Abstract: The recent observation of coherent elastic neutrino-nucleus scattering (CEvNS) with neutrinos from pion decay at rest (N-DAR) sources by the COHERENT Collaboration has raised interest in this process in the search for new physics. Unfortunately, current uncertainties in the determination of nuclear parameters relevant to those processes can hide new physics effects. This is not the case for processes involving lower-energy neutrino sources such as nuclear reactors. Note, however, that a CEvNS measurement with reactor neutrinos depends largely on a (still-missing) precise determination of the quenching factor at very low energies, making its observation more challenging. In the upcoming years, once this signal is confirmed, a combined analysis of N-DAR and reactor CEvNS experiments will be very useful to probe particle and nuclear physics, with a reduced dependence on nuclear uncertainties. In this work, we explore this idea by simultaneously testing the sensitivity of current and future CEvNS experiments to neutrino nonstandard interactions (NSIs) and the neutron root mean square (rms) radius, considering different neutrino sources as well as several detection materials. We show how the interplay between future reactor and accelerator CEvNS experiments can help to get robust constraints on the neutron rms and to break degeneracies between the NSI parameters. Our forecast could be used as a guide to optimize the experimental sensitivity to the parameters under study.

Abstract: The potential for probing extra neutral gauge boson mediators (Z') from low-energy measurements is comprehensively explored. Our study mainly focuses on Z' mediators present in string-inspired E-6 models and left-right symmetry. We estimate the sensitivities of coherent-elastic neutrino-nucleus scattering (CE nu NS) and neutrino-electron scattering experiments. Our results indicate that such low-energy high-intensity measurements can provide a valuable probe, complementary to high-energy collider searches and electroweak precision measurements.

Abstract: Majorana neutrino electromagnetic properties are studied through neutral current coherent neutrinonucleus scattering. We focus on the potential of the recently planned COHERENT experiment at the Spallation Neutron Source to probe muon-neutrino magnetic moments. The resulting sensitivities are determined on the basis of chi(2) analysis employing realistic nuclear structure calculations in the context of the quasiparticle random phase approximation. We find that they can improve existing limits by half an order of magnitude. In addition, we show that these facilities allow for standard model precision tests in the low energy regime, with a competitive determination of the weak mixing angle. Finally, they also offer the capability to probe other electromagnetic neutrino properties, such as the neutrino charge radius. We illustrate our results for various choices of experimental setup and target material.

Abstract: We investigate the impact of a fourth sterile neutrino at reactor and Spallation Neutron Source neutrino detectors. Specifically, we explore the discovery potential of the TEXONO and COHERENT experiments to subleading sterile neutrino effects through the measurement of the coherent elastic neutrino-nucleus scattering event rate. Our dedicated chi(2)-sensitivity analysis employs realistic nuclear structure calculations adequate for high purity sub-keV threshold Germanium detectors.

Abstract: The nature of dark matter is one of the most thrilling riddles for both cosmology and particle physics nowadays. While in the typical models the dark sector is composed only by weakly interacting massive particles, an arguably more natural scenario would include a whole set of gauge interactions which are invisible for the standard model but that are in contact with the dark matter. We present a method to constrain the number of massless gauge bosons and other relativistic particles that might be present in the dark sector using current and future cosmic microwave background data, and provide upper bounds on the size of the dark sector. We use the fact that the dark matter abundance depends on the strength of the interactions with both sectors, which allows one to relate the freeze-out temperature of the dark matter with the temperature of this cosmic background of dark gauge bosons. This relation can then be used to calculate how sizable is the impact of the relativistic dark sector in the number of degrees of freedom of the early Universe, providing an interesting and testable connection between cosmological data and direct/indirect detection experiments. The recent Planck data, in combination with other cosmic microwave background experiments and baryonic acoustic oscillations data, constrains the number of relativistic dark gauge bosons, when the freeze-out temperature of the dark matter is larger than the top mass, to be N less than or similar to 14 for the simplest scenarios, while those limits are slightly relaxed for the combination with the Hubble constant measurements to N less than or similar to 20. Future releases of Planck data are expected to reduce the uncertainty by approximately a factor of 3, which will reduce significantly the parameter space of allowed models.