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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Evidence of Higgs Boson Production through Vector Boson Fusion

Cerio, Benjamin C. January 2015 (has links)
<p>The discovery of the Higgs boson in 2012 provided confirmation of the</p><p>proposed mechanism for preserving the electroweak $SU(2) \times U(1)$</p><p>gauge symmetry of the Standard Model of particle physics. It also</p><p>heralded in a new era of precision Higgs physics. This thesis presents a</p><p>measurement of the rate at which the Higgs boson is produced by vector</p><p>boson fusion in the $WW^{(\ast)}\rightarrow\,\ell\nu\ell\nu$ decay channel. With gauge boson couplings</p><p>in both the production and decay vertices, a VBF measurement in this</p><p>channel is a powerful probe of the $VVH$ vertex strength. Using</p><p>$4.5$~fb$^{-1}$ and $20.3$~fb$^{-1}$ of $pp$ collision data collected</p><p>at respective center-of-mass energies of 7 and $8 \tev$ in the ATLAS</p><p>detector, measurements of the statistical significance and the signal</p><p>strength are carried out in the Higgs mass range $100 \leq m_H \leq</p><p>200 \gev$. These measurements are enhanced with a boosted decision</p><p>tree that exploits the correlations between eight kinematic inputs in</p><p>order to separate signal and background processes. At the benchmark</p><p>Higgs mass of $125.36 \gev$, the significance of the data assuming the</p><p>background-only hypothesis to be true has been observed to be</p><p>$3.2\sigma$ ($2.7\sigma$ expected), constituting evidence of VBF Higgs boson</p><p>production. The measured signal strength (ratio of observed cross section times</p><p>branching ratio to that predicted by the SM) is</p><p>$1.27^{+0.53}_{-0.45}$. The inclusive cross section times</p><p>branching ratio is found to be $0.51^{+0.22}_{-0.17}$~pb at $\sqrts =</p><p>8 \tev$, consistent with the SM prediction of $0.34$~pb. No</p><p>significant deviations from the SM predictions for VBF Higgs boson</p><p>production are observed.</p> / Dissertation
2

Valuation of Mortgage Backed Securities with Prepayment using BDT Model and Monte Carlo Methods

Tang, Yuxiao 30 April 2015 (has links)
Mortgage backed securities are one of the most important asset classes available to fixed income investors. They are also essential to the functioning of the financial and housing market by providing liquidity to the home mortgage market. Proliferation and wide spread acceptance of mortgage backed securities resulted in a significant deduction of the interest rates for home mortgages. The 2007-2010 financial crisis sparked enhanced scrutiny of the accuracy of the pricing of mortgage backed securities. The purpose of the present thesis is to develop a computer based mathematical methodology to accurately price individual mortgages that are the fundamental assets underlying every mortgage backed security. The focus of this paper is to correctly account for inherent interest rate and prepayment risk. Default risk is not subject of this project. Interest rate risk is handled in the framework of the arbitrage free Black-Derman-Toy (BDT) model. Public Securities Association’s (PSA) model is used to simulate prepayment risk. Monte Carlo simulation methodology is developed to evaluate the properly discounted current value of the risky cash flows and hence value the mortgages. The computational algorithms are implemented in R.
3

Synthesis and Photophysical Properties of 3D Substituted Heterohelicenes and their Derivatives

Ying, Hu 05 November 2008 (has links)
No description available.
4

Evidence for the production of a Higgs boson in association with two top quarks with the ATLAS detector

Raine, John January 2018 (has links)
In this thesis, the search for the production of the Higgs boson in associationwith two top quarks is presented. The main focus of this work is on the analysis optimised for the decay of the Higgs boson to a b-quark pair. The analysis is performed using 36.1 fb−1 of ppcollision data at a centre of mass energy sqrt(s)=13 TeV collected by the ATLAS detector at the Large Hadron Collider during 2015 and 2016. The signal strength of ttH in relation to the Standard Model prediction for a Higgs boson with a mass of 125 GeV is measured to be mu(ttH) = 0.87 +0.64−0.61, with signal strengths greater than 2.0 excluded at the 95% confidence level. The combination of this analysis with searches targeting additional Higgs boson decay modes is subsequently presented. The measured signal strength in relation to the Standard Model prediction is mu(ttH) = 1.2 +/-0.3. This correspondsto an observed (expected) significance for ttH of 4.2sigma (3.8sigma), constituting evidence for the ttH production mode. Finally, a study into the ability to observe and model the colour connection of b-quarks in ttH(bb) and ttbar+jets events is presented. The jet pull angle observable is used to investigate the effect of colour connection on jet substructure. Such an observable is found to be sensitive to the underlying colour structure in events, showing differences between b-quarks which decay from a colour singlet in comparison to a colour octet. However, the effect is found to be small and a larger dataset is required to measure the effect in ttH events.
5

