{"id":"67570e5d-cd06-4d82-8061-e903bcc01c44","arxiv_id":"2608.05284","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":10,"one_line_summary":"Excited dark matter that is stable in vacuum can decay near Earth into two fast muons, giving neutrino telescopes a nearly background-free signal.","lead":"This paper proposes that excited dark matter particles, which are stable in empty space, can decay rapidly inside or near the Earth into pairs of energetic muons. Large neutrino telescopes such as IceCube and KM3NeT would see these as two non-collimated tracks from one point, a signal with almost no Standard Model background.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Kinetic-mixing channel cannot tolerate even mild screening of the scalar profile: rescaling M to hold epsilon=1e-20 speeds the vacuum decay by F^4 and violates gamma-ray bounds.","rationale":"The reader identified Eq. (6) and the unscreened long-range scalar profile as the weakest assumption. My analysis agrees and sharpens it: not only would screening reduce event rates, but in the kinetic-mixing realization this reduction cannot be compensated by adjusting the effective operator scale M without making the vacuum decay too fast. The vacuum and matter-induced widths have the same 1/M^4 dependence, so their ratio is fixed by phi^4 once epsilon is chosen. This makes the benchmark quantitatively fragile to any O(1) deviation from the linear profile. The paper itself acknowledges the illustrative nature of Eq. (6), so the CONDITIONAL verdict is appropriate. A single quantitative check, recomputing the vacuum lifetime under a screened phi, would settle whether this concern lands. If the gamma-ray bound is robust, the kinetic-mixing channel is viable only in the unscreened limit; the mass-shift channel is less fragile but still constrained by self-interaction bounds when y1 is pushed up. No fatal internal inconsistency was found, and the reader's verdict of CONDITIONAL is the right level of confidence.","tokens_in":11180,"tokens_out":35783,"duration_ms":327547,"concrete_test":"Fix the Sec. III B benchmark (g_chi=1, m_Z'=1 TeV, Delta m=300 GeV, epsilon=1e-20, phi_0=9e3 GeV). For F=1,3,10, set phi_F=phi_0/F and M_F=phi_F/sqrt(1e-20); evaluate Eq. (17) for the near-Earth lifetime and Eq. (18) for the vacuum lifetime. Check whether tau_vac remains above the isotropic gamma-ray bound (~1e27 s). If it drops below for F>1, the kinetic-mixing scenario requires the scalar field at Earth's surface to be unscreened to within a factor of a few.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The observable rates rest on Eq. (6), the unscreened, long-range scalar field phi(R_oplus). The paper calls this illustrative, but the tension is sharper than generic screening. In Sec. III B, the near-Earth width scales as (phi/M)^4 while the vacuum width scales as 1/M^4. If screening reduces phi by a factor F, keeping the required epsilon=(phi/M)^2~1e-20 forces M down by the same factor, boosting the vacuum width by F^4. For the stated benchmark, the vacuum width is already only a factor ~1e9 below the near-Earth width; a suppression F~3 lowers tau_vac to ~1e27 s, right at the isotropic gamma-ray limit, and F~10 is excluded. Thus the kinetic-mixing signal cannot be rescued by lowering M; it requires phi to be within a factor ~3 of the linear profile. In the mass-shift case, compensation via larger y1 drives y1 toward O(0.1), where DM self-interaction constraints become marginal. The central observability claim is therefore contingent on the unscreened limit being accurate to better than an order of magnitude.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper proposes a new observable signature of dark matter decay in large-volume neutrino telescopes: dimuon events with non-negligible opening angle and negligible Standard Model background. The central idea is matter-induced decay of a long-lived excited dark matter state chi2 in the presence of the Earth. Two mechanisms are presented. First, a long-range scalar field phi sourced by nucleons shifts the dark-sector masses (Eqs. 7-8), kinematically opening chi2 -> chi1 Z' near Earth (Eqs. 10-12). Second, the scalar induces environmental kinetic mixing epsilon = phi^2/M^2 (Eq. 14), enhancing chi2 -> chi1 mu+ mu- in matter-rich regions (Eqs. 16-17). The paper calculates decay kinematics (opening-angle distributions, Eqs. 21, 23-24), argues that neutron-star heating is not constraining (Sec. V), and briefly discusses CHAMP-induced multi-muon events (Sec. VI). The claimed