TY  - CONF
AU  - Kohl, Michael
TI  - EM Form Factors and OLYMPUS
JO  - The European physical journal / Web of Conferences
VL  - 81
SN  - 2100-014X
CY  - Les Ulis
PB  - EDP Sciences
M1  - PUBDB-2016-02983
SP  - 01006 -
PY  - 2014
AB  - The elastic form factors of the nucleon characterize the distributions of charge and magnetization in momentum space and are important input for calculations of strong interaction phenomena and nuclear structure. The dramatic discrepancy in the observed ratio of elastic proton form factors between the Rosenbluth separation and polarization transfer methods has invoked numerous theoretical and experimental investigations. The previously neglected effect from two-photon exchange has become the favored explanation for the discrepancy. While the effect can not be calculated from first principles, it can be verified experimentally in several ways, most stringently by comparing the positron-proton and electron-proton elastic cross sections. The OLYMPUS experiment at DESY has been carried out to quantify the effect of two-photon exchange using intense stored positron and electron beams along with an internal unpolarized hydrogen target and alarge acceptance detector to measure the ratio of the positron-proton and electron-proton elastic scattering cross sections. The status of proton form factor measurements and of the experimental efforts to verify the effect of two-photon exchange is presented, withsome emphasis on the OLYMPUS experiment.
T2  - 13th International Workshop on Meson Production, Properties and Interaction
CY  - 29 May 2014 - 3 Jun 2014, KRAKÓW (Poland)
Y2  - 29 May 2014 - 3 Jun 2014
M2  - KRAKÓW, Poland
LB  - PUB:(DE-HGF)16 ; PUB:(DE-HGF)8
UR  - <Go to ISI:>//WOS:000351440900006
DO  - DOI:10.1051/epjconf/20148101006
UR  - https://bib-pubdb1.desy.de/record/301926
ER  -