Chiral Dynamics of the Two \Lambda(1405) States

A. Ramos; D. Jido; E. Oset; J.A. Oller; U.-G. Mei{\ss}ner

REVIEW

Chiral Dynamics of the Two \Lambda(1405) States

D. Jido, J.A. Oller, E. Oset, A. Ramos, U.-G. Mei{ss}ner

Nuclear Theory · Submitted 25 Mar 2003 · 25 references

Pith's verdict: The SU(3) classification of the two Λ(1405) poles is the real contribution here, and it holds up; the quantitative pole positions and the reaction-dependent line shapes are model-bound and the paper knows it.

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arXiv IDnucl-th/0303062 (version 1)

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CitationA. Ramos, D. Jido, E. Oset, J.A. Oller, U.-G. Mei{\ss}ner. "Chiral Dynamics of the Two \Lambda(1405) States." arXiv:nucl-th/0303062 (2003). https://pith.science/paper/ZU7KK5ZJ

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Editor's note

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You should read this for the group theory, not for the numbers. The two-pole structure near the Λ(1405) is prior work — Refs. [3, 7, 8] — and the paper says so plainly in the introduction. What is new is the SU(3) bookkeeping: Eq. (13), V = diag(6, 3, 3, 0, 0, −2) in the basis 1, 8s, 8a, 10, 10bar, 27, which shows the two octets share the same Born amplitude and therefore stay degenerate after unitarization. That step is clean algebra from the Weinberg-Tomozawa coefficients and does not depend on any fit. The decomposition of each physical pole into singlet and octet amplitudes (Table 5, Eqs. 22–25) is the natural follow-up and is done carefully. The suggestion that K⁻p → Λ(1405)γ weights the K̄N-coupled pole and should show a narrower, higher peak is a genuine falsifiable prediction, and it is the kind of thing this literature needs more of. The paper is also honest about its own inputs — Section 2 and Section 6 both flag the omitted higher-order kernel corrections, even though the classifier found no stated limitations. Credit where due: two independently developed models are run side by side, and the qualitative agreement is real cross-model support, not a rhetorical gesture. Now the soft spots, in proportion. The pole positions and widths rest on the SU(3)-breaking scheme: physical baryon masses inserted in Eq. (2) where M0 belongs at leading order, and the channel-dependent subtraction constants of Eq. (7) tuned to mimic a 630 MeV cutoff rather than derived. The spread between the two models is not small — the lower I=0 pole is 1390+66i versus 1379+27i, a factor ~2.5 in width — and that width is exactly what controls the line shapes in Figs. 2–5. So 'properties change from one reaction to another' is qualitatively supported but not quantitatively pinned. Second, the leading-order degeneracy of 8s and 8a is an accident of the WT kernel, not a symmetry requirement; the paper says this in Section 3, but the abstract's phrasing slightly overstates, since O(p²) SU(3)-symmetric terms would also split the octets and that is not quantified. On the reader's circularity worry: extracting residues from the amplitude via Eq. (15) is standard pole extraction, not circularity. Who should read it: anyone working on baryon spectroscopy or chiral unitary methods, and anyone planning photoproduction or K̄N experiments in this region. Worth a serious referee.

Referee report

Significance

The group-theoretic result of Eq. (13) is a clean, parameter-free consequence of the lowest-order chiral Lagrangian and is the part of the paper most likely to outlast the specific fits: it explains why two octets appear degenerate and why no bound states arise in the 10, 10bar and 27 channels. The paper also does the right thing by cross-checking the pole structure in two independently constructed models rather than one, and by publishing pole positions and complex couplings in Tables 1–4 in a form that later work can reuse. The prediction that the K̄N-initiated reaction K⁻p → Λ(1405)γ should produce a narrower, higher-lying peak than hadronic production is falsifiable and is the kind of statement that gives the two-pole picture experimental teeth. The qualitative conclusion — that the observed Λ(1405) shape is an effective superposition whose apparent parameters depend on the production mechanism — is well supported by the analysis of Section 5.

