sentences without a confident label
Builds on it 1 paper
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In the further extension of Ref. [ref] , the next-order $𝒪(p^4)$ Lagrangian of chPT is taken into account, where additional parameters entering by this procedure are also fitted to data.
Dynamical generation of hadronic resonances in effective models with derivative interactions · Coupled-channel unitarity approach by Oller, Oset, and Peláez · 0.86
Uses its method or tool 44 papers
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To parametrize the scattering amplitude we use unitarized chiral perturbation theory (U$χ$PT) [ref] , which is derived from standard $χ$PT [ref] by applying the Inverse Amplitude Method.
From QCD to Physical Resonances · METHOD AND RESULTS · 0.99
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The squares in the diagrams mean the full meson–meson scattering amplitudes involving the loop resummation through the BS equation [ref] .
Final state interactions in the decays J/psi->VPP · Formalism · 0.99
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The required kernels, i.e., the potentials which describe the interaction of the different pairs of the system are calculated using chiral Lagrangians [ref] .
Searching for exotic states in the $N \pi K $ system · Formalism and Results · 0.81
Uses its data or values 4 papers
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However, by using the two-pion decay width $Γ(f_0→ππ)$=19.5 MeV derived in [ref] within the framework of a chiral unitarity approach, we can estimate the effective coupling $g_KK̅π⃗π⃗$ around 10 GeV.
f0(980) meson as a K bar K molecule in a phenomenological Lagrangian approach · The strong decay · 1.00
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[ref] that is slightly better for this quantum number (dashed vs. solid line in figure [ref]).
Finite volume effects in pion-kaon scattering and reconstruction of the kappa(800) resonance · P-wave states: Extraction of the K*(892) and the rho(770) · 0.93
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The values of the $O(p^4)$ coupling constants are given in Table II of Ref. [ref] and the cutoff momentum $q_max=1.02$.
Form factors of the $\rho$ meson from effective field theory and the lattice · Parameterization of the $ππ$ amplitude in the vicinity of the pole · 0.99
Compares with it 4 papers
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Furthermore, small differences between two parameterizations can be parameterized by introducing the quantity ϵ_i(k^2)=2(G_i(k^2)-G_i'(k^2))/|G_i(k^2)|+|G_i'(k^2)| , i=1,2,3 , where $G_i(k^2)$ and $G_i'(k^2)$ are calculated with the use of the parameterizations from Ref. [ref] and Ref. [ref] , respectively.
Form factors of the $\rho$ meson from effective field theory and the lattice · Numerical implementation: contact contributions to the form factors in NREFT · 0.87
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[ref] (dashed lines in fig.
Finite volume effects in pion-kaon scattering and reconstruction of the kappa(800) resonance · The pion-kaon amplitude in the infinite volume limit with next-to-leading order terms · 0.99
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The results are shown in Figure [ref] and are in agreement with previous works on the subject [ref] : $(i)$ We observe a rapidly falling inelasticity when the $KK̅$ threshold is reached.
Dynamical generation of hadronic resonances in effective models with derivative interactions · Phase shifts and inelasticity · 0.99
Cites it as support 2 papers
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This has been shown to be sufficient to reproduce the available scattering data on the scalar channel and generates the observed resonances [ref] .
Investigation of a0-f0 mixing · Form factors and unitarization · 0.97
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This procedure has been shown to accurately describe low-lying resonances in multiple channels with a relatively small set of parameters (see, for example, Refs. [ref] ).
From QCD to Physical Resonances · METHOD AND RESULTS · 0.99
Cites it as background 22 papers
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The application of the BSE methodology to the light (up and down) quark sector have been plentiful both in the meson [ref] as well as baryon sector [ref] , which also includes extensions to coupled channels.
Towards a theory of hadron resonances · Light quark sector: Meson-meson scattering · 0.90
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The $ππ$-$KK̅$-$πη$ coupled-channel system around $1$ was studied in this framework in Ref. [ref] with a particular interest in the $f_0$ and $a_0$ resonances followed by the studies with similar approaches [ref] [The scalar mesons around 1 GeV have been studied for a long time, and many studies were devoted for it from various viewpoints, e.g., as done in Refs. [ref] (see also Ref. [ref] for a review article).] and the applications to many reactions.
Role of the triangle mechanism in the $\Lambda_b\rightarrow \Lambda_c\pi^-f_0(980)$ reaction · $KK̅→π^+π^-$ scattering amplitude · 0.80
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In the literature, three schemes were proposed to unitarize coupled-channel amplitudes, i.e., the inverse amplitude method [ref] , the N/D method [ref] , and the Bethe-Salpeter method [ref] .
Radiative decays of the $\Lambda(1520)$ as a dynamically generated resonance · Introduction · 0.89
Discussion
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