Measurement of the Higgs Boson Production Cross Section in Hadronic Final States in 13 TeV Proton-Proton Collisions with the ATLAS Detector

Drechsler, Eric 14 March 2018 (has links)
No description available.
6

Möjliga VA-lösningar förRunnö, Oskarshamnskommun

Dyberg, Johanna, Forsberg, Jenny January 2019 (has links)
Detta examensarbete analyserar möjliga lösningar för vatten och avlopp för en isoleradskärgårdsö, Runnö, i Oskarshamns kommun. Öns tillgång på vatten undersöks, där hänsyntas till de boendes behov av vattenförbrukning och VA-standard, vad de boende vill, samtöns geologiska och hydrologiska förutsättningar. Genom att kartlägga och jämföra olikatekniska lösningar för vatten och avlopp, och även ta hänsyn till Oskarshamns kommunsplaner samt nationella och globala miljömål, är målet med examensarbetet att ge förslag pålösningar för vatten och avlopp som kan nyttjas på ön inom en snar framtid. En genomgående litteraturstudie genomfördes om de tekniska möjligheter som finnstillgängliga i dagsläget, öns geologiska och hydrologiska förutsättningar samt om vilka lagar,regler och mål som behöver följas eller strävas mot. Litteraturstudien kompletterades meden serie intervjuer med de boende på ön, samtal med relevanta personer som arbetar förOskarshamns kommun samt telefon- och mejlkontakt med personer från yrken inom vattenoch avlopp som kunde komplettera studien med aktuell kunskap och erfarenhet. Därefterföljde ett studiebesök på Runnö där insamlad information kunde bekräftas eller dementeras.Studiebesöket erbjöd även en chans att undersöka de geologiska förhållanden som råder påön samt att tala med boende kring deras nuvarande lösningar och framtidsvisioner. Som ettsista steg beräknades avrinningsområdets grundvattenbalans för att uppskatta devattenresurser som finns, och hur de är fördelade över året. Resultat från studien visar bland annat att de vattenmängder som finns tillgängliga på ön idet specifika avrinningsområde studien behandlar är tillräckliga för de boendes behov. Storaoch geografiskt koncentrerade grundvattenuttag kan dock orsaka uttorkning av, ochsaltvatteninträngning i, brunnar inom avrinningsområdet oavsett magasinets storlek. Önsöversta marklager är hårt packad och fylld av sten, och undertill finns sandsten färgad röd avjärnoxid. Medan Oskarshamns kommun i sin VA-plan år 2015 föreslog en mer permanent lösning medvatten- och avloppsrör mellan fastlandet och ön, är de nu även öppna för lokala alternativ. De boende på Runnö är överens om att det viktigaste för dem är att ta vara på detraditionella sätten, däribland att fortsätta leva med en enkel sanitär standard. Från resultaten har slutsatsen dragits att dricksvatten framförallt bör baseras på lokaltbrunnsvatten, vid behov renat med filter. För övrig hushållsanvändning kan brunnsvattenkompletteras med insamlat regnvatten. För toalettavfall föreslås torra lösningar, exempelviskomposttoalett, frystoalett eller förbränningstoalett. Rening av BDT-vatten kan lösas medolika metoder; sluten tank, två-/tre-/fyrkammarbrunn och infiltrationsbädd,minireningsverk tillsammans med för- eller efterrening eller BDT-filteranläggning medtillhörande markbädd. / This bachelor thesis analyses how to best acquire water for drinking and for household use,and which water and wastewater solutions are the most beneficial for the island of Runnö onthe southeast coast of Sweden, belonging to the municipality of Oskarshamn. The purpose of this report is to analyse the island’s capacity and needs for water- and toiletsolutions from a geoscientific perspective with regard to geological and hydrologicalconditions, as well as the needs and visions of the people currently living there. Furthermore,the ambition is to analyse and compare various solutions with existing technologies,municipal plans and national and global environmental goals. Finally, the goal of this thesisis to present various examples of solutions that can be used on the island in the near future. A thorough literary examination of the technical possibilities of the field today, geologicaland hydrological conditions of the island and the laws, rules and goals related to the subjectwas conducted. This was complemented by a short series of interviews with people currentlyliving at Runnö, and conversations with professionals working for the municipality ofOskarshamn and companies relevant for the study. Information from the literaryexamination, as well as information from said interviews, were confirmed or disproven witha field study of the island. The field study offered a chance to see the conditions of the islandon site and talk with residents of the island about the water and toilet solutions currently inuse. Finally, a ground water balance calculation was made to receive an estimation of theislands ground water resources throughout the year. Results from the study show, amongst other things, that water resources on the island andmore specifically on the part of the island where the summer houses are located, aresufficient for the needs of the residents. Large and concentrated water extraction canhowever cause drying wells or saltwater intrusion regardless of the volume of the basin. Theground on the island is packed hard with rocks on top and sandstone, coloured with ironoxide, on the bottom. While the municipality of Oskarshamn in the year of 2015 suggested a more permanentsolution with water pipes between the mainland and Runnö, they are now also open to localoptions. The residents wish to keep the traditional ways of the island intact with a simple lifeas their core value. From those results the conclusions of this project are to mainly use local wells, possiblyfiltered, for drinking water, and wells for household water. Rainwater harvesting is an optionfor water use aside from drinking water. Compost or combustion toilets are recommended,combined with either a septic tank and soil infiltration or a closed container which needs tobe emptied regularly. There are several options for treatment of greywater; sand infiltrationcombined with a previous step to separate sludge, a closed tank for container-basedsanitation, wastewater treatment plants adapted for individual managed treatment in aseparate household, or bio modules/compact filters combined with sand infiltration.
7

