Measurement of helicity dependence of single π0 photoproduction on deuteron

The study of the properties of the baryon resonances gives essential constraints on models for nucleon structure. Pion-photoproduction is a powerful tool to excite the nucleon to an intermediate resonant state and, in combination with polarised beams/targets, plays an important role in the investigation of the nucleon resonances. Data for polarisation observables accessible using a polarised photon beam and/or polarised nucleon targets are scarce in many channels, especially in those involving a neutron target. A systematic measurement is performed at the Mainz facility by the A2@MAMI collaboration. This talk will focus on the experiment performed at the Mainz Microtron, using a circularly polarised photon beam and a longitudinally polarised deuteron target, in conjunction with the large acceptance Crystal Ball/TAPS detection setup. An overview of the status of the experiment will be given, together with the preliminary results of polarised cross section from deuteron and of the double polarization observable E for the single π0 photoproduction reaction from the quasi-free proton and quasi-free neutron.

Experimental Facility at A2 Collaboration (MAINZ) for Photoproduction reaction

<p>Since 20 years, a very successful experimental program with real photons has been achieved at the Mainz Microtron (MAMI) facility. The A2 Collaboration at MAINZ is a unique place for the experimental facility of photoproduction reaction. The combination of highly sensitive photo spectrometers Crystal Ball and TAPS as forward wall detector along with particle identification detector and Multiwire proportional chambers as inner wall detectors provide the high precision of the measurement. MAMI-C, which consists of there Race Track Microtrons (RTMs) with the Harmonic Double -Sided Microtron (HDSM) is an intense, stable and continuous-wave accelerator to accelerate electron to 1.5 GeV. This electron beam is responsible to produce real photons via bremsstrahlung process at Glasgow Photon Tagger. A major part of the ongoing and future programme at MAMI will exploit polarised nucleon targets.</p><p>Journal of Nepal Physical Society Vol.3(1) 2015: 73-81</p>

THE γp → K0Σ+ PHOTOPRODUCTION REACTION

The photoproduction reaction γp → K0Σ+ was investigated with the CBELSA/TAPS experiment at the electron accelerator facility ELSA of the University of Bonn. A pronounced structure in the cross section was found at the K* threshold. There are indications that this may be associated with the formation of a K*-hyperon quasibound state below the K* threshold. The very first measurements of the photon beam asymmetry in the studied reaction channel are presented and their impact is discussed.

CHIRAL DYNAMICS AND DUBNA-MAINZ-TAIPEI DYNAMICAL MODEL FOR PION PHOTOPRODUCTION REACTION

We demonstrate that the Dubna-Mainz-Taipei (DMT) meson-exchange dynamical model, which starts from an effective chiral Lagrangian, for pion photoproduction provides an excellent and economic framework to describe both the π0 threshold production and the Δ deformation, two features dictated by chiral dynamics.

A NEW MEASUREMENT OF BEAM ASYMMETRY IN PION PHOTOPRODUCTION FROM THE NEUTRON USING CLAS

We present a preliminary analysis of the photon beam asymmetry observable (Σ) from the photoproduction reaction channel γn → π-p. This new data was obtained using the near-4π CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 - 2.3 GeV. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle.