Detecting and studying the lightest pseudo-Goldstone boson at future pp, e(+)e(-) and mu(+)mu(-) colliders

For an attractive class of dynamical symmetry breaking (technicolor) models , the lightest neutral pseudo-Nambu-Goldstone boson (P-0) contains only dow n-type techniquarks and charged technileptons. We discuss the prospects for discovering acid studying the P-0 of such models at the Tevatron and the L HC and at future e(+)e(-) and mu(+)mu(-) colliders. Depending upon the numb er of technicolors, N-TC, discovery of the P-0 at the Tevatron and the LHC in the gg --> P-0 --> gamma gamma mode could be possible over a wide range of mass. For N-TC = 4, we estimate that RunII Tevatron data can be used to exclude or discover a P-0 in the 50-200 GeV mass range, and at the LHC, a v ery precise measurement of Gamma(P-0 --> gg)B(P-0 --> gamma gamma) will be possible. For N-TC = 4, discovery of the P-0 at an e(+)e(-) collider via th e reaction e(+)e(-) --> gamma P-0 should be possible for an integrated lumi nosity of L = 100 fb(-1) at root s = 500 CeV as long as m(p0) is not near m (z). However, measuring the branching fractions and couplings of the P-0 wi th precision would require much more luminosity. In the gamma gamma collide r mode of operation at an e(+)e(-) collider, the gamma gamma --> P-0 --> <b (b)over bar> signal should be very robust and could be measured with high s tatistical accuracy for a broad range of m(p0) if N-TC = 4. For the minimal N-TC = 1 case, detection of the P-0 at the Tevatron and in e(+)e(-) collis ions will be very difficult, and the precision of measurements at the LHC a nd the gamma gamma collider decline markedly. Only a mu(+) mu(-) collider y ields a P-0 production rate that does not depend markedly upon N-TC. At a m u(+) mu(-) collider, depending upon the luminosity available at low energie s, discovery of the P-0 as an s-channel resonance (given its predicted coup ling to mu(+) mu(-)) should prove possible via scanning, even if it has not already been detected elsewhere. Once the precise mass of the P-0 is known , operation of the mu(+) mu(-) collider as a P-0 factory will typically all ow precision measurements of enough observables to determine the number of technicolors of the theory and (up to a discrete set of ambiguities) the fu ndamental parameters of the low-energy effective Lagrangian describing the Yukawa couplings of the P-0. (C) 1999 Elsevier Science B.V. All rights rese rved.