---
title: 'N(2080)3/2^-: Resonance, Molecule & Chiral Quartet'
url: https://www.emergentmind.com/topics/n-2080-3-2
type: topic
---

# N(2080)3/2^-: Resonance, Molecule & Chiral Quartet

\(N(2080)\,3/2^-\), often written \(N^*(2080)\), is a nucleon resonance with spin–parity \(J^P=3/2^-\); in molecular and hidden-strangeness studies it is also denoted \(P_s(2080)\). In the PDG (2012) the two-star \(N^*(2080)\) has \(J^P=3/2^-\) and is now called \(N^*(2120)\), while recent coupled-channel and effective-Lagrangian analyses continue to discuss a state near \(2.08\) GeV under the \(N(2080)\,3/2^-\) label. Across the literature represented here, the state is treated in three main ways: as a conventional \(s\)-channel nucleon resonance in \(K\Lambda(1520)\), \(K\Sigma\), and \(\phi N\) production; as an \(S\)-wave \(K^*\Sigma\) hadronic molecule and hidden-strange pentaquarklike state; and as the negative-parity member of a mirror-assigned chiral quartet [1302.0468] [2412.19559] [2302.14308] [1003.2834].

## 1. Identification, nomenclature, and empirical status

The resonance is consistently assigned \(J^P=3/2^-\) in the effective-Lagrangian analyses of \(\vec\gamma p\to K^+\Lambda(1520)\), \(\pi^-p\to K^0\Lambda(1520)\), \(\pi^-p\to\phi n\), and \(\gamma p\to K\Sigma\) [1007.3141] [1302.0468] [2404.11078] [2504.05811]. In hidden-strangeness coupled-channel work it carries \(I(J^P)=\tfrac12(3/2^-)\), and the 2024 study of vector–baryon dynamics explicitly identifies it as a nucleon with a hidden strange quark content, in analogy to the \(P_c\) states discovered by the LHCb collaboration, under the notation \(P_s(2080)\) [2412.19559].

Its empirical status has long been loose. The 2010 photoproduction study compared extracted parameters with a PDG estimate \(M\sim2080\) MeV and \(\Gamma\sim300\) MeV, described there as poorly known [1007.3141]. The 2018 molecular decay study used the PDG [2016] value \(\Gamma_{\rm tot}(N(2080))=250\pm130\) MeV as a benchmark [1805.06843]. The 2013 hadronic-production analysis noted that in the PDG (2012) the two-star \(N^*(2080)\) is now called \(N^*(2120)\), while retaining the older label for consistency with earlier photoproduction fits [1302.0468]. This coexistence of \(N^*(2080)\), \(N(2080)\,3/2^-\), \(N^*(2120)\), and \(P_s(2080)\) reflects a literature in which the state is simultaneously a resonance candidate, a hadronic-molecule candidate, and a still-evolving spectroscopy entry.

## 2. Extracted masses, widths, and \(K\Lambda(1520)\) phenomenology

A central phenomenological arena for the state is \(\Lambda(1520)\) production near threshold. In the effective-Lagrangian treatment of \(\vec\gamma p\to K^+\Lambda(1520)\), the nonresonant background consists of the contact term, \(t\)-channel \(K\) exchange, and \(s\)-channel nucleon pole terms, while the \(s\)-channel \(N^*(2080)\) pole is added as a \(J^P=3/2^-\) contribution [1007.3141]. In that framework, the total amplitude is decomposed as \(T_{\rm tot}=T_{\rm bg}+T_{N^*}\), and the forward-angle bump around \(E_\gamma\sim2.1\) GeV is produced by the interference term \(2\,\mathrm{Re}\{T_{\rm bg}T_{N^*}^*\}\) [1007.3141].

