{"id":"80d5daed-a133-4edd-abf8-611b32a3b742","arxiv_id":"2504.21839","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"A re-analysis of slow antiproton stopping in LiF says the PRL134 results deviate from experiment by up to a factor of three and proposes the Adiabatic Ionization Model instead.","lead":"This comment argues that a recent Physical Review Letters calculation of slow antiproton stopping in LiF is inaccurate, deviating from experiment by up to a factor of three at low velocities. It lays out the authors' Adiabatic Ionization Model and new statistical tests that question the PRL's simulation method.","discovery_kind":"replication","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The factor-of-3 disagreement with experiment rests on an unpublished 1.13 rescaling of the Møller data; until that scaling is independently verified, the central numerical claim is not fully supported.","rationale":"The reader's weakest_assumption focused on the uncertain inference that PRL134 used a single incommensurate trajectory and on the simplified AIM collision model. That is a real uncertainty, and the comment itself flags it in the sentence 'one cannot be sure'. However, the more load-bearing condition for the paper's central numerical claim is the experimental scaling: the factor-of-3 deviation is computed against Møller data rescaled by 1.13 using details deferred to an unpublished manuscript. This was noted in the reader's rationale but was not chosen as the weakest assumption. I therefore partially agree with the reader. The comment has independent value: the AIM derivation is transparent, the comparison with PRL128 is a useful cross-check, and the trajectory-sampling histograms are a legitimate methodological warning. But the strongest quantitative statement rests on an unavailable scaling reference. The appropriate verdict remains CONDITIONAL: the comment should be accepted only if the scaling is supplied and the trajectory-count inference is either confirmed or softened. My recommendation is UNCHANGED because the reader already reached CONDITIONAL and my concern reinforces that verdict rather than moving it.","tokens_in":8003,"tokens_out":2615,"duration_ms":28230,"concrete_test":"Recompute the 1.13 scaling factor. Locate the proton stopping data in Møller et al. (PRL93 042502, 2004) and compare them velocity-by-velocity with the 'most precise recent proton measurements' referenced in [14]. If the ratio is not 1.13, or varies significantly with velocity, redo the comparison in Fig. 3 using the unscaled and the correctly scaled antiproton data. If the PRL134 curve still deviates by roughly a factor of 3 at low velocities, the claim survives; if the deviation shrinks substantially, the comment's headline result must be revised.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The comment's most striking quantitative claim is that PRL134's stopping curve deviates from existing experimental data by up to a factor of 3 at low speeds. That claim is anchored in Fig. 3, where the Møller et al. antiproton data are multiplied by 1.13 to align the same experiment's proton data with more precise recent proton measurements. The justification for this rescaling is deferred to reference [14], described in the text as 'publication in preparation, 2025'. This is not an available, checkable source; it is a private communication of the authors. If the 1.13 factor is wrong, or if it is not velocity-independent, the magnitude and even the shape of the claimed discrepancy changes. The comment itself acknowledges the uncertainty about PRL134's trajectory sampling ('one cannot be sure, but PRL134 seems to employ just a single trajectory'), but the factor-of-3 statement is presented as a quantitative fact. Because the entire low-velocity comparison depends on this unpublished rescaling, the strongest claim is not yet independently verifiable.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This manuscript is a Comment on arXiv:2501.14381 / Phys. Rev. Lett. 134, 076401 (2025), which reported anomalies in the electronic stopping of slow antiprotons in LiF. The authors present calculations with their Adiabatic Ionization Model (AIM), compare them with CERN experimental data and with earlier rt-TDDFT results, and argue that the PRL134 results deviate from experiment by up to a factor of 3 at low velocities. They further argue that the PRL134 anomalies likely arise from the use of a single incommensurate trajectory (yielding large statistical errors) and from the use of a local Coulomb pseudopotential, and they criticize statements in PRL134 about antiproton capture, the Horsfield model, and resonance effects.","tokens_in":8291,"tokens_out":4937,"duration_ms":44571,"significance":"If the quantitative claims are correct, the comment would show that a published PRL contains serious artifacts and would support AIM as a better low-velocity description. The finite-length trajectory statistics presented in Figs. 4 and 5 are a useful illustration of potential sampling errors. However, the strongest numerical claim (factor of 3) depends on an unpublished data rescaling, and the trajectory-count inference is uncertain; therefore the overall significance depends on further documentation.","major_comments":[{"comment":"The central claim that PRL134 deviates from experiment by up to a factor of 3 is based on multiplying the Møller et al. data by 1.13, and the sole justification is reference [14], described as \"publication in preparation, 2025.