Measurement Of The π~0 Inclusive Cross Section In Ep Scattering And The Design Of Electromagnetic Calorimeter For SoLID Program At Jefferson Lab

One of the key goals in high-and medium-energy hadronic physics is to study the in-ternal structure of the nucleon and to understand how QCD works in the non-perturbation region.The subatomic structure of the nucleon remains a frontier topic in hadronic physics research.The goal of the nucleon structure study is to understand how quarks and gluons form the nucleon’s energy/momentum and its spin.For this topic,the pri-mary experiment tool used is electron scattering from a nucleon or a light-nuclear target.Recently,as advancement in electron scattering and in experimental setup that can al-low higher and higher statistics,understanding the nucleon structure has advanced from extracting the momentum-dependent（1D）PDF to a more comprehensive view:the 3D structure of the nucleon.Semi-inclusive deep inelastic scattering（SIDIS）is used as the main experimental tool to access the nucleon 3D structure functions such as transverse-momentum distribution（TMD）functions.In studying the internal structure of the nucleon,one of the frontier facility world-wide is Thomas Jefferson National Accelerator Facility,or Jefferson Lab（JLab）,lo-cated in Newport News,Virginia.Electron scattering is a unique tool in subatomic physics study,providing unambiguous information on the nucleon structure that cannot be achieved by other methods such as hadron-hadron collisions or pure leptonic reactions.The superconducting continuous-wave electron accelerator at JLab provides the highest electron-scattering luminosity of the world.Its luminosity can reach up to 1039 cm-2s-1 for unpolarized targets,and up to 1036 cm-2s-1 for polarized-target experiments.In ad-dition,JLab has just completed its upgrade and can now provide up to 11 GeV in beam energy to 3 of the 4 experimental halls（A,B and C）,and up to 12 GeV to experimental Hall D.The high luminosity and this recent energy upgrade of JLab has made it possible to provide high-precision data in unprecedented areas.A high-intensity,large-acceptance spectrometer called SoLID（Solenoid Large Inten-sity Device）is planned for JLab’s experimental Hall A,which contain three main physics programs:Semi-Inclusive Deep Inelastic Scattering（SIDIS）,Parity-Violating Deep In-elastic Scattering（PVDIS）and J/ψ program.This dissertation contains two main topics,both are central to the SoLID program at JLab.The first topic is a measurement of the π0 inclusive cross section in e+p scattering process,where the photons decayed from π0 are the important background in SoLID experiment.The second topic is to research and design one shashlik-type electromagnetic calorimeter（ECal）for SoLID experiment.The DVCS（Deeply Virtual Compton Scattering）experiment E12-06-114 of JLab is one of initial experiments after 12 GeV upgrade in Hall A.Due to no special π0 cross sec-tion experiment,this E12-06-114 experiment,including kinematic configuration kin48₂,kin48₃,kin48₄,is used to measure the inclusive π0 cross section in this dissertation.Thanks to the DIS（Deep Inelastic Scatter）trigger mode and ARS（Analog Ring Sampler）digitizer of the calorimeter used this experiment,the inclusive π0 events can be extracted from ARS recorded which anti-coincidence with LHRS electron trigger signal.The Monte Carlo event generator of SoLID is a modifier generator of Hall D at JLab.The π0 yield in the process of electron colliding with liquid Hydrogen target was simulated with this generator.The π0 events yield are measured in energy bin from 1 GeV to 8 GeV and each polar angle bin from 8 degree to 20 degree at 8.5 GeV and 11 GeV beam energy.The π0 cross section of measured result are derived by comparing with the simulation results.This scale factor from comparison will be used to fix the generator simulation π0 production in the future SoLID experiment.The second work is to study the design of electromagnetic calorimeter（ECal）for SoLID spectrometer.SoLID’s ECal will utilize a new sampling technique called the"shashlik" design,in which each module is made of 194 each of 0.5mm-thick lead and 1.5mm-thick scintillator layers.The light signal is guided out by wavelength-shifting（WLS）fibers penetrating through all layers through pre-drilled holes.The light of the module was guided into one photomultiplier tube by the fiber and transfered to electronic signal.Such technique provides a good balance between particle ID capability,energy resolution,radiation hardness,and cost.Total 2000 modules will be built as plan,which will be an onerous work.The energy resolution of ECal is greatly influenced by the statistics of light yield,and the design study in this dissertation is mostly focus on the improvement of light yield.We studied the material selection,light collection,machining process and the assembly.A few prototypes of this shashlik ECal have been assembled with varied scintillator material,fiber type,fiber end mirror,reflector layer and package layer.To measure the light yield,few testing system was built for testing the performance of the PMT and the light yield of ECal prototype.In this dissertation,from chapter 2 to 6 will describe the inclusive π0 cross section measurement work,the chapter from 7 to 10 is the design and test of SoLID ECal.