Representative parameter determinations reported in the literature are summarized below.

| Context | Parameters | Note |
|---|---|---|
| LEPS six-parameter fit | \(M_{N^*}=2138\pm4\) MeV, \(\Gamma_{N^*}=168\pm10\) MeV | \(\chi^2/\mathrm{d.o.f.}\simeq1.4\) [1007.3141] |
| LEPS eight-parameter fit | \(M_{N^*}=2115\pm8\) MeV, \(\Gamma_{N^*}=254\pm24\) MeV | \(\chi^2/\mathrm{d.o.f.}\simeq1.2\) [1007.3141] |
| Coupled-channel pole | \(\sqrt{s_p}\simeq2071-i\,35\) MeV | \(\Gamma_R\approx70\) MeV [2412.19559] |
| \(\pi^-p\to\phi n\) fit | \(M_R=2080\) MeV, \(\Gamma_R=99\) MeV | fixed in fit [2404.11078] |
| \(\gamma p\to K\Sigma\) fit | \(M_R=2080\) MeV, \(\Gamma_R=144\pm7\) MeV | main fit [2504.05811] |

The same \(K\Lambda(1520)\) channel also constrains the strong decay vertex. In the best eight-parameter fit to the LEPS data, the \(N^*\to K\Lambda(1520)\) couplings are \(g_1=1.4\pm0.3\) and \(g_2=5.5\pm1.0\), which was interpreted as indicating a rather strong \(N^*\to K\Lambda(1520)\) decay [1007.3141]. In \(\pi^-p\to K^0\Lambda(1520)\), a related effective-Lagrangian analysis took \(M_{N^*}=2115\) MeV and \(\Gamma_{N^*}=254\) MeV and obtained \(g_{N^*(2080)N\pi}=0.14\pm0.04\), with \(\chi^2/{\rm dof}\approx1.1\); the corresponding branching fraction was quoted as \({\rm Br}(N^*\to N\pi)\approx(2.9\pm1.6)\%\) [1302.0468]. The same study found that in \(pp\to pK^+\Lambda(1520)\) the \(K\Lambda(1520)\) invariant-mass spectrum and the Dalitz plot exhibit a pronounced bump near \(M_{K\Lambda^*}\approx2.08\) GeV [1302.0468].

A persistent caveat already appeared in the 2010 photoproduction work: although inclusion of \(N^*(2080)\) yields a fairly good description of the LEPS differential cross section data, serious discrepancies appear when the model is compared to the photon-beam asymmetry measured by LEPS [1007.3141].

## 3. Effective descriptions and the \(K^*\Sigma\) molecular scenario

Two distinct but partially overlapping theoretical languages dominate the modern discussion. The first is tree-level effective-Lagrangian phenomenology with a spin-\(3/2\) Rarita–Schwinger field. A representative electromagnetic and hadronic interaction set for a \(J^P=3/2^-\) state \(R\equiv N(2080)\) is
\[
L_{\gamma NR}^{3/2^-}
= - i e\,\frac{g_{\gamma NR}^{(1)}}{2M_N}\,\bar R_\mu\,\gamma_\nu\,F^{\mu\nu}\,N
+ e\,\frac{g_{\gamma NR}^{(2)}}{(2M_N)^2}\,\bar R_\mu\,F^{\mu\nu}\,\partial_\nu N
+ \mathrm{H.c.},
\]
\[
L_{K\Sigma R}^{3/2^-}
= - \frac{g_{K\Sigma R}}{M_K}\,\bar\Sigma\,\gamma_5\,(\partial_\mu K)\,R^\mu
+ \mathrm{H.c.},
\]
with the usual spin-\(3/2\) propagator in the \(s\)-channel [2504.05811]. Closely related \(3/2^-\) vertices are used in \(\gamma p\to K^+\Lambda(1520)\), \(\pi^-p\to K^0\Lambda(1520)\), and \(\pi^-p\to\phi n\) [1007.3141] [1302.0468] [2404.11078].