Searching for the charged Higgs boson in the tau nu analysis using Boosted Decision Trees

Hallberg, Jesper January 2016 (has links)
his thesis implements a multivariate analysis in the current cut- based search for the charged Higgs bosons, which are new scalar particles predicted by several extensions to the Standard Model. Heavy charged Higgs bosons (mH± mtop) produced in association with a top quark de- caying via H± → τν are considered. The final state contains a hadronic τ decay, missing transverse energy and a hadronically decaying top quark. This study is based on Monte Carlo samples simulated at CM-energy √ s = 13 TeV for signal and backgrounds. The figure of merit to measure the improvement of the new method with respect to the old analysis is the separation between the signal and background distributions. Four mass points (mH± = 200, 400, 600, 1000 GeV) are considered, and an increase of the separation ranging from 2.6% (1000 GeV) to 29.2% (200 GeV) com- pared to the current cut-based analysis is found. / Denna studie implementerar en flervariabel-analys till den befintliga snitt-baserade analysen av laddade Higgs-bosoner, nya skal ̈arpartiklar fo ̈rutsagda av flertalet fo ̈rl ̈angningar av Standardmodellen. Studien antar tunga lad- dade Higgs-bosoner (mH± mtop) producerade tillsammans med en top- kvark som fo ̈rfaller via H± → τν. Sluttillst ̊andet best ̊ar av ett hadroniskt τ-so ̈nderfall, f ̈orlorad transversell energi och en hadroniskt so ̈nderfallande √ toppkvark. Studien a ̈r baserad p ̊a data f ̈or signal och bakgrund. Fo ̈r att ma ̈ta fo ̈rba ̈ttringen av analysens ka ̈nslighet anva ̈nds avst ̊and mellan bakgrundens och signalens distribu- tioner som godhetstal. Fyra masspunkter (mH± = 200, 400, 600, 1000 GeV) anva ̈nds, och en o ̈kning av avst ̊and fr ̊an 2.6% (1000 GeV) till 29.2% (200 GeV) hittades.
8

Modely úrokovej miery a ocenenie úrokových opcií / Models of interest rate and interest rate options valuation

Lendacký, Peter January 2010 (has links)
The interest rate dynamics is an important fundamental for valuation more complex structures of interest rate derivatives. The goal of this diploma thesis is to describe the use of models of interest rate for interest rate option pricing. The paper could be logically divided into two parts, the theoretical one and practical one. In the first part the essentials for pricing theory are introduced as risk neutrality, martingales, stochastic differential calculus, and theory of arbitrage. On their basis four basic yield curve models are derived, Vasicek model, model Cox-Ingersoll-Ross , Black-Derman-Toy and two factor Heath-Jarrow-Morton model. Second part provides the analysis of yields of U.S. Treasury bonds with different maturity. At the end CIR model and BDT binomial tree are used for valuation of option on 10 years yield.
9

Egenskap och precision av GNSS BeiDou, Navstar (GPS), GLONASS samt kombinationen av GPS/GLONASS

