Search

Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-β decay, and dark matter search experiments. The KamLAND-Zen experiment searches for neutrinoless double-β decay in 745 kg of xenon dissolved in liquid scintillator. The experiment includes dead-time-free electronics with a high efficiency for detecting muon-induced neutrons. The production yields of different radioisotopes are measured with a combination of delayed coincidence techniques, newly developed muon reconstruction, and xenon spallation identification methods. The observed xenon spallation products are consistent with results from the fluka and geant4 simulation codes.

We report a measurement of the strange axial coupling constant gAs using atmospheric neutrino data at KamLAND. This constant is a component of the axial form factor of the neutral-current quasielastic (NCQE) interaction. The value of gAs significantly changes the ratio of proton and neutron NCQE cross sections. KamLAND is suitable for measuring NCQE interactions as it can detect nucleon recoils with low-energy thresholds and measure neutron multiplicity with high efficiency. KamLAND data, including the information on neutron multiplicity associated with the NCQE interactions, makes it possible to measure gAs with a suppressed dependence on the axial mass MA, which has not yet been determined. For a comprehensive prediction of the neutron emission associated with neutrino interactions, we establish a simulation of particle emission via nuclear deexcitation of C12, a process not considered in existing neutrino Monte Carlo event generators. Energy spectrum fitting for each neutron multiplicity gives gAs=-0.14-0.26+0.25, which is the most stringent limit obtained using NCQE interactions without MA constraints. The two-body current contribution considered in this analysis relies on a theoretically effective model and electron scattering experiments and requires future verification by direct measurements and future model improvement.

The KamLAND-Zen experiment has provided stringent constraints on the neutrinoless double-beta (0νββ) decay half-life in ^{136}Xe using a xenon-loaded liquid scintillator. We report an improved search using an upgraded detector with almost double the amount of xenon and an ultralow radioactivity container, corresponding to an exposure of 970 kg yr of ^{136}Xe. These new data provide valuable insight into backgrounds, especially from cosmic muon spallation of xenon, and have required the use of novel background rejection techniques. We obtain a lower limit for the 0νββ decay half-life of T_{1/2}^{0ν}>2.3×10^{26}  yr at 90% C.L., corresponding to upper limits on the effective Majorana neutrino mass of 36-156 meV using commonly adopted nuclear matrix element calculations.

We report the results of a search for MeV-scale astrophysical neutrinos in KamLAND presented as an excess in the number of coincident neutrino interactions associated with the publicly available high-energy neutrino datasets from the IceCube Neutrino Observatory. We find no statistically significant excess in the number of observed low-energy electron antineutrinos in KamLAND, given a coincidence time window of ±500 s, ±1,000 s, ±3,600 s, and ±10,000 s around each of the IceCube neutrinos. We use this observation to present limits from 1.8 MeV to 100 MeV on the electron antineutrino fluence, assuming a mono-energetic flux. We then compare the results to several astrophysical measurements performed by IceCube and place a limit at the 90% confidence level on the electron antineutrino isotropic thermal luminosity from the TXS 0506+056 blazar.

The decay of the primordial isotopes 238U, 235U, 232Th, and 40K has contributed to the terrestrial heat budget throughout the Earth's history. Hence, the individual abundance of those isotopes are key parameters in reconstructing contemporary Earth models. The geoneutrinos produced by the radioactive decays of uranium and thorium have been observed with the Kamioka Liquid-Scintillator Antineutrino Detector (KamLAND). Those measurements have been improved with more than 18-year observation time, and improvement in detector background levels mainly with an 8-year nearly reactor-free period, which now permit spectroscopy with geoneutrinos. Our results yield the first constraint on both uranium and thorium heat contributions. The KamLAND result is consistent with geochemical estimations based on elemental abundances of chondritic meteorites and mantle peridotites. The High-Q model is disfavored at 99.76% C.L. and a fully radiogenic model is excluded at 5.2σ assuming a homogeneous heat producing element distribution in the mantle.