The second language is the hadronic-molecule picture. In that interpretation, \(N(2080)\,3/2^-\) is an \(S\)-wave bound state of \(K^*(892)\) and \(\Sigma\), identified as the strange partner of \(P_c(4457)\) [2302.14308] [2504.05811]. Lin et al. assumed \(N(2080)\) to be a pure \(S\)-wave \(K^*\Sigma\) molecule with \(I(J^P)=\tfrac12(3/2^-)\), motivated by a small binding energy \(\epsilon\approx6\) MeV [1805.06843]. The 2025 \(K^{*+}\Lambda\) photoproduction analysis similarly quoted \(\epsilon\simeq(892+1193)\,{\rm MeV}-2080\,{\rm MeV}\simeq5\) MeV and used Weinberg’s compositeness criterion to fix the molecular coupling, obtaining \(g_{R\Sigma K^*}=1.72\) [2510.03673]. The 2023 \(K^*\Sigma\) photoproduction fit used the same value, \(g_{K^*\Sigma R}\simeq1.72\), together with a fitted width \(\Gamma_{N(2080)}=70.1\pm9.7\) MeV [2302.14308].

The most explicit dynamical realization of the molecular picture is the coupled-channel vector–baryon model of the 2024 \(P_s(2080)\) study. There, the channels are \(\rho N\), \(\omega N\), \(\phi N\), \(K^*\Lambda\), and \(K^*\Sigma\), projected onto total spin \(3/2\) and isospin \(1/2\) in \(s\) wave, with
\[
T(s)=\big[\,1-V(s)\,G(s)\big]^{-1}V(s).
\]
A pole in the second Riemann sheet is found at \(\sqrt{s_p}\simeq2071-i\,35\) MeV, and its dominant origin is the attractive \(K^*\Sigma\) channel lying just above threshold \((m_{K^*}+m_\Sigma\approx2085\ {\rm MeV})\) [2412.19559]. The extracted pole couplings make this dominance explicit: among \(\rho N\), \(\omega N\), \(\phi N\), \(K^*\Lambda\), and \(K^*\Sigma\), the \(K^*\Sigma\) coupling is by far the largest [2412.19559].

## 4. Decay patterns and channel couplings

Decay information is one of the sharpest discriminants among models. In the \(\Lambda(1520)\) photoproduction fit, the strong \(N^*\to K\Lambda(1520)\) vertex was parameterized by
\[
\mathcal{L}_{K\Lambda^* N^*}
=\frac{g_1}{m_K}\,\bar\Lambda^*_\mu\,\gamma_5\gamma_\alpha\,(\partial^\alpha K)\,N^{*\mu}
+\frac{i\,g_2}{m_K^2}\,\bar\Lambda^*_\mu\,\gamma_5\,(\partial^\mu\partial_\nu K)\,N^{*\nu}
+\mathrm{h.c.},
\]
and the best eight-parameter fit gave \(g_1=1.4\pm0.3\) and \(g_2=5.5\pm1.0\) [1007.3141]. The 2013 hadronic-production analysis used the same structure and reinforced the significance of the \(K\Lambda(1520)\) channel [1302.0468].

In the 2024 coupled-channel hidden-strangeness study, partial widths were grouped into vector–baryon, pseudoscalar–baryon, and pseudoscalar–baryon-resonance classes. The direct vector–baryon widths were quoted as \(\Gamma_{\rho N}=5.66\) MeV, \(\Gamma_{\omega N}=1.33\) MeV, \(\Gamma_{\phi N}=1.92\) MeV, \(\Gamma_{K^*\Lambda}=6.64\) MeV, and \(\Gamma_{K^*\Sigma}=49.97\) MeV, for a total vector–baryon width \(\simeq65.5\) MeV [2412.19559]. The total light-\(PB\) width was \(\simeq10.4\) MeV, with the largest ground-state channels \(K\Lambda\) and \(K\Sigma\), while the total \(PB\)-resonance width was \(\simeq24.6\) MeV, dominated by \(K^+\Lambda_1(1405)\) at \(17.16\pm2.71\) MeV and accompanied by \(K^+\Lambda_2(1405)\), \(\pi N^*(1535)\), \(\eta N^*(1535)\), and \(\pi N^*(1650)\) [2412.19559]. Summing these contributions yielded \(\Gamma_{\rm tot}\simeq100\) MeV, described there as being in good agreement with the width extracted from the pole [2412.19559].

