{"id":"6d0ace23-a954-4834-b5e4-954fb35c10ac","arxiv_id":"2505.02436","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Extending AMPT with medium-induced gluon radiation gives a unified kinetic description of jet suppression and the full jet-shape ratio, matching CMS data out to radius 1 when both elastic and radiative losses act.","lead":"This paper adds in-medium gluon radiation to the AMPT transport model so that jets and the quark-gluon plasma share energy through collisions and radiation, then tests the model against CMS jet suppression and jet-shape data in lead-lead collisions at 5.02 TeV. It reports that radiative plus collisional energy loss together reproduce the measured jet-shape ratio far from the jet axis, while radiation-free models over-populate the large-angle region.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The radiative-cascade conclusion is regulated by pT,cut=2 GeV, which is never varied; a sensitivity test is needed before the central claim can be trusted.","rationale":"The reader's weakest-assumption analysis already identifies pT,cut = 2 GeV as the unvaried regulator of the radiative cascade, and my reading agrees. The strongest claim—that radiative degradation is essential to the jet-shape ratio across the full radial range—is directly tied to this threshold. Without a sensitivity scan, the reader cannot tell whether the agreement in Fig. 5 is a robust consequence of radiative energy loss or a consequence of choosing pT,cut = 2 GeV. The paper does include useful independent support: the p-p baseline matches CMS data, the bulk parameters are calibrated to bulk observables, and the qualitative distinction between collisional-only and collisional-plus-radiative cases is physically plausible. However, those supports do not remove the need to test the one parameter that gates the radiative cascade. The concern does not justify rejection or a stronger verdict than CONDITIONAL; it reinforces the need for a sensitivity study before acceptance as a definitive statement about the role of gluon emissions. The recommended verdict therefore remains CONDITIONAL, consistent with the reader's verdict.","tokens_in":13050,"tokens_out":1786,"duration_ms":24312,"concrete_test":"Repeat the string-melting AMPT calculation of Fig. 5 with pT,cut = 1.0, 1.5, 2.5, and 3.0 GeV, keeping all other settings (sigma_el = 1.5 mb, same statistics, same cuts) fixed. If the jet-shape ratio rho_PbPb/rho_pp changes by more than the quoted statistical or experimental uncertainty, especially for Delta r > 0.4, then the conclusion that radiative energy degradation is essential is threshold-dependent and must be qualified. If the ratio remains within uncertainties across pT,cut in 1–3 GeV, the concern is resolved.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim—that gradual degradation of jet energy through gluon emissions is essential to describe the full jet-shape ratio—depends on the threshold pT,cut = 2 GeV that separates jet-shower partons from bulk-medium partons (Sec. II, after Eq. (3)). Radiated gluons with pT > pT,cut can emit further gluons and thus participate in the radiative cascade; those below only scatter elastically. This threshold therefore controls both the number of cascade generations and the population of semi-hard partons that undergo elastic diffusion to large angles, which is precisely the region where the model's agreement with CMS data is claimed. No sensitivity study is presented: Fig. 5 varies the elastic cross section (1.5 vs 5 mb), but pT,cut is fixed. The paper also does not show how pT,cut relates to the zmin = mu/E cutoff in Eq. (3), the hadron track cut pT > 0.7 GeV, or the jet reconstruction threshold. Because the radiative channel is the distinguishing ingredient in the transport framework, an unexamined threshold that directly regulates that channel leaves the central conclusion conditional. This is not a circularity or data-exclusion concern; it is an internal sensitivity gap in a parameter-free-looking but actually hand-chosen parameter.