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Closed-String Tachyon Condensation and the Worldsheet Super-Higgs Effect

Description: Alternative gauge choices for worldsheet supersymmetry can elucidate dynamical phenomena obscured in the usual superconformal gauge. In the particular example of the tachyonic E_8 heterotic string, we use a judicious gauge choice to show that the process of closed-string tachyon condensation can be understood in terms of a worldsheet super-Higgs effect. The worldsheet gravitino assimilates the goldstino and becomes a dynamical propagating field. Conformal, but not superconformal, invariance is maintained throughout.
Date: September 13, 2007
Creator: Horava, Petr; Horava, Petr & Keeler, Cynthia A.
Partner: UNT Libraries Government Documents Department

The Supersymmetric Fat Higgs

Description: Supersymmetric models have traditionally been assumed to be perturbative up to high scales due to the requirement of calculable unification. In this note I review the recently proposed `Fat Higgs' model which relaxes the requirement of perturbativity. In this framework, an NMSSM-like trilinear coupling becomes strong at some intermediate scale. The NMSSM Higgses are meson composites of an asymptotically-free gauge theory. This allows us to raise the mass of the Higgs, thus alleviating the MSSM of its fine tuning problem. Despite the strong coupling at an intermediate scale, the UV completion allows us to maintain gauge coupling unification.
Date: October 27, 2004
Creator: Harnik, Roni
Partner: UNT Libraries Government Documents Department

Duals for SU(N) SUSY Gauge Theories with an Antisymmetric Tensor: Five Easy Flavors

Description: I consider N = 1 supersymmetric SU(N{sub c}) gauge theories with matter fields consisting of one antisymmetric representation, five flavors, and enough antifundamental representations to cancel the gauge anomaly. Previous analyses are extended to the case of even N{sub c} with no superpotential. Using holomorphy I show that the theory has an interacting infrared fixed point for sufficiently large N{sub c}. These theories are interesting due to the fact that in going from five to four flavors the theory goes from a non-trivial infrared fixed point to confinement, in contradistinction to SUSY QCD, but in analogy to the behavior expected in non-SUSY QCD.
Date: December 16, 1997
Creator: Terning, John
Partner: UNT Libraries Government Documents Department

Stable SUSY breaking model with O(10) eV gravitino from combined D-term gauge mediation and U(1)' mediation

Description: We show a calculable example of stable supersymmetry (SUSY) breaking modelswith O(10) eV gravitino mass based on the combination of D-term gauge mediationand U(1)' mediation. A potential problem of the negative mass squared for theSUSY standard model (SSM) sfermions in the D-term gauge mediation is solvedby the contribution from the U(1)' mediation. On the other hand, the splittingbetween the SSM gauginos and sfermions in the U(1)' mediation iscircumvented bythe contributions from the D-term gauge mediation. Since the U(1)' mediation doesnot introduce any new SUSY vacua, we achieve a completely stable model underthermal effects. Our model, therefore, has no cosmological difficulty.
Date: December 17, 2007
Creator: Nakayama, Yu & Nakayama, Yu
Partner: UNT Libraries Government Documents Department

Gravitino Warm Dark Matter with Entropy Production

Description: Gravitinos with a mass in the keV range are an interesting candidate for warm dark matter. Recent measurements of the matter density of the universe and of cosmic structures at the dwarf galaxy scale rule out the simplest gravitino models with thermal freeze-out. We construct a model where the decay of the messenger particles that transmit the supersymmetry breaking to the observable sector generates the required entropy to dilute the gravitino relic density by the required factor of a few to come in line with observations. The model is natural, and requires only that the coupling of the messenger sector to the standard model be set so that the decay happens at the appropriate time.
Date: August 9, 2001
Creator: Baltz, Edward A. & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

R-Parity From the Heterotic String

Description: In T-duality invariant effective supergravity with gaugino condensation as the mechanism for supersymmetry breaking, there is a residual discrete symmetry that could play the role of R-parity in supersymmetric extensions of the Standard Model.
Date: December 7, 2004
Creator: Gaillard, Mary K.
Partner: UNT Libraries Government Documents Department

Modular invariant gaugino condensation in the presence of ananomalous U(1)*

Description: Starting from the previously constructed effective supergravity theory below the scale of U(1) breaking in orbifold compactifications of the weakly coupled heterotic string, we study the effective theory below the scale of supersymmetry breaking by gaugino and matter condensation in a hidden sector. Questions we address include vacuum stability and the masses of the various moduli fields, including those associated with flat directions at the U(1) breaking scale, and of their fermionic superpartners. The issue of soft supersymmetry-breaking masses in the observable sector presents a particularly serious challenge for this class of models.
Date: December 10, 2003
Creator: Gaillard, Mary K.; Giedt, Joel & Mints, Aleksey L.
Partner: UNT Libraries Government Documents Department

