....nucleus consists of protons and neutrons... three goals .. strange quark... two photons .. axial form factor parity violation... MAMI ....1022... polarimeters
The atomic nucleus consists of protons and neutrons that are called nucleons. There are six types of quarks in the standard model. In the constituent quark model nucleons, however, are buit up only with two of them: up and down quark. Quantum chromodynamics describes these quarks as valence quarks by analogy with valence electrons. The quarks are bound inside the nucleon by the force, which is called Color force, by exchanges of gluons. The gluons can split into virtual quark-antiquark pairs. These virtual quarks are called sea quarks.
A4 collaboration has three scientific goals:
  1. To investigate the influence of the strange quark in the nucleon form factor
  2. To measure the effect of the two-photon exchange in the elastic electron-nucleon scattering
  3. To measure the nucleon axial form factor that was predicted by the theory experimentally
A4 collaboration experimental setup has three parts:
  1. MAMI accelerator
  2. Target, calorimeter, and luminosity monitors
  3. Polarimeters
D etector Relocation Process:
Contacts
Secretary : Mrs. Sabine Klotter
Spokesperson of A4 Collaboration: Dr. Sebastian Baunack
Spokesperson of SFB Project P2: Prof. Dr. Frank Maas
Ms. Petra Bischof
Dr. Sebastian Baunack
Prof. Dr. Frank Maas
The cw electron accelerator MAMI consists of three cascaded racetrack microtrons with a 3.5MeV injector linac, followed by a Harmonic Double Sided Microtron (HDSM) as the fourth and last stage. The maximum output energy is 1508MeV with a beam current of up to 100µA. The third stage (RTM3) delivers beams from 180MeV to 855MeV in 15MeV steps. After installation of the extraction system of the HDSM also in the range of 855MeV to 1508MeV beam extraction in steps of approx. 15MeV will be possible. Normal conducting accelerating structures in connection with multiple beam recirculation represent an economical and reliable solution for stable acceleration of the intense electron beam. The relatively modest ratio between output and input energy of each stage made it possible to build the microtrons according to the fundamental design idea, avoiding complicated injection and focusing schemes. Therefore, and due to the high precision and homogeneity of the end magnets, the transverse and longitudinal beam transport through the microtrons occurs in a nearly ideal way. Owing to the extensive beam monitor and computer control system the accelerator complex is easy to operate, and several automatic optimising routines serve for short beam setup and optimisation times. The stability of the machine is excellent, the mean time between corrections by the operator normally being more than ten hours. Due to the highly stabilized rf amplitude in the acceleration sections the beam intensity can easily be changed and even pulsed up to more than 110µA with a rise time of 100µs.