Solar neutrino probes of light new physics: Updated limits from LUX-ZEPLIN experiment

The recent low-energy electron recoil (ER) results reported by the LUX-ZEPLIN (LZ) experiment have established the most stringent constraints to date on new physics scenarios, specifically for solar axion-like particles with keV-scale masses and mirror dark matter. Motivated by this enhanced sensitivity and the resulting restrictive limits, our present work focuses on probing light mediator models via elastic neutrino-electron scattering induced by solar neutrinos. We specifically consider two broad classes of new physics scenarios; (i) universal light mediator models consistent with Lorentz invariance, including scalar, vector, and tensor interactions, and (ii) anomaly-free leptophilic <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>U</a:mi> <a:mo stretchy="false">(</a:mo> <a:mn>1</a:mn> <a:msup> <a:mo stretchy="false">)</a:mo> <a:mo>′</a:mo> </a:msup> </a:math> gauge extensions featuring a new vector mediator associated with the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msub> <e:mi>L</e:mi> <e:mi>e</e:mi> </e:msub> <e:mo>−</e:mo> <e:msub> <e:mi>L</e:mi> <e:mi>μ</e:mi> </e:msub> </e:math> , <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:msub> <g:mi>L</g:mi> <g:mi>e</g:mi> </g:msub> <g:mo>−</g:mo> <g:msub> <g:mi>L</g:mi> <g:mi>τ</g:mi> </g:msub> </g:math> , <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:msub> <i:mi>L</i:mi> <i:mi>μ</i:mi> </i:msub> <i:mo>−</i:mo> <i:msub> <i:mi>L</i:mi> <i:mi>τ</i:mi> </i:msub> </i:math> , and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msub> <k:mi>L</k:mi> <k:mi>e</k:mi> </k:msub> <k:mo>+</k:mo> <k:mn>2</k:mn> <k:msub> <k:mi>L</k:mi> <k:mi>μ</k:mi> </k:msub> <k:mo>+</k:mo> <k:mn>2</k:mn> <k:msub> <k:mi>L</k:mi> <k:mi>τ</k:mi> </k:msub> </k:math> symmetries. By incorporating contributions from these interactions into the neutrino-electron scattering cross section and utilizing the most precise solar neutrino flux predictions, we analyze the latest LZ ER datasets. We report novel constraints on the coupling-mass parameter space for these models. Furthermore, we contextualize our findings by comparing them with established bounds from various laboratory, cosmological, and astrophysical sources. Our analysis demonstrates that LZ data provide significantly improved limits in previously unconstrained regions of the parameter space.