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New dark matter candidates motivated from superstring derived unification

Description: Perturbative gauge coupling unification in realistic superstring models suggest the existence of additional heavy down-type quarks, beyond the minimal supersymmetric standard model. The mass scale of the heavy down-type quarks is constrained by requiring agreement between the measured low energy gauge parameters and the string-scale gauge coupling unification. These additional quarks arise and may be stable due to the gauge symmetry breaking by ``Wilson lines`` in the superstring models. We argue that there is a window in the parameter space within which this down-type quark is a good candidate for the dark matter. 18 refs.
Date: March 1, 1996
Creator: Chang, Sanghyeon; Coriano, C. & Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

A new scheme for the running coupling constant in gauge theories using Wilson loops

Description: We propose a new renormalization scheme of the running coupling constant in general gauge theories defined by using the Wilson loops. The renormalized coupling constant is obtained from the Cretz ratio in lattice simulations and the corresponding perturbative coefficient at the leading order. The latter calculation is performed by adopting the zeta-function resummation techniques. We make a benchmark test of our scheme in quenched QCD with the plaquette gauge action. The running of the coupling constant is determined by applying the step scaling procedure. Using several methods to improve the statistical accuracy, we show that the running coupling constant can be determined in a wide range of energy scales with relatively small number of gauge configurations.
Date: January 1, 2009
Creator: Kurachi, Masafumi; Bilgici, Erek; Flachi, Antonion; Itou, Etsuko; David Lin, C J; Matsufuru, Hideo et al.
Partner: UNT Libraries Government Documents Department

A separate SU(2) for the third family: Topflavor

Description: The authors consider the extended electroweak gauge group SU(2){sub 1}xSU(2){sub x}xU(1){sub Y} where the first and second families of fermions couple to SU(2){sub 1} while the third family couples to SU(2){sub 2}. Bounds based on precision electroweak observables and heavy gauge boson searches are placed on the new parameters of the theory. The extra gauge bosons can be as light as about a TeV and can be discovered at future colliders such as the NLC and LHC for a wide range of the parameter space. FCNC interactions are also considered.
Date: October 17, 1996
Creator: Muller, D. J. & Nandi, S.
Partner: UNT Libraries Government Documents Department

Gaugino condensation, loop corrections and S-duality constraint

Description: This talk is a brief review of gaugino condensation in superstring effective field theories and some related issues (such as renormalization of the gauge coupling in the effective supergravity theories and modular anomaly cancellation). As a specific example, we discuss a model containing perturbative (1-loop) corrections to the K{umlt a}hler potential and approximate S-duality symmetry.
Date: November 1, 1996
Creator: Saririan, K.
Partner: UNT Libraries Government Documents Department

State of physics at the end of the 20. century: Massive neutrinos?

Description: A brief review of neutrino masses is presented with focus on how masses might appear in unified models. A fall 1996 status report of the LSND (Liquid Scintillator Neutrino Detector) experiment at Los Alamos is given; the statistical evidence for neutrino oscillations is becoming stronger. A summary of a unified model based on SO(18) shows possible complications in understanding neutrino masses.
Date: October 1, 1997
Creator: Slansky, R.
Partner: UNT Libraries Government Documents Department

Summary talk: Gauge bosons self interactions

Description: A review is given of the theoretical expectations of the self couplings of gauge bosons and of the present experimental information on the couplings. The possibilities for future measurements are also discussed.
Date: March 31, 1995
Creator: Hinchliffe, I.
Partner: UNT Libraries Government Documents Department

Probing new physics in B Penguins

Description: Constraints placed on physics beyond the Standard Model from the recent CLEO observation of the inclusive decay B {yields} X{sub s}{gamma} are summarized. Further searches for new physics using the process B {yields} X{sub s}l{sup +}l{sup {minus}} are discussed.
Date: February 1, 1995
Creator: Hewett, J.L.
Partner: UNT Libraries Government Documents Department

