Hamburg 2016 – scientific programme
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T: Fachverband Teilchenphysik
T 98: Experimentelle Methoden III
T 98.3: Talk
Thursday, March 3, 2016, 17:25–17:40, VMP8 SR 105
Track reconstruction for the P2 experiment — •Alexey Tyukin for the P2 collaboration — JGU, Mainz, Deutschland
The P2 experiment at the future MESA accelerator in Mainz will measure elastically scattered electrons from a hydrogen or lead target in order to determine the parity violating asymmetry for different beam polarisations, which is created due to the weak charge of the target. The asymmetry can provide access to the Weinberg angle and the neutron skin of heavy nuclei. These quantities depend heavily on the momentum transfer Q2, thus a reconstruction of single electron tracks in an inhomogeneous magnetic field is necessary. For this, the P2 detector will have four tracking planes of thin high voltage monolithic active pixel sensors (HV-MAPS).
The scattered electrons propagate through a magnetic field and hit all four planes. In order to fit the hit positions the General Broken Lines method is used. As a fast propagator, a variation of the Runge-Kutta algorithm is applied, which solves the equation of motion in an inhomogeneous magnetic field numerically, such that the final state momentum and scattering angle can be reconstructed. The initial momentum and incident angle can vary strongly due to the thickness of the target, limiting the reconstruction quality. The average single track Q2 value of 0.006 GeV2/c2 can be reconstructed with about 4 % uncertainty in a first analysis of the Geant4 simulation, leading to a high total precision due to large electron numbers in the experiment.