{"id":"3cb51b6d-b5ef-411a-aba4-803f253317cc","arxiv_id":"2501.01968","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"A preliminary measurement of the energy-energy correlator from the collinear to the back-to-back limit in archived ALEPH e+e- data shows agreement with PYTHIA6 and a track-based NNLL/NNNLL theory calculation.","lead":"This proceedings paper reports a first fully corrected measurement of the two-point energy-energy correlator (E2C) across the collinear and back-to-back limits, using archived ALEPH e+e- data from LEP at 91.2 GeV. If correct, it provides new constraints on QCD resummation in the Sudakov region and a benchmark for future lepton colliders such as FCC-ee.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The claim of a first fully-corrected E2C measurement is load-bearing on an unvalidated 2D Bayesian unfolding; in the sparse Sudakov region the result may reflect the MC prior, and the quoted 'excellent agreement' with PYTHIA6 could be partly circular.","rationale":"The paper is an honest, clearly labeled preliminary proceedings: it uses archived ALEPH data, presents a physically motivated observable, and explicitly states that the dominant systematics are unfolding-related. However, the central claim of a first fully-corrected measurement going from the collinear to the Sudakov limit is not adequately supported by the material actually presented. The measurement relies on a 2D Bayesian unfolding, but no closure tests, validation plots, or quantitative systematic tables are shown. This is especially concerning in the Sudakov region, where the event count is low and the unfolding is strongly prior-dominated. If the prior is the same PYTHIA6 sample used for comparison, the claimed 'excellent agreement' with PYTHIA6 is to some degree circular. The reader's weakest-assumption analysis identified the same core issue: unvalidated unfolding in the sparsely populated Sudakov bins. A closure test with an independent MC prior would settle whether the bias is real. Until that validation is shown, the measurement should be regarded as preliminary and conditional. Since this supports, rather than changes, the reader's CONDITIONAL verdict, no verdict adjustment is needed.","tokens_in":955,"tokens_out":681,"duration_ms":29420,"concrete_test":"Re-run the nominal 2D Bayesian unfolding on pseudo-data generated from an independent MC (e.g., PYTHIA8 or Herwig) with the nominal PYTHIA6 response matrix; compare the unfolded pseudo-data to the input truth in z bins, especially z>0.8 (Sudakov). If the deviation exceeds the quoted systematic uncertainty, the unfolding bias invalidates the fully-corrected claim. Also, check whether the PYTHIA6 MC shown in Fig. 1 is the same sample used as the unfolding prior; if so, recompute the data/MC ratio using an independent generator and quote the shift.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's central claim (Sec. 4) is a fully-corrected measurement spanning the collinear to back-to-back limit with excellent agreement to PYTHIA6 and theory. This rests on the 2D Bayesian unfolding introduced in Sec. 3/ref [19]. Two specific weaknesses: (1) No closure test, validation, or numerical systematic breakdown is shown. The Sudakov region (z near 1) is sparsely populated, so the unfolding is strongly regularized by the prior; if the prior is PYTHIA6, the data/MC agreement in the bottom panel of Fig. 1 is partly built in. (2) The systematic uncertainties from binning, iterations, and prior choice are described only qualitatively, with no table, so the reader cannot tell whether the quoted 'excellent agreement' in the Sudakov region is within the systematic envelope. The claim therefore is not independently testable from the proceedings.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript, a proceedings contribution to the 12th Large Hadron Collider Physics conference, reports an energy-energy correlator (E2C) measurement in e+e- annihilations at sqrt(s) = 91.2 GeV using archived ALEPH data from 1994. The observable is the projected two-point energy correlator as a function of z = (1 - cos(theta_L))/2, spanning from the collinear region near z = 0 to the back-to-back/Sudakov region near z = 1. Detector effects and energy smearing are corrected with a two-dimensional Bayesian unfolding procedure described in Ref. [19], and the result is compared with archived PYTHIA6 simulation and with a track-function theory calculation labeled as NNLL collinear plus NNNLL Sudakov. The paper's stated conclusion is that this is the first fully-corrected measurement spanning from the