Darmstadt 2016 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 45: Postersession

HK 45.17: Poster

Mittwoch, 16. März 2016, 18:30–20:30, S1/05 22-24

Measurement of the e⁺ e⁻ → p p cross section at BESIII using the untagged-initial state radiation technique — •Alaa Dbeyssi¹, Samer Ali Nasher Ahmed^1,2, Paul Larin^1,2, Dexu Lin^1,2, Christoph Rosner^1,2, Frank Maas^1,2,3, Cristina Morales¹, and Yadi Wang^1,2 for the BESIII collaboration — ¹Helmholtz-Institut Mainz, Mainz, Germany — ²Institute of Nuclear Physics, Johannes Gutenberg-Universität Mainz, Germany — ³PRISMA Cluster of Excellence, Johannes Gutenberg-Universität Mainz, Germany

Electromagnetic form factors (FFs) are fundamental quantities which parametrise the electric and magnetic structure of hadrons. In the time-like region, proton FFs can be accessed through the annihilation process e⁺ e⁻ → p p, assuming that the interaction takes place through the exchange of one virtual photon. Initial state radiation (ISR) is an effective tool to measure hadronic cross section at high luminosity e⁺e⁻ storage rings, such as the Beijing Electron-Positron Collider II (BEPC-II). This contribution reports on the analysis of e⁺ e⁻ → p p γ for proton FF measurements at the Beijing Spectrometer III (BESIII/BEPC- II). Data collected at 7 beam energies between 3.773 and 4.6 GeV, with a total luminosity of 7.408 fb⁻¹, are analysed. The case of untagged ISR photon in e⁺ e⁻ → p p γ is presented.