Signatures of top flavour-changing dark matter

We consider extending the Standard Model by including an additional Abelian gauge group broken at low energies under which the right-handed top quark is the only effectively charged Standard Model fermion. The associated gauge boson (Z ) is then naturally top-philic and couples only to the rest of the SM particle content at loop-level or via kinetic mixing with the hypercharge gauge boson which is assumed to be small. Working at the effective theory level, we demonstrate that such a minimal extension allows for an improved fitting of the ∼ 2σ excess observed in tth searches at the LHC in a region of parameter space that satisfies existing collider constraints. We also present the reach of the LHC at 13 TeV in constraining the relevant region of parameter space. Additionally we show that within the same framework a suitably chosen fermion charged only under the exotic Abelian group can, in the region of parameter space preferred by thetth measurements, simultaneously explain the dark matter relic density and the γ-ray excess at the galactic center observed by the Fermi-LAT experiment.

Section: Jhep06(2016)110mentioning

confidence: 99%

Novel collider and dark matter phenomenology of a top-philic Z ′

Cox

Medina

Ray

et al. 2016

“…Indeed, Eq. (18) shows that the rotations of Y to the lepton mass basis are highly suppressed, and as a result, do not induce large couplings in c, c , other than the single dominant one. Rotating to the mass, basis, the couplings read…”

Section: A Concrete Realizationmentioning

confidence: 94%

“…as well as the couplings of ϕ to leptons, c ij , c ij , and to the dark sector, g L ab , g R ab . We are interested in a flavorful dark sector [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] where both the mediator, ϕ, as well as the DM