{"id":"695926f5-373c-43d3-bbaf-9cfe2d4d55a1","arxiv_id":"2507.19332","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"low","formal_verification":"none","parameter_count":3,"one_line_summary":"First multiplicity-dependent measurement of charged K*(892) production in pp collisions at 13 TeV shows a 7-sigma suppression of the K*/K_S ratio from low to high multiplicity, mainly at low transverse momentum.","lead":"This paper reports the first measurement of charged K*(892) meson production in proton-proton collisions at 13 TeV, split by collision multiplicity. The key finding is a 7-sigma suppression of the K*/kaon ratio from low to high multiplicity events, the first clear sign of such an effect in small collision systems.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Load-bearing concern: multiplicity-independent A×ε is assumed on a check that is not shown; a residual efficiency slope could bias the 7σ K*/K_S suppression.","rationale":"The reader's weakest-assumption identification is correct: the multiplicity-independent A×ε is the most load-bearing premise because it directly enters the yield ratio that constitutes the central claim. The paper states that per-class A×ε values were obtained and found consistent, but the absence of the quantitative comparison makes it impossible to assess the size of the residual uncertainty; the check is referenced rather than demonstrated. My concern is not that the analysis is wrong, but that the 7σ and >3σ significances rest on this flatness assumption. Other potential issues (signal extraction, fSL) are secondary; the A×ε assumption also interacts with the use of the separate K_S dataset. A concrete test with per-class corrections or an embedding test can settle it. The CONDITIONAL verdict remains appropriate; if the per-class A×ε table is added and the ratio shift is negligible, the paper could be accepted.","tokens_in":28006,"tokens_out":11488,"duration_ms":118621,"concrete_test":"Ask the collaboration to provide the per-class A×ε values (or a closure test): re-derive the K*±/K_S ratio in classes I and X with per-class A×ε applied and with the inclusive A×ε; if the high-to-low double ratio shifts by more than the quoted per-point uncorrelated systematic uncertainty (~1–2%), the 7σ claim needs to be revised. Additionally, run an embedding test in real data: inject simulated K*± decays into events of class I and class X and compare the reconstructed efficiency ratio with the inclusive A×ε assumption; a deviation of >2% between the two classes would invalidate the flat-efficiency premise.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Sec. 3.2 states that A×ε values computed per V0M class are consistent with the inclusive INEL>0 correction, and therefore a single multiplicity-integrated A×ε is applied to all classes. The per-class numbers are not reported or quantified (only a reference to Fig. 2 of Ref. [20]), so the claimed flatness is not independently checkable from the preprint. This matters because the K*± reconstruction includes a V0 (K_S) whose finding efficiency depends on local track density; in the 0–1% V0M class the TPC occupancy is roughly an order of magnitude above INEL>0, and tracking/V0 efficiencies typically decrease by a few percent at low pT. The quoted 'global tracking efficiency' systematic (Table 2: 1.3–2.5%) is treated as correlated across classes, so it cancels in the K*/K_S ratio and does not protect against a residual multiplicity slope. If the true A×ε in class I were, say, 3% lower than assumed at low pT and class X 3% higher, the high-to-low double ratio would shift by ~6%, comparable to the size of the claimed low-pT suppression and to the uncorrelated systematic budget; the integrated 7σ significance would decrease accordingly. The denominator K_S yields are taken from Ref. [32], a separate analysis that may apply its own multiplicity-dependent corrections; any mismatch in the treatment of trigger-loss (fSL) or per-class efficiency between the two datasets enters the ratio directly. Since the central claim is the observation of a multiplicity-dependent suppression in a small system, this assumption is load-bearing and is not demonstrated with quantitative per-class comparisons in the paper.