1997 Fiscal Year Final Research Report Summary
Precision Measurement of 4 and 5 photon decay in positronium
| Project/Area Number |
08454068
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | TOKYO METROPOLITAN UNIVERSITY |
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Principal Investigator |
CHIBA Masami Tokyo Metropolitan Univ., Physics Dept., Reserch Associate, 大学院理学研究科, 助手 (60128577)
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| Co-Investigator(Kenkyū-buntansha) |
KUMITA Tetsurou Tokyo Metropolitan Univ., Physics Dept., Reserch Associate, 大学院理学研究科, 助手 (30271159)
HAMATSU Ryousuke Tokyo Metropolitan Univ., Physics Dept., Associate Professor, 大学院理学研究科, 助教授 (20087092)
HIROSE Tachishige Tokyo Metropolitan Univ., Physics Dept., Professor, 大学院理学研究科, 教授 (70087162)
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| Project Period (FY) |
1996 – 1997
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| Keywords | positron / positronium / higher order QED process / charge conjugation / GSO scintillator / 4 and 5 photon decay / positron beam / ortho-positronium lifetime |
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| Research Abstract |
In 1996 we published the first results of the measurement of 5 photon decay from ortho-positronium. This was the first test of the 8th order of a without including the lower order in QED.In the second paper we published the results of the measurement of the charge conjugation invariance in 4 photon decay from ortho-positronium. It is inhibited by charge conjugation invariance to decay even number of photons. By the Grant-in Aid we presented and discussed in the international conference held at Poland. The contents were published in the third paper.
In 1997 we prepared to use the slow positron beam facility at the National Laboratory for High Energy Physics. The experiment had been approved as the experiment 95-G158. We set the multi-gamma ray spectrometer at the down stream of the line and connected by high vacuum pipe. In order to introduce the beam to the center of the spectrometer, we generated a magnetic field by selenoidal and Helmholz coils. After the preparetion we succeeded to t
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ransport the beam to the entrance of the spectrometer. But we did not have enough time to do the experiment since the slow positron beam line should to move due to the construction of the injector for the B factory. After that we studied the positron beam transport line with alternating magnetic field along the beam line using radially magnetized cylindrical permanent magnets. The preliminary experimental results are encouraging. They have some advantages over electromagnets. They generate strong magnetic field with small magnetic flux leakage, have no power dissipation to heat the environment and are compact. The relevant results was presented at the international conference held at South Africa andwill appear in the fifth paper. We have studied and planed for the new spectrometer to have 10 times larger acceptance for the 4 and 5 photon-decay compared to the existing spectrometer furnished with 32 NaI scintillators. The new one has 92 GSO scintillators to detect the photons. Discrepancy between QED and experiments concerning to the lifetime of ortho-positronium have been reported by Michigan Univ.group. In order to resolve the puzzle, we have studied a spectrometer to utilize 6 GSO scintillators to detect the decay 2 and 3 photons from ortho-positronium in good separation. By the Grant-in Aid we presented and discussed about the theme in the international conference held at England. The contents were published in the fourth paper. Less
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