{"id":"256fd21d-aa65-45ea-906d-3dc10fc37bf7","arxiv_id":"2608.10717","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"PYTHIA8 pp simulations show the underlying-event region extends to 40-140 degrees in azimuth, with universal angular shape but energy-dependent Tsallis parameters from 62.4 GeV to 13 TeV.","lead":"PYTHIA8 simulations of proton-proton collisions show that the underlying event, the soft background around the hard scatter, occupies a wider angular window (40 to 140 degrees from the leading particle) than the standard transverse region, across energies from 62.4 GeV to 13 TeV. The paper maps how this window's temperature-like and non-extensive parameters evolve with energy and event shape, giving experiments a larger handle on soft QCD.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The claimed 40–140° extended-UE interval is not demonstrated at 62.4 GeV: the topology figures that define it start at 200 GeV, and the low-energy event selection is acknowledged to be strongly biased.","rationale":"The reader's weakest assumption is that PYTHIA8 Monash correctly describes the energy dependence of soft-QCD/MPI processes, and that external validation is missing for azimuthally resolved observables. I agree that this is a serious limitation and that the paper should be read as an MC prediction. However, there is a more direct, internal gap in the paper's own presentation: the two figures that establish the extended-UE definition via Eq. (5) do not include the 62.4 GeV point, while the abstract and summary explicitly claim the range starts at 62.4 GeV. The event-selection bias at that energy is acknowledged in Sec. II A, so the lower endpoint of the universality claim is supported neither by the defining figures nor by an unbiased sample. The concrete check above would settle whether the 40–140° interval actually holds at 62.4 GeV under the same generator and cuts. If it does not, the abstract's 'from RHIC to LHC' claim must be weakened; if it does, the remaining risk is exactly the generator-fidelity concern raised by the reader. No internal mathematical inconsistency was found, so the verdict remains conditional rather than reject or unverified.","tokens_in":19691,"tokens_out":10313,"duration_ms":108731,"concrete_test":"Re-run the PYTHIA8 8.317 Monash simulation at 62.4 GeV with exactly the Sec. II A cuts and produce Figs. 2 and 3 at that energy; verify whether \\bar{S}'_0(\\Delta\\phi)>\\bar{S}_0(MB) holds in every 20° bin with 2\\pi/9 \\le |\\Delta\\phi| < 7\\pi/9, and report the retained fraction of inelastic events. If it fails in the 40–60° or 120–140° bins, or if the accepted fraction differs sharply from the higher-energy samples, the extended-UE interval should be re-defined or the claim restricted to \\sqrt{s} \\ge 200 GeV.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is that the UE region extends beyond the conventional transverse side uniformly from 62.4 GeV to 13 TeV. The evidence for the extension comes from Eq. (5), \\bar{S}'_0(\\Delta\\phi)>\\bar{S}_0(MB), shown in Figs. 2 and 3. Those figures include 200 GeV, 900 GeV, 7 TeV, and 13 TeV, but not 62.4 GeV, even though the abstract claims 62.4 GeV as the lower endpoint. This is not a minor omission: Sec. II A states that at the lowest energies the forward-acceptance requirement retains a significantly smaller fraction of inelastic events, so the 62.4 GeV sample is a rare, forward-biased subset rather than a minimum-bias sample. If Eq. (5) fails in any 20° bin within 40°–140° at 62.4 GeV, the claimed universality of the enlarged window is false even inside the generator. In addition, because Eq. (5) is the only discriminator used, the extension is an operational property of the selected criterion rather than a data-calibrated statement; the sole external check (Fig. 7) is dN_ch/d\\eta, which is azimuthally integrated and cannot validate the \\Delta\\phi-resolved UE or Tsallis content.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript uses PYTHIA 8.317 with the Monash 2013 tune to study the azimuthal structure of charged-particle production in pp collisions from sqrt(s)=62.4 GeV to 13 TeV. Working in 20-degree sliding-angle bins relative to the leading charged particle, the authors extract Tsallis–Pareto parameters from the pT spectra in each bin, and study their dependence on collision energy and on event-shape classes defined by transverse spherocity and charged-particle flattenicity. The central claims are: (i) the underlying-event region extends beyond the conventional transverse side to 40–140 degrees, and this extended interval is valid across RHIC and LHC energies; (ii) the angular decomposition of event activity and topology is qualitatively universal in shape across energies; (iii) jetty events have larger q and smaller Ts than isotropic events; and (iv) on the Tsallis