rates are roughly one to ten dimuon events per cubic kilometer per year for benchmark parameters, in scenarios that evade vacuum decay constraints.","tokens_in":11482,"tokens_out":3313,"duration_ms":26348,"significance":"If the rates hold, the experimental signature, a dimuon event with a common vertex and no Standard Model background, is genuinely novel and would motivate dedicated searches in IceCube and KM3NeT. The paper is careful to check against several external constraints (positron spectrum, isotropic gamma-ray background, fifth-force bounds, neutron-star heating), and the rate estimates follow from clearly stated Lagrangians and benchmark parameters. The individual components are not new, but the combined matter-induced decay channel for neutrino telescopes is a fresh idea with falsifiable predictions.","major_comments":[{"comment":"The kinetic-mixing signal is not robust to rather mild suppression of the scalar field. Eq. (17) requires epsilon ~ phi^2/M^2 = 1e-20, while Eq. (18) gives the vacuum rate scaling as 1/M^4. If screening reduces phi by a factor F, keeping epsilon fixed forces M down by F, so the vacuum width increases by F^4. The manuscript states in Sec. III.B that the vacuum decay is smaller than the near-Earth rate by a factor of about 1e9; this factor shrinks to about 1e9/F^4, so F ~ 5-10 already puts the vacuum gamma-ray production at or above the limits quoted from Refs. [21,32]. The assertion of consistency with gamma-ray constraints therefore holds only if the unscreened linear profile in Eq. (6) is accurate to better than an order of magnitude. This is load-bearing because the same concern cannot be fully compensated by lowering M.","section":"III.B and Eqs. (14)-(18)"},{"comment":"The mass-shift rate in Eq. (12) is proportional to [(Delta m_eff)^2 - m_Z'^2]^{3/2}, so it is highly sensitive to the scalar field value at the Earth's surface. Eq. (6) is explicitly an unscreened linear limit, acknowledged as illustrative at the end of the paragraph containing Eq. (6), but the benchmark value y_N ~ 10^-26 is chosen so that phi gives shifts of order 100 GeV. If screening, nonlinearities, or a finite scalar range suppress phi at the surface by even a factor of a few, the threshold condition Delta m_eff > m_Z' fails and the rate vanishes. The paper does not quantify the allowed suppression for the mass-shift channel, so the central rate claim rests on Eq. (6) being approximately correct at the Earth's surface.","section":"III.A and Eqs. (6)-(12)"},{"comment":"The headline event rates of about 0.6 yr^-1 km^-3 in Eq. (4) are physical decay rates per volume in the medium, not detector event rates. The paper nowhere includes an effective detector volume (the reported IceCube and KM3NeT detector sizes are not used), a muon reconstruction efficiency, a containment requirement for the common vertex, or a trigger threshold beyond the statement in Sec. IV that both muons must have E_mu > 100 GeV. For a signal defined by two muon tracks emerging from a common vertex inside the instrumented volume, these are large multiplicative effects, plausibly O(1-10). The abstract and conclusions should state that the rates are rates per volume in the medium, not projections for a specific detector.","section":"III.A-III.B and Eq. (4)"}],"minor_comments":[{"comment":"The normalization in Eq. (12) is written with the ratio (300^2 - 200^2)/[(Delta m_eff)^2 - m_Z'^2]^{3/2}, which is dimensionally awkward; expressing the phase-space factor as [(Delta m_eff/m_Z')^2 - 1]^{3/2} would be clearer.","section":"III.A, Eq. (12)"},{"comment":"The joint distribution d^2 Gamma / dm_mumu dcos theta is presented without its normalization; stating the numerical median opening angle of 75 degrees without a plot or an explicit integrated distribution makes the result hard to reproduce. A figure showing the opening-angle distribution for the benchmark would help.","section":"IV, Eq. (24)"},{"comment":"The sentence stating that the kinematically allowed opening angles range from about 93.3 to 180 degrees appears before the muon energy cut is applied; as written it seems inconsistent with the subsequent statement that the energy cut restricts the angles to 93.3-98.2 degrees. Clarify that the second range is after applying E_mu > 100 GeV.","section":"IV, after Eq. (21)"},{"comment":"The CHAMP rate estimate uses N_p ~ 10^39 protons in a cubic kilometer but then quotes the rate per km^3; the sentence around Eq. (27) should state explicitly that Y_X is the abundance per proton and that the CHAMPs