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The Study of Hadron Dynamics in Relativistic Heavy Ion Collisions

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The Study of Hadron Dynamics in Relativistic Heavy Ion Collisions The Study of Hadron Dynamics in Relativistic Heavy Ion Collisions INIS-mf—14275 r i %••,'• KS00165264X DEO059O3621 The Study of Hadron Dynamics in Relativistic Heavy Ion Collisions S 135 Rijksuniversiteit Groningen The Study of Hadron Dynamics in Relativistic Heavy Ion Collisions Proefschrift ter verkrijging van het doctoraat in de Wiskunde en Natuurwetenschappen aan de Rijksuniversiteit Groningen op gezag van de Rector Magnificus Dr. S.K. Kuipers in het openbaar te verdedigen op vrijdag 22 april 1994 des namiddags te 2:45 uur precies door Lars Brf .at Venema geboren op 26 april 1964 te Winschoten Promotores : Prof. Dr. R.H. Siemssen Prof. Dr. H. Löhner Referent : Dr. H.W.E.M. Wilschut The work described in this thesis is the result of the common effort of the TAPS collaboration. The TAPS collaboration is an international group consisting of scientists from different institutes and universities. At the time of the experiments described in this thesis the collaboration consisted of the Gesellschaft für Schwerlonenforschung (GSI), the university of Gießen, the Kernfysisch Versneller Instituut (KVI), the Grand Accelerateur National des Ions Lourds (GANIL) and the university of Münster. This work was performed as part of a research program supported by the Stichting voor Fundamenteel Onderzoek der Materie (FOM), the Gesellschaft für Schwerlonenforschung (GSI), the Institut National de Physique Nucleaire et de Physique des Particules (IN2P3) and by the Bundesministerium für Forschung und Technologie (BMFT) through the uni- versities of Gießen and Münster. Abbreviations ADC Amplitude to Digital Converter BUU Boltzmanu Uehling Uhlenbeck CFD Constant Fraction Discriminator CPV Charged Particle Veto V Directivity EOS Equation Of State FW Forward Wall FWHM Full Width at Half Maximum GSI Gesellschaft für Schwerlonenforschung KVI Kerafysisch Versneller Instituut INC Intra Nuclear Cascade DPW Inner Plastic Wall IQMD Isospin Quantum Molecular Dynamics LED Leading Edge Discriminator M Multiplicity OFM One Fluid Model OPW Outer Plastic Wall QDC Charge (Q) to Digita' Converter QGSM Quark Gluon String Model QMD Quantum Molecular Dynamics RDV Retard Digital Variable RMS Root Mean Square RQMD Relativistic Quantum Molecular Dynamics SIS Schwer Ionen Synchrotron TAPS Two Arm Photon Spectrometer TDC Time to Digital Converter TFM Two Fluid Model TOF Time Of Flight Contents 1 Introduction 1 1.1 History 3 1.1.1 First Experiments 4 1.1.2 Pion Spectra 5 1.1.3 Pion Yield 8 1.1.4 Collective Motion 8 1.2 Goals 11 1.3 This Thesis 11 2 Theory 13 2.1 The Hydrodynamical Model 15 2.1.1 The One Fluid Model 15 2.1.2 The Two Fluid Model 16 2.2 Cascade Models 17 2.2.1 The Boltzmann-Uehling-Uhlenbeck Model 20 2.2.2 The "Quantum Molecular Dynamics" Models 23 2.2.3 The Toneev Gudima Cascade Model (QGSM) 25 2.2.4 Overview of the Models 26 3 Experimental Setup 29 3.1 The Experiment 29 3.1.1 Beams, Targets and Beam Detectors 30 3.1.2 The Forward Wall 31 3.1.3 TAPS 34 3.1.4 TAPS Data Acquisition 36 3.2 The TAPS-detector 38 3.2.1 The Detector 38 3.2.2 Performance Tests of the Detector 41 3.2.2.1 Charged Particle and Pulse Shape Analysis 41 3.2.2.2 Photon Response Tests 45 3.2.3 The Laser System 49 3.2.3.1 Introduction 49 3.2.3.2 Hardware of the Laser System 49 3.2.3.3 The Laser Analysis 53 3.2.3.4 Stability during the Au + Au Experiment 54 4 Data Analysis 57 4.1 Event-by-Event Analysis 57 4.1.1 Energy Calibration 58 4.1.2 Time Calibration 59 4.1.3 Pulse Shape Analysis 60 4.1.4 Cluster Routine 62 4.1.5 Invariant Mass Analysis 65 4.1.5.1 Invariant Mass Reconstruction 65 4.1.5.2 Resolution 69 4.2 Photon Efficiency 71 4.3 Acceptance Corrections 74 4.4 Absolute Normalization 77 4.5 Forward Wall Analysis 78 4.5.1 Calibration 79 4.5.2 Impact Parameter Selection 81 4.5.3 Reaction Plane 83 5 Results 89 5.1 Inclusive 7T°-Spectra 90 5.1.1 Ar + Ca 90 5.1.2 Au + Au 93 5.1.3 ir°-Spectra from Model Calculations 96 5.1.3.1 Ar + Ca 96 5.1.3.2 Au + Au 97 5.2 Particle Multiplicities 100 5.2.1 Ar + Ca 100 5.2.2 Au + Au 102 5.2.3 Comparison with Models 103 5.3 Systematics 108 5.4 Impact Parameter Dependence 113 5.4.1 Methods for Impact Parameters Selections 113 5.4.2 Sensitivity of 7r°-meson Spectra to Impact Parameter 116 5.4.2.1 The Experimental Results 116 5.4.2.2 The Theoretical Models 118 5.5 Reaction Plane Dependence 120 5.5.1 Au + Au 121 5.5.1.1 Azimuthai Distributions of Charged Particles and Neutronsl21 5.5.1.2 Azimuthal Distribution of Neutral Pions 122 5.5.1.3 Pion Spectra 126 5.5.2 Ar + Ca 127 5.5.3 Discussion 130 6 Summary 135 6.1 Conclusions 135 6.2 Future Prospects 137 A Relativistic Formulas 139 A.I Relativistic Kinematics 139 A.2 Cross Section Transformations 142 A.3 Scaling 143 B Properties of the v-mesoa 145 C Analysis parameters 147 D Experimental data 149 List of Publications 155 Bibliography 157 Samenvatting 167 Nawoord 173 Stellingen behorende bij het proefschrift: The Study of Hadron Dynamics in Relativistic Heavy Ion Collisions 1. De interacties tussen resonanties en nucleonen en tussen resonanties onderling kun- nen door middel van relativistische zware ionen reakties bestudeerd worden. 