Pattern recognition in the inner tracking system of HERA-B and measurement of the V_1tn0 production cross section in pN collisions [Elektronische Ressource] / vorgelegt von Iouri Gorbounov

Gorbounov, Iouri

Sujets

• Physik

Informations

• Publié par: universitat_siegen
• Publié le: 01 janvier 2004
• Nombre de lectures: 27
• Langue: Deutsch
• Poids de l'ouvrage: 7 Mo

Extrait

Pattern Recognition in the Inner Tracking
System of HERA-B
and Measurement of the V Production0
Cross Section in pN Collisions
Dissertation
zur
Erlangung des Grades eines Doktors
der Naturwissenschaften
vorgelegt von
Dipl.-Phys. Iouri Gorbounov
geb. am 28.01.1976 in Protvino
eingereicht beim Fachbereich Physik
der Universit at Siegen
Siegen 2003Dissertation
1. Gutachter: Prof. Dr. Gun ter Zech
2.hter: Prof. Dr. Peter Buchholz
Disputation
am 23.01.2004
Prufer: Prof. Dr. Hans-Dieter Dahmen
Prof. Dr. Peter Buchholz
Prof. Dr. Gun ter Zech
urn:nbn:de:hbz:467-353Dissertation
submitted to the
Siegen University
for the degree of
Doctor of Natural Sciences
Pattern Recognition in the Inner Tracking
System of HERA-B and Measurement of the
V Production Cross Section in pN Collisions0
presented by
Diplom-Physicist Iouri Gorbounov
Born in Protvino
Siegen, 2003Zusammenfassung
Das HERA-B-Experiment be ndet sich am HERA-Beschleuniger bei DESY,
Ziel dieses Experimentes war die Messung der CP-Verletzung in dem Sys-
tem der neutralen B-Mesonen. Das inneren Spurkammersystem von HERA-B
besteht aus GEM-MSGC-Detektoren.
Im ersten Teil der Arbeit wird die Entwicklung eines Spurrekonstruktions- Al-
gorithmus (CATS) fur das inneren Spurkammersystem vorgestellt. Der Algo-
rithmus wurde erfolgreich w ahrend der Online-Datennahme und fur die O ine-
Aufbereitung der Daten der Jahre 2002/03 benutzt.
Die Betriebseigenschaften des inneren Spurkammersystems w ahrend der Inbe-
triebnahme wurden bestimmt. Die angewendete Methode basiert auf dem fur
das innere Spurkammersystem entwickelten Spurrekonstruktions-Algorithmus.
Mit Hilfe der gemessenen E zienzen der Einzeldetektoren wurden die indi-
viduellen GEM-Spannungen korrigiert, um die Gesamte zienz des inneren
Spurkammersystems zu verbessern.
Im zweiten Teil der Arbeit wird eine Messung des inklusiven Produktions-
2 0 Wirkungsquerschnitts d =dx und d =dp fur K , und Teilchenpro-pA F pA t Sp
duktion in pN-Kollisionen bei s=41.6 GeV vorgestellt. Daten aus Proton-
Kohlensto , Titan und Wolfram Wechselwirkungen wurden benutzt. Die
Massenabh angikeit des Wirkungsquerschnitts wurde gemessen.pA
Abstract
The HERA-B experiment located at the HERA collider at DESY, was designed
and built to measure CP violation in the system of neutral B mesons. One
of the HERA-B detector components is the Inner Tracker, which consists of
Micro-Strip Gas Counters with a Gas-Electron Multiplier (GEM-MSGC).
This thesis describes the development of a pattern recognition algorithm
(CATS) for the Inner Tracking system of HERA-B. The algorithm was success-
fully used during online data taking and o ine reprocessing of the collected
data in the years 2002 and 2003.
During the running period 2002/03 the performance of the Inner Tracking
system was estimated. The applied procedure was based on the developed
pattern recognition algorithm. With the help of the measured e ciencies, a
tuning of the GEM voltages was performed in order to increase the e ciency
of the Inner Tracking system.
The second part of this thesis describes a measurement of the inclusive di er-
2 0ential cross sections d =dx and d =dp for the production of K , andpA F pA t Sp particles produced in pN collisions at s=41.6 GeV. As target materials C,
Ti and W were used and the dependence of the total cross section on thepA
target atomic mass is measured.
iiiContents
1 Introduction 1
1.0.1 CP violation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.0.2 Physics Programme for Data Taking 2002/03 . . . . . . . . . . . . 3
1.0.3 The Search for QGP . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.0.4 Strangeness production in a Quark Gluon Plasma . . . . . . . . . . 5
2 The HERA-B experiment 7
2.1 The HERA Storage ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Detector overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 The Inner Tracker System 15
3.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2 Used technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.1 MSGC, GEM, GEM-MSGC . . . . . . . . . . . . . . . . . . . . . . 16