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript extends the AMPT parton transport model to include, in addition to elastic scatterings, medium-induced gluon radiation for jet shower partons, using the higher-twist spectrum of Eq. (3) with qhat computed from the same elastic cross section that governs the collisional channel. The model is applied to (0-10)% central Pb-Pb collisions at 5.02 TeV, and predictions are presented for the time dependence of single-gluon energy loss (Fig. 1), jet pT loss as a function of cone size (Fig. 2), inclusive jet R_AA (Fig. 3), the jet shape rho(Delta r) (Fig. 4), and the jet-shape ratio rho_PbPb/rho_pp (Fig. 5). The central claim is that gradual degradation of jet energy through repeated gluon emissions is essential to describe the full range of the measured jet-shape ratio, whereas a pure collisional calculation injects too much pT broadening and overpopulates large angular distances. The model achieves reasonable quantitative agreement with the CMS jet-shape data up to Delta r = 1, while the inclusive jet R_AA is somewhat under-quenched at low pT and for the larger cone radius.","tokens_in":13231,"tokens_out":3917,"duration_ms":46412,"significance":"If the central claim holds, the paper provides a genuinely unified kinetic framework for jet and bulk evolution, with the notable strength that alpha_s and the Debye mass are fixed by prior AMPT bulk calibration to multiplicity and flow, and qhat is not tuned to jet data but derived from the elastic cross section. The controlled switch between collisional-only and collisional-plus-radiative channels in Fig. 5 is a valuable diagnostic, and the decomposition of the jet shape into fragmentation, semi-hard radiated gluons, and medium-excitation contributions in Fig. 4 is informative. The model also makes falsifiable predictions for the pT and cone-size dependence of jet suppression. However, the central conclusion rests on the unexamined threshold pT,cut = 2 GeV that regulates the radiative cascade, so the significance can only be fully realized after a sensitivity analysis is provided.","major_comments":[{"comment":"The threshold pT,cut = 2 GeV determines whether a radiated gluon can undergo further inelastic splittings, and therefore controls both the number of cascade generations and the population of semi-hard partons that subsequently diffuse elastically to large angles. The central claim that gradual radiative degradation is essential to describe the jet-shape ratio (abstract and Sec. III, Fig. 5) is thus regulated by a parameter for which no sensitivity study is presented. I request a scan of pT,cut (for example 1, 3, and 4 GeV, or values tied to mu or to the jet radius R) with the jet-shape ratio and R_AA shown, together with a statement of how pT,cut relates to the zmin = mu/E_j cutoff in Eq. (3) and to the hadron track cut pT > 0.7 GeV.","section":"Sec. II, after Eq. (3)"},{"comment":"The comparison between the pure-collisional (dashed blue) and collisional-plus-radiative (solid red) curves is the primary evidence for the central claim. Because the radiative channel is switched on together with the pT,cut criterion, the difference between the two curves could be influenced by pT,cut as much as by the presence of radiation itself. At minimum, one additional radiative run with a different pT,cut is needed to separate these effects; without it, the statement that gluon emissions are 'essential' remains conditional on the threshold choice.","section":"Sec. III, Fig. 5"},{"comment":"The model visibly underpredicts the measured jet suppression, with the largest deviations for pjet_T < 150 GeV and for the larger cone radius R = 0.4, in line with the authors' own acknowledgment in the text. Since the abstract and Sec. III claim 'reasonable quantitative agreement' with inclusive jet suppression, the disagreement should be quantified (for instance as a chi-square per degree of freedom or an average relative deviation) and its implications for the jet-shape analysis discussed, particularly whether the missing suppression points to high-virtuality energy loss that could also affect the small-Delta r region of the jet-shape ratio.","section":"Sec. III, Fig. 3"}],"minor_comments":[{"comment":"There is a spacing typo in the affiliation: 'Ind ia' should read 'India'.","section":"Author affiliation"},{"comment":"The notation for the jet nuclear modification factor appears in several forms (Rjet_AA, R^jet_AA, RAA^jet); please use a single consistently typeset symbol.","section":"Throughout"},{"comment":"The dashed curves are labeled 'w/o medium' but the caption should specify that this means without jet-induced medium response, not without the underlying medium itself, to avoid confusion with the collisional-only case in Fig. 3.","section":"Fig. 2 caption"},{"comment":"The text should clarify that Eq. (10) sums charged tracks with pT > 0.7 GeV while the R_AA calculation in Eq. (8) includes all hadrons; the current wording 'all the hadrons' in Fig. 2 is