Atmospheric neutrino up-scattering explanation of LZ 2026 excess
4 affiliations
- 1Key Laboratory for Particle Astrophysics and Cosmology (MOE) &
- 2State Key Laboratory of Dark Matter Physics , Tsung-Dao Lee Institute & School of Physics and Astronomy , Shanghai Jiao Tong University , Shanghai 200240 , China
- 3Department of Physics , Indian Institute of Science Education and Research -Bhopal , Bhopal Bypass Road , Bhauri , Bhopal 462066 , India
- 4Shanghai Key Laboratory for Particle Physics and Cosmology , Shanghai Jiao Tong University , Shanghai 200240 , China
Abstract
The recent observation of an isolated nuclear recoil at 248± 23± 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 mχ. 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 (𝒩), ν𝒩→ χ𝒩, 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 mϕ that couples to the ν-χ pair with strength yχ and to up quarks with strength yu. For example, mχ≃ 1.13~GeV, mϕ≃ 494~MeV and √(yχyu) ≃ 0.33 can account for the observed event while remaining allowed by other existing constraints.
Related
- A scalar-extended U(1)Lμ−Lτ explanation of the LUX-ZEPLIN 248 keV excess
- Atmospheric Neutrino Oscillations: the Full Picture
- Evidence for Normal Neutrino Ordering with Combined Atmospheric Neutrino Experiments
- Characterizing Single-Signal Events from Atmospheric-Neutrino Neutral-Current Interactions in Large Liquid Scintillator Detectors
- Comment on arXiv:2608.29450: "First Measurement of Solar Neutrinos through Elastic Neutrino-Electron Scattering at the keV Scale"
BibTeX
@misc{jeesun2026atmospheric,
title = {{Atmospheric neutrino up-scattering explanation of LZ 2026 excess}},
author = {Sk Jeesun and Anirban Majumdar},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.04185},
eprint = {2609.04185},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04185},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Atmospheric neutrino up-scattering explanation of LZ 2026 excess
AU - Sk Jeesun
AU - Anirban Majumdar
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.04185
UR - https://arxiv.org/abs/2609.04185
AB - The recent observation of an isolated nuclear recoil at 248± 23± 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 (𝒩), ν𝒩→ χ𝒩, 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≃ 1.13~GeV, m_ϕ≃ 494~MeV and √(y_χy_u) ≃ 0.33 can account for the observed event while remaining allowed by other existing constraints.
SN - 2331-8422
ER -