852278
Note on Mediation of Supersymmetry Breaking from Closed to Open Strings
We discuss the mediation of supersymmetry breaking from closed to open strings, extending and improving previous analysis of the authors in Nucl. Phys. B 695 (2004) 103 [hepth/0403293]. In the general case, we find the absence of anomaly mediation around any perturbative string vacuum. When supersymmetry is broken by Scherk-Schwarz boundary conditions along a compactification interval perpendicular to a stack of D-branes, the gaugino acquires a mass at two loops that behaves as m1/2 � g 4 m 3/2 in string units, where m3/2 is the gravitino mass and g is the gauge coupling.
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.
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.
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.
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.
20721233
A design concept for the LHC insertion quadrupoles
It is noted that the low- beta insertion optics imposes severe constraints on the desired characteristics of the local quadrupoles. In order to obtain the necessary degree of focusing at the LHC (Large Hadron Collider), triplets made up of four 250 T/m superconducting quadrupoles, about 6- to 7-m long, are presently envisaged. The large value of the betatron functions through these magnets is such that, besides being the principal source of chromatic aberrations, errors in their gradient will also contribute significantly to the excitation of resonance in the circulating beams. The magnets should therefore provide a gradient field of very high quality. The relatively small number of quadrupoles involved means that the cost constraints are less binding on these than on the lattice magnets. Their single aperture also opens up the possibility of an approach different from that adopted for the regular twin-aperture quadrupoles. One of the design concepts being investigated involves the use of flat cable wound in rectangular blocks to approximate the required quadrupole producing current density. The characteristics of the magnet are described, as is the method of applying the required prestress to the winding.<<ETX>>
37031481
Progress in the development of the 1-m model of the 70 mm aperture quadrupole for the LHC low-/spl beta/ insertions
Within the LHC magnet development program Oxford Instruments has built a one metre model of the 70 mm aperture low-/spl beta/ quadrupole. The magnet features a four layer coil wound from two 8.2 mm wide graded NbTi cables, and is designed for 250 T/m at 1.9 K. The magnet has previously been tested between 4.5 K and 23 K. In this paper we review the magnet rebuild and the subsequent tests. Results on magnet training at 43 K and 1.9 K are presented along with the results related to quench protection studies. We also present the first results of magnetic field measurements done at room and liquid nitrogen temperatures.
118472339
A study of longitudinal polarization at LEP
118152947
SUPERCONDUCTING MAGNETS FOR A SUPER LHC
Feasibility studies underway for the upgrade of luminosity and energy of the LHC indicate the need for intensifying the R&D on long, accelerator-type magnets that target the highest possible fields. The major technological aspects of such magnets will be presented, together with the expected physical limits, some envisaged solutions and open questions. Ongoing programmes to reach for the maximum practical operational fields will be reviewed. The report will conclude with a tentative analysis of the cost issues related to the use of proposed new materials and technologies. What is a Super LHC? After about 5 years of running at the maximum luminosity achievable with the LHC, it can be foreseen that upgrades will be sought to increase the machine's luminosity, L, and energy, E, and thereby extend the physics reach. It is therefore proposed to make a staged upgrade of the LHC and its injectors, compatible with established accelerator design criteria and fundamental limitations of hardware. This is aimed initially at a target luminosity of up to 10 35 cm -2 s -1 in the