Analysis of diffractive dissociation of K- into K- pi+ pi- on a liquid hydrogen target at the COMPASS spectrometer [Elektronische Ressource] / Prometeusz Kryspin Jasinski

© Prometeusz Kryspin Jasinski, Johannes Gutenberg-Universität Mainz, Institut Für Kernphysik

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• Physik

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• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2012
• Nombre de lectures: 11
• Langue: English
• Poids de l'ouvrage: 21 Mo

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prometeusz kryspin jasinski
-A N A LY S I S O F D I F F R A C T I V E D I S S O C I AT I O N O F K
- + -I N T O K O N A L I Q U I D H Y D R O G E N TA R G E T AT
T H E C O M PA S S S P E C T R O M E T E R- - + -A N A LY S I S O F D I F F R A C T I V E D I S S O C I AT I O N O F K I N T O K
O N A L I Q U I D H Y D R O G E N TA R G E T AT T H E C O M PA S S
S P E C T R O M E T E R
Dissertation
zu Erlangung des Grades
"Doktor der Naturwissenschaften"
am Fachbereich Physik der
Johannes Gutenberg-Universität in Mainz
prometeusz kryspin jasinski
geb. in Duszniki Zdr. (Polen)
Mainz, den 02.01.2012-Prometeusz Kryspin Jasinski: Analysis of diffractive dissociation of K
- + -into K on a liquid hydrogen target at the COMPASS Spectrometer,
© 02.01.2012 Mainz D77
tag der mündlichen prüfung: 22.12.2011Dedicated to my beloved Julia
who made me the best gifts ever:
my lovely children,
Leonie & Paul.A B S T R A C T
The systematic exploration of excited meson and baryon states was the
central topic of the COmmon Muon Proton Apparatus for Structure and
Spectroscopy (COMPASS) physics program in the years2008 and2009 at
the CERN facility. Particularly states non fitting a constituent quark model
were searched for, identified by their exotic quantum numbers which are
forbidden by a simpleqq¯ scheme. A high energetic hadron-beam on a
fixed target yielded in resonances decaying into a large variety of final
states. The diffractive and central production mechanisms allowed for
- + - +a clean exclusive selection of channels such as p! p ,recoil
which then were analysed with a high precision and a huge number of
events.
Apart from the main pion component in the negative hadron beam a
small fraction of kaons of about2.5% allowed the study of light strange
- + -resonances in theK decay channel. The best measurement in this
channel was quoted to be so far the measurement of the WA03 experiment
at CERN. The ACCMOR-collaboration has the data recorded and analysed
with an experimental set-up very similar to the COMPASS-spectrometer [1].
COMPASS had therefore not only the ability to remeasure this channel with
a significantly higher number of events and better precision to cross-check
those over30 years old results. Moreover, improved analysis methods
together with new evidences from other experiments, are expected to
enlighten our present picture of the hadron spectrum.
Chapter1 introduces the concept of meson spectroscopy. The formation
of bound quark anti-quark systems allows to interpret our measurements
in terms of coupled quantum numbers, with properties as spin, charge
1conjugation and parity. Particularly kaonic isospinI= resonances are
2
classified as proposed by group theory and differences to I = 1 and
I=0 states, formed mainly byu andd quarks and their anti-quarks, are
pointed out.
That chapter introduces also the production mechanisms used to access
those resonances and summarizes briefly the results obtained so far from
previous experiments. Special emphasis is put on single diffraction of
beam particles at high beam energies. Important observables as well
as the main properties of the production mechanisms are defined, to
understand how excited beam particles were identified in the COMPASS
spectrometer.
Chapter2 describes the most important parts of the COMPASS spectrom-
eter as it was assembled in the years2008 and2009 under light meson
spectroscopy considerations. The beam line and beam properties of the
hadron beams are discussed since beam divergence was affecting the
kaon identification in the initial state significantly. Detectors used to mea-
sure the large variety of processes are presented as well as information
viiabout triggers, the DAQ and event reconstruction is given. As strategies
had been developed for this analysis, to distinguish kaons from pions
with the CEDAR detectors in the initial channel as well as with the RICH
detector in the final states, those detectors are treated of in two separate
chapters.
The CEDAR detector, designed to identify one kind of particles in
the beam is described in chapter 3. The set-up, performance and mea-
surement of it is discussed as well as stability issues of those detectors
filled with pressurized helium are pointed out. The calculation of the
