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Study of Two-Photon processes at low Q2 using the VSAT calorimeter in the DELPHI experiment

Tyapkin, Pavel LU (2004)
Abstract (Swedish)
Popular Abstract in Swedish

Studie av Två-Fotons processer vid låg Q<sup>2</sup> med hjälp av VSAT kalorimetern i DELPHI experimentet



Den här studien är baserad på data som har insamlats med hjälp av LEP (Large Electron-Positron) acceleratorn under dess andra tidsperioden LEP II (1996-2000) då strålenergin uppgick till 103-104 GeV. Under den perioden insamlades vid DELPHI (DEtector with Lepton, Photon and Hadron Identification) ungefär 90 Gb data, motsvarande till 687-691 pb<sup>-1</sup> i luminositet.



Data från VSAT (Very Small Angle Tagger) elektromagnetisks kalorimetern lagrades separat och användes av VSAT-gruppen till luminositets mätningar och till... (More)
Popular Abstract in Swedish

Studie av Två-Fotons processer vid låg Q<sup>2</sup> med hjälp av VSAT kalorimetern i DELPHI experimentet



Den här studien är baserad på data som har insamlats med hjälp av LEP (Large Electron-Positron) acceleratorn under dess andra tidsperioden LEP II (1996-2000) då strålenergin uppgick till 103-104 GeV. Under den perioden insamlades vid DELPHI (DEtector with Lepton, Photon and Hadron Identification) ungefär 90 Gb data, motsvarande till 687-691 pb<sup>-1</sup> i luminositet.



Data från VSAT (Very Small Angle Tagger) elektromagnetisks kalorimetern lagrades separat och användes av VSAT-gruppen till luminositets mätningar och till gamma-gamma (två-fotonens) fysik analyser av foton-foton kollisioner.



Dessa analyser är inriktad på en- och två- fotonsbetecknad fall (single and double tag events) som sislar med en eller två fotoner registrerad i VSAT efter kollision. Tre Monte Carlo simulationserier utvecklades för perioden 1998-2000 med hjälp av tre olika generatorprogram (PYTHIA, PHOJET och TWOGAM). Studier av gamma-gamma fysik vid så höga energier (från 189 till 206 GeV i tyngdpunktssystemet) och så små polar vinklar av fotoner (3-12 milliradians) är ganska unika i det här området av högenergifysik.



Bakgrund och strål villkor som har påverkat denna analys har studerats för att få så "ren" signal med så liten bakgrund som möjligt. Förbättring och uppdatering av mjukvaran i VSAT datasystem och en del av hårdvara problem på grund av ålder och kraftig strålning från LEP diskuteras också i den här avhandlingen. (Less)
Abstract
The study is based on data collected at the LEP II accelerator during the second period of the Large Electron-Positron collider operations (1996-2000). During that time the DELPHI (DEtector with Lepton, Photon and Hadron Identification) experiment collected about 90 Gb of data on tape corresponding to 687-691 pb<sup>-1</sup> of luminosity.



The data obtained by the VSAT (Very Small Angle Tagger) electromagnetic calorimeter was stored and used for luminosity measurements and for gamma-gamma physics analysis.



The analysis was concentrated on single and double tag events. Three Monte Carlo sets were generated for years 1998-2000 using three different generators (PYTHIA, PHOJET and TWOGAM).... (More)
The study is based on data collected at the LEP II accelerator during the second period of the Large Electron-Positron collider operations (1996-2000). During that time the DELPHI (DEtector with Lepton, Photon and Hadron Identification) experiment collected about 90 Gb of data on tape corresponding to 687-691 pb<sup>-1</sup> of luminosity.



The data obtained by the VSAT (Very Small Angle Tagger) electromagnetic calorimeter was stored and used for luminosity measurements and for gamma-gamma physics analysis.



The analysis was concentrated on single and double tag events. Three Monte Carlo sets were generated for years 1998-2000 using three different generators (PYTHIA, PHOJET and TWOGAM). Gamma-gamma physics at such high energies (189-206 GeV in the c.m.s.) and small polar angles (3-12 mrad) is unique.



Background and beam conditions influenced the analysis and were studied in order to obtain a "clean" signal with as little background as possible. The total hadronic cross-sections for different invariant mass were estimated. The upgrade of the VSAT data-taking software and some hardware problems due to aging were also discussed.



The articles in the Appendices are connected with VSAT data-taking and the two-photon physics analysis.



Appendix A, is the VSAT status report with estimation of VSAT performance for higher energies. The situation with the VSAT detector hardware and software upgrades are explained in the article.



