Future Colliders

Abstract:

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 36.1 fb−1 at a centre-of-mass energy of 13 TeV collected in 2015 and 2016 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons (e or μ). Several signal regions are considered with increasing requirements on the missing transverse momentum above 250 GeV. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, and supersymmetric particles in several compressed scenarios.

Abstract:

Centrifugal barrel polishing (CBP) is a simple and environmentally friendly method that can be applied for mechanical abrasion of the cavity interior in order to remove the mechanically damaged surface after its production. The CBP recipes described in the literature, however, require CBP to be performed in many stages, require long processing times and nevertheless are unable to provide good cavity RF performance without additional chemical processing. Here, we report new results on characterization of cavity surfaces treated with a typical CBP recipe, including the contamination with abrasive particles, plastic deformation and hydrogen contamination, and critically evaluate it. Methods to reduce the depth of significant plastic deformation as well as the modified commercially viable CBP procedure followed by final electropolishing are proposed and tested on samples.