Exploration of mass splitting and muon/tau mixing parameters for an eV-scale sterile neutrino with IceCube
(2024) Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics — Vol. 858 (2024)
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Lamoureux, Mathieu 
- et. al.
- Abstract
- We present the first three-parameter fit to a 3+1 sterile neutrino model using 7.634 years of data from the IceCube Neutrino Observatory on <math altimg="si1.svg"><msub><mrow><mi>ν</mi></mrow><mrow><mi>μ</mi></mrow></msub><mo linebreak="goodbreak" linebreakstyle="after">+</mo><msub><mrow><mover accent="true"><mrow><mi>ν</mi></mrow><mo>‾</mo></mover></mrow><mrow><mi>μ</mi></mrow></msub></math> charged-current interactions in the energy range 500–9976 GeV. Our analysis is sensitive to the mass-squared splitting between the heaviest and lightest mass state (<math altimg="si2.svg"><mi mathvariant="normal">Δ</mi><msubsup><mrow><mi>m</mi></mrow><mrow><mn>41</mn></mrow><mrow><mn>2</mn></mrow></msubsup></math>), the mixing matrix element connecting muon flavor to the fourth mass state (<math altimg="si11.svg"><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>μ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup></math>), and the element connecting tau flavor to the fourth mass state (<math altimg="si4.svg"><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>τ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup></math>). Predicted propagation effects in matter enhance the signature through a resonance as atmospheric neutrinos from the Northern Hemisphere traverse the Earth to the IceCube detector at the South Pole. The remaining sterile neutrino matrix elements are left fixed, with <math altimg="si5.svg"><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>e</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>0</mn></math> and <math altimg="si6.svg"><msub><mrow><mi>δ</mi></mrow><mrow><mn>14</mn></mrow></msub><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>0</mn></math>, as they have a negligible effect, and <math altimg="si7.svg"><msub><mrow><mi>δ</mi></mrow><mrow><mn>24</mn></mrow></msub><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mi>π</mi></math> is set to give the most conservative limits. The result is consistent with the no-sterile neutrino hypothesis with a probability of 4.3%. Profiling the likelihood of each parameter yields the 90% confidence levels: <math altimg="si8.svg"><mn>2.4</mn><mspace width="0.2em"/><msup><mrow><mi mathvariant="normal">eV</mi></mrow><mrow><mn>2</mn></mrow></msup><mo linebreak="goodbreak" linebreakstyle="after"><</mo><mi mathvariant="normal">Δ</mi><msubsup><mrow><mi>m</mi></mrow><mrow><mn>41</mn></mrow><mrow><mn>2</mn></mrow></msubsup><mo linebreak="goodbreak" linebreakstyle="after"><</mo><mn>9.6</mn><mspace width="0.2em"/><msup><mrow><mi mathvariant="normal">eV</mi></mrow><mrow><mn>2</mn></mrow></msup></math>, <math altimg="si9.svg"><mn>0.0081</mn><mo linebreak="goodbreak" linebreakstyle="after"><</mo><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>μ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup><mo linebreak="goodbreak" linebreakstyle="after"><</mo><mn>0.10</mn></math>, and <math altimg="si10.svg"><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>τ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup><mo linebreak="goodbreak" linebreakstyle="after"><</mo><mn>0.035</mn></math>, which narrows the allowed parameter-space for <math altimg="si4.svg"><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>τ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup></math>. However, the primary result of this analysis is the first map of the 3+1 parameter space exploring the interdependence of <math altimg="si2.svg"><mi mathvariant="normal">Δ</mi><msubsup><mrow><mi>m</mi></mrow><mrow><mn>41</mn></mrow><mrow><mn>2</mn></mrow></msubsup></math>, <math altimg="si11.svg"><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>μ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup></math>, and <math altimg="si4.svg"><mo stretchy="false">|</mo><msub><mrow><mi>U</mi></mrow><mrow><mi>τ</mi><mn>4</mn></mrow></msub><msup><mrow><mo stretchy="false">|</mo></mrow><mrow><mn>2</mn></mrow></msup></math>.
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Citations
de Wasseige, G., Genton, E., Kruiswijk, K., Lamoureux, M., Lazar, J., Raab, C., Myhr, P., Vereecken, M., IceCube, & et al. (2024). Exploration of mass splitting and muon/tau mixing parameters for an eV-scale sterile neutrino with IceCube. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 858. https://doi.org/10.1016/j.physletb.2024.139077 (Original work published 2024)