Spelling suggestions: "subject:"hadron"" "subject:"padron""
121 |
A search for technicolor at the Large Hadron ColliderLove, Jeremy R January 2012 (has links)
Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The Standard Model of particle physics provides an accurate description of all experimental data to date. The only unobserved piece of the Standard Model is the Higgs boson, a consequence of the spontaneous breaking of electroweak symmetry by the Higgs mechanism. An alternative to the Higgs mechanism is proposed by Technicolor theories which break electroweak symmetry dynamically through a new force. Technicolor predicts many new particles, called Technihadrons, that could be observed by experiments at hadron colliders. This thesis presents a search for two of the lightest Technihadrons, the ρT and ωT .
The Low-Scale Technicolor model predicts the phenomenology of these new states. The ρT and ωT are produced through qq annihilation and couple to Standard Model fermions through the Drell-Yan process, which can result in the dimuon final state. The ρT and ω T preferentially decay to the πT and a Standard Model gauge boson if kinematically allowed. Changing the mass of the πT relative to that of the ρT and ωT affects the cross section times branching fraction to dimuons. The ρT and ωT are expected to have masses below about 1 TeV.
The Large Hadron Collider (LHC) at CERN outside of Geneva, Switzerland, produces proton-proton collisions with a center of mass energy of 7 TeV. A general purpose high energy physics detector ATLAS has been used in this analysis to search for Technihadrons decaying to two muons. We use the ATLAS detector to reconstruct the tracks of muons with high transverse momentum coming from these proton-proton collisions.
The dimuon invariant mass spectrum is analyzed above 130 GeV to test the consistency of the observed data with the Standard Model prediction. We observe excellent agreement between our data and the background only hypothesis, and proceed to set limits on the cross section times branching ratio of the ρT and ωT as a function of their mass using the Low-Scale Technicolor model. We combine the dielectron and dimuon channels to exclude masses of the ρT and ωT between 130 GeV - 480 GeV at 95% Confidence Level for masses of the πT between 50 GeV - 480 GeV. In addition for the parameter choice of m(π T ) = m(ρT /ω T )- 100 GeV, 95% Confidence Level limits are set excluding masses of the ρT and ωT below 470 GeV. This analysis represents the current world's best limit on this model. / 2031-01-01
|
122 |
Differential cross section measurements in H→ WW and prospects of observing H→ bb in future LHC runs at the ATLAS detectorGlaysher, Paul Christopher Frederick January 2016 (has links)
The highly celebrated discovery of a new particle with a mass of 125 GeV in proton-proton collisions by the ATLAS and CMS experiments at the CERN Large Hadron Collider in 2012 has been shown to be compatible with the Standard Model description of the Higgs boson. However, in order to fully verify the Standard Model nature of the Higgs boson, most of its properties still remain to be measured. Such measurements include differential cross section measurements, which are shown here for the H→WW decay channel and the coupling of the Higgs boson to bottom quarks, for which a study of future prospects is presented. Differential fiducial cross section measurements of the Higgs boson were performed in the H → WW*→lvlv channel at the ATLAS detector with 20 fb−1 of √s = 8 TeV collision data. For Higgs bosons produced by gluon-gluon fusion, the cross section is measured as a function of kinematic variables, including transverse momentum and rapidity of the Higgs boson, as well as the number of jets associated with the Higgs event. The obtained distributions are unfolded to a fiducial volume using a two-dimensional iterative Bayesian algorithm. The measured fiducial differential cross sections are compared to predictions from Monte Carlo generators. The total cross section measured in the fiducial volume defined by the charged lepton and neutrino kinematic properties is 36.0 ± 9.7 fb. Additionally the jet-veto efficiency in the fiducial volume is extracted from the differential cross sections. An analysis is presented of Higgs boson production and decay into bottom quarks in association with a vector boson at the ATLAS detector for the future high-luminosity LHC with proton-proton collisions at √s = 14 TeV. The vector bosons are reconstructed from Z→l+l− or W→lv final states, where l is an electron or muon. The analysis uses generator-level Monte Carlo samples to which efficiency and resolution smearing functions are applied. These reproduce the expected resolution of the upgraded ATLAS detector for the foreseen amount of pile-up due to multiple overlapping proton-proton collisions. The analysis of the ZH(→ l+l−b¯b) channel is presented and results are combined with the WH(→lvb¯b) channel from a corresponding study. For an integrated luminosity of 300 fb−1 using an average pile-up of 60, the expected significance is 3.9 σ with an expected error on the signal strength of 25%. Likewise, for 3000 fb−1 using an average pileup of 140 the expected significance is 8.8 σ , and the error on the signal strength is expected to be about 15%.