collinear to the back-to-back limit and that the data show excellent agreement with both the simulation and the theory.","tokens_in":5449,"tokens_out":8289,"duration_ms":78770,"significance":"If the result were supported by the required validation and quantitative uncertainties, it would be a valuable addition to the EEC literature: e+e- collisions provide a clean environment for studying the collinear-to-Sudakov transition without jet-radius cuts, and the Sudakov region is comparatively unexplored. The paper has concrete strengths: it uses archived open-format ALEPH data, it exploits the full event rather than jet-only particles, it uses a readable double-log presentation, and it compares against a theory prediction whose non-perturbative parameter Omega is derived from an external thrust extraction rather than fitted to these data. The central claims are not, however, independently testable from this proceedings version: the unfolding is not validated, systematic uncertainties are only qualitative, no numerical data points or covariance information are provided, and the theory curve references an unpublished manuscript. The agreement with PYTHIA6 is useful as a cross-check, but it is not a strong test of the measurement unless the prior dependence of the unfolding is demonstrated.","major_comments":[{"comment":"The central claim of a fully-corrected measurement rests on the two-dimensional Bayesian unfolding introduced in Section 1 and Ref. [19], but the paper shows no closure test, no study with an alternative prior, no sensitivity scan in iteration count or binning, and no table of systematic uncertainties. The Sudakov region near z = 1 is sparsely populated, so the result there is likely to be strongly regularized by the unfolding prior; if that prior is the same PYTHIA6 Monte Carlo used in the comparison, the good data-to-MC ratio in the left panel of Figure 1 is at least partly built in. Please add (i) a closure test in which pseudo-data generated with a different generator are unfolded and compared with the input truth, (ii) a numerical breakdown of uncertainties from binning, number of iterations, prior choice, track selection, and matching, and (iii) a table of the unfolded data points with their statistical and systematic covariances. Without these, the statements of 'excellent agreement' and 'fully corrected' cannot be assessed.","section":"Section 3, Figure 1"},{"comment":"The abstract and the Introduction state that the measurement uses 'all particles' in the event, while Section 2 states that only charged particles with pT above 0.2 GeV, at least four TPC hits, and |cos(theta)| < 0.94 are used. These are different observables: a charged-track E2C is not the same as the full energy-weighted EEC, and neutral energy is not negligible in hadronic Z decays. The manuscript must either use 'charged-particle' consistently or explain that the theory comparison is intentionally a track-function calculation for charged tracks. This distinction is also missing from Equation (2), where the sum over i,j is not specified as being over charged tracks, and where neither a 1/N_event normalization nor the E^-2 factor that appears in the figure label is present.","section":"Section 1 versus Section 2; Equation (2)"},{"comment":"The agreement with the track-function theory calculation is one of the two central claims, but the calculation is cited only as an unpublished manuscript in Footnote 4, with no arXiv number, no version, no description of scale choices, no matching prescription between the NNLL collinear and NNNLL Sudakov regions, and no theory uncertainty band. As written, the 'excellent agreement' with theory is not reproducible or falsifiable from the information in the paper. The authors should either provide a citation to a public write-up of the calculation, include the relevant theory details and uncertainties directly, or soften the conclusion until the calculation is available. This is particularly important in the Sudakov region, where the result is most sensitive to the non-perturbative input beyond Omega.","section":"Figure 1, right panel; Section 4"}],"minor_comments":[{"comment":"The definition of E2C(z) does not specify the exact normalization: the figure y-axis label includes 1/N_event and an E^-2 factor, but the equation shows neither. Please give the precise histogram definition, including the bin-width convention used in the double-log representation.","section":"Equation (2)"},{"comment":"The simulation is only described as 'Archived MC' in the figure and as 'archived PYTHIA6 MC' in the text. Please