Physics reach of CERN-based SuperBeam neutrino oscillation experiments

We compare the physics potential of two representative options for a SuperBeam in Europe, studying the achievable precision at 1\sigma with which the CP violation phase (\delta) could be measured, as well as the mass hierarchy and CP violation discovery potentials. The first setup corresponds to a high energy beam aiming from CERN to a 100 kt liquid argon detector placed at the Pyh\"asalmi mine (2300 km), one of the LAGUNA candidate sites. The second setup corresponds to a much lower energy beam, aiming from CERN to a 500 kt water \v{C}erenkov detector placed at the Gran Sasso underground laboratory (730 km). This second option is also studied for a baseline of 650 km, corresponding to the LAGUNA candidate sites of Umbria and the Canfranc underground laboratory. All results are presented also for scenarios with statistics lowered by factors of 2, 4, 8 and 16 to study the possible reductions of flux, detector mass or running time allowed by the large value of \theta_{13} recently measured.Comment: 15 pages, 4 figure

Search for Neutrinos from Annihilation of Captured Low-Mass Dark Matter Particles in the Sun by Super-Kamiokande

Artículo escrito por muchos autores, sólo se referencian el primero, los autores que firman como Universidad Autónoma de Madrid y el grupo de colaboración en el caso de que aparezca en el artículoSuper-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/c2-200-GeV/c2) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV/c2 (at 10 GeV/c2, 1.49×10-39 cm2 for χχ→bb¯ and 1.31×10-40 cm2 for χχ→τ+τ- annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV/c2 mass rangeThe Super-Kamiokande experiment was built and has been operated with funding from the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundatio

Test of Lorentz invariance with atmospheric neutrinos

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMA search for neutrino oscillations induced by Lorentz violation has been performed using 4,438 live-days of Super-Kamiokande atmospheric neutrino data. The Lorentz violation is included in addition to standard three-flavor oscillations using the nonperturbative standard model extension (SME), allowing the use of the full range of neutrino path lengths, ranging from 15 to 12,800 km, and energies ranging from 100 MeV to more than 100 TeV in the search. No evidence of Lorentz violation was observed, so limits are set on the renormalizable isotropic SME coefficients in the eμ, μτ, and eτ sectors, improving the existing limits by up to 7 orders of magnitude and setting limits for the first time in the neutrino μτ sector of the SMEWe would like to thank A. Kostelecky for his advice and support and we are grateful to J. S. Diaz for working closely with us to calculate and implement the Lorentz-violating oscillation probabilities. The authors gratefully acknowledge the cooperation of the Kamioka Mining and Smelting Company. Super-K has been built and operated from funds provided by the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundation. This work was partially supported by the Research Foundation of Korea (BK21 and KNRC), the Korean Ministry of Science and Technology, the National Science Foundation of China, the European Union FP7 (DS laguna-lbno PN- 284518 and ITN invisibles GA-2011-289442), the National Science and Engineering Research Council (NSERC) of Canada, and the Scinet and Westgrid consortia of Compute Canad

Search for dinucleon decay into pions at Super-Kamiokande

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMA search for dinucleon decay into pions with the Super-Kamiokande detector has been performed with an exposure of 282.1 kiloton-years. Dinucleon decay is a process that violates baryon number by two units. We present the first search for dinucleon decay to pions in a large water-Cherenkov detector. The modes O16(pp)→C14π+π+, O16(pn)→N14π+π0, and O16(nn)→O14π0π0 are investigated. No significant excess in the Super-Kamiokande data has been found, so a lower limit on the lifetime of the process per oxygen nucleus is determined. These limits are τpp→π+π+>7.22×1031 years, τpn→π+π0>1.70×1032 years, and τnn→π0π0>4.04×1032 years. The lower limits on each mode are about 2 orders of magnitude better than previous limits from searches for dinucleon decay in ironWe gratefully acknowledge the cooperation of the Kamioka Mining and Smelting Company. The Super- Kamiokande experiment has been built and operated from funding by the Japanese Ministry of Education, Culture, Sports, Science and Technology, the United States Department of Energy, and the U.S. National Science Foundation. This work was partially supported by the Research Foundation of Korea (BK21 and KNRC), the Korean Ministry of Science and Technology, the National Science Foundation of China, the European Union FP7 (DS laguna-lbno PN-284518 and ITN invisibles GA-2011- 289442), the National Science and Engineering Research Council (NSERC) of Canada, and the Scinet and West-grid consortia of Compute Canad

