{"id":"d4bd0a99-89db-4f5a-9eed-ab4cd91c46be","arxiv_id":"2411.10104","paper_version":2,"verdict":"ACCEPT","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"First measurement of azimuthal correlations between prompt Lambda_c baryons and charged particles in pp collisions at 13 TeV shows a hint of larger low-pT associated yields than for D mesons.","lead":"The ALICE collaboration measured, for the first time, how charged particles cluster around a specific charm baryon, the Lambda_c, in proton-proton collisions. The data hint that these baryons are accompanied by more low-momentum particles than charm mesons, and current simulations do not reproduce the effect.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 2.7 sigma Lambda_c/D near-side yield ratio hinges on fixing the generalized-Gaussian beta to PYTHIA CR-BLC Mode 2; a free-beta or beta-scan refit is needed.","rationale":"I read the paper as a careful first measurement with no internal inconsistency or evident circular reasoning. The main concern is not about data quality or the feed-down treatment, which the paper handles with explicit systematic uncertainties, but about the observable definition used for the central claim. The near-side yield YNS is extracted through a generalized Gaussian whose shape parameter beta is fixed to PYTHIA 8 CR-BLC Mode 2, a model that the paper itself shows underpredicts the measured yields. Because the central result is a 2.7 sigma difference between Lambda_c and D mesons, and because the D-meson comparison comes from a separate analysis with its own fit conventions, a model-dependent beta can move the ratio without any change in the underlying data. The paper's existing cross-check with a von Mises function and the free-beta RMS are useful but do not directly test the sensitivity of the specific Lambda_c/D ratio across a range of beta values. The measurement itself is publishable and valuable; the conditional recommendation is that the yield-enhancement claim should be accompanied by a beta-scan stability test, or phrased with explicit dependence on the assumed peak shape.","tokens_in":32823,"tokens_out":7755,"duration_ms":90283,"concrete_test":"Re-fit the published baseline-subtracted Lambda_c and D-meson correlation distributions for 3 < pT(Lambda_c,D) < 5 GeV/c and 0.3 < passoc < 1 GeV/c (the Fig. 1/Fig. 2 data) using Eq. (3) with (a) beta free, (b) beta fixed to 0.5, 0.8, 1.2, 1.5, and 2.0, and (c) a von Mises peak shape. For each configuration compute YNS, YAS, and the Lambda_c/D yield ratio with the same systematic propagation as Sec. 4. If the 2.7 sigma deviation falls below about 2 sigma, or changes by more than the quoted 8-29% yield uncertainty under any beta within the range consistent with the data's fit quality, the central comparison is not robust to the shape assumption and the paper should state the effect as model-dependent.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central physics claim is the 2.7 sigma near-side yield enhancement for Lambda_c over D-meson triggers at 3 < pT < 5 GeV/c and 0.3 < passoc < 1 GeV/c. The extraction of that yield uses Eq. (3), where YNS is the integral of a generalized Gaussian whose tail behaviour is controlled by beta. Section 3.3 fixes beta to the value obtained by fitting PYTHIA 8 CR-BLC Mode 2, a baryon-formation model. This is load-bearing for two reasons: (i) for beta values in the quoted range 0.7-1.9, the generalized Gaussian has substantial tails, so YNS is not a local peak integral but depends on how much near-side tail is separated from the flat baseline and the away-side Gaussian; (ii) fixing beta from a model that is itself one of the under-predicting baryon hadronisation models (and that is being tested in the same paper) can bias YNS in the direction of that model. The systematic check described in Sec. 4 leaves beta free and takes an RMS over the same data, but this does not cover a systematic mismatch between the true near-side shape and the CR-BLC shape, nor does it guarantee that the D-meson reference from Ref. [27] used the same beta convention. If the true beta differs, the 2.7 sigma ratio and the Lambda_c/D yield comparison can shift without any change in the data.