are assumed to be distributed uniformly in the detector volume.","section":"VI, Eq. (27)"},{"comment":"The operator (phi/M)^2 Z'_mu_nu F^mu_nu is presented as a phenomenological choice with n=2; the text could state whether this operator can be UV-completed without introducing a new hierarchy problem or whether it should be read as a low-energy EFT.","section":"III.B, Eq. (14)"}],"recommendation":"major_revision","confidential_remarks":"The paper would be suitable for the journal if the authors either show that the linear profile in Eq. (6) is stable under the relevant screening and finite-range corrections, or explicitly present the gamma-ray constraint as a function of the suppression factor F and the mass-shift threshold as a function of the profile. The kinetic-mixing channel is the more fragile of the two because the vacuum width scales as 1/M^4. I also note that the manuscript presents the benchmark at m_chi2 = 1 TeV and Delta m = 300 GeV with m_Z' = 200 GeV, which makes the Z' on-shell in the mass-shift scenario; the paper should verify that the on-shell muon pair from Z' -> mu+ mu- actually satisfies the E_mu > 100 GeV requirement used in Sec. IV. This check is not present in the text and would affect the rate estimate."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Two things to know. First, this is a genuinely new search target: dark matter decaying near Earth into a pair of energetic, wide-angle muons. That topology is essentially background-free in neutrino telescopes, and the paper gives a concrete opening-angle prediction—for the mass-shift benchmark with both muons above 100 GeV, the opening angle sits between about 93 and 98 degrees—which a search can use directly. Second, the event rates all rest on Eq. (6), the unscreened long-range scalar profile, and the paper is honest that this is illustrative.\n\nI checked the stress-test arithmetic and it holds. For the kinetic-mixing channel, a screening suppression of phi by a factor F forces M down by F to keep epsilon fixed, and the vacuum width then grows as F^4. A factor F~3 brings the vacuum lifetime down to ~1e27 s, right at the isotropic gamma-ray bound; F~10 is excluded. That channel is therefore not just uncertain—it requires the unscreened profile to be accurate to within a factor of a few. The mass-shift channel is more tolerant, but compensating for screening pushes y1 toward O(0.1), where dark-matter self-interaction constraints become relevant, and the paper does not discuss them.\n\nWhat the paper does well: the two mechanisms are clearly formulated, the benchmark lifetime and rate estimates are easy to reproduce, and the authors check against gamma-ray, fifth-force, and neutron-star constraints. The CHAMP discussion is explicitly preliminary, which is fine.\n\nSoft spots beyond screening: the quoted rates are per cubic kilometer per year, not per detector after reconstruction. Requiring both muons to have E > 100 GeV already restricts the opening-angle window; trigger and track-reconstruction efficiency will cut further, and none of that is quantified. The f_chi2 ~ 0.5 abundance is a hand-picked input. These are addressable gaps, not fatal flaws.\n\nBottom line: this deserves a serious referee. The central idea is coherent, the signature is concrete, and a referee can reasonably ask for a screening analysis and a detector-level estimate before publication. I would not desk-reject it.","headline":"A concrete new dimuon signature for matter-induced dark matter decay, but the rates rest on an unscreened scalar profile that needs closer scrutiny.","tokens_in":12024,"tokens_out":4353,"would_cite":true,"duration_ms":40298,"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 argues that a dark matter component that is long-lived in vacuum could decay at observable rates near Earth, producing pairs of non-collimated muons that large-volume neutrino telescopes could see with almost no Standard Model…","keywords":["dark matter decay","matter-induced decay","dimuon events","neutrino telescopes","long-range scalar field","kinetic mixing","excited dark matter","IceCube"],"falsifier":"Run a dedicated search in IceCube and KM3NeT for events with two muon tracks (each $E_\\mu \\gtrsim 100$ GeV) emerging from a common vertex with opening angles between about $10^\\circ$ and $90^\\circ$; the absence of such events in roughly 10 km$^3$ years of exposure would exclude the benchmark lifetimes in Eqs. (12) and (17), while a handful of events would support the