{"id":"62637de5-cb6e-4a08-830d-f5c85e61cf40","arxiv_id":"2504.15102","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"The muon flux inside the Kokhav HaYarden tunnel is measured at 3.75 x 10^-6 cm^-2 s^-1, about 4,456 times lower than at sea level.","lead":"Researchers measured how much the rock above a proposed Israeli underground lab weakens cosmic-ray muons, finding a suppression factor of about 4,456 compared with sea level. The result suggests the site, roughly 873 meters water equivalent, could host low-background experiments despite warm, humid conditions.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 4456x suppression rests on the TAU above-ground rate of 38 s^-1, but no dead-time or pileup correction is reported for that run; a rate-dependent test on the stored TAU triggers would settle whether the central flux claim holds.","rationale":"The reader's weakest assumption identifies the same load-bearing point: the suppression factor is a ratio between a high-rate reference run and low-rate underground runs, and the paper's cancellation argument covers only rate-independent systematics. I agree with that assessment. The concern is genuinely load-bearing because a rate-dependent inefficiency at TAU enters directly into the numerator of the suppression factor, while the quoted uncertainty is purely statistical. The paper's own statement that only statistical errors are reported makes this an explicit acknowledged limitation. The recommended verdict remains CONDITIONAL, exactly as the reader concluded, so no change to the verdict is required. This is not an accusation of an error; it is a request for the one systematic check that the analysis's cancellation argument cannot cover. If the inter-trigger gap test shows negligible dead time, the central claim would be substantially strengthened; if it shows a few percent dead-time fraction, the reported suppression factor and absolute flux would need revision.","tokens_in":7071,"tokens_out":6759,"duration_ms":68149,"concrete_test":"From the stored TAU run (11,000 triggers), build the histogram of time intervals between consecutive triggers and compare it with the exponential expected for Poisson-distributed muon arrivals. A deficit of short intervals quantifies the dead-time fraction; if that fraction is above ~1%, recompute the TAU rate and the Table 2 suppression factor with the dead-time correction and propagate the added systematic. If the inter-trigger timestamps were not saved, repeat the above-ground measurement at TAU for 10 minutes while a calibrated pulser injects 38 Hz into an unused DAQ channel, and compare the recorded pulser count with the injected count. A recorded/injected ratio of 1.000 +/- 0.001 would show dead time is negligible and resolve the concern.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section 4 and Table 2 define the central result as the ratio of the TAU trigger rate (3.80 +/- 0.04e1 s^-1) to the average KY rate (8.535e-3 s^-1). The paper argues that systematic uncertainties cancel because they are constant between runs, but rate-dependent effects are not constant: DAQ dead time, trigger re-arm time, PMT gain sag, and accidental coincidences all scale with singles rate and are far larger at TAU (38 Hz) than at KY (0.0085 Hz). The text explicitly reports 'only the statistical error here'; no dead-time measurement, no accidental-coincidence estimate, and no rate-dependence check is presented. A 2% rate loss at TAU would shift the suppression factor by about 90, outside the quoted +/-77; a 5% loss would shift it by about 220. The sentence claiming correlated muons 'can only increase the inferred shielding' is also hard to follow, since multi-muon events counted once would tend to reduce the TAU event rate and thus reduce the measured suppression. The absence of a quantitative rate-dependent systematic therefore leaves the headline flux 3.75 +/- 0.06e-6 cm^-2 s^-1 not yet demonstrated at the stated precision.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports a first exploratory muon-flux measurement at the proposed Kokhav HaYarden (KY) underground site in Israel, using a four-plate plastic scintillator hodoscope with a two-fold (top-plate) coincidence trigger. Data were taken above ground at Tel Aviv University (TAU) and underground at KY in two orientations, South-North and West-East. The central result is a suppression factor of 4456 ± 77 relative to TAU, corresponding to an integrated muon flux of 3.75 ± 0.06 × 10^-6 cm^-2 s^-1 and an effective vertical overburden of roughly 873 m.w.e. The paper also presents angular distributions that show the mountain's muon shadow, a simulation-based slant-depth map, and ancillary radon, temperature, and humidity measurements. The authors state that the quoted uncertainty is statistical only and that constant-efficiency systematics cancel in the ratio.","tokens_in":7326,"tokens_out":5140,"duration_ms":45770,"significance":"The direct ratio measurement is a simple and appropriate way to obtain a site-specific suppression factor without relying on detailed geological simulation, and the cancellation of detector-efficiency and acceptance terms that are constant between runs is a genuine strength. The angular distributions and the full-sky slant-depth map make the topographic effect directly visible, and the radon measurement is a useful