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The next generation of neutrinoless double beta decay search experiments aims to reach sensitivities to this half-life of the process up to 1028 years. This will require tonne scale detectors with almost no background in their region of interest, which represents a large improvement with respect to current technologies. With this scenario, the NEXT collaboration presents two parallel developments: NEXT-High Definition and NEXT-Barium atOm Light Detection. The first is based on the incremental improvement of the current pressure gas xenon technology, and the second is based on the use of a barium tagging technology.

A bstract The European Spallation Source (ESS), presently well on its way to completion, will soon provide the most intense neutron beams for multi-disciplinary science. Fortuitously, it will also generate the largest pulsed neutrino flux suitable for the detection of Coherent Elastic Neutrino-Nucleus Scattering (CE ν NS), a process recently measured for the first time at ORNL’s Spallation Neutron Source. We describe innovative detector technologies maximally able to profit from the order-of-magnitude increase in neutrino flux provided by the ESS, along with their sensitivity to a rich particle physics phenomenology accessible through high-statistics, precision CE ν NS measurements.

A unique feature of gas xenon electroluminescent time projection chambers (GXeEL TPCs) in ββ0ν searches is their ability to reconstruct event topology, in particular to distinguish “single-electron” from “double-electron” tracks, the latter being the signature of a ββ0ν decay near the decay endpoint Qββ . Together with excellent energy resolution and the t 0 provided by primary scintillation, this topological information is key to suppressing backgrounds. Preserving EL, however, requires operation in pure xenon (with helium as the only benign additive), where electron diffusion is large. Consequently, reconstructed track fidelity is limited by diffusion and intrinsic EL blurring. We propose augmenting the detector with the ability to image not only the electron track but also the corresponding mirror ion track. Introducing trace amounts of NH3 ( ∼ 100 ppb) converts primary xenon ions into ammonium ions, NH4+ , via a fast two-step ion–molecule process involving charge transfer followed by proton transfer, while leaving EL unaffected. Electrons drift rapidly to the anode, producing the standard EL image, whereas NH4+ ions drift slowly toward the cathode, allowing time to determine the event energy and barycenter. For events in the region of interest, an ion sensor near the cathode at the projected barycenter captures the ions. Laser interrogation of the sensor’s molecular layer then reveals an ion-track image with sub-millimeter diffusion and no EL-induced smearing. Combined electron–ion imaging strengthens topological discrimination, improving background rejection by about an order of magnitude and significantly extending the discovery potential of GXeEL TPCs for very long ββ0ν lifetimes.

A bstract The Japan Proton Accelerator Research Complex (J-PARC) currently delivers a 1 MW, 3 GeV proton beam to the Materials and Life Science Experimental Facility (MLF). Power is expected to increase to 1.3 MW, driven by the needs of Hyper-Kamiokande. As a result, the MLF presently provides the highest neutron yield of any spallation source, while potentially holding the best current and foreseeable conditions for Coherent Elastic Neutrino-Nucleus Scattering (CE ν NS) experimentation. We explore this potential, using as examples detector technologies presently funded for construction and under development. We quantify their sensitivity to a rich variety of particle physics scenarios, finding that very-high-statistics CE ν NS measurements with significant sensitivity to relevant scenarios are feasible at this facility within the next few years.

A novel experimental setup to measure deviations from the 1 / r 2 distance dependence of Newtonian gravity was proposed in Donini and Marimón (Eur Phys J C 76:696, 2016). The underlying theoretical idea was to study the orbits of a microscopically-sized planetary system composed of a “Satellite”, with mass m S ∼ O ( 10 - 9 ) g, and a “Planet”, with mass M P ∼ O ( 10 - 5 )  g at an initial distance of hundreds of microns. The detection of precession of the orbit in this system would be an unambiguous indication of a central potential with terms that scale with the distance differently from 1/ r . This is a huge advantage with respect to the measurement of the absolute strength of the attraction between two bodies, as most electrically-induced background potentials do indeed scale as 1/ r . Detection of orbit precession is unaffected by these effects, allowing for better sensitivities. In Baeza-Ballesteros et al. (Eur Phys J C 82:154, 2022), the impact of other subleading backgrounds that may induce orbit precession, such as, e.g., the electrical Casimir force or general relativity, was studied in detail. It was found that the proposed setup could test Yukawa-like corrections, α × exp ( - r / λ ) , to the 1/ r potential with couplings as low as α ∼ 10 - 2 for distances as small as λ ∼ 10 μ m, improving by roughly an order of magnitude present bounds. In this paper, we start to move from a theoretical study of the proposal to a more realistic implementation of the experimental setup. As a first step, we study the impact of air viscosity on the proposed setup and see how the setup should be modified in order to preserve the theoretical sensitivity achieved in Donini and Marimón (2016) and Baeza-Ballesteros et al. (2022).