Flavorful supersymmetry

Description: Weak scale supersymmetry provides elegant solutions to many of the problems of the standard model, but it also generically gives rise to excessive flavor and CP violation. We show that, if the mechanism that suppresses the Yukawa couplings also suppresses flavor changing interactions in the supersymmetry breaking parameters, essentially all the low energy flavor and CP constraints can be satisfied. The standard assumption of flavor universality in the supersymmetry breaking sector is not necessary. We study signatures of this framework at the LHC. The mass splitting among different generations of squarks and sleptons can be much larger than in conventional scenarios, and even the mass ordering can be changed. We find that there is a plausible scenario in which the next-to-lightest superparticle is a long-lived right-handed selectron or smuon which decays into the lightest superparticle, a gravitino. This leads to the spectacularsignature of monochromatic electrons or muons in a stopper detector, providing strong evidence for the framework.
Date: December 13, 2007
Creator: Nomura, Yasunori; Nomura, Yasunori; Papucci, Michele & Stolarski, Daniel
Partner: UNT Libraries Government Documents Department

Dynamical (super) symmetry breaking

Description: Dynamical Symmetry Breaking (DSB) is a concept theoristsrely on very often in the discussions of strong dynamics, model building,and hierarchy problems. In this talk, I will discuss why this is such apermeating concept among theorists and how they are used in understandingphysics. I also briefly review recent progress in using dynamicalsymmetry breaking to construct models of supersymmetry breaking andfermion masses.
Date: October 3, 2000
Creator: Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

rSUGRA: Putting Nonuniversal Gaugino Masses on the (W)MAP

Description: In this talk, we investigate the relic density and direct detection prospects of rSUGRA, a simple paradigm for supersymmetry breaking that allows for nonuniversal gaugino masses. We present updated plots reflecting the latest cosmological measurements from WMAP.
Date: June 17, 2003
Creator: Birkedal-Hansen, Andreas
Partner: UNT Libraries Government Documents Department

Supergravity Analysis of Hybrid Inflation Model from D3--D7 System

Description: The slow-roll inflation is a beautiful paradigm, yet the inflaton potential can hardly be sufficiently flat when unknown gravitational effects are taken into account. However, the hybrid inflation models constructed in D = 4 N = 1 supergravity can be consistent with N = 2 supersymmetry, and can be naturally embedded into string theory. This article discusses the gravitational effects carefully in the string model, using D = 4 supergravity description. We adopt the D3--D7 system of Type IIB string theory compactified on K3 x T^2/Z_2 orientifold for definiteness. It turns out that the slow-roll parameter can be sufficiently small despite the non-minimal Kahler potential of the model. The conditions for this to happen are clarified in terms of string vacua. We also find that the geometry obtained by blowing up singularity, which is necessary for the positive vacuum energy, is stabilized by introducing certain 3-form fluxes.
Date: November 20, 2003
Creator: Koyama, Fumikazu; Tachikawa, Yuji & Watari, Taizan
Partner: UNT Libraries Government Documents Department

Recent Progress in Weakly-Coupled Heterotic String Phenomenology

Description: Some recent developments in the weakly-coupled heterotic string phenomenology are reviewed. We discuss several important issues such as dilaton/moduli stabilization, supersymmetry breaking (by hidden-sector gaugino condensation), gauge coupling unification (or the Newton's constant), the QCD axion, as well as cosmological problems involving the dilaton/moduli and the axion.
Date: July 28, 1997
Creator: Wu, Yi-Yen
Partner: UNT Libraries Government Documents Department

Duality after supersymmetry breaking

Description: Starting with two supersymmetric dual theories, we imagine adding a chiral perturbation that breaks supersymmetry dynamically. At low energy we then get two theories with soft supersymmetry-breaking terms that are generated dynamically. With a canonical K{umlt a}hler potential, some of the scalars of the ``magnetic`` theory typically have negative mass-squared, and the vector-like symmetry is broken. Since for large supersymmetry breaking the ``electric`` theory becomes ordinary QCD, the two theories are then incompatible. For small supersymmetry breaking, if duality still holds, the magnetic theory analysis implies specific patterns of chiral symmetry breaking in supersymmetric QCD with small soft masses.
Date: May 1, 1998
Creator: Shadmi, Yael & Cheng, Hsin-Chia
Partner: UNT Libraries Government Documents Department

