35 research outputs found
Track Segments within Hadronic Showers using the CALICE AHCal
Using the high granular CALICE analog hadron calorimeter (AHCal) a tracking
algorithm capable of identifying MIP-like tracks within hadronic showers is
presented. Such an algorithm provides excellent tools for detector calibration
and for studies of the substructure of hadronic showers. The properties of the
identified tracks are used as observables for a Monte-Carlo to data comparison.Comment: 6 pages, 9 figures, LCWS2010 Proceedin
Mass and Cross Section Measurement of light-flavored Squarks at CLIC
We present a study of the prospects for the measurement of TeV-scale
light-flavored right-squark masses and the corresponding production cross
section at a 3 TeV e+e- collider based on CLIC technology. The analysis,
performed in the framework of the CLIC Conceptual Design Report, is based on
full Geant4 simulations of the CLIC_ILD detector concept, including standard
model physics background and machine related hadronic background from
two-photon processes. The events are reconstructed using particle flow event
reconstruction, and the mass is obtained from a template fit built from
generator-level simulations with smearing to parametrize the detector response.
For an integrated luminosity of 2/ab, a statistical precision of 5.9 GeV,
corresponding to 0.52%, is obtained for unseparated first and second generation
right squarks. For the combined cross section, a precision of 0.07 fb,
corresponding to 5%, is obtained.Comment: To appear in the proceedings of LCWS11, Granada, Spain, September
201
Light-flavor squark reconstruction at CLIC
We present a simulation study of the prospects for the mass measurement of
TeV-scale light-flavored right-handed squarks at a 3 TeV e+e- collider based on
CLIC technology. In the considered model, these particles decay into their
standard-model counterparts and the lightest neutralino, resulting in a
signature of two jets plus missing energy. The analysis is based on full GEANT4
simulations of the CLIC_ILD detector concept, including Standard Model physics
backgrounds and beam-induced hadronic backgrounds from two-photon processes.
The analysis serves as a generic benchmark for the reconstruction of highly
energetic jets in events with substantial missing energy. Several jet finding
algorithms were evaluated, with the longitudinally invariant kt algorithm
showing a high degree of robustness towards beam-induced background while
preserving the features typically found in algorithms developed for e+e-
collisions. The presented study of the reconstruction of light-flavored squarks
shows that for TeV-scale squark masses, sub-percent accuracy on the mass
measurement can be achieved at CLIC.Comment: 11 pages, 5 figures, accepted for publication in EPJ
Mass measurement of right-handed scalar quarks and time measurement of hadronic showers for the compact linear collider
Der Compact Linear Collider (CLIC) ist ein Konzept eines 48.3km langen e+ e- Beschleunigers mit einer Schwerpunktsenergie von 3TeV. Sein Ziel ist sowohl die Präzisionsvermessung bereits bekannter, als auch die Entdeckung bislang unbekannter Teilchen. Der International Large Detector (ILD) ist eines der Detektorkonzepte, die speziell für die Anwendung des Particle Flow Algorithmus entworfen wurde. Der Inhalt dieser Arbeit gliedert sich in zwei Teilbereiche, die beide im Kontext von CLIC stehen.
Im ersten Teil dieser Arbeit wird die Messung der Zeitstruktur hadronischer Schauer in Kalorimetern mit Wolframabsorber, wie es auch im ILD Konzept für CLIC benutzt wird, präsentiert. Das beinhaltet die Entwicklung und Konstruktion eines kleinen Testbeam-Experimentes namens Tungsten Timing Testbeam (T3B), welches aus lediglich 15 Szintillator Kacheln der Dimension 30mm x 30mm x 5mm besteht. Diese werden mit Silicon Photomultipliern ausgelesen, welche wiederum mit USB Oszilloskopen verbunden sind. T3B wurde während der Testreihen am CERN in den Jahren 2010 und 2011 hinter dem Prototypen des analogen hadronischen Kalorimeters (W-AHCal) der CALICE Kollaboration platziert. Die gewonnenen Daten wurden mit Simulationsergebnissen verglichen, die mit den drei verschiedenen Modellen hadronischer Schauer der Geant4 Simulation gewonnen wurden: QGSP_BERT, QGSP_BERT_HP und QBBC. Die Ergebnisse der 60GeV Datennahme sind zumeist mit QBBC und QGSP_BERT_HP konsistent. Hingegen überschätzt QGSP_BERT wegen der fehlenden Präzisionsverfolgung von Neutronen die Häufigkeit später Energiedepositionen.
