On Extracting Hadron Multiplicities and Unpolarized Nucleon Structure Ratios From SIDIS Data at the HERMES Experiment

139 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.We present an analysis using the world's largest data set of semi-inclusive deep inelastic scattering (SIDIS) in the kinematic range 0.1 < x < 0.6 at an average Q2 of 2.5 GeV2. This data was collected at the HERMES experiment located in the east hall of the HERA accelerator between the years 2000 and 2006. The hadron multiplicity from these scattering events is extracted for identified charged pions, kaons and protons from two different gaseous targets (H & D). For the hydrogen (deuterium) target 12.5 (16.68) million events were recorded. Using these hadron multiplicities an attempt is made to extract unpolarized information about the parton momentum distribution functions (PDFs) inside the nucleon via the flavor tagging technique within the quark-parton model. In particular, one can exploit certain factorization assumptions and fragmentation symmetries to extract the valence quark ratio dv/ uv and the light sea asymmetry d -- u/(u -- d) from the measured pion multiplicities on hydrogen and deuterium targets. The excellent particle identification available in the HERMES spectrometer coupled with the overwhelming statistics that are available from the high density end-of-fill running (especially in 2002 and 2004) make the HERMES data invaluable for reinforcing the E866/NuSea Drell-Yan result on d/ u at a different &lang;Q 2&rang; and from an entirely different physical process. These PDF extractions are also an important test of many typical assumptions made in SIDIS analyses and must be taken into consideration in light of the future facilities that propose to use this technique.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD