Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Electromagnetic form factors of the Sigma*-Lambda transition
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

We introduce and examine the analytic properties of the three electromagnetic transition form factors of the Sigma*-Lambda hyperon transition. In the first part of the thesis, we discuss the interaction Lagrangian for the hyperons at hand. We calculate the decay rate of the Dalitz decay  Sigma* Lambda -> e+e- in the one-photon approximation in terms of the form factors, as well as the differential cross section of the scattering e+e- -> Sigma*bar Lambda in the one-photon approximation. In the second part of the thesis, we build up the machinery for calculation of the form factors using dispersion relations, performing an analytic continuation from the timelike, q2 > 0, to the spacelike, q2 < 0, region of the virtual photon invariant mass q2. Due to an anomalous cut in the triangle diagram arising from a two-pion saturation of the photon-hyperon vertex, there is an additional term in the dispersive integral. We use the scalar three-point function as a model for the examination of the dispersive approach with the anomalous cut. The one-loop diagram is calculated both directly and using dispersion relations. After comparison of the two methods, they are found to coincide when the anomalous contribution is added to the dispersive integral in the case of the octet Sigma exchange. By examination of the branch points of the logarithm in the discontinuity, we deduce the structure of the Riemann surface of the unitarity cut and present trajectories of the branch points. The result of our analysis of the analytic structure yields a correct dispersive relation for the electromagnetic transition form factors. This opens the way for the calculation of these form factors in the low-energy region for both space- and timelike q2. As an outlook, we present preliminary calculations for the hyperon-pion scattering amplitude using the unitarity and the anomalous contribution in a once-subtracted dispersion relation. Finally we present the corresponding preliminary unsubtracted dispersive calculations for the form factors.

Place, publisher, year, edition, pages
2019. , p. 136
Series
FYSAST ; FYSMAS1099
Keywords [en]
hyperon form factors, dispersion relations, anomalous cuts
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-392236OAI: oai:DiVA.org:uu-392236DiVA, id: diva2:1347579
Educational program
Master Programme in Physics
Supervisors
Examiners
Available from: 2019-09-06 Created: 2019-09-01 Last updated: 2019-09-06Bibliographically approved

Open Access in DiVA

fulltext(4196 kB)21 downloads
File information
File name FULLTEXT01.pdfFile size 4196 kBChecksum SHA-512
c10a3accec92c571dccbb6cbf35531f61d070b606e98f69c4510f84dd3081e8fce10a963ed0657579127951f4f84c8479a5fefffbce56387b0f9c3508d663517
Type fulltextMimetype application/pdf

By organisation
Nuclear Physics
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 21 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 108 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf