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.
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.
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>>
121851945
Design, test and performance of the prototype superconducting quadrupole for the LEP low-beta insertions
The prototype of the superconducting quadrupoles for the low-beta insertions at the Large Electron-Positron collider has been tested successfully. This industry-built quadrupole, which has a warm bore of 130 mm and a magnetic length of 2 m, is required to provide a gradient of 36 T/m over a field aperture of 1000 mm diameter. It achieved its maximum operating current without training. While retaining the main characteristics of its ISR predecessors, the design of this magnet incorporates several novel features, due to constraints imposed by the environment of the LEP experiments. In particular the quadrupole is slender and ironless, and has a horizontally oriented cryogenic service funnel. Following a description of the major aspects of the design, the results are given of the magnetic and cryogenic tests and measurements. >
122817793
Conceptual design of a 5 T/mm quadrupole for linear collider final focus
The luminosity required of a future linear e/sup +/e/sup -/ collider in the teraelectronvolt energy range puts high demands on the final focus elements. In particular, if a classical quadrupole arrangement is chosen, the last magnet should be capable of producing a gradient of several tesla per millimeter. The authors have studied the performance limits of a quadrupole having soft ferromagnetic poles of sufficiently simple geometry to allow fabrication to submicron tolerances, excited by blocks of commercial permanent magnet material. It is shown that it should be possible to obtain a good quality quadrupole of less than 1-mm aperture, with up to 1.4-T pole-tip field.<<ETX>>
108199483
Analyzing magnet with field-free channel for use in the ISR
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.
121382436
Jet calculus beyond leading logarithms
It is shown that the evolution of hadronic jets produced in hard processes can be studied in terms of a simple parton branching picture, beyond the leading log approximation of QCD. The jet calculus is generalized to any given order of logs (but always to all orders of αs. We discuss the general structure of the formalism. Universality of jet evolution is discussed. We consider also jet calorimetry measure and the multiplicity distribution of final states in a form which allows a systematic improvement of approximation. To the next-to-leading order, we prove the finiteness and elucidate the scheme dependence of parton subprocess probabilities. The physical inclusive cross section is shown to be scheme independent: next-to-leading results for e+e− → q (non-singlet) + X agree with those of Curci and others.
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.
20156101
Threshold Effects Beyond the Standard Model
In this contribution to the Festschrift celebrating Gabriele Veneziano on his 65th birthday, I discuss the threshold effects of extra dimensions and their applications to physics beyond the standard model, focusing on superstring theory.
120182331
Macroscopic constraints on string unification
The comparison of sting theory with experiment requires a huge extrapolation from the microscopic distances, of order of the Planck length, up to the macroscopic laboratory distances. The quantum effects give rise to large corrections to the macroscopic predictions of sting unification. I discus the model-independent constraints on the gravitational sector of string theory due to the inevitable existence of universal Fradkin-Tseytlin dilatons. 9 refs.