thermometer, the bins inside the extended UE region form a compact, energy-dependent cluster that moves away from the Boltzmann–Gibbs limit as collision energy increases. The paper is primarily a model-level phenomenological study; the only experimental comparison shown is dN_ch/dEta versus ALICE data in Appendix A.","tokens_in":19978,"tokens_out":3860,"duration_ms":40422,"significance":"If the claims are correct, the paper would provide a useful model-based reference for an enlarged UE acceptance window and establish an energy-dependent Tsallis reference for soft, MPI-dominated particle production in pp collisions. The presentation is generally transparent: the generator version, tune, soft-QCD settings, cuts, and fit ranges are stated, and the dN_ch/dEta comparison with ALICE data in Fig. 7 is a useful sanity check. The use of flattenicity as a forward-rapidity classifier that is less autocorrelated with midrapidity spectra, and the direct comparison of high-N_MPI with hard-scattering selections in Appendix C, are genuine strengths that sharpen the interpretation of the q and Ts azimuthal modulation. The principal weaknesses are evidential and logical rather than computational: the endpoint energy 62.4 GeV is absent from the key topology figures, the extended-UE criterion is essentially a definition, and the azimuthally resolved UE and Tsallis content are never validated against experimental data. These issues do not destroy the paper's model-level contribution, but they limit the strength of the 'validation' claim.","major_comments":[{"comment":"The abstract and Sec. IV claim that the extended UE interval 40–140 degrees is validated 'from RHIC to LHC energies', with 62.4 GeV as the lower endpoint, but Figs. 2 and 3 showing the defining quantities of Eq. (5) cover only 200 GeV, 900 GeV, 7 TeV, and 13 TeV; 62.4 GeV is absent. This omission is load-bearing because Sec. II.A states that the forward-acceptance requirement retains a significantly smaller fraction of inelastic events at RHIC energies, making the 62.4 GeV sample a rare, forward-biased subset. If Eq. (5) fails in any 20-degree bin within 40–140 degrees at 62.4 GeV, the claimed universality of the enlarged window is false inside the generator. Please either add the 62.4 GeV panels to Figs. 2 and 3 and verify Eq. (5) bin-by-bin, or explicitly restrict the claim to 200 GeV and above and adjust the abstract and conclusions accordingly.","section":"Sec. III.A and Figs. 2, 3; Sec. II.A"},{"comment":"The extended UE region is defined by Eq. (5), S0'(Delta-phi) > S0(MB). The demonstration in Sec. III.A that Eq. (5) holds for the displayed energies is therefore a consistency check of the definition, not an independent validation of the interval. The independent support should come from observables that are not used in the definition, such as the small angular derivatives of Ts and q in the extended window, Eq. (8), or the compact grouping of the (q, Ts) pairs in Fig. 6. Please state this distinction explicitly and provide a quantitative test of Eq. (8) within the 40–140 degree window, including a statement of the threshold on |dTs/dDelta-phi| and |dq/dDelta-phi| that counts as 'approximately zero'. As written, the text presents Eq. (5) as both the definition and the evidence, which is circular.","section":"Sec. II.D, Eq. (5); Sec. III.A"},{"comment":"The only external data comparison in the paper is dN_ch/dEta at midrapidity versus ALICE data (Fig. 7). That observable is azimuthally integrated and does not constrain the Delta-phi-resolved UE structure, the pT spectra in fixed Delta-phi bins, or the Tsallis parameters that carry the paper's central claims. The abstract and Sec. III use the word 'validating' for the extended UE window, but within the generator this is a prediction, not a data-calibrated statement. Please either add experimental comparisons of azimuthally resolved UE observables (for example, UE charged-particle density or scalar pT sum versus Delta-phi, or Delta-phi-resolved pT spectra from ALICE or CMS) or soften the wording from 'validating' to 'predicting within PYTHIA8 Monash'. This distinction is load-bearing because the model's energy trend for soft particle production is exactly what determines the claimed universality.","section":"Sec. II.A and Appendix A"}],"minor_comments":[{"comment":"The text contains the duplicated phrase 'The parameterT s The parameterT s sets the slope...'; the duplication should be removed.","section":"Sec. II.B, after Eq. (1)"},{"comment":"The caption as printed is garbled in the manuscript (for example, 'o-20ofull markers: 0s, one per o-140oboxes: ext. UE 40' is unreadable); please regenerate the caption and ensure axis labels and marker definitions are legible.","section":"Fig. 6 caption"},{"comment":"The sentence 'Since the leading particle enters this bin once per event and