Direct measurement of the formation length of photons |
| |
Authors: | Andersen Kristoffer K,Andersen S?ren L,Esberg Jakob,Knudsen Helge,Mikkelsen Rune,Uggerh?j Ulrik I,Sona Pietro,Mangiarotti Alessio,Ketel Tjeerd J,Ballestrero Sergio CERN NA |
| |
Affiliation: | Department of Physics and Astronomy, Aarhus University, Aarhus C, Denmark. kka@phys.au.dk |
| |
Abstract: | We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron. With the present setup it is possible to control the separation of the foils on a μm scale and hence measure interference effects caused by the macroscopic dimensions of the formation length. Several theoretical groups have predicted this effect using different methods. Our observations have a preference for the modified theory by Blankenbecler but disagree with the results of Baier and Katkov. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|