Detecting and studying the lightest pseudo-Goldstone boson at future pp, e+e− and μ+μ− colliders

For an attractive class of dynamical symmetry breaking (technicolor) models, the lightest neutral pseudo-Nambu-Goldstone boson (P0) contains only down-type techniquarks and charged technileptons. We discuss the prospects for discovering and studying the P0 of such models at the Tevatron and the LHC and at future e+e− and μ+μ− colliders. Depending upon the number of technicolors, NTC, discovery of the P0 at the Tevatron and the LHC in the gg → P0 → γγ mode could be possible over a wide range of mass. For NTC = 4, we estimate that RunII Tevatron data can be used to exclude or discover a P0 in the 50–200 GeV mass range, and at the LHC, a very precise measurement of Γ(P0 → gg)B(P0 → γγ) will be possible. For NTC = 4, discovery of the P0 at an e+e− collider via the reaction e+e− → γP0 should be possible for an integrated luminosity of L = 100 fb−1 at √s = 500 Gev as long as mP0 is not near mZ. However, measuring the branching fractions and couplings of the P0 with precision would require much more luminosity. In the γγ collider mode of operation at an e+e− collider, the γγ → P0 → bb signal should be very robust and could be measured with high statistical accuracy for a broad range of mP0 if NTC = 4. For the minimal NTC = 1 case, detection of the P0 at the Tevatron and in e+e− collisions will be very difficult, and the precision of measurements at the LHC and the γγ collider decline markedly. Only a μ+μ− collider yields a P0 production rate that does not depend markedly upon NTC. At a μ+μ− collider, depending upon the luminosity available at low energies, discovery of the P0 as an s-channel resonance (given its predicted coupling to μ+μ−) should prove possible via scanning, even if it has not already been detected elsewhere. Once the precise mass of the P0 is known, operation of the μ+μ− collider as a P0 factory will typically allow precision measurements of enough observables to determine the number of technicolors of the theory and (up to a discrete set of ambiguities) the fundamental parameters of the low-energy effective Lagrangian describing the Yukawa couplings of the P0.