is by construction the hardest particle.' is a sentence fragment; it should be joined to the following sentence or rewritten.","section":"Sec. III.C, paragraph on full markers"},{"comment":"The manuscript states that 'approximately a billion minimum-bias events' are generated across seven energies, but does not list the number of events after selection per energy. Please provide per-energy event counts after all cuts so that the statistical uncertainties quoted in the figures can be evaluated.","section":"Sec. II.A"},{"comment":"The main text specifies SoftQCD:inelastic = on, while the Fig. 8 caption states SoftQCD:all = on; please make the generator settings consistent.","section":"Sec. II.A and Fig. 8 caption"},{"comment":"The definition of the 'conventional CDF UA definition' of the transverse side is not cited precisely; please add a reference or a parenthetical definition so the '66% larger' statement can be checked.","section":"Sec. II.D"}],"recommendation":"major_revision","confidential_remarks":"The paper is a sensible model-level study, and I would not reject it because the central physics question is legitimate and the computational setup is transparent. The main risk is overclaiming: the 62.4 GeV endpoint is not shown in the defining figures, the extended-UE criterion is partly self-referential, and no azimuthally resolved data comparison is provided. These are fixable by adding the missing panels, clarifying the logical status of Eq. (5), and softening the validation language. The current manuscript is close to publishable after those changes, so I recommend major revision rather than rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Punchline: this is a competent, systematic extension of the group's earlier 13 TeV sliding-angle study to √s from 62.4 GeV to 13 TeV, and the main claims hold up as PYTHIA8–Monash predictions. What's actually new: the energy evolution of the Tsallis parameters in 20° Δφ bins across seven collision energies, the compact (q, T_s) grouping inside the extended-UE window, and the spherocity-versus-flattenicity comparison. The authors treat the q–T_s anti-correlation carefully, distinguishing it from the joint growth of both parameters with √s, and they explicitly refine their own earlier conclusion: the UE moves away from the Boltzmann–Gibbs limit as √s increases, it is not universally near q≈1. Appendix C, separating N_MPI-driven from p̂T-driven selections, is a genuinely useful diagnostic. They also flag the low-energy event-selection bias themselves, which is to their credit.\n\nThe soft spots are real but not load-bearing. First, the extended-UE claim is partly circular: Eq. (5) defines the region as the set of bins where S'_0(Δφ) > S_0(MB), and the \"validation\" then consists of showing Eq. (5) holds. The independent support — the compact (q, T_s) cluster in Fig. 6 — is real, but it comes from the same generator. \"Validating\" overstates what is shown; a prediction consistently realized inside PYTHIA8 Monash is the accurate description. Second, the stress-test note is right: Figs. 2 and 3, which establish the criterion, start at 200 GeV, not 62.4 GeV. The 62.4 GeV sample appears in the Tsallis plots, but the authors acknowledge the forward-acceptance requirement keeps a much smaller, biased subset of inelastic events at RHIC energies, so the abstract's \"from RHIC to LHC\" phrasing is stronger than the displayed evidence. Third, the only external check is dN_ch/dη against ALICE, which is azimuthally integrated; the Δφ-resolved pT spectra that feed the fits are never compared to data. No code or fit tables are shipped either, which would have made the baseline reusable.\n\nWho it's for: anyone doing underlying-event measurements, Tsallis phenomenology, or event-shape classification in small systems gets a useful baseline — an enlarged UE window with roughly 66% more azimuthal acceptance, and PYTHIA8 reference behavior for (q, T_s) across √s, Δφ, and event class. I'd send it to a serious referee rather than desk-reject it, but I'd ask for one of two fixes: show Eq. (5) at 62.4 GeV, or soften the energy-range claim to 200 GeV–13 TeV; and ideally test one Δφ-resolved spectrum against data. Treat the paper as a prediction to check, not a measurement.","headline":"Competent PYTHIA8 extension of the sliding-angle UE framework to RHIC–LHC energies with a useful Tsallis baseline; the 62.4 GeV endpoint is missing from the defining figures and the extended-UE validation is partly self-referential.","tokens_in":20543,"tokens_out":8506,"would_cite":true,"duration_ms":73432,"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 paper claims that the underlying event in proton–proton collisions occupies an enlarged azimuthal window, $40^\\circ \\lesssim |\\Delta\\phi| \\lesssim 140^\\circ$, from RHIC to LHC energies, with a stable but