Recent results from the search for new phenomena at D0

Description: We present results from several new searches for physics beyond the Standard Model. We describe a search based on the scalar sum of the transverse energy of the event, a global quantity nearly independent of the event topology. We summarize our searches for first generation leptoquarks into all three decay channels, eq{ovr eq}, eq{ovr {nu}q}, and {nu}q{ovr {nu}q} and note that this is the first time that the triumvirate of decay channels has been searched. We do not find any evidence for production of first generation leptoquarks and set a lower limit on the mass of the leptoquark of 175 GeV/c{sup 2} , assuming the decay is exclusively into eq{ovr eq}. We also present results from the first search for a third generation leptoquark with charge {+-}1/3. Again, we find no evidence for its existence for a mass less than 80 GeV/c{sup 2} Finally, we discuss one of our searches for supersymmetry, specifically the pair-production of {tilde e}, {tilde {nu}}, and {tilde {chi}}{sup 0}{sub 2} where the decay yields final states with two photons plus missing transverse energy (E{sub T}). We set limits on the production cross section ranging from 1 pb to 400 fb, depending on the mass. This analysis also sets a model-independent limit of {sigma} {center_dot} B(pp - {gamma}{gamma} {vert_bar} E{sub T} {vert_bar} X) < 185 fb at the 95% CL for E{sub T}{sup ({gamma})} > 12 GeV and {vert_bar}{eta}{vert_bar} < 1.1 T and E{sub T}> 25 GeV.
Date: June 1, 1997
Creator: Wightman, J.A.
Partner: UNT Libraries Government Documents Department

Final Year Project Report

Description: In the last years of this eighteen-year grant project, the research efforts have focused mostly on the study of off-shell representations of supersymmetry, both on the worldline and on the world- sheet, i.e., both in supersymmetric quantum mechanics and in supersymmetric field theory in 1+1-dimensional spacetime.
Date: June 20, 2013
Creator: Hubsch, Tristan
Partner: UNT Libraries Government Documents Department

A Historical Profile of the Higgs Boson

Description: The Higgs boson was postulated in 1964, and phenomenological studies of its possible production and decays started in the early 1970s, followed by studies of its possible productionin e{sup +} e{sup -}, {anti p}p and pp collisions, in particular. Until recently, the most sensitive searches for the Higgs boson were at LEP between 1989 and 2000, which have been complemented bysearches at the Fermilab Tevatron. The LHC has recently entered the hunt, excluding a Higgs boson over a large range of masses and revealing a tantalizing hint in the range 119 to125 GeV, and there are good prospects that the existence or otherwise of the Higgs boson will soon be established. One of the most attractive possibilities is that the Higgs bosonis accompanied by supersymmetry, though composite options have yet to be excluded. This article reviews some of the key historical developments in Higgs physics over the past half-century.
Date: January 31, 2012
Creator: Ellis, John; Gaillard, Mary K. & Nanopoulos, Dimitri V.
Partner: UNT Libraries Government Documents Department

One-loop soft supersymmetry breaking terms in superstring effective theories.

Description: We perform a systematic analysis of soft supersymmetry breaking terms at the one loop level in a large class of string effective field theories. This includes the so-called anomaly mediated contributions. We illustrate our results for several classes of orbifold models. In particular, we discuss a class of models where soft supersymmetry breaking terms are determined by quasi model independent anomaly mediated contributions, with possibly non-vanishing scalar masses at the one loop level. We show that the latter contribution depends on the detailed prescription of the regularization process which is assumed to represent the Planck scale physics of the underlying fundamental theory. The usual anomaly mediation case with vanishing scalar masses at one loop is not found to be generic. However gaugino masses and A-terms always vanish at tree level if supersymmetry breaking is moduli dominated with the moduli stabilized at self-dual points, whereas the manishing of the B-term depends on the origin of the mu-term in the underlying theory. We also discuss the supersymmetric spectrum of O-I and O-II models, as well as a model of gaugino condensation. For reference, explicit spectra corresponding to a Higgs mass of 114 GeV are given. Finally, we address general strategies for distinguishing among these models.
Date: November 1, 2000
Creator: Binetruy, Pierre; Gaillard, Mary K. & Nelson, Brent D.
Partner: UNT Libraries Government Documents Department

Supersymmetry and Superstring Phenomenology

Description: We briefly cover the early history of supersymmetry, describe the relation of SUSY quantum field theories to superstring theories and explain why they are considered a likely tool to describe the phenomenology of high energy particle theory beyond the Standard Model.
Date: May 5, 2008
Creator: Gaillard, Mary K; Gaillard, Mary K. & Zumino, Bruno
Partner: UNT Libraries Government Documents Department

M-theory through the looking glass: Tachyon condensation in the E8 heterotic string