ambiguous.","section":"Eq. (10) and Fig. 4"},{"comment":"Reference [43] has an incomplete page number '01491'; it should be '014910' or the full article number as published.","section":"References"},{"comment":"In the concluding paragraph, 'the significant differences' and 'their significance' are used in close proximity with slightly different meanings; rewording would improve readability.","section":"Sec. IV"}],"recommendation":"major_revision","confidential_remarks":"The paper is a solid and useful contribution to transport-based jet quenching, and I found no evidence of circularity in the parameter choice: alpha_s and mu are fixed by bulk calibration and qhat is derived from the same elastic cross section rather than fitted to jet data. The main obstacle is the absence of a sensitivity study for pT,cut, which directly regulates the radiative cascade on which the central claim rests. If the authors can provide that scan and quantify the R_AA under-quenching, I would support acceptance; in its current form the central claim remains conditional."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"First, the short version: this is a genuine step forward for AMPT-based jet quenching, not a breakthrough, and the central claim is plausible but not fully nailed down because a hand-chosen threshold controls the radiative cascade and is never varied.\n\nWhat's actually new: the authors take the string-melting AMPT transport model, which so far only treated jets with elastic two-body scatterings, and add medium-induced gluon radiation from the higher-twist formalism (Eq. 3). The qhat is computed from the same elastic cross section, not fitted to jet data; alpha_s and mu come from bulk calibration to multiplicity and flow. So the jet observables—R_AA and the jet shape ratio—are genuine predictions. That deserves credit. The comparison to CMS data up to Delta r = 1 is also meaningful: the model gets the qualitative shape, and the collisional-only control shows a clear dip-and-excess structure that does not look like data. That makes the point about gradual energy loss via gluon radiation being important.\n\nNow the soft spots. The stress-test concern is on target: pT,cut = 2 GeV decides which radiated gluons can emit further gluons and which just scatter elastically as bulk. That threshold directly regulates the radiative cascade—which is exactly their new physics—and they never vary it. They vary the elastic cross section (1.5 vs 5 mb), but that's not the same knob. If the conclusion is robust, they should show it for pT,cut = 1.5 and 3 GeV. Without that, the central claim is conditional. It's a missing test, not a contradiction.\n\nThe R_AA comparison is a second soft spot: under-quenching at low pT and an opposite cone-radius dependence relative to data. The authors acknowledge this and attribute it to needing more energy loss at high virtuality, but it does weaken the overall impression. The model has the right ingredients but not the right size of that effect.\n\nMinor: no code, parameter files, or event counts are shipped. For a Monte Carlo paper that is not a dealbreaker, but it limits independent reproduction.\n\nWho this is for: jet-quenching modelers, especially AMPT users, will get the most out of it. It deserves a serious referee. I'd engage with it, but the referee should ask for the pT,cut scan before accepting the interpretation.","headline":"First radiative+elastic jet transport in string-melting AMPT with a clean physics claim and honest caveats—just missing a pT,cut sensitivity scan before I'd buy the central conclusion.","tokens_in":13808,"tokens_out":3892,"would_cite":true,"duration_ms":44027,"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":"A unified transport model with elastic scattering plus medium-induced gluon emission reproduces the measured suppression and full radial jet-shape ratio in central Pb-Pb collisions at 5.02 TeV.","keywords":["jet quenching","jet shape","quark-gluon plasma","medium-induced gluon radiation","collisional energy loss","parton transport","heavy-ion collisions","jet nuclear modification factor"],"falsifier":"Repeat the same simulation with the transverse-momentum threshold varied from about 1 to 3 GeV and check whether the jet-shape ratio at radial distances greater than 0.5 changes by more than the experimental uncertainty; if it does, the claim that gradual gluon degradation is essential to the full profile is not robust.","tokens_in":12774,"feed_emoji":"⚛️","tokens_out":6926,"duration_ms":80749,"temperature":0.7,"pith_summary":"The