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the first measurement of azimuthal correlations between prompt Lambda_c+ baryons and charged particles in pp collisions at sqrt(s)=13 TeV with ALICE, using L_int=29.2 pb^-1 of Run 2 data. The correlation distributions are corrected for acceptance, efficiency, combinatorial background, secondary contamination, beauty feed-down, and Sigma_c(2455) feed-down, then fitted with Eq. (3) to extract near- and away-side yields and widths. The main physics result is a comparison with published D-meson correlations: for 3 < pT^{Lambda_c,D} < 5 GeV/c and 0.3 < pT^{assoc} < 1 GeV/c, the near-side associated yield for Lambda_c triggers is larger than for D-meson triggers, with a quoted deviation of 2.7 sigma. The paper also compares the extracted observables with PYTHIA 8 Monash, POWHEG+PYTHIA 8, PYTHIA 8 CR-BLC Mode 2, and JETSCAPE predictions, finding that all models underpredict the low-pT associated yields, and tests a SHM+RQM-inspired resonance contribution that cannot explain the data.","tokens_in":33135,"tokens_out":5795,"duration_ms":61935,"significance":"If correct, this is the first measurement of charm-baryon azimuthal correlations, a genuinely new observable that can discriminate between in-vacuum fragmentation and modified hadronization mechanisms. The paper is a standard ALICE analysis with a detailed systematic table (Table 1) and appropriately hedged claims (the word 'hints' is used, and the 2.7 sigma significance is explicitly 'limited'). The comparison with D mesons and with several models provides a useful, falsifiable benchmark for charm hadronization models. The strengths of the paper are the established analysis chain, the explicit treatment of feed-down and contamination corrections, and the quantitative comparison with multiple generators. The main weakness is the model-dependent fixing of the generalized-Gaussian shape parameter beta, which is load-bearing for the central yield comparison.","major_comments":[{"comment":"The central 2.7 sigma near-side yield enhancement for Lambda_c over D-meson triggers depends on the extraction of Y_NS from Eq. (3), where beta is fixed to the value obtained from PYTHIA 8 CR-BLC Mode 2. For beta in the quoted range 0.7-1.9, the generalized Gaussian has substantial tails, so Y_NS is sensitive to how much near-side tail is separated from the flat baseline. The systematic check in Sec. 4 leaves beta free and takes the RMS over the same data, but this does not cover a systematic mismatch between the true near-side shape and the CR-BLC shape, especially because the paper itself finds that CR-BLC underpredicts the measured yields. Also, the paper does not demonstrate that the D-meson reference from Ref. [27] used the same beta convention; if the two analyses used different beta prescriptions, the ratio could be biased. Please add a robustness test: extract Y_NS with beta fixed to the values obtained from Monash, JETSCAPE, or a free-beta fit, and quote the spread as an additional systematic; or explicitly show that the D-meson reference used the same beta values and that the ratio is insensitive to beta.","section":"Sec. 3.3, Eq. (3); Sec. 4"},{"comment":"There is an inconsistency between the data and model treatments in the comparison shown in Fig. 4. The data near-side yields are obtained with beta fixed to the PYTHIA 8 CR-BLC Mode 2 value, whereas the model predictions are fitted with beta left unconstrained ('the beta parameter was left unconstrained'). This asymmetry can change the extracted Y_NS for data relative to the models and may bias the conclusion that all models underpredict the yields. Please either fit the data and models with the same beta prescription, or quantify the effect of the differing prescriptions on the data-to-model ratios.","section":"Sec. 5.2, Fig. 4"},{"comment":"The paper quotes 'a deviation of 2.7 sigma' for the Lambda_c/D near-side yield ratio at 3 < pT < 5 GeV/c and 0.3 < pT^{assoc} < 1 GeV/c, but it does not state explicitly whether this significance includes only statistical uncertainties or the total (statistical plus systematic) uncertainties, nor how the correlations between the Lambda_c and D-meson measurements were propagated. Since this number is the primary quantitative claim of the paper, please specify the exact uncertainty treatment used to compute the deviation.","section":"Sec. 5.1"}],"minor_comments":[{"comment":"The notation '3 < p^{Lambda_c,D}_T < 5, GeV/c' contains a stray comma; also the symbol p^{Lambda_c,D}_T is introduced in the abstract before it is defined in the text.","section":"Abstract and Sec. 5.1"},{"comment":"The typical beta values are quoted as a range (0.7-1.9) without reporting the actual value used for each pT interval. A table or a sentence listing the beta values per interval would make the model dependence more