Appendix B, was written during the summer of 1999. The main subject of the article is the background condition in VSAT, STIC and other calorimeters. Some effective methods of removing background are proposed for each of the DELPHI calorimeters.



Appendix C, describes problems of the long-time radiation damage and the short periods of high background which caused an increase of the bias currents in the VSAT modules.



Appendix D, summarizes all beam parameters changes, position shifts of the VSAT modules observed by geometrical surveys and consequences of that during LEP II period.



Appendix E, is devoted to the two-photons physics analysis of the DELPHI - VSAT data. The final analysis of two-photon events in double and single tag modes is presented. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Grafström, Per, CERN, CH-1211 Geneva 23, Switzerland
organization
publishing date
type
Thesis
publication status
published
subject
keywords
högenergi, QCD, STIC, VSAT, DELPHI, LEP, antitag, double tag, single tag, photon structure function, hadronic cross-section, virtual photons, two-photon, gamma-gamma, Kosmisk strålning, cosmic rays, High energy interactions, PHOJET, TWOGAM, PYTHIA, VDM, GSP, Fysicumarkivet A:2004:Tyapkin
pages
190 pages
publisher
Lund University
defense location
Hall F of the Department of Physics (Theoretical division building, 2nd floor)
defense date
2004-09-17 15:15
external identifiers
  • Other:LUNFD6/(NFFL-7221) 2004
ISBN
91-628-6168-9
language
English
LU publication?
yes
id
bd96fc89-c4f9-4fff-9b45-a4c10838f1de (old id 467214)
date added to LUP
2007-08-09 11:40:49
date last changed
2016-09-19 08:45:14
@misc{bd96fc89-c4f9-4fff-9b45-a4c10838f1de,
  abstract     = {The study is based on data collected at the LEP II accelerator during the second period of the Large Electron-Positron collider operations (1996-2000). During that time the DELPHI (DEtector with Lepton, Photon and Hadron Identification) experiment collected about 90 Gb of data on tape corresponding to 687-691 pb&lt;sup&gt;-1&lt;/sup&gt; of luminosity.<br/><br>
<br/><br>
The data obtained by the VSAT (Very Small Angle Tagger) electromagnetic calorimeter was stored and used for luminosity measurements and for gamma-gamma physics analysis.<br/><br>
<br/><br>
The analysis was concentrated on single and double tag events. Three Monte Carlo sets were generated for years 1998-2000 using three different generators (PYTHIA, PHOJET and TWOGAM). Gamma-gamma physics at such high energies (189-206 GeV in the c.m.s.) and small polar angles (3-12 mrad) is unique.<br/><br>
<br/><br>
Background and beam conditions influenced the analysis and were studied in order to obtain a "clean" signal with as little background as possible. The total hadronic cross-sections for different invariant mass were estimated. The upgrade of the VSAT data-taking software and some hardware problems due to aging were also discussed.<br/><br>
<br/><br>
The articles in the Appendices are connected with VSAT data-taking and the two-photon physics analysis.<br/><br>
<br/><br>
Appendix A, is the VSAT status report with estimation of VSAT performance for higher energies. The situation with the VSAT detector hardware and software upgrades are explained in the article.<br/><br>
<br/><br>
Appendix B, was written during the summer of 1999. The main subject of the article is the background condition in VSAT, STIC and other calorimeters. Some effective methods of removing background are proposed for each of the DELPHI calorimeters.<br/><br>
<br/><br>
Appendix C, describes problems of the long-time radiation damage and the short periods of high background which caused an increase of the bias currents in the VSAT modules.<br/><br>
<br/><br>
Appendix D, summarizes all beam parameters changes, position shifts of the VSAT modules observed by geometrical surveys and consequences of that during LEP II period.<br/><br>
<br/><br>
Appendix E, is devoted to the two-photons physics analysis of the DELPHI - VSAT data. The final analysis of two-photon events in double and single tag modes is presented.},
  author       = {Tyapkin, Pavel},
  isbn         = {91-628-6168-9},
  keyword      = {högenergi,QCD,STIC,VSAT,DELPHI,LEP,antitag,double tag,single tag,photon structure function,hadronic cross-section,virtual photons,two-photon,gamma-gamma,Kosmisk strålning,cosmic rays,High energy interactions,PHOJET,TWOGAM,PYTHIA,VDM,GSP,Fysicumarkivet A:2004:Tyapkin},
  language     = {eng},
  pages        = {190},
  publisher    = {ARRAY(0xb455bc0)},
  title        = {Study of Two-Photon processes at low Q<sup>2</sup> using the VSAT calorimeter in the DELPHI experiment},
  year         = {2004},
}