2942508
Supersymmetry Relations and MHV Amplitudes in Superstring Theory
Abstract We discuss supersymmetric Ward identities relating various scattering amplitudes in type I open superstring theory. We show that at the disk level, the form of such relations remains exactly the same, to all orders in α ′ , as in the low-energy effective field theory describing the α ′ → 0 limit. This result holds in D = 4 for all compactifications, even for those that break supersymmetry. We apply SUSY relations to the computations of N -gluon MHV superstring amplitudes, simplifying the existing results for N ⩽ 6 and deriving a compact expression for N = 7 .
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.
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.
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.
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.
119276770
Maximally Helicity Violating Disk Amplitudes, Twistors and Transcendental Integrals
Abstract We obtain simple expressions for tree-level maximally helicity violating amplitudes of N gauge bosons from disk world-sheets of open superstrings. The amplitudes are written in terms of ( N − 3 ) ! hypergeometric integrals depending on kinematic parameters, weighted by certain kinematic factors. The integrals are transcendental in a strict sense defined in this work. The respective kinematic factors can be succinctly written in terms of “dual” momentum-twistors. The amplitudes are computed by using the prescription proposed by Berkovits and Maldacena.
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.
73548193
Systems layout of the low-/spl beta/ insertions for the LHC experiments
The LHC experimental insertions consist of a low-/spl beta/ triplet, a pair of separation dipoles, and a matching section of four quadrupoles. The superconducting low-/spl beta/ quadrupoles must accommodate separated beams at injection, provide high field gradients and low multipole errors for colliding beams, and sustain considerable heat load from secondary particles generated in the high luminosity ATLAS and CMS experiments. In the other two proposed experiments, ALICE and LHC-B, the separation dipoles and matching sections share the available space with the injection equipment. In this report we present the systems layout of the experimental insertions for the LHC, and review the requirements for the superconducting magnets.
54553106
Quench performance and field quality measurements of the first LHC low-/spl beta/ quadrupole model
As part of the LHC magnet development program, CERN in collaboration with Oxford Instruments has designed, built and tested a one metre model of a 70 mm aperture low-/spl beta/ quadrupole. The magnet features a four layer coil, and is designed for 250 T/m at 1.9 K. We review the results of the magnet training and quench propagation studies performed at 4.3 K and 1.9 K, and report on the magnetic field measurements.
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.
115978348
Tau-charm factory cost estimate