{"id":"9f4e0ebb-e9c9-4934-8c0f-7781c0619840","arxiv_id":"2502.03277","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"A model calculation predicts that in pion-proton scattering to D−D0p, the 2.9 GeV D0p peak should come mostly from Λc(2910) rather than Λc(2940), testable at J-PARC.","lead":"This paper estimates the production rates of the charmed baryons Λc(2910) and Λc(2940) in pion-proton scattering using an effective Lagrangian model. It predicts that an upcoming J-PARC experiment should see the 2.9 GeV peak in the D0p invariant mass spectrum dominated by Λc(2910), not its heavier partner Λc(2940).","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The central claim rests on transferring a 1.1 GeV cutoff from compact Λc(2286) to spatially larger molecular states, although the paper itself says the molecular cutoff should be below 1 GeV; lowering it could flip the 2910/2940 dominance.","rationale":"Good-faith reading: the paper is a complete effective-Lagrangian estimate with a clean, testable J-PARC prediction, and the compositeness relation Eq. (12) gives some independent input for the molecular couplings. The weakest point is not the formalism but the numerical control of the one parameter that governs the relative size of the two resonance signals. The reader's weakest_assumption identifies the same issue. I do not see a demonstrated internal contradiction; the concern is that the paper's own stated physics (larger molecular size implies smaller cutoff) has not been implemented, and the published numbers do not show that the 2910-over-2940 dominance survives that change. Since the required test is a straightforward rerun of Fig. 7 with a second cutoff, the appropriate outcome is to keep the CONDITIONAL verdict: accept the prediction as a motivated model estimate, but require the two-cutoff calculation (or an experimental measurement at J-PARC) before treating the identity of the 2.9 GeV structure as established.","tokens_in":17980,"tokens_out":11101,"duration_ms":108678,"concrete_test":"Recompute the π− p → D− D0 p cross sections and the D0p invariant mass distribution at pπ = 14 GeV with two cutoffs: keep Λr = 1.1 GeV for Λc(2286) and the exchanged meson/nucleon vertices, but use Λr_mol = 0.8 and 0.9 GeV for vertices involving Λc(2910)/Λc(2940), as their larger molecular size implies. Compare the ratio of the 2910 and 2940 peak heights in Fig. 7 (and the integrated contributions) with the Λr = 1.1 result. If the 2910 peak remains several times larger than the 2940 peak for both Λr_mol values, the claimed dominance is robust; if the ratio drops below about one, the central claim fails. As a consistency check, restrict Λr to values for which σ(π− p → D*− Λc(2286)) at 13 GeV is below the 7 nb upper limit.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The load-bearing step is the transfer of the single cutoff Λr = 1.1 GeV, fixed by the reference process π− p → D*− Λc(2286), to the production and decay vertices of the molecular states Λc(2910) and Λc(2940) in Eq. (9). The paper's own closing paragraph of Sec. III.C states that, as ND* molecules, these states should be larger than a compact Λc(2286), so their cutoff should be smaller than 1 GeV and the cross sections would be smaller. This matters because the central claim is a dominance ratio, not an absolute rate: at pπ = 14 GeV the 2910 signal is about an order of magnitude above the 2940 signal in the D0p spectrum (Fig. 7), and the t-channel form factors [F(k1, m_D*, Λr)]^2 enter both signals with different D* virtualities. A smaller molecular cutoff changes those weights and the off-shell line shapes, so the predicted identity of the 2.9 GeV structure can change. The calibration is also only an upper limit: σ(D*− Λc(2286)) at 13 GeV is 2.59 nb for Λr = 1.1, below the 7 nb bound, and the quoted 1.0–1.2 GeV band includes Λr = 1.2 with about 9.7 nb, already above that bound. The central claim therefore depends on an unverified cutoff transferability that the authors themselves flag.