1992 Fiscal Year Final Research Report Summary
Baryon Number Violating Process and Sphaleron
| Project/Area Number |
03640276
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
OTSUKI Shoichiro Dep't of Physics, Kyushu Univ. Prof., 理学部, 教授 (80037142)
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| Co-Investigator(Kenkyū-buntansha) |
TOYODA Fumihiko Dep't of Lib. Arts,in Kyushu Kinki Univ. Prof., 九州工学部, 教授 (60088622)
HARADA Koji Dep't of Physics, Kyushu Univ. Research Associate, 理学部, 助手 (00202268)
KASHIWA Taro Dep't of Physics, Kyushu Univ. Research Associate, 理学部, 助手 (30128003)
IMACHI Masahiro Dep't of Physics, Kyushu Univ. Associate Prof., 理学部, 助教授 (70037208)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Electroweak dynamics / Baryon number violation / Sphaleron / Tunneling effect / Bounce solution / Unitarity bound |
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| Research Abstract |
A formalism to treat tunneling process in quantum field theory is developed. Even in quantum field theory, the process is known to be reduced to an one dimensional problem with respect to a parameter along the tunneling. The bounce solution in the reduced version of the theory is made full use of to obtain tunneling probability.
The formalism was applied to evaluating high energy cross section with baryon number violation due to anomaly of quantum electroweak dynamics. Sphaleron is a saddle point solution at the top of the tunneling barrier that connects topologically inequivalent vacua.
The evaluated cross section is by orders of magnitude smaller than the unitarity bound. The reasons are as follows: (i) Since the sphaleron is an extended configuration of the nonperturbative character, its overlap with the incident (outgoing) plane wave at the entrance (exit) of the tunneling damps rapidly for high momentum particles. (ii) The number of the produced particles are finite (about 100), so that an easy approximation usually adpoted such as exponentiation is misleading.
The alove result forms a sharp contrast to earlier works by Ringwald and Espinosa that the cross section with baryon number violation brows as largely as to reach the unitarity bound. It should be added, however, that many of recent works support our conclusion.
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