The LZ230616 event stands apart: it is a single high-energy nuclear recoil in the LZ detector, where the background is almost absent. Alongside this work, the archive contains studies linking dark matter to neutrino mass, examining Higgsinos in liquid xenon, and explaining rare signals in the LZ detector through an invisible conductor. There are also papers on the dineutron, the supernova neutrino background, and neutrinos from the early Universe. All of them, one way or another, search for new particles or interactions using xenon detectors. This paper tests the most conservative hypothesis: could the event have been caused by ordinary or exotic neutrinos through elastic scattering?
The authors calculated nuclear recoil spectra from coherent elastic neutrino-nucleus scattering on xenon nuclei. They used an LZ exposure of 2.84 tonne·year and accounted for the detector's energy resolution through Gaussian smearing with a width of 1.46√$T_N$ keV. The signal region was defined as the interval 225-271 keV, which contains the LZ230616 event. For each neutrino source, the parameters were tuned so that the signal region contained exactly one event, and then they checked how many events are predicted at energies below 225 keV. Standard solar, atmospheric, and relic neutrinos were considered, as well as neutrinos from dark matter annihilation and decay and from primordial black hole evaporation. For new interactions, light scalar and vector mediators were introduced.
Standard astrophysical neutrinos yield only about 2×10⁻⁶ events in the signal region, which is six orders of magnitude less than required. Introducing new scalar or vector mediators that enhance the cross section to obtain one event at 248 keV leads to the appearance of on the order of 10⁵ events in the low-energy bins. This contradicts the LZ observations. For neutrinos from dark matter annihilation, the required annihilation cross section is ⟨σv⟩≳10⁻¹⁸ cm³/s, which is orders of magnitude above existing constraints, and the $R_I$=1 curve lies entirely in the region excluded by the excess of low-energy events. Similarly, for decaying dark matter, the required lifetime is τ_χ≲10¹⁵ s, which is far below established limits. For primordial black holes, obtaining one event requires a fraction $f_{PBH}$≥95 at a mass of 8×10¹⁴ g, which exceeds the total dark matter density, while the low-energy excess reaches 10²³ events for heavier black holes.
This work differs from neighboring studies in that it does not propose a new dark matter model but systematically rules out an entire class of explanations via elastic neutrino scattering. While neighboring papers search for a positive signal, this one shows that elastic neutrino scattering of any origin cannot produce an isolated high-energy event without overfilling the low-energy region. This is the first check of its kind for the LZ230616 event. The result strengthens the case for inelastic mechanisms, such as endothermic or exothermic dark matter scattering, which can create a threshold and localize the signal.
The topic could develop toward a detailed study of inelastic processes involving dark matter, which naturally explain isolated high-energy events. An analysis of neutrino signals accounting for inelastic scattering on nuclei is also possible, though it requires more complex nuclear models. In addition, future LZ data with greater exposure will make it possible to check whether LZ230616 is a statistical fluctuation or the first hint of new physics.
The result is important for interpreting data from liquid xenon dark matter detectors such as LZ, XENONnT, and PandaX-4T. It also places constraints on models with light mediators and on scenarios with neutrinos from dark matter and primordial black holes.
The next step is to check inelastic scattering channels that could reproduce the LZ230616 event without an excess at low energies. It is also important to accumulate more LZ data to refine the statistical significance of the event.
In dark matter physics, the problem of the nature of dark matter particles and their non-gravitational interactions remains unsolved. This work narrows the space of hypotheses by ruling out elastic neutrino scattering as an explanation for a rare high-energy event, thereby pushing toward models with inelastic processes or new particles.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The authors computed the nuclear recoil spectra from coherent elastic neutrino-nucleus scattering on xenon nuclei for a broad class of sources, including both standard and exotic fluxes. They showed that requiring a single event like LZ230616 at 248 keV inevitably produces a huge excess of events at low energies, which contradicts the LZ data. Therefore, elastic neutrino scattering of any origin is ruled out as an explanation for the event.
Where its strength is
The strength of this work lies in systematically closing off an entire class of explanations via elastic neutrino scattering, with explicit treatment of energy resolution and a check against the low-energy excess. This yields a clear negative result that serves as a useful benchmark for future searches.
Where it could go next
Worth trying
Why this may matter
Ruling out elastic neutrino scattering as the cause of LZ230616 matters for correctly interpreting future events in dark matter detectors: if similar single high-energy recoils recur, they will point to new physics beyond the Standard Model, but not to neutrinos.
Nearby works in our archive
The closest work in the archive sits at 0.65 by meaning — the usual level for our corpus.
Obtaining a single event from primordial black holes would require their fraction in dark matter to be $f_{PBH}$≥95, which means there would have to be more black holes than all the dark matter in the Universe. That is physically impossible.