Abstract:The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross-section is the largest by far of all low-energy neutrino couplings. This mode of interaction provides new opportunities to study neutrino properties, and leads to a miniaturization of detector size, with potential technological applications. We observe this process at a 6.7-sigma confidence level, using a low-background, 14.6-kg CsI [Na] scintillator exposed to the neutrino emissions from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the Standard Model for this process, are observed in high signal-to-background conditions. Improved constraints on non-standard neutrino interactions with quarks are derived from this initial dataset.The characteristic most often associated with neutrinos is a very small probability of interaction with other forms of matter, allowing them to traverse astronomical objects while undergoing no energy loss. As a result, large targets (tons to tens of kilotons) are used for their detection. The discovery of a weak neutral current in neutrino interactions (1) implied that neutrinos were capable of coupling to quarks through the exchange of neutral Z bosons. Soon thereafter it was suggested that this mechanism should also lead to coherent interactions between neutrinos and all nucleons present in an atomic nucleus (2). This possibility would exist only as long as the momentum exchanged remained significantly smaller than the inverse of the nuclear size ( Fig. 1A), effectively restricting the process to neutrino energies below a few tens of MeV.The enhancement to the probability of interaction (scattering cross-section) would however be very large when compared to interactions with isolated nucleons, approximately scaling with the square of the number of neutrons in the nucleus (2, 3). For heavy nuclei and sufficiently intense neutrino sources, this can lead to a dramatic reduction in detector mass, down to a few kilograms.Coherent elastic neutrino-nucleus scattering (CEnNS) has evaded experimental demonstration for forty-three years following its first theoretical description. This is somewhat surprising, in view of the magnitude of its expected cross-section relative to other tried-andtested neutrino couplings (Fig. 1B), and of the availability of suitable neutrino sources: solar, atmospheric and terrestrial, supernova bursts, nuclear reactors, spallation facilities, and certain radioisotopes (3). This delay stems from the difficulty in detecting the low-energy (few keV) nuclear recoil produced as the single outcome of the interaction. Compared to a minimum ionizing particle of the same energy, a recoiling nucleus has a diminished ability to generate measurable scintillation or ionization in common radiation detector materials. This is exacerbated by a trade-off between the enhancement to the CEnNS cross-section brought about by a large nuclear mass, and the smaller maxi...

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Coherent elastic neutrino-nucleus scattering (CEvNS) is calculated to be the dominant neutrino scattering channel for neutrinos of energy E ν < 100 MeV. We report a limit for this process from data collected in an engineering run of the 29 kg CENNS-10 liquid argon detector located 27.5 m from the pion decay-at-rest neutrino source at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) with 4.2 × 10 22 protons on target. The dataset provided constraints on beam-related backgrounds critical for future measurements and yielded < 7.4 candidate CEvNS events which implies a cross section for the

The COHERENT experiment is well poised to test sub-GeV dark matter models using detectors sensitive to coherent elastic neutrino-nucleus scattering (CEvNS) in the π þ decay-at-rest (π-DAR) neutrino beam produced by the Spallation Neutron Source. We show a planned 750-kg single-phase liquid argon scintillation detector would place leading limits on scalar light dark matter models for dark matter particles produced through vector and leptophobic portals in the absence of other effects beyond the standard model. The characteristic timing profile of a π-DAR beam allows a unique opportunity for constraining systematic

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We have in mind a register of qubits for an quantum information system, and consider its decoherence in an idealized but typical situation. Spontaneous decay and other couplings to the far environment considered as the world outside the quantum apparatus will be neglected, while couplings to quantum states within the apparatus, i.e. to a near environment are assumed to dominate. Thus the central system couples to the near environment which in turn couples to a far environment. Considering that the dynamics in the near environment is not sufficiently well known or controllable, we shall use random matrix methods to obtain analytic results. We consider a simplified situation where the central system suffers weak dephasing from the near environment, which in turn is coupled randomly to the far environment. We find the anti-intuitive result that increasing the coupling between near and far environment actually protects the central qubit. In many quantum optics experiments and quantum information devices we find the following situation: The central system, well protected from simple decoherence processes such as spontaneous emission or direct coupling to a structureless heat bath, still suffers some decoherence from the coupling to the quantum part of the apparatus. We will call the former the far environment and the latter the near environment. In such a tripartite system without direct coupling between central system and far environment, we find that increasing the coupling of the near to the far environment can protect the central system against decoherence. In the setting of the Haroche experiment [1, 2] the late M. C. Nemes discussed this somewhat anti-intuitive fact with one of the authors [3] twelve years ago. More recently, additional numerical evidence has appeared [4], some of which were master thesis related to the present work [5][6][7]. Finally, it was shown in Ref.[8] that a protected subspace can appear in a strong coupling limit.We now wish to construct a model that allows some analytical treatment and simultaneously has some claim to universality. Indeed the intermediate environment in a quantum information system typically consists of quantum states that are not used but are unavoidably present. While ordered and systematic couplings can be minimized with good technology, it is plausible that the uncontrolled remanent will have a random structure. Considering its minimum information character [9], we use random matrix theory (RMT) of decoherence [10][11][12]. There are several examples, which involve chaotic or irregular dynamics explicitly: e.g. the coupling of two-level atoms to quantum systems with classical chaotic analog [13,14], and the experimental realization of quantum chaos in a chain of three level atoms in [15]. The recent advances in the design and control of chains of individual ions [16], may lead to similar experimental systems. We simplify the picture by limiting the coupling between central system and near environment to dephasing [17,18], and assume the coupling between near and f...

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