A novel experimental setup to measure deviations from the [Formula omitted] distance dependence of Newtonian gravity was proposed in Donini and Marimón (Eur Phys J C 76:696, 2016). The underlying theoretical idea was to study the orbits of a microscopically-sized planetary system composed of a \"Satellite\", with mass [Formula omitted] g, and a \"Planet\", with mass [Formula omitted] g at an initial distance of hundreds of microns. The detection of precession of the orbit in this system would be an unambiguous indication of a central potential with terms that scale with the distance differently from 1/r. This is a huge advantage with respect to the measurement of the absolute strength of the attraction between two bodies, as most electrically-induced background potentials do indeed scale as 1/r. Detection of orbit precession is unaffected by these effects, allowing for better sensitivities. In Baeza-Ballesteros et al. (Eur Phys J C 82:154, 2022), the impact of other subleading backgrounds that may induce orbit precession, such as, e.g., the electrical Casimir force or general relativity, was studied in detail. It was found that the proposed setup could test Yukawa-like corrections, [Formula omitted] to the 1/r potential with couplings as low as [Formula omitted] for distances as small as [Formula omitted] [Formula omitted]m, improving by roughly an order of magnitude present bounds. In this paper, we start to move from a theoretical study of the proposal to a more realistic implementation of the experimental setup. As a first step, we study the impact of air viscosity on the proposed setup and see how the setup should be modified in order to preserve the theoretical sensitivity achieved in Donini and Marimón (2016) and Baeza-Ballesteros et al. (2022).

A unique feature of gas xenon electroluminescent time projection chambers (GXeEL TPCs) in β β 0 ν searches is their ability to reconstruct event topology, in particular to distinguish “single-electron” from “double-electron” tracks, the latter being the signature of a β β 0 ν decay near the decay endpoint Q β β . Together with excellent energy resolution and the t 0 provided by primary scintillation, this topological information is key to suppressing backgrounds. Preserving EL, however, requires operation in pure xenon (with helium as the only benign additive), where electron diffusion is large. Consequently, reconstructed track fidelity is limited by diffusion and intrinsic EL blurring. We propose augmenting the detector with the ability to image not only the electron track but also the corresponding mirror ion track. Introducing trace amounts of NH 3 ( ∼ 100 ppb) converts primary xenon ions into ammonium ions, NH 4 + , via a fast two-step ion–molecule process involving charge transfer followed by proton transfer, while leaving EL unaffected. Electrons drift rapidly to the anode, producing the standard EL image, whereas NH 4 + ions drift slowly toward the cathode, allowing time to determine the event energy and barycenter. For events in the region of interest, an ion sensor near the cathode at the projected barycenter captures the ions. Laser interrogation of the sensor’s molecular layer then reveals an ion-track image with sub-millimeter diffusion and no EL-induced smearing. Combined electron–ion imaging strengthens topological discrimination, improving background rejection by about an order of magnitude and significantly extending the discovery potential of GXeEL TPCs for very long β β 0 ν lifetimes.

NEXT is a new experiment to search for neutrinoless double beta decay processes that will start operation at the LSC laboratory (Canfranc, Spain) in 2013. The apparatus is a high pressure gas xenon chamber (HPGXe) filled with 100-150 kg of gas Xenon enriched at 90% in the 136Xe isotope. NEXT proposes a novel detection technique called SOFT (Separated Optimized Function TPC) which optimizes both the energy resolution and the measurement of the topological signature of the event. This results in a powerful background rejection, which, combined with a carefully screened radiopure detector will allow NEXT to be competitive with existing proposals for next-generation neutrinoless double-beta decay experiments. First prototypes have been operating successfully in different laboratories. First results with large-scale prototypes measure a resolution of 1% FWHM at the 137Cs photopeak. This extrapolates to a resolution better than 0.5% FWHM at Qββ.

The recent detection of the coherent elastic neutrino-nucleus scattering ( CEυNS ) opens the possibility to use neutrinos to explore physics beyond standard model with small size detectors. However, the CEυNS process generates signals at the few keV level, requiring of very sensitive detecting technologies for its detection. The European Spallation Source (ESS) has been identified as an optimal source of low energy neutrinos offering an opportunity for a definitive exploration of all phenomenological applications of CEυNS . In this project I propose to apply the high pressure gas TPC technology to the detection of the CEυNS process at the ESS. This will require the development of very low-energy detectors and to improve the current knowledge of the quenching factor for nuclear recoils in gas at keV energies. The major goal of this project is to build a 20 kg xenon gaseous detector and operate it at the ESS, such detector will provide more than 7,000 CEυNS events per year, overtaking the sensitivities of much larger detectors in current spallations sources.

A simple hole-type secondary scintillation structure (2 mm-hole, 5 mm-pitch, 5 mm-thickness) is introduced and its operation demonstrated in pure xenon in the pressure range 2-10 bar. The new device, characteristically translucent, has been manufactured through a collaboration between IGFAE and the CERN workshop, and relies entirely on radiopure materials (acrylic and copper), being extremely rugged in the presence of sparks, mechanically robust, and easily scalable, yet made through a relatively simple process. With an overall figure (at 10 bar) characterized by an energy resolution of 18.9%(FWHM) for 55Fe x-rays, an optical gain of mγ= 500 ph/e, and a stable operation at reduced fields more than twice those of some of the presently running experiments (EEL= 3 kV/cm/bar), this family of structures seems to show great promise for electroluminescence readouts on large scale detectors. As argued below, further improvements have the potential of bringing the energy resolution close to the Fano factor and increasing the optical gain.