energy-dependent…","keywords":["underlying event","Tsallis–Pareto distribution","non-extensive thermodynamics","PYTHIA8","transverse spherocity","flattenicity","proton–proton collisions","azimuthal correlation"],"falsifier":"Measure azimuthally resolved charged-particle $p_{\\rm T}$ spectra in real pp data at $\\sqrt{s}\\approx 200$ GeV, 900 GeV, 7 TeV and 13 TeV, fit Eq. (1) in $20^\\circ$ bins, and test whether $(q, T_{\\rm s})$ inside $40^\\circ < |\\Delta\\phi| < 140^\\circ$ form a compact cluster and whether the multiplicity and spherocity profiles are flat there; if the cluster is not compact or the profiles are modulated, the universality of the extended UE window would be falsified.","tokens_in":19483,"feed_emoji":"⚛️","tokens_out":6932,"duration_ms":60944,"temperature":0.7,"pith_summary":"This paper argues that the underlying event (UE) in proton–proton collisions is not confined to the conventional transverse side; across collision energies from 62.4 GeV to 13 TeV, the angular interval $40^\\circ \\lesssim |\\Delta\\phi| \\lesssim 140^\\circ$ is UE-dominated. Using the PYTHIA8 event generator, the authors fit Tsallis–Pareto distributions to charged-particle transverse-momentum spectra in fixed $20^\\circ$ azimuthal bins relative to the leading particle and show that, within this extended UE window, the fitted parameters $q$ and $T_{\\rm s}$ are jointly stable and group into a compact cluster in the $(q, T_{\\rm s})$ plane. The compactness is universal across energies for minimum-bias and isotropic event classes, while the cluster's location shifts; as $\\sqrt{s}$ increases, the UE moves away from the Boltzmann–Gibbs limit, refining the single-energy picture. If these findings hold against real azimuthally resolved data, they turn a one-energy observation into an energy-scaling statement and give experimenters a larger, more robust angular window for isolating soft-QCD activity.","feed_headline":"Underlying event extends beyond the usual transverse region","feed_subtitle":"PYTHIA shows the same wide underlying-event window and stable Tsallis parameters from 62.4 GeV to 13 TeV.","key_machinery":"The load-bearing tools are the thermodynamically consistent Tsallis–Pareto distribution, Eq. (1), fitted in fixed $20^\\circ$ azimuthal bins relative to the leading charged particle; the extended-UE criterion $\\bar{S}'_0(\\Delta\\phi) > \\bar{S}_0(\\rm MB)$, carried over from the sliding-angle method; and the Tsallis thermometer, the $(q, T_{\\rm s})$ plane in which each $\\Delta\\phi$ bin maps to a point. The identity $q-1 = -\\langle n\\rangle^{-1} + \\Delta n^2/\\langle n\\rangle^2$ ties $q$ to event-by-event multiplicity fluctuations and is used to interpret the near- and away-side excesses as fluctuation effects rather than pure spectral hardness. Together these provide a multi-differential map of geometry, event topology, and thermodynamics as functions of $\\Delta\\phi$, $\\sqrt{s}$, and event class.","core_discovery":"The paper's central claim is that the underlying-event region in pp collisions extends beyond the conventional transverse side, so that $40^\\circ \\lesssim |\\Delta\\phi| \\lesssim 140^\\circ$ ($2\\pi/9 \\le |\\Delta\\phi| < 7\\pi/9$) is a UE-dominated window valid from RHIC to LHC energies. The evidence is that both the $\\Delta\\phi$-differential charged-particle multiplicity and the average transverse spherocity $\\bar{S}'_0$ are flat in that window and satisfy $\\bar{S}'_0(\\Delta\\phi) > \\bar{S}_0(\\rm MB)$, while the Tsallis parameters extracted from the spectra are jointly stable there. For minimum-bias and isotropic event selections, the compactness of the $(q, T_{\\rm s})$ cluster is universal from $\\sqrt{s}=62.4$ GeV to 13 TeV, but its position moves toward higher $T_{\\rm s}$ and higher $q$ as energy increases, so the UE recedes from the $q\\to1$ limit. Jetty events break the compactness because fragmentation products contaminate the window, and the near- and away-side enhancements of $q$ are traced to the leading hard scattering rather than to the overall multiparton-interaction activity.","pith_inferences":["The compactness of the extended-UE cluster in the $(q, T_{\\rm s})$ plane could be repurposed as a quantitative figure of merit for how well any event-shape selection isolates the underlying event, beyond the two classifiers studied here.","If real azimuthally resolved data confirm the flat $q$ and $T_{\\rm s}$ profiles in the $40^\\circ\\!