{"id":"4922a04e-e083-4b79-8d7f-796c2bffc397","arxiv_id":"2412.15783","paper_version":2,"verdict":"ACCEPT","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":5,"one_line_summary":"ATLAS presents the first JES and JER measurements for anti-k_t R=0.2 and R=0.6 jets at 13 TeV, using a new direct-matching in situ calibration against R=0.4 jets.","lead":"This paper reports the first measurements of the energy scale and resolution of anti-k_t jets with radius parameters R=0.2 and R=0.6 in proton-proton collisions at 13 TeV, using 37 fb^-1 of ATLAS data. It introduces a new in situ calibration method that ties these jets to the well-calibrated R=0.4 jets, and shows that the resulting uncertainties are comparable to those of the standard jets.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Abstract reports (6 ± 0.5)% JER at pT = 300 GeV for central R = 0.2 jets but Section 8 reports (4 ± 0.5)%; the figure supports the abstract, so the conclusion misstates the headline resolution.","rationale":"I read the paper's central claim as a measurement of JES and JER for R = 0.2 and R = 0.6 jets with uncertainties comparable to R = 0.4 jets, enabled by the direct matching method. The reader's weakest-assumption — dependence on the R = 0.4 reference calibration and on only two in situ topologies — is a genuine limitation, but the paper mitigates it: the multijet and Z+jets topologies have complementary flavour composition and pT coverage, the associated systematic uncertainties (matching, isolation, JVT, MC generator) are propagated, and Section 7 explicitly validates the close-by-jet environment that is the main motivation for R = 0.2 jets. I therefore do not see the topology-universality issue as a demonstrated flaw in the central argument. The concrete problem I find is an internal inconsistency in the headline JER number: the abstract quotes (6 ± 0.5)% at pT = 300 GeV for central R = 0.2 jets, while the conclusion quotes (4 ± 0.5)% at the same pT. Figure 20(a) and the body text are consistent with the abstract value, so the conclusion likely contains a typographical error. Because the conclusion is the summary most readers will cite, this misstates the measured resolution by 50% relative and should be corrected before the paper is used as a reference. This does not overturn the measurement, but it warrants a conditional acceptance pending a numerical consistency check of all quoted results.","tokens_in":71945,"tokens_out":15447,"duration_ms":140553,"concrete_test":"Extract the fitted relative JER for R = 0.2 jets at pT = 300 GeV from the Figure 20(a) curve and the corresponding fit parameters reported in the text or auxiliary material. If the fitted value is approximately 0.06, as the abstract and the plotted curve indicate, then the Section 8 statement of (4 ± 0.5)% is a typo that must be corrected. The same check should be repeated for the R = 0.6 jets and for every numerical JES/JER value quoted in both the abstract and the conclusions to ensure full internal consistency.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The most concrete load-bearing issue is an internal inconsistency in the central JER result. The abstract states the relative energy resolution for central R = 0.2 jets ranges from (35 ± 6)% at pT = 20 GeV to (6 ± 0.5)% at pT = 300 GeV, while Section 8 (Conclusions) states the same quantity is (4 ± 0.5)% at pT = 300 GeV. Figure 20(a) and the surrounding text are consistent with the abstract value of about 6%, so the conclusion appears to contain a typographical error. This is not a deep methodological flaw, but it is load-bearing because most readers will cite the conclusion, and a 50% relative error in the headline resolution number undermines the paper's self-consistency. The methodological assumption flagged by the reader — reliance on the R = 0.4 reference jets and only two in situ topologies — is mitigated by the propagated R = 0.4 uncertainties, the MC generator comparison, and the dedicated close-by-activity study in Section 7. The numerical inconsistency is therefore the more immediate obstruction to trusting the paper's stated results.