|
123 |
Etude de la production inclusive de J/ψ dans les collisions pp et Pb-Pb √sNN =5.02 TeV avec le spectromètre à muon de l'expérience ALICE au LHC / Study of the inclusive J/ψ production in pp and Pb-Pb collisions at √sNN = 5.02 TeV with the ALICE muon spectrometer at the LHCAudurier, Benjamin 05 October 2017 (has links)
La production des états charmonia (par exemple le J/ψ et le ψ(2S)) est l’une des sondes étudiées pour comprendre les propriétés du Plasma de Quarks et de Gluons (PQG) formé dans les collisions d’ions lourds à très haute énergie. En effet, la présence d’un milieu déconfiné est susceptible de modifier le taux de production des charmonia par effet d’écrantage de couleur de la paire de quarks charme-anti-charme. Une telle suppression fut déjà observée dans les collisions d’ions lourds aux énergies du SPS et du RHIC. Dans les collisions Pb-Pb à √sNN = 2.76 TeV au LHC, une suppression relative du taux de production du J/ψ par rapport à celui mesuré dans les collisions pp normalisé aux nombres de collisions binaires proton-proton (facteur de modification nucléaire RAA) fut aussi mesurée. Cette suppression est cependant moins importante que ce qui fut observé à plus petites énergies dans le centre de masse. Ceci peut s’expliquer par la présence d’un nouveau mécanisme de production, la recombinaison de quarks charme et anticharme déconfinés au moment de l’expansion hydrodynamique du PQG ou durant la phase d’hadronisation. Dans cette thèse, nous présentons les résultats de la production de J/ψ dans les collisions pp et Pb-Pb, mesurée par le détecteur ALICE à √sNN = 5.02 TeV à rapidité avant dans le canal de décroissance dimuonique. La section efficace de production mesurée dans les collisions pp est comparée à différents modèles théoriques et est utilisée pour calculer le RAA en collisions Pb-Pb, lui-même comparé à différentes prédictions théoriques ainsi qu’aux précédentes mesures. / The production of charmonium states (for instance J/ψ and ψ(2S)) is one of the probes studied to investigate the properties of the Quark-Gluon Plasma (QGP) formed in high-energy heavy-ion collisions. Indeed, the presence of a deconfined medium should modify the charmonium production yield, due to the color screening of the charm quark anti-quark potential. Such a suppression was already observed in heavy-ion collisions at SPS and RHIC energies. In Pb-Pb collisions at √sNN = 2.76 TeV at the LHC, a clear suppression of the J/ψ yield with respect to the one measured in binary-scaled pp collisions (nuclear modification factor RAA) was observed, but much smaller than that at lower collision energies. This observation can be explained by the presence of a new production mechanism, the (re)combination of deconfined charm and anti-charm quarks during the hydrodynamical expansion of the QGP or at the hadronization stage. In this thesis, we report on the results of the J/ψ production in pp and Pb-Pb collisions measured with the ALICE detector √sNN = 5.02 TeV at forward rapidity in the dimuon channel. The cross-section in pp collisions is compared to various model calculations, and is used to compute the RAA in Pb-Pb collisions, which is also compared to theoretical predictions as well as to previous measurements.
