Next-to-minimal super-symmetric extensions of the Standard Model (SM) predict the existence of several non-SM like Higgs bosons. The process pp→a1h±→4b+W involves the production and the decay of a spin-0 charged Higgs boson and a CP-odd Higgs boson a1 which can have a sizable cross section in the NMSSM. The invariant masses of these intermediate bosons can be reconstructed from the four momenta of the final state particles using mass minimization algorithms. This thesis presents a cut-based analysis of two mass scenarios and specialized algorithms that are capable of recovering the signal in a large background arising from Standard Model processes such as ttbar. The analysis is tested with a realistic ATLAS detector simulation investigating trigger efficiencies and probing several jet reconstruction algorithms.

I present the results of a search for pair production of scalar top quarks (~t1) in an R-parity violating supersymmetric scenario using 322 pb_1 of pp collisions at ps = 1.96 TeV collected by the upgraded Collider Detector at Fermilab. I assume each ~t1 decays into a tau lepton and a b quark, with branching ratio B, and search for final states containing either an electron or a muon from a leptonic tau decay, a hadronically decaying tau lepton, and two or more jets. Two candidate events pass my final selection criteria, consistent with the expectation from standard model processes. I present upper limits on the cross section times branching ratio squared (~t1~t1)B2 as a function of the stop mass m(~t1). Assuming B = 1, I set a 95% confidence level limit m(~t1) > 153 GeV=c2. These limits are also fully applicable to the case of a pair produced third generation scalar leptoquark that decays into a tau lepton and a b quark.

The low-energy supersymmetry phenomenology for specific classes of string compactifications is investigated given that the low-energy physics may provide a clue as to the structure of the fundamental theory at high energy scales. The one-parameter model (OPM), a highly constrained subset of minimal Supergravity where all the soft-supersymmetry breaking terms may be fixed in terms of the gaugino mass, is studied, in addition to a three-family Pati-Salam model constructed from intersecting D6-branes. Furthermore, the phenomenology of gravity mediated supersymmetry breaking F-theory SU(5) and SO(10) models, as well as F-SU(5) models with vector- like particles, are examined. We determine the viable parameter space that satisfies all the latest experimental constraints, including the most recent WMAP relic neutralino abundance observations, and find it to be consistent with the CDMS II and other concurrent direct-detection experiments. Moreover, we compute the gamma-ray flux and cross-sections of neutralino annihilations into gamma-rays and compare to the published Fermi-LAT satellite telescope measurements. In F-theory SU(5) and SO(10) models, we predict the exact small deviation of the gaugino mass relation at two-loop level near the electroweak scale, which can be tested at the colliders. More- over, in F-SU(5), we predict the precise deviations from the mSUGRA gaugino mass relations due to the presence of the vector-like particles, also testable at the colliders. The compilation of all these results form a comprehensive collection of predictions with which to evaluate these string models alongside anticipated experimental dis- coveries in the coming decade.

Supersymmetry (SUSY) is the most motivated scenario beyond the Standard Model (SM) addressing the problems of the SM in an elegant way by establishing a symmetry which relates matter particles to interaction particles and vice versa. The simplest phenomenologically viable supersymmetric theory is the Minimal Supersymmetric Standard Model (MSSM) which can be accommodated to minimal Supergravity (mSuGra) theory in order to both take gravity into account and constrain its parameter space. CMS detector is one of the general purpose detectors constructed at LHC (Large Hadron Collider) which targets to search for SUSY signal. This thesis presents a search strategy for SUSY in three different fully hadronic jet topologies with the CMS detector. Di-jet, 3-jet, and 4-jet event topologies offer clear signatures for SUSY searches and the key SUSY decay modes of these jet topologies appear to be squark pair production, squark-gluino production, and gluino pair production, respectively. In these jet topologies, an important kinematical variable named alpha, &amp / #945 / is used to separate SUSY signal test points from the SM background events including QCD, EWK (Electroweak), and invisible decay of Z boson processes. Alpha variables are found to be very useful in terms of enhancing SUSY signal while rejecting all QCD events. Discriminating power of alpha variables are shown in terms of signal-to-background and signal significance calculations and the results are found to be promising which further encourage searches for SUSY signal in jet event topologies with the early CMS data at 1 f b^{&amp / #8722 / 1} integrated luminosity.