We present the results of a search for core-collapse supernova neutrinos, using long-term KamLAND data from 2002 March 9 to 2020 April 25. We focus on the electron antineutrinos emitted from supernovae in the energy range of 1.8-111 MeV. Supernovae will make a neutrino event cluster with the duration of ∼10 s in the KamLAND data. We find no neutrino clusters and give the upper limit on the supernova rate to be 0.15 yr−1 with a 90% confidence level. The detectable range, which corresponds to a >95% detection probability, is 40-59 kpc and 65-81 kpc for core-collapse supernovae and failed core-collapse supernovae, respectively. This paper proposes to convert the supernova rate obtained by the neutrino observation to the Galactic star formation rate. Assuming a modified Salpeter-type initial mass function, the upper limit on the Galactic star formation rate is

We present two results of a search for MeV-scale neutrino and anti-neutrino events correlated with gravitational wave events/candidates and large solar flares with KamLAND. The KamLAND detector is a large-volume neutrino detector using liquid scintillator, which is located at 1 km underground under the top of Mt. Ikenoyama in Kamioka, Japan. KamLAND has multiple reaction channels to detect neutrinos. Electron antineutrino can be detected via inverse-beta decay with 1.8 MeV neutrino energy threshold. All flavors of neutrinos can be detected via neutrino-electron scattering without neutrino energy threshold. KamLAND has continued the neutrino observation since 2002 March. We use the data set of 60 gravitational waves provided by the LIGO/Virgo collaboration during their second and third observing runs and search for coincident electron antineutrino events in KamLAND. We find no significant coincident signals within a ±500 s timing window from each gravitational wave and present 90% C.L. upper limits on the electron antineutrino fluence between 108–1013 cm−2 for neutrino energies of 1.8–111 MeV. For a solar-flare neutrino search at KamLAND, we determine the timing window using the solar X-ray data set provided by the GOES satellite series from 2002 to 2019 and search for the excess of coincident event rate on the all-flavor neutrinos. We find no significant event rate excess in the flare time windows and get 90% C.L. upper limits on the fluence of neutrinos of all flavors (electron anti-neutrinos) between 1010–1013 cm−2 (108–1013 cm−2) for neutrino energies in the energy range of 0.4–35 MeV.

We present the results of a time-coincident event search for low-energy electron antineutrinos in the KamLAND detector with gamma-ray bursts (GRBs) from the Gamma-ray Coordinates Network and Fermi Gamma-ray Burst Monitor. Using a variable coincidence time window of ±500 s plus the duration of each GRB, no statistically significant excess above the background is observed. We place the world's most stringent 90% confidence level upper limit on the electron antineutrino fluence below 17.5 MeV. Assuming a Fermi-Dirac neutrino energy spectrum from the GRB source, we use the available redshift data to constrain the electron antineutrino luminosity and effective temperature.

We report on a search for electron antineutrinos ( ) from astrophysical sources in the neutrino energy range 8.3-30.8 MeV with the KamLAND detector. In an exposure of 6.72 kton-year of the liquid scintillator, we observe 18 candidate events via the inverse beta decay reaction. Although there is a large background uncertainty from neutral current atmospheric neutrino interactions, we find no significant excess over background model predictions. Assuming several supernova relic neutrino spectra, we give upper flux limits of 60-110 cm-2 s-1 (90% confidence level, CL) in the analysis range and present a model-independent flux. We also set limits on the annihilation rates for light dark matter pairs to neutrino pairs. These data improve on the upper probability limit of 8B solar neutrinos converting into , (90% CL) assuming an undistorted shape. This corresponds to a solar flux of 60 cm-2 s-1 (90% CL) in the analysis energy range.

We report the result of a search for neutrinos in coincidence with solar flares from the GOES flare database. The search was performed on a 10.8 kton-year exposure of KamLAND collected from 2002 to 2019. This large exposure allows us to explore previously unconstrained parameter space for solar flare neutrinos. We found no statistical excess of neutrinos and established 90% confidence level upper limits of 8.4 × 107 cm-2 (3.0 × 109 cm-2) on the electron antineutrino (electron neutrino) fluence at 20 MeV normalized to the X12 flare, assuming that the neutrino fluence is proportional to the X-ray intensity.

