LHC signals from cascade decays of warped vector resonances

Abstract

Recently (arXiv:1608.00526), a new framework for warped higher-dimensional compactifications with "bulk" standard model (SM) was proposed: in addition to the UV (Planck scale) and IR (a couple of TeV) branes, there is an intermediate brane, taken to be around 10 TeV. The SM matter and Higgs fields propagate from the UV brane down to this intermediate brane only, while gauge and gravity fields propagate in the entire bulk. Such a configuration renders the lightest gauge Kaluza-Klein (KK) states within LHC reach, simultaneously satisfying flavor and CP constraints. In addition, the usual leading decay modes of the lightest KK gauge bosons into top and Higgs bosons are suppressed. This effect permits erstwhile subdominant channels to become significant. These include flavor-universal decays to SM fermions and Higgs bosons, and a novel channel -decay to a radion and a SM gauge boson, followed by radion decay to a pair of SM gauge bosons. In this work, we first delineate the parameter space where the above mentioned cascade decay of gauge KK particles dominates, and thereby can be the discovery mode at the LHC. We then perform a detailed analysis of the LHC signals from this model, finding that 300/fb suffices for evidence of KK-gluon in tri-jet, jet + di-photon and jet + di-boson channels. However, KK photon in photon + di-jet, and KK-W in leptonic W + di-jet require 3000/fb. The crucial feature of this decay chain is a "double" resonance, i.e. 3-particle and 2-particle invariant mass peaks, corresponding to the KK gauge boson and the radion respectively.

Running bumps from stealth bosons

“…The cross section times efficiency of the injected signals is given in Table 1. We note in passing that, as previously seen for the τ 21 and D 2 variables [3,25], the efficiency for stealth bosons of a cut on two-subjettiness, as measured by N 1 2 , is smaller than for the QCD background. The jet mass distributions at the different stages of the N 1 2 selection are presented for the three scenarios in the top, left panels of Figs.…”

“…The decay S → Z Z → qqqq is analogous. Those signals can also appear in left-right models if the neutral scalar sector departs from the alignment limit, and in models with warped extra dimensions, with S = φ the radion [21,22]. The third scenario is S → A 1 A 2 → bbbb, with M S = 200 GeV and two different (pseudo-)scalars A 1 , A 2 , with M A 1 = 20 GeV, M A 2 = 115 GeV.…”

“…For jet substructure variables such as τ 21 [4,5] and D 2 [6], designed to separate hadronically-decaying weak bosons from the QCD background, stealth bosons look more like the QCD background, composed by quark and gluon jets.…”

“…Let us consider the decay S → A A → qqqq of a boosted stealth boson. When the groomed jet mass m J is close to M S , the jet substructure is mostly four-pronged, so that a tight requirement of a small τ 21 or D 2 of the groomed jet, to select a twopronged substructure, usually results in a rejection. But often the grooming algorithm fully eliminates one of the daughter particles A from the jet, yielding a jet mass m J ∼ M A .…”

“…But often the grooming algorithm fully eliminates one of the daughter particles A from the jet, yielding a jet mass m J ∼ M A . This groomed jet has a mostly two-pronged substructure, so the application of a requirement on τ 21 or D 2 has a much larger efficiency. As a consequence, the bulk of the jet mass bump moves from M S to M A after the application of the jet substructure requirement, with the removal of the events with jet mass closer to M S .…”