We consider three distinct categories of supersymmetric scenarios with heavy scalars and light gauginos. First, we investigate the SO(10) SUSY GUTs, and locate MSSM parameter space regions that satisfy GUT scale Yukawa unification, which is a distinct feature of these models. Then taking example SO(10) cases, we perform a Monte Carlo study with toy detector simulation at 14 TeV at the LHC on the no $met$ leptonic channels 2,3 leptons + $ge$4 jets and show that discovery is possible with $sim$1 fb$^{-1}$ of integrated luminosity. We also demonstrate the feasibility of invariant mass endpoint measurements for $sim$100 fb$^{-1}$. Furthermore, in a cosmological context, we propose that SO(10) scenarios with excess neutralino relic abundance can be made WMAP-compatble by assuming neutralino decays to axinos, and show that there are various axino/axion cold and warm dark matter admixtures which can be consistent with non-thermal leptogenesis requirements for the thermal re-heat temperature. Afterwards we complement the SO(10)s with the string-inspired G$_2$-MSSM and focus point mSUGRA scenarios and perform a full simulation search of these at $sqrt{s} =$ 14 TeV at the LHC with the CMS detector where the main production mechanism is through gluino pair production and the final states are cheracterized by all-hadronic topologies (including $b$s and $t$s). Through the design of six prototype all-hadronic selection paths and using the CMS High Lever Trigger paths with highest significance (including the $b$-enriched ones), we find that all but one model benchmarks are accessible with 100 pb$^{-1}$ integrated luminosity. We present the results as a function of the gluino mass considering the major detector systematic effects.

The Large Hadron Collider located at CERN is currently the most powerful particle accelerator and ATLAS is an experiment designed to exploit the high energy proton-proton collisions provided by the LHC. It opens a unique window to search for new physics at very high energy, such as supersymmetry, a postulated symmetry between fermions and bosons. Supersymmetry can provide a solution to the hierarchy problem and a candidate for Dark Matter. It also predicts the existence of new particles with masses around 1 TeV, thus reachable with the LHC. This thesis presents a new search for supersymmetry in a previously unexplored search channel, namely the production of charginos and neutralinos directly decaying to electroweak on-shell gauge bosons, with two leptons, jets, and missing transverse momentum in the final state. The search is performed with proton-proton collision data at a center of mass energy of √s = 8 TeV recorded with the ATLAS experiment in 2012. The design of a signal region sensitive to the new signal is presented and a data driven technique to estimate the Z+jets background is developed. Precise measurements of hadronic jet energies are crucial to search for new physics with ATLAS. A precise energy measurement of hadronic jets requires detailed knowledge of the pulse-shapes from the hadron calorimeter signals. Performance of the ATLAS Tile Calorimeter in this respect is presented using both pion test-beams and proton–proton collision data. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2 and Paper 4: Technical report from the  ATLAS experiment.</p>

No description available.

