New High Luminosity LHC Baseline and Performance at Ultimate Energy

The LHC machine is envisioned to operate eventually at an ultimate beam energy of 7.5 TeV at the end of LHC Run 4, i.e. after commissioning of the HL-LHC systems, a stage falling into the High Luminosity LHC (HL-LHC) era. In this paper we review the latest baseline parameters and performance, and study the potential reach of the HL-LHC with pushed optics at the ultimate beam energy. Results in terms of integrated luminosity and effective pile-up density of both the nominal (5.0×10³⁴ cm⁻² s^{−1}) and ultimate (7.5×10³⁴ cm⁻² s^{−1}) levelling operations are discussed