Multiparticle Production in Strong Interactions
(2003) Abstract
 An alternative formulation of the Lund fragmentation model for string states without gluons is presented. It is shown that the fragmentation process can be factorised into a product of transition operators with welldefined eigenfunctions and corresponding eigenvalues. The physical properties of these functions are studied and possible applications are suggested.
A fragmentation model for multigluon strings is defined and investigated in detail. The model fulfils the Lund area law on an event to event basis and it is formulated in a way which makes it suitable for a Monte Carlo implementation. A Monte Carlo fragmentation program, called ALFS, based upon this exact implementation of the Lund area law is analysed and... (More)  An alternative formulation of the Lund fragmentation model for string states without gluons is presented. It is shown that the fragmentation process can be factorised into a product of transition operators with welldefined eigenfunctions and corresponding eigenvalues. The physical properties of these functions are studied and possible applications are suggested.
A fragmentation model for multigluon strings is defined and investigated in detail. The model fulfils the Lund area law on an event to event basis and it is formulated in a way which makes it suitable for a Monte Carlo implementation. A Monte Carlo fragmentation program, called ALFS, based upon this exact implementation of the Lund area law is analysed and compared with the PYTHIA event generator. We find that inclusive distributions are the same but that there are differences on an event to event basis.
We demonstrate that the hadrons produced in this model can be grouped into (almost) planar regions in momentum space called Coherence Chains. A qualitative study of the properties of the Coherence Chains is performed using the above mentioned ALFS Monte Carlo fragmentation program. We find that the distribution in the number of hadrons in a Coherence Chain has stability properties which allows us to base a model for the BoseEinstein effect upon the concept of Coherence Chains. The two particle correlation function for 2, 3 and 4 jet events is studied.
The thesis also contains a phenomenological investigation of a set of distributions obtained from the perturbative QCD parton cascades as they are implemented in the Monte Carlo event generators ARIADNE and PYTHIA. In an analysis built upon a generalised rapidity range, we observe a set of independent entities, that we call Generalised Dipoles. In the Lund model, the Generalised Dipoles correspond to connected plaquettes along a surface characteristic to the string state. We demonstrate that there is a close relationship between the Generalised Dipoles and the above mentioned Coherence Chains. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/465715
 author
 Söderberg, Fredrik ^{LU}
 supervisor
 opponent

 Prof Csörgö, Tamas, H1525 BudapestHUNGARY
 organization
 publishing date
 2003
 type
 Thesis
 publication status
 published
 subject
 keywords
 Hadronisation, QCD, BoseEinstein correlations, Elementary particle physics, Elementarpartikelfysik, quantum field theory, String fragmentation, kvantfältteori, Fysicumarkivet A:2003:Söderberg
 pages
 157 pages
 publisher
 Department of Theoretical Physics, Lund University
 defense location
 Lecture Hall F, Dept. of Theoretical Physics
 defense date
 20030509 10:30:00
 ISBN
 9162855948
 language
 English
 LU publication?
 yes
 id
 0795c6d60a784bc4937e1c792110798e (old id 465715)
 date added to LUP
 20160404 09:54:10
 date last changed
 20181121 20:55:36
@phdthesis{0795c6d60a784bc4937e1c792110798e, abstract = {An alternative formulation of the Lund fragmentation model for string states without gluons is presented. It is shown that the fragmentation process can be factorised into a product of transition operators with welldefined eigenfunctions and corresponding eigenvalues. The physical properties of these functions are studied and possible applications are suggested.<br/><br> <br/><br> A fragmentation model for multigluon strings is defined and investigated in detail. The model fulfils the Lund area law on an event to event basis and it is formulated in a way which makes it suitable for a Monte Carlo implementation. A Monte Carlo fragmentation program, called ALFS, based upon this exact implementation of the Lund area law is analysed and compared with the PYTHIA event generator. We find that inclusive distributions are the same but that there are differences on an event to event basis.<br/><br> <br/><br> We demonstrate that the hadrons produced in this model can be grouped into (almost) planar regions in momentum space called Coherence Chains. A qualitative study of the properties of the Coherence Chains is performed using the above mentioned ALFS Monte Carlo fragmentation program. We find that the distribution in the number of hadrons in a Coherence Chain has stability properties which allows us to base a model for the BoseEinstein effect upon the concept of Coherence Chains. The two particle correlation function for 2, 3 and 4 jet events is studied.<br/><br> <br/><br> The thesis also contains a phenomenological investigation of a set of distributions obtained from the perturbative QCD parton cascades as they are implemented in the Monte Carlo event generators ARIADNE and PYTHIA. In an analysis built upon a generalised rapidity range, we observe a set of independent entities, that we call Generalised Dipoles. In the Lund model, the Generalised Dipoles correspond to connected plaquettes along a surface characteristic to the string state. We demonstrate that there is a close relationship between the Generalised Dipoles and the above mentioned Coherence Chains.}, author = {Söderberg, Fredrik}, isbn = {9162855948}, language = {eng}, publisher = {Department of Theoretical Physics, Lund University}, school = {Lund University}, title = {Multiparticle Production in Strong Interactions}, year = {2003}, }