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents measurements of the jet energy scale (JES) and jet energy resolution (JER) for anti-k_t jets with radius parameters R=0.2 and R=0.6, using 37 fb^-1 of 13 TeV pp collisions recorded by ATLAS in 2015-2016. A new 'direct matching' in situ method calibrates AR jets against fully calibrated R=0.4 jets in Z+jet and dijet topologies. The paper reports JES uncertainties near 1% for 100-800 GeV central jets and JER values from (35±6)% at pT=20 GeV to about 6% at pT=300 GeV for central R=0.2 jets, with a dedicated study of close-by hadronic activity using 80.4 fb^-1 of 2015-2017 data. The central claim is that the direct matching method yields AR-jet JES uncertainties of similar magnitude to those of the reference R=0.4 jets.","tokens_in":72231,"tokens_out":3062,"duration_ms":18619,"significance":"If correct, the results are significant: they provide the first LHC calibration of anti-k_t R=0.2 jets, which are needed for substructure studies of boosted bosons and top quarks, and they generalize the in situ calibration approach by using R=0.4 jets as reference objects. The paper's strengths include a detailed decomposition of 69 JES and 101/102 JER uncertainty components, explicit closure tests with agreement typically within 0.5%, MC generator cross-checks with Sherpa and Herwig, consistency checks using chi-square metrics, and a close-by-activity study that validates the calibration in dense environments. The reliance on the R=0.4 reference jets is not circular, because those jets were calibrated independently in earlier ATLAS publications and the associated uncertainties are propagated; the main residual risk is the implicit assumption that the measured data/MC response difference is representative across the full phase space, which is mitigated by the MC modelling uncertainty and the demonstrated consistency of the two topologies. However, the paper contains internal inconsistencies in the concluding section that must be fixed before the results can be cited reliably.","major_comments":[{"comment":"The conclusion states that the relative energy resolution ranges from (35±6)% at pT=20 GeV to (4±0.5)% at pT=300 GeV for central R=0.2 jets, while the Abstract states (6±0.5)% at pT=300 GeV. Figure 20(a) and the surrounding text in Section 6.2 are consistent with the Abstract value of about 6%, not 4%. This is a load-bearing numerical inconsistency in the headline result: most readers will quote the value from the Conclusions, and a 50% relative error in the quoted resolution is material. The Conclusions must be corrected to match the Abstract and Figure 20, and the paper should be checked for any other occurrences of this number.","section":"Section 8 (Conclusions) vs. Abstract and Figure 20"},{"comment":"The Conclusions state that the full JER is 'determined using the direct balance method, where the resolutions are extracted by comparing asymmetries in energies of AR jets measured in data to those found in truth jet simulations, in the Z+jets and dijet topologies.' This is inconsistent with Section 6.2, where the direct balance method is defined using only dijet events; Z+jets events are used for the in situ JES calibration in Section 5.2, not for the JER measurement. The sentence should be corrected to refer only to the dijet topology, or to properly describe the separate roles of the two topologies.","section":"Section 8 (Conclusions), JER method description"}],"minor_comments":[{"comment":"The text in Sections 5.3.1 and 6.3.1 refers to a 'reducible set of 45 pT-dependent in situ uncertainty components,' while Section 5.3 states the total JES has 69 components; the relationship between the total count and the reducible set of 45 should be made explicit to avoid confusion.","section":"Section 5.3.1 and Figures 16/23"},{"comment":"The close-by-activity study uses 80.4 fb^-1 of 2015-2017 data, whereas the main JES/JER calibration uses 37 fb^-1 of 2015-2016 data; this is stated but could be emphasized more prominently because the two luminosity figures appear in close succession and readers may otherwise mistake the close-by study as part of the main calibration sample.","section":"Section 7"},{"comment":"In the random cones description, the text says the noise term is estimated as one-half of the central 68% confidence interval divided by sqrt(2); the derivation of the factor sqrt(2) from the pair difference in Eq. (4) is implicit and could be stated more explicitly for clarity.","section":"Section 6.1"},{"comment":"The sentence 'While this approach creates a dependency of the AR jets reconstructed from topoclusters at the LCW scale on R=0.4 jets reconstructed from topoclusters at the EM scale' is grammatically awkward; rewording would improve readability.","section":"Section 4"}],"recommendation":"minor_revision","confidential_remarks":"The numerical inconsistency in the Conclusions appears to be a typographical error rather than a deep methodological flaw; Figure 20 and the Abstract agree. The wrong statement about Z+jets in the JER method is also local and easily fixed. No concerns about circularity or novelty disclosure; the direct matching method is a reasonable extension of established ATLAS procedures. I recommend minor revision rather than rejection because the central methodology is sound and the required changes are localized to the concluding section and small textual clarifications."