Proton electromagnetic form factors: present status and future perspectives at PANDA
on behalf of the PANDA Collaboration
CEA, IRFU, SPhN, Saclay, 91191 Gif-sur-Yvette Cedex, France and
CNRS/IN2P3, Institut de Physique Nucl\'eaire, UMR 8608, 91406 Orsay, France
Electromagnetic FFs are fundamental quantities, which describe the internal structure of hadrons and the dynamic behaviour of their charge and magnetic distributions. Although experiments and theories develop since decades, recent experimental advances have driven an intensive and renewed activity in the field.
The development of high intensity, high polarized electron beams, large solid angle spectrometers and proton and neutron polarimeters in the GeV range opened the possibility to apply the polarization method suggested in the 70's by the Kharkov School and obtain precise and surprising data at electron accelerators.
At electron-positron facilities, using initial state radiation, BABAR measured FFs in a wide time-like kinematical region and the BES collaboration will measure very precisely proton and neutron FFs in the threshold region.
In next future an antiproton beam with momentum up to 15 GeV/c will be available at FAIR (Darmstadt) and measurements by the PANDA collaboration of proton-antiproton annihilation into an electro-positron pair should allow a precise measurement of electric and magnetic FFs in the time-like region in a wide region of momentum transfer. The emission of an additional pion will allow for the first time to access the unphysical region, below the kinematical threshold.
We will show the results of feasibility studies at PANDA and focus on the consequences of such measurements in view of a unified description of FFs in the full kinematical region. We will present models which have the necessary analytical requirements to apply in the whole kinematical region.
For many experiments, e.g. those at the LHC, design choices made a very long time ago for the compute and trigger model are still used today. The incoming experiments have the opportunity to make new choices based on the current state of computing technology and novel ways to design the reconstruction frameworks, using the experience from previous experiments as well as already existing software packages developed outside the collaboration and used and by a larger community. This talk will show the computing decisions and the current developments of the Panda experiment at FAIR - Darmstadt (Germany), which will take data starting from 2018. One of the key features is a modular software framework with a dynamic data structure based on ROOT, in common to other experiments outside FAIR, with the possibility to run simulation and analysis on grid but open to different middleware technologies such as the cloud. Due to the high data rate, a special attention is also given to the online reconstruction of the continuous data stream coming from a trigger-less DAQ system, where the pre-processing for event selection is done online and concurrency is the key feature to achieve the requested high performances; all the efforts to develop a modular multi-core architecture, supporting also FPGA and GPU units, will be here presented together with the results obtained so far.