A different molecular calculation by Lin et al. produced a broader decay pattern. For \(\Lambda_0=1.0\) GeV and \(\Lambda_1=1.2\) GeV, the quoted partial widths were \(\pi\Delta:82.6\) MeV, \(\phi p:19.2\) MeV, \(\omega p:11.3\) MeV, \(\rho N:3.8\) MeV, \(K\Lambda:3.7\) MeV, \(K\Sigma:1.4\) MeV, \(K^*\Lambda:2.4\) MeV, \(K\Sigma^*:7.3\) MeV, \(\pi N:0.2\) MeV, \(\eta p:0.4\) MeV, \(K\Lambda(1520):0.1\) MeV, \(K\Lambda(1405):8.0\) MeV, and \(K\pi\Sigma\) (three-body): \(41.3\) MeV, for a total of \(181.7\) MeV [1805.06843]. In that study, the leading branching fractions were \(B(\pi\Delta)\simeq45.5\%\), \(B(\phi p)\simeq10.6\%\), \(B(\omega p)\simeq6.2\%\), and \(B(K\Sigma^*)\simeq4.0\%\) [1805.06843].

These results differ substantially in both total width and dominant channels. This suggests sensitivity to the assumed dynamics: one framework emphasizes \(K^*\Sigma\), \(K\Lambda(1405)\), and other hidden-strangeness channels [2412.19559], whereas another gives a large \(\pi\Delta\) component and a sizeable \(K\pi\Sigma\) three-body mode [1805.06843]. The conventional \(K\Lambda(1520)\) fits emphasize instead the strong \(K\Lambda(1520)\) vertex and a relatively small \(N\pi\) branching fraction [1007.3141] [1302.0468].

## 5. Production channels and characteristic observables

The state has been invoked in a broad range of production reactions, with different observables isolating different aspects of its dynamics. In \(\pi^-p\to\phi n\), Wang, Zhou, and Liu treated \(\rho\)-exchange in the \(t\)-channel and nucleon exchange in the \(u\)-channel as background, and the \(N^*(2080)\) as an \(s\)-channel signal term [2404.11078]. With \(M_R=2080\) MeV and \(\Gamma_R=99\) MeV fixed, and \(g_{\pi NN^*}g_1\equiv g_{N^*}^{3/2^-}=0.020\pm0.010\), the fit yielded \(\chi^2/{\rm d.o.f.}=1.05\) and displayed a clear threshold peak near \(W\simeq2.08\) GeV in the forward differential cross section at \(\cos\theta=1\) [2404.11078]. Numerically, \(d\sigma/d\cos\theta|_{\cos\theta=1}\sim0.1\)–\(0.2\,\mu{\rm b}\) in the immediate threshold region, whereas the background remains at the level of \(10^{-2}\)–\(10^{-3}\,\mu{\rm b}\); however, the authors stressed that the limited accuracy of the experimental data makes it difficult to determine the properties of the \(N^*(2080)\) from this process alone [2404.11078].