transparent.","section":"Sec. 3.3"},{"comment":"The 'scale unc.' boxes in the figures are not defined in the captions; please state explicitly that these represent the Delta-phi-independent systematic uncertainties.","section":"Figure captions (Figs. 1-6)"},{"comment":"The 'PYTHIA 8 Monash+Reso' model is described in the text but does not appear to have a dedicated reference; if this is a new model variant developed for this paper, please provide more detail on the implementation, or cite a companion paper.","section":"Sec. 5.3"}],"recommendation":"major_revision","confidential_remarks":"The paper is a solid ALICE measurement with a well-documented systematic budget, and the central claim is appropriately hedged as a 'hint'. The main concern is the model-dependent fixing of beta in Eq. (3), which is load-bearing for the 2.7 sigma claim. The authors should be asked to provide a beta-robustness test or to demonstrate that the D-meson reference uses the same beta convention. This is a fixable issue within the scope of the paper and does not require rejection. The analysis is suitable for a journal in the field once these points are addressed."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"First measurement of prompt-Lambda_c-charged azimuthal correlations; the paper is careful and the claim is properly hedged, but the headline ratio's significance depends on a beta parameter pulled from PYTHIA CR-BLC. I'd send it to referees but ask the authors to show the free-beta behavior.\n\nWhat is new: the Lambda_c-charged particle dN/dDelta(phi) distribution, measured for the first time. The observable is genuinely sensitive to charm hadronization into baryons. The analysis methodology follows the established ALICE D-meson correlation chain, which is a labor-intensive and well-tested pipeline: sideband subtraction, mixed-event correction, feed-down removal with PYTHIA templates, and Sigma_c subtraction. The systematics in Table 1 are granular and mostly Delta-phi dependent where they matter. The paper also adds a useful test of SHM+RQM resonances, which is a nice touch.\n\nThe soft spots are proportionate. The main claim, a 2.7 sigma enhancement of the near-side associated yield for Lambda_c over D mesons at 3 < pT < 5 GeV/c and 0.3 < passoc < 1 GeV/c, is explicitly a hint, and the paper does not oversell it. The most load-bearing choice is fixing the generalized-Gaussian beta to PYTHIA CR-BLC Mode 2. The free-beta systematic is a step in the right direction, but a free-beta RMS on the same data does not cover a systematic offset between the true shape and the CR-BLC shape, nor does it guarantee that the D-meson reference [27] used the same beta convention. I would want to see a beta-scan plot, or at least the free-beta fit results reported, before treating the baryon/meson ratio as robust. The feed-down corrections rely on FONLL and PYTHIA templates, but those uncertainties are included, so that's minor. No circularity: yields are fitted per trigger, then compared.\n\nWho it's for: charm-hadronization specialists, ALICE followers, MC tune developers. It absolutely deserves peer review. I'd accept with a request to address the beta issue more transparently.","headline":"First Lambda_c azimuthal correlations are real and worth publishing, but the 2.7 sigma baryon/meson yield difference rests on a beta shape parameter fixed from PYTHIA CR-BLC; referees should ask for a beta-scan.","tokens_in":754,"tokens_out":597,"would_cite":true,"duration_ms":49007,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"First $\\Lambda_c^+$-charged-particle azimuthal correlations show a $2.7\\sigma$ near-side excess over D mesons at low $p_{\\rm T}$, indicating baryon-specific charm hadronisation.","keywords":["charm hadronisation","azimuthal correlations","Lambda_c baryon","prompt charm production","fragmentation","near-side associated yield","baryon-to-meson ratio","13 TeV pp collisions"],"falsifier":"A decisive test is to repeat the measurement with LHC Run 3 statistics and a data-driven, template-independent subtraction of beauty feed-down; if the $\\Lambda_c^+/D$ near-side yield ratio for $3<p_{\\rm T}<5$ GeV/$c$ and $0.3<p_{\\rm T}^{\\rm assoc}<1$ GeV/$c$ then becomes consistent with unity, the claimed $2.7\\sigma$ excess would be refuted.","tokens_in":32616,"feed_emoji":"⚛️","tokens_out":12576,"duration_ms":114815,"temperature":0.7,"pith_summary":"Charm quarks in proton-proton collisions can hadronise into mesons or baryons, and this paper asks whether the two paths leave different