paper presents a unified kinetic-transport calculation in which a jet and the quark-gluon plasma medium are evolved together, sharing energy and momentum through both elastic scatterings and medium-induced gluon emission. Its central claim is that this combined treatment reproduces the measured inclusive jet suppression and the full jet-shape ratio, from the jet core out to large radial distances, in central lead-lead collisions at 5.02 TeV. The key quantitative finding is that gradual degradation of jet energy through gluon emissions is essential to describe the entire jet-shape ratio, whereas pure collisional energy loss over-populates the large-angle region. The result matters because it provides a complete kinetic framework for jet-medium interaction that can be used to interpret differential jet-substructure observables and to probe the medium's response to a propagating jet.","feed_headline":"Gluon emission shapes jets from core to edge in Pb-Pb","feed_subtitle":"A unified transport calculation reproduces suppression and full jet-shape data out to radial distance 1.","key_machinery":"The engine is the AMPT multiphase transport model with string melting, extended for jet quenching by allowing hard jet shower partons to undergo medium-induced inelastic splittings alongside the existing elastic parton cascade. Jets are embedded as full PYTHIA-generated parton showers, and jet-medium interactions are described by a Debye-screened elastic cross section plus a higher-twist gluon radiation spectrum whose sampling follows the LBT methodology. The inelastic rate is tied to the elastic broadening through the jet transport coefficient q-hat, and emitted gluons only re-interact after a formation time and if their transverse momentum exceeds 2 GeV; bulk medium partons scatter only elastically. This machinery allows the lost energy and momentum to flow from the jet into the medium through discrete scatterings, producing the medium response that dominates the jet shape at large radial distances.","core_discovery":"The paper claims that a single kinetic-transport framework, in which a full jet shower and the quark-gluon plasma are evolved together and exchange energy and momentum through both elastic scatterings and medium-induced gluon radiation, describes the measured jet observables in central Pb-Pb collisions at 5.02 TeV. Concretely, the jet nuclear modification factor is reproduced within statistical uncertainties for cone radii R=0.2 and 0.4, and the jet-shape ratio matches experimental data from the core out to radial distance one. The authors find that pure collisional energy loss produces too much particle population at large radial distances, while gradual energy degradation via gluon emission makes the jet narrower and is essential to describe the entire range of the ratio. The result is presented as the first unified kinetic-based treatment of jet and medium evolution with a dynamically evolving partonic background, as opposed to models that assume instantaneous thermalization of the lost energy.","pith_inferences":["Editorial: the 2 GeV transverse-momentum threshold that separates radiative jet partons from elastically scattering bulk partons is the least constrained parameter in the model; a systematic scan of this threshold would map the radiative-versus-elastic competition and should be reported before applying the framework to fine jet substructure.","Editorial: because the lost energy is not instantaneously thermalized in this approach, the jet-shape ratio's large-angle tail is probably sensitive to the medium's relaxation time; comparisons with calculations that assume instantaneous thermalization would isolate this memory effect.","Editorial: the same framework could naturally be extended to jet-substructure observables such as girth or angularities, where the radiative and elastic contributions enter in different combinations and would provide sharper tests of the mechanism identified here."],"forward_implications":["If the central claim holds, jet-shape measurements at large radial distance directly probe the partition of lost jet energy into radiative versus collisional channels, not just total suppression.","The model's under-quenching of low-pT jets for larger cone radius implies more energy loss is needed at the high-virtuality stage, motivating the addition of a detailed in-medium high-virtuality evolution to the same framework.","The strong sensitivity of the jet-shape ratio to the medium's parton density means the observable can