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.
42302696
Multigluon scattering in open superstring theory
We discuss the amplitudes describing $N$-gluon scattering in type I superstring theory, on a disk world sheet. After reviewing the general structure of amplitudes and the complications created by the presence of a large number of vertices at the boundary, we focus on the most promising case of maximally helicity violating (MHV) configurations because in this case, the zero Regge slope limit (${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{\rightarrow}0$) is particularly simple. We obtain the full-fledged MHV disk amplitudes for $N=4$, 5, and $N=6$ gluons, expressed in terms of one, two and six functions of kinematic invariants, respectively. These functions represent certain boundary integrals\char22{}generalized Euler integrals\char22{}which for $N\ensuremath{\ge}6$ correspond to multiple hypergeometric series (generalized Kamp\'e de F\'eriet functions). Their ${\ensuremath{\alpha}}^{\ensuremath{'}}$ expansions lead to Euler-Zagier sums. For arbitrary $N$, we show that the leading string corrections to the Yang-Mills amplitude, of order $\mathcal{O}({\ensuremath{\alpha}}^{\ensuremath{'}2})$, originate from the well-known ${\ensuremath{\alpha}}^{\ensuremath{'}2}\text{ }\mathrm{Tr}{F}^{4}$ effective interactions of four gauge field strength tensors. By using iteration based on the soft gluon limit, we derive a simple formula valid to that order for arbitrary $N$. We argue that such a procedure can be extended to all orders in ${\ensuremath{\alpha}}^{\ensuremath{'}}$. If nature gracefully picked a sufficiently low string mass scale, our results would be important for studying string effects in multijet production at the Large Hadron Collider (LHC).
15978893
String loop corrections to gauge and Yukawa couplings
We report on the recent progress in computing the effective supergravity action from superstring scattering amplitudes beyond the tree approximation. We discuss the moduli-dependent string loop corrections to gauge, gravitational and Yukawa couplings.
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.
122672513
Dilaton, gaugino condensation and supersymmetry breaking
Abstract Non-perturbative condensation of gauginos belonging to a gauge group of the form G 1 ⊗ G 2 ⊗…⊗ G p , whre G n are non-abelian subgroups, is examined in superstring theory by utilizing the effective lagrangian techniques. A supersymmetric vacuum with stable expectation values of the dilation and moduli fields is shown to exist provided that the gauge group satisfies one non-trivial constraint.
119067706
Higher Level String Resonances in Four Dimensions
Abstract We study higher level Regge resonances of open superstrings, focusing on the universal part of the Neveu–Schwarz sector common to all D-brane realizations of the standard model. For Regge states with masses far above the fundamental string scale, we discuss the spin-dependence of their decay rates into massless gauge bosons. Extending our previous work on lowest level string excitations, we study the second mass level at which spins range from 0 to 3. We construct the respective vertex operators and compute the amplitudes involving one massive particle and two or three gauge bosons. To illustrate the use of Britto–Cachazo–Feng–Witten (BCFW) recursion relations in superstring theory, we build the four-gluon amplitude from on-shell amplitudes involving string resonances and gauge bosons.
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.
118159983
The LHC:: a new hadron collider for experimental physics
Abstract The Large Hadron Collider is now under construction at CERN. This accelerator will be by far the most powerful ever built, and will provide the current generation of experimental physicists with an extraordinary opportunity to make new discoveries. It will also provide accelerator scientists with a tool to test current theory and refine studies of possible future accelerators going to even higher energies. The environment of a collider is such that experts of both disciplines have to collaborate closely, and this will surely continue to be to the long-term advantage of our whole field of science.
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.
38380389
Design of the 70 mm twin aperture superconducting quadrupole for the LHC dump insertion
The LHC dump insertion features a pair of superconducting quadrupoles located on either side of a 340 m long straight section. Two horizontally deflecting kickers, located in between the quadrupole pairs, and a septum in the centre of the insertion, vertically deflect the two counter-rotating beams past the quadrupoles on the downstream sides, and into the dump areas. Due to the layout, the optical /spl beta/ function in the quadrupoles is around 640 m, the largest around the LHC at injection. The quadrupoles must therefore have enlarged aperture and specially designed cryostats to allow for the safe passage of both the circulating and ejected beams. In this paper we present the design of the twin aperture dump quadrupole based on the 70 mm four layer coil proposed for the LHC low-/spl beta/ quadrupoles. In preparation for model construction, we report on improvements of the coil design and a study of the retaining structures.
39425282
The magnets for the LHC experiments
The Large Hadron Collider (LHC) presently under construction at the European Laboratory for Particle Physics (CERN) will provide proton-proton collisions at the 14 TeV level. Each of the four approved detectors (ALICE, ATLAS, CMS, and LHCb) to be installed at the interaction points of this machine relies on a sophisticated magnet system for separation and momentum measurements of the charged particles. The magnets are being designed, manufactured, tested and installed under the technical and financial responsibility of the experiment collaborations, but must satisfy constraints imposed by the laboratory, regarding in particular the cryogenics, powering, controls, and safety. The delivery and assembly schedules are also highly constrained by the requirement to have the magnet systems fully installed before the projected commissioning of the accelerator in 2005. The report compares the salient features of these magnet systems, and of their integration into the CERN environment.