mechanism.","tokens_in":10935,"feed_emoji":"🧊","tokens_out":15021,"duration_ms":120185,"temperature":0.7,"pith_summary":"This paper argues that a class of dark matter models that is invisible to conventional searches becomes testable when the Earth itself acts as a catalyst. An excited dark state $\\chi_2$ that is effectively stable in vacuum can decay much faster inside or near ordinary matter, because nucleons source a long-range scalar field. In the first realization the field shifts the dark masses so that the two-body decay $\\chi_2 \\to \\chi_1 Z'$ (with $Z'$ a new heavy gauge boson) opens up near Earth, with a benchmark lifetime of about $1.5 \\times 10^{18}$ s; in the second it generates kinetic mixing that enables $\\chi_2 \\to \\chi_1 \\mu^+ \\mu^-$, with a benchmark lifetime near $8 \\times 10^{19}$ s. Both channels produce pairs of energetic, non-collimated muons from a common vertex at rates of order one to ten events per cubic kilometer per year, a topology with negligible Standard Model background. That is the pith: matter-induced decay could make a previously invisible dark sector observable in existing neutrino telescopes.","feed_headline":"Dark matter could decay near Earth, lighting up neutrino telescopes","feed_subtitle":"Two matter-triggered decay channels would create nearly background-free muon pairs in IceCube and KM3NeT.","key_machinery":"The load-bearing object is the classical scalar field $\\phi$ sourced by ordinary nucleons through the Yukawa term $-y_N \\phi \\bar{N} N$. In the unscreened spherical-Earth limit its surface value is $\\phi(R_\\oplus) \\approx -y_N M_\\oplus / (4\\pi R_\\oplus m_N)$, which is small in coupling but enormous in aggregate because the Earth contains about $10^{51}$ nucleons. That field then does one of two jobs. In the mass-shift scenario it enters the effective dark masses $m_{\\chi_i}^{\\rm eff} = m_{\\chi_i} + y_i \\phi$, changing the $\\chi_2$-$\\chi_1$ mass splitting and, when $(y_2 - y_1)\\phi$ bridges the gap $m_{Z'} - (m_{\\chi_2} - m_{\\chi_1})$, kinematically opens $\\chi_2 \\to \\chi_1 Z'$. In the kinetic-mixing scenario it appears in the operator $\\frac{1}{2}(\\phi/M)^2 Z'_{\\mu\\nu} F^{\\mu\\nu}$, which after diagonalization gives the $Z'$ a photon-like coupling to muons suppressed by $\\varepsilon = \\phi^2/M^2$ and enables $\\chi_2 \\to \\chi_1 \\mu^+\\mu^-$. The huge nucleon number is what converts extremely small couplings like $y_i y_N \\sim 10^{-26}$ into GeV-scale effects.","core_discovery":"The paper shows that an excited dark matter component $\\chi_2$ that is stable, or nearly stable, in vacuum can decay at observable rates near ordinary matter. Ordinary nucleons source a classical scalar field that either shifts the dark-state masses or induces kinetic mixing between a heavy $Z'$ and the photon. With benchmark parameters $g_\\chi = 10^{-22}$, $m_{Z'} = 200$ GeV, and a 300 GeV vacuum mass splitting, the mass-shift scenario gives $\\tau(\\chi_2 \\to \\chi_1 Z') \\approx 1.5 \\times 10^{18}$ s; with $\\varepsilon \\approx 10^{-20}$, $m_{Z'} = 1$ TeV, and the same splitting, the kinetic-mixing scenario gives $\\tau(\\chi_2 \\to \\chi_1 \\mu^+\\mu^-) \\approx 8 \\times 10^{19}$ s. These lifetimes correspond to event rates of roughly one to ten dimuon events per cubic kilometer per year at the local dark matter density, and the paper computes that the muon pairs emerge with broad opening angles and energies of order 100 GeV or more, making them reconstructable in large-volume neutrino telescopes and essentially free of Standard Model background.","pith_inferences":["Inference: the same Earth-sourced scalar would also be sourced by the Sun, so solar-region enhancement of $\\chi_2$ decay is a natural extension; the paper does not quantify it, but it could make the Sun a complementary target.","Inference: a null result from the proposed dimuon search would translate directly into upper bounds on the product of the nucleon-scalar coupling and the dark gauge coupling (or the kinetic-mixing scale), because the event-rate formula is linear in the inverse lifetime.","Inference: the caution the authors raise about extrapolating the linear scalar profile to neutron-star densities applies equally to the Sun and white dwarfs; if screening sets in at high density, the mechanism might only operate near lower-density bodies, which would change which telescopes can see it."],"forward_implications":["IceCube, KM3NeT, Baikal-GVD, and Super-Kamiokande can search for the common-vertex dimuon topology with essentially no Standard Model background, so even