state the generator version, tune, and whether it is the same simulation used to build the response matrix, so that the degree of prior overlap in the unfolding is transparent.","section":"Section 3, left panel of Figure 1"},{"comment":"The manuscript contains several typographical and stylistic errors, including 'ALEPH1' in Section 2, 'to looks at' in the Introduction, and a hyphenation break in 'perturbativeandnon-perturbative' in the abstract; a careful proofread is needed.","section":"General"},{"comment":"Reference [19] should give the full publication details for the D'Agostini unfolding method; the phrase 'Technical report, DESY, Hamburg, 1994' is incomplete as a citation. The in-preparation theory manuscript should also be listed with a version or a preprint number once available.","section":"References"}],"recommendation":"major_revision","confidential_remarks":"The reader's conditional assessment is close to my own. The measurement is not circular in the sense that no theory parameter is fitted to these data, but the absence of unfolding validation is a genuine load-bearing gap, and the comparison to an unpublished theory makes the central claim fragile. I do not think rejection is warranted, because the archival-data approach is sound and the missing material is additive rather than conceptually impossible. The main recommendation to the editor is that a revised version should contain numerical data tables, closure tests, and a systematic breakdown before the 'fully corrected' claim is made. The discrepancy between 'all particles' and 'charged particles only' should also be fixed before approval, as it can confuse readers about what is actually measured."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"First, what's actually new: this is the first fully corrected EEC measurement in e+e- that spans the full phase space from collinear to the back-to-back/Sudakov region. That's a real step, not a repackaging. The clean e+e- environment lets them use all charged particles instead of jet constituents, and they display the result in a way that shows the free-hadron region in both limits. Using archived ALEPH data is a nice demonstration of open-data reanalysis. I also credit them for being upfront that this is preliminary and the systematics are conservative.\n\nThe soft spots are the usual proceedings ones, but they matter here because the central claim depends on them. There are no tabulated data points, no unfolding closure tests, and no quantitative systematic breakdown. The Sudakov limit is exactly where the 2D Bayesian unfolding is most vulnerable: the bins are sparsely populated and the prior (PYTHIA6) can dominate. So the 'excellent agreement' with PYTHIA6 in the ratio plot is partly a statement about the simulation you unfolded with, not an independent test. That doesn't make the measurement wrong—including the prior choice in the systematics is the right instinct—but it does mean the claim can't be verified from this proceedings. The theory comparison also leans on an unpublished manuscript, and 'excellent agreement' has no number attached.\n\nTo be fair, these limitations are expected for a proceedings, and the paper labels itself preliminary. The circularity concern is real but not a killer. The theory prediction uses Omega extracted from thrust as an external input, so the theory agreement is not fitting these data. If the full paper provides closure tests and released numbers, this should be a solid measurement.\n\nBottom line: worth a serious referee for the full analysis, and the proceedings is a legitimate progress report. I'd ask the authors to release the corrected data and the unfolding validation promptly. The result is the kind of benchmark that Sudakov resummation and FCC-ee studies need, so I want to see it done carefully.","headline":"A genuine first: a fully corrected E2C from e+e- spanning collinear to Sudakov, but the proceedings format hides the validation, so trust the full paper when it lands.","tokens_in":6038,"tokens_out":2428,"would_cite":false,"duration_ms":23512,"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":"First fully corrected energy-energy correlator measurement from $e^+e^-$ data spans the full angular range from collinear to back-to-back QCD.","keywords":["energy-energy correlator","back-to-back limit","Sudakov region","collinear limit","ALEPH archived data","e+e- annihilation","QCD","Bayesian unfolding"],"falsifier":"A closure test would settle it: take PYTHIA6 events, run them through the ALEPH detector simulation, unfold them with the same two-dimensional