Im zweiten Teil wird einer der sechs Benchmark-Prozesse gezeigt, die im Rahmen des CLIC Conceptual Design Report die Detektor Leistungsfähigkeit am CLIC Beschleuniger gezeigt haben. Der vorgestellte Benchmark Prozess behandelt die Messung der Masse und des Wirkungsquerschnitts der Paarerzeugung von supersymmetrischen rechtshändigen skalaren Quarks (squarks). Im zugrundeliegenden SUSY Modell zerfallen diese fast ausschließlich in das leichteste Neutralino (fehlende Energie) und das zugehörige Standardmodell Quark (Jet). In der Analyse wird der Beam-generierte pile-up Untergrund von gamma gamma -> Hadronen durch die Anwendung der Hadronen Variante des kt-Algorithmus der FastJet-Bibliothek unterdrückt. Standardmodell Prozesse, die der Ereignisstopologie entsprechen, werden durch die Anwendung von Boosted Decision Trees, implementiert im Toolkit for Multivariate Analysis (TMVA), zurückgewiesen. Die Squark-Masse wird durch die Konstruktion der MC-Verteilung und dem folgenden Fit an die mit verschiedenen Squark-Massen generierten Templates extrahiert. Die Ergebnisse sind konsistent mit ihren Eingangswerten und zeigen, dass Massenmessungen von schweren, stark wechselwirkenden Teilchen bei CLIC mit Genauigkeiten von unter 1% möglich sind.The Compact Linear Collider (CLIC) is a concept for a 48.3km long e+ e- accelerator with a center-of-mass energy of 3TeV. Its purpose is the precise measurement of particles discovered by the LHC as well as the discovery of yet unknown particles. The International Large Detector (ILD) is one of its detector concepts which was specifically designed for the usage of the Particle Flow Algorithm. This thesis is divided into two parts, both within the context of CLIC.
In the first part of this thesis the unprecedented measurement on time structure of hadronic showers in calorimeters with tungsten absorber material, which is used in the ILD concept for CLIC, will be presented. It shows the development and the construction of a small testbeam experiment called Tungsten Timing Testbeam (T3B) which consists of only 15 scintillator tiles of 30mm x 30mm x 5mm, read out with Silicon Photomultipliers which in turn were connected to USB oscilloscopes. T3B was placed downstream of the CALICE tungsten analog hadron calorimeter (W-AHCal) during beam tests performed at CERN in 2010 and 2011. The resulting data is compared to simulation obtained with three different hadronic shower physics models of the \geant~simulation toolkit: QGSP_BERT, QGSP_BERT_HP and QBBC. The results from 60GeV high statistics run show that QBBC and QGSP_BERT_HP are mostly consistent with the testbeam data, while QBBC, which is lacking a sophisticated treatment of neutrons, overestimates the late energy depositions.
The second part of this thesis presents one out of the six benchmark processes that were part of the CLIC Conceptual Design Report (CDR) to verify the detector performance at CLIC. This benchmark process is the measurement of the mass and cross-section of two supersymmetric right-handed scalar quarks. In the underlying SUSY model these almost exclusively decay into the lightest neutralino (missing energy) and the corresponding standard model quark (jet). Within this analysis pile-up from beam induced background of gamma gamma -> hadron is rejected by choosing the hadron variant of the kt-algorithm as it is implemented in the FastJet library. Standard Model processes mimicking the signal event topography are rejected with a forest of Boosted Decision Trees using the Toolkit for Multivariate Analysis (TMVA). The squark mass is extracted by constructing the MC distribution and fitting it to templates generated with different squark masses. The results for the mass and cross-section are consistent with the input generator values and show that sub-percent accuracy for the masses of heavy strongly interacting particles can be reached with CLIC
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