In \(\gamma p\to K\Sigma\), the 2025 effective-Lagrangian fit included \(N(2080)\,3/2^-\) as a strange molecular partner of the \(P_c\) states and found that its \(s\)-channel exchange contributes significantly to the bump structures at \(W\approx2080\) MeV in both \(\gamma p\to K^+\Sigma^0\) and \(\gamma p\to K^0\Sigma^+\) [2504.05811]. The fitted parameters for this state were \(M_R=2080\) MeV, \(\Gamma_R=144\pm7\) MeV, \(g_{\gamma N R}^{(1)}g_{K\Sigma R}=+0.630\pm0.040\), \(g_{\gamma N R}^{(2)}g_{K\Sigma R}=-0.880\pm0.040\), and \(\phi_R=+0.069\pm0.034\) rad [2504.05811]. The paper also emphasized coherent sums with \(N(2080)\,1/2^-\), non-molecular \(N^*\) states, and \(\Delta^*\) exchanges, and reported improved agreement with polarization observables \(P,\Sigma,T,O_x,O_z\) in the \(W=2.05\)–\(2.12\) GeV region [2504.05811].

In \(\gamma p\to K^*\Sigma\), the 2023 molecular analysis replaced any nucleon resonances in the \(s\) channel by the \(N(2080)\,3/2^-\) and \(N(2270)\,3/2^-\) molecules [2302.14308]. For \(N(2080)\,3/2^-\), the fitted values were \(g^{(1)}_{RN\gamma}=-0.12\pm0.04\), \(g^{(2)}_{RN\gamma}/g^{(1)}_{RN\gamma}=-1.60\pm0.19\), \(\phi_{N(2080)}=2.83\pm0.26\), \(\Gamma_{N(2080)}=70.1\pm9.7\) MeV, and \(\Lambda_R=1607\pm118\) MeV [2302.14308]. In the near-threshold region \(W\lesssim2.2\) GeV, the \(N(2080)\) exchange alone was found to account for roughly \(50\)–\(70\%\) of the cross section for both \(\gamma p\to K^{*+}\Sigma^0\) and \(\gamma p\to K^{*0}\Sigma^+\), and the beam, target, and recoil asymmetries \(\Sigma\), \(T\), and \(P\) were presented as sensitive diagnostics of the molecular hypothesis [2302.14308].

In \(\gamma p\to K^{*+}\Lambda\), the 2025 reanalysis incorporated \(N(2080)\,3/2^-\) through triangle loops based on the molecular \(K^*\Sigma\) picture and reported a considerable improvement in the overall description of the data [2510.03673]. The state was taken with \(M_R=2080\) MeV and \(\Gamma_R=141\) MeV fixed, while the loop regularization parameters were fitted as \(\Lambda_M=837\pm7\) MeV and \(\Lambda_B=733\pm9\) MeV [2510.03673]. The most visible effect was in the spin-density matrix element \(\rho_{00}\), where the full model nearly reproduced the upward bend at mid-angles for \(W=2041\) MeV and \(W=2086\) MeV, while the previous model without \(N(2080)\) underestimated the data [2510.03673]. The paper attributed this to interference with the dominant \(K\)-exchange, which provides extra spin-flip amplitude needed to raise \(\rho_{00}\) [2510.03673].

The 2024 \(P_s(2080)\) study generalized the experimental outlook beyond these channels. It argued that the dominance of \(K^*\Sigma\) in vector–baryon decays and of \(K\Lambda(1405)\) in pseudoscalar–baryon-resonance decays makes \(\gamma p\to K^*\Sigma\), \(\phi\) photoproduction near threshold, \(pp\to pK^+\Lambda(1405)\to pK^+\pi\Sigma\), \(\pi N\to K\Lambda(1405)\), and \(\Lambda_b\) decays with final \(K\pi\Sigma p\) especially suitable places to search for a bump around \(2080\) MeV in invariant-mass distributions [2412.19559].