imprints on the particles produced alongside the charm hadron. It reports the first measurement of azimuthal correlations between prompt $\\Lambda_c^+$ baryons (produced in charm hadronisation rather than in beauty decays) and charged particles in pp collisions at $\\sqrt{s}=13$ TeV, using the angular separation $\\Delta\\varphi$ between the baryon and each associated particle as the probe. The central result is the comparison with D-meson-triggered correlations: for $3<p_{\\rm T}^{\\Lambda_c^+,{\\rm D}}<5$ GeV/$c$ and $0.3<p_{\\rm T}^{\\rm assoc}<1$ GeV/$c$, the near-side peak yield (particles moving roughly collinearly with the trigger) is larger for $\\Lambda_c^+$ triggers than for D-meson triggers by $2.7\\sigma$, with a similar excess on the away side. The paper interprets this as evidence for a softer fragmentation of the charm quark, or a different hadronisation process, when it forms a baryon, and shows that the tested Monte Carlo generators all underpredict the low-momentum associated yields.","feed_headline":"Charm baryons carry a 2.7-sigma excess of low-momentum partners","feed_subtitle":"First azimuthal correlations of Lambda_c in pp collisions point to softer charm fragmentation for baryons.","key_machinery":"The central object is the per-trigger azimuthal correlation $(1/N_{\\Lambda_c^+})\\,dN^{\\rm assoc}/d\\Delta\\varphi$, built by pairing each $\\Lambda_c^+$ candidate with charged particles (with $p_{\\rm T}^{\\rm assoc}>0.3$ GeV/$c$, $|\\eta|<0.8$) in the same event, dividing by mixed-event pairs, and then correcting for efficiency, secondary-particle contamination, beauty feed-down, and $\\Sigma_c(2455)$ decays. The quantitative comparison is carried by a fit of the baseline-subtracted distribution with a generalized Gaussian for the near-side peak, a Gaussian for the away-side peak, and a constant baseline; ratios of the fitted near-side yield, near-side width, and away-side yield against the D-meson values are the observables that carry the $2.7\\sigma$ difference. The generalized Gaussian's shape parameter $\\beta$ is fixed from a Monte Carlo prediction of the correlation shape, which is one of the model-dependent inputs needed to stabilise the fit.","core_discovery":"The paper establishes the first measurement of the per-trigger azimuthal correlation distribution between prompt $\\Lambda_c^+$ baryons and charged particles at midrapidity in pp collisions at $\\sqrt{s}=13$ TeV, for $\\Lambda_c^+$ transverse momenta $3<p_{\\rm T}<16$ GeV/$c$ and associated-particle momenta $p_{\\rm T}^{\\rm assoc}>0.3$ GeV/$c$. After subtracting the baseline, fitting the correlation peaks shows that in the charm-hadron momentum interval $3<p_{\\rm T}<5$ GeV/$c$ and for associated particles with $0.3<p_{\\rm T}^{\\rm assoc}<1$ GeV/$c$, the $\\Lambda_c^+$-triggered near-side yield exceeds the D-meson-triggered yield by $2.7\\sigma$; a comparable excess is seen on the away side. The models tested, including those that reproduce the $\\Lambda_c^+/D^0$ production ratio, underpredict these low-momentum yields, and adding the decay feed-down from unobserved heavier charm-baryon states does not remove the discrepancy. The authors conclude that the charm quark fragments more softly, or hadronises via a different mechanism, when the final state contains a baryon.","pith_inferences":["A testable extension: measuring the same correlations with higher-mass charm baryons such as $\\Xi_c^+$ or $\\Omega_c^0$ would show whether the soft-particle excess grows with strangeness, as the baryon-to-meson production ratios do.","A reader may infer that the near-side excess, if confirmed, would favour a softer fragmentation picture over coalescence, since coalescence models predict a reduction of jet-associated particles for a given $\\Lambda_c^+$ momentum.","An implication of the multiplicity discussion is that the measured rise of $\\Lambda_c^+/D^0$ with event multiplicity could be driven by more particles inside $\\Lambda_c$ jets rather than by more baryon production per se.","A practical cross-check is to measure the same correlation for non-prompt $\\Lambda_c$ baryons from beauty decays, isolating the largest model-dependent correction and testing the feed-down subtraction directly."],"forward_implications":["The $\\Lambda_c^+$ and D-meson fragmentation patterns differ at low momentum: the near-side yield excess of $2.7\\sigma$ for $3<p_{\\rm T}<5$ GeV/$c$ and $0.3<p_{\\rm T}^{\\rm assoc}<1$ GeV/$c$ is a direct jet-level signature of baryon-specific charm hadronisation.","The