Year: 2026
Type: preprint
Abstract: The recent observation of an isolated nuclear recoil at $248\pm 23\pm 23$ keV energy by the LUX-ZEPLIN (LZ) experiment has motivated the community to look for a new physics explanation, as the Standard Model background estimation fails to accommodate it. Most of the existing literature hitherto considers a galactic halo dark matter with a heavier partner. In this work, we traverse the alternate route of atmospheric neutrino ($ν$) up-scattering, thus producing a massive beyond standard model (BSM) particle $χ$ with mass $m_χ$. The kinematic requirement of such a scattering demands a higher energy of the incoming neutrinos than elastic scattering, explaining the absence of excess events from solar $ν$ scattering. However, for high energy neutrinos in the tail of the atmospheric neutrino flux, the kinematic threshold no longer prevents events at low recoil energies. To avoid an excess of such events, we consider a momentum dependent operator, which suppresses the event rate at low recoil energies and allows a single event in the high recoil energy window. Such up-scattering on nuclei ($\mathcal{N}$), $ν\mathcal{N}\to χ\mathcal{N}$, can be naturally realized in sterile neutrino models, though we keep our analysis generic without specifying $χ$. We identify the region of parameter space that can produce such an isolated event, assuming a pseudoscalar mediator with mass $m_ϕ$ that couples to the $ν$-$χ$ pair with strength $y_χ$ and to up quarks with strength $y_u$. For example, $m_χ\simeq 1.13$~GeV, $m_ϕ\simeq 494$~MeV and $\sqrt{y_χy_u} \simeq 0.33$ can account for the observed event while remaining allowed by other existing constraints.
Source: arXiv (Cornell University)
Authors: Jeesun, Sk, Majumdar, Anirban
Language: English
Topic: Neutrino Physics Research
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G4129341838, G8924575279
OpenAlex ID: W7208772671