|
124 |
Search for diboson resonance production at sqrt(s) = 8 TeV with the ATLAS detectorMarsden, Stephen Philip January 2015 (has links)
A search for heavy exotic diboson resonances decaying to llqq final states is presented using pp collision data collected with the ATLAS detector at the Large Hadron Collider. The analysis uses a data sample corresponding to an integrated luminosity of 20.3 fb^-1 at sqrt(s) = 8 TeV collected between April and December 2012. No significant excess of data events over the predicted Standard Model background is observed and 95% confidence level upper limits are set on the product of the production cross-section and the branching ratio for spin-2 Kaluza-Klein gravitons predicted by the bulk Randall-Sundrum model and for Extended Gauge Model W’ bosons. These results are subsequently combined with limits obtained from searches using the lvll, lvqq, and qqqq final states, and new mass limits are set on both signal models.
|
125 |
Search for the pentaquark Θ+ via the π- p → K- X reaction at J-PARC / J-PARCにおけるπ- p → K- X反応を用いたペンタクォークΘ+の探索Moritsu, Manabu 23 January 2015 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18673号 / 理博第4022号 / 新制||理||1580(附属図書館) / 31606 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 教授 谷森 達, 准教授 成木 恵 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM
|
126 |
Photoproduction of Λ* Resonances using the CLAS DetectorShrestha, Utsav 03 June 2021 (has links)
No description available.
|
127 |
Inclusive hadron production in electron-positron collisions with center-of-mass energies from 50 to 61.4 GeVMattson, Mark Edward 19 September 2008 (has links)
The K⁰, K*(892), p⁰(770) and Φ(1020) mesons along with the Λ° baryon have been observed in the TRISTAN energy region of 50 to 61.4 GeV using a data sample of 245.4 pb⁻¹. Their multiplicities and total cross sections are found and compared with the results from experiments at other center-of-mass energies. The multiplicities are compared with various theoretical and phenomenological models. The differential cross sections for the K⁰ and Λ⁰ are calculated and compared with other experiments. Measurements of the ratio of production of vector mesons to vector plus pseudoscalar mesons and the ratio of the production of excited ss̄ quark pairs to the production of excited uū plus dd̄ quark pairs are compared with other experiments along with the phenomenological predictions. The HERWIG Monte Carlo is tuned with regard to the inclusive production of hadrons. / Ph. D.
|
128 |
Measurement of the total W- and Z-boson production cross sections in pp collisions at 2.76 TeV with the ATLAS detectorGasnikova, Ksenia 14 June 2018 (has links)
Es werden Messungen der totalen Wirkungsquerschnitte der Prozesse pp → W/Z → ll′ in Endzuständen mit Elektronen und Myonen präsentiert. Für diese Analyse werden Daten, die im Jahr 2013 mit dem ATLAS-Detekor am LHC bei einer Schwerpunktsenergie von √s= 2.76 TeV aufgezeichnet wurden und einer integrierten Luminosität von pb−1 entsprechen, verwendet.
In dieser Analyse werden mehrere Quellen systematischer Unsicherheiten berücksichtigt. Die Untergründe werden sowohl mittels Simulationen (für elektroschwache und tt ̄ Un- tergründe) als auch mithilfe datengetriebener Methoden (für den Multi-Jet Untergrund) abgeschätzt. Die Resultate der Elektron- und Myon-Kanäle werden kombiniert und ergeben die folgenden Wirkungsquerschnitte:
sigma_fid(W → lν) = 2206.3±20.2(stat.)±10.6(sys.)±68.4(lumi.)[pb],
sigma_fid(Z → ll) = 200.4±6.1(stat.)±0.3(sys.)±6.2(lumi.)[pb].
Die kombinierten Wirkungsquerschnitte werden zur Berechnung der Wirkungsquerschnitts- Verhältnisse W/Z und W+/W− benutzt.
Die Ergebnisse werden mit QCD-Berechnungen unterschiedlicher Ordnungen verglichen. Der Einfluss dieser Messung auf Partonverteilungsfunktionen (parton distribution func- tions, PDFs) wird abgeschätzt. Die gesamte Unsicherheit dieser Messungen ist vergleich- bar mit den Unsicherheiten aktueller PDFs, weshalb diese Analyse zur Einbeziehung in zukünftige PDF-Bestimmungen geeignet ist.