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper uses an effective Lagrangian approach to compute cross sections for π−p→D*−Λc(2286), π−p→D−Λc(2286)/Λc(2910)/Λc(2940), and the three-body process π−p→D−D0p, assuming Λc(2910) and Λc(2940) are D*N molecular states with J^P=1/2− and 3/2−, respectively. The cutoff Λr is fixed to 1.1 GeV by requiring the reference cross section π−p→D*−Λc(2286) to lie below the experimental upper limit of 7 nb at Pπ=13 GeV. With this parameter, the authors predict the ratio of two-body cross sections at Pπ=30 GeV to be 1:4.8:1.42:0.26 for the D*−Λc(2286), D−Λc(2286), D−Λc(2910), and D−Λc(2940) channels, and estimate the total three-body cross section at Pπ=15 GeV to be (0.49+1.56−0.38) nb. The central claim is that the structure near 2.9 GeV in the D0p invariant mass spectrum of π−p→D−D0p should correspond to Λc(2910) rather than Λc(2940), which is proposed as a testable signal at J-PARC.","tokens_in":18340,"tokens_out":5389,"duration_ms":47735,"significance":"If the central prediction is reliable, it offers a concrete, falsifiable experimental signature that can distinguish between two molecular-state interpretations at J-PARC. The paper provides complete effective Lagrangians, explicit amplitudes, and a transparent parameter calibration, and it is commendable that the authors state the physical limitation that molecular states should have a smaller cutoff. However, the main prediction depends on two fragile inputs: the transferability of the cutoff Λr=1.1 GeV from a compact baryon to spatially larger molecular states, and the coupling constants inherited from the same authors' earlier model calculation (Ref. [57]). These dependencies are acknowledged or implicit in the manuscript but are not quantitatively explored, so the significance of the central claim is conditional rather than established.","major_comments":[{"comment":"The central claim that the structure around 2.9 GeV should be assigned to Λc(2910) rather than Λc(2940) rests on the relative magnitude of the two signals in the D0p invariant mass distribution, which is controlled by the form factor F(k,m,Λr) of Eq. (8) applied to all vertices with a single cutoff Λr=1.1 GeV. The authors themselves state at the end of Section III.C that, as ND* molecular states, Λc(2910) and Λc(2940) should have a larger size and therefore a cutoff smaller than 1 GeV, which would reduce the cross sections. Because the two resonances have different D* virtualities and off-shell line shapes, a lower cutoff for the molecular vertices can change the relative 2910/2940 weight and thus the identity of the predicted peak. No sensitivity study of the differential spectrum, or of the dominance ratio, to Λr in the molecular-vertex range below 1 GeV is provided. This is load-bearing for the main conclusion and should be addressed with a quantitative scan or a robust argument that the dominance persists.","section":"Section III.C, Eq. (9), Fig. 7"},{"comment":"The calibration of Λr uses only an upper limit, not a measured cross section, so it does not determine Λr uniquely; it merely imposes an inequality. Moreover, the uncertainty band quoted in Fig. 4(a) is not consistent with that upper limit: at Pπ=13 GeV the central value is 2.59 nb, but the +7.15 nb upper uncertainty reaches approximately 9.7 nb, exceeding the 7 nb bound from Ref. [66]. The range Λr=1.0–1.2 GeV is therefore only partially compatible with the reference data, and the corresponding uncertainty band in Fig. 8 for the three-body cross section overstates the allowed model variation. The authors should either restrict the admissible Λr range to values satisfying the bound or justify why including values above the bound is acceptable for estimating theoretical uncertainty.","section":"Section III.B, Fig. 4"},{"comment":"The couplings g_Λc(2910)ND, g_Λc(2910)πΣc, g_Λc(2940)ND, and g_Λc(2940)πΣc are fixed by the branching