Major objections (3)

[Abstract, sentence s1; Section 3, paragraph after Eq. (13)] The abstract states without qualification that 'the SU(3) breaking produces the splitting of the two octets', but Section 3 itself concedes that 'there is no reason why they should be degenerate in principle' and that the degeneracy is a dynamical consequence of the leading-order kernel rather than a symmetry requirement. Since the two octets sit in the same irreducible representation content only by accident of the Weinberg–Tomozawa coefficients, any SU(3)-symmetric O(p²) contribution to V would split 8s from 8a even at x = 0. The two models compared here differ precisely in their subleading content (Ref. [3] keeps a common baryon mass M0 and includes direct and crossed Born terms, Refs. [5, 10] use physical masses and omit them), so the comparison already contains information about the size of such terms. I would ask the authors to reword the abstract so that the splitting is attributed to SU(3) breaking plus the leading-order accident, and to state explicitly in Section 3 that an O(p²) SU(3)-symmetric kernel could move the two octets apart at x = 0. This is a framing correction rather than a physics correction, but it is the paper's headline sentence and should not overstate what Eq. (13) proves.
[Section 3, pole-search prescription; Tables 1–4] The pole positions quoted throughout are obtained by a prescription — changing the sign of the on-shell momentum q_l in G_l(z) for channels open at Re(z) — that is stated in one sentence and never tabulated. The authors themselves note that in the model of Ref. [3] an additional I = 1 pole at 1401 MeV appears only if the sign in the K̄N channel is also flipped, and they defend that choice by the proximity of the K̄N threshold to the resonance. Because pole positions are sheet-dependent by construction, the reader cannot tell from Tables 1–4 which Riemann sheet each entry belongs to, nor whether the two I = 0 poles that carry the central claim are on sheets assigned by the same rule in both models. I would ask for an explicit column or footnote giving the sheet for every pole in Tables 1–4, and for a short demonstration that the two I = 0 poles are stable under the alternative sheet assignments that were considered for I = 1. Without that, the I = 1 discussion reads as a prescription chosen after the fact, and the reader has no way to judge how much of the I = 0 result is prescription-independent.
[Section 5, Figs. 4–5, and the K⁻p → Λ(1405)γ prediction] The reaction-dependent line shapes of Section 5 are the paper's main experimental message, and they are controlled by the width of the lower I = 0 pole, which differs by roughly a factor of 2.5 between the two models (1390 + 66i in Table 1 versus 1379 + 27i in Table 3). The authors acknowledge this spread in the text, but Figs. 4 and 5 are drawn from the model of Ref. [10] alone, and the concluding prediction that K⁻p → Λ(1405)γ yields a narrower peak at higher energy is stated without an uncertainty band. I would ask that the corresponding curves be shown for both models, or at minimum that the predicted peak position and width in Fig. 5 be quoted with the spread implied by Tables 1 and 3 attached. As it stands the qualitative statement 'properties change from one reaction to another' is well supported, but the quantitative version a reader would want to test against data is not pinned down, and the paper should say so where the prediction is made rather than only in the discussion of the two models.

Minor objections (6)

[Section 2, large-N_c paragraph] The argument that G_l counts as O(N_c^0) rests on the subtraction constants being generated by the cutoff relation of Eq. (9), and the authors correctly note that otherwise V G would be O(N_c^0) and the poles would survive the large-N_c limit. Since this paragraph is used to argue against the large-N_c treatment of Ref. [12], it would read more cleanly if the conditional nature of the conclusion were stated in the sentence that draws it, not only in the sentence that follows.
[Table 1 and Table 3] Both tables list three I = 0 poles without flagging that the third, near 1680 MeV, is the Λ(1670) and plays no role in the Λ(1405) claim. A parenthetical label in the caption would prevent the reader from supposing that three poles are being proposed near 1405 MeV.
[Eqs. (22)–(25) and the accompanying normalization discussion] The closure check on the basis transformation is reported as holding within 20% except for the SU(3) singlet column of Ref. [3], which is overestimated by 40%. Since Eqs. (17)–(20) assume closure, the size of this violation should be interpreted for the reader: does the 40% excess indicate a sizable continuum or 27 admixture in that pole, or merely the sensitivity of the decomposition to the SU(3)-limit couplings of Eq. (21)?
[Fig. 1] The figure carries a stray 'x = 0.6' label alongside the x = 0.5 and x = 1.0 markers, and the caption does not explain why that one trajectory is annotated at a different step. The axis labels also place Im z_R on the vertical axis without stating the units on both axes; both should be made explicit.
[Section 2, Eq. (6)] The four logarithmic terms in the q_l/√s bracket are written without the customary ±iπ offsets that specify the sheet, which is exactly the information a reader needs to reproduce the pole search of Section 3. A sentence stating the sheet convention used in evaluating Eq. (6) would remove the ambiguity.
[Whole manuscript] The text contains a number of typographical faults that should be corrected in proof, among them 'Universi ty' and 'andKernphysik' in the author block, 'Proceedigns' in Ref. [21], and several broken words in the running text. Reference [21] is listed as a conference proceedings 'in print'; if it has since appeared, the final citation should be supplied.

