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.
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.
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).
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 .
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.
56124350
The status of the LHC Machine
116986881
Configuration of dipole wigglers for LEP
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.
115171795
Development of a superconducting insertion quadrupole model magnet for the Large Hadron Collider
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