New phenomena beyond both the standard model and MSSM

Description: The Standard Model (SM) is in complete agreement with present experimental data. Nevertheless, it is believed to leave many questions unanswered, and this belief has resulted in numerous attempts to find a more fundamental underlying theory. One key ingredient in the extrapolation of the SM to higher energies is to identify the complete particle spectrum at the electroweak scale. Two popular examples of theories which populate the TeV scale with a plethora of new particles are supersymmetry and technicolor. This has resulted in extensive searches for super- and techni-particles, which have been reported elsewhere at this meeting. In this talk, the author identifies other possible manifestations of new physics, and discusses their implications on hadron collider physics.
Date: July 1, 1995
Creator: Hewett, J.L.
Partner: UNT Libraries Government Documents Department

Logarithmic unification from symmetries enhanced in the sub-millimeter infrared

Description: In theories with TeV string scale and sub-millimeter extra dimensions the attractive picture of logarithmic gauge coupling unification at 10{sup 16} GeV is seemingly destroyed. In this paper we argue to the contrary that logarithmic unification can occur in such theories. The rationale for unification is no longer that a gauge symmetry is restored at short distances, but rather that a geometric symmetry is restored at large distances in the bulk away from our 3-brane. The apparent ''running'' of the gauge couplings to energies far above the string scale actually arises from the logarithmic variation of classical fields in (sets of) two large transverse dimensions. We present a number of N = 2 and N = 1 supersymmetric D-brane constructions illustrating this picture for unification.
Date: August 21, 1999
Creator: Arkani-Hamed, Nima; Dimopoulos, Savas & March-Russell, John
Partner: UNT Libraries Government Documents Department

AdS orbifolds and Penrose limits

Description: In this paper we study the Penrose limit of AdS{sub 5} orbifolds. The orbifold can be either in the pure spatial directions or space and time directions. For the AdS{sub 5}/{Lambda} x S{sup 5} spatial orbifold we observe that after the Penrose limit we obtain the same result as the Penrose limit of AdS{sub 5} x S{sup 5}/{Lambda}. We identify the corresponding BMN operators in terms of operators of the gauge theory on R x S{sup 3}/{Lambda}. The semi-classical description of rotating strings in these backgrounds have also been studied. For the spatial AdS orbifold we show that in the quadratic order the obtained action for the fluctuations is the same as that in S{sup 5} orbifold, however, the higher loop correction can distinguish between two cases.
Date: December 9, 2002
Creator: Alishahiha, Mohsen; Sheikh-Jabbari, Mohammad M. & Tatar, Radu
Partner: UNT Libraries Government Documents Department

(De)Constructing dimensions

Description: We construct renormalizable, asymptotically free, four dimensional gauge theories that dynamically generate a fifth dimension.
Date: April 2, 2001
Creator: Arkani-Hamed, Nima; Cohen, Andrew G. & Georgi, Howard
Partner: UNT Libraries Government Documents Department

`t Hooft anomaly matching for discrete symmetries

Description: The authors show how to extend the `t Hooft anomaly matching conditions to discrete symmetries. They check these discrete anomally matching conditions on several proposed low-energy spectra of certain strongly interacting gauge theories. The excluded examples include the proposed chirally symmetric vacuum of pure N = 1 supersymmetric yang-Mills theories, certain non-supersymmetric confining theories and some self-dual N = 1 supersymmetric theories based on exceptional groups.
Date: May 1, 1998
Creator: Csaki, C. & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

Gauge theories from D7-branes over vanishing 4-cycles

Description: We study quiver gauge theories on D7-branes wrapped over vanishing holomorphic 4-cycles. We investigate how to incorporate O7-planes and/or flavor D7-branes, which are necessary to cancel anomalies. These theories are chiral, preserve four supercharges and exhibit very rich infrared dynamics. Geometric transitions and duality in the presence of O-planes are analyzed. We study the Higgs branch of these quiver theories, showing the emergence of fuzzy internal dimensions. This branch is related to noncommutative instantons on the divisor wrapped by the seven-branes. Our results have a natural application to the recently introduced F(uzz) limit of F-theory.
Date: December 16, 2010
Creator: Franco, Sebastian; /Santa Barbara, KITP; Torroba, Gonzalo & /SLAC /Stanford U., Phys. Dept.
Partner: UNT Libraries Government Documents Department