Außerdem wurden Studien zur Frozen Showers Methode zur schnelleren Simulation von Ereignissen im ATLAS-Detektor durchgeführt. Es wurde eine neue Methode zur Gener- ierung einer Frozen Showers Bibliothek entwickelt, die eine Reduzierung der für diesen Abschnitt benötigten Zeit erlaubt. / Measurements of the total pp → W/Z → ll′ cross sections in the electron and muon
s = 2.76 TeV with the ATLAS detector at the LHC (in 2013), corresponding to a total integrated luminosity of 4
channels are presented. Data collected at a center-of-mass energy
pb−1, are used for this analysis.
In this measurement, several sources of systematic uncertainties are estimated. The back-
ground contribution is estimated using simulation (for electroweak and tt ̄ backgrounds) as well as data-driven methods (for the multijet background). The combined results for electron and muon channels provide the following cross sections:
sigma_fid(W → lν) = 2206.3±20.2(stat.)±10.6(sys.)±68.4(lumi.)[pb],
sigma_fid(Z → ll) = 200.4±6.1(stat.)±0.3(sys.)±6.2(lumi.)[pb].
The combined cross sections are used for the calculation of the W/Z and W+/W− cross section ratios.
These results are compared with different orders of QCD calculations. The effect of the addition of the measured cross sections to the parton density functions (PDF) is estimated. The total uncertainty of the measurements is comparable to the current global PDF uncer- tainties, which makes them applicable for future PDF determination.
Additionally, studies of the Frozen Showers method for fast simulation have been per- formed. A new method of Frozen Showers library generation, allowing to reduce time spend on this stage, is developed.
|
129 |
Resolution Studies for the Micro Vertex Detector of the PANDA Experiment and the Reconstruction of Charmed Mesons for Specific Hadronic Channels / Auflösungsstudien für den Mikro-Vertex-Detektor des PANDA Experiments und die Rekonstruktion von Charm-Mesonen für spezielle hadronische KanäleJäkel, René 17 December 2009 (has links) (PDF)
The PANDA experiment is planned as part of the extended GSI facility FAIR to investigate hadronic reactions in antiproton-proton annihilations. An excellent beam quality and high luminosity is expected which allows the investigation of hadronic reactions such as the spectroscopy of the charmonium system. To ensure different studies of hadronic systems an universal detector is being designed, the PANDA detector. A high resolution Micro Vertex Detector (MVD), as part of the whole setup, is an important component of the track and vertex reconstruction.
A mayor part of this work were simulation studies to investigate the resolution ability of the vertex detector. For this the development and implementation of reconstruction algorithms and their integration to the track and vertex reconstruction were an essential part to allow the detailed study of the resolution of the MVD and the whole apparatus under realistic assumptions. The track and vertex reconstruction ability of the detector is shown exemplarily for the channels antiproton-proton into two charged pions and into J/psi and photon.
The expected hadronic background for physics observables requires a high selection power of the experimental setup, especially for the investigation of the charmonium system above the DD(bar) threshold. For this particular energy region no experimental data exist and the PANDA experiment can contribute to understand the binding of charmed mesonic systems. Charmonium states can decay to open-charm channels which provide a clear signature in the detector from the charged D-Meson decays. In this work the high selection ability of the experimental setup was investigated for two reaction channels. Under the assumption of an expected low reaction cross section the clear identification of the DD(bar) decay channel was shown, even for the presence of a huge hadronic background. This allows a clear identification of the DD(bar) decay channel and mayor background resources for this channel were discussed. / Das PANDA Experiment wird Teil der geplanten Ausbaustufe FAIR als
Erweiterung zur GSI und wird die Untersuchung von hadronischen
Reaktionen in Antiproton-Proton Annihilationen ermöglichen. Durch die
zu erwartende exzellente Strahlqualität und hohe Luminosität ergeben sich
vielfältige Möglichkeiten zur Untersuchung von
Hadronenwechselwirkungen, wie beispielsweise die genaue Spektroskopie
des Charmoniumsystems. Um vielfältige
Untersuchungen verschiedenster hadronischer Systeme zu gewährleisten,
wurde der Aufbau eines universellen Detektors geplant, des PANDA
Detektors. Dazu ist ein hochauflösender Vertexdetektor (MVD) eine wichtige
Komponente, um im Zusammenspiel mit weiteren Detektorkomponenten zur Spur- und Vertexrekonstruktion beitragen zu können.