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The paper

The paper claims

The paper argues that the bump called the $Λ(1405)$ is not one resonance but two poles of the meson–baryon scattering matrix, a broad low one and a narrow high one, whose apparent shape depends on which channel starts the reaction.

The reading

The paper asks what the $Λ(1405)$ actually is. Working in a chiral unitary coupled-channel treatment of meson–baryon scattering with strangeness $S=-1$, the authors show that the SU(3) structure of the problem, $8⊗8 = 1 ⊕ 8_s ⊕ 8_a ⊕ 10 ⊕ 10̄ ⊕ 27$, allows a singlet and two octets of dynamically generated $J^π = 1/2^-$ states, and that the two octets come out exactly degenerate because the lowest-order potential is identical in both. Breaking SU(3) with physical masses splits the octets and leaves the singlet nearby, so the physical scattering matrix carries two poles in the $Λ(1405)$ region: a broad low one that couples mainly to $πΣ$ and a narrow high one that couples mainly to $K̄N$. If this is right, every experiment that reports a single $Λ(1405)$ is really reporting an interference-weighted mixture of two states, and the apparent mass and width should move with the production channel rather than being fixed properties of one particle.

What carries the argument

The load-bearing object is the unitarized amplitude $T = [1 - VG]^{-1} V$, where $V$ is the Weinberg–Tomozawa meson–baryon kernel and $G$ is the diagonal loop function regularized by subtraction constants. The decisive step is evaluating $V$ in the SU(3) basis, which gives $V_{αβ} = $ diag$(6, 3, 3, 0, 0, -2)$ and thereby explains both why the two octets are degenerate before symmetry breaking and why no bound states form in the $10$, $10̄$ and $27$ channels. Pole positions and complex couplings $g_i$ are then extracted by matching $T_{ij} = g_i g_j / (z - z_R)$ near each pole, and a basis rotation with the SU(3) Clebsch–Gordan coefficients converts physical-channel couplings into singlet and octet fractions, which is how the authors argue that the lowest pole is mostly singlet, the highest mostly antisymmetric octet, and the middle one an even mixture.

Extended reading notes

Core claim

The central claim is that two poles, not one, sit near the nominal $Λ(1405)$, and that they are the surviving physical descendants of a singlet and a degenerate pair of octets present in the exact-SU(3) limit. The authors first show that in the symmetry limit the transition potential in the irreducible-representation basis is diagonal with entries $(6, 3, 3, 0, 0, -2)$ for $1, 8_s, 8_a, 10, 10̄, 27$, so the two octets share the same Born amplitude and remain degenerate after unitarization, while the $10$, $10̄$ and $27$ entries are repulsive and generate nothing. They then turn on SU(3) breaking through a parameter $x$ that interpolates physical masses and subtraction constants, and follow the pole trajectories: one $I=0$ octet pole climbs toward the $Λ(1670)$ region, the other drops to a narrow state just below the $K̄N$ threshold, and the singlet settles at low energy with a large width. In the physical limit the two nearby $I=0$ poles are $1390 + 66i$ MeV and $1426 + 16i$ MeV in one model and $1379 + 27i$ MeV and $1434 + 11i$ MeV in the other, with the lower pole coupling more strongly to $πΣ$ and the upper more strongly to $K̄N$. The authors then show that coherent sums of the two poles reproduce a single Breit–Wigner-like bump, so that the two-state structure is hidden in plain sight rather than contradicted by existing data.