Exact Lattice Supersymmetry

Description: We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of N = 4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.
Date: March 31, 2009
Creator: Catterall, Simon; Kaplan, David B. & Unsal, Mithat
Partner: UNT Libraries Government Documents Department

The quest for new phenomena

Description: The Standard Model of particle physics has been very successful in describing experimental data with great precision. With the exception of some neutrino anomalies, there is no data that is in disagreement with it. Nevertheless, the model is regarded as incomplete and unsatisfactory. There is no explanation of the pattern of quark and lepton masses and, possibly more important, no understanding of the scale of electroweak interactions. Electroweak symmetry breaking is implemented in the Standard Model from the presence of a scalar electroweak doublet, the Higgs field, that acquires a vacuum expectation value of order 250 GeV and leaves as a remnant one physical state, the electrically neutral Higgs boson whose mass is not predicted. In this talk, the author compares the techniques used at, and capabilities of, various facilities in searching for new phenomena. The author emphasizes the cases where information from more than one facility may be needed to fully explore the physics.
Date: December 1, 1996
Creator: Hinchliffe, I.
Partner: UNT Libraries Government Documents Department

Electro symmetry breaking and beyond the standard model

Description: The development of the Standard Model of particle physics is a remarkable success story. Its many facets have been tested at present day accelerators; no significant unambiguous deviations have yet been found. In some cases, the model has been verified at an accuracy of better than one part in a thousand. This state of affairs presents our field with a challenge. Where do we go from here? What is our vision for future developments in particle physics? Are particle physicists` recent successes a signal of the field`s impending demise, or do real long-term prospects exist for further progress? We assert that the long-term health and intellectual vitality of particle physics depends crucially on the development of a new generation of particle colliders that push the energy frontier by an order of magnitude beyond present capabilities. In this report, we address the scientific issues underlying this assertion.
Date: May 1, 1995
Creator: Barklow, T.; Dawson, S.; Haber, H.E. & Siegrist, J.
Partner: UNT Libraries Government Documents Department

Meeting the constraint of neutrino-Higgsino mixing in gravity unified theories

Description: In Gravity Unified Theories all operators that are consistent with the local gauge and discrete symmetries are expected to arise in the effective low-energy theory. given the absence of multiplets like 126 of S0(10) in string models, and assuming that B - L is violated spontaneously to generate light neutrino masses via a seesaw mechanism, it is observed that string theory solutions genetically face the problem of producing an excessive {nu}{sub L} - {tilde H} mixing mass at the GUT scale, which is some nineteen orders of magnitude larger than the experimental bound of 1 MeV. The suppression of {nu}{sub L} - {tilde H} mixing, like proton longevity, thus provides one of the most severe restraints on the validity of any string theory solution. We examine this problem in a class of superstring derived models. We find a family of solutions within this class for which the symmetries of the models and an allowed pattern of VEVs, surprisingly, succeed in adequately suppressing the neutrino-Higgsino mixing terms. At the same time they produce the terms required to generate small neutrino masses via seesaw mechanism.
Date: February 1, 1997
Creator: Faraggi, A.E. & Pati, J.C.
Partner: UNT Libraries Government Documents Department

Outstanding junior investigator program. [Final technical report, 8/1/92-10/31/97]

Description: Much of the authors work over the past five years has been aimed at bridging the gap between the exactly supersymmetric world of string theories and the world that is actually observed. Her report discusses the following subjects: (1) supersymmetry breaking; related work on the mass hierarchy and the relation between supersymmetry and grand unified theories; distinguishing between supersymmetric models; and the fundamental question of how gauge theories arise from D-branes.
Date: December 18, 1999
Creator: Randall, Lisa & Rosenberg, Leslie
Partner: UNT Libraries Government Documents Department