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a careful, much-needed calibration paper and I'd send it to review. The new result is real: first Run 2 energy scale and resolution measurements for anti-k_t R=0.2 jets, and first for R=0.6 above 7 TeV. The direct matching method—calibrating AR jets against fully calibrated R=0.4 jets in only Z+jet and dijet topologies—is a sensible technical simplification borrowed from heavy-ion work, and the paper is honest that it inherits the R=0.4 reference's systematics. The uncertainty decomposition is thorough: 69 JES components, propagated R=0.4 uncertainties, dedicated close-by activity study, and reduction schemes for users. Closure tests are within 0.5% except at low pT, where a non-closure uncertainty is added. The JER measurement uses the standard direct balance method with the noise term fixed from random cones, and the cross-checks with multiple generators are appropriate.\n\nThe one concrete problem is an internal inconsistency in the central JER headline number. The abstract says the relative resolution for central R=0.2 jets ranges from (35±6)% at pT=20 GeV to (6±0.5)% at pT=300 GeV. Section 8 (Conclusions) says the same quantity is (4±0.5)% at pT=300 GeV. Figure 20(a) and its surrounding text support the abstract value of about 6%. So the conclusion contains what looks like a simple typo, but it's load-bearing because many readers will cite the conclusion's number, and a 50% relative error in the final resolution is a real trap. This needs fixing before the paper is used.\n\nThe concern the reader raised—reliance on the R=0.4 reference and only two topologies—is real but not a flaw in the execution. The paper propagates the reference uncertainties, checks MC generator dependence, and adds a dedicated close-by activity study in Section 7. The assumption is acknowledged, and the uncertainty budget reflects it. I don't see a deeper circularity issue: the R=0.4 jets are calibrated in independent earlier work, and the in situ factors come from data.\n\nWho this is for: anyone doing boosted-object substructure with small-R jets in ATLAS Run 2, or anyone wanting correlation-aware JES/JER uncertainties for R=0.2/0.6 jets. The paper deserves a serious referee; given it's already in EPJC, in practice it needs only a typo fix and perhaps harmonization of abstract/conclusion numbers. My verdict: accept after revision.","headline":"Solid first Run 2 JES/JER for R=0.2 and R=0.6 jets with a new direct-matching calibration; the headline resolution number is inconsistent between abstract and conclusions and must be fixed.","tokens_in":72744,"tokens_out":1964,"would_cite":true,"duration_ms":20205,"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":"This paper calibrates anti-$k_t$ jets with radius parameters $R=0.2$ and $R=0.6$ to roughly the same precision as standard $R=0.4$ jets, using a new in situ method that matches them directly to $R=0.4$ reference jets in only two topologies.","keywords":["jet energy scale","jet energy resolution","anti-k_t jets","alternative radius jets","direct matching method","in situ calibration","close-by hadronic activity","LHC 13 TeV proton-proton collisions"],"falsifier":"A decisive check is to derive the same in situ correction in a third topology, such as $\\gamma$+jets, and compare the calibrated $R=0.2$ and $R=0.6$ jet energy scales with the $Z$+jets/dijet result: the paper's own closure tests show agreement within 0.5% to 1%, so a disagreement larger than the combined uncertainties would show that two topologies do not cover the full phase space. A second check is to re-derive the correction using 2017--2018 data and verify whether the claimed Run 2 applicability holds under higher pile-up conditions.","tokens_in":71757,"feed_emoji":"🎯","tokens_out":13391,"duration_ms":60105,"temperature":0.7,"pith_summary":"This paper calibrates the energy scale and resolution of anti-$k_t$ jets (the standard infrared-safe jet clustering algorithm used at the LHC) with radius parameters $R=0.2$ and $R=0.6$, using 37 fb$^{-1}$ of 13 TeV proton--proton collisions. Its central proposal is a new in situ 'direct matching method' that calibrates these alternative-radius jets against the already well-calibrated $R=0.4$ jets in only $Z$+jets and dijet events, instead of repeating the full multi-topology calibration for each radius. The paper claims that this is enough to bring the total jet energy scale uncertainty for both radii to roughly the same size as for the reference $R=0.4$ jets, about 1% for central jets with $100 \\lesssim p_T \\lesssim 800$ GeV. The measured relative energy resolution for central $R=0.2$ jets falls from $(35\\pm6)\\%$ at $p_T=20$ GeV to $(6\\pm0.5)\\%$ at $p_T=300$ GeV. These numbers matter because $R=0.2$ jets are the building blocks of boosted-object substructure measurements, while $R=0.6$ jets serve analyses that need a wider angular catchment.","feed_headline":"Narrow and wide jets now match standard jet calibration precision","feed_subtitle":"Direct matching transfers the proven R=0.4 jet calibration to narrow 0.2 and wide 0.6 jets.","key_machinery":"The central object is the direct matching in situ calibration. Alternative-radius jets are matched within $\\Delta R<0.2$ to fully calibrated anti-$k_t$ $R=0.4$ reference jets reconstructed from EM-scale topoclusters, and the correction $C(p_T^{\\mathrm{ref}},\\eta^{\\mathrm{AR}})=\\langle R_{\\mathrm{insitu}}\\rangle^{\\mathrm{MC}}/\\langle R_{\\mathrm{insitu}}\\rangle^{\\mathrm{Data}}$ is built from the average $p_T$ ratio in $Z$+jets and dijet events. This transfers the full $R=0.4$ calibration, including its propagated systematic uncertainties, onto the new radii without re-running the complete four-topology in situ program. For the resolution, the supporting machinery is the standard three-term parameterisation $\\sigma(p_T)/p_T = N/p_T \\oplus S/\\sqrt{p_T} \\oplus C$, with the noise term $N$ fixed from random cones in zero-bias data and the stochastic and constant terms $S$ and $C$ fitted from the dijet balance asymmetry. The close-by hadronic activity study uses the inverse charged fraction $r_{\\mathrm{trk}}=p_T^{\\mathrm{probe}}/p_T^{\\mathrm{trk}}$ as a calibration-independent probe of energy scale changes when other jets approach within $\\Delta R\\sim0.4$.","core_discovery":"The paper argues, on its own terms, that the energy scale of anti-$k_t$ jets with $R=0.2$ and $R=0.6$ can be established at the same precision as the standard $R=0.4$ jets. The load-bearing result is the direct matching method: each alternative-radius jet is matched to a fully calibrated $R=0.4$ jet, and a correction factor $C(p_T^{\\mathrm{ref}},\\eta^{AR})=\\langle R_{\\mathrm{insitu}}\\rangle^{\\mathrm{MC}}/\\langle R_{\\mathrm{insitu}}\\rangle^{\\mathrm{Data}}$ is derived from the $p_T$ ratio in $Z$+jets and dijet data and simulation. After statistical combination and smoothing in $(p_T,\\eta_{\\mathrm{det}})$, the total jet energy scale uncertainty for central jets is about 1% in the $100\\lesssim p_T\\lesssim800$ GeV range, with the $R=0.2$ budget dominated by propagated $R=0.4$ reference uncertainties and the low-$p_T$ $R=0.6$ budget by pile-up; the conclusion is that the uncertainty is of similar magnitude to that of reference jets. The resolution is determined by fixing the noise term from random-cone measurements and fitting the dijet direct-balance asymmetry; for central $R=0.2$ jets it decreases from $(35\\pm6)\\%$ at $p_T=20$ GeV to $(6\\pm0.5)\\%$ at $p_T=300$ GeV. The paper further claims that close-by hadronic activity shifts the $R=0.2$ scale in a way that is well modelled by Monte Carlo simulation, so no additional correction is needed when small jets are reclustered into large jets.","pith_inferences":["If the transfer works as cleanly as claimed, the same matching idea should calibrate other radii, such as $R=1.0$ or very small jets for high-pile-up running, and could be checked immediately against the dedicated large-radius calibration already published by the same experiment.","A structural limit is that this method's uncertainty can never be smaller than the reference $R=0.4$ calibration; an independent cross-check using single-particle-response calibrations, which the paper names as a future validation route, would expose any radius-dependent bias inherited from the reference.","The close-by activity study relies on