Load-bearing premise

The specific pole positions and the identification of which pole is singlet-like and which is octet-like depend on the chosen way of implementing symmetry breaking, namely physical masses in the potential plus channel-dependent subtraction constants tuned to a common cutoff, or alternatively a single constant with one-baryon-exchange terms; the paper itself notes that higher-order chiral corrections to the kernel are omitted and that the two models bracket rather than fix the uncertainty.

Editorial extensions

If this is right

The mass and width attributed to the $Λ(1405)$ are channel-dependent effective quantities, so comparing peak positions across different production experiments is not comparing a single resonance parameter.
A reaction that forces the initial state to be $K̄N$, such as $K^-p → Λ(1405)γ$ where the photon carries away the excess energy, should weight the narrow high pole and produce a peak that is narrower and sits at higher energy than hadronic measurements.
The two models compared in the paper, which differ in how SU(3) breaking enters the kernel and the loop functions, agree qualitatively on the two-pole structure, which the authors read as a measure of robustness against omitted higher-order chiral terms.
Because the product $VG$ counts as $O(1/N_c)$, these dynamically generated states disappear in the large-$N_c$ limit, so they are not ordinary quark-model states and are not suited to a large-$N_c$ counting treatment.
The $I=1$ amplitude in the same region is not negligible and interferes with the dominant $I=0$ part with opposite signs in $π^+Σ^-$ and $π^-Σ^+$, which produces charge-dependent cross sections.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

If the two-pole picture holds, a global amplitude analysis that fits all available $K̄N$ and $πΣ$ production data with a single Breit–Wigner should show systematic residuals, and refitting with two coupled poles should absorb them without adding new dynamics.
The same SU(3) bookkeeping that produces one singlet plus two degenerate octets in $S=-1$ predicts analogous double-octet structure in $S=-2$ and $S=0$; finding a second pole near the $Ξ(1620)$ or the $N^*(1535)$ would test the mechanism far more stringently than the $Λ(1405)$ alone.
Lattice calculations at unphysical quark masses could trace the degeneracy directly: as the pion mass is raised toward the SU(3) limit, the two $I=0$ poles should approach each other and merge, which is a sharper prediction than any single pole position.
If the singlet and octet mix as strongly as the extracted coefficients suggest, the mixing angles are themselves observables, and a future determination of the singlet fraction of the low pole would discriminate among the regularization schemes that currently bracket the answer.

Original abstract

Using a chiral unitary approach for the meson--baryon interactions, we show that two octets of J^{\pi}=1/2^- baryon states, which are degenerate in the limit of exact SU(3) symmetry, and a singlet are generated dynamically. The SU(3) breaking produces the splitting of the two octets, resulting in the case of strangeness S=-1 in two poles of the scattering matrix close to the nominal \Lambda(1405) resonance. These poles are combinations of the singlet state and the octets. We show how actual experiments see just one effective resonance shape, but with properties which change from one reaction to another.

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.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 3,666 input tokens.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.28 · human participants 0.02 · controlled comparison 0.05 · randomized assignment 0.01 · states quantitative result 0.08 · compares with prior results 0.11 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

Using a chiral unitary approach for the meson--baryon interactions, we show that two octets of J^{\pi}=1/2^- baryon states, which are degenerate in the limit of exact SU(3) symmetry, and a singlet are generated dynamically. The SU(3) breaking produces the splitting of the two octets, resulting in the case of strangeness S=-1 in two poles of the scattering matrix close to the nominal \Lambda(1405) resonance. These poles are combinations of the singlet state and the octets. We show how actual experiments see just one effective resonance shape, but with properties which change from one reaction to another.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	Using a chiral unitary approach for the meson--baryon interactions, we show that two octets of J^{\pi}=1/2^- baryon states, which are degenerate in the limit of exact SU(3) symmetry, and a singlet are generated dynamically.	contribution 0.53	0.93	0.40	asserted 1.00
s1	The SU(3) breaking produces the splitting of the two octets, resulting in the case of strangeness S=-1 in two poles of the scattering matrix close to the nominal \Lambda(1405) resonance.	result 0.98	0.79	0.32	asserted 1.00
s2	These poles are combinations of the singlet state and the octets.	result 0.81	0.77	0.17	asserted 1.00
s3	We show how actual experiments see just one effective resonance shape, but with properties which change from one reaction to another.	interpretation 0.62	0.79	0.30	asserted 1.00

What kind of paper the classifier reports this is: theoretical result 0.98 · evidence from simulation or computation 0.62.