auxiliary datum for site evaluation. If the rate-dependent systematic discussed below is quantified, the result would be a useful addition to the sparse literature on shallow and intermediate underground sites. At present, however, the headline precision is not demonstrated because the high-rate TAU run is not checked for dead time, pileup, or accidental coincidences.","major_comments":[{"comment":"The central suppression factor is defined as the ratio of the TAU rate (3.80 ± 0.04 × 10^1 s^-1) to the average KY rate (8.535 × 10^-3 s^-1), but no dead-time, pileup, or accidental-coincidence correction is reported for the TAU run. Rate-dependent losses do not cancel in the TAU/KY ratio because the trigger rates differ by more than three orders of magnitude; a 2% trigger loss at TAU changes the suppression factor by about 90, which is outside the quoted ±77 statistical uncertainty. The text explicitly reports \"only the statistical error here,\" so the claim of 4456 ± 77 is not yet demonstrated at the stated precision. Please use the stored TAU triggers or waveforms to measure dead time and check rate linearity, or add a quantitative conservative systematic uncertainty.","section":"§4, Table 2"},{"comment":"The sentence claiming that correlated muons \"can only increase the inferred shielding\" is unclear and appears to contradict the preceding multiplicity statement. If two or more muons arriving together are counted as a single trigger, the measured TAU rate is an underestimate of the true muon arrival rate, which would reduce the measured suppression factor rather than increase it. Please clarify the logic and, if multi-muon events are intended to be a correction, provide a quantitative estimate of their fraction at TAU.","section":"§4, correlated-muon sentence"},{"comment":"The effective overburden of 873 m.w.e. is obtained by inverting Eq. (1), but the cited Mei-Hime relation is stated to be appropriate for 1–10 km.w.e., and 873 m.w.e. lies below that range. Extrapolating the formula outside its stated validity could bias the inferred depth; please justify the extrapolation or use a depth-intensity relation validated at shallow depths. Also clarify whether the quoted 873 m.w.e. depends on the rock-density assumption (2.6 g cm^-3) used for the m.w.e. conversion in Fig. 2.","section":"§4, Eq. (1)"}],"minor_comments":[{"comment":"The flux value is written as \"3.75 ± 0.06 × 10^-6 cm^-2 s^-1\" in both the abstract and Section 4; please parenthesize the uncertainty as (3.75 ± 0.06) × 10^-6 cm^-2 s^-1 to avoid ambiguity.","section":"Abstract and §4"},{"comment":"The text says the muon shadow of the mountain is visible \"in the western direction,\" while the Fig. 10 caption describes an eastward bias in the W-E orientation; please make this consistent.","section":"§4 and Fig. 10"},{"comment":"Please state explicitly that the \"faulty\" events excluded from the angular distributions are nevertheless included in the trigger-rate counts used for the suppression factor, since the rate calculation is based on all triggers.","section":"§4, Fig. 11"},{"comment":"There are several typographical and formatting issues, including \"Tel A viv\" in the author affiliations, \"T able\" in table captions, \"auxillary\" in Table 3, and \"Galille\" in Section 1; these should be corrected.","section":"Throughout"}],"recommendation":"major_revision","confidential_remarks":"No confidential concerns beyond the content of the report. The manuscript is within the scope of physics.ins-det as a site-characterization measurement."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"You should know the main claim before reading: the Kokhav HaYarden site has a muon flux of 3.75e-6 cm^-2 s^-1, a suppression factor of 4456±77, measured with a four-plate scintillator hodoscope at one tunnel location. The stated errors are statistical only, and that matters.\n\nWhat is new: this is the first reported muon characterization at this site, directly useful for planning a low-background lab there. The angular mountain shadow is visible in the data, a nice site-specific cross-check. Using the same detector above and below ground is a sensible way to make efficiency and acceptance cancel. The two underground orientations agree (8.54 vs 8.53e-3 s^-1), which is reassuring. The radon measurement at ~28 Bq/m^3 is a bonus.\n\nThe soft spot is where the stress-test lands: the above-ground TAU run is 38.0±0.4 s^-1 and only about 4.8 minutes of data. No dead-time, pileup, or accidental-coincidence correction is reported. The paper explicitly says 'We report only the statistical error here.' If the true TAU rate is 2% higher due to dead-time losses, the suppression factor drops by ~90, outside the quoted ±77. That is a small relative effect in the big picture, but it means the central flux value is not demonstrated at the stated precision. I do not think the claim is wrong; I think it is under-quantified. The authors should re-analyze stored TAU triggers for rate dependence or do a dedicated high-rate test. The sentence about correlated muons is confusing and should be rewritten.\n\nA minor issue: the effective depth of 873 m.w.e. is derived from a formula whose stated range is 1–10 km.w.e. The authors acknowledge this and give a simulation cross-check at ~860 m.w.e., so it is acceptable as an approximate estimate, but not as a precise number.