We report the result of a search for neutrinos in coincidence with solarflares from the GOES flare database. The search was performed on a 10.8kton-year exposure of KamLAND collected from 2002 to 2019. This large exposureallows us to explore previously unconstrained parameter space for solar flareneutrinos. We found no statistical excess of neutrinos and established 90%confidence level upper limits of $8.4 \times 10^7$ cm$^{-2}$ ($3.0 \times10^{9}$ cm$^{-2}$) on electron anti-neutrino (electron neutrino) fluence at 20MeV normalized to the X12 flare, assuming that the neutrino fluence isproportional to the X-ray intensity.

We present the results of a search for MeV-scale electron antineutrino events in KamLAND coincident with the 60 gravitational wave events/candidates reported by the LIGO/Virgo collaboration during their second and third observing runs. We find no significant coincident signals within a 500 s timing window from each gravitational wave and present 90% C.L. upper limits on the electron antineutrino fluence between 108 and 1013 cm-2 for neutrino energies in the energy range of 1.8-111 MeV.

There are many theories where a dark matter particle is part of a multipletwith an electrically charged state. If WIMP dark matter ($\chi^{0}$) isaccompanied by a charged excited state ($\chi^{-}$) separated by a small massdifference, it can form a stable bound state with a nucleus. In supersymmetricmodels, the $\chi^{0}$ and the $\chi^{-}$ could be the neutralino and a chargedslepton, such as the neutralino-stau degenerate model. The formation bindingprocess is expected to result in an energy deposition of {\it O}(1--10 MeV),making it suitable for detection in large liquid scintillator detectors. Wedescribe new constraints on the bound state formation with a xenon nucleususing the KamLAND-Zen 400 Phase-II dataset. In order to enlarge the searchableparameter space, all xenon isotopes in the detector were used. For a benchmarkparameter set of $m_{\chi^{0}} = 100$ GeV and $\Delta m = 10$ MeV, this studysets the most stringent upper limits on the recombination cross section$\langle\sigma v\rangle$ and the decay-width of $\chi^{-}$ of $2.0 \times10^{-31}$ ${\rm cm^3/s}$ and $1.1 \times 10^{-18}$ GeV, respectively (90\%confidence level).

Purpose: This study aimed to investigate the process mothers go through in coming to terms with raising a child with chromosomal structural abnormalities., Methods: Sixteen mothers living in Japan were interviewed and a modified grounded theory approach was used for the analysis., Results: A total of 35 concepts, nine subcategories, and six categories were extracted. The six categories were: (a) Concern about abnormalities; (b) A healthy child is considered as a standard; (c) Deepening attachment to the child; (d) Acceptance of the child as s/he is; (e) Changing attitude toward disabilities; (f) Creating a frontier for other mothers. The parenting journey meant that parents did not move in a straightforward way from the beginning of the process to the endpoint but instead moved between "Deepening attachment to the child" and "Acceptance of the child as s/he is" before they moved ahead., Conclusion: Having support and meeting peers of mothers with similar issues is essential for mothers to review their perspectives that healthy children are the standard against which to measure their child and to motivate them to raise their children, but it was extremely difficult to have such opportunities due to rarity of the disorder. It is crucial to accumulate more practical information so that mothers can access and use it. Mothers also need support to enhance their self-worth while giving due consideration to the possibility that they may be conscious of being stigmatized. Nurses need to advocate for these children and families to get the appropriate help, understanding and support., (© 2020 Japan Academy of Nursing Science.)

