Measurement of the proton air cross section using hybrid data of the Pierre Auger Observatory [Elektronische Ressource] / von Ralf Matthias Ulrich

Sujets

• Physik

Informations

• Publié par: karlsruher_institut_fur_technologie
• Publié le: 01 janvier 2008
• Nombre de lectures: 31
• Langue: English
• Poids de l'ouvrage: 11 Mo

Extrait

Measurementoftheproton-aircrosssection
usinghybriddataofthe
PierreAugerObservatory
ZurErlangungdesakademischenGradeseines
DOKTORSDERNATURWISSENSCHAFTEN
vonderFakulta¨tfu¨rPhysikderUniversita¨t(TH)
Karlsruhe
genehmigte
DISSERTATION
vonDipl.-Phys. RalfMatthiasUlrich
ausBasel(Schweiz)
Tagdermu¨ndlichenPru¨fung: 21.12.2007
Referent: Prof. J.Blu¨mer
Korreferent: Prof. G.QuastALT XEAbstract
The subject of this thesis is the measurement of the proton-air cross section at ultra high
energy with hybrid data of the Pierre Auger Observatory. Based on a critical review of the
shortcomings of previous air shower measurements, a new analysis method is developed.
Thisanalysis methodtakesintoaccount themostimportantandrelevantexperimentaland
air shower physics effects. The impact of a changed cross section extrapolation on the re-
sulting air shower development is considered in addition to its more obvious effect on the
distributionofshowerstartingpoints. Furthermore,detectoracceptanceeffectsareexplicitly
includedinthereconstructionansatz,whichallowsustousealmostthecompletedatasetin
theanalysis. Systematicuncertaintiesontheresultingcrosssectionsarethoroughlystudied
and quantified. Assuming a proton dominated composition, the analysis is applied to hy-
briddataofthePierreAugerObservatory. Theobtainedcrosssectionis,withinthestatistical
andsystematicuncertainties,inagreementwithpredictionsfromhadronicinteractionmod-
18.4elsupto10 eV.Athigherenergiestheresultingcrosssectionincreasesrapidly. Finallythe
proton-air cross section is converted to a proton-proton cross section using Glauber theory
andlimitsontheelasticscatteringslopearederived.
Bestimmung des Wechselwirkungsquerschnittes von Protonen mit Luft mittels
Hybrid-DatendesPierreAugerObservatoriums
In dieser Arbeit werden Hybrid-Daten des Pierre Auger Observatoriums verwendet, um
den Wechselwirkungsquerschnitt von Protonen mit Kernen der Luft bei ultra-hoher En-
ergiezubestimmen. BasierendaufeinerAnalysederSchwachpunktefru¨hererLuftschauer-
Messmethodenwirdein neuerRekonstruktionsansatzentwickelt. Dieserberu¨cksichtigtex-
plizit diewichtigstenexperimentellensowiephysikalischenEffekte. DerEinflusseinerver-
a¨ndertenExtrapolationdesWechselwirkungsquerschnittesaufdieLuftschauer-Entwicklung
wirdebensoberu¨cksichtigtwiederEinflussaufdieVerteilungderLuftschauer-Startpunkte.
Daru¨ber hinaus wird die Akzeptanz des Detektors direkt in der Rekonstruktionsmethode
beru¨cksichtigt, wodurch fast der komplette Datensatz fu¨r die Analyse verwendet werden
kann. SystematischeUnsicherheitendesresultierendenWechselwirkungsquerschnitteswer-
denim Detailuntersuchtundquantifiziert. Die Hybrid-DatendesPierreAugerObservato-
riums werden unter der Annahme einer proton-dominierten Zusammensetzung der kos-
mischenStrahlunganalysiert. DerresultierendeWechselwirkungsquerschnittist,innerhalb
18.4der statistischen und systematischenUnsicherheiten, bis zu einer Energie von 10 eV mit
denVorhersagenvonhadronischenWechselwirkungsmodellenkompatibel. Beiho¨hererEn-
ergie nehmen die resultierendenWechselwirkungsquerschnittejedoch sehr schnell zu. Ab-
schliessendwird derProton-Luft-WechselwirkungsquerschnittmittelsderGlauber-Theorie
indenProton-Proton-WechselwirkungsquerschnittkonvertiertundeswerdenEinschra¨nkun-
gendesSteigungsparametersderelastischenStreuungabgeleitet.
iiiContents
1 Introduction 1
2 Cosmicrays,extensiveairshowersandhighenergyhadronicinteractions 3
2.1 Overviewofcosmicrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Extensiveairshowerphenomenology . . . . . . . . . . . . . . . . . . . . . . . 9
2.3 Hadronicinteractionmodels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4 Low-energymodels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.5 High-energymodels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.6 Proton-aircrosssectionmeasurementsusingcosmicraydata . . . . . . . . . . 26
2.7 Glaubertheoryandproton-protoncrosssection . . . . . . . . . . . . . . . . . 35
3 PierreAugerObservatory 41
3.1 Experimentalsetup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
line3.2 Off softwareframework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.3 Hybrideventreconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.4 Hybriddetectorsimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4 Anovelmethodtoderivetheproton-aircrosssection 73
