15909902
GRAVITATIONAL MEDIATION OF SUPERSYMMETRY BREAKING IN SUPERSTRING THEORY
SUSY breaking and its mediation are among the most important problems of supersymmetric generalizations of the standard model. The idea of gravity-mediated SUSY breaking, proposed in 1982 by Arnowitt, Chamseddine and Nath, and independently by Barbieri, Ferrara and Savoy, fits naturally into superstring theory, where it can be realized at both classical as well as quantum levels. This talk is dedicated to Pran Nath on his 65th birthday.
120401055
Dilaton Couplings at Large Distances
Abstract The large-distance behaviour of dilaton couplings is studied within the framework of four-dimensional heterotic superstring theories. String loop corrections violate universality of dilaton and graviton couplings, increasing dilaton couplings at large distances. This implies a serious problem for string theories, unless a non-zero dilaton mass is generated.
14387997
N = 2 HETEROTIC SUPERSTRING AND ITS DUAL THEORY IN FIVE DIMENSIONS
Abstract We study quantum effects in five dimensions in heterotic superstring theory compactified on K 3 × S 1 and analyze the conjecture that its dual effective theory is eleven-dimensional supergravity compactified on a Calabi-Yau threefold. This theory is also equivalent to type II superstring theory compactified on the same Calabi-Yau manifold, in an appropriate large volume limit. In this limit the conifold singularity disappears and is replaced by a singularity associated to enhanced gauge symmetries, as naively expected from the heterotic description. Furthermore, we exhibit the existence of additional massless states which appear in the strong coupling regime of the heterotic theory and are related to a different type of singular points on Calabi-Yau threefolds.
120318508
Low-energy softly-broken supersymmetry
Abstract We consider supersymmetric low-energy lagrangians based on the gauge group SU(3) × SU(2) × U(1) × Ũ(1), where Ũ(1) is an additional axial group a la Fayet. Models with explicit soft breaking of supersymmetry are considered as an alternative to models with axial anomalies. We argue that soft breaking can be very efficient and illustrate this with a simple example in which the introduction of a negative mass squared term for only one scalar field leads to a phenomenologically interesting model.
120574302
Stability of supersymmetric ground state in chiral theories
Abstract The effective action for the scalar propagator is studied in supersymmetric chiral gauge theories. The form of the scalar potential ensures the stability of the supersymmetric ground state, even for large values of the coupling constant. It is found however, that the gluino condensation tends to destabilize the system. This may signal dynamical supersymmetry breaking.
62835109
Lectures on heterotic-type I duality
In the last couple of years, there has been remarkable progress in understanding non-perturbative aspects of string theories. The new ingredient is the discovery of various duality symmetries; these, in particular, invert the coupling constant and exchange perturbative states with non-perturbative solitonic excitations. Since inversion of the coupling involves the Planck constant ħ, duality symmetries can be realized only at the quantum level. Once the dual models are identified, non-perturbative dynamics of one model can be studied by means of the standard perturbative techniques in the other model.
115450618
A final focus design for the CERN linear collider CLIC
44644796
Technological Aspects of the LEP Low-Beta Insertions
In order to obtain the highest luminosity at LEP, it is necessary to use superconducting quadrupoles for the final vertical focusing of the beams. The low-beta structure is such that these quadrupoles must be virtually integrated into the experiments, imposing severe constraints on their design. In particular, at LEP these magnets must be iron-free, occupy minimum space in the transverse direction, and be supported together with other beam- and experiment-related equipment on mobile cantilever girders. The constraints are analyzed, and the proposed system is described.
107865879
Progress in the system design of the inner triplet of 70 mm aperture quadrupoles for the LHC low-beta insertions
45682848
Wigglers for Control of Beam Characteristics in LEP
Eight three-block dipole wigglers will be used in LEP to maximize luminosity and control other beam parameters such as emittance, damping rates at injection, energy spread and polarization. The excitation law for constant emittance (chosen, for example, to fill the dynamic aperture) and damping partition numbers is given. In contrast to conventional wigglers where orbit perturbation is avoided by means of a series of equal fields of alternate polarity, the LEP wigglers will use unequal fields and pole lengths. This allows one to retain a high potential asymptotic polarisation level together with an increased polarisation rate. The choice of the degree of field asymmetry is imposed by limitations on the transverse dimensions of the magnets and field levels, by polarisation requirements and by cost. A practical design of the proposed wiggler is presented.
107631253
AMPLITUDE DEPENDENT TUNE SPREAD AND FIELD ERRORS OF SUPERCONDUCTING LOW- QUADRUPOLES
The nonlinear effects in the lowinsertions are studied on the basis of the amplitude dependent tune spread. Several methods of estimating the tune spread in superconducting lowquadrupoles are compared. The main feature of these magnets is that the random errors dominate the multipole spectrum. The proposed methods allow an analysis of the final focus layout in the early stages of the insertion design, and point to the critical magnets and the dominant multipole errors.