\" This is not an available, checkable source; the 1.13 scaling factor, including its velocity dependence and uncertainty, must be documented in the present comment for the factor-of-3 statement to be fully supported.","section":"Energy Loss Comparison for Antiprotons at low velocities, Fig. 3"},{"comment":"The quoted errors (43% mean for the golden-ratio direction, up to −100%/+47% for individual trajectories) are derived from a simplified AIM step-function model with b_c = 2 a.u. The authors acknowledge that \"one cannot be sure\" whether PRL134 used a single trajectory; if more than one trajectory was used, or if the real energy-loss statistics differ from this step function, these numbers do not transfer to PRL134. This section should be rewritten as an illustrative uncertainty analysis with explicit conditional language, not as a definitive error estimate for PRL134.","section":"On the importance and accuracy of incommensurate trajectories, Figs. 4 and 5"},{"comment":"The AIM curve in Fig. 3 depends on three estimated parameters: ΔE_trans = 14.5 eV, P_cont ≈ 58%, and b_c obtained from the crossing in Fig. 2. The paper does not give a sensitivity analysis for these choices, and the same b_c = 2 a.u. is later used for the statistical-error estimate, making part of the critique self-referential. The authors should state whether any AIM parameters are adjusted to reproduce the LiF antiproton data and should show the effect of varying them.","section":"Collisional Broadening and Antiproton Energy Losses, Eq. (2)"},{"comment":"The statements that the pseudopotential is \"exactly ... responsible for the missing stopping-power contributions of 20% ... and partly for the 200%\" and that the supercell \"might not represent an undisturbed solid\" are speculative hypotheses without supporting calculations. To be load-bearing, these points need to be either demonstrated with test calculations or explicitly labeled as conjectures that require further investigation.","section":"On the methodology of the PRL134 quantum calculations"}],"minor_comments":[{"comment":"The PRL134 curve is referred to as \"dashed olive curve\" and later as \"green dashed curve,\" while the caption uses \"green\"; please make the color labels consistent.","section":"After Fig. 3"},{"comment":"Typo: \"resonably\" should be \"reasonably\".","section":"Discussion of AIM agreement"},{"comment":"The approximation `≈ E_gap − 1/(R^2 + r_mean^2)^0.5` would benefit from a note that it is a spherically-averaged estimate; as written, the equality of the matrix element with this closed form is not obvious.","section":"Eq. (1)"},{"comment":"Reference [14] is a \"publication in preparation\"; regardless of the major concern, the manuscript should provide a preprint or an appendix with the scaling details.","section":"References"},{"comment":"The abstract claims \"pointing to severe problems,\" while the body sometimes uses \"might be\"; the abstract could be more calibrated.","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":"The comment is appropriate for a comment venue, but the reliance on an unpublished companion paper is a significant concern. Given that the manuscript is a comment on a PRL, the standards of evidence should be particularly high. If the 1.13 scaling is not independently checkable, the editor might consider asking for a revised version with the scaling details included."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Greg,\n\nShort version: this comment is worth reading if you work on stopping power or TDDFT trajectory sampling, but it is not the final word. The central comparison with experiment is suggestive, not conclusive.\n\nWhat the paper does well: the histogram analysis of incommensurate trajectories (Figs. 4 and 5) is genuinely new and a useful warning. Showing that a single trajectory along a golden-ratio direction can have a 43% mean error, with a distribution ranging from -100% to +47%, is a concrete methodological point. The AIM-LiF stopping curve provides a simple benchmark that agrees reasonably with the CERN data and the PRL128 rt-TDDFT results at low velocities, and the authors make a fair case that PRL134's pseudopotential and supercell treatment could suppress real stopping contributions. The critique of the \"Horsfield model\" and the capture statements also raises legitimate questions.\n\nWhere it gets soft: the factor-of-3 deviation from experiment is anchored in a 1.13 scaling of the Møller et al. data, justified only by a reference to an unpublished paper [14]. That scaling may be right, but it is not checkable, and if it is velocity-dependent the shape of the discrepancy changes. The paper also concedes that it cannot be sure PRL134 used a single trajectory; the whole statistical-error argument depends on that inference plus a simplified AIM collision model with b_c = 2 a.u. The 43% and 100% numbers are illustrative for those conditions, not a measured property of PRL134. Using the same AIM threshold to estimate PRL134's statistical error is a bit self-referential, though the main comparison to PRL128 and to experiment is external.\n\nThe paper is honest about its own limitations, and the tone is more forensic than polemical. I would not take the factor-of-3 claim to the bank, but the methodological warning about single incommensurate trajectories is solid and worth heeding. The citation pattern is fine; self-citation here is appropriate since the AIM framework is their own prior work. The one problematic reference is the unpublished [14].