Search for a neutral technicolor signature in pp(bar) collisions at center of mass energy = 1.8 TeV.

摘要

The standard model (SM) of particle physics has been a very successful theory for decades; however, several features remain unexplained. One such feature is the mechanism of electro-weak symmetry-breaking. The Higgs mechanism is postulated as part of the SM to give us the masses of the W +/- and the Z0 bosons in a manner consistent with unitarity. The Higgs boson is a consequence of the mechanism currently used. It is massive, and has the quantum numbers of the vacuum; i.e. it is a scalar. Also, the pattern of fermion (quark and lepton) masses is yet to be understood. Technicolor introduces a new force and particles (techniquarks and technileptons), which can break electroweak symmetry and generate the vector boson masses without introducing fundamental scalars. Along with some necessary extensions to the theory, technicolor provides the known fermion masses, and it also predicts many new "techni-mesons." 1 Previous searches for various technicolor channels have been performed throughout the high-energy physics community at CERN on the L3 and DELPHI Experiments, and at Fermilab on the CDF and DO Experiments. 2 At the DO experiment, we use neural networks to search for the lightest techni-mesons in a sample of gammabb¯ data at the Tevatron. They are the techni-o (oT) and its mass-degenerate techni- r ( rT ), which decay to a gamma and a techni-pion ( pT/p'T ). For the technicolor models considered, the pT/p'T decays predominantly to bb¯. This analysis searches for oT/ r0T production using many Monte Carlo signal samples on the M (oT) vs. M( pT ) mass plane. No evidence was found for the production of neutral technicolor particles in this channel, and 95% confidence level upper limits on cross-section x branching ratio (sigma x BR) are computed.;1E. Eichten, K. Lane and J. Womersley, "Finding Low-Scale Technicolor at the Tevatron," Phys. Lett. B405 305 (1997), hep-ph/9704455; E. Eichten, K. Lane, "Low-Scale Technicolor at the Tevatron," Phys. Lett. B388 803 (1996), hep-ph/9607213. 2K. Lane, "Technicolor Signatures---Ieri, Oggi E Domani," hep-ph/0006143 (July 2000). This reference has compiled several searches for technicolor and is also a good summary of technicolor phenomenology that is within observational range of current and near-future experiments.