The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Reconstruction of B Hadron Decays at DELPHI

Laura Salmi

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Auditorium F1 at Helsinki University of Technology (Espoo, Finland) on the 24th of March, 2006, at 12 o'clock noon.

Overview in PDF format (ISBN 952-10-1698-1)   [892 KB]
Dissertation is also available in print (ISBN 952-10-1697-3)

Abstract

This thesis describes three analyses related to heavy quarks.

The analysis with the largest impact is the extraction of parameters of heavy quark decays using the lepton energy spectrum and the hadronic mass spectrum in semileptonic B decays. The extraction of the parameters allows to test the framework used to theoretically describe the decay of heavy mesons, and more accurate knowledge of the parameter values results in greater accuracy in the determination of the element |Vcb| of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. The determination described in this thesis is important, since it is so far the only one where the full lepton energy spectrum has been used. The other determinations are based on using only a part of the spectrum. The first extraction of the parameters in the kinetic mass scheme was based on the statistical moments of the lepton energy spectrum and hadronic mass spectrum measured using the data collected at DELPHI.

In the second analysis, the angular distribution of fragmentation particles in Z → bb̅ and Z → cc̅ events was studied using the DELPHI data. The analysis gave the first direct experimental evidence of the dead cone effect, or the depletion of fragmentation particles at small emission angles, predicted by perturbative quantum chromodynamics.

The third analysis is a simulation study of top quark pair production at a possible future e+e− linear collider with a 3 TeV center-of-mass energy. The study allowed to estimate the accuracies with which the cross-section and forward-backward asymmetry could be measured.

This thesis consists of an overview and of the following 7 publications:

  1. J. Abdallah et al. with L. Salmi (The DELPHI collaboration), Determination of heavy quark non-perturbative parameters from spectral moments in semileptonic B decays, The European Physical Journal C 45 (2006) 35-59. © 2006 by authors and © 2006 Springer Science+Business Media. By permission.
  2. M. Battaglia, M. Calvi, P. Gambino, A. Oyanguren, P. Roudeau, L. Salmi, J. Salt, A. Stocchi, and N. Uraltsev, Heavy quark parameters and |Vcb| from spectral moments in semileptonic B decays, Physics Letters B 556 (2003) 41-49. © 2003 Elsevier Science. By permission.
  3. L. Salmi on behalf of the DELPHI collaboration, OPE parameter determinations from semileptonic B decays at DELPHI, Nuclear Physics B (Proceedings Supplement) 142 (2005) 167-172. © 2005 Elsevier Science. By permission.
  4. M. Battaglia, M. Calvi, and L. Salmi, A study of the lepton spectrum moments in b → Xcℓ ν̅ decays with the DELPHI detector at LEP, DELPHI 2002-071 CONF 605, Contributed paper to the 31st International Conference on High Energy Physics (ICHEP 2002), Amsterdam, Netherlands, 24-31 July 2002. © 2002 by authors.
  5. L. Salmi on behalf of the DELPHI collaboration, Recent b physics results from DELPHI, Nuclear Physics B (Proceedings Supplement) 133 (2004) 133-136. © 2004 Elsevier Science. By permission.
  6. M. Battaglia, R. Orava, and L. Salmi, A study of depletion of fragmentation particles at small angles in b-jets with the DELPHI detector at LEP, DELPHI 2004-037 CONF 712, Contributed paper to the 32nd International Conference on High Energy Physics (ICHEP 2004), Beijing, China, 16-22 August 2004. © 2004 by authors.
  7. L. Salmi, tt̅ cross-section and forward-backward asymmetry at CLIC, In: J. S. Kang and S. K. Oh (editors), Proceedings of the International Workshop on Linear Colliders (LCWS 2002), Jeju, Korea, 26-30 August 2002, pp. 310-314. © 2002 Korean Physical Society. By permission.

Keywords: heavy quark expansion, Cabibbo-Kobayashi-Maskawa matrix, semileptonic B decays

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© 2006 Helsinki University of Technology

Last update 2011-05-26