Standard Model Physics at the HL-LHC and HE-LHC

Abstract

The successful operation of the Large Hadron Collider (LHC) and the excellent performance of the ATLAS, CMS, LHCb and ALICE detectors in Run-1 and Run-2 with pp collisions at center-of-mass energies of 7, 8 and 13 TeV as well as the giant leap in precision calculations and modeling of fundamental interactions at hadron colliders have allowed an extraordinary breadth of physics studies including precision measurements of a variety physics processes. The LHC results have so far confirmed the validity of the Standard Model of particle physics up to unprecedented energy scales and with great precision in the sectors of strong and electroweak interactions as well as flavour physics, for instance in top quark physics. The upgrade of the LHC to a High Luminosity phase (HL-LHC) at 14 TeV center-of-mass energy with 3 ab −1 of integrated luminosity will probe the Standard Model with even greater precision and will extend the sensitivity to possible anomalies in the Standard Model, thanks to a ten-fold larger data set, upgraded detectors and expected improvements in the theoretical understanding. This document summarises the physics reach of the HL-LHC in the realm of strong and electroweak interactions and top quark physics, and provides a glimpse of the potential of a possible further upgrade of the LHC to a 27 TeV pp collider, the High-Energy LHC (HE-LHC), assumed to accumulate an integrated luminosity of 15 ab −1 .

Search for Standard Model Production of Four Top Quarks

“…This cross section measurement is found to be consistent with the Standard Model prediction. However, the additional data and increased center-of-mass energy promised by the HL-LHC makes for an exiting future of precision measurements of tttt and other rare Standard Model processes [9].…”

Probing tqZ anomalous couplings in the trilepton signal at the HL-LHC, HE-LHC and FCC-hh

“…For the SM backgrounds, we generated LO samples renormalised the NLO or next-NLO (NNLO) order cross sections, where available, taken from Refs. [39][40][41][42][43][44][45][46][47][48]. For instance, the LO cross section for the W ± Z+ jets background (one the one most relevant overall) is renormalised to the NLO one through a k-factor of 1.3 [43] at 14 TeV LHC and, as an estimate, we assume the same correction factor at the HE-LHC and FCC-hh.…”

“…For instance, the LO cross section for the W ± Z+ jets background (one the one most relevant overall) is renormalised to the NLO one through a k-factor of 1.3 [43] at 14 TeV LHC and, as an estimate, we assume the same correction factor at the HE-LHC and FCC-hh. The LO cross section for the t t process is renormalised to the NNLO one by a k-factor of 1.6 [48] at the HL-LHC as well as HE-LHC and 1.43 [42] at the FCC-hh.…”

Search for new phenomena in top quark interactions

“…The summary of the latest constraints obtained with the LHC data on the top quark FCNC branching ratios, along with the theoretical predictions [6] and projections of sensitivity of experimental searches for future experiments [13][14][15], is presented in Fig. 2.…”