Search NASA⌕ Search

Engineering topics

Yanai, K.

Publications and source records attributed to Yanai, K..

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A search for $$\upmu ^+ \rightarrow \textrm{e}^+ \upgamma $$ with the first dataset of the MEG II experiment

Abstract The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay$$\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma $$ μ + → e + γ from data taken in the first physics run in 2021. No excess of events over the expected background is observed, yielding an upper limit on the branching ratio of$${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 7.5 \times 10^{-13}$$ B ( μ + → e + γ ) < 7.5 × 10 - 13 (90% CL). The combination of this result and the limit obtained by MEG gives$${\mathcal {B}} (\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma ) < 3.1 \times 10^{-13}$$ B ( μ + → e + γ ) < 3.1 × 10 - 13 (90% CL), which is the most stringent limit to date. A ten-fold larger sample of data is being collected during the years 2022–2023, and data-taking will continue in the coming years.

Physics↗
DOE OSTI2024

Operation and performance of the MEG II detector

Abstract The MEG II experiment, located at the Paul Scherrer Institut (PSI) in Switzerland, is the successor to the MEG experiment, which completed data taking in 2013. MEG II started fully operational data taking in 2021, with the goal of improving the sensitivity of the$$\upmu ^+ \rightarrow {\textrm{e}}^+ \upgamma $$ μ + → e + γ decay down to$$\sim 6 \times 10^{-14}$$ ∼ 6 × 10 - 14 almost an order of magnitude better than the current limit. In this paper, we describe the operation and performance of the experiment and give a new estimate of its sensitivity versus data acquisition time.

Physics↗
DOE OSTI2020

Search for lepton flavour violating muon decay mediated by a new light particle in the MEG experiment

We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, μ + → e + X,X → γγ . This search uses a dataset resulting from 7.5 × 10 14 stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c 2 for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c 2 , down to O(10 –11 ) at 90% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1981

Organic analysis of the Antarctic carbonaceous chondrites

Thus far, organic analysis of carbonaceous chondrites has proven the only fruitful means of examining complex organic matter of extraterrestrial origin. The present paper presents the results of organic analysis of two Antarctic meteorites, Allan Hills (77306) and Yamato (74662), which may be considered free from terrestrial contamination. Ion-exchange chromatography, gas chromatography and mass spectrometery of meteorite samples reveal the presence in Yamato of 15 and in Allan Hills of 20 protein and nonprotein amino acids, the most abundant of which are glycine and alanine. Abundances of the D and L enantiomers of each amino acid are also found to be nearly equal. Data thus indicate an abiotic extraterrestrial origin for the matter, and confirm a lack of terrestrial contamination.

Kotra, R. K.↗
NASA NTRS1979

Amino acids in the Yamato carbonaceous chrondrite from Antarctica

Evidence for the presence of amino acids of extraterrestrial origin in the Antarctic Yamato carbonaceous chrondrite is presented. Hydrolyzed and nonhydrolyzed water-extracted amino acid samples from exterior, middle and interior portions of the meteorite were analyzed by an amino acid analyzer and by gas chromatography of N-TFA-isopropyl amino acid derivatives. Nine protein and six nonprotein amino acids were detected in the meteorite at abundances between 34 and less than one nmole/g, with equal amounts in interior and exterior portions. Nearly equal abundances of the D and L enantiomers of alanine, aspartic acid and glutamic acid were found, indicating the abiotic, therefore extraterrestrial, origin of the amino acids. The Antarctic environment and the uniformity of protein amino acid abundances are discussed as evidence against the racemization of terrestrially acquired amino acids, and similarities between Yamato amino acid compositions and the amino acid compositions of the Murchison and Murray type II carbonaceous chrondrites are indicated.

Shimoyama, A.↗
NASA NTRS1979

Total carbon and sulfur abundances in Antarctic meteorites

Total carbon and sulfur abundances have been measured in five Antarctic meteorites. Two C2 carbonaceous chondrites Yamato 74662 and Allan Hills 77306 have sulfur abundances (3.490 plus or minus .040% and 3.863 plus or minus 0.050% respectively) similar to other C2 chondrites but their carbon abundances (1.514 plus or minus 0.050% and 1.324 plus or minus .040% respectively) are lower than previously measured C2 chondrites. The decreased carbon abundances may reflect the effects of weathering in cold environments. Carbon and sulfur abundances for one C4 carbonaceous chondrite, one E4 enstatite chondrite and one ureilite are similar to values reported previously for meteorites of the same petrologic grades.

Gibson, E. K., Jr.↗
NASA NTRS1978

The Yamato-74659 ureilite and some new findings on the Yamato achondritic pyroxenes

A cube-like fragment with an approximately 4 mm edge was taken from the Yamato-74659 meteorite for the mineralogical and crystallographic examination discussed in the present paper. An analysis of powdered fragments by a standard wet chemical method showed that it matched to weathered ureilite. The chemical composition was found to differ from other ureilites in that the FeO content (8.83 wt%) is the lowest among known ureilites and it is richer in SiO2 contents (42.91 wt%).

Takeda, H.↗