Abstract
In this paper, we present a model in which an up-type vector-like quark (VLQ) is charged under a new $U(1)_d$ gauge force which kinetically mixes with the SM hypercharge. The gauge boson of the $U(1)_d$ is the dark photon, $\gamma_d$. Traditional searches for VLQs rely on decays into Standard Model electroweak bosons $W,Z$ or Higgs. However, since no evidence for VLQs has been found at the Large Hadron Collider (LHC), it is imperative to search for other novel signatures of VLQs beyond their traditional decays. As we will show, if the dark photon is much less massive than the Standard Model electroweak sector, $M_{\gamma_d}\ll M_Z$, for the large majority of the allowed parameter space the VLQ predominately decays into the dark photon and the dark Higgs that breaks the $U(1)_d$ . That is, this VLQ is a `maverick top partner' with nontraditional decays. One of the appeals of this scenario is that pair production of the VLQ at the LHC occurs through the strong force and the rate is determined by the gauge structure. Hence, the production of the dark photon at the LHC only depends on the strong force and is largely independent of the small kinetic mixing with hypercharge. This scenario provides a robust framework to search for a light dark sector via searches for heavy colored particles at the LHC.
Highlights
Some of the most important searches for beyond the Standard Model physics at the Large Hadron Collider (LHC) are searches for new vectorlike quarks (VLQs)
We present a model in which an up-type vectorlike quark (VLQ) is charged under a new Uð1Þd gauge force which kinetically mixes with the Standard Model hypercharge
One of the appeals of this scenario is that pair production of the VLQ at the LHC occurs through the strong force and the rate is determined by the gauge structure
Summary
Some of the most important searches for beyond the Standard Model physics at the Large Hadron Collider (LHC) are searches for new vectorlike quarks (VLQs). A renormalizable interaction [30,31,32] This kinetic mixing can be generated via new vectorlike fermions charged under both the SM and the new Uð1Þd [30,33,34], as considered here. Since there is a quadratic dependence on vEW and vd, this mass gap does not have to be very large for the decays T → t þ γd=hd to be dominant This is a new avenue to search for light dark sectors using decays of heavy particles at the LHC, providing a connection between heavy particle searches and searches for new light sectors. VI we present collider searches relevant for our model This includes the current collider sensitivity as well as demonstrating the complementarity between the searches for dark photons via heavy particle decays at the LHC and low energy experiments.
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