{"id":"0131f706-b550-4bbf-86eb-8c2a270e7498","arxiv_id":"2608.06543","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"A Monte Carlo sensitivity study projects that the IceCube Upgrade with DeepCore can detect Earth matter effects at 5.5-7.1 sigma, reject a uniform Earth at 2.4 sigma, and measure the Earth's mass to about 10% precision.","lead":"This paper simulates how well the IceCube Upgrade, a dense new sub-detector at the South Pole, could use multi-GeV atmospheric neutrino oscillations to probe the Earth's interior. It projects that the detector could detect matter-induced oscillation effects at 5.5-7.1 sigma and measure the Earth's mass to about 10% precision, independent of seismic and gravitational methods.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The quoted density and mass precisions are really precisions on rho*Ye, with Ye fixed exactly; a few-percent core composition systematic is comparable to the claimed 7% core density precision.","rationale":"The paper is a transparent sensitivity study, and the fixed-Ye assumption is explicitly stated in Section II. However, the assumption is not merely an external input; it is the conversion between the measured quantity (electron density) and the reported quantity (mass density). Because the headline claims are precision estimates, a systematic of similar size to the claimed precision is a first-order concern. The reader's weakest_assumption identifies exactly this fixed-Ye issue, and I agree that it is the most load-bearing assumption in the chain from oscillation probabilities to Earth density and mass. The IC91-versus-IC93 mismatch is also important and the paper handles it with a Note added, but it is a detector parameter that the authors openly disclose; the Ye assumption, by contrast, can bias the physical interpretation of the results even if the detector were exactly as simulated. The proposed concrete test would quantify whether the Ye systematic is subdominant or dominant. Since the reader already returned CONDITIONAL, and this concern reinforces that verdict by adding a specific condition on composition marginalization, the verdict should remain unchanged.","tokens_in":27265,"tokens_out":9041,"duration_ms":90175,"concrete_test":"Re-run the Section V.D correlated-density fit with two additional nuisance parameters deltaYe_core and deltaYe_mantle, using Gaussian priors of sigma=3% and sigma=1% (or the current geochemical allowed ranges from Refs. [39,46]), and recompute the 1-sigma band on alpha_C in Fig. 11(a) and the 1-sigma alpha band in Fig. 10. If either band widens by more than 30% relative to the quoted precision, or shifts by more than 1-sigma, then the reported constraints are not robust to composition uncertainty and the paper should quote results in terms of rho*Ye or marginalize over Ye.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claims in Sections V.C and V.D are that the Upgrade can measure the Earth's mass to about 10% and correlated layer densities to about 7% for the core. But the observable in Eq. (1) is the matter potential V_CC proportional to rho*Ye, and Section II fixes Ye=0.4656 for the core and Ye=0.4957 for the mantle without propagating any uncertainty. The paper itself notes that neutrino data cannot pin down Ye within its present allowed range, so this is a modeling premise rather than a measured constraint. Because the fit interprets the matter potential entirely as density, a mis-specified Ye directly biases the fitted scale factors: the inferred density scaling is approximately alpha_true times (Ye_true/Ye_assumed), with the core contributing about one third of the Earth's mass. The geochemical uncertainty in core Ye, dominated by the light-element content, is plausibly several percent. That is comparable to the quoted 7% core density precision and non-negligible for the 10% mass precision. In addition, the uniform-vs-layered test of Section V.B mixes density layering with composition layering, since the uniform hypothesis adopts Ye=0.5 while the 12-layer PREM hypothesis adopts different Ye values in core and mantle. Thus the headline 'density' and 'mass' constraints are conditional on an unquantified external composition assumption.