Limits on sterile neutrino mixing using atmospheric neutrinos in Super-Kamiokande

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMWe present limits on sterile neutrino mixing using 4,438 live-days of atmospheric neutrino data from the Super-Kamiokande experiment. We search for fast oscillations driven by an eV2-scale mass splitting and for oscillations into sterile neutrinos instead of tau neutrinos at the atmospheric mass splitting. When performing both of these searches we assume that the sterile mass splitting is large, allowing sin2(Δm2L/4E) to be approximated as 0.5, and we assume that there is no mixing between electron neutrinos and sterile neutrinos (|Ue4|2=0). No evidence of sterile oscillations is seen and we limit |Uμ4|2 to less than 0.041 and |Uτ4|2 to less than 0.18 for Δm2>0.1eV2 at the 90% C.L. in a 3+1 framework. The approximations that can be made with atmospheric neutrinos allow these limits to be easily applied to 3+N models, and we provide our results in a generic format to allow comparisons with other sterile neutrino modelsThe authors gratefully acknowledge the cooperation of the Kamioka Mining and Smelting Company. Super-K has been built and operated from funds provided by the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundation. This work was partially supported by the Research Foundation of Korea (BK21 and KNRC), the Korean Ministry of Science and Technology, the National Science Foundation of China, the European Union FP7 (DS laguna-lbno PN- 284518 and ITN invisibles GA-2011-289442) the National Science and Engineering Research Council (NSERC) of Canada, and the Scinet and Westgrid consortia of Compute Canad

Search for neutrinos in Super-Kamiokande associated with gravitational-wave events GW150914 and GW151226

Astrophysical Journal Letters 830.1 (2016): L11 reproduced by permission of the AASWe report the results from a search in Super-Kamiokande for neutrino signals coincident with the first detected gravitational-wave events, GW150914 and GW151226, as well as LVT151012, using a neutrino energy range from 3.5 MeV to 100 PeV. We searched for coincident neutrino events within a time window of ±500 s around the gravitational-wave detection time. Four neutrino candidates are found for GW150914, and no candidates are found for GW151226. The remaining neutrino candidates are consistent with the expected background events. We calculated the 90% confidence level upper limits on the combined neutrino fluence for both gravitational-wave events, which depends on event energy and topologies. Considering the upward-going muon data set (1.6 GeV-100 PeV), the neutrino fluence limit for each gravitational-wave event is 14-37 (19-50) cm-2 for muon neutrinos (muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined fluence limits for both gravitational-wave events range from 2.4 ×104 to 7.0 ×109 cm-2The Super-Kamiokande experiment has been built and operated from funding by the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundation. Some of us have been supported by funds from the Korean Research Foundation (BK21 and KNRC), the National Research Foundation of Korea (NRF-20110024009), the European Union (H2020 RISE-GA641540-SKPLUS), the Japan Society for the Promotion of Science, the National Natural Science Foundation of China under grant No. 11235006, and the Scinet and Westgrid consortia of Compute Canad

Search for Nucleon and Dinucleon Decays with an Invisible Particle and a Charged Lepton in the Final State at the Super-Kamiokande Experiment

Artículo escrito por muchos autores, sólo se referencian el primero, los autores que firman como Universidad Autónoma de Madrid y el grupo de colaboración en el caso de que aparezca en el artículoSearch results for nucleon decays p→e+X, p→μ+X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decays np→e+ν, np→μ+ν, and np→τ+ν in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of 273.4 kton·yr, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of τp→e+X>7.9×1032yr, τp→μ+X>4.1×1032yr, τn→νγ>5.5×1032yr, τnp→e+ν>2.6×1032yr, τnp→μ+ν>2.2×1032yr, and τnp→τ+ν>2.9×1031yr at a 90% confidence level are obtained. Some of these searches are novelThe Super- Kamiokande experiment was built and has been operated with funding from the Japanese Ministry of Education, Culture, Sports, Science and Technology, the U.S. Department of Energy, and the U.S. National Science Foundatio