4.1 Motivationof X asobservable . . . . . . . . . . . . . . . . . . . . . . . . . . 73max
4.2 Impactofmasscompositionandhadronicinteractionfeaturesonairshowers 74
4.3 ParameterizationoftheX -distribution . . . . . . . . . . . . . . . . . . . . . 84max
4.4 ShowerdevelopmentandtheΔX -distribution . . . . . . . . . . . . . . . . . . 861
4.5 Invisiblecrosssection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
4.6 Fittingrangeandstability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.7 Comparisontopreviousmeasurementstechniques. . . . . . . . . . . . . . . . 95
4.8 Primarycomposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5 Dataanalysis 101
5.1 Hybriddataselectionandqualitycuts . . . . . . . . . . . . . . . . . . . . . . . 101
5.2 Hybrid X -resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104max
5.3 Detectoracceptance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.4 Protonhypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.5 Proton-aircrosssection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
5.6 Systematicuncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.7 Discussionoftheresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6 Summary 131
References 135
Appendix 143
A Fasthybridsimulations 143
iiiB ΔX-parameterizations 148
B.1 Energydependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
B.2 Crosssectiondependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
C Fitsofthecross-sectionanalysis 154
C.1 AnalysisbasedonSIBYLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
C.2 AnalysisbasedonQGSJET01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
iv1 Introduction
In the early years, elementary particle physics began with the observation of cosmic rays
and cosmic ray induced air showers. Many discoveries are directly linked to the analysis
of cosmic ray interactions, like the finding of positrons [1], muons [2] and pions [3, 4, 5].
Following these early discoveries based on cosmic rays, accelerators were built for preci-
sionstudies. Thiswasleadingtohugeachievementsinunderstandingfundamentalparticle
physicsandtotheformulationoftheextremelysuccessfulstandardmodelofelementarypar-
ticlephysics. Allphysicssofardiscoveredatacceleratorscanbedescribedverywellwithin
thisframework(forexample [6,7]). Mainly thedifficulty tounifythecouplingconstantsof
allelementaryforcesathighenergyandthegeneralproblemtodescribegravityaretheory-
motivated arguments that require physics beyond the standard model. Again, it is only
astro- and astroparticle physics, which are currently providing experimental evidence for
theexistenceofsuchphysics. Namely,theobservationofthenon-vanishingmassofneutri-
nos[8,9]andtherequiredexistenceofdarkmatter[10].
Furthermore man-made accelerators are limited in their maximum energy, on the other
hand astroparticle physics can provide observations of the most extreme environments in
theuniverseandevenprobeultra-highenergyphysicsdirectly. Forexample,theextragalac-
ticpropagationofcosmicraysatultra-high energiesissensitivetoviolations oftheLorentz
invariance of space-time [11, 12] as well as new particle physics. Moreover, by the obser-
vation of the highest energy cosmic rays it is also possible to study hadronic interactions
directlyatenergiesfarlarger,thananyEarth-basedacceleratorisabletoreach.
With the Pierre Auger Observatory there is the first time a detectoravailable, which al-
lowsustodohighprecisionstudiesofcosmicraysatultra-highenergies[13]. Thisismainly
duetothehybriddetectordesign,combiningagroundbasedairshowerarraywiththedata
of telescopedetectors,which observetheshowerdevelopmentwithin theatmosphere. The
2enormous size of the Auger detectorof more than 3000km allows us to gather high event
statisticsalreadyafterthefirstfewyearsofoperationdespiteof theextremelysmallcosmic
ray flux at these energies. This is ideal for studying cosmic ray properties like their origin,
butalsotostudyhadronicinteractionsatultra-highenergies.
The aim of this thesis is the first measurement of the proton-air cross section based on
thehybriddataofthePierreAugerObservatorycollectedsofar.
As a starting point methodical studies of previous attempts to measure the proton-air
cross section using air shower data are studied, unveiling the common scheme, on which
they are all founded on. The principal shortcoming, which is inherent to all of them, is
pointedout.
Basedonthesefundamentalstudiesanovelmethodtoderivetheproton-aircrosssection
from air showerdatais developed. Compared topreviousmethodstomeasuretheproton-
aircrosssection,twomainimprovementsa