charged-particle tracks, so a complementary test using calorimeter-only or neutral-sensitive observables would show whether the Monte Carlo modelling also holds for the neutral component of close-by radiation.","Since the calibration uses 2015--2016 data but is asserted to cover the whole Run 2, a natural extension is to check $Z$+jet balance or jet $p_T$ spectra in the higher-pile-up 2017--2018 data against these calibrations."],"forward_implications":["Measurements using $R=0.2$ and $R=0.6$ jets would inherit roughly the same jet energy scale systematic precision as standard $R=0.4$ jets, about 1% for central jets with $100\\lesssim p_T\\lesssim800$ GeV.","The direct matching method, requiring only $Z$+jets and dijet topologies, provides a lightweight route for calibrating any alternative jet radius in future datasets or at other experiments.","The published $R=0.2$ resolution figures (35% at 20 GeV decreasing to 6% at 300 GeV for central jets) set the uncertainty budget for track-assisted reclustering and boosted-object analyses built from small-radius jets.","The close-by hadronic activity results imply that no additional jet energy scale correction is needed when $R=0.2$ jets are reclustered into large-radius jets, and that the quoted uncertainties cover boosted topologies up to $p_T\\sim2.4$ TeV."],"supporting_citations":[{"why":"Supplies the fully calibrated $R=0.4$ reference jets and the propagated in situ JES uncertainty categories that the direct matching method relies on.","marker":"[4]"},{"why":"Provides the standard 13 TeV $R=0.4$ calibration chain (pile-up, absolute JES, global sequential calibration) adapted to alternative-radius jets.","marker":"[15]"},{"why":"Provides the statistical combination method and numerical inversion used to combine the $Z$+jets and dijet in situ corrections.","marker":"[10]"},{"why":"Supplies the random cones and direct balance methodology for the jet energy resolution measurement, together with out-of-cone corrections.","marker":"[14]"},{"why":"Provides the low-pile-up 2010 data comparison used for the pile-up-free noise term systematic uncertainty in the resolution measurement.","marker":"[12]"},{"why":"Shows the precedent for the matching-to-reference calibration technique in heavy-ion jet measurements that motivated the direct matching method.","marker":"[5]"},{"why":"Is the single-particle-response calibration used to interpret low-$p_T$ response differences and named as a future validation of the direct matching method.","marker":"[17]"}],"fun_headline_variants":["ATLAS calibrates narrow and wide jets to 1% scale precision","Small and large radius jets match R=0.4 calibration precision","New method measures jet energy scale for R=0.2 and 0.6","Jet resolution for R=0.2 spans 35% to 6% across pT"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the already-calibrated $R=0.4$ reference jets are unbiased and that the data-to-simulation response differences measured in $Z$+jets and dijet events represent all environments where $R=0.2$ and $R=0.6$ jets are used; if either assumption fails, the alternative-radius jet energy scale inherits the same hidden bias.","fun_headline_variants_meta":{"raw":{"variants":["ATLAS calibrates narrow and wide jets to 1% scale precision","Small and large radius jets match R=0.4 calibration precision","New method measures jet energy scale for R=0.2 and 0.6","Jet resolution for R=0.2 spans 35% to 6% across pT"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000456,"raw_usage":{"total_tokens":2460,"prompt_tokens":1285,"completion_tokens":1175,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":901,"completion_tokens_details":{"reasoning_tokens":1089}},"tokens_in":901,"tokens_out":1175,"duration_ms":9768,"temperature":1.0,"reasoning_tokens":1089,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T11:16:51.184574+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A decisive check is to derive the same in situ correction in a third topology, such as $\\gamma$+jets, and compare the calibrated $R=0.2$ and $R=0.6$ jet energy scales with the $Z$+jets/dijet result: the paper's own closure tests show agreement within 0.5% to 1%, so a disagreement larger than the combined uncertainties would show that two topologies do not cover the full phase space. A second check is to re-derive the correction using 2017--2018 data and verify whether the claimed Run 2 applicability holds under higher pile-up conditions.","supporting_citations":[],"review_version":1}