Searching for dark photons with maverick top partners

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, γ 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 γ d 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.Some of the most important searches for Beyond the Standard Model (BSM) physics at the Large Hadron Collider (LHC) are searches for new vector like quarks (VLQs). Up-type VLQs, so-called top partners T , are ubiquitous in composite [1][2][3][4][5][6][7] and Little Higgs [8][9][10][11][12][13][14][15] models where new fermionic top partners help solve the hierarchy problem. Traditionally, searches for VLQs rely on decays into the Standard Model (SM) electroweak (EW) bosons: W/Z/Higgs. However, there is a a class of "maverick top partners" with non-traditional decays into photons [16][17][18][19][20][21], gluons [16][17][18][19][20][21], new scalars [22][23][24][25], etc. These new decays can easily be dominant with minor tweaks to the simplest VLQ models. We consider a VLQ that is charged under both the SM and a new abelian gauge symmetry U (1) d , where the SM is neutral under the U (1) d . As we will show, for a very large range of parameter space, this opens new dominant decays of VLQs that have not yet been searched for.This new U (1) d can be motivated by noting that dark matter may very well have selfinteractions through this new force. The U (1) d gauge boson, the so-called dark photon, kinetically mixes with the SM hypercharge through a renormalizable interaction [26][27][28]. This kinetic mixing can be generated via new vector like fermions charged under both the SM and the new U (1) d [26,29,30], as considered here. In the limit that the dark photon is much less massive than the Z and the kinetic mixing is small, the dark photon inherits couplings to SM particles of the form ε J µ EM , where J µ EM is the electromagnetic current and ε is the kinetic mixing parameter. Hence, the name dark photon. Most of the searches for the dark photon...

Composite dark matter phenomenology in the presence of lighter degrees of freedom

“…Besides, only limits in a narrow range 100 GeV m κ 400 GeV have been obtained using LHC results for κ → bb [63]; see refs. [64][65][66][67][68][69][70][71][72][73] for studies of other exotic decays of VLQs. Thus, we will provide dedicated searches for this case.…”

Kinetic mixing, dark photons and extra dimensions. Part III. Brane localized dark matter

“…In the simplest of such models, a force carrier (the dark photon, a gauge field corresponding to a new gauge group, U(1) D under which SM fields are neutral) mediates the relevant DM-SM interaction. This very weak interaction is the result of the small KM between this U(1) D and the SM hypercharge group, U(1) Y , which is generated at the one-(or two)-loop level by a set of BSM fields, called portal matter (PM) [16][17][18][19][20][21][22][23][24][25][26][27], JHEP03(2021)173 which carry charges under both gauge groups. In the IR, the phenomenology of such models is well-described by suitably chosen combinations of only a few parameters: the DM and dark photon masses, m DM,V , respectively, the U(1) D gauge coupling, g D and , the small dimensionless parameter describing the strength of the KM, ∼ 10 − (3−4) .…”

Signatures of vector-like top partners decaying into new neutral scalar or pseudoscalar bosons

“…It is thus important to ask how the presence of exotic decay channels of VLQs can affect the current bounds and whether these might actually be promising discovery channels on their own. This question has been asked in similar contexts in various preceding works [14][15][16][17][18][19][20][21][22][23], each concentrating on a specific BSM construction. Here, in contrast, we follow the approach of [24], which adopts a set of simplified scenarios based on effective Lagrangians (motivated by compositeness).…”