Im Rahmen dieser Arbeit wurden detaillierte Simulationen durchgeführt,
die das Auflösungsvermögen des Vertexdetektors
charakterisieren, ganz besonders im Hinblick auf die Rekonstruktion
verschiedener physikalischer Kanäle. Dafür war die Entwicklung und
Implementierung von Algorithmen zur Rekonstruktion der zu erwartenden
Detektordaten und deren Integration in den Spurfit zur
Teilchenrekonstruktion eine Grundvoraussetzung. Dadurch ist es
möglich das Auflösungsvermögen des MVD und des gesamten
experimentellen Aufbaus unter realistischen Bedingungen zu testen und zu
optimieren. Die Spur- und Vertexrekonstruktion wird anhand der Kanäle
Antiproton-Proton nach zwei geladenen Pionen und nach J/Psi Photon
evaluiert.
Der zu erwartende hadronische Untergrund stellt hohe Anforderungen an
die Selektionskraft des experimentellen Aufbaus, bezüglich der
physikalischen Observablen, dar.
Dies ist besonders für die Untersuchung des Charmoniumsystems oberhalb
der DD(quer)-Schwelle von Bedeutung, wofür kaum experimentelle
Untersuchungen vorliegen und der PANDA Detektor zukünftig einen
entscheidenden Beitrag zum Verständnis gebundener mesonischer Systeme
beitragen kann. Zuständen im Charmoniumsystem ist es erlaubt in
Open-Charm-Kanäle zu zerfallen, die eine eindeutige experimentelle
Signatur mittels der D-Zerfälle in geladene Teilchen im Detektor erlauben.
Im Rahmen dieser Arbeit konnte anhand zweier grundlegender Reaktionen
gezeigt werden, dass selbst unter
ungünstigen Annahmen über den zu erwartenden Wirkungsquerschnitt, der noch nicht schwellennah vermessen wurde, das stark
unterdrückte Signal gegenüber Untergrundereignissen hinreichend
angereichert werden kann. Dies erlaubt eine klare Identifizierung des
DD(quer)-Ausgangskanales, wobei die wesentlichen Untergrundbeiträge
identifiziert und diskutiert werden.
|
130 |
Física de Pomeron a altas energiasMachado, Magno Valério Trindade January 2002 (has links)
Neste trabalho investigamos a física de Pomeron, tanto em sua formulação perturbativa dada pela Cromodinâmica Quântica como o aspecto não-perturbativo dado pela teoria de Regge. Estes formalismos teóricos levam em consideração o fato que o Pomeron porta os números quânticos do vácuo e deve dominar o espalhamento entre partículas em altas energias. Partindo do formalismo de dipolos de cor, estudamos a interação perturbativa usual corrigida por efeitos de unitariedade em altas energias para os processos DIS e Drell- Yan, determinando a importância destas correções para ambos processos. Referente ao Pomeron não-perturbativo, investigamos os aspectos do modelo de múltiplos espalhamentos, o qual também contribui também para a unitariedade no setor suave. Dado os resultados similares entre modelos QCD e de Regge na descrição de DIS difrativo, propomos um novo observável, o coeficiente angular difrativo da função de estrutura difrativa, que permitirá discriminar dinâmicas subjacentes ao processo. Finalmente estudamos a fenomenologia associada à truncagem da série assintótica advinda do formalismo BFKL, e a utilizamos para descrever os principais observáveis em colisões hadrônicas e elétron-próton.
|
Page generated in 0.0263 seconds