Yangians, Grassmannians and T-duality

We investigate the Yangian symmetry of scattering amplitudes in N=4 super Yang-Mills theory and show that its formulations in twistor and momentum twistor space can be interchanged. In particular we show that the full symmetry can be thought of as the Yangian of the dual superconformal algebra, annihilating the amplitude with the MHV part factored out. The equivalence of this picture with the one where the ordinary superconformal symmetry is thought of as fundamental is an algebraic expression of T-duality. Motivated by this, we analyse some recently proposed formulas, which reproduce different contributions to amplitudes through a Grassmannian integral. We prove their Yangian invariance by directly applying the generators.Comment: 28 pages, 1 figure; v2: minor correction

Experiment protection at the LHC and damage limits in LHC(b) silicon detectors

The Large Hadron Collider (LHC), once in operation, will represent approximately a 200-fold increase in stored beam energy with respect to previous high energy colliders. Safe operation will critically rely on machine and experiment protection systems. A review is given of possible beam failure modes at the LHC and of the strategy adopted in the LHC experiments to protect the detectors against such events. Damage limits for the detectors are discussed