Neutrino NSI in archaeological Pb

Abstract

Dark matter direct detection experiments can observe solar neutrinos via coherent elastic neutrino-nucleus scattering, making it possible to test new physics in the neutrino sector. In this article, we study the sensitivity of RES-NOVA, a novel cryogenic calorimetric experiment employing PbWO$_4$ crystals grown from archaeological lead, to neutrino non-standard interactions (NSI). We perform a sensitivity study for a benchmark setup with a nominal energy threshold of 1 keV and an exposure of 1 ton$\cdot$y, both for a conservative (only heat readout) and ideal (heat and scintillation) background rejection scenario. We find that, in its nominal configuration, RES-NOVA can reach sensitivities to NSI at the level of current global fits. With moderate or significant improvements of the threshold down to 0.5 keV and 0.1 keV, RES-NOVA will be able to achieve sensitivities beyond NSI global fit results, testing new areas of the parameter space in the electron and tau sectors, $\varepsilon_{ee}$, $\varepsilon_{ττ}$, and $\varepsilon_{eτ}$. A similar improvement in sensitivities is expected when instead increasing the exposure to 10 ton$\cdot$y.

Figures (7)

• Figure 1: Schematic view of a single detector unit (left) and the full RES-NOVA detector (right). The setup includes a PbWO$_4$ crystal absorber, a cryogenic light detector and copper mechanical structure.
• Figure 2: Differential solar neutrino fluxes at earth (left) and corresponding induced recoil spectra in PbWO$_4$ (right). The colored lines correspond to individual flux components (see legend). The black line represents the total expected recoil rate.
• Figure 3: The 90% C.L. discovery reach for solar neutrinos via SM CE$\nu$NS, as a function of different energy thresholds and exposures, computed assuming the best (green) and worst (blue) background scenarios for PbWO$_4$ detectors in the RES-NOVA installation. The range of energy thresholds considered corresponds to values that are technologically achievable with cryogenic detectors, as discussed in Ref. Bento:2024zkd. Three representative thresholds are highlighted: 1 keV, adopted as the RES-NOVA benchmark configuration; and 0.5 keV and 0.1 keV, which can be reached by trading target mass for increased detector granularity and readout channel count. The increase in sensitivity in the pessimistic scenario between thresholds of around 0.1 keV and 0.2 keV is due to additional neutrino flux components entering the signal region (cf. right panel of \ref{['fig:nu_sig']}).
• Figure 4: The 90% C.L. sensitivity of the RES-NOVA experiment to NSI with nucleons ($\varphi = 0$) due to nuclear recoils induced via CE$\nu$NS. Shown are the projected constraints for two different representative background configurations: an optimistic scenario (green), corresponding to full e-$\gamma$ background rejection, and a pessimistic scenario (blue), based on no background rejection capability. Both projections are obtained for the same detector exposure and energy threshold of 1 ton$\cdot$yr and 1 keV, respectively. The two configurations illustrate the impact of background control on the sensitivity to NSI in PbWO$_4$ cryogenic detectors. For comparison, we show the $2\sigma$ credible intervals from the NSI global fits in the proton direction, $\varepsilon^p_{\alpha\beta}$, from Ref. Coloma:2019mbs (red), and on the up- and down-quark directions, $\varepsilon^u_{\alpha\beta}$ and $\varepsilon^d_{\alpha\beta}$, from Ref. Coloma:2023ixt (blue).
• Figure 5: The 90% C.L. sensitivity of the RES-NOVA experiment considering an exposure of 1 ton$\cdot$yr and an energy threshold of 0.5 keV. The NSI parameters and the color coding are the same as in \ref{['fig:nsisensitivity_1kev_1ton']}.