What was examined, and what was not

sources read

arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures

**Figure 1.** References [1] M. Jones, R. H. Dalitz and R. R. Horgan, Nucl. Phys. B 129 (1977) 45. [2] N. Kaiser, T. Waas and W. Weise, Nucl. Phys. A 612 (1997) 297. [3] J. A. Oller and U.-G. Meißner, Phys. Lett. B 500 (2001) 263. [4] U.-G. Meißner, J. A. Oller, Phys. Rev. D 64 (2001) 014006. [5] E. Oset and A. Ramos, Nucl. Phys. A 635 (1998) 99. [6] P. J. Fink, G. He, R. H. Landau and J. W. Schnick, Phys. Rev. C 41 (1990) 2720. [7] D. Jido, A. Hosaka, J. C. Nacher, E. Oset and A. Ramos, Phys. Rev. C 66 (2002) 025203. [8] C. Garcia-Recio, J. Nieves, E. Ruiz Arriola and M. J. Vicente Vacas, arXiv

**Figure 2.** z1: the modulus square of the first term in Eq. (26) multiplied by pπ. z2: Same for the second term in Eq. (26). z1 + z2: Same for the coherent sum of the two terms. 1340 1360 1380 1400 1420 1440 1460 Ec.m. (MeV) 0 0,5 1 1,5 2 z1 z2 z1+z2

**Figure 3.** Same as Fig. 2 but for the terms in Eq. (27).

**Figure 4.** The πΣ mass distributions with I = 0 constructed from the KN¯ → πΣ and πΣ → πΣ amplitudes. The solid and dashed lines denote |TKN¯ →πΣ| 2 qπ and |TπΣ→πΣ| 2 qπ, respectively. Units are arbitrary. πΣ → πΣ (dotted line) and KN¯ → πΣ (solid line) amplitudes. As we expected, in the KN¯ → πΣ case, the resonance peaks at a higher energy and shows a narrower width. In

**Figure 5.** Modulus squared of the loop function Gl times the amplitudes, simulating a reaction with the resonance initiated by the πΣ (dashed line) or the KN¯ (solid lines) channels. 6 Conclusions In this paper we have investigated the poles appearing in the meson–baryon scattering matrix for strangeness S = −1 within a coupled–channel chiral unitary approach, using two different methods for breaking the SU(3) symmetry which have been used in the literature. In both approaches some resonances are generated dynamically from the interaction of the octet of pseudoscalar mesons with the octet of th

Figures reproduced from arXiv:nucl-th/0303062 by the authors.

References

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The isospin-violating J/ψ→ΛΛ̄π⁰ decay is shown to selectively produce the dynamically-generated Σ(1430) resonance while suppressing the conventional Σ(1385) state, matching limited BESIII data.
Machine learning unveils the quark mass dependence of the pseudoscalar meson decay constants in three-flavour N$^2$LO ChPT
hep-ph 2026-06 unverdicted novelty 5.0 of 10

LASSO regression on LQCD data determines quark-mass dependence of f_π, f_K, f_η in N²LO three-flavor ChPT and supplies LECs for SU(3)-limit baryon mass predictions.
Vector charmonium(-like) states in the energy range of 4.1-4.6 GeV
hep-ph 2026-06 unverdicted novelty 5.0 of 10

A coupled-channel framework is developed and fitted to BESIII data on vector charmonium-like states in the 4.1-4.6 GeV range, concluding that coupled-channel effects with dynamically generated poles explain the line shapes.
Finding Low Star Discrepancy 3D Kronecker Point Sets Using Algorithm Configuration Techniques
cs.NE 2026-04 unverdicted novelty 5.0 of 10

