Dark matter-neutrino interactions affect the propagation of astrophysical neutrinos, attenuating the flux of neutrinos arriving at Earth. Using the highest-energy neutrino event detected to date by the KM3NeT Collaboration as an example, and assuming an extragalactic origin, we derive limits on these interactions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>E</mi><mi>ν</mi></msub><mo>=</mo><mn>22</mn><msubsup><mn>0</mn><mrow><mo>−</mo><mn>110</mn></mrow><mrow><mo>+</mo><mn>570</mn></mrow></msubsup><mtext> </mtext><mtext> </mtext><mi>PeV</mi></math>. Considering only the propagation on the Milky Way dark matter halo, we constrain the interaction cross section over the mass of the dark matter candidate to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>σ</mi></mrow><mrow><mrow><mi>DM</mi><mo>−</mo></mrow><mi>ν</mi></mrow></msub><mo>/</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>DM</mi></mrow></msub><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>22</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>cm</mi></mrow><mrow><mn>2</mn></mrow></msup><mtext> </mtext><msup><mrow><mi>GeV</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>. If a transient source was positively identified, the high-energy neutrino would have crossed the dark matter halo of the source host as well, resulting in more stringent constraints (e.g., up to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>6</mn></math> orders of magnitude assuming the blazar PKS 0605-085 is the source). These bounds on the dark matter-neutrino interaction cross section are translated into limits on the mass of the dark matter candidate, the mass of the mediator, and the coupling strength for different simplified models. We find that the constraints from the KM3-230213A high-energy event for these simplified models are almost entirely ruled out for masses above the mega-electron-volts by unitarity constraints. Therefore, the attenuation of such energetic neutrinos by dark matter calls for richer dark sectors in order to produce meaningful constraints.

Spain

Toni Bertólez-Martínez

United States

Gonzalo Herrera

Denmark

Pablo Martínez-Miravé

Italy

Jorge Terol Calvo

Highest-energy neutrino event constrains dark matter-neutrino interactions

Recent results on the Coherent Elastic Neutrino-Nucleus Scattering (CE$\textit{ν}$NS) on germanium present significant discrepancies among experiments. We perform a combined analysis of the Dresden-II, CONUS+ and COHERENT data, quantifying the impact of quenching factor uncertainties on their CE$\textit{ν}$NS cross section measurement. No choice of quenching factor can bring these three data sets into mutual agreement, whereas the combination of COHERENT with either Dresden-II or CONUS+ agrees well albeit for very different quenching factors. We further study the quenching factor dependence on the sensitivity of these experiments to a large neutrino magnetic moment, finding that the constraints can vary by up to an order of magnitude. Our work highlights the importance of reducing this uncertainty on quenching factors in order to probe new physics from neutrinos at the low-energy frontier.

Yulun Li

Patrick Huber

New physics versus quenching factors in Coherent Neutrino Scattering

Generic constraints on dark photons are generally presented assuming they have Stueckelberg masses. These constraints are strengthened if instead the mass is due to the Higgs mechanism and the dark Higgs is light. First, we show that under reasonable assumptions on the origin of kinetic mixing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ε</mi></math> and perturbativity, the strengthened constraints on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ε</mi></math> cannot be arbitrarily relaxed by making the Higgs heavy. Second, we demonstrate a simple mechanism for generating dark photon dark matter after inflation, where fluctuations of a dark Higgs by stochastic misalignment can produce stable dark photons through <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mo stretchy="false">→</mo><msup><mi>A</mi><mo>′</mo></msup><msup><mi>A</mi><mo>′</mo></msup></math> decay. Third, we point out new lower bounds on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ε</mi></math> in the case where the dark photon mediates thermal freeze-out of light dark matter by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>s</mi></math>-channel exchange, taking account of generic expectations for the size of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ε</mi></math>, and astrophysical upper bounds on the self-interaction cross section.

CERN

Canada

James M. Cline

Plausible constraints and inflationary production for dark photons

The PandaX-4T and XENONnT experiments present indications of Coherent Elastic Neutrino Nucleus Scattering (CE$\textit{ν}$NS) from B solar neutrinos at 2.6$\textit{σ}$ and 2.7$\textit{σ}$, respectively. This constitutes the first observation of the neutrino “floor” or “fog”, an irreducible background that future dark matter searches in terrestrial detectors will have to contend with. Here, we first discuss the contributions from neutrino–electron scattering and from the Migdal effect in the region of interest of these experiments, and we argue that they are non-negligible. Second, we make use of the recent PandaX-4T and XENONnT data to derive novel constraints on light scalar and vector mediators coupling to neutrinos and quarks. We demonstrate that these experiments already provide world-leading laboratory constraints on new light mediators in some regions of parameter space.