Στόχος της διατριβής είναι η αναζήτηση υπερσυμμετρικών λύσεων με προέλευση από την Μ θεωρία και τη θεωρία χορδών στις 10-διαστάσεις, με συνακόλουθη μελέτη των συνεπειών τους στις 4-διαστάσεις μέσω της αντιστοιχίας βαρύτητας/βαθμίδας. Στο πρώτο βήμα προχωρούμε σε συστηματική κατασκευή υπερσυμμετρικών βαρυτικών λύσεων της υπερβαρύτητας σε διάφορες διαστάσεις με μειωμένη Lorentzian ολονομία. Η κατασκευή μας βασίζεται στην εισαγωγή χρονικής εξάρτησης στις παραμέτρους moduli των Riemannian αντιγράφων. Συνεπώς οδηγούμαστε σε D-διάστατες υπερσυμμετρικές λύσεις κενού με Lorentzian ομάδα ολονομίας της μορφής G×RD-2. Στο δεύτερο βήμα προσεγγίζουμε τους 5-διάστατους χώρους Sasaki-Einstein, οι οποίοι παρεμβάλονται μεταξύ της S5 και του T1,1. Χρησιμοποιώντας τους 5-διάστατους αυτούς χώρους σαν βάση κατασκευάζουμε 6-διάστατους υπερσυμμετρικούς κώνους, οι οποίοι στη συνέχεια θα αποτελέσουν τα δομικά στοιχεία για την κατασκευή λύσεων της 10-διάστατης υπερβαρύτητας τύπου ΙΙΒ για συσσωματώματα από D3 και D5-βράνες. Στο τρίτο βήμα μελετάμε τις δυϊκές βαρυτικές λύσεις του κλάδου Coulomb που αντιστοιχούν σε μια marginally παραμορφωμένη N=4 θεωρία Yang-Mills. Μέσα από μια αλληλουχία από Τ δυϊκότητες και μετατοπίσεις συντεταγμένων κατασκευάζουμε το δυϊκο βαρυτικό υπόβαθρο, ουσιαστικά παρουσιάζοντας μια γενική μεθοδολογία. Εξετάζουμε ενδελεχώς το ζήτημα της υπερσυμμετρίας και πως αυτή ελαττώνεται από Ν=4 σε Ν=1. Στη συνέχεια ανιχνεύουμε την γεωμετρία μέσα από τον υπολογισμό του βρόχου Wilson για ζεύγος βαρέων quark-antiquark, αποκαλύπτοντας φαινόμενα θωράκισης και εγκλωβισμού για το δυναμικό. / Our main objective is the quest of supersymmetric solutions coming from M theory and 10-dim string theory together with the study of their implications in 4-dim through the AdS/CFT correspondence. As a first step we proceed in a systematic construction of supersymmetric supergravity solutions in diverse dimensions with reduced Lorentzian holonomy. Our construction is based on time dependence insertion over the moduli parameters of the Riemannian counterparts. We end up with D-dim supersymmetric vacuum solutions with Lorentzian holonomy group of the semidirect product type G×RD-2. In the second step we get near the 5-dim Sasaki-Einstein spaces which interpolate between S5 and T1,1. Using those 5-dim spaces as a base we construct the 6-dim supersymmetric cones which in turn will form the building blocks for the consequent construction of supersymmetric type-IIB supergravity solutions representing a stack of D3- and D5-branes. In the last step we study the gravity duals of the Coulomb branch of marginally deformed N=4 Yang-Mills theory. Through a sequence of T dualities and coordinate shifts we construct the dual supergravity background, in other words present a general methodology. We examine in detail the issue of supersymmetry and in particular the way it is reduced from N=4 to N=1. We probe the geometry through the computation of the expectation value of the Wilson loop operator for a pair of quark-antiquark, reviling confining and complete screening phenomena for the potential.

Three different aspects of the sinh-Gordon model are explored in this thesis. We begin, in chapter one, with a summary of the model and the necessary background. Chapter two studies the model with two boundary conditions. Two approaches are presented to investigate the reflection factors off the boundaries and the energy of the theory. In chapter three, perturbation theory is developed to study the theory with one general boundary condition. A contribution to the quantum reflection factor is obtained and compared with the result obtained for the special boundary condition. Chapters four and five investigate the supersymmetric extension of the model in the presence of a single boundary. Firstly, the classical limits of the supersymmetric reflection matrices are checked. The exact reflection factors are studied perturbatively up to the second order of the coupling constant. Secondly, the perturbation theory and the path integral formalism are employed in the supersymmetric model to study the quantum reflection factors. We conclude with a brief sixth chapter describing the outlook for further investigations.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Qaisar Shafi, Dept. of Physics & Astronomy. Includes bibliographical references.