a handful of events would be a discovery.","Published constraints on cosmic-ray positrons and the isotropic gamma-ray background do not exclude these decays, because the vacuum decay rate is suppressed by roughly nine orders of magnitude relative to the matter-enhanced rate.","Sparsely instrumented arrays are sensitive only when the dark mass splitting is roughly $\\gtrsim 200$ GeV, while denser detectors such as Super-Kamiokande, KM3NeT/ORCA, and the IceCube Upgrade could probe smaller splittings.","Neutron-star heating does not close the window: even maximal energy deposition from incident $\\chi_2$ particles would keep a neutron star near $5 \\times 10^{-3}$ eV, below observational sensitivity.","IceCube could also constrain cosmologically long-lived charged massive particles, whose decays into muon pairs could yield up to about $10^3$ events per cubic kilometer per year at the currently allowed abundance."],"supporting_citations":[{"why":"These cosmic-ray positron constraints are used to show that conventional dark matter annihilation and decay cannot produce an observable dimuon rate.","marker":"[20, 29–31]"},{"why":"The isotropic gamma-ray background limits on decaying dark matter are what force the matter-induced mechanism, since vacuum decay must be far below observable rates.","marker":"[21, 32]"},{"why":"The local dark matter density $\\rho = 0.4$ GeV/cm$^3$ supplies the normalization for converting decay lifetimes into event rates per cubic kilometer.","marker":"[28]"},{"why":"These $L_\\mu - L_\\tau$ gauge-boson models motivate a new $Z'$ that couples to muons, the final-state particle in the proposed signals.","marker":"[33–37]"},{"why":"The chameleon, symmetron, and environmental-mass constructions provide the pattern for making particle masses depend on the matter-sourced scalar field.","marker":"[38–41]"},{"why":"This work supplies the environmentally dependent kinetic-mixing operator that is the basis of the second decay scenario.","marker":"[42]"},{"why":"Fifth-force and MICROSCOPE measurements bound the nucleon-scalar coupling $y_N$, and therefore the size of the surface field used in the rate estimates.","marker":"[43, 44]"},{"why":"The cold neutron star temperature observation is used to argue that matter-enhanced dark matter decays would not cause anomalous neutron-star heating.","marker":"[46]"}],"fun_headline_variants":["Matter triggers dark matter decay: new muon pairs","Dark matter decays near Earth, creating detectable muon pairs","Neutrino telescopes could spot matter-induced dark matter decay","Nearly stable dark matter decay near Earth: IceCube signal","When matter meets dark matter: decay lights up telescopes"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The entire signal rests on the Earth sourcing an unscreened, long-range scalar field whose surface value is given by Eq. (6); if screening, nonlinearities, or a finite scalar range suppress that field, the mass-shift and kinetic-mixing enhancements, and with them the observable event rates, go away.","fun_headline_variants_meta":{"raw":{"variants":["Matter triggers dark matter decay: new muon pairs","Dark matter decays near Earth, creating detectable muon pairs","Neutrino telescopes could spot matter-induced dark matter decay","Nearly stable dark matter decay near Earth: IceCube signal","When matter meets dark matter: decay lights up telescopes"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00024,"raw_usage":{"total_tokens":1583,"prompt_tokens":1077,"completion_tokens":506,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":693,"completion_tokens_details":{"reasoning_tokens":426}},"tokens_in":693,"tokens_out":506,"duration_ms":5121,"temperature":1.0,"reasoning_tokens":426,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-08T16:15:37.584807+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run a dedicated search in IceCube and KM3NeT for events with two muon tracks (each $E_\\mu \\gtrsim 100$ GeV) emerging from a common vertex with opening angles between about $10^\\circ$ and $90^\\circ$; the absence of such events in roughly 10 km$^3$ years of exposure would exclude the benchmark lifetimes in Eqs. (12) and (17), while a handful of events would support the mechanism.","supporting_citations":[{"cited_title":"Indirect Signals of Dark Matter Can Change Depending on Where You Look","cited_arxiv_id":"2208.04964","evidence_quote":"This work supplies the environmentally dependent kinetic-mixing operator that is the basis of the second decay scenario."}],"review_version":1}