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Transverse Spin Structure of the Proton Studied in Semi–inclusive DIS

(2006)
Author
Promoter
D Ryckbosch
Organization
Abstract
The quark structure of the nucleon can be described by three fundamental quark distributions: the quark number density (giving the probability to find a quark with a certain momentum inside the nucleon), the quark helicity distribution and the quark transversity distribution. The latter two are the differences of the number of quarks with their spins aligned and antialigned with the nucleon spin whose direction is longitudinal or respectively transversal to its momentum. The first two distributions have been measured extensively in the past. The transversity distribution, however, has escaped experimental attention because of its chiral-odd nature which prevents its determination in purely inclusive measurements. In order to access the transversity distribution, it has to couple to a chiral-odd object, e.g., to the so-called Collins fragmentation function in semi-inclusive deep-inelastic scattering (DIS). This gives rise to a left-right asymmetry in the cross-section for a transversely polarised nucleon. Another source of an azimuthal single-spin asymmetry is the so-called Sivers effect which stems from an asymmetry in the unpolarised quark distribution of a transversely polarised nucleon. A non-vanishing Sivers distribution function requires orbital angular momentum of the quarks. Although the direct connection between them has not yet been established, there is the hope that a measurement of the Sivers function will ultimately lead to constraints of orbital angular momentum of the quarks -- an important piece of the nucleon's spin puzzle. The HERMES experiment at DESY has been taking data with a transversely polarised proton target since 2002. This PhD work covers the analysis of the HERMES data recorded in the years 2002 through 2004 including extensive systematic studies. In addition, several Monte Carlo generators have been used for the estimation of systematic uncertainties. With the measured asymmetries it is possible to estimate the ratio of disfavoured to favoured Collins functions and to extract for the first time the Sivers function.

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MLA
Elschenbroich, Ulrike. Transverse Spin Structure of the Proton Studied in Semi–Inclusive DIS. 2006, doi:1854/4208.
APA
Elschenbroich, U. (2006). Transverse Spin Structure of the Proton Studied in Semi–inclusive DIS. https://doi.org/1854/4208
Chicago author-date
Elschenbroich, Ulrike. 2006. “Transverse Spin Structure of the Proton Studied in Semi–Inclusive DIS.” https://doi.org/1854/4208.
Chicago author-date (all authors)
Elschenbroich, Ulrike. 2006. “Transverse Spin Structure of the Proton Studied in Semi–Inclusive DIS.” doi:1854/4208.
Vancouver
1.
Elschenbroich U. Transverse Spin Structure of the Proton Studied in Semi–inclusive DIS. 2006.
IEEE
[1]
U. Elschenbroich, “Transverse Spin Structure of the Proton Studied in Semi–inclusive DIS,” 2006.
@phdthesis{469947,
  abstract     = {{The quark structure of the nucleon can be described by three fundamental quark distributions: the quark number density (giving the probability to find a quark with a certain momentum inside the nucleon), the quark helicity distribution and the quark transversity distribution. The latter two are the differences of the number of quarks with their spins aligned and antialigned with the nucleon spin whose direction is longitudinal or respectively transversal to its momentum. The first two distributions have been measured extensively in the past. The transversity distribution, however, has escaped experimental attention because of its chiral-odd nature which prevents its determination in purely inclusive measurements. In order to access the transversity distribution, it has to couple to a chiral-odd object, e.g., to the so-called Collins fragmentation function in semi-inclusive deep-inelastic scattering (DIS). This gives rise to a left-right asymmetry in the cross-section for a transversely polarised nucleon. Another source of an azimuthal single-spin asymmetry is the so-called Sivers effect which stems from an asymmetry in the unpolarised quark distribution of a transversely polarised nucleon. A non-vanishing Sivers distribution function requires orbital angular momentum of the quarks. Although the direct connection between them has not yet been established, there is the hope that a measurement of the Sivers function will ultimately lead to constraints of orbital angular momentum of the quarks -- an important piece of the nucleon's spin puzzle. The HERMES experiment at DESY has been taking data with a transversely polarised proton target since 2002. This PhD work covers the analysis of the HERMES data recorded in the years 2002 through 2004 including extensive systematic studies. In addition, several Monte Carlo generators have been used for the estimation of systematic uncertainties. With the measured asymmetries it is possible to estimate the ratio of disfavoured to favoured Collins functions and to extract for the first time the Sivers function.}},
  author       = {{Elschenbroich, Ulrike}},
  language     = {{und}},
  school       = {{Ghent University}},
  title        = {{Transverse Spin Structure of the Proton Studied in Semi–inclusive DIS}},
  url          = {{http://dx.doi.org/1854/4208}},
  year         = {{2006}},
}

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