Optimizing the two Kronecker parameters with irace yields new state-of-the-art L∞ star discrepancy for 3D point sets of size at least 500 and for ranges of sizes.
Experimental Advances on Light Baryon Spectroscopy at BESIII Experiment
hep-ex 2026-03 unverdicted novelty 5.0 of 10

BESIII reports discoveries of new excited nucleon, Lambda, Sigma, Xi, and Omega hyperon states from high-statistics electron-positron collision data.
Probing the isospin structure and low-lying resonances in $\Lambda_c^+ \to n\bar{K}^0 \pi^+$ decays
hep-ph 2026-02 unverdicted novelty 5.0 of 10

The chiral unitary calculation predicts a narrow peak from N(1535) in the pi+ n invariant mass spectrum and a dip from Lambda(1670) in the K0bar n spectrum, supporting the molecular interpretation of these resonances.
The dynamically generated $h_1$ state by the $K^*\bar{K}^*$ interaction and its $K_1(1270)\bar{K}$ and $b_1(1235)\pi$ decays
hep-ph 2026-01 conditional novelty 5.0 of 10

The dynamically generated h1(1790) K*Kbar* molecule is predicted to decay into K1(1270)Kbar and b1(1235)pi with partial widths of about 0.5 to several MeV, plus stable width ratios R1≈0.3 and R2≈0.53.
Final state interaction in the $\Lambda_b\to D^+D^- \Lambda,~D^0D_s^- p,~D_s^+D_s^-\Lambda$ reactions
hep-ph 2025-07 conditional novelty 5.0 of 10

Threshold enhancements in the Ds-p, Ds-Lambda, and related mass distributions of Lambda_b decays are predicted from final state interactions with molecular exotic states.
Exotic Hadrons from Heavy Ion Collisions
nucl-th 2017-02 conditional novelty 5.0 of 10

Coalescence and statistical models of heavy ion collisions predict that compact multiquark hadrons are produced about an order of magnitude less abundantly than hadronic molecules or ordinary excited states of the same mass.
Constraints on the chiral unitary $\bar KN$ amplitude from $\pi\Sigma K^+$ photoproduction data
hep-ph 2014-11 conditional novelty 5.0 of 10

Photoproduction data from CLAS reduce eight equally good chiral-unitary descriptions of antikaon-nucleon scattering to three, narrowing the position of the broad Lambda(1405) pole.
Wave functions of composite hadron states and relationship to couplings of scattering amplitudes for general partial waves
hep-ph 2012-02 conditional novelty 5.0 of 10

A generalized Weinberg compositeness sum rule, valid for any partial wave, coupled channels, and resonances, indicates the rho meson is mostly not a pion-pion composite.
New insights into antikaon-nucleon scattering and the structure of the Lambda(1405)
nucl-th 2012-02 conditional novelty 5.0 of 10

A 17-parameter chiral Bethe-Salpeter fit to K-minus proton scattering and SIDDHARTA data yields scattering lengths a0 = -1.81 + 0.92i fm and a1 = 0.48 + 0.87i fm and locates two Lambda(1405) poles.
$\Lambda(1670)$ production in the $\psi(3686) \to \Lambda \bar \Lambda \eta$ reaction
hep-ph 2026-06 unverdicted novelty 4.0 of 10

Theoretical calculation of ψ(3686) → Λ Λ̄ η decay shows Λ(1670) peaks in ηΛ and ηΛ̄ distributions using two SU(3) flavor structures and final-state interactions, with one free parameter fitting data and supporting a m...
Towards a theory of hadron resonances
hep-ph 2022-06 accept novelty 3.0 of 10

The review consolidates lattice-QCD and effective-field-theory methods for hadron resonances and argues that Breit-Wigner parameterizations are incompatible with chiral symmetry in strongly coupled channels.
Threshold cusps and triangle singularities in hadronic reactions
hep-ph 2019-12 conditional novelty 3.0 of 10