\n\nWho should read this: anyone evaluating PRL134's results, and anyone doing rt-TDDFT stopping calculations with long trajectories. It deserves a serious referee, not a desk reject, because it offers new analysis and concrete methodological criticisms. If I were refereeing, I would ask for the 1.13 scaling to be made available or removed, and for the trajectory-count inference to be toned down to match the uncertainty.\n\nEndorse with caution.\n\nBest,\n[Your name]","headline":"This comment makes a plausible case that PRL134's low-velocity antiproton stopping curve is too low, but its strongest quantitative claim leans on an unpublished data rescaling and an uncertain inference about trajectory sampling.","tokens_in":8773,"tokens_out":1642,"would_cite":false,"duration_ms":18993,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["34.50.Bw"],"model":"deepseek-v4-flash","headline":"This comment argues that the anomalies reported in the stopping of slow antiprotons in LiF are artifacts: the disputed curve misses measured data by up to a factor of 3, and the incommensurate-trajectory method can carry a 43% mean error.","keywords":["electronic stopping","antiprotons","lithium fluoride","time-dependent density functional theory","adiabatic ionization model","incommensurate trajectory","stopping power","low-velocity ions"],"falsifier":"Rerun the criticized calculation with a large set of random incommensurate starts (say 100) and the same pseudopotential: if the anomalous low-velocity knee persists in the averaged stopping, the sampling-artifact explanation is wrong. Conversely, rerunning with the pseudopotential singularity removed should change the stopping by roughly 20% at high velocities if the pseudopotential critique is right.","tokens_in":7798,"feed_emoji":"⚛️","tokens_out":7550,"duration_ms":76707,"temperature":0.7,"pith_summary":"This comment tries to establish that the anomalies in the electronic stopping of slow antiprotons in LiF reported in the commented Letter are not a genuine physical effect. It argues that the Letter's low-velocity stopping curve deviates from the published experimental antiproton data by up to a factor of 3, while the Adiabatic Ionization Model and an earlier real-time time-dependent density-functional calculation reproduce the measurements. The main technical accusation is that the Letter used a single incommensurate trajectory of finite length, and the authors show with histograms that such a trajectory can carry a 43% mean statistical error, or as much as 100% for the particular golden-ratio direction, depending on the starting point. A secondary target is the Letter's use of a Coulomb pseudopotential, which may suppress long-range dipole contributions to the energy loss. If the comment is right, the reported anomalies are sampling artifacts plus pseudopotential artifacts rather than new physics.","feed_headline":"One trajectory may explain the LiF slow-antiproton anomaly","feed_subtitle":"A comment finds the disputed stopping curve misses measured data by up to 3x and carries 43% sampling error.","key_machinery":"The load-bearing mechanism is the Adiabatic Ionization Model (AIM): the stopping power $S_e(v) = \\pi P_{\\mathrm{cont}}\\Delta E_{\\mathrm{trans}} b_c(v)^2$, where $b_c(v)$ is the largest impact parameter at which half the collisional energy broadening $\\Gamma(v)/2$ crosses the antiproton-lowered adiabatic excitation gap of LiF. The gap curve comes from self-consistent cluster calculations showing that the F-2p orbital is promoted until the gap vanishes near $R \\approx 2$ a.u. The same $b_c=2$ a.u. cutoff is then used as a simplified collision statistic in histograms for incommensurate trajectories, which is what produces the 43% versus 12% mean-error contrast between two trajectory directions.","core_discovery":"On the paper's own terms, the central claim is that the anomalies reported for slow antiprotons in LiF are not physical. The comment compares the criticized real-time TDDFT curve with corrected experimental data and finds deviations that reach a factor of 3 at low speeds, whereas the Adiabatic Ionization Model, built from self-consistent adiabatic excitation thresholds and collisional broadening, reproduces the data below about 0.5 a.u. It further argues that the incommensurate-trajectory method, if used with a single trajectory of about 48 Å, has large statistical fluctuations: with a fixed critical impact parameter $b_c=2$ a.u., the golden-ratio trajectory direction has a 43% mean error and can miss all close collisions (error $-100\\%$), so the knee-like anomaly in the commented Letter may be a sampling artifact. The comment also targets the pseudopotential: a Coulomb pseudopotential that removes the singularity or suppresses the long-range dipole interaction can remove about 20% of the stopping at high velocities and far more at low velocities.","pith_inferences":["I would infer that the same single-trajectory sampling critique applies to any incommensurate-trajectory stopping calculation with finite path length, not only to LiF, whenever the energy loss is dominated by rare close collisions.","A decisive test would be to rerun the criticized calculation with 100 random starting points and the same pseudopotential: the comment's histogram model implies the stopping estimate should scatter by tens of percent, which would show up as a spread in the extracted slope.","If the pseudopotential critique is correct, the reported anomaly should be sensitive to the potential's core treatment; varying the