\n\nFor whom: groups evaluating shallow underground sites, especially for the proposed Israeli lab, and anyone planning material screening or low-threshold experiments there. It deserves peer review; the main measurement is straightforward and likely correct, but the dead-time question must be answered before the paper is accepted.","headline":"A useful first muon-flux measurement at a candidate Israeli underground site, with a plausible suppression factor, but the claimed precision rests on an unquantified above-ground dead-time correction.","tokens_in":7834,"tokens_out":3080,"would_cite":false,"duration_ms":28746,"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":"A tunnel under Kokhav HaYarden suppresses atmospheric muons by a factor of 4,456, with an effective overburden of about 873 m.w.e.","keywords":["underground laboratory","atmospheric muons","muon flux suppression","scintillator hodoscope","cosmic rays","low-background experiments","Kokhav HaYarden","superconducting qubits"],"falsifier":"Run the same hodoscope above ground while lowering the photomultiplier high voltage in steps and record the trigger rate; if the rate does not scale linearly with the muon rate, then the efficiency is rate-dependent and the sea-level rate used in the suppression factor is biased. A second check is to compare the measured angular muon distribution at Kokhav HaYarden with a full muon transport simulation using the actual rock density; a systematic angular offset would implicate the slant-depth model rather than the flux measurement.","tokens_in":6901,"feed_emoji":"⚛️","tokens_out":9681,"duration_ms":74198,"temperature":0.7,"pith_summary":"The paper reports the first direct measurement of the residual atmospheric muon flux at a candidate underground laboratory site inside the Kokhav HaYarden pumped-storage tunnels in Israel. Using a four-plate plastic scintillator hodoscope run both above ground and under 361 m of rock, the authors measure a suppression factor of $4456 \\pm 77$ relative to sea level, an absolute integrated flux of $3.75 \\times 10^{-6}$ cm$^{-2}$ s$^{-1}$, and an effective flat overburden of roughly 873 m.w.e. If the measurement holds, the site would sit at an intermediate depth between shallow and deep underground laboratories, useful for material screening, low-background testing, low-mass dark matter searches, and radiation-sensitive quantum devices. The paper also reports a low radon level of $28.3 \\pm 14.0$ Bq m$^{-3}$ and an angular muon shadow from the mountain topography, both supporting the site's working conditions for future experiments.","feed_headline":"Muon flux drops 4,456-fold in an Israeli tunnel site","feed_subtitle":"Proposed Israeli lab would get 873 m.w.e. shielding and low radon for rare-event searches.","key_machinery":"The central object is a portable muon hodoscope: four vertically stacked plastic scintillator plates ($144 \\times 60 \\times 1.2$ cm$^3$) with photomultiplier tubes at both ends of each plate, triggered by a coincidence on the top two plates and read out by two oscilloscopes. Track angles are reconstructed from the time delay between the two PMTs on each plate, giving a one-dimensional position along the plate and hence a zenith angle. The argument is carried by the ratio of trigger rates at the two sites: because the same detector, threshold, and geometry are used above ground and underground, the efficiency and acceptance factors cancel, so the rate ratio is the flux suppression factor. The measured suppression is then converted to an equivalent vertical depth using the differential muon intensity function $I_\\mu(h_0) = 68 \\times 10^{-6} e^{-h_0/285} + 2 \\times 10^{-6} e^{-h_0/698}$ (with $h_0$ in m.w.e.), and cross-checked against a simulation that propagates a Gaisser-parametrized muon spectrum through a two-dimensional slant-depth map built from elevation data.","core_discovery":"The central claim is that the integrated atmospheric muon flux at the Kokhav HaYarden site is suppressed by a factor of $4456 \\pm 77$ relative to sea level, corresponding to $3.75 \\times 10^{-6}$ cm$^{-2}$ s$^{-1}$ and an equivalent vertical depth of about 873 m.w.e. The authors establish this by measuring the trigger rate of a hodoscope with identical geometry at the above-ground Tel Aviv University site and at the underground site, in two orientations, and taking the ratio so that detector efficiency and acceptance cancel. They further show that the angular distribution of reconstructed muon tracks is biased away from the thickest rock overburden, revealing the muon shadow of the mountain, and that the local radon concentration is low. A simplified simulation that propagates a standard parametrization of the sea-level muon spectrum through the slant-depth map predicts about 860 m.w.e., in good agreement with the measured value. The conclusion is that the tunnel branch offers working conditions suitable for a new low-radiation underground laboratory, with the option of 25% more overburden deeper in the tunnel.","pith_inferences":["Inference: if the rate-ratio cancellation is robust, the same hodoscope could be redeployed at Manara with a longer sea-level control run to test for rate-dependent losses, since a small dead-time correction at the high above-ground rate would shift the quoted suppression factor.","Inference: the agreement