15842113
Topological Amplitudes in Heterotic Superstring Theory
We show that certain heterotic string amplitudes are given in terms of correlators of the twisted topological (2,0) SCFT, corresponding to the internal sector of the N = 1 space-time supersymmetric background. The genus g topological partition function Fg corresponds to a term in the effective action of the form W2g, where W is the gauge or gravitational superfield. We study also recursion relations related to holomorphic anomalies, showing that, contrary to the type II case, they involve correlators of anti-chiral superfields. The corresponding terms in the effective action are of the form W2gΠn, where Π is a chiral superfield obtained by chiral projection of a general superfield. We observe that the structure of the recursion relations is that of N = 1 spacetime supersymmetry Ward identity. We give also a solution of the tree-level recursion relations and discuss orbifold examples.
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.
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.
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.
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.
118679470
Dependence Of LEP Acceptance On Low Beta Insertion Settings
56244495
Progress in the construction and testing of the 70 mm aperture quadrupole for the LHC low-b insertions
This paper reviews the current status and development of the one meter model of the 70 mm aperture quadrupole for the LHC low-p insertions. We describe the problems that were encountered in insulating the cable with an all Kapton system, the manufacture of the shaped end spacers, and coil winding and curing. We also present results of the short mechanical model of the magnet straight section which confirmed the soundness of the structural design and proved the tooling for the final magnet assembly.
123424297
The Choice of Spectrometer Magnets for LEP
Many experiments at LEP will require matching spectrometer magnets. In this report, guidelines are established for providing a starting point in the iterative process of choosing the best device for a particular detector. Magnets are compared in terms of their resolving power based on measurements of sagitta. This approach draws attention to the importance of detector size, and also helps to define the preferred areas of application of normal and superconducting technology. Although most emphasis is placed on the solenoid, toroids and dipoles are also discussed.
136548606
Analysis of the Performance of the Eight Superconducting Quadrupoles for the Lep Low-Beta Insertions
The LEP low-beta quadrupoles are iron-free superconducting magnets having a warm bore of 120 mm in diameter, an effective length of 2 m and a nominal gradient of 36 T m−l. The coils form a two-block approximation of the cosine 2θ distribution, and are wound from monolithic multifilamentary NbTi conductor; mechanical prestress is obtained by means of aluminium shrinking rings. Following manufacture and appraisal of a prototype magnet, eight series units have been produced by industry and thoroughly tested and measured prior to installation into LEP. In this paper, a brief description of the manufacturing technique is given, and the results of tests and measurements are presented and compared with the performance expected from calculations and previous experience. The analysis reveals the tolerances on field quality which can reasonably be obtained with this type of construction.
121954895
Test results of a variant-design LHC twin-aperture dipole magnet
Since 1989, KEK and CERN carried out jointly an experimental program in the frame of the R&D work for the LHC main dipole. The mechanical structure of this design is based on a separate coil/collar and "horizontally split iron" concept. A total of four single aperture and two twin-aperture 1 m long dipole magnets were built. The last twin-aperture magnet was tested at CERN, reaching a maximum field of 9.55 T at 1.9 K. This paper reports the magnet training performance and quench localization at 1.9 K and 4.5 K. The performance as a function of current ramp rate and measurements of the field quality are also reported.