fractions quoted in Eq. (11), which are taken from Ref. [57], a previous paper by the same group using the same D*N molecular assignments. Consequently, the relative strength of Λc(2910) versus Λc(2940) in the D0p spectrum is not an independent prediction of the present calculation but is inherited from those earlier model outputs. This is not an internal inconsistency, but it means the proposed J-PARC measurement would test the combined molecular model rather than the production mechanism alone. The manuscript should state this inheritance explicitly and avoid presenting the 2910/2940 dominance as a new result that is independent of the model assumptions.","section":"Section III.A, Table I, Eq. (11)"}],"minor_comments":[{"comment":"The text says that the contributions from Λc(2286) and Λc(2940) are not shown in Fig. 6(a) because their cross sections are less than 1 fb, but the figure caption lists three curves corresponding to Λc(2286), Λc(2910), and Λc(2940). Please clarify which curves are actually plotted and why the caption is misleading.","section":"Section III.C, Fig. 6(a)"},{"comment":"There are several typographical errors, including 'whlie' near Eq. (5), 'Λc((2940))' in Section III.A, and 'crosse an order of magnitude' near Fig. 8. These should be corrected.","section":"Throughout"},{"comment":"The statement that Λr=1.1 GeV is 'safely under the experimental upper limit' should be qualified, since the quoted uncertainty band extends above the 7 nb bound; the phrase 'safely' is only true for the central value.","section":"Section III.B, Fig. 4"},{"comment":"The phase-space integral in Eq. (17) is written as dσ = ... d p0_5 d p0_3 d cosθ dη, but the integration limits and the definition of the five-body phase-space variables are not specified. Please provide the integration ranges or reference a standard phase-space parametrization so the numerical implementation is reproducible.","section":"Section II.B, Eq. (17)"},{"comment":"The phrase 'should correspond to Λc(2910) rather than Λc(2940)' is presented as a definitive conclusion. Given the model dependence and the admitted cutoff uncertainty, a conditional formulation (e.g., 'within the present model') would be more appropriate and would better match the actual strength of the argument.","section":"Abstract and Summary"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a standard effective-Lagrangian calculation, but the central claim is less novel than it appears because the relative 2910/2940 strength is largely fixed by the same group's earlier model (Ref. [57]). The main technical gap is the unquantified transfer of the cutoff Λr from the reference process to the molecular states, which the authors themselves flag. I recommend major revision: the authors should provide a sensitivity analysis of the D0p invariant mass spectrum with respect to a smaller molecular cutoff and restrict the uncertainty band to values consistent with the experimental upper limit. If those changes are made, the paper would be a useful phenomenological contribution for J-PARC."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Punchline: this is a workmanlike effective-Lagrangian calculation with one genuinely testable statement—at J-PARC, the 2.9 GeV peak in π−p→D−D0p should come from Λc(2910), not Λc(2940). The prediction is worth treating as a target to shoot at, but not as settled: the authors calibrate a single cutoff from an upper limit and then apply it to states that they themselves say should have a smaller cutoff. That is the load-bearing point.\n\nWhat is actually new: Ref [65] studied this reaction for Λc(2940) alone with JP=1/2±. This paper adds Λc(2910), treats Λc(2940) as 3/2−, and predicts the 2910 dominates the D0p spectrum by roughly an order of magnitude. The amplitudes are written out in full, the s/u/t channels are separated, and the Λr dependence is shown as an uncertainty band. The authors also flag their own cutoff caveat at the end of Sec. III.C, which is more transparent than most papers in this genre. That is real credit.