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ISBN 91-628-4932-8
LUNFD6/(NFFL-7199)2001

Hadronic Structure Measurements of the Photon
by DELPHI at LEP II

Thesis submitted for the degree of
Doctor of Philosophy in Physics

by

Andreas Nygren


Department of Physics
Lund University, 2001

Organization:		Document name:
LUND UNIVERSITY		DOCTORAL DISSERTATION
Department of Physics		Date of issue:  30th August 2001
Professorgatan 1, Box 118		CODEN:
221 00 Lund, Sweden		LUNFD6/(NFFL-7199)2001
Author(s)		Sponsoring organization:
Andreas Nygren
Title and subtitle:
Hadronic Structure Measurements of the Photon by DELPHI at LEP II
Abstract:
This thesis is mainly an analysis of data taken by the VSAT detector in the
DELPHI experiment at the LEP II collider at CERN. The analysis spans from
1998 to 2000, with a center of mass energy ranging from 189 to 206 GeV. The
VSAT calorimeter was constructed to be a luminosity and background monitor
for the DELPHI experiment, and a full description of the luminosity and
background analysis for the LEP II conditions is presented.
The VSAT detector is located in the very forward direction and covers angles
between three and eight milliradians since 1998. This also makes the detector
an excellent tool for studying two photon physics, as the outgoing
electrons from a two-photon collision mainly are located at small angles.
A full study of the VSAT double tag data between 1998 and 2000 is presented.
Gamma-gamma collisions with an invariant mass reaching up to 100 GeV could be
explored in a Q2 range of 0.2-0.8 GeV. With help of data from the STIC
detector, which is located at larger polar angles, two photon collisions could
also be probed with a Q2 between 20 and 100 GeV.
Key words:
VSAT, DELPHI, LEP, luminosity, two-photon physics, cross section,
double tag, bhabha, structure function, background
Classification system and/or index terms (if any):
Supplementary bibliographical information:			Language: English
ISSN and key title:			ISBN:91-628-4932-8
Recipient's notes:		Number of pages: 153	Price:
		Security classification:
Distribution by (name and address): Andreas Nygren,
Lund University, Department of Physics, Box 118, 221 00 Lund, Sweden
I, the undersigned, being the copyright owner of the abstract of the above-mentioned
dissertation, hereby grant to all reference sources permission to publish and
disseminate the abstract of the above-mentioned dissertation.
Signature:			Date: 30th August, 2001

ISBN 91-628-4932-8
LUNFD6/(NFFL-7199)2001

Hadronic Structure Measurements of the Photon
by DELPHI at LEP II

By due permission of the faculty of mathematics and natural science at the University of Lund, to be publicly discussed at the lecture hall B of the Department of Physics, Sep 28, 2001, at 13.15, for the degree of Doctor of Philosophy

by

Andreas Nygren


Department of Physics
Lund University
Professorsgatan 1
Box 118
SE-221 00 Lund
Sweden

This thesis is based on following papers, included as Appendices A to H:

A.

Exact position of VSAT modules and LEP beam parameters measurements in 1998-2000. DELPHI Note 2001-005 CAL 145

B.

Proceedings from QFTHEP 2000 in Tver, Russia.
DELPHI Note 2001-002 Talk 021

C.

$\gamma$$\gamma$ -Physics background in VSAT.
DELPHI Note 2000-173 Phys 884.

D.

LEP machine background and noise in the DELPHI calorimeters.
DELPHI Note 99-157 LEDI 87.

E.

VSAT Background and Luminosity 1999.
DELPHI Note 2000-054 Phys 857.

F.

VSAT trigger and energy response for LEP II.
DELPHI Note 99-163 CAL 143 .

G.

Forthcoming results in two-photon collisions.
DELPHI Note 98-175 Phys 814 .

H.

1998 Running review workshop, the VSAT project
DELPHI 99-49 LEDI 11

Abstract

This thesis is mainly an analysis of data taken by the VSAT detector in the DELPHI experiment at the LEP II collider at CERN. The analysis spans from 1998 to 2000, with a center of mass energy ranging from 189 to 206 GeV. The VSAT calorimeter was constructed to be a luminosity and background monitor for the DELPHI experiment, and a full description of the luminosity and background analysis for the LEP II conditions is presented.

The VSAT detector is located in the very forward direction and covers angles between three and eight milliradians since 1998. This also makes the detector to an excellent tool for studying two photon physics, as the outgoing electrons from a two-photon collision mainly are located at small angles. A full study of the VSAT double tag data between 1998 and 2000 is presented. Gamma-gamma collisions with an invariant mass reaching up to 100 GeV could be explored in a Q² range of 0.2-0.8 GeV. With help of data from the STIC detector,which is located at larger polar angles, two photon collisions could also be probed with a Q² between 20 and 100 GeV.