Search for dinucleon decay into pions at Super-Kamiokande

A 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 $^{16}$O$(pp) \rightarrow$ $^{14}$C$\pi^{+}\pi^{+}$, $^{16}$O$(pn) \rightarrow$ $^{14}$N$\pi^{+}\pi^{0}$, and $^{16}$O$(nn) \rightarrow$ $^{14}$O$\pi^{0}\pi^{0}$ 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: $\tau_{pp\rightarrow\pi^{+}\pi^{+}} > 7.22 \times 10^{31}$ years, $\tau_{pn\rightarrow\pi^{+}\pi^{0}} > 1.70 \times 10^{32}$ years, and $\tau_{nn\rightarrow\pi^{0}\pi^{0}} > 4.04 \times 10^{32}$ years. The lower limits on each mode are about two orders of magnitude better than previous limits from searches for dinucleon decay in iron.Comment: 20 pages, 17 figures. Accepted for publication in Physical Review D on March 30, 201

Search for astronomical neutrinos from blazar TXS 0506+056 in super-kamiokande

We report a search for astronomical neutrinos in the energy region from several GeV to TeV in the direction of the blazar TXS 0506+056 using the Super-Kamiokande detector following the detection of a 100 TeV neutrinos from the same location by the IceCube collaboration. Using Super-Kamiokande neutrino data across several data samples observed from 1996 April to 2018 February we have searched for both a total excess above known backgrounds across the entire period as well as localized excesses on smaller timescales in that interval. No significant excess nor significant variation in the observed event rate are found in the blazar direction. Upper limits are placed on the electron- and muon-neutrino fluxes at the 90% confidence level as 6.0 × 10−7 and 4.5 × 10−7–9.3 × 10−10 [erg cm−2 s−1], respectively

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

Used 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 in 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 detail

Requirement of Mouse BCCIP for Neural Development and Progenitor Proliferation

Multiple DNA repair pathways are involved in the orderly development of neural systems at distinct stages. The homologous recombination (HR) pathway is required to resolve stalled replication forks and critical for the proliferation of progenitor cells during neural development. BCCIP is a BRCA2 and CDKN1A interacting protein implicated in HR and inhibition of DNA replication stress. In this study, we determined the role of BCCIP in neural development using a conditional BCCIP knock-down mouse model. BCCIP deficiency impaired embryonic and postnatal neural development, causing severe ataxia, cerebral and cerebellar defects, and microcephaly. These development defects are associated with spontaneous DNA damage and subsequent cell death in the proliferative cell populations of the neural system during embryogenesis. With in vitro neural spheroid cultures, BCCIP deficiency impaired neural progenitor's self-renewal capability, and spontaneously activated p53. These data suggest that BCCIP and its anti-replication stress functions are essential for normal neural development by maintaining an orderly proliferation of neural progenitors

Successful bone marrow transplantation in a patient with DNA ligase IV deficiency and bone marrow failure

BACKGROUND: DNA Ligase IV deficiency syndrome is a rare autosomal recessive disorder caused by hypomorphic mutations in the DNA ligase IV gene (LIG4). The clinical phenotype shows overlap with a number of other rare syndromes, including Seckel syndrome, Nijmegen breakage syndrome, and Fanconi anemia. Thus the clinical diagnosis is often delayed and established by exclusion. METHODS: We describe a patient with pre- and postnatal growth retardation and dysmorphic facial features in whom the diagnoses of Seckel-, Dubowitz-, and Nijmegen breakage syndrome were variably considered. Cellular radiosensitivity in the absence of clinical manifestations of Ataxia telangiectasia lead to the diagnosis of DNA ligase IV (LIG4) deficiency syndrome, confirmed by compound heterozygous mutations in the LIG4 gene. At age 11, after a six year history of progressive bone marrow failure and increasing transfusion dependency the patient was treated with matched sibling donor hematopoetic stem cell transplantation (HSCT) using a fludarabine-based conditioning regimen without irradiation. RESULTS: The post-transplantation course was uneventful with rapid engraftment leading to complete and stable chimerism. Now at age 16, the patient has gained weight and is in good clinical condition. CONCLUSION: HSCT using mild conditioning without irradiation qualifies as treatment of choice in LIG4-deficient patients who have a matched sibling donor

Search for proton decay into three charged leptons in 0.37 megaton-years exposure of the Super-Kamiokande

A search for proton decay into three charged leptons has been performed by using 0.37 Mton⋅years of data collected in Super-Kamiokande. All possible combinations of electrons, muons, and their antiparticles consistent with charge conservation were considered as decay modes. No significant excess of events has been found over the background, and lower limits on the proton lifetime divided by the branching ratio have been obtained. The limits range between 9.2×10^33 and 3.4×10^34 years at 90% confidence level, improving by more than an order of magnitude upon limits from previous experiments. A first limit has been set for the p→μ^−e^+e^+ mode