between the measured 873 m.w.e. and simulated 860 m.w.e. suggests the elevation-derived slant-depth map and a uniform rock density of 2.6 g cm$^{-3}$ are adequate for survey-level planning, but a direct density measurement would tighten the depth estimate.","Inference: for superconducting qubit experiments, a factor-of-4,456 reduction in ionizing radiation could meaningfully lower radiation-induced quasiparticle poisoning, provided the site's humidity and temperature are controlled.","Inference: the measured flux could be compared against depth-flux curves from other intermediate-depth labs; a systematic offset would point to local rock composition or the sea-level normalization rather than the detector."],"forward_implications":["At roughly 873 m.w.e., the Kokhav HaYarden site sits between shallow and deep underground laboratories, making it a candidate for material screening, high-voltage component testing, low-mass dark matter searches, and some neutrino experiments.","The deeper, currently inaccessible part of the tunnel would add about 25% more vertical rock, which would further reduce the muon flux below the already measured suppression.","The low radon activity of $28.3 \\pm 14.0$ Bq m$^{-3}$ means radon is not a limiting background for the planned uses, although the high temperature and humidity will require attention.","The measured angular muon shadow confirms that the slant-depth map built from elevation data captures the real overburden, validating the simulation-based estimate of about 860 m.w.e.","The same portable hodoscope and ratio method can be carried to the deeper Manara pumped-storage site, which could reach roughly 2000 m.w.e. and enter the depth class of established deep laboratories."],"supporting_citations":[{"why":"Supplies the reference sea-level muon flux of $1.67 \\times 10^{-2}$ cm$^{-2}$ s$^{-1}$ that anchors the absolute flux normalization.","marker":"[18]"},{"why":"Provides the differential muon intensity function used to convert the measured flux into the equivalent vertical depth of about 873 m.w.e.","marker":"[19]"},{"why":"Supplies the continuous muon energy-loss model and the standard sea-level spectrum used in the simulation that predicts about 860 m.w.e.","marker":"[15]"},{"why":"Provides the elevation data from which the slant-depth maps and the two-dimensional overburden profile are built.","marker":"[14]"},{"why":"Describes the cosmic-ray hodoscope design whose scintillator plates and readout form the measurement apparatus.","marker":"[16]"},{"why":"Documents the precedent of a pumped-storage tunnel site (YangYang) hosting low-background physics, supporting the site-viability argument.","marker":"[10]"}],"fun_headline_variants":["Israeli tunnel: muon flux 4,456× lower, low radon","Proposed Israeli lab: 4,456× muon cut, low radon","Muon suppression 4,456× measured in Israeli tunnel","Underground Israeli lab site: muon flux 4,456× lower"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The suppression factor assumes that the above-ground trigger rate of about $3.8 \\times 10^1$ s$^{-1}$ at Tel Aviv University is not distorted by dead time or by two muons arriving close together, so that the detector's efficiency and acceptance cancel exactly between the above-ground and underground runs; the paper quotes only statistical errors and does not quantify rate-dependent effects.","fun_headline_variants_meta":{"raw":{"variants":["Israeli tunnel: muon flux 4,456× lower, low radon","Proposed Israeli lab: 4,456× muon cut, low radon","Muon suppression 4,456× measured in Israeli tunnel","Underground Israeli lab site: muon flux 4,456× lower"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000627,"raw_usage":{"total_tokens":2972,"prompt_tokens":1087,"completion_tokens":1885,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":703,"completion_tokens_details":{"reasoning_tokens":1801}},"tokens_in":703,"tokens_out":1885,"duration_ms":14350,"temperature":1.0,"reasoning_tokens":1801,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-16T11:32:37.719251+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same hodoscope above ground while lowering the photomultiplier high voltage in steps and record the trigger rate; if the rate does not scale linearly with the muon rate, then the efficiency is rate-dependent and the sea-level rate used in the suppression factor is biased. A second check is to compare the measured angular muon distribution at Kokhav HaYarden with a full muon transport simulation using the actual rock density; a systematic angular offset would implicate the slant-depth model rather than the flux measurement.","supporting_citations":[{"cited_title":": Review of particle physics","cited_arxiv_id":null,"evidence_quote":"Supplies the continuous muon energy-loss model and the standard sea-level spectrum used in the simulation that predicts about 860 m.w.e."},{"cited_title":"https://developers.google.com/ maps/documentation/elevation (2025)","cited_arxiv_id":null,"evidence_quote":"Provides the elevation data from which the slant-depth maps and the two-dimensional overburden profile are built."},{"cited_title":"Models of the Universe based on Jordan algebras","cited_arxiv_id":"2003.13527","evidence_quote":"Describes the cosmic-ray hodoscope design whose scintillator plates and readout form the measurement apparatus."}],"review_version":1}