Search for heavy toplike quarks using lepton plus jets events in 1.96 TeV pp collisions

Area of Science:

• Particle Physics
• High-Energy Physics
• Collider Physics

Background:

• The Standard Model of particle physics describes fundamental particles and forces.
• Searches for new heavy quarks, such as a hypothetical top-like quark (t'), are crucial for extending the Standard Model.
• Previous experiments have set limits on the masses of hypothetical new quarks.

Purpose of the Study:

• To search for evidence of pair production of a new heavy top-like quark (t').
• To investigate the decay channel t' -> W + quark.
• To set a lower limit on the mass of the t' quark.

Main Methods:

• Utilized data from the Collider Detector at Fermilab II (CDF II) detector.
• Analyzed a data sample of 760 pb^-1 from Run II of the Tevatron proton-antiproton collider.
• Performed a fit to the total transverse energy spectrum and reconstructed t' quark mass, considering Standard Model processes and t' pair production.

Main Results:

• Observed no statistically significant evidence for t' pair production.
• Set a lower limit on the mass of the t' quark at 256 GeV/c^2 at 95% confidence level (C.L.).
• Assumed standard strong couplings for the t' quark in the mass limit calculation.

Conclusions:

• The search for pair-produced t' quarks decaying to a W boson and another quark yielded no evidence for new physics beyond the Standard Model.
• The results place stringent constraints on the existence of such a heavy top-like quark.
• Future searches at higher energies and luminosities may probe different mass ranges or decay channels.