\n\nSoft spots, in proportion:\n- The cutoff Λr=1.1 GeV is not determined by a measured cross section; it is chosen so that the reference π−p→D*−Λc cross section sits below a 7 nb upper limit. The quoted 1.0–1.2 GeV band actually includes parameter values that push that reference cross section above the same upper limit (2.59+7.15 nb at 13 GeV). So the calibration is weaker than it first appears.\n- Because Λc(2910) and Λc(2940) are loosely bound ND* molecules, the relevant cutoff should be below 1 GeV, as the authors concede. A smaller cutoff suppresses the molecular production vertices. Whether it flips the 2910/2940 dominance is not shown; since the central claim is exactly a ratio, this is the first thing I would ask for.\n- The branching-fraction inputs for the two resonances come from Ref [57], a previous paper by the same group. That is self-citation, but not a fatal flaw and not unusual here. It does mean the prediction is only as independent as that earlier model.\n\nBottom line: this is for the hadron-spectroscopy community and for J-PARC planning. It deserves a serious referee. My own prior is that the specific 2910-over-2940 statement is fragile, but the calculation is clear and the caveats are stated, so I would send it out and ask for a cutoff-sensitivity study with Λr below 1 GeV before the dominance claim is presented as robust.","headline":"Workmanlike effective-Lagrangian calculation with a testable J-PARC prediction, but the 2910-over-2940 dominance claim rests on a cutoff that the authors themselves say should be smaller.","tokens_in":18943,"tokens_out":3794,"would_cite":true,"duration_ms":33945,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"The structure near 2.9 GeV in the D0p mass spectrum of pion–proton scattering should be Λc(2910), not Λc(2940).","keywords":["Λc(2910)","Λc(2940)","D*N molecular states","effective Lagrangian","pion-induced reactions","hadron molecules","D0p invariant mass","J-PARC"],"falsifier":"Measure the $D^0 p$ invariant mass distribution of $\\pi^- p \\to D^- D^0 p$ at J-PARC with $p_\\pi \\approx 13$–15 GeV; the claim predicts a peak near 2914 MeV with a total cross section around 0.5 nb and a $\\Lambda_c(2940)$ peak about ten times smaller. Finding the 2.9 GeV structure at the $\\Lambda_c(2940)$ mass, or measuring an upper limit well below 0.1 nb at that energy, would falsify the prediction.","tokens_in":17739,"feed_emoji":"⚛️","tokens_out":9334,"duration_ms":70166,"temperature":0.7,"pith_summary":"This paper predicts which of the two nearly degenerate charmed-baryon candidates, $\\Lambda_c(2910)$ and $\\Lambda_c(2940)$, should appear as the structure near 2.9 GeV in the $D^0 p$ invariant mass spectrum of $\\pi^- p \\to D^- D^0 p$ at J-PARC. Treating both states as $D^* N$ molecules with $J^P = 1/2^-$ and $3/2^-$, the authors compute the production amplitudes with an effective Lagrangian approach and fix the cutoff by the measured upper limit on $\\pi^- p \\to D^{*-} \\Lambda_c(2286)$. Their central numbers are a total cross section of $0.49^{+1.56}_{-0.38}$ nb at $p_\\pi = 15$ GeV, dominated by $t$-channel $D^*$ exchange, and a $\\Lambda_c(2910)$ signal in the $D^0 p$ spectrum about an order of magnitude larger than the $\\Lambda_c(2940)$ signal. If correct, the prediction turns a spectroscopic ambiguity into a concrete peak-position measurement that the J-PARC pion beam can test.","feed_headline":"The 2.9 GeV peak in pion-proton scattering should be Λc(2910)","feed_subtitle":"A J-PARC beam can distinguish the two charmed-baryon molecules by their D0p mass spectra.","key_machinery":"The argument is carried by effective-Lagrangian amplitudes for $s$-, $u$-, and $t$-channel exchange, with the $t$-channel $D^*$ meson exchange as the dominant mechanism. The central object is the form-factor cutoff $\\Lambda_r$ appearing in $F(k_i, m_i, \\Lambda_r) = \\Lambda_r^4 / [\\Lambda_r^4 + (k_i^2 - m_i^2)^2]$, fixed to 1.1 GeV by requiring the $\\pi^- p \\to D^{*-} \\Lambda_c(2286)$ cross section to stay below its experimental upper limit, and then applied unchanged to the molecular-state vertices. The $\\Lambda_c(2910)$ and $\\Lambda_c(2940)$ couplings to their $D^* N$ constituents come from the compositeness condition with binding energies 32 MeV and 6.2 MeV, respectively, and the decay couplings into $D^0 p$ are set by the decay widths and branching fractions of the two states. The decisive feature is that the $t$-channel $D^*$ exchange that produces the molecular states and feeds their $D^0 p$ decay favours the lighter, wider $\\Lambda_c(2910)$ over the heavier, narrower $\\Lambda_c(2940)$.","core_discovery":"On the paper's own terms, the central claim is that the expected 2.9 GeV enhancement in the $D^0 p$ invariant mass distribution of $\\pi^- p \\to D^- D^0 p$ should be attributed to $\\Lambda_c(2910)$, not to $\\Lambda_c(2940)$. With $\\Lambda_r = 1.1$ GeV determined from the 7 nb upper limit for $\\pi^- p \\to D^{*-} \\Lambda_c(2286)$ at $P_\\pi = 13$ GeV, the two-body cross sections at $p_\\pi = 30$ GeV stand in the ratios $1 : 4.8 : 1.42 : 0.26$ for $\\pi^- p \\to D^{*-} \\Lambda_c(2286)$, $\\pi^- p \\to D^- \\Lambda_c(2286)$, $\\pi^- p \\to D^- \\Lambda_c(2910)$, and $\\pi^- p \\to D^- \\Lambda_c(2940)$. In the three-body process, the intermediate $\\Lambda_c(2910)$ dominates the $t$-channel contribution over $\\Lambda_c(2940)$ by a factor of about 20, and in the final $D^0 p$ mass spectrum the $\\Lambda_c(2910)$ peak is roughly an order of magnitude stronger, with $\\Lambda_c(2286)$ serving as a smooth background. The authors conclude that a future J-PARC measurement of this reaction can distinguish the two molecular-state interpretations.","pith_inferences":["If, as the authors themselves note, the cutoff for the spatially larger molecular states should be smaller than the 1.1 GeV value fixed from $\\Lambda_c(2286)$, then all predicted $\\Lambda_c(2910)$ and $\\Lambda_c(2940)$ cross sections would shrink; whether $\\Lambda_c(2910)$ still dominates the 2.9 GeV peak is not guaranteed and should be rechecked at $\\Lambda_r \\lesssim 1$ GeV.","The same calibrated amplitudes could be carried over to other production channels that populate these two states, such as photoproduction off a neutron or $\\bar p p$ annihilation, where the predicted ratio pattern would serve as a cross-channel consistency test.","A line-shape analysis of the measured $D^0 p$ spectrum using the two resonances' widths (about 52 and 20 MeV) could distinguish a broad $\\Lambda_c(2910)$ bump from the narrower $\\Lambda_c(2940)$ even at modest statistics; the paper's claim implies the bump centroid sits near 2.91 GeV rather than 2.94 GeV."],"forward_implications":["At J-PARC pion momenta above roughly 13 GeV, the predicted $\\pi^- p \\to D^- D^0 p$ cross section is a few tenths of a nanobarn to a few nanobarns, so the process should be experimentally accessible.","The $D^0 p$ invariant mass spectrum should show its 2.9 GeV enhancement at the $\\Lambda_c(2910)$ mass, near 2914 MeV, with any $\\Lambda_c(2940)$ contribution about an order of magnitude smaller.","For the two-body channels at $p_\\pi = 30$ GeV, $\\Lambda_c(2940)$ production should be suppressed relative to $\\Lambda_c(2910)$ by a factor of roughly 5.5, a pattern that can be checked through $\\pi^- p \\to D^- \\Lambda_c(2910)$ versus $D^- \\Lambda_c(2940)$.","Because the $t$-channel $D^*$ exchange dominates, the angular and pion-energy dependence of the cross section should follow the $t$-channel propagator rather than the $s$- or $u$-channel shapes.","The smooth $\\Lambda_c(2286)$ contribution sits below the $D^0 p$ threshold and acts as a background, so subtracting it should cleanly expose the molecular-state peak."],"supporting_citations":[{"why":"Supplies the experimental upper limit of 7 nb for $\\pi^- p \\to