1. POSTER TEMPLATE BY: www.PosterPresentations.com D(e,e   p RTPC )X D(e,e   p RTPC p CLAS )X N(e,e   )XD(e,e   p CLAS )X E = 5.3GeV Simulation Procedure Event Generator  Geant4 RTPC  gsim (CLAS)  RECSIS (reconstruct) LOGO Exclusive  - Electro-production from the Neutron in the Resonance Region Jixie Zhang for the BoNuS Collaboration Old Dominion University LOGO Radial Time Projection Chamber D(e,e’   p)p Study Neutron Resonances Kinematic Acknowledgements The study of baryon resonances is crucial to our understanding of nuclear structure and dynamics. The excited states of the proton have been studied in great detail. One would like to characterize the neutron in the same fashion. The ratio of spectral functions with and without FSI corrections is shown as a function of spectator momenta p s and θ pq (the angle between spectator proton and virtual photon). Simulation is one of my major contribution in BoNuS experiment. I developed the Geant4 simulation for RTPC, then modified the exist gsim code and RECSIS to fit our purpose. We checked the reconstruction software base on the fake tracks from the simulation. I have also developed the energy loss correction for CLAS and RTPC particles. Currently I am running to simulation to finish the acceptance correction. A long and thin target of deuterium gas at 7 atm with a diameter of 6 mm and a length of 20 cm. Drift region locates at 3 to 6 cm from the target and is filled with a drift gas (helium-DME). The ionized electrons are avalanched by the 3 layer of Gaseous Electron Multipliers (GEMs) and finally collected by the readout pad array on the surface of the detector cylinder. MAGBOLTZ simulation I would like to express my sincere gratitude to the DOE, the entire CLAS and BoNuS collaborations. Many, many thanks go to my advisors G. Dodge and S. Kuhn for all of their encouragement, suggestion, guidance and patience. Also I’d like to acknowledge the significant contributions of my fellow graduate students N. Baillie, N. Kalantarians and S. Tkachenko. However, a free neutron target is impossible due to its instability. Most of the neutron data were taken with deuteron targets, so we do not know the initial state of the neutron (binding, Fermi motion effects, and nucleon off- shellness …). “spectator tagging” technique may help 5 tesla magnetic filed point to the opposite direction to the beam line. Placed inside the center of Hall-B to work conjugate with CLAS. BoNuS Experiment W = (m n 2 + 2m n  - Q 2 ) 1/2 q 2 = -Q 2 = 4  ′sin 2 (  e /2)  * = angle between the emitted  - and the virtual photon in the CM frame  * = angle between the leptonic and hadronic scattering planes  q ** **  n pp Hadronic plane  ’,k ’ ,k Leptonic plane 3200 channels Sensitive to protons with momenta of 67-250 Mev/c Particle ID by dE/dx (charge/track_length) Helium/DME at 80/20 ratio 140 µm 3-D tracking: time of drift -> r pad position -> , z dE/dX FSI in Spectator Tagging Ciofi degli Atti and Kopeliovich, Eur. Phys. J. A17(2003)133 For low spectator momenta, ps 120 o ) are quite small, ≤ 5%, for both models. Require the low Ps and large θ pq allow us to ignore the FSI. The red lines in the left figure show the drift path of each ionization electron that would appear on a given channel. In green is the spatial reconstruction of where the ionization took place. The figures on the right show various views of an event reconstructed in three dimensions. Hits which are close to each other in space are linked together and fit to a helical trajectory. This resulting helix tells us the vertex position and the initial three momentum of the particle. The blue curve is fit to the simulated hits; the red curve is fit to the reconstructed hits. Simulation Jefferson Lab Experiment E03-012 Barely off-shell Nucleon Structure Electron beam energies: 2.1, 4.2, 5.3 GeV Spectator protons were detected by the newly built Radial Time Projection Chamber (RTPC), other particles were detected by CEBAF Large Acceptance Spectrometer (CLAS) Target: 7 atm deuterium gas Data were taken from Sep. to Dec. in 2005 Both CLAS and RTPC calibration completed ① Quality checks completed ② CLAS Fiducial region for electrons defined Electron and   identification defined ② Target contaminations studied Beam line (position) and correction is ready ② Energy loss corrections for CLAS particles and RTPC proton base on simulation are ready ② Momentum correction is ready Acceptance correction is ongoing …… ② More simulation is running…… ② ① Only the EC time calibration is my contribution ② My major contribution Current Status A MAGBOLTZ simulation of the crossed E and B fields, together with the drift gas mixture, determines the drift path and the drift velocity of the electrons. Electrons measured by CLAS and in RTPC Public in NIM-A. doi:10.1016/j.nima.208.04.047 W (GeV) Q 2 (GeV 2 ) cos(θ pq ) Ps (MeV) Kinematic Coverage RTPC effectively reconstructed and identified slow protons Spectator tagging technique works RTPC can save 20% more date for exclusive  - channel D(e, e   p)p D(e, e   p CLAS )p s D(e, e   p RTPC )p CLAS N(1520)D13, N(1535)S11  (1620)S31, N(1650)S11, N(1675)D15, N(1680)D15,  (1700)D33, N(1720)P13  (1232)P33 Baryonic Resonances D(e,e  - p)p E = 5.262 GeV preliminary e p n E = 4.223 GeV = 1.19 (GeV/c) 2 preliminary FC