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The ALICE Collaboration reports the first measurement of K*(892)+- production at midrapidity (|y|<0.5) in pp collisions at sqrt(s)=13 TeV as a function of event multiplicity. The K*+/- is reconstructed via K*+/- -> pi+/- + K_S^0, with the K_S^0 reconstructed through its V0 topology. Raw yields are extracted from same-event invariant-mass distributions after subtracting an event-mixing background, with a non-relativistic Breit-Wigner plus an ad-hoc residual-background function used for the peak description. Corrections include a PYTHIA8+GEANT based acceptance-times-efficiency (A x epsilon), a per-class signal-loss correction f_SL, and a systematic-uncertainty budget split into correlated and uncorrelated sources. The paper reports pT-differential spectra, pT-integrated yields, mean pT, and K*+/K_S^0 ratios as a function of multiplicity, comparing with PYTHIA6, PYTHIA8, EPOS-LHC, and DIPSY. The central claim is a 7-sigma suppression of K*+/K_S^0 from low to high multiplicity, interpreted as the first clear observation of K*/K suppression in a small collision system, with the suppression concentrated at pT below about 2 GeV/c (double ratio deviating by more than 3 sigma from unity).","tokens_in":28282,"tokens_out":5541,"duration_ms":59577,"significance":"If the result holds, it establishes a multiplicity-dependent resonance suppression in pp collisions with far better precision than the earlier ~2 sigma hint from the K*(892)^0 channel, and it sharpens the empirical constraints on the possible existence and duration of a hadronic phase in small collision systems. The analysis is in several respects careful and model-independent in the relevant sense: the K*/K_S ratio is built from measured yields, the event-mixing background subtraction and the systematic budget with correlated/uncorrelated separation are standard and well documented, and the model comparisons are not fits that could by construction imprint the observed trend. The main risk is not circularity but a data-dependent correction assumption: the claim that A x epsilon is multiplicity independent is asserted but not quantitatively demonstrated, and the denominator K_S^0 yields come from a separate analysis with its own corrections. These points, if resolved, do not appear to invalidate the measurement but are required before the 7-sigma claim can be fully assessed.","major_comments":[{"comment":"The claim that the acceptance-times-efficiency correction has no multiplicity dependence is load-bearing but is not substantiated in this manuscript. The text states that per-class A x epsilon values are consistent with the inclusive INEL>0 correction and refers to Fig. 2 of Ref. [20], but that figure shows the inclusive correction, not the per-class values; no per-class A x epsilon values, compatibility test, or uncertainty on the flatness are reported. Because the K*+/- yields in every multiplicity class are corrected with the multiplicity-integrated A x epsilon, a residual multiplicity slope in the tracking or V0-finding efficiency would propagate directly into the K*+/K_S^0 ratios and the central 7-sigma suppression claim. The correlated systematic sources in Table 2 (for example the 1.3-2.5% global tracking efficiency) are treated as fully correlated across classes and therefore cancel in the ratio, so they do not protect against a multiplicity-dependent efficiency slope. The authors should report the per-class A x epsilon values and their uncertainties, or quantify the maximum possible multiplicity slope and assign an appropriate uncorrelated systematic uncertainty.","section":"Sec. 3.2"},{"comment":"The denominator of the central ratio, the K_S^0 yield, is taken from Ref. [32], which is a separate analysis with its own acceptance, efficiency, event-selection, and signal-loss corrections. The manuscript does not discuss how the K*+/- and K_S^0 corrections are harmonized with respect to the V0M class definitions, the rapidity coverage, the f_SL treatment, or the per-class efficiencies. Any mismatch between the two analyses' corrections enters the K*+/K_S^0 ratio directly and therefore affects both the magnitude of the suppression and the quoted 7-sigma significance. The authors should state explicitly how the denominator corrections were matched to those used for the K*+/- numerator, or estimate a systematic uncertainty for the possible mismatch.","section":"Sec. 4 (Fig. 4)"}],"minor_comments":[{"comment":"The sentence stating that the tail correction 'accounts for about 13% of the yield' does not indicate whether this fraction varies across pT and multiplicity bins or whether it carries an uncertainty; a short statement would help.","section":"Sec. 3.2"},{"comment":"The differential-yield formula is not reproduced in this paper; it is only referenced as Eq. 3 of Ref. [20]. Including the formula, or at least