D^{*-}\\Lambda_c$ at 13 GeV, used to fix the cutoff $\\Lambda_r$.","marker":"[66]"},{"why":"Provides the $D^*N$ molecular assignment with $J^P = 1/2^-$ for $\\Lambda_c(2910)$ and $3/2^-$ for $\\Lambda_c(2940)$, plus the branching fractions used to fix the decay couplings.","marker":"[57]"},{"why":"Sets up the $\\pi^- p \\to D^- D^0 p$ reaction with $t$-channel $D^*$ exchange, $s$-channel nucleon pole, and $u$-channel $\\Sigma_c^{++}$ exchange, including the value of $g_{D^*D\\pi}$.","marker":"[65]"},{"why":"Gives the compositeness condition used to determine the $\\Lambda_c^* N D^*$ coupling constants from the binding energies of the two molecular states.","marker":"[74, 75]"},{"why":"Establishes the experimental state $\\Lambda_c(2940)$ in the $D^0 p$ spectrum, whose mass and width enter as input.","marker":"[48]"},{"why":"Provides the newer state $\\Lambda_c(2910)$ and its resonance parameters, which anchor the predicted peak position.","marker":"[50]"}],"fun_headline_variants":["Λc(2910) wins over Λc(2940) for pion-proton peak","Pion scattering peak assigned to Λc(2910)","2.9 GeV bump in pion-proton scattering? It's Λc(2910)","Λc(2910) is the right 2.9 GeV charmed baryon"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the cutoff parameter $\\Lambda_r = 1.1$ GeV, calibrated on the compact $\\Lambda_c(2286)$ reference channel, also applies without reduction to the spatially larger $D^* N$ molecular states $\\Lambda_c(2910)$ and $\\Lambda_c(2940)$; the paper itself notes that a smaller cutoff would lower these cross sections and could change which resonance dominates the 2.9 GeV peak.","fun_headline_variants_meta":{"raw":{"variants":["Λc(2910) wins over Λc(2940) for pion-proton peak","Pion scattering peak assigned to Λc(2910)","2.9 GeV bump in pion-proton scattering? It's Λc(2910)","Λc(2910) is the right 2.9 GeV charmed baryon"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001121,"raw_usage":{"total_tokens":4855,"prompt_tokens":1326,"completion_tokens":3529,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":942,"completion_tokens_details":{"reasoning_tokens":3440}},"tokens_in":942,"tokens_out":3529,"duration_ms":24557,"temperature":1.0,"reasoning_tokens":3440,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-09T05:16:46.237899+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the $D^0 p$ invariant mass distribution of $\\pi^- p \\to D^- D^0 p$ at J-PARC with $p_\\pi \\approx 13$–15 GeV; the claim predicts a peak near 2914 MeV with a total cross section around 0.5 nb and a $\\Lambda_c(2940)$ peak about ten times smaller. Finding the 2.9 GeV structure at the $\\Lambda_c(2940)$ mass, or measuring an upper limit well below 0.1 nb at that energy, would falsify the prediction.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the experimental upper limit of 7 nb for $\\pi^- p \\to D^{*-}\\Lambda_c$ at 13 GeV, used to fix the cutoff $\\Lambda_r$."},{"cited_title":"Strong decays of the Λc(2910) and Λc(2940) in the ND* molecular frame","cited_arxiv_id":null,"evidence_quote":"Provides the $D^*N$ molecular assignment with $J^P = 1/2^-$ for $\\Lambda_c(2910)$ and $3/2^-$ for $\\Lambda_c(2940)$, plus the branching fractions used to fix the decay couplings."},{"cited_title":"Role of the Λ+ c (2940) in theπ− p→ D−D0 p reaction close to threshold","cited_arxiv_id":null,"evidence_quote":"Sets up the $\\pi^- p \\to D^- D^0 p$ reaction with $t$-channel $D^*$ exchange, $s$-channel nucleon pole, and $u$-channel $\\Sigma_c^{++}$ exchange, including the value of $g_{D^*D\\pi}$."},{"cited_title":"Observation of a charmed baryon decay- ing to D0p at a mass near 2.94-GeV /c**2","cited_arxiv_id":null,"evidence_quote":"Establishes the experimental state $\\Lambda_c(2940)$ in the $D^0 p$ spectrum, whose mass and width enter as input."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the newer state $\\Lambda_c(2910)$ and its resonance parameters, which anchor the predicted peak position."}],"review_version":1}