3.2.2 GEM-MSGC at HERA-B . . . . . . . . . . . . . . . . . . . . . . . 18
3.3 The Inner Tracker system . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.4 Infrastructure for Chamber Operation . . . . . . . . . . . . . . . . . . . . . 20
4 Pattern recognition 25
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.2 Methods of Track Recognition . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.3 CATS Track Recognition Strategy . . . . . . . . . . . . . . . . . . . . . . . 27
4.3.1 Association of Neighboring Hits into Clusters . . . . . . . . . . . . 27
4.3.2 Reconstruction of Space-Points . . . . . . . . . . . . . . . . . . . . 29
4.3.3 of Track Candidates . . . . . . . . . . . . . . . . . . 30
4.3.4 Track Competition for Clone and Ghost Removal . . . . . . . . . . 32
4.3.5 Left-Right Ambiguity Resolution . . . . . . . . . . . . . . . . . . . 32
4.3.6 Track Fit by the Kalman Filter and Smoother . . . . . . . . . . . . 35
4.4 Performance Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.4.1 Reference Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.4.2 MC Study Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.4.3 OTR/ITR-CATS on Real Data . . . . . . . . . . . . . . . . . . . . 45
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
iii5 Hit e ciency 47
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.2 Masking Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.3 Track Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.4 E ciency of the Superlayer MS01 . . . . . . . . . . . . . . . . . . . . . . . 53
5.5 of the PC Superlayers . . . . . . . . . . . . . . . . . . . . . . . . 54
5.6 E ciency of the TC Superlayers . . . . . . . . . . . . . . . . . . . . . . . 56
5.7 Test of the Algorithm with Monte Carlo . . . . . . . . . . . . . . . . . . . 58
5.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6 V Inclusive Production Cross Sections 630
6.1 Monte Carlo Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.2 Event Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
0 6.3 K ; ; Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65S
6.3.1 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.3.2 Selection Cuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
6.3.3 Armenteros-Podolanski Plot . . . . . . . . . . . . . . . . . . . . . . 67
6.3.4 Summary of Used Cuts . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.3.5 Detector Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.4 Acceptance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.5 Luminosity Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
6.6 MC and Data Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
6.6.1 ITR Contribution and Stability . . . . . . . . . . . . . . . . . . . . 77
6.7 V signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 810
6.8 Cross Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.8.1 Systematic Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7 Conclusion 95
A Runs used in the analysis 103
Bibliography 105
ivChapter 1
Introduction
This chapter presents a brief overview of the original physics goal of HERA-B - measuring
CP violation in the decays of neutral B mesons. Finally the modi ed physics program is
outlined.
The violation of CP symmetry was rst observed in the system of neutral K mesons
0 0 0(K K ). TheK has a CP eigenstate of -1 but it was shown that it can also decay intoL
two charged pions with a CP of +1. The Standard Model o ers a mechanism
which can explain this violation. The system of neutral B mesons should also show
CP violation mediated by the same mechanism and in addition the CP violation in the
B-system should be large relative to the Kaon system.
HERA-B was approved in 1994 [1] but the start of the HERA-B experiment was de-
layed by several years due to problems during detector development and commissioning.
+The e e B factory approach was chosen by two experiments: BaBar [29] collaboration
at SLAC and Belle [30] collaboration at KEK, they were able to present their rst mea-
surements of CP violation already in 2000. Since that moment the measurements have
reached an accuracy level that can not be reached by HERA-B. HERA-B was commis-
sioned in 1999 with a short data taking run. In 2000/01, during the HERA luminosity
upgrade, HERA-B detector was partially upgraded and nalized. Since it became obvious
that HERA-B is no longer competitive in B-physics a new physi