Description: This four-day workshop focused on the wide variety of approaches to the non-perturbative physics of QCD. The main topic was the formulation of non-Abelian gauge theory in orbit space, but some other ideas were discussed, in particular the possible extension of the Maldacena conjecture to nonsupersymmetric gauge theories. The idea was to involve most of the participants in general discussions on the problem. Panel discussions were organized to further encourage debate and understanding. Most of the talks roughly fell into three categories: (1) Variational methods in field theory; (2) Anti-de Sitter space ideas; (3) The fundamental domain, gauge fixing, Gribov copies and topological objects (both in the continuum and on a lattice). In particular some remarkable progress in three-dimensional gauge theories was presented, from the analytic side by V.P. Nair and mostly from the numerical side by O. Philipsen. This work may ultimately have important implications for RHIC experiments on the high-temperature quark-gluon plasma.
Date: June 1, 2000
Creator: Van Baal, P.; Orland, P. & Pisarski, R.
Partner: UNT Libraries Government Documents Department

Fermion frontiers in vector lattice gauge theories: Proceedings. Volume 8

Description: The inclusion of fermions into simulations of lattice gauge theories is very difficult both theoretically and numerically. With the presence of Teraflops-scale computers for lattice gauge theory, the authors wanted a forum to discuss new approaches to lattice fermions. The workshop concentrated on approaches which are ripe for study on such large machines. Although lattice chiral fermions are vitally important to understand, there is not technique at hand which is viable on these Teraflops-scale machines for real-world problems. The discussion was therefore focused on recent developments and future prospects for QCD-like theories. For the well-known fermion formulations, the Aoki phase in Wilson fermions, novelties of U{sub A}(1) symmetry and the {eta}{prime} for staggered fermions and new approaches for simulating the determinant for Wilson fermions were discussed. The newer domain-wall fermion formulation was reviewed, with numerical results given by many speakers. The fermion proposal of Friedberg, Lee and Pang was introduced. They also were able to compare and contrast the dependence of QCD and QCD-like SUSY theories on the number of quark flavors. These proceedings consist of several transparencies and a summary page from each speaker. This should serve to outline the major points made in each talk.
Date: November 1, 1998
Partner: UNT Libraries Government Documents Department

Holographic Systematics of D-brane Inflation

Description: We provide a systematic treatment of possible corrections to the inflaton potential for D-brane inflation in the warped deformed conifold. We consider the D3-brane potential in the presence of the most general possible corrections to the throat geometry sourced by coupling to the bulk of a compact Calabi-Yau space. This corresponds to the potential on the Coulomb branch of the dual gauge theory, in the presence of arbitrary perturbations of the Lagrangian. The leading contributions arise from perturbations by the most relevant operators that do not destroy the throat geometry. We find a generic contribution from a non-chiral operator of dimension {Delta} = 2 associated with a global symmetry current, resulting in a negative contribution to the inflaton mass-squared. If the Calabi-Yau preserves certain discrete symmetries, this is the dominant correction to the inflaton potential, and fine-tuning of the inflaton mass is possible. In the absence of such discrete symmetries, the dominant contribution comes from a chiral operator with {Delta} = 3/2, corresponding to a {phi}{sup 3/2} term in the inflaton potential. The resulting inflationary models are phenomenologically identical to the inflection point scenarios arising from specific D7-brane embeddings, but occur under far more general circumstances. Our strategy extends immediately to other warped geometries, given sufficient knowledge of the Kaluza-Klein spectrum.
Date: November 5, 2008
Creator: Baumann, Daniel; /Harvard U., Phys. Dept. /Princeton U.; Dymarsky, Anatoly; /Stanford U., Phys. Dept.; Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC et al.
Partner: UNT Libraries Government Documents Department

Superpotentials for Quiver Gauge Theories

Description: We compute superpotentials for quiver gauge theories arising from marginal D-Brane decay on collapsed del Pezzo cycles S in a Calabi-Yau X. This is done using the machinery of A{sub {infinity}} products in the derived category of coherent sheaves of X, which in turn is related to the derived category of S and quiver path algebras. We confirm that the superpotential is what one might have guessed from analyzing the moduli space, i.e., it is linear in the fields corresponding to the Exts of the quiver and that each such Ext multiplies a polynomial in Exts equal to precisely the relation represented by the Ext.
Date: June 10, 2005
Creator: Aspinwall, Paul S.; /Stanford U., Phys. Dept. /SLAC /Duke U., CGTP; Fidkowski, Lukasz M. & /Stanford U., Phys. Dept.
Partner: UNT Libraries Government Documents Department