Kinematic singularities of the S-matrix, not only resonances, can produce peaks in hadronic mass spectra, and their sensitivity to kinematics both exposes misidentifications and enables precision measurements.
Review of the ${\mathbf \Lambda}$(1405): A curious case of a strange-ness resonance
nucl-th 2020-09 conditional novelty 2.0 of 10

The Lambda(1405) is best described by two poles, a narrow one near 1420 MeV and a broad one near 1380 MeV, and this two-pole picture survives every modern model class once kaonic-hydrogen and CLAS photoproduction data...
Two-pole structures in QCD: Facts, not fantasy!
hep-ph 2020-05 accept novelty 2.0 of 10

The Lambda(1405) and the D*0(2300) are each two resonances rather than one, according to unitarized chiral perturbation theory checked against lattice QCD and LHCb data.
Strangeness in Nuclei and Neutron Stars
nucl-ex 2020-02 accept novelty 2.0 of 10

A comprehensive review of strangeness in nuclear matter: the two-pole Lambda(1405), kaon and antikaon potentials in dense matter, phi broadening, hyperon forces, and their role in neutron star interiors.
Heavy Hadrons in Nuclear Matter
hep-ph 2016-06 accept novelty 2.0 of 10

The review consolidates three decades of theory on charm and bottom hadrons in nuclear matter, organized by chiral symmetry and heavy quark spin symmetry, and reports where competing models agree and where they do not.

How later papers used it

136 later papers cite it

Evidence: substantial. 100 of the citing papers share no author with it, and 23 of those carry a confident label from Pith's citation classifier.

Pith read 21 of the 264 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

2 later papers by other authors are listed below: 1 used its data or values and 1 cited it as support.

Uses its data or values 1 of 4 papers with this label

Adopted the same subtraction constants as this paper for the loop function.

Identifying the two-pole structure of the $\Lambda(1405)$ using an SU(3) flavor filter (2024) · 0.92 · paraphrased: the licence does not allow quoting

Cites it as support 1 of 5 papers with this label

Said that its approximation is justified by the chiral perturbation theory with the Weinberg-Tomozawa interaction of this paper, where the 8_s and 8_a do not mix.

Study on Lambda(1405) in the flavor SU(3) limit in the HAL QCD method (2023) · 1.00 · paraphrased: the licence does not allow quoting

How the literature uses it

116 arXiv papers cite this in 229 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers whose main result relates to this one's

Found among the papers closest to this one by title and main claim. Pith's classifier compared each pair's main results and a second model family confirmed the relation; checked against two further families, shown conflicts agreed 118 times in 120 and shown same results 218 times in 239. The quoted sentence is the other paper's main claim.

States the same result 3 papers

The Lambda(1405) emerges as containing the effect of two poles of the scattering amplitude and various reactions that might preferentially select one or the other pole are discussed.

Dynamical baryon resonances from chiral unitarity · 0.86
We reach the conclusion that the Lambda(1405) resonance seen in experiments is not just one single resonance, but a superposition of these two states.

Chiral dynamics of the two Lambda(1405) states · 0.82
In this talk we report on how, using a chiral unitary approach for the meson--baryon interactions, two octets of $J^{\pi}=1/2^-$ baryon states and a singlet are generated dynamically, resulting in the case of strangeness $S=-1$ in two poles of the scattering matrix close to the nominal $\Lambda(1405)$ resonance.

Dynamical Generation of Hyperon Resonances · 0.80

States a conflicting result 1 paper

The squared amplitude is suppressed strongly and only one $\Lambda(1405)$ state is generated dynamically in the strangeness $S=-1$ and isospin $I=0$ sector.

The Lambda(1405) state in a chiral unitary approach with off-shell corrections to dimensional regularized loop functions · 0.87

Papers citing it · 165 sentences without a confident label

Uses its method or tool 12 papers

For the meson-baryon amplitudes we apply the so-called chiral unitary approach [ref] .

Production of hyperon resonances induced by kaon on a deuteron target · $K^- d$ Scattering amplitudes · 0.99
For the description of the $Λ(1405)$ states, we use the chiral unitary approach [ref] .

Wave functions for dynamically generated resonances; the two $\Lambda(1405)$ and $\Lambda(1670)$ · Introduction · 0.93
We shall use the extended local hidden gauge symmetry approach [ref] , which has been widely applied in the study of the meson-meson and meson-baryon interactions [ref] .