separation-purity is described and alternative methods to analyse the
signals of this detector are shown.
Chapter4 deals with the final state PID at COMPASS with the help of the
RICH detector. The PID, based on individual likelihood cuts, is explained
and a measurement of the performance of this detector for the data of
the year2008 is presented. This is particularly important as the resulting
efficiency and purity distributions were used directly as an input to the
MC acceptance simulations.
- + -The strategy for the selection of diffractively producedK events
is shown in chapter5. Apart from the detailed explanation of cuts applied
to the data, quality studies showing the impact by initial state pions are
presented. The model of a two-body decay of resonances into the final
states is already motivated by observations of r in the invariant
- + + -mass distributions ofK and track combinations as well as the
corresponding Dalitz plots. About270000 events served finally as an
input to PWA.
As Partial Wave Analysis (PWA) needs further information on the
- + -availableK phase space and the spectrometer acceptance of it, a
detailed MC simulation study was performed as depicted in chapter 6.
There, the methods to simulate the signal response of several detectors
are presented, used to process in total44 million MC decays in the range
- + - 2of0.86m(K )[GeV/c ]<3.0.
Finally all information from event selection and MC studies was com-
bined in the PWA to observe resonances, suspected to contribute to the
- + -invariantK mass spectrum. The continuous momentum basis of
final states was expanded in terms of discreet states with spin, parity
and orbital angular momentum. A partial wave set was found with the
help of mass independent fit algorithms, able to describe the observed
- + -K spectrum and it’s dynamics in narrow bins of the invariant
- + -K mass. Individual partial wave resonances are discussed and
a proposal for a partial wave amplitude parametrization is made. The
results of the mass independent analysis studies are the fundamental
basis for a prospective mass dependent fit giving finally the information
about poles, widths and coupling constants of contributing resonances.
viiiZ U S A M M E N FA S S U N G
Das Hauptziel des COmmon Muon Proton Apparatus for Structure and
Spectroscopy (COMPASS) Physikprogramms in den Jahren2008 und2009
am CERN Forschungszentrum war die systematische Erforschung angereg-
ter Mesonen und Baryonen. Es wurden hauptsächlich Zustände gesucht,
die nicht in ein Konstituentenquark-Modell passten, weil ihre exotischen
Quantenzahlen im simplenqq¯ -Schema verboten waren. Ein hochenerge-
tischer Hadronstrahl auf einem festen Target erzeugte Resonanzen, die
in eine große Vielfalt von Endzuständen zerfielen. Die diffraktiven und
zentralen Produktionsmechanismen erlaubten eine saubere Auswahl von
- + - +Kanälen wie p! p , welche mit hoher Präzision undrecoil
einer großen Anzahl von Ereignissen untersucht werden konnten.
Abgesehen von der pionischen Hauptkomponente des negativen Ha-
dronstrahls erlaubte ein kleiner Anteil mit2,5% an Kaonen das Studium
- + -leichter seltsamer Resonanzen im K Zerfallskanal. Die bis dato
beste Messung in diesem Kanal kam vom WA03-Experiment am CERN.
Die ACCMOR-Kollaboration hatte mit einem experimentellen Aufbau, sehr
ähnlich dem des COMPASS-Spektrometers, die Daten aufgenommen und
analysiert [1]. COMPASS hatte demnach nicht nur die Möglichkeit diesen
Kanal mit einer deutlich höheren Anzahl von Ereignissen und besserer
Präzision wieder zu untersuchen, um die über30 Jahre alten Ergebnisse
zu überprüfen. Vielmehr erwartete man, dass fortgeschrittene Analyse-
methoden zusammen mit den neuen Erkentnissen anderer Experimente
unser derzeitiges Bild des Hadronspektrums verbessern werden.
Kapitel 1 führt in das Konzept der Mesonenspektroskopie ein. Die
Bildung von gebundenen Quark Anti-Quark Systemen erlaubt es, unsere
Messungen mit Eigenschaften gekoppelter Quantenzahlen zu verstehen
wie Spin, Ladungkojugation und Parität. Insbesondere werden kaonische
1IsospinI= Resonanzen klassifiziert, so wie es von der Gruppentheorie
2
vorgeschlagen wird. Es werden die Unterschiede zuI = 1 undI = 0
Zuständen aufgezeigt, die hauptsächlich aus u- und d-Quarks sowie
deren Anti-Quarks bestehen.
Das Kapitel führt auch in die Produktionsmechanismen ein, die ver-
wendet wurde, um die Resonanzen zu erzeugen. Zudem werden die
Ergebnisse vorangegangener Experimente kurz zusammengefasst. Dabei
wird ein besonderer Schwerpunkt auf die einfache Diffraktion von Strahl-
teilchen bei hohen Strahlenergien gelegt. Die wichtigsten Observablen
sowie die Haupteigenschaften der Produktionsprozesse werden erörtert,
um die Identifiaktion angeregter Strahlteilchen im COMPASS Spektrometer
zu verstehen.
Kapitel 2 beschreibt die wichtigsten Teile des COMPASS Spektrome