Fundamental physics activities with pulsed neutron at J-PARC(BL05)

"Neutron Optics and Physics (NOP/ BL05)" at MLF in J-PARC is a beamline for studies of fundamental physics. The beamline is divided into three branches so that different experiments can be performed in parallel. These beam branches are being used to develop a variety of new projects. We are developing an experimental project to measure the neutron lifetime with total uncertainty of 1 s (0.1%). The neutron lifetime is an important parameter in elementary particle and astrophysics. Thus far, the neutron lifetime has been measured by several groups; however, different values are obtained from different measurement methods. This experiment is using a method with different sources of systematic uncertainty than measurements conducted to date. We are also developing a source of pulsed ultra-cold neutrons (UCNs) produced from a Doppler shifter are available at the unpolarized beam branch. We are developing a time focusing device for UCNs, a so called "rebuncher", which can increase UCN density from a pulsed UCN source. At the low divergence beam branch, an experiment to search an unknown intermediate force with nanometer range is performed by measuring the angular dependence of neutron scattering by noble gases. Finally the beamline is also used for the research and development of optical elements and detectors. For example, a position sensitive neutron detector that uses emulsion to achieve sub-micrometer resolution is currently under development. We have succeeded in detecting cold and ultra-cold neutrons using the emulsion detector.Comment: 9 pages, 5 figures, Proceedings of International Conference on Neutron Optics (NOP2017

New project for precise neutron lifetime measurement at J-PARC

The decay lifetime of free neutrons (∼880 s) is an important parameter of the weak interaction and for Big Bang Nucleosynthesis. However, results of measurements currently show discrepancies depending on the method used. As most experiments nowadays employ ultra cold neutrons, we have developed a new cold-beam experiment which we perform at the Japan Proton Accelerator Research Complex. As a special feature, a polarized neutron beam is bunched by a spin flip chopper. A time projection chamber operated with He and CO2 gas, including a well-controlled amount of 3He, is used for detection of the beta-decays and simultaneous determination of the beam intensity. Using the data between 2014 and 2016, we evaluated our first, preliminary result of the neutron lifetime as 896 ± 10(stat.) −10+14(sys.) s. We plan several upgrades to achieve our precision goal of 1 s

New project for precise neutron lifetime measurement at J-PARC

The decay lifetime of free neutrons (∼880 s) is an important parameter of the weak interaction and for Big Bang Nucleosynthesis. However, results of measurements currently show discrepancies depending on the method used. As most experiments nowadays employ ultra cold neutrons, we have developed a new cold-beam experiment which we perform at the Japan Proton Accelerator Research Complex. As a special feature, a polarized neutron beam is bunched by a spin flip chopper. A time projection chamber operated with He and CO2 gas, including a well-controlled amount of 3He, is used for detection of the beta-decays and simultaneous determination of the beam intensity. Using the data between 2014 and 2016, we evaluated our first, preliminary result of the neutron lifetime as 896 ± 10(stat.) −10+14(sys.) s. We plan several upgrades to achieve our precision goal of 1 s

National trends in the outcomes of subarachnoid haemorrhage and the prognostic influence of stroke centre capability in Japan: retrospective cohort study

Objectives To examine the national, 6-year trends in in-hospital clinical outcomes of patients with subarachnoid haemorrhage (SAH) who underwent clipping or coiling and the prognostic influence of temporal trends in the Comprehensive Stroke Center (CSC) capabilities on patient outcomes in Japan.Design Retrospective study.Setting Six hundred and thirty-one primary care institutions in Japan.Participants Forty-five thousand and eleven patients with SAH who were urgently hospitalised, identified using the J-ASPECT Diagnosis Procedure Combination database.Primary and secondary outcome measures Annual number of patients with SAH who remained untreated, or who received clipping or coiling, in-hospital mortality and poor functional outcomes (modified Rankin Scale: 3–6) at discharge. Each CSC was assessed using a validated scoring system (CSC score: 1–25 points).Results In the overall cohort, in-hospital mortality decreased (year for trend, OR (95% CI): 0.97 (0.96 to 0.99)), while the proportion of poor functional outcomes remained unchanged (1.00 (0.98 to 1.02)). The proportion of patients who underwent clipping gradually decreased from 46.6% to 38.5%, while that of those who received coiling and those left untreated gradually increased from 16.9% to 22.6% and 35.4% to 38%, respectively. In-hospital mortality of coiled (0.94 (0.89 to 0.98)) and untreated (0.93 (0.90 to 0.96)) patients decreased, whereas that of clipped patients remained stable. CSC score improvement was associated with increased use of coiling (per 1-point increase, 1.14 (1.08 to 1.20)) but not with short-term patient outcomes regardless of treatment modality.Conclusions The 6-year trends indicated lower in-hospital mortality for patients with SAH (attributable to better outcomes), increased use of coiling and multidisciplinary care for untreated patients. Further increasing CSC capabilities may improve overall outcomes, mainly by increasing the use of coiling. Additional studies are necessary to determine the effect of confounders such as aneurysm complexity on outcomes of clipped patients in the modern endovascular era