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper presents a Monte Carlo sensitivity projection for using atmospheric neutrino oscillations in the IceCube Upgrade to probe the interior of the Earth. The analysis is built on simulated events for the planned IC93 configuration, with an explicit binned likelihood including roughly 26 nuisance parameters, an Asimov dataset, and a non-nested hypothesis-test statistic for binary comparisons. The four main results are: (i) rejection of the vacuum oscillation hypothesis at 5.5 sigma, or 7.1 sigma with a 1% prior on Delta m^2_31, in a combined IC86 (12 yr) + IC93 (3 yr) fit; (ii) rejection of a uniform-density Earth at 2.4 sigma; (iii) a 1-sigma constraint on the Earth's mass scaling factor alpha of about 10%; and (iv) correlated density constraints of about 7% for the core, 10% for the inner mantle, and 23% for the middle mantle. All headline numbers assume normal mass ordering and the planned seven-string IC93 geometry, with a note added acknowledging that the as-built detector is IC91.","tokens_in":27492,"tokens_out":8050,"duration_ms":83243,"significance":"If the quoted sensitivities are correct as stated, they would demonstrate a substantial improvement of the IceCube Upgrade over DeepCore-only analyses for neutrino-based Earth tomography, making neutrino oscillations a competitive complement to seismic and gravitational probes. The manuscript has clear strengths: a full simulation chain based on established DeepCore/Upgrade tools, an explicit and fairly complete list of nuisance parameters with priors, a transparent Asimov-based statistical procedure, and an unusually honest note about the mismatch between the planned IC93 geometry and the as-built IC91 detector. The results are, however, conditional on two external assumptions that receive less attention in the abstract and conclusions than they deserve: the exact composition of the Earth through Y_e, and the IC93 geometry. These caveats do not invalidate the methodology, but they must be propagated into the headline claims before the paper can be read as a sensitivity estimate for the actual IceCube Upgrade.","major_comments":[{"comment":"The observable in Eq. (1) is V_CC proportional to rho times Y_e, but Section II fixes Y_e = 0.4656 for the core and Y_e = 0.4957 for the mantle and propagates no uncertainty in Y_e. The paper itself states that neutrino data are not yet sensitive enough to constrain Y_e within its current allowed range, so this is an external modeling assumption rather than a measured input. Because the fit interprets every change in the matter potential as a change in density, an unmodeled fractional change in Y_e biases the inferred scaling factors alpha and alpha_C by a comparable fractional amount. Geochemical uncertainty in the core's light-element content is plausibly several percent, which is comparable to the claimed ~7% core-density precision and non-negligible for the claimed ~10% mass precision. The abstract and conclusions should either propagate a Y_e systematic into the quoted precisions or reframe the claims as sensitivities to the product rho times Y_e.","section":"Section II / Eq. (1), Sections V.C and V.D"},{"comment":"The uniform-density test hypothesis in Section V.B uses Y_e = 0.5, while the 12-layered PREM hypothesis uses Y_e = 0.4656 in the core and Y_e = 0.4957 in the mantle. The 2.4-sigma rejection therefore does not test density layering alone; it also tests the assumed composition profile. As defined, the test cannot distinguish a uniform-density Earth with a different core composition from a layered-density Earth, so the abstract's claim that the Upgrade can verify the non-homogeneous distribution of matter density is stronger than what is actually demonstrated. The comparison should either adopt a common Y_e profile for both hypotheses or treat Y_e as a nuisance parameter.","section":"Section V.B and Section II"},{"comment":"All quoted sensitivities are computed for the planned IC93 geometry, while the as-built detector is IC91 with six Upgrade strings deployed and five operational. Section I and the Note added state this clearly, and the Note added says the actual sensitivity will be lower, but the abstract and Section V present the IC93 numbers without this qualifier and no IC91 projection is provided. Because the title and abstract refer to 'the IceCube Upgrade' in the present tense, readers will reasonably take 5.5 sigma, 7.1 sigma, and the ~10% mass precision as statements about the detector that now exists. The abstract and conclusions should clearly label the configuration used, and the authors should provide at least an approximate estimate of the IC91 degradation, given that the detector geometry is already known.","section":"Section I, Note added, Abstract"}],"minor_comments":[{"comment":"The text says bins with low event statistics are excluded from the analysis but does not specify the threshold or how the exclusion is applied across PID classes; this should be stated for reproducibility.","section":"Section III / Fig. 3"},{"comment":"The pull term in Eq. (2) is written as a Gaussian penalty, but Table II also lists parameters with uniform priors (e.g., ice absorption, A_eff scale); clarify how uniform-prior parameters enter the minimization, for example as hard bounds with no pull term.","section":"Eq. (2) / Table