Bayesian procedure, and compare the result with the generator-level E2C. If the unfolded closure distribution deviates from the generator input by more than the quoted systematics in the Sudakov region ($z\\gtrsim 1/2$), the central agreement claim would not survive.","tokens_in":5101,"feed_emoji":"⚛️","tokens_out":11404,"duration_ms":64337,"temperature":0.7,"pith_summary":"This paper reports the first fully corrected measurement of the two-point energy-energy correlator (E2C) that spans the whole angular range from collinear emission ($z\\to 0$) to the back-to-back, Sudakov limit ($z\\to 1$) in $e^+e^-$ annihilation at $\\sqrt{s}=91.2$ GeV. Using archived ALEPH data, it includes all charged particles in the event rather than restricting to jets, so the same observable probes free-hadron, transition, and perturbative quark/gluon behavior twice: once near $z=0$ and again mirrored near $z=1$. The reason to care is that this gives QCD theory and Monte Carlo generators one continuous distribution that constrains perturbative resummation and non-perturbative hadronization in a single place, with real novelty in the relatively unexplored Sudakov region. The fully corrected distribution agrees with PYTHIA6 and with a track-function theory calculation combining NNLL collinear and NNNLL Sudakov resummation.","feed_headline":"First fully corrected energy correlator spans collinear to back-to-back QCD","feed_subtitle":"Using archived ALEPH data, the strong force now has a single measurement reaching the back-to-back limit.","key_machinery":"The central object is the projected two-point energy-energy correlator E2C($z$), an energy-weighted sum over pairs of particles separated by opening angle $\\theta_L$, binned in $z=(1-\\cos\\theta_L)/2$. The variable $z$ is what carries the argument: it maps the collinear limit to $z\\approx 0$ and the back-to-back limit to $z\\approx 1$, so the Sudakov region appears as a mirror image of the collinear region with its own free-hadron and perturbative subregions. The correcting machinery is a two-dimensional Bayesian unfolding that simultaneously removes detector effects in $z$ and in the energy product $E_iE_j$; because the collision energy is fixed at $\\sqrt{s}=91.2$ GeV, no explicit energy-scale correction is needed. Measuring with all particles instead of only jet constituents removes the jet-radius cutoff and is what lets one distribution cover the full collinear-to-back-to-back range.","core_discovery":"The central result is the first fully corrected E2C distribution, $\\frac{1}{N}\\sum_{i,j}\\frac{E_iE_j}{E^2}\\delta(z-z_{ij})$ with $z=(1-\\cos\\theta_L)/2$, corrected by a two-dimensional Bayesian unfolding and shown on a double-log scale from $z\\sim 10^{-4}$ to $z\\sim 1-10^{-4}$. The paper finds excellent agreement between the corrected data and the archived PYTHIA6 Monte Carlo, and between the data and a theory prediction combining NNLL collinear resummation for $z\\lesssim 1/2$ with NNNLL Sudakov resummation for $z\\gtrsim 1/2$, the latter using a Collins-Soper kernel extracted from lattice QCD and a non-perturbative parameter $\\Omega$ taken from the thrust distribution. The agreement holds across both the collinear and Sudakov free-hadron regions and the perturbative transition in between, making the result one of the first experimental constraints on QCD in the back-to-back limit.","pith_inferences":["Beyond the paper's stated claims, a quantitative comparison of the free-hadron plateau heights at $z\\approx 0$ and $z\\approx 1$ would directly test whether hadronization is universal between the collinear and back-to-back limits; the paper only notes that they are roughly compatible.","Because no closure or validation tests for the unfolding are shown, an independent check is to repeat the correction with an alternative unfolding method, for example iterative matrix inversion, and compare the Sudakov region bin by bin; the agreement would bound the prior dependence that the paper treats only qualitatively.","A ratio such as E2C($z$)/E2C($1-z$) would isolate perturbative contributions by canceling the non-perturbative regions at the two ends of the distribution; the paper does not present this construction, but its symmetric $z$ variable makes it a natural next step.","If the track-function prediction continues to hold with more data, the same observable could become a lattice-informed constraint on the Collins-Soper kernel, linking the measured Sudakov shape to transverse-momentum-dependent distribution physics."],"forward_implications":["The Sudakov limit of QCD gets an experimental