Precision ${\overline{\nu }}_e$-electron scattering measurements with IsoDAR to search for new physics

IsoDAR provides a pure and intense ${\overline{\nu }}_e$ source with an average energy of 6.5 MeV produced through ${}^8\mathrm{Li}$ $\beta$ decay. This source can be paired with a large scintillator detector, such as KamLAND, to produce a sample of ${\overline{\nu }}_e$-electron scatters that is more than 5 times larger than what has been collected before. Such a sample would allow for a 3.2% measurement of ${\sin }^2{\theta }_W$ and a sensitive search for nonstandard interactions.

Figure 1

The number of signal and background events as a function of visible energy. The thick solid line shows the ES signal events, the dashed line shows the nonbeam background, and the thin solid line with x’s shows the misidentified IBD beam background. The distributions include an energy smearing of $\delta E_{\mathrm{vis}}=0.065·\sqrt{E_{\mathrm{vis}}\text{(MeV)}}$.

Figure 2

IsoDAR’s sensitivity to $g_V$ and $g_A$ along with allowed regions from other neutrino scattering experiments and the electroweak global best fit point taken from Ref. [42]. The IsoDAR, Liquid Scintillator Neutrino Detector, and TEXONO contours are all at $1\sigma$ and are all plotted in terms of $g_{V,A}^{{\nu }_{\mu }e}=g_{V,A}^{{\nu }_{e}e}-1$ to compare with ${\nu }_{\mu }$ scattering data. The ${\nu }_{\mu }e/{\overline{\nu }}_{\mu }e$ contour is at 90% C.L.

Figure 3

(Top) IsoDAR’s sensitivity to ${\epsilon }_{ee}^{eL}$ and ${\epsilon }_{ee}^{eR}$. The current global allowed region based on Ref. [43] is also shown. (Bottom) A zoomed-in version of the top plot emphasizing the region near ${\epsilon }_{ee}^{eL}$ and ${\epsilon }_{ee}^{eR}\sim 0$ is shown.