To flow or not to flow; A study of elliptic flow and nonflow in proton-proton collisions in ALICE

132 Pages·2011·3.31 MB·English

To flow or not to flow
A study of elliptic flow and nonflow
in proton-proton collisions in ALICE
AcataloguerecordisavailablefromtheUtrechtUniversityLibrary.
ISBN:978-90-393-5705-7
Copyright(cid:13)c 2011byN.vanderKolk
All rights reserved. No part of this book may be reproduced, stored in a database or
retrievalsystem,orpublished,inanyformorinanyway,electronically,mechanically,by
print, photoprint, microfilm or any other means without prior written permission of the
author.
Coverdesign: N.vanderKolk
TypesetusingLATEXandprintedbyIpskampDrukkers,Enschede,TheNetherlands.
To flow or not to flow
A study of elliptic flow and nonflow
in proton-proton collisions in ALICE
Over het meten van elliptische flow en nonflow
in proton-protonbotsingen met de ALICE-detector
(meteensamenvattinginhetNederlands)
PROEFSCHRIFT
terverkrijgingvandegraadvandoctoraandeUniversiteitUtrechtopgezag
vanderectormagnificus,prof.dr. G.JvanderZwaan,ingevolgehetbesluit
vanhetcollegevoorpromotiesinhetopenbaarteverdedigenopwoensdag
25januari2012desmiddagste12.45uur
door
Naomi van der Kolk
geborenop4oktober1979teEindhoven
Promotoren:
Prof.dr. Th. Peitzmann
Prof.dr. R.J.MSnellings
“Itwouldbesoniceifsomethingwouldmakesenseforachange”
AliceinWonderland-LewisCarroll

Contents
1. Introduction 1
1.1 TheStandardModel ................................................. 2
1.2 QuantumChromodynamics .......................................... 4
1.3 TheQuarkGluonPlasma............................................. 6
1.4 Kinematicvariables.................................................. 9
1.5 Proton-protoncollisions.............................................. 10
1.6 Heavyioncollisions ................................................. 11
1.7 SignaturesoftheQGP................................................ 12
v
1.8 Thesisoutline....................................................... 14
2. Elliptic Flow 17
2.1 Radialflowinheavyioncollisions..................................... 18
2.2 Anisotropicflowinheavyioncollisions ................................ 18
2.3 Ellipticflowinheavyioncollisions .................................... 20
2.3.1 Centralitydependence............................................ 21
2.3.2 Transversemomentumandparticlespeciesdependence............... 22
2.3.3 Energydependence .............................................. 24
2.3.4 Eccentricityfluctuations........................................... 25
2.3.5 Nonflowcorrelations ............................................. 27
2.4 Ellipticflowinproton-protoncollisions ................................ 27
3. The ALICE Detector 31
3.1 TheLargeHadronCollider ........................................... 32
3.2 TheALICEdetector.................................................. 33
3.3 Subdetectors........................................................ 35
3.3.1 InnerTrackingSystem ............................................ 35
3.3.2 TimeProjectionChamber.......................................... 36
3.3.3 TheForwardMultiplicityDetectorandtheVZEROcounters........... 37
ff
3.4 EventreconstructionintheALICEo -lineframework.................... 37
3.4.1 Minimumbiaseventselection ..................................... 37
3.4.2 Eventreconstruction.............................................. 38
3.4.3 Tracking ........................................................ 38
3.4.4 Alignmentandcalibration......................................... 39
4. Analysis Methods 41
4.1 Scalarproductmethod ............................................... 43
4.2 Cumulantmethod................................................... 46
4.3 Lee–Yangzeroesmethod ............................................. 47
ff
4.4 Aneventplaneestimatewithoutnonflowe ects ........................ 51
4.5 Analysissoftware ................................................... 52
4.6 ValidationusingMonteCarlosimulations .............................. 52
4.6.1 Applicabilityoftheanalysismethods ............................... 53
4.7 Discussion.......................................................... 59
5. Correlations in proton-proton collisions 63
5.1 Datasample ........................................................ 64
5.1.1 Eventselection................................................... 64
5.1.2 Trackselection................................................... 64
5.1.3 Kinematiccuts................................................... 66
ffi
5.1.4 E ciencyandpurity ............................................. 67
5.2 Correlationmeasurementsusingthescalarproductmethod............... 68
5.2.1 PseudorapiditygapdependenceinsimpleMonteCarloevents......... 69
vi
5.2.2 PseudorapiditygapdependenceinPYTHIAevents................... 72
5.2.3 Pseudorapiditygapdependencein7TeVproton-protondata .......... 75
5.2.4 Discussion ...................................................... 78
6. Conclusions and Summary 81
η
A.Extending the -range 87
B. Estimating nonflow in Pb-Pb collisions from proton-proton
collisions 95
B.1 Analysismethod .................................................... 96
B.2 ValidationofthemethodusingasimpleMonteCarlomodel .............. 98
B.3 Scalingwiththecentreofmassenergy ................................. 99
B.4 CentralitydependenceinPb-Pbcollisions .............................. 101
B.5 Discussion.......................................................... 105
References 109
Samenvatting 115
Curriculum Vitae 119