Characterization of new photomultipliers and fibers for the LUCID-3 prototypes for HL-LHC

LUCID-2, the main luminometer of the ATLAS experiment, guaranteed a precision of 1% and a time stability of about 1% during LHC Run-2. Similar performances are expected for Run-3 as well. Due to the higher pile-up and radiation damage, a new LUCID is needed to fulfill the requirements of Run-4. New photomultipliers (PMTs) and fibers have been installed in ATLAS as LUCID-3 prototypes and are evaluated for their use in Run-4. The first results of this characterization campaign are presented. The newly proposed PMTs generate shorter signals compared to LUCID-2 PMTs and the current readout system is not able to digitize them optimally. A fiber irradiation session was performed to estimate the radiation damage during Run-4. A larger loss was observed in the UV region with respect to the visible region, leading to a modification of the fiber prototype installed

The Importance of Slow-roll Corrections During Multi-field Inflation

We re-examine the importance of slow-roll corrections during the evolution of cosmological perturbations in models of multi-field inflation. We find that in many instances the presence of light degrees of freedom leads to situations in which next to leading order slow-roll corrections become significant. Examples where we expect such corrections to be crucial include models in which modes exit the Hubble radius while the inflationary trajectory undergoes an abrupt turn in field space, or during a phase transition. We illustrate this with two examples -- hybrid inflation and double quadratic inflation. Utilizing both analytic estimates and full numerical results, we find that corrections can be as large as 20%. Our results have implications for many existing models in the literature, as these corrections must be included to obtain accurate observational predictions -- particularly given the level of accuracy expected from CMB experiments such as PlanckComment: v1: 21 pages, 3 figures, 1 appendix. v2: clarifications to {\S}{\S}2.1, 3.1 and 4, {\S}5.3 added, references added, results unchanged. Matches published version in JCA