{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:77"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:77","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Extraction of Polarised Quark Distributions of the Nucleon from Deep Inelastic Scattering at the HERMES Experiment","abstract":"This thesis reports on the measurement of polarised quark
distributions of the nucleon from deep inelastic polarised
positron-proton scattering in the HERMES experiment at DESY.
The first part of this thesis describes the achievement and
measurement of longitudinal positron polarisation in the HERA
storage ring, using Compton scattering of polarised laser light.
Emphasis is laid on the setup and performance of the laser
optical system of the so-called 'Longitudinal Polarimeter'.
In the second part of this thesis, polarised quark distributions
for up-, down-, and sea-quarks are extracted from the analysis
of semi inclusive cross section asymmetries in deep inelastic
scattering. The data cover a kinematic range of
0.023 < x < 0.6 and 1.0 GeV^2 < Q^2 < 10 GeV^2. Polarised quark
distributions are extracted as a function of Bjorken-x for the
up-, down-, and sea-flavours, as well as for the valence up-,
valence down-, and sea-flavours. The polarisation of the
up-quarks was determined to be positive in the entire kinematic
range and increases up to a value of approximately 0.5 for large
values of x. Similarly, the down-quarks show negative polarisation,
whereas the sea-quarks carry no significant polarisation in the
measured range. Furthermore, the first and second moments of the
extracted polarised quark distributions are determined and
compared to existing analyses of world data on inclusive
polarised deep inelastic scattering and to QCD lattice
calculations. The extracted moments are consistent with the
analyses of the inclusive scattering data assuming SU(3) flavour
symmetry for the polarised quark distributions in the nucleon,
whereas there is a clear discrepancy to the results of the
lattice QCD calculations.","abstract_html":"This thesis reports on the measurement of polarised quark <br>distributions of the nucleon from deep inelastic polarised <br>positron-proton scattering in the HERMES experiment at DESY. <br> <br>The first part of this thesis describes the achievement and <br>measurement of longitudinal positron polarisation in the HERA <br>storage ring, using Compton scattering of polarised laser light. <br>Emphasis is laid on the setup and performance of the laser <br>optical system of the so-called 'Longitudinal Polarimeter'. <br> <br>In the second part of this thesis, polarised quark distributions <br>for up-, down-, and sea-quarks are extracted from the analysis <br>of semi inclusive cross section asymmetries in deep inelastic <br>scattering. The data cover a kinematic range of <br>0.023 < x < 0.6 and 1.0 GeV^2 < Q^2 < 10 GeV^2. Polarised quark <br>distributions are extracted as a function of Bjorken-x for the <br>up-, down-, and sea-flavours, as well as for the valence up-, <br>valence down-, and sea-flavours. The polarisation of the <br>up-quarks was determined to be positive in the entire kinematic <br>range and increases up to a value of approximately 0.5 for large <br>values of x. Similarly, the down-quarks show negative polarisation, <br>whereas the sea-quarks carry no significant polarisation in the <br>measured range. Furthermore, the first and second moments of the <br>extracted polarised quark distributions are determined and <br>compared to existing analyses of world data on inclusive <br>polarised deep inelastic scattering and to QCD lattice <br>calculations. The extracted moments are consistent with the <br>analyses of the inclusive scattering data assuming SU(3) flavour <br>symmetry for the polarised quark distributions in the nucleon, <br>whereas there is a clear discrepancy to the results of the <br>lattice QCD calculations.","abstract_has_math":false,"creators":["Beckmann, Marc"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Königsmann, Kay"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:21:24Z","subjects":["polarisierte Quarkdichteverteilungen","polarisierte Lepton-Nukleon-Streuung","deep inelastic scattering","polarised quark distribution","nucleon"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/77","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Königsmann, Kay"]},{"key":"dc:creator","label":"Author","values":["Beckmann, Marc"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["polarisierte Quarkdichteverteilungen","polarisierte Lepton-Nukleon-Streuung","deep inelastic scattering","polarised quark distribution","nucleon"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This thesis reports on the measurement of polarised quark
distributions of the nucleon from deep inelastic polarised
positron-proton scattering in the HERMES experiment at DESY.