Pablo Blanco-Mas

Pilar Coloma

Switzerland

Germany

Joachim Kopp

Ian Shoemaker

Zahra Tabrizi

Clarity through the neutrino fog: constraining new forces in dark matter detectors

We present a novel way to probe inelastic dark matter using cosmic-ray (CR) cooling in active galactic nuclei (AGNs). Dark matter (DM) in the vicinity of supermassive black holes may scatter off CRs, resulting in the rapid cooling of CRs for sufficiently large cross sections. This in turn can alter the high-energy neutrino and gamma-ray fluxes detected from these sources. We show that AGN cooling bounds obtained through the multimessenger data of NGC 1068 and TXS <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>0506</mn><mo>+</mo><mn>056</mn></mrow></math> allows us to reach unprecedently large mass splittings for inelastic DM (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≳</mo><mi>TeV</mi></math>), orders of magnitude larger than those probed by direct detection experiments and DM capture in neutron stars. Furthermore, we demonstrate that cooling bounds from AGNs can probe thermal light DM with small mass splittings. This provides novel and complementary constraints in parts of a parameter space accessible solely by colliders and beam-dump experiments.

Japan

R. Andrew Gustafson

Mainak Mukhopadhyay

Kohta Murase

Ian M. Shoemaker

Cosmic-ray cooling in active galactic nuclei as a new probe of inelastic dark matter

Axionlike particles (ALPs) can be produced in gamma ray bursts, altering the polarization of the electromagnetic emission in these events. For the first time, we derive bounds on the axion-photon coupling from polarization measurements of GRB 221009A, performing a full calculation of the Stokes parameters, as it is typically done in the astrophysics community. Within astrophysical uncertainties, our limits on the axion-photon coupling are competitive with complementary probes in the axion mass range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>9</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi><mo>≲</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>8</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></mrow></math>, further allowing to probe motivated parameter space of ALP dark matter.

Boris Betancourt Kamenetskaia

Mexico

Nissim Fraija

Polarization measurements as a probe of axion-photon coupling: A study of GRB 221009A

We show that placing a radioactive source such as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi>Cr</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>51</mn></mrow></mmultiscripts></mrow></math> near a liquid xenon detector may allow us to detect the contribution induced by the anapole moment to neutrino-electron scattering in the Standard Model (SM) at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mo>−</mo><mn>2</mn><mi>σ</mi></mrow></math> level. Although the anapole moment of neutrinos induces a scattering rate with the same spectral shape as the neutral and charged current contributions, exposures of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo>∼</mo><mn>60</mn><mtext> </mtext><mtext> </mtext><mi>ton</mi><mo>×</mo><mi>source</mi></mrow></math> run at XENONnT or XLZD may be enough to accumulate sufficient statistics for a detection. We also discuss a simple model where the anapole moment of neutrinos is enhanced or decreased with respect to the SM expectation, further demonstrating how a potential measurement of the anapole moment of neutrinos would allow us to constrain new physics.

Anapole moment of neutrinos and radioactive sources near liquid xenon detectors

India

Subhasis Nalui

Subhra Bhattacharya

Addendum to “Herrera complexity and shadows of spherically symmetric compact objects” [Phys. Lett. B 861 (2025) 139261]

Energetic cosmic rays scatter off the cosmic neutrino background throughout the history of the Universe, yielding a diffuse flux of cosmic relic neutrinos boosted to high energies. We calculate this flux under different assumptions of the cosmic-ray flux spectral slope and redshift evolution. The nonobservation of the diffuse flux of boosted relic neutrinos with current high-energy neutrino experiments already excludes an average cosmic neutrino background overdensity larger than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><msup><mn>10</mn><mn>4</mn></msup></math> over cosmological distances. We discuss the future detectability of the diffuse flux of boosted relic neutrinos in light of neutrino overdensity estimates and cosmogenic neutrino backgrounds.

Shunsaku Horiuchi

Xiaolin Qi

Diffuse boosted cosmic neutrino background

We uncover two precise interpretations of traditional electroweak fine-tuning (FT) measures that were historically missed. (i) a statistical interpretation: the traditional FT measure shows the change in plausibility of a model in which a parameter was exchanged for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson mass relative to an untuned model in light of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson mass measurement. (ii) an information-theoretic interpretation: the traditional FT measure shows the exponential of the extra information, measured in nats, relative to an untuned model that you must supply about a parameter in order to fit the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> mass. We derive the mathematical results underlying these interpretations, and explain them using examples from weak scale supersymmetry. These new interpretations allow us to rigorously define FT in particle physics and beyond, shed fresh light on the status of extensions to the Standard Model and, lastly, allow us to precisely reinterpret historical and recent studies using traditional FT measures.

China

Andrew Fowlie

Precise interpretations of traditional fine-tuning measures