To examine the perception of nuclear energy risks among Asian university students following the Fukushima nuclear disaster, a standardized questionnaire survey was conducted since July 2011 after the Fukushima disaster. A total of 1814 respondents from 18 universities in China, Japan, Korea, and Taiwan participated in this survey. It showed that students with the following characteristics had a higher preference for "a clear schedule to phase out nuclear power plant (NPP)": females (adjusted odds ratio [aOR] = 1.84, 95% confidence interval [CI] = 1.44-2.34), in Japan (aOR = 2.81, 95% CI = 2.02-3.90), in China (aOR = 1.48, 95% CI = 1.04-2.09), and with perceived relative risks of cancer incidence greaterthan 1 (aOR = 1.42, 95% CI = 1.07-1.88). "If nuclear energy were phased out," the opinions on potential electricity shortage were as follows: Japan, aOR = 0.53, 95% CI = 0.40-0.69; China, aOR = 2.46, 95% CI = 1.75-3.45; and associated with academic majors (science/technology, aOR = 0.43, 95% CI = 0.31-0.59; medicine/health science, aOR = 0.64, 95% CI = 0.49-0.84). The results carried essential messages for nuclear energy policy in East Asia., (© 2014 APJPH.)

The p16INK4A gene, which encodes the cell-cycle regulatory protein cyclin-dependent kinase 4 inhibitor, is a putative tumor-suppressor gene. We examined p16 gene alterations in 30 primary ovarian cancers and 11 ovarian cancer cell lines. Five of the primary cancers (16.7%) had lost both p16INK4A genes. In addition, four cancers (13.3%) contained five kinds of missense mutations and a one-base deletion. Three cell lines had homozygous deletions of p16 genes, and one cell line had multiple intragenic mutations. There was also suppressed transcription of the p16 gene in one cell line. Some point mutations occurred in the conserved ankylin consensus region. These observations suggest that p16 is a functional target for ovarian carcinogenesis and that p16 alterations occurred in the primary cancers.

The present study was undertaken to define the gene(s) of importance on the long arm of chromosome 18 (chromosome 18q) in endometrial carcinomas. We analyzed loss of heterozygosity (LOH) at 3 loci on chromosome 18q and DCC gene expression by the reverse-transcriptase/polymerase chain reaction (RT-PCR) method. Among 61 tumors that were informative, 16 (26%), estimated to be a minimum number, showed allelic losses at one or more chromosome 18q loci. Deletions in these tumors possibly involved the region within or near the chromosome 18q 21.3 band where the DCC gene was localized. Moreover, the incidence of altered DCC mRNA expression was high in these tumors. Appropriate transcription was lost in 5 of 7 (71%) carcinoma cell lines in addition to 14 of 28 (50%) surgically resected tumors. Histopathological differentiation and clinical stage of disease were not related to LOH frequency or to DCC mRNA expression. These results suggest that the target for allelic loss on chromosome 18q seen in endometrial carcinomas is the DCC gene, and that inactivation of this gene may be critical for the development of most endometrial carcinomas.

Mutations in the p53 gene are associated with a wide variety of human malignancies. Point mutation in one allele and loss of the remaining one generally lead to inactivation of p53 protein. A high frequency of allelic losses corresponding to the 17p13.3 region that contained the p53 gene sequence was also noted in human endometrial carcinoma. Thus, in order to confirm involvement of the p53 gene in endometrial carcinogenesis, we searched for nucleotide sequence change in this gene in 42 endometrial carcinomas that had been subjected to previous LOH analyses. Using the polymerase-chain-reaction-single-strand conformation polymorphism (PCR-SSCP) method, we detected p53 gene mutations in 4 specimens. Two adenocarcinomas with allelic loss on 17p contained a mutant p53 gene in the allele that was retained. One specimen with a p53 gene mutation contained a 17q deletion but was uninformative for LOH on 17p. p53 gene mutation was also noted in the remaining stage-I carcinoma, though the 17p deletion was not detected in the previous LOH examination. However, 5 specimens with the LOH on 17p retained the wild-type p53 gene. In the remaining 33 specimens, both alleles of p53 gene seemed to be normal. The mutations observed in 2 specimens (cases 10 and 24), involving C-to-T and T-to-G substitutions, were located in a highly conserved region. However, the mutations identified in the remaining 2 cases (29 and 35) were at regions positioned outside conserved stretches.