II"},{"comment":"The phrase 'These estimates are conservative' is not supported by the analysis shown; since no reoptimization was performed for the reduced geometry, the relation of the IC93 results to IC91 sensitivities is unknown rather than conservative, and the wording should be revised.","section":"Note added"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is honest about its caveats, but the abstract and title currently make claims about 'the IceCube Upgrade' without carrying the IC93-configuration and fixed-Y_e qualifications. I would ask the editor to ensure the revised version labels all sensitivity numbers with the configuration and composition assumptions prominently, ideally in the abstract."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"This is the first full-simulation sensitivity projection for the IceCube Upgrade as an Earth-tomography instrument, and it is a competent one. The work is not a measurement and does not pretend to be: it uses an Asimov dataset, a full MC chain, roughly 26 nuisance parameters, and a non-nested hypothesis test statistic, which is the right way to compare vacuum or uniform-density hypotheses against a layered Earth model.\n\nThe paper does itself credit by stating in a note added that the detector was actually deployed with six strings rather than seven, only five of them operational, and that all quoted sensitivities use the planned IC93 geometry. The physics conclusions are plausible: 12 years of DeepCore plus 3 years of Upgrade can reject vacuum at 5.5 sigma (7.1 with a 1% prior on Delta m^2_31), reject a uniform Earth at 2.4 sigma, measure the total mass to about 10%, and constrain the core density to about 7%, while DeepCore alone is much weaker. The figures and appendices are clear.\n\nTwo caveats matter. First, the headline numbers are for IC93; the as-built detector is IC91. The note added is honest, but the abstract and summary still lead with the IC93 numbers. For a sensitivity projection this is acceptable if clearly labeled, and it should be labeled in the abstract and conclusion. Second, the stress-test concern about Ye is on target. The observable in Eq. (1) is the matter potential proportional to rho*Ye, and Section II fixes Ye = 0.4656 for the core (pure FeNi) and 0.4957 for the mantle (pyrolite) without propagating uncertainty. The paper itself says neutrino data cannot pin down Ye within its allowed range. So the quoted \"7% core density precision\" is really a precision on rho*Ye assuming exact composition. A few-percent uncertainty in core light-element content is comparable to the claimed core precision, and the uniform-vs-layered test mixes density layering with composition layering because the uniform hypothesis uses Ye = 0.5. This is not fatal, but it should be quantified or the claims reworded as constraints on rho*Ye.\n\nA smaller point: the low-statistics bin-exclusion rule is not specified. A referee should ask for that to be documented. The citation pattern is fine; the collaboration cites its own DeepCore and preliminary studies, which is appropriate here.\n\nWho is this for? Neutrino physicists planning Upgrade analyses and geoscientists interested in independent probes of Earth structure. It deserves serious peer review. My recommendation: send it to a competent referee, ask for clear labeling or rebaselining to IC91, a quantitative discussion of Ye systematics, and documentation of the bin-exclusion rule. The core analysis is sound.","headline":"A competent, transparent sensitivity projection showing the IceCube Upgrade roughly doubles DeepCore-only reach to Earth matter effects, but the headline numbers assume the unbuilt IC93 geometry and the quoted density/mass precisions are really precisions on rho*Ye with composition fixed.","tokens_in":30510,"tokens_out":3018,"would_cite":true,"duration_ms":29716,"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 projects that adding three years of IceCube Upgrade data to twelve years of DeepCore data would let atmospheric neutrino oscillations reject the vacuum-oscillation hypothesis at 5.5σ, measure Earth's mass to about 10%, and…","keywords":["neutrino oscillations","Earth tomography","atmospheric neutrinos","IceCube Upgrade","matter effects","PREM","Earth mass measurement"],"falsifier":"Re-run the same Asimov fits with the core $Y_e$ set to 0.50 instead of 0.4656 while keeping the densities fixed; if the recovered Earth-mass scaling $\\alpha$ shifts by more than the quoted $1\\sigma$ precision, then the Upgrade is measuring the product $\\rho\\,Y_e$ as a whole, not density alone, and the paper's composition assumption is not innocuous.","tokens_in":27019,"feed_emoji":"🌍","tokens_out":9293,"duration_ms":76758,"temperature":0.7,"pith_summary":"This paper projects what the IceCube Upgrade, a densely instrumented central array added to the IceCube neutrino detector, could learn about the Earth's interior from oscillations of multi-GeV atmospheric neutrinos. Using simulated data equivalent to 12 years of IceCube DeepCore plus 3 years of the Upgrade (the IC93 configuration), it predicts that matter effects in neutrino propagation would be established at $5.5\\sigma$ by rejecting the vacuum-oscillation hypothesis, rising to $7.1\\sigma$ with a 1% external prior on $\\Delta m^2_{31}$. The same simulated data set would reject a uniform-density Earth at $2.4\\sigma$, measure the Earth's total mass to about 10% at the $1\\sigma$ level, and constrain the correlated densities of the core, inner mantle, and middle mantle to roughly 7%, 10%, and 23%. These numbers assume normal neutrino mass ordering and the originally planned IC93 geometry; the as-built IC91 detector is expected to be somewhat less sensitive. The case for caring: neutrino tomography would be an independent, complementary check on seismic and gravitational models of the deep Earth.","feed_headline":"Upgraded IceCube could weigh Earth to 10 percent precision","feed_subtitle":"Twelve years of DeepCore plus three of the Upgrade would reject a uniform Earth at 2.4 sigma and pin core density to about 7 percent.","key_machinery":"The central object is the matter potential of Eq. (1), $V_{CC} \\approx \\pm 7.6\\times 10^{-14}\\,Y_e\\,(\\rho/\\mathrm{g\\,cm^{-3}})\\,\\mathrm{eV}$, which modifies the $\\nu_\\mu \\to \\nu_e$ and $\\nu_\\mu \\to \\nu_\\mu$ oscillation probabilities as neutrinos cross the Earth. The analysis leans on two resonance features: the MSW resonance near 6--10 GeV for mantle-passing neutrinos, and the parametric (oscillation-length) resonance near 3--6 GeV for neutrinos that cross the core. The Earth is represented by a 12-layered volume-averaged PREM profile, with $Y_e = 0.4656$ for the core and $Y_e = 0.4957$ for the mantle, for the vacuum-rejection, uniform-rejection, and mass-measurement fits, and by a 5-layered version (inner core, outer core, inner mantle, middle mantle, outer mantle) for the correlated-density fit, with total mass and moment of inertia held fixed. Sensitivities are evaluated with a modified $\\chi^2$ statistic on Asimov datasets, using a non-nested hypothesis formula for discrete comparisons and Wilks' theorem for nested scans over the scaling factors.","core_discovery":"The paper's central claim is that the IceCube Upgrade turns atmospheric neutrino oscillations into a practical probe of the Earth's radial density profile. Because the matter potential $V_{CC} = \\pm\\sqrt{2}G_F N_e$ depends on the product of density $\\rho$ and the electron-to-nucleon ratio $Y_e$, neutrinos crossing the mantle and core acquire oscillation signatures in specific energy and zenith ranges: the MSW resonance near 6--10 GeV for mantle trajectories and the parametric (oscillation-length) resonance near 3--6 GeV for core-crossing trajectories. Fitting a 12-layered volume-averaged PREM profile against the vacuum hypothesis and against a uniform-density Earth, the paper estimates median sensitivities of $5.5\\sigma$ and $2.4\\sigma$, respectively, for the combined IC86 (12 yr) + IC93 (3 yr) sample under normal ordering. It further claims that scaling the 12-layered profile by a single factor $\\alpha$ lets the data measure the Earth's mass to about 10% at the $1\\sigma$ level, and that a 5-layered profile with fixed total mass and moment of inertia constrains correlated layer densities to about 7% (core), 10% (inner mantle), and 23% (middle mantle). All of these results are Asimov (no-fluctuation) median sensitivities from Monte Carlo templates, not yet real data.","pith_inferences":["A future external measurement of $\\Delta m^2_{31}$ at sub-percent precision should push the vacuum-rejection significance above the $7.1\\sigma$ shown here, because the paper identifies the $\\Delta m^2_{31}$--matter-effect degeneracy as the main systematic.","Because the as-built IC91 detector has one fewer working string than IC93, three years of real data will likely land below these projections; the paper's note that degradation is roughly uniform suggests scaling live-time upward as a rough correction.","If the Earth-mass measurement matures, the same $\\alpha$ scaling could be reinterpreted as a joint constraint on density and composition, giving a neutrino-based check on mineral-physics models of the core.","The technique's sensitivity to the density jump at the core-mantle boundary could motivate combining these data with other large-volume neutrino detectors to sharpen the location and size of the discontinuity."],"forward_implications":["The IceCube Upgrade roughly doubles to triples the expected significance for