Description: We study the spacetime decay to nothing in string theory and M-theory. First we recall a nonsupersymmetric version of heterotic M-theory, in which bubbles of nothing -- connecting the two E_8 boundaries by a throat -- are expected to be nucleated. We argue that the fate of this system should be addressed at weak string coupling, where the nonperturbative instanton instability is expected to turn into a perturbative tachyonic one. We identify the unique string theory that could describe this process: The heterotic model with one E_8 gauge group and a singlet tachyon. We then use worldsheet methods to study the tachyon condensation in the NSR formulation of this model, and show that it induces a worldsheet super-Higgs effect. The main theme of our analysis is the possibility of making meaningful alternative gauge choices for worldsheet supersymmetry, in place of the conventional superconformal gauge. We show in a version of unitary gauge how the worldsheet gravitino assimilates the goldstino and becomes dynamical. This picture clarifies recent results of Hellerman and Swanson. We also present analogs of R_\xi gauges, and note the importance of logarithmic CFT in the context of tachyon condensation.
Date: September 20, 2007
Creator: Horava, Petr; Horava, Petr & Keeler, Cynthia A.
Partner: UNT Libraries Government Documents Department

Bounds on Unparticles from the Higgs Sector

Description: We study supersymmetric QCD in the conformal window as a laboratory for unparticle physics, and analyze couplings between the unparticle sector and the Higgs sector. These couplings can lead to the unparticle sector being pushed away from its scale invariant fixed point. We show that this implies that low energy experiments will not be able to see unparticle physics, and the best hope of seeing unparticles is in high energy collider experiments such as the Tevatron and the LHC. We also demonstrate how the breaking of scale invariance could be observed at these experiments.
Date: May 20, 2007
Creator: Fox, Patrick J.; Rajaraman, Arvind & Shirman, Yuri
Partner: UNT Libraries Government Documents Department

Supersymmetry without the Desert

Description: Naturalness of electroweak symmetry breaking in weak scale supersymmetric theories may suggest the absence of the conventional supersymmetric desert. We present a simple, realistic framework for supersymmetry in which (most of) the virtues of the supersymmetric desert are naturally reproduced without having a large energy interval above the weak scale. The successful supersymmetric prediction for the low-energy gauge couplings is reproduced due to a gauged R symmetry present in the effective theory at the weak scale. The observable sector superpotential naturally takes the form of the next-to-minimal supersymmetric standard model, but without being subject to the Landau pole constraints up to the conventional unification scale. Supersymmetry breaking masses are generated by the F-term and D-term VEVs of singlet and U(1){sub R} gauge fields, as well as by anomaly mediation, at a scale not far above the weak scale. We study the resulting pattern of supersymmetry breaking masses in detail, and find that it can be quite distinct. We construct classes of explicit models within this framework, based on higher dimensional unified theories with TeV-sized extra dimensions. A similar model based on a non-R symmetry is also presented. These models have a rich phenomenology at the TeV scale, and allow for detailed analyses of, e.g., electroweak symmetry breaking.
Date: September 26, 2006
Creator: Nomura, Yasunori & Poland, David
Partner: UNT Libraries Government Documents Department

Models of Scherk-Schwarz Symmetry Breaking in 5D: Classification and Calculability

Description: The form of the most general orbifold breaking of gauge, global and supersymmetries with a single extra dimension is given. In certain theories the Higgs boson mass is ultraviolet finite due to an unbroken local supersymmetry, which is explicitly exhibited. We construct: a 1 parameter SU(3) \times SU(2) \times U(1) theory with 1 bulk Higgs hypermultiplet, a 2 parameter SU(3) \times SU(2) \times U(1) theory with 2 bulk Higgs hypermultiplets, and a 2 parameter SU(5) \to SU(3) \times SU(2) \times U(1) theory with 2 bulk Higgs hypermultiplets, and demonstrate that these theories are unique. We compute the Higgs mass and compactification scale in the SU(3) \times SU(2) \times U(1) theory with 1 bulk Higgs hypermultiplet.
Date: July 1, 2001
Creator: Barbieri, Riccardo; Hall, Lawrence J. & Nomura, Yasunori
Partner: UNT Libraries Government Documents Department

Target space supersymmetric sigma model techniques

Description: We briefly review the covariant formulation of the Green-Schwarz superstring by Berkovits, and describe how a detailed tree-level and one-loop analysis of this model leads, for the first time, to a derivation of the low-energy effective action of the heterotic superstring while keeping target-space supersymmetry manifest. The resulting low-energy theory is old-minimal supergravity coupled to tensor multiplet. The dilaton is part of the compensator multiplet.
Date: July 1, 1996
Creator: de Boer, Jan & Skenderis, Kostas
Partner: UNT Libraries Government Documents Department