Abstract
Abstract Many new physics models with strongly interacting sectors predict a mass hierarchy between the lightest vector meson and the lightest pseudoscalar mesons. We examine the power of jet substructure tools to extend the 7 TeV LHC sensitivity to these new states for the case of QCD octet mesons, considering both two gluon and two b-jet decay modes for the pseudoscalar mesons. We develop both a simple dijet search using only the jet mass and a more sophisticated jet substructure analysis, both of which can discover the composite octets in a dijet-like signature. The reach depends on the mass hierarchy between the vector and pseudoscalar mesons. We find that for the pseudoscalar-to-vector meson mass ratio below approximately 0.2 a simple dijet analysis with only the jet mass variable provides the best discovery limit; for a ratio between 0.2 and the QCD-like value of 0.3, the full jet substructure analysis has the best discovery potential; for a ratio above approximately 0.3, the standard four-jet analysis is more suitable.
Highlights
JHEP07(2012)067 produced through its mixing with the gluon, while the G-pions πGa, as the lightest colored particles in the G sector, have the largest production cross sections
We develop both a simple dijet search using only the jet mass and a more sophisticated jet substructure analysis, both of which can discover the composite octets in a dijet-like signature
While the production cross sections for these light composite states are large, the dominant decays of the πGa and the ρaG yield all-hadronic final states, and large QCD backgrounds can make discovery challenging [5]. This is especially true of the vector resonance, ρaG, which naturally has large branching fractions to other new states, rather than back to dijets, leading to multijet final states which can be challenging to separate from QCD backgrounds
Summary
One generic possibility for physics above the electroweak scale is a new gauge interaction G which confines at a scale ΛG above the electroweak scale. It is the coupling of eq (2.3) to quarks which leads to resonant production of the ρG at hadron colliders.. The theory described by eq (2.1) depends on four parameters: the masses mρG and mπG, the ρaG − Ga mixing tan θ, and the ρaG − πGa coupling gρ. Assuming for simplicity that these interactions are proportional to the SM Yukawa couplings, cuij,d ∝ Yiuj,d, after electroweak symmetry breaking these operators allow G-pion to decay through i mq M πGa qta γ 5 q (2.10). Since G-pion decay to both bb and to gluons proceeds through higher dimension operators, details of the model can dramatically affect the branching ratios of the πGa. We will study discovery prospects for either πGa → gg or πGa → bb as the dominant decay channel. The decay widths of the ρaG into two quarks and into two G-pions are given in terms of tan θ as
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