## 6. Chiral-quartet placement, competing interpretations, and unresolved issues

A nonmolecular interpretation emerges from the mirror-assigned chiral-multiplet analysis of spin-\(3/2\) baryons. In that framework, the quartet \((\Delta(1920),\Delta(1940),N(2080),N(1900))\) is assigned to a \((1,\tfrac12)\oplus(\tfrac12,1)\) multiplet with \(N(2080)\) as the negative-parity member \(N^-\) [1003.2834]. The physical \(N^\pm\) and \(\Delta^\pm\) states arise from diagonalizing mirror-mixed mass matrices, with mixing angles determined by
\[
\tan2\theta_N=\frac{4\,m_0}{(g_1-g_2)f_\pi},
\qquad
\tan2\theta_\Delta=\frac{2\,m_0}{(g_2-g_1)f_\pi},
\]
and the quartet obeys the mass relations
\[
(m_{\Delta^+}+m_{\Delta^-})\ge(m_{N^+}+m_{N^-}),
\qquad
m_{\Delta^-}-m_{\Delta^+}=2\,(m_{N^+}-m_{N^-}) .
\]
For the fit called “Case (3-2),” the paper quoted \(\theta_N\simeq38^\circ\) and \(g_{\pi NN(2080)}\equiv g_{\pi N^-N^-}/\Lambda\approx2.2\ {\rm GeV}^{-1}\), leading to \(\Gamma_{N(2080)\to N\pi}\sim50\)–\(100\) MeV and a \(\Delta\pi\) width of a few tens of MeV [1003.2834]. In that reading, \(N(2080)\,3/2^-\) is neither a threshold molecule nor a hidden-strange pentaquarklike state, but part of a chiral quartet whose masses and \(\pi RR\) couplings are tied together by mirror symmetry.

Set against this are the hadronic-molecule studies, which emphasize an \(S\)-wave \(K^*\Sigma\) bound state with coupling fixed by Weinberg compositeness, a dominant \(K^*\Sigma\) pole residue, and hidden-strangeness decay patterns [1805.06843] [2302.14308] [2412.19559]. The effective-Lagrangian production analyses occupy an intermediate position: they often treat the state pragmatically as an \(s\)-channel spin-\(3/2\) resonance without committing to whether it is “a genuine \(3/2^-\) state or a dynamically generated object” [1302.0468].

Several unresolved points recur across these approaches. First, the extracted width is not stable across frameworks, ranging from \(\Gamma_R\approx70\) MeV in coupled-channel and \(K^*\Sigma\) photoproduction fits to \(\Gamma_R=144\pm7\) MeV in \(\gamma p\to K\Sigma\), \(\Gamma_R=168\pm10\) or \(254\pm24\) MeV in \(\Lambda(1520)\) photoproduction, and a PDG [2016] benchmark of \(250\pm130\) MeV [2412.19559] [2504.05811] [1007.3141] [1805.06843]. Second, even when the state improves cross sections, polarization observables remain constraining: the LEPS beam asymmetry in \(\gamma p\to K^+\Lambda(1520)\) remains in tension with the model, where the full result stays negative, \(\Sigma\sim-0.1\div-0.2\), while the published measurement hovers around zero with a slight positive tendency [1007.3141]. Third, several papers explicitly call for more precise data: the \(\pi^-p\to\phi n\) analysis cites limited data accuracy as an objective limitation and recommends correlation measurements at J-PARC, AMBER, and future HIKE and HIAF meson beam experiments [2404.11078], while the \(\gamma p\to K\Sigma\) study states that more abundant experiments, particularly for \(\gamma p\to K^0\Sigma^+\), are necessary to strengthen the constraints on theoretical models [2504.05811].

Taken together, the literature supports a robust phenomenological statement: a \(J^P=3/2^-\) nucleon structure near \(2.08\) GeV repeatedly improves descriptions of threshold and near-threshold observables in channels with \(K\Lambda(1520)\), \(K\Sigma\), \(K^*\Sigma\), \(\phi N\), and \(K^*\Lambda\) final states [1007.3141] [2302.14308] [2404.11078] [2504.05811] [2510.03673]. Whether that structure is best regarded as a conventional resonance, a \(K^*\Sigma\)-dominated hidden-strange hadronic molecule, or a member of a chiral mirror quartet remains an open spectroscopy problem.

Source: https://www.emergentmind.com/topics/n-2080-3-2