Mahdere, Yafet January 2021 (has links)
Eftersom att både GNSS GPS och GLONASS har många likheter så finns möjlighet att utnyttja systemen i kombination. Dock föreligger olikheter vilket gör att systemen inte är fullkomlig kompatibla med varandra. Diskrepans i koordinater och tidsram utgör ett stort hinder för att kombinera dessa system. Men lösningar för koordinatstransformering har tagits fram för att eliminera dessa divergenser (Roßbach, 2001) BeiDou GNSS system till skillnad från GNSS GPS/GLONASS är ett av det senaste etablerade navigationssystem, vilket ställer frågor för användare om systemets kvalitéer och brister. Denna studie behandlar väldigt översiktligt om hur BeiDou systemet tillkom och bakgrunden, karaktärer samt ambitionen som är framlagt för systemet. BeiDou som ursprungligen kallades för COMPASS hade inte samma ändamål som GLONASS och GPS att tillfredsställa sina användare med globalt navigationssystem, intentionen med systemet var mestadels för positioneringssystem som skulle användas regionalt och för militära ändamål, men med tiden ökade ambitionen hos tillverkaren och en ny plan alstrades. planen var att satsa på att bli en av världsledande positionering och navigationssystem, och det skulle etableras och utnyttjas världen över. GLONASS och NAVSTARs GPS vilka är stora konkurrenter av produktutveckling inom rymd teknologi, har framställt världens mest noggranna och effektiva satellitsystemen. Även om ändamålen för dessa systemen hade sin utgångspunkt för applikation inom det militära avseende, har de gjort tillgängliga för diverse civil användning. GNSS GPS/GLONASS kan i vissa fall visa brister på uppkopplingshastighet men också mätningsprecision vid användning på egen hand, detta p.g.a. att antalet synliga och uppnåbara satelliter är begränsande. Detta har gett upphov till vidare studier inom systemens karaktärer samt implementering av kombination GNSS GPS/GLONASS. Emedan både systemen tillsammans består av 48 satelliter, att hitta tillfredställande antal satelliter under alla omständigheter underlättas. Systemen innehöll implikationer i sina grundinställningar som försvårar tillämpning av dessa i kombination. Satelliterna skickar information om sina positioner på två olika metoder, PZ-90 för GLONASS och WGS-84 för GPS. Metoderna är väldigt lika varandra med skiljer sig någorlunda i sättet de utför sina beräkningar. Denna skiljaktighet skapades då systemen ej hade som avsikt att samarbeta och eventuellt integrera med varandra vilket gjorde att utvecklingen av båda GNSS gick isär. Detta innebär att transformation av satellitinformation är nödvändigt för att uppnå tillförlitliga lösningar, då GNSS ska sammanställas och användas integrerat.
10

Event categorisation and Machine-learning Techniques in Searches for Higgs Boson Pairs in the ATLAS Experiment at the LHC

Emadi, Milads January 2023 (has links)
This thesis investigates the pair production of Higgs bosons (di-Higgs events) at the ATLAS experiment in the Large Hadron Collider (LHC), focusing on the channel where one Higgs boson decays into two bottom quarks and the other decays into two tau leptons. The main objective was to determine whether introducing a split in the invariant mass of the decay products from the two Higgs bosons (the di-Higgs mass) and using this as an analysis variable improves the sensitivity of the Boosted Decision Tree (BDT) machine learning algorithm to the di-Higgs signal. A mass split was performed at 350 GeV, and the BDT algorithm was trained on both the split and un-split data sets, where the split data set included a high-mass region (di-Higgs mass above 350 GeV) using the Standard Model Higgs boson coupling constant of 1 and a low-mass region (di-Higgs mass below 350 GeV) using the enhanced coupling constant of 10 to create a low-mass region more sensitive to the signal.  The results showed that the BDT algorithm training performed on the split data set provided a 3.6% improvement in the exclusion limits, indicating an improvement in the algorithm's sensitivity to the di-Higgs signal compared to the training performed on the un-split data set. This finding suggests that the introduction of a split at 350 GeV can enhance the accuracy and efficiency of machine learning algorithms in detecting di-Higgs boson production at the LHC.  The improvement in sensitivity was attributed to the enhanced discrimination between signal and background events provided by the split in the di-Higgs mass analysis variable. The improved separation between the signal and background events lead to a higher signal-to-background ratio and a corresponding increase in the BDT algorithm's sensitivity to the di-Higgs signal.  In conclusion, this thesis provided evidence that introducing a split in the di-Higgs mass analysis variable can improve the sensitivity of machine learning algorithms to the di-Higgs signal in the channel where one Higgs boson decays into two bottom quarks and the other into two tau particles. This finding has important implications for future research on di-Higgs boson production at the LHC and could lead to more accurate and efficient detection of this rare and important process.

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