Coherent e + e − pair creation at high energy muon colliders . ∗

It is shown that at muon colliders with the energy in the region of 100 TeV the process of coherent pair creation by the muon in the field of the opposing beam becomes important and imposes some limitations on collider parameters. One of the main advantages of muon colliders is that the muon is much heavier than the electron and therefore the radiation (beamstrahlung) in beam collisions is suppressed. The relative energy loss during the beam collision ∆E/E ∝ EB/m. However, there is another process in beam collisions which may be important for a high energy muon collider: it is the coherent e+e− creation. In this process the e+e− pair is created by a virtual photon in a strong field of the opposing muon beam B ≡ |E|+ |B|. The process of coherent pair creation is very important for e+e− linear colliders [1, 2]. This process has large probability at κ = (ω/mec 2)(B/B0) > 1, B0 = αe/r 2 e ∼ 4.4× 10 13 Gauss. (1) At a 100 TeV muon collider the energy and beam field are even higher than those at linear e+e− colliders. So, one can expect that this process will be important for muon collider as well, because naively the cross section of this process depends only on E,B,me, but not on mμ. However, there is one effect in this process which makes a situation at electrons and muon beams very different. In e+e− collisions, the maximum energy of virtual photons is almost equal to the electron energy, while at μμ colliders the maximum photon energy depends also on the mass of the produced system. This can be understood in the Talk at the Workshop Studies on Colliders and Collider Physics at the Highest Energies: Muon Colliders at 10 TeV to 100 TeV, 27 September 1 October, 1999 Montauk, New York, USA, be published by the American Institute of Physics. email:[email protected]