pseudopotential in a controlled way would separate sampling error from interaction error."],"forward_implications":["The low-velocity knee reported for antiprotons in LiF should not be cited as evidence for anomalous stopping physics if it disappears once many trajectories are averaged.","The Adiabatic Ionization Model, with a nearly constant energy loss below roughly $v=0.3$ a.u. down to the capture limit, becomes the working description of low-velocity antiproton stopping in LiF.","Incommensurate-trajectory calculations of stopping in crystals should report convergence over at least ten independent trajectories to reach few-percent accuracy.","The choice of trajectory direction matters: a golden-ratio incommensurate direction can substantially worsen the sampling error relative to a generic direction.","Pseudopotential treatments of antiprotons need to be checked for removal of the Coulomb singularity and for suppression of the long-range dipole interaction, which materially change the stopping."],"supporting_citations":[{"why":"The criticized Letter whose claimed anomalies and methods are the target of the comment.","marker":"[1]"},{"why":"The measured antiproton stopping data used as the reference that the criticized curve misses by up to a factor of 3.","marker":"[5]"},{"why":"The earlier real-time TDDFT calculation whose low-velocity curve agrees with experiment and is contrasted with the criticized curve.","marker":"[6]"},{"why":"Self-consistent cluster calculations establishing the antiproton-induced vanishing gap that anchors the Adiabatic Ionization Model.","marker":"[3]"},{"why":"The earlier paper that formulates the Adiabatic Ionization Model and its collisional-broadening criterion.","marker":"[4]"},{"why":"The computational-methods paper cited as the source of the incommensurate trajectory direction used in the criticized calculation and in the comment's error histograms.","marker":"[20]"}],"fun_headline_variants":["Slow-antiproton LiF anomaly may be a sampling artifact","AIM model reproduces LiF antiproton data, anomaly questioned","Single-trajectory sampling may explain LiF antiproton anomaly","Disputed LiF stopping curve may miss data by 3x","LiF antiproton anomaly may stem from single-trajectory sampling"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The quantitative part of the critique assumes that the criticized paper used one (or very few) incommensurate trajectories and that the energy-loss statistics can be modeled by a fixed critical impact parameter of $b_c=2$ a.u.; if more trajectories were sampled, or if the real impact-parameter cutoff differs, the estimated 43% mean error and 100% worst-case error do not transfer.","fun_headline_variants_meta":{"raw":{"variants":["Slow-antiproton LiF anomaly may be a sampling artifact","AIM model reproduces LiF antiproton data, anomaly questioned","Single-trajectory sampling may explain LiF antiproton anomaly","Disputed LiF stopping curve may miss data by 3x","LiF antiproton anomaly may stem from single-trajectory sampling"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000775,"raw_usage":{"total_tokens":3436,"prompt_tokens":961,"completion_tokens":2475,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":577,"completion_tokens_details":{"reasoning_tokens":2393}},"tokens_in":577,"tokens_out":2475,"duration_ms":16093,"temperature":1.0,"reasoning_tokens":2393,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-16T04:52:23.458562+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Rerun the criticized calculation with a large set of random incommensurate starts (say 100) and the same pseudopotential: if the anomalous low-velocity knee persists in the averaged stopping, the sampling-artifact explanation is wrong. Conversely, rerunning with the pseudopotential singularity removed should change the stopping by roughly 20% at high velocities if the pseudopotential critique is right.","supporting_citations":[{"cited_title":"Anomalies in the electronic stopping of slow antiprotons in LiF","cited_arxiv_id":"2501.14381","evidence_quote":"The criticized Letter whose claimed anomalies and methods are the target of the comment."},{"cited_title":"Stopping Power in Insulators and Metals without Charge Exchange,","cited_arxiv_id":null,"evidence_quote":"The measured antiproton stopping data used as the reference that the criticized curve misses by up to a factor of 3."},{"cited_title":"Ab initio prediction of a negative barkas coefficient for slow protons and antiprotons in lif,","cited_arxiv_id":null,"evidence_quote":"The earlier real-time TDDFT calculation whose low-velocity curve agrees with experiment and is contrasted with the criticized curve."},{"cited_title":"Vanishing gap in lif for electronic excitations by slow antiprotons,","cited_arxiv_id":null,"evidence_quote":"Self-consistent cluster calculations establishing the antiproton-induced vanishing gap that anchors the Adiabatic Ionization Model."},{"cited_title":"Comprehensive analysis of the stopping power of antiprotons and negative muons in he and h2 gas targets,","cited_arxiv_id":null,"evidence_quote":"The earlier paper that formulates the Adiabatic Ionization Model and its collisional-broadening criterion."},{"cited_title":"Calculating electronic stopping power in materials from first principles,","cited_arxiv_id":null,"evidence_quote":"The computational-methods paper cited as the source of the incommensurate trajectory direction used in the criticized calculation and in the comment's error histograms."}],"review_version":1}