Search for top-quark partners with charge 5/3 in the same-sign dilepton final state

Area of Science:

• High Energy Physics
• Particle Physics
• Beyond Standard Model Physics

Background:

• The Standard Model of particle physics describes fundamental particles and forces.
• Extensions to the Standard Model predict new particles, such as heavy partners of the top quark.
• Searches for these predicted particles can reveal new physics phenomena.

Purpose of the Study:

• To search for evidence of heavy top quark partners with charge 5/3.
• To establish exclusion limits on the mass of these hypothetical particles.

Main Methods:

• Analysis of proton-proton collision data collected by the CMS experiment at the LHC.
• Utilizing a data sample corresponding to an integrated luminosity of 19.5 fb⁻¹ at √s = 8 TeV.
• Selection of events containing a pair of same-sign leptons to identify potential signals.

Main Results:

• No significant excess of events was observed above the expected background.
• The existence of top-quark partners with masses below 800 GeV is excluded at a 95% confidence level.
• The exclusion assumes these hypothetical particles decay exclusively to a top quark and a W boson (tW).

Conclusions:

• This study presents the first exclusion limits from the LHC on top quark partners with charge 5/3.
• The established limits are significantly more restrictive than previous findings.
• The results constrain theories beyond the Standard Model that predict such heavy particles.