Further searches of the Higgs scalar sector at the ESS

Abstract: Recent decades have witnessed remarkable confirmations of the Standard Model (SM) describing the Electro-Weak and Strong Interactions. The Higgs boson was observed at CERN-LHC at 7-8 TeV and 13 TeV. The HL-LHC, a major luminosity upgrade has been recently approved. The HL-LHC may be already an early "Higgs factory", however only capable to perform Ho related measurements with rather large uncertainties because of persisting backgrounds and uncertainties. New projects using leptons rather than hadrons should be investigated Ho has a spin zero and its coupling is proportional to the square of the lepton mass, greatly enhancing the production from pairs of muons. A mu+mu- Collider may operate at a much higher magnetic field respect to the e+e- Collider and it has a smaller radius, easily fitting within one existing European site. However muons are unstable particles: they must be produced in sufficient amounts from pions of a proton beam, cooled and quickly accelerated to the required energies. The scenario is here primarily concentrated to further developments of the European Spallation Source (ESS) under construction in the Lund site as the most intense future source of spallation neutrons. As a initial part of the program, muon cooling should be experimentally demonstrated with the much cheaper and simpler Initial Cooling Experiment.