Hadronic molecular states with the quark contents $bc\bar{s}\bar{q}$, $b\bar{c}s\bar{q}$, and $b\bar{c}\bar{s}q$ · Introduction · 0.98

Uses its data or values 3 papers

The most interesting thing in this model is that two poles exist around the $Λ(1405)$ energy region at $z_1=(1390,-i66)$ MeV and $z_2=(1426,-i16)$ MeV [ref] .

Wave functions for dynamically generated resonances; the two $\Lambda(1405)$ and $\Lambda(1670)$ · Introduction · 0.93
For the LO WT interaction, we adopt the same subtraction constants as those in Refs. [ref] , i.e., $a_πΣ=-2.00$, $a_K̅N=-1.84$, $a_ηΛ=-2.25$, and $a_K Ξ=-2.67$, and use them for the loop function in Eq. [ref] as well.

Identifying the two-pole structure of the $\Lambda(1405)$ using an SU(3) flavor filter · Introduction · 0.92
We shall develop the formalism and then we will apply the results to evaluate the wave functions in the ten coupled channels of the two $Λ(1405)$ states obtained in [ref] .

Couplings in coupled channels versus wave functions in the case of resonances: application to the two $\Lambda(1405)$ states · Introduction · 0.89

Compares with it 11 papers

To compare with the coupling strengths from the amplitude in the isospin basis as in Ref. [ref] , a factor $√(N_I)$ should be multiplied with the isospin multiplicity $N_I=2$ for $K̅N$ and $KΞ$, and $N_I=3$ for $πΣ$.] From this Table, one can see that the lower pole $Z_1$ strongly couples to the $πΣ$ state, whereas the higher pole $Z_2$ dominantly couples to the $K̅N$ state.

Internal structure of resonant Lambda(1405) state in chiral dynamics · $$ in chiral dynamics · 0.97
These pole positions are consistent with the LO [ref] , next-to-leading order (NLO) [ref] , and NNLO results [ref] .

Two-pole structures in QCD -- a universal phenomenon governed by chiral dynamics · Q1: Coupled channel effects · 0.93
The results of Eq. [ref] are similar to those obtained in Ref. [ref] , where, as shown in Ref. [ref] , a pole would appear close to the $K̅N$ threshold and with a width of the order of $200$.

How to unravel the nature of the $\Sigma^*(1430) (1/2^-)$ state from correlation functions · Considerations on the $Σ^*(1430)$ state · 1.00

Cites it as support 3 papers

Although such an effect on the observables should be examined in the future, this approximation is justfied by the chiral perturbation theory with the Weinberg-Tomozawa interaction [ref] , where $8_s$ and $8_a$ do not mix.

Study on Lambda(1405) in the flavor SU(3) limit in the HAL QCD method · Setups · 1.00
Then, the results may support its double pole structure proposed by the chiral unitary approach [ref] .

$\Lambda (1405)$ from lattice QCD · Conclusion and Discussions · 0.97
This is consistent with the dominance of the LO contribution observed in previous works [ref] .

Pole trajectories of the $\Lambda(1405)$ helps establish its dynamical nature · Results and discussions · 0.96

Cites it as background 27 papers

This can be mainly attributed to the two-pole structure predicted in the chiral unitary approach, which refers to a lower pole above the $πΣ$ threshold and a higher pole below the $K̅N$ threshold [ref] .

Pole trajectories of the $\Lambda(1405)$ helps establish its dynamical nature · Introduction · 0.82
Parameters of such models are typically fixed by fitting $K^-p$ reactions and threshold data, and the chirally motivated coupled-channel dynamics generates two poles in the complex energy plane [ref] .

Testing chiral unitary models for the $\Lambda(1405)$ in $K^{+}\pi\Sigma$ photoproduction · Introduction · 0.86
Recently, a few works to describe $Λ$(1405) as a baryon-meson resonance have been reported [ref] .

Lambda(1405) in a baryon-meson scattering with a bound state embedded in the continuum · Introduction · 0.96

Discussion

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