2006 Fiscal Year Final Research Report Summary
Precise measurement of x-rays from kaonic helium atom
| Project/Area Number |
17340087
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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 |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | The Institute of Physical and Chemical Research |
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Principal Investigator |
OUTA Haruhiko The Institute of Physical and Chemical Research, Advanced Meson Science Laboratory, Senior Research Scientist (60221818)
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| Co-Investigator(Kenkyū-buntansha) |
IWASAKI Masahiko RIKEN, Advanced Meson Science Laboratory, Chief Scientist (60183745)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Exotic atom / K meson / x-ray detection / SDD / Silicon Drift Detector / Kaonic nucleus / Precision measurement |
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| Research Abstract |
In order to study the strong interaction between K meson and nucleus in the low energy region, we carried out a precise measurement of the energy of x-rays emitted from the 3d→2p transition of kaonic 4He atom. The experiment was carried out as the last experiment of KEK-PS (E570) and we took data in fiscal year 2005. We intensively analyzed the data in fiscal year 2006.
There were three independent measurements for this 3d→2p transition x-ray energy before our experiment and the average of those results was about 40±8eV repulsive shift, while most of the theoretical calculations predict much smaller energy shift. The disagreement of this 2p level shift between them has been known for a long term as "the puzzle of kaonic helium atom" and the new precision measurement has been awaited.
In our experiment(E570), we improved following points :
(1) We utilized newly developed Silicon Drift Detectors (SDDs). The SDD has better energy resolution than the conventional Si(Li) detector. It also has good capability to reduce soft-compton x-rays background.
(2) We can calibrate absolute energy scale by referring the energy of characteristic x-ray from Ti/Ni foils placed on the beam. In-situ energy calibration has been achieved for the first time.
(3) We can track both of incoming kaons and outgoing charged particles by drift chambers, which enabled us to cleanly identify the events from stopped K-reaction on helium target.
In the x-ray spectrum, we drastically improved statistics, resolution and signal-to-noise ratio and we achieved about 2eV accuracy for the energy measurement. We found that the level shift of kaonic helium 2p state is almost consistent with zero and its width is also consistent with 0 (less than 16eV(95% CL). Those results has been published in a referred journal.
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Research Products
(6 results)
