AFBt meets LHC

Joanne L. Hewett, Jessie Shelton, Michael Spannowsky, Tim M.P. Tait, Michihisa Takeuchi

Research output: Contribution to journalArticlepeer-review


The recent Tevatron measurement of the forward-backward asymmetry of the top quark shows an intriguing discrepancy with Standard Model expectations, particularly at large tt̄ invariant masses. Measurements of this quantity are subtle at the LHC, due to its pp initial state, however, one can define a forward-central-charge asymmetry which captures the physics. We study the capability of the LHC to measure this asymmetry and find that within the SM a measurement at the 5σ level is possible with roughly 60fb-1 at √s=14TeV. If nature realizes a model which enhances the asymmetry (as is necessary to explain the Tevatron measurements), a significant difference from zero can be observed much earlier, perhaps even during early LHC running at √s=7TeV. We further explore the capabilities of the 7 TeV LHC to discover resonances or contact interactions which modify the tt̄ invariant mass distribution using recent boosted top-tagging techniques. We find that TeV-scale color-octet resonances can be discovered, even with small coupling strengths and that contact interactions can be probed at scales exceeding 6 TeV. Overall, the LHC has good potential to clarify the situation with regards to the Tevatron forward-backward measurement.

Original languageEnglish (US)
Article number054005
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number5
StatePublished - Sep 7 2011
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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