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

This is the third out of five chapters of the final report [1] of theWorkshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted tothe study of the potential, in the search for Beyond the Standard Model (BSM)physics, of the High Luminosity (HL) phase of the LHC, defined as3 ab^-1 of data taken at a centre-of-mass energy of14 TeV, and of a possible future upgrade, the High Energy (HE) LHC,defined as 15 ab^-1 of data at a centre-of-mass energy of27 TeV. We consider a large variety of new physics models, both in asimplified model fashion and in a more model-dependent one. A long list ofcontributions from the theory and experimental (ATLAS, CMS, LHCb) communitieshave been collected and merged together to give a complete, wide, andconsistent view of future prospects for BSM physics at the consideredcolliders. On top of the usual standard candles, such as supersymmetricsimplified models and resonances, considered for the evaluation of futurecollider potentials, this report contains results on dark matter and darksectors, long lived particles, leptoquarks, sterile neutrinos, axion-likeparticles, heavy scalars, vector-like quarks, and more. Particular attention isplaced, especially in the study of the HL-LHC prospects, to the detectorupgrades, the assessment of the future systematic uncertainties, and newexperimental techniques. The general conclusion is that the HL-LHC, on top ofallowing to extend the present LHC mass and coupling reach by 20-50% on mostnew physics scenarios, will also be able to constrain, and potentiallydiscover, new physics that is presently unconstrained. Moreover, compared tothe HL-LHC, the reach in most observables will generally more than double atthe HE-LHC, which may represent a good candidate future facility for a finaltest of TeV-scale new physics.