discriminate between different bulk-medium evolution scenarios.","Pure collisional transport predicts a characteristic dip-and-rise jet-shape ratio, so a precise measurement in the intermediate radial region can flag whether a model is missing the radiative channel.","The framework sets the stage for exploring different radiative energy-loss formalisms within a kinetically consistent medium, rather than assuming instantaneous thermalization."],"supporting_citations":[{"why":"provides the measured jet-shape ratio in central Pb-Pb and pp collisions that the model's central comparison targets.","marker":"[5]"},{"why":"supplies the Debye-screened elastic scattering cross section used for collisional energy loss in the cascade.","marker":"[17]"},{"why":"supplies the methodology for sampling medium-induced gluon radiation and enforcing energy-momentum conservation in 2 to 2 plus N_g processes.","marker":"[24, 25]"},{"why":"provides the multiphase transport (AMPT) framework, including string melting and parton cascade, that is extended here to radiative losses.","marker":"[38]"},{"why":"provides the HIJING 2.0 initial conditions whose realistic minijet production is shown to change the jet-shape ratio.","marker":"[43]"},{"why":"generates the embedded full-jet parton showers with initial-state radiation and multi-parton interactions.","marker":"[45]"},{"why":"supplies the higher-twist medium-induced gluon radiation spectrum used for inelastic collisions.","marker":"[48]"},{"why":"provides the higher-twist energy-loss formulation on which the radiation formula is based.","marker":"[49]"}],"fun_headline_variants":["Unified transport nails jet shapes in Pb-Pb","Gluon emission key to jet shape in Pb-Pb","Collisions alone fail: gluon emission shapes jets","Transport model matches jet shapes to large radius"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The calculation rests on a fixed 2 GeV transverse-momentum threshold that separates partons allowed to radiate gluons from bulk medium partons that only scatter elastically, and the paper does not test whether changing that threshold changes the conclusions.","fun_headline_variants_meta":{"raw":{"variants":["Unified transport nails jet shapes in Pb-Pb","Gluon emission key to jet shape in Pb-Pb","Collisions alone fail: gluon emission shapes jets","Transport model matches jet shapes to large radius"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000556,"raw_usage":{"total_tokens":2646,"prompt_tokens":943,"completion_tokens":1703,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":559,"completion_tokens_details":{"reasoning_tokens":1640}},"tokens_in":559,"tokens_out":1703,"duration_ms":11756,"temperature":1.0,"reasoning_tokens":1640,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-16T00:51:52.519518+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Repeat the same simulation with the transverse-momentum threshold varied from about 1 to 3 GeV and check whether the jet-shape ratio at radial distances greater than 0.5 changes by more than the experimental uncertainty; if it does, the claim that gradual gluon degradation is essential to the full profile is not robust.","supporting_citations":[{"cited_title":"5 mb and collisional plus radiative energy loss for σ el gg = 1","cited_arxiv_id":null,"evidence_quote":"provides the measured jet-shape ratio in central Pb-Pb and pp collisions that the model's central comparison targets."},{"cited_title":"Cunqueiro and A","cited_arxiv_id":null,"evidence_quote":"supplies the Debye-screened elastic scattering cross section used for collisional energy loss in the cascade."},{"cited_title":"Casalderrey-Solana, D","cited_arxiv_id":null,"evidence_quote":"provides the multiphase transport (AMPT) framework, including string melting and parton cascade, that is extended here to radiative losses."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"provides the HIJING 2.0 initial conditions whose realistic minijet production is shown to change the jet-shape ratio."},{"cited_title":"Acharya et al","cited_arxiv_id":null,"evidence_quote":"generates the embedded full-jet parton showers with initial-state radiation and multi-parton interactions."},{"cited_title":"Sj¨ ostrand, S","cited_arxiv_id":null,"evidence_quote":"supplies the higher-twist medium-induced gluon radiation spectrum used for inelastic collisions."},{"cited_title":"Zhang, Y","cited_arxiv_id":null,"evidence_quote":"provides the higher-twist energy-loss formulation on which the radiation formula is based."}],"review_version":1}