The first part of this thesis describes the achievement and
measurement of longitudinal positron polarisation in the HERA
storage ring, using Compton scattering of polarised laser light.
Emphasis is laid on the setup and performance of the laser
optical system of the so-called 'Longitudinal Polarimeter'.
In the second part of this thesis, polarised quark distributions
for up-, down-, and sea-quarks are extracted from the analysis
of semi inclusive cross section asymmetries in deep inelastic
scattering. The data cover a kinematic range of
0.023 < x < 0.6 and 1.0 GeV^2 < Q^2 < 10 GeV^2. Polarised quark
distributions are extracted as a function of Bjorken-x for the
up-, down-, and sea-flavours, as well as for the valence up-,
valence down-, and sea-flavours. The polarisation of the
up-quarks was determined to be positive in the entire kinematic
range and increases up to a value of approximately 0.5 for large
values of x. Similarly, the down-quarks show negative polarisation,
whereas the sea-quarks carry no significant polarisation in the
measured range. Furthermore, the first and second moments of the
extracted polarised quark distributions are determined and
compared to existing analyses of world data on inclusive
polarised deep inelastic scattering and to QCD lattice
calculations. The extracted moments are consistent with the
analyses of the inclusive scattering data assuming SU(3) flavour
symmetry for the polarised quark distributions in the nucleon,
whereas there is a clear discrepancy to the results of the
lattice QCD calculations."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Extraction of Polarised Quark Distributions of the Nucleon from Deep Inelastic Scattering at the HERMES Experiment"]}]}],"canonical_facts":{"dc:contributor":["Königsmann, Kay"],"dc:creator":["Beckmann, Marc"],"dc:description.abstract":["This thesis reports on the measurement of polarised quark
distributions of the nucleon from deep inelastic polarised
positron-proton scattering in the HERMES experiment at DESY.
The first part of this thesis describes the achievement and
measurement of longitudinal positron polarisation in the HERA
storage ring, using Compton scattering of polarised laser light.
Emphasis is laid on the setup and performance of the laser
optical system of the so-called 'Longitudinal Polarimeter'.
In the second part of this thesis, polarised quark distributions
for up-, down-, and sea-quarks are extracted from the analysis
of semi inclusive cross section asymmetries in deep inelastic
scattering. The data cover a kinematic range of
0.023 < x < 0.6 and 1.0 GeV^2 < Q^2 < 10 GeV^2. Polarised quark
distributions are extracted as a function of Bjorken-x for the
up-, down-, and sea-flavours, as well as for the valence up-,
valence down-, and sea-flavours. The polarisation of the
up-quarks was determined to be positive in the entire kinematic
range and increases up to a value of approximately 0.5 for large
values of x. Similarly, the down-quarks show negative polarisation,
whereas the sea-quarks carry no significant polarisation in the
measured range. Furthermore, the first and second moments of the
extracted polarised quark distributions are determined and
compared to existing analyses of world data on inclusive
polarised deep inelastic scattering and to QCD lattice
calculations. The extracted moments are consistent with the
analyses of the inclusive scattering data assuming SU(3) flavour
symmetry for the polarised quark distributions in the nucleon,
whereas there is a clear discrepancy to the results of the
lattice QCD calculations."],"dc:format.medium":["application/pdf"],"dc:subject":["polarisierte Quarkdichteverteilungen","polarisierte Lepton-Nukleon-Streuung","deep inelastic scattering","polarised quark distribution","nucleon"],"dc:title":["Extraction of Polarised Quark Distributions of the Nucleon from Deep Inelastic Scattering at the HERMES Experiment"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:21:24Z"}