Future wishes and constraints from the experiments at the LHC for the Proton-Proton programme

TL;DR

This paper reviews the challenges and successes of the LHC's first run, discusses future high-luminosity operation plans, and emphasizes the importance of luminosity control for optimizing performance and experimental conditions.

Contribution

It provides a comprehensive assessment of LHC performance, explores future operational scenarios, and outlines strategies for luminosity control to enhance experimental outcomes.

Findings

LHC achieved high efficiency with beam brightness twice the design.

Luminosity control is crucial for future high-luminosity runs.

Effective luminosity levelling has improved experimental performance.

Abstract

Hosting six different experiments at four different interaction points and widely different requirements for the running conditions, the LHC machine has been faced with a long list of challenges in the first three years of luminosity production (2010-2012, Run 1), many of which were potentially capable of limiting the performance due to instabilities resulting from the extremely high bunch brightness. Nonetheless, LHC met the challenges and performed extremely well at high efficiency and routinely with beam brightness at twice the design, well over one-third of the time in collision for physics, average luminosity lifetimes in excess of 10 h and extremely good background conditions in the experiments. While the experimental running configurations remain largely the same for the future high luminosity proton-proton operational mode, the energy and the luminosity should increase significantly, making a prior assessment of related beam-beam effects extremely important to guarantee high performance. Of particular interest is the need for levelling the luminosity individually in the different experiments. Luminosity control as the more general version of 'levelling' has been at the heart of the success for LHCb, and to a large extent also for ALICE, throughout Run 1. With the increasing energy and potential luminosity, luminosity control may be required by all the experiments at some point in the future as a means of controlling the pileup conditions and trigger rates, but possibly also as a way of optimizing the integrated luminosity. This paper reviews the various motivations and possibilities for controlling the luminosity from the experiments' point of view, and outlines the future running conditions and desiderata for the experiments as they are viewed currently, with the aim of giving guidelines for different options.