establishing matter effects compared to DeepCore alone: $5.5\\sigma$ versus $1.9\\sigma$ at $\\theta_{23}=47.5^\\circ$ under normal ordering.","A 1% external prior on $\\Delta m^2_{31}$ improves the vacuum-rejection significance by about 30%, to $7.1\\sigma$.","The combined sample can reject a homogeneous Earth at $2.4\\sigma$, providing an independent test of radial layering.","A neutrino-based estimate of the Earth's mass to about 10% would be a new, independent weak-interaction measurement, complementing gravitational determinations.","Correlated layer-density constraints (core $\\sim7\\%$, inner mantle $\\sim10\\%$, middle mantle $\\sim23\\%$) narrow the density ranges allowed by mass and moment-of-inertia constraints alone."],"supporting_citations":[{"why":"Defines the Preliminary Reference Earth Model whose 12-layered volume-averaged profile is the true hypothesis for the matter-effect and mass fits.","marker":"[22]"},{"why":"Supplies the Y_e values (0.4656 core, 0.4957 mantle) that let the matter potential be read as a density, along with the spectrometry idea.","marker":"[39]"},{"why":"Provides the DeepCore data sample, best-fit theta_23 and Delta m^2_31, and the oscillation parameter values used as nominal inputs.","marker":"[58]"},{"why":"Supplies the IceCube Upgrade simulation chain, event selection, and the IC93 detector configuration used for projections.","marker":"[70]"},{"why":"Provides the global-fit neutrino oscillation parameters and motivates the 1% Gaussian prior on Delta m^2_31.","marker":"[77]"},{"why":"Gives the Honda atmospheric neutrino flux model used to weight Monte Carlo events into expected counts.","marker":"[94]"},{"why":"Provides the series expansions showing the linear dependence of the relevant probabilities on sin^2 theta_23, used to interpret the sensitivity curves.","marker":"[100]"},{"why":"Gives the formula for converting chi-square differences into Gaussian significance in non-nested hypothesis tests.","marker":"[102]"}],"fun_headline_variants":["IceCube Upgrade to weigh Earth to 10% precision","Neutrino probe weighs Earth's core via IceCube","IceCube Upgrade: weighing Earth with neutrinos","Upgraded IceCube measures Earth's mass to 10%","IceCube Upgrade probes Earth's density with neutrinos"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the Earth's chemical composition, quantified by the electron-to-nucleon ratio $Y_e$, is known exactly (FeNi core with $Y_e = 0.4656$, pyrolite mantle with $Y_e = 0.4957$), so every measured matter effect can be attributed to density rather than composition; if the true core or mantle composition differs, the inferred densities, Earth mass, and layer-density constraints would shift.","fun_headline_variants_meta":{"raw":{"variants":["IceCube Upgrade to weigh Earth to 10% precision","Neutrino probe weighs Earth's core via IceCube","IceCube Upgrade: weighing Earth with neutrinos","Upgraded IceCube measures Earth's mass to 10%","IceCube Upgrade probes Earth's density with neutrinos"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000524,"raw_usage":{"total_tokens":2565,"prompt_tokens":1013,"completion_tokens":1552,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":629,"completion_tokens_details":{"reasoning_tokens":1472}},"tokens_in":629,"tokens_out":1552,"duration_ms":11331,"temperature":1.0,"reasoning_tokens":1472,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T04:17:19.015010+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Re-run the same Asimov fits with the core $Y_e$ set to 0.50 instead of 0.4656 while keeping the densities fixed; if the recovered Earth-mass scaling $\\alpha$ shifts by more than the quoted $1\\sigma$ precision, then the Upgrade is measuring the product $\\rho\\,Y_e$ as a whole, not density alone, and the paper's composition assumption is not innocuous.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the Y_e values (0.4656 core, 0.4957 mantle) that let the matter potential be read as a density, along with the spectrometry idea."},{"cited_title":"Constraining the core radius and density jumps inside Earth using atmospheric neutrino oscillations","cited_arxiv_id":"2405.04986","evidence_quote":"Provides the DeepCore data sample, best-fit theta_23 and Delta m^2_31, and the oscillation parameter values used as nominal inputs."},{"cited_title":"Abbasiet al.(IceCube), D-Egg: a dual PMT op- tical module for IceCube, JINST18(04), P04014, arXiv:2212.14526 [astro-ph.IM]","cited_arxiv_id":null,"evidence_quote":"Supplies the IceCube Upgrade simulation chain, event selection, and the IC93 detector configuration used for projections."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the Honda atmospheric neutrino flux model used to weight Monte Carlo events into expected counts."}],"review_version":1}