away-side excess indicates the effect extends beyond the charm jet to the recoiling (anti)charm quark, consistent with the charm quark having less energy after a softer fragmentation.","All tested generators underpredict the low-momentum associated yields even when they describe $\\Lambda_c^+/D^0$ ratios, so the observable provides a new discriminating constraint on hadronisation models.","For trigger $p_{\\rm T}>5$ GeV/$c$ the $\\Lambda_c^+$ and D-meson correlations agree, suggesting the hadronisation difference is confined to low and intermediate momentum.","The correlation results give a concrete way to connect the multiplicity-dependent baryon-to-meson enhancement to jet structure: the increase could come from more particles in $\\Lambda_c$-containing jets rather than from a higher baryon formation probability."],"supporting_citations":[{"why":"Supplies the D-meson-triggered azimuthal-correlation results and peak observables to which the $\\Lambda_c^+$ yields and widths are compared.","marker":"[27]"},{"why":"Provides the measured fraction of $\\Lambda_c^+$ from $\\Sigma_c(2455)$ decays, used to remove soft-pion contamination near $\\Delta\\varphi=0$.","marker":"[13]"},{"why":"Establishes the correlation-analysis recipe including mixed-event correction, primary-particle purity, the feed-down selection-bias factor, and the fit function.","marker":"[29]"},{"why":"Provides the colour-reconnection model whose near-side peak shape supplies the fixed $\\beta$ parameter and whose predictions are compared with the data.","marker":"[21]"},{"why":"Provides the Monte Carlo event generator used for efficiency, purity, and feed-down templates.","marker":"[38]"},{"why":"Proposes the unobserved charm-baryon resonance states whose decay feed-down is tested as an explanation for the excess.","marker":"[24]"},{"why":"Gives the measured longitudinal-momentum fraction of $\\Lambda_c^+$ in jets, cited as independent support for softer charm fragmentation into baryons.","marker":"[25]"},{"why":"Provides perturbative QCD beauty-production cross sections used to compute the prompt fraction in the feed-down subtraction.","marker":"[43-45]"},{"why":"Provides b-hadron fragmentation fractions used in the feed-down normalization.","marker":"[46]"}],"fun_headline_variants":["First Lambda_c correlations hint at softer charm fragmentation","Charm baryons pull extra low-pT partners in pp collisions","2.7σ: Lambda_c triggers have more soft partners than D","ALICE: charm baryons carry soft excess over D mesons","Charm baryon correlations: first look shows softer fragmentation"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The result assumes the Monte Carlo templates used to subtract beauty feed-down and $\\Sigma_c(2455)$ decays have the correct shape and normalization, and that fixing the near-side peak shape from one model prediction is safe; if either assumption fails, the near-side yield excess could be an artifact.","fun_headline_variants_meta":{"raw":{"variants":["First Lambda_c correlations hint at softer charm fragmentation","Charm baryons pull extra low-pT partners in pp collisions","2.7σ: Lambda_c triggers have more soft partners than D","ALICE: charm baryons carry soft excess over D mesons","Charm baryon correlations: first look shows softer fragmentation"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001383,"raw_usage":{"total_tokens":5722,"prompt_tokens":1191,"completion_tokens":4531,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":807,"completion_tokens_details":{"reasoning_tokens":4445}},"tokens_in":807,"tokens_out":4531,"duration_ms":32644,"temperature":1.0,"reasoning_tokens":4445,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T19:58:22.015563+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A decisive test is to repeat the measurement with LHC Run 3 statistics and a data-driven, template-independent subtraction of beauty feed-down; if the $\\Lambda_c^+/D$ near-side yield ratio for $3<p_{\\rm T}<5$ GeV/$c$ and $0.3<p_{\\rm T}^{\\rm assoc}<1$ GeV/$c$ then becomes consistent with unity, the claimed $2.7\\sigma$ excess would be refuted.","supporting_citations":[{"cited_title":"Investigating charm production and fragmentation via azimuthal correlations of prompt D mesons with charged particles in pp collisions at $\\sqrt{s} = 13$ TeV","cited_arxiv_id":"2110.10043","evidence_quote":"Supplies the D-meson-triggered azimuthal-correlation results and peak observables to which the $\\Lambda_c^+$ yields and widths are compared."}],"review_version":1}