the explicit correction factors, would make the analysis self-contained.","section":"Sec. 3.2"},{"comment":"The definition of the significance shown in the lower panel of Fig. 5 is implicit; please state explicitly whether it is the signed deviation of the double ratio from unity divided by the quadrature sum of statistical and multiplicity-uncorrelated systematic uncertainties, and whether the pT bins are treated as independent.","section":"Sec. 4 (Fig. 5)"},{"comment":"Table 2 quotes multiplicity-averaged systematic uncertainties; since the 7-sigma claim is based on the uncorrelated part, showing the per-class uncorrelated uncertainties or at least their range would allow the reader to reproduce the significance statement.","section":"Sec. 3.3"},{"comment":"The notation 'INEL > 0' is sometimes written 'INEL>0' and the V0M class labels are introduced in Table 1 but not always defined at first use in figure captions; a consistent notation would improve readability.","section":"Sec. 2 and Sec. 4"}],"recommendation":"major_revision","confidential_remarks":"The central measurement is potentially very valuable, but the missing per-class A x epsilon demonstration and the use of a denominator from a separate analysis are standard internal checks that the collaboration can likely provide. If those checks confirm the flatness assumption and the harmonization with Ref. [32], the paper would be publishable in essentially its present form; the current manuscript, however, does not yet make those checks independently verifiable."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Two things to know. First, this is the charged-channel version of the ALICE K* measurement in pp, and it turns the old 2σ hint from K*0 into a 7σ suppression. Second, the result is probably right, but the headline significance rests on a multiplicity-independent acceptance-times-efficiency correction that is asserted more than demonstrated. I would send this to referees, and I would tell the referee to ask for the per-class A×ε numbers.\n\nWhat is genuinely new: the first multiplicity-dependent K*(892)± measurement at 13 TeV, reconstructed via K_S pi, with better precision than the previous K*0 analysis. The pT spectra, integrated yields, mean pT, and the low-pT double ratio (more than 3σ below unity for pT below 2 GeV/c) are presented cleanly. The systematic budget is detailed, with an explicit split between correlated and uncorrelated sources. The model comparisons are descriptive rather than fitted; EPOS-LHC reproducing the trend without afterburners is noted but not oversold, and the conclusion honestly leaves the hadronic-phase interpretation open. No circularity problem: the ratio is built from measured yields, and Monte Carlo is used only for efficiency corrections.\n\nThe soft spots are proportionate. The stress-test worry about A×ε is real but not fatal. The paper says the per-class A×ε values are consistent with the inclusive INEL>0 correction and refers to Fig. 2 of Ref. [20], but that figure is from the inclusive analysis — the per-class comparison is not shown. Since the denominator K_S comes from a separate analysis, relative efficiency slopes between numerator and denominator could enter the double ratio directly. A few-percent slope at low pT would be comparable to the claimed low-pT suppression. This is the kind of thing ALICE has almost certainly checked internally, but the preprint does not let the reader verify it. I would make that a referee request, not a rejection. The absence of data tables in the arXiv version is standard for ALICE, but for a result people will want to reweight, it is a minor practical annoyance.\n\nThe citation pattern is sound: it builds on the prior K*0, inclusive K*±, and strange-hadron analyses, and the self-references are all relevant prior measurements. This paper is for the small-system and resonance-production community, and also for phenomenologists who want a sharp new constraint on rescattering and model predictions. It deserves a serious referee. My recommendation: referee it, with one explicit request for per-class A×ε and per-class systematic tables in the final version.","headline":"First multiplicity-differential K*(892)± measurement in pp at 13 TeV; the 7σ K*/KS suppression is a real new result, with one load-bearing correction assumption the paper checks but doesn't show.","tokens_in":28871,"tokens_out":2373,"would_cite":true,"duration_ms":26791,"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":"The paper reports the first clear observation of $K^*(892)^{\\pm}$/$K_S^0$ suppression with event multiplicity in pp collisions at $\\sqrt{s}=13$ TeV, measured at $7\\sigma$ significance.","keywords":["K*(892) resonance","proton-proton collisions","multiplicity dependence","K*/K_S0 yield ratio","resonance suppression","hadronic phase","rescattering","core-corona hadronization"],"falsifier":"Recompute the corrected yields using acceptance-times-efficiency evaluated separately in each V0M multiplicity class; if the high-to-low K*/$K_S^0$ ratio then moves toward unity by more than the quoted uncertainties, the 7σ suppression claim would be refuted.","tokens_in":27754,"feed_emoji":"⚛️","tokens_out":10292,"duration_ms":86696,"temperature":0.7,"pith_summary":"This paper tries to establish that the yield of the short-lived $K^*(892)^{\\pm}$ resonance relative to the longer-lived $K_S^0$ decreases as proton-proton collisions at $\\sqrt{s}=13$ TeV become more multiply populated, with the drop measured at $7\\sigma$ significance. The suppression is concentrated at low transverse momentum: for $p_{\\rm T}\\lesssim 2$ GeV/$c$, the ratio of high-multiplicity to low-multiplicity yields deviates from unity by more than $3\\sigma$. If the result holds, it would mean that resonance suppression, a signature usually associated with rescattering in the hadronic medium formed in heavy-ion collisions, also occurs in small collision systems, pointing to a short-lived hadronic phase in pp events. The paper also shows that EPOS-LHC reproduces the trend without any hadronic afterburner, so the effect does not uniquely require rescattering as usually modeled.","feed_headline":"K* mesons fade in high-multiplicity pp collisions at 7σ","feed_subtitle":"First clear K*/K_S0 suppression in a small system, concentrated below 2 GeV/c.","key_machinery":"The load-bearing observable is the ratio of the $K^*(892)^{\\pm}$ yield to the $K_S^0$ yield, where $K^*(892)^{\\pm}$ is a short-lived vector meson ($\\tau\\approx 4$ fm/$c$) reconstructed via $K^{*\\pm}\\to \\pi^\\pm + K_S^0$ and $K_S^0\\to \\pi^+\\pi^-$. The denominator is a long-lived ground-state particle with similar quark content, so the ratio cancels common production factors and isolates resonance-specific losses. The paper extracts raw yields from $K_S^0\\pi^\\pm$ invariant-mass fits after event-mixing background subtraction, corrects them with acceptance-times-efficiency from a multiplicity-integrated simulation, and then forms the high-to-low multiplicity double ratio with per-class uncorrelated systematic uncertainties.","core_discovery":"The central claim is that, in pp collisions at $\\sqrt{s}=13$ TeV, the $K^{*\\pm}/K_S^0$ yield ratio falls from the lowest (70–100% V0M) to the highest (0–1%) multiplicity class, a suppression of $7\\sigma$ accounting for multiplicity-uncorrelated uncertainties; this is the first observation of K*/K suppression in a small collision system, upgrading the previous $\\approx 2\\sigma$ hint from neutral $K^{*0}$. The $p_{\\rm T}$-differential double ratio (highest multiplicity divided by lowest) is consistent with unity above about 2.5 GeV/$c$ and lies below unity by more than $3\\sigma$ for $p_{\\rm T}\\lesssim 2$ GeV/$c$, indicating that the suppression acts mainly on low-$p_{\\rm T}$ resonances. The paper’s own interpretation connects this to rescattering of decay products in a brief hadronic phase, while noting that EPOS-LHC, which contains no hadronic afterburner, reproduces the multiplicity trend through its core-corona treatment, leaving the physical origin open.","pith_inferences":["If the same analysis were repeated in p–Pb collisions at the same center-of-mass energy per nucleon, the multiplicity trend would show whether the suppression scales with charged-particle density or with collision-system size; the paper stops at pp.","A systematic comparison of resonances with different lifetimes ($\\rho(770)^0$, $\\Lambda(1520)$, $\\phi(1020)$) in the same pp dataset would map suppression as a function of lifetime, separating rescattering from regeneration and from color-reconnection effects.","A direct check of the multiplicity-independence assumption would be to publish per-class acceptance-times-efficiency tables, letting independent analyses recompute the corrected ratios from the same raw yields.","One testable prediction implied by the paper’s core-corona/EPOS-LHC agreement is that the suppression should appear already at moderate multiplicities rather than only in the extreme 0–1% bin; future binned data can check that."],"forward_implications":["The previous 2σ hint from neutral $K^{*0}$ becomes a 7σ effect in the charged channel, making resonance suppression a quantitative observable in pp collisions.","Any successful model of pp collisions must reproduce a low-$p_{\\rm T}$-concentrated K*/K decrease with multiplicity, not just an overall yield growth.","Because EPOS-LHC matches the trend without a hadronic afterburner, the suppression can no longer be taken by itself as proof of a hadronic phase in pp events; it also constrains core-corona hadronization models.","The measured yields and ratios can be used as input for estimating hadronic-phase lifetimes in small systems, extending the heavy-ion-based estimates to pp collisions."],"supporting_citations":[{"why":"previous $K^{*0}$ measurement at 13 TeV; provides the 2σ hint this paper upgrades and the direct comparison for $K^{*\\pm}$ results.","marker":"[19]"},{"why":"inclusive $K^{*\\pm}$ analysis establishing the reconstruction method, the acceptance-times-efficiency correction, and the signal-loss factor used here.","marker":"[20]"},{"why":"multiplicity-dependent $K_S^0$ yields used as the denominator in the $K^{*\\pm}$/$K_S^0$ ratios.","marker":"[32]"},{"why":"PYTHIA8 Monash 2013 tune; used for Monte Carlo simulations of acceptance and efficiency and as a model comparison.","marker":"[30]"},{"why":"EPOS-LHC event generator; its core-corona hadronization without afterburners is the model that reproduces the measured suppression trend.","marker":"[38]"},{"why":"$K^{*0}$ production in Pb–Pb collisions at 2.76 TeV; defines the heavy-ion reference pattern of resonance suppression against which the pp results are compared.","marker":"[14]"},{"why":"estimate of hadronic-phase lifetime from resonance ratios across systems; gives the interpretive frame for low-$p_{\\rm T}$ suppression as rescattering.","marker":"[17]"}],"fun_headline_variants":["K* suppression in pp collisions hits 7σ","First clear K*/K_S0 drop in small systems","High-multiplicity pp: K* mesons suppressed at 7σ","Low-pT K* resonances fade in dense pp events","K*/K_S0 ratio falls with multiplicity in pp collisions"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The correction for detector acceptance and reconstruction efficiency is computed in the multiplicity-integrated INEL>0 class and then applied to every multiplicity class, based on the paper’s statement that no multiplicity dependence of the correction is observed; if that statement is wrong, the per-class yields and the 7σ suppression would be biased.","fun_headline_variants_meta":{"raw":{"variants":["K* suppression in pp collisions hits 7σ","First clear K*/K_S0 drop in small systems","High-multiplicity pp: K* mesons suppressed at 7σ","Low-pT K* resonances fade in dense pp events","K*/K_S0 ratio falls with multiplicity in pp collisions"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000257,"raw_usage":{"total_tokens":1712,"prompt_tokens":1210,"completion_tokens":502,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":826,"completion_tokens_details":{"reasoning_tokens":416}},"tokens_in":826,"tokens_out":502,"duration_ms":5032,"temperature":1.0,"reasoning_tokens":416,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T17:55:06.403292+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Recompute the corrected yields using acceptance-times-efficiency evaluated separately in each V0M multiplicity class; if the high-to-low K*/$K_S^0$ ratio then moves toward unity by more than the quoted uncertainties, the 7σ suppression claim would be refuted.","supporting_citations":[{"cited_title":"Measurement of K$^{*}$(892)$^{\\mathrm{\\pm}}$ production in inelastic pp collisions at the LHC","cited_arxiv_id":"2105.05760","evidence_quote":"inclusive $K^{*\\pm}$ analysis establishing the reconstruction method, the acceptance-times-efficiency correction, and the signal-loss factor used here."},{"cited_title":"Tuning PYTHIA 8.1: the Monash 2013 tune","cited_arxiv_id":null,"evidence_quote":"PYTHIA8 Monash 2013 tune; used for Monte Carlo simulations of acceptance and efficiency and as a model comparison."},{"cited_title":"EPOS LHC: Test of collective hadronization with data measured at the CERN Large Hadron Collider","cited_arxiv_id":null,"evidence_quote":"EPOS-LHC event generator; its core-corona hadronization without afterburners is the model that reproduces the measured suppression trend."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"estimate of hadronic-phase lifetime from resonance ratios across systems; gives the interpretive frame for low-$p_{\\rm T}$ suppression as rescattering."}],"review_version":2}