HFiTT - Higgs Factory in Tevatron Tunnel (Rev. 3)

Introduction Among various options for a Higgs factory [1], a photon collider has the distinct advantage of the lowest energy requirement for an electron beam. This advantage is especially important for a circular Higgs factory, in which the synchrotron radiation power increases to the fourth power of the electron energy. For an e + e  collider, the minimum required energy per beam is 120 GeV, while for a photon collider it is 80 GeV. The corresponding ratio of synchrotron radiation power is 5 to 1. This makes it possible to consider building a photon collider at Fermilab, which will be named HFiTT, or Higgs Factory in Tevatron Tunnel. The layout is shown in Figure 1. A photon collider is based on Inverse Compton Scattering (ICS) by shooting a low energy (~3.5 eV) laser beam into a high energy (10s of GeV) electron beam to generate a back-scattered high energy (10s of GeV) photon beam for collision. The cross section for  → H is large and comparable to e + e  → ZH (~200 fb). Since this is an s-channel resonance, the required photon energy is low (63 GeV), corresponding to 80 GeV for an electron beam. Our design goal is 10,000 Higgs per year. If we look to the far future of electron collider technology, very high gradient acceleration techniques such as plasma wakefield acceleration are asymmetric between electrons and positrons. It is therefore important to develop a technology that will allow physicists to accelerate electrons only and still access annihilation reactions with precisely understood point-like interactions. The photon collider fills this need. This project will not only carry out important measurements of the Higgs boson properties but will also demonstrate the unique technologies needed to construct photon collider experiments at higher energies.