2. In tegenstelling tot eerdere beweringen is het pion wel geschikt om de hete reak- tiezone bij relativistische kernbotsingen te onderzoeken. (Dit proefschrift, hoofdstuk 5.5) 3. Er kan geen onderscheid gemaakt worden tussen bijdragen van 'toeschouwers' en 'deelnemers' aan een spectrum gemeten bij de zwaartepuntsrapiditeit indien bij de meting geïntegreerd is over de azimut ten opzichte van het reaktievlak. (Dit proefschrift, hoofdstuk 5.5) 4. De energie-afhankelijke geometrische acceptantie van pionen is zo gecompliceerd dat men tijdens een experiment de detectorgeometrie niet op basis van ad-hoc ar- gumenten kan veranderen. (Dit proefschrift, hoofdstuk 4.3) 5. Bij een multi-detector systeem zoals TAPS die zeer veel observabelen meet, is het onmogelijk alle beschikbare informatie te verwerken. 6. De veel gebruikte methode om dosis-effect relaties van tumorinductie door straling weer te geven door de gemiddelde incidentie van een groep dieren uit te zetten tegen de gemiddelde dosis, is onvoldoende voor het verkrijgen van inzicht in het effect van straling omdat de gemiddelde leeftijd van de groepen zeer sterk uiteen kan lopen. 7. Gezien de sterke correlatie tussen de natuurlijke kans op kanker en het verhoogde risico ten gevolge van straling is het sterk te betwijfelen of volstaan kan worden met één enkele (internationale) stralingsnorm zoals het ICRP dat voorstelt. 8. De praktijk om van alle experimentele resultaten van dierproeven alleen de groeps- gemiddelden te publiceren, reduceert de bruikbaarheid van deze experimenten. 9. De stelling 'A theme should have a certain something which Ike whole world already knows. * geldt niet alleen voor de muziek, maar zeker ook voor de wetenschap. (1) Arnold Schönberg. Fundamentals of musical composition 10. Het is opmerkelijk dat het gezegde "zoals de baas is, is zijn hond" omgekeerd zo vaak opgaat voor musici en hun instrument. 11. Met een wereldbevolking van 5 miljard mensen kan de jacht niet langer een serieuze mogelijkheid zijn om de mensheid van voedsel te voorzien. 12. In de discussies rond euthanasie is het verwerpelijk dat sommige mensen menen te mogen oordelen over de dragelijkheid van het lijden van anderen. 13. Het lijkt een kenmerk van de Nederlandse politiek te zijn om alles waarin Nederland zich onderscheidt van het buitenland af te willen schaffen. Het beleid op het gebied van de universitaire studies en vervolgopleidingen sinds de aanloop van de twee-fasen structuur is hiervan een sprekend voorbeeld. 14. De populariteit van bronwater doet vermoeden dat lucht het volgende commerciële succes wordt. 15. Het scheiden van fietsen en auto's op gevaarlijke kruispunten leidt er nogal eens toe dat de doorstroom van auto's verbetert terwijl dat niet opgaat voor de fietsen. 16. Het is af te raden met een skegloze kano in zee te gaan. Lars Venema 28 februari 1994 Chapter 1 Introduction The main emphasis in nuclear physics has been on structure and .eaction dynamics at fairly low excitation energies before it became feasible to study in relativistic heavy ion collisions the properties of hadronic matter at densities higher than normally encoun- tered in ordinary nuclei. A great impulse for nuclear physics may be expected when more detailed knowledge of the behaviour of hadrons under conditions far away from the conditions normally encountered in nuclei becomes available. The properties of highly compressed nuclear matter" is regarded as a very important question. The properties of highly compressed nuclear matter are also important outside the field of nuclear physics. Answers to questions concerning the stability of neutron stars and the ignition of supernova explosions [1] appear to depend on the compressibility of nuclear matter. It was recognized in the early 70's that during high energy heavy ion collisions a state of high density nuclear matter may be created. When nuclei with high velocity collide and the penetration speed of the projectile nucleus is higher than the velocity of sound in the nuclear medium, r.ucleons will accrete in the overlap region. The flux of ntcleons into this region caused by the projectile momentum will exceed the flux out of this region due to the increased pressure.
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