雙光子交換對電子核子碰撞的貢獻

Two-Photon Exchange Effect in the Elastic Electron-Nucleon Scattering

陳佑駿(Yu-Chun Chen)

指導教授 ： 楊信男

國立臺灣大學/理學院/物理研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.00447

摘要

對於核子波形因子的量測，近代的極化實驗所得的結果，和以前非極化實驗所得的結果對比時，雖在低動量交換時能夠一致，但在高動量交換時卻有巨大的不同。為要解決這個迷題，雙光子交換在彈性電子質子碰撞中的效應開始被注重起來。我們透過部份子的模型，計算雙光子交換的貢獻。我們發現，當加入雙光子交換的貢獻後，能很好的解決之前兩種實驗所得結果嚴重衝突的問題。如今我們明白，雙光子交換的效應，在量測核子的波形因子時伴演了很重要的角色。

關鍵字

核子波行因子,雙光子交換,彈性核子碰撞,部分子,質子,中子

並列摘要

When measuring the nucleon form factors, recent polarization experiments at the Thomas
Jefferson Laboratory (JLab) have confirmed the earlier Rosenbluth measurements from SLAC
at small Q2. However, at large Q2, a huge discrepancy appear between them. To solve this
puzzle, the two-photon exchange contribution to elastic electron-proton scattering at large
momentum transfer by using a quark-parton representation of virtual Compton scattering was
estimated. And then we thus can relate the two-photon exchange amplitude to the generalized
parton distributions which also enter in other wide angle scattering processes. We find that the interference of one- and two-photon exchange contribution is able to substantially resolve the difference between electric form factor measurements from Rosenbluth and polarization transfer experiments. Now we know higher-order QED effects can play an important role in precision measurements of nucleon elastic form factors in electron scattering.

並列關鍵字

nucleon form factors, two-photon exchange, elastic scattering, partonic, proton,

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