benchmark that resummation calculations and event generators must reproduce in both shape and normalization, not just inside jets.","The $e^+e^-$ E2C can serve as a standard reference for energy-correlator measurements in hadronic collisions, since it is free of beam remnants, initial-state gluon radiation, and parton distribution functions.","Ratios of higher-point correlators to the E2C become a practical route to an $\\alpha_s$ determination from archived LEP data, addressing the gap left by the removal of event-shape extractions from the world average.","The same analysis pipeline can be applied to LEP 2 archived data and to future machines such as FCC-ee, where larger statistics would sharpen the Sudakov-region constraints.","Systematic uncertainties, stated by the authors as conservative, can be refined in later iterations of the analysis without changing the basic measurement."],"supporting_citations":[{"why":"Preceding ALEPH jet-substructure analysis whose generator comparisons motivate checking generators against the full E2C and which established reanalysis of the archived data.","marker":"[4]"},{"why":"Original definition of the N-point energy correlation functions in $e^+e^-$ collisions; the E2C measured here is the two-point case.","marker":"[5–8]"},{"why":"Supplies the multidimensional Bayesian unfolding procedure used to correct the measured distribution for detector effects and energy smearing.","marker":"[19]"},{"why":"Documents the open-data format through which the ALEPH data and simulation used here are archived and read.","marker":"[20]"},{"why":"Records the recent removal of $e^+e^-$ event-shape determinations from the strong-coupling world average, motivating the paper's proposed $\\alpha_s$ extraction from correlator ratios.","marker":"[21]"}],"fun_headline_variants":["First corrected energy correlator reaches back-to-back QCD","ALEPH data reveals QCD in back-to-back limit","Archived ALEPH data yields first back-to-back energy correlator","Energy correlator spans collinear to back-to-back with ALEPH"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The weakest assumption is that the two-dimensional Bayesian unfolding removes detector distortions and energy smearing without bias at every $z$, especially near the back-to-back limit where particle pairs are sparse and the prior strongly shapes the result.","fun_headline_variants_meta":{"raw":{"variants":["First corrected energy correlator reaches back-to-back QCD","ALEPH data reveals QCD in back-to-back limit","Archived ALEPH data yields first back-to-back energy correlator","Energy correlator spans collinear to back-to-back with ALEPH"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000827,"raw_usage":{"total_tokens":3615,"prompt_tokens":948,"completion_tokens":2667,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":564,"completion_tokens_details":{"reasoning_tokens":2593}},"tokens_in":564,"tokens_out":2667,"duration_ms":13343,"temperature":1.0,"reasoning_tokens":2593,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T11:41:28.308727+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A closure test would settle it: take PYTHIA6 events, run them through the ALEPH detector simulation, unfold them with the same two-dimensional Bayesian procedure, and compare the result with the generator-level E2C. If the unfolded closure distribution deviates from the generator input by more than the quoted systematics in the Sudakov region ($z\\gtrsim 1/2$), the central agreement claim would not survive.","supporting_citations":[{"cited_title":"Jet energy spectrum and substructure in𝑒+𝑒− collisions at 91.2 GeV with ALEPH Archived Data.JHEP, 06:008, 2022","cited_arxiv_id":null,"evidence_quote":"Preceding ALEPH jet-substructure analysis whose generator comparisons motivate checking generators against the full E2C and which established reanalysis of the archived data."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the multidimensional Bayesian unfolding procedure used to correct the measured distribution for detector effects and energy smearing."},{"cited_title":"Jet Substructure Studies with CMS Open Data.Phys","cited_arxiv_id":null,"evidence_quote":"Documents the open-data format through which the ALEPH data and simulation used here are archived and read."},{"cited_title":"Quantum Chromodynamics","cited_arxiv_id":null,"evidence_quote":"Records the recent removal of $e^+e^-$ event-shape determinations from the strong-coupling world average, motivating the paper's proposed $\\alpha_s$ extraction from correlator ratios."}],"review_version":1}