Gadolinium concentration measurement with an atomic absorption spectrophotometer

Because gadolinium (Gd) has the highest thermal neutron capture cross section, resulting in an 8 MeV gamma cascade upon capture, it has been proposed for dissolution in water Cherenkov detectors to achieve efficient neutron tagging capabilities. While metallic Gd is insoluble in water, several compounds are very easy to dissolve. Gadolinium sulfate, Gd$_2$(SO$_4$)$_3$, has been thoroughly tested and proposed as the best candidate. Accurate measurement of its concentration, free of doubt from impurities in water, is crucial. An atomic absorption spectrophotometer (AAS) is a device that suits this purpose and is widely used to measure the concentration of many elements. In this study, we describe three different approaches to measure Gd sulfate concentrations in water using an AAS: doping samples with potassium and lanthanum, and employing tantalum and tungsten platforms

Gadolinium Concentration Measurement with an Atomic Absorption Spectrophotometer

Because gadolinium (Gd) has the highest thermal neutron capture cross section, resulting in an 8 MeV gamma cascade upon capture, it has been proposed for dissolution in water Cherenkov detectors to achieve efficient neutron tagging capabilities. Whereas metallic Gd is insoluble in water, several compounds are very easy to dissolve. Gadolinium sulfate, Gd2(SO4)3, has been thoroughly tested and proposed as the best candidate. Accurate measurement of its concentration, free of doubt from impurities in water, is crucial. An atomic absorption spectrophotometer (AAS) is a device that suits this purpose and is widely used to measure the concentration of many elements. In this study, we describe three different approaches to measure Gd sulfate concentrations in water using an AAS: doping samples with potassium and lanthanum, and employing tantalum and tungsten platformsWe would like to thank the Super-Kamiokande collaboration and very specially the EGADS group for their help in conducting this study. We also would like to thank the technicians of Kavli-IPMU, Nakagawa Hitoshi and Kanazawa Motoichi, for their help and support. We gratefully acknowledge the cooperation of the Kamioka Mining and Smelting Company. L.M. has been partially supported by funds from the Ministry of Education, Culture, Sports, Science and Technology (Grant-in-Aid for Young Scientists No. 15K17638). L.L. acknowledges the support from the Spanish Ministry of Science, Universities and Innovation (grant PID2021-124050NB-C31) and the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement no. 872549 H2020-MSCA-RISE-2019 SK2H

Evaluation of gadolinium’s action on water Cherenkov detector systems with EGADS

Artículo escrito por un elevado número de autores, sólo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiera, y los autores pertenecientes a la UAMUsed for both proton decay searches and neutrino physics, large water Cherenkov (WC) detectors have been very successful tools in particle physics. They are notable for their large masses and charged particle detection capabilities. While current WC detectors reconstruct charged particle tracks over a wide energy range, they cannot efficiently detect neutrons. Gadolinium (Gd) has the largest thermal neutron capture cross section of all stable nuclei and produces an 8 MeV gamma cascade that can be detected with high efficiency. Because of the many new physics opportunities that neutron tagging with a Gd salt dissolved in water would open up, a large-scale R&D program called EGADS was established to demonstrate this technique’s feasibility. EGADS features all the components of a WC detector, chiefly a 200-ton stainless steel water tank furnished with 240 photo-detectors, DAQ, and a water system that removes all impurities from water while keeping Gd in solution. In this paper we discuss the milestones towards demonstrating the feasibility of this novel technique, and the features of EGADS in detailThis work was supported by the JSPS KAKENHI Grant Numbers JP21224004, JP26000003, JP24103004 and JP17H06365. Funding support was provided by Kavli IPMU (WPI), the University of Tokyo and the US Department of Energy. We thank the “Consorcio Laboratorio Subterraneo de Canfranc” (Spain) and the Boulby Underground Research Laboratory and in particular the staff of the BUGS facility (UK) for supporting the low-background materials screening work. Some of us have been supported by funds from the European Union H2020-MSCA-RISE-GA872549-SK2HK, the Spanish Ministry of Science and Innovation (grant PGC2018-099388-B-100), the Science and Technology Facilities Council (STFC) and GridPP, UK, and the European Union’s H2020 -MSCA-RISE-2018 JENNIFER2 grant agreement no. 82207