-\\!140^\\circ$ window, the same window could become a standard experimental definition for UE measurements in small collision systems.","The stated link between $q-1$ and multiplicity fluctuations suggests a direct experimental test: measuring the per-$\\Delta\\phi$ multiplicity variance and comparing the predicted $q(\\Delta\\phi)$ with the fitted values would probe the fluctuation mechanism itself.","The energy-dependent shift of the UE cluster away from the Boltzmann–Gibbs limit implies that system-size comparisons (pp versus larger nuclei) should quote the collision energy alongside the $(q, T_{\\rm s})$ pair, otherwise apparent medium effects may be confused with the trivial $\\sqrt{s}$ trend."],"forward_implications":["UE studies gain a larger, statistically more robust angular acceptance: $40^\\circ\\!-\\!140^\\circ$ instead of the conventional $60^\\circ\\!-\\!120^\\circ$ transverse side.","The extended UE region's $(q, T_{\\rm s})$ pair provides an energy-dependent reference point for the soft, multiparton-interaction-dominated component of pp collisions.","The UE is not universally close to Boltzmann–Gibbs; it moves away from $q\\to1$ as $\\sqrt{s}$ increases, so its near-equilibrium character is an LHC-energy statement.","Transverse spherocity and charged-particle flattenicity are complementary: spherocity separates jetty and isotropic events more strongly in $q$, while flattenicity yields a cleaner and more extended $q$–$T_{\\rm s}$ correlation.","The near- and away-side enhancement of $q$ is governed by the leading hard scattering rather than by the overall level of multiparton interactions, as shown by selections on $N_{\\rm mpi}$ and $\\hat{p}_{\\rm T}$."],"supporting_citations":[{"why":"Introduces the sliding-angle analysis and the extended UE definition that this work validates across energies.","marker":"[36]"},{"why":"Provides the PYTHIA8 event generator used for all simulated pp collisions.","marker":"[45]"},{"why":"Supplies the Monash 2013 tune that fixes the energy dependence of soft QCD and multiparton-interaction activity.","marker":"[46]"},{"why":"ALICE charged-particle multiplicity data used as the only direct experimental validation of the generator's energy trend.","marker":"[49–51]"},{"why":"Derives the relation between $q$ and multiplicity fluctuations used to interpret the non-extensive parameter.","marker":"[28]"},{"why":"Introduces the thermodynamically consistent Tsallis–Pareto distribution used for the spectral fits.","marker":"[32]"}],"fun_headline_variants":["Underlying event widens to 140° in pp collisions","UE window extends from 40° to 140° across energies","Stable Tsallis parameters reveal wider UE region","PYTHIA finds UE dominance beyond transverse side","New UE window: 40–140° from RHIC to LHC"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the PYTHIA8 Monte Carlo with the Monash tune correctly predicts how soft QCD and multiparton interactions evolve with collision energy, since only the inclusive multiplicity trend is compared with data while the azimuthally resolved spectra that feed the Tsallis fits are not checked against experiment.","fun_headline_variants_meta":{"raw":{"variants":["Underlying event widens to 140° in pp collisions","UE window extends from 40° to 140° across energies","Stable Tsallis parameters reveal wider UE region","PYTHIA finds UE dominance beyond transverse side","New UE window: 40–140° from RHIC to LHC"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000726,"raw_usage":{"total_tokens":3322,"prompt_tokens":1082,"completion_tokens":2240,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":698,"completion_tokens_details":{"reasoning_tokens":2156}},"tokens_in":698,"tokens_out":2240,"duration_ms":14362,"temperature":1.0,"reasoning_tokens":2156,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T18:46:11.338135+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure azimuthally resolved charged-particle $p_{\\rm T}$ spectra in real pp data at $\\sqrt{s}\\approx 200$ GeV, 900 GeV, 7 TeV and 13 TeV, fit Eq. (1) in $20^\\circ$ bins, and test whether $(q, T_{\\rm s})$ inside $40^\\circ < |\\Delta\\phi| < 140^\\circ$ form a compact cluster and whether the multiplicity and spherocity profiles are flat there; if the cluster is not compact or the profiles are modulated, the universality of the extended UE window would be falsified.","supporting_citations":[{"cited_title":"Varga, R","cited_arxiv_id":null,"evidence_quote":"Introduces the sliding-angle analysis and the extended UE definition that this work validates across energies."},{"cited_title":"Ortiz, A","cited_arxiv_id":null,"evidence_quote":"Provides the PYTHIA8 event generator used for all simulated pp collisions."},{"cited_title":"Ortiz and G","cited_arxiv_id":null,"evidence_quote":"Supplies the Monash 2013 tune that fixes the energy dependence of soft QCD and multiparton-interaction activity."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Derives the relation between $q$ and multiplicity fluctuations used to interpret the non-extensive parameter."},{"cited_title":"Gyulai, G","cited_arxiv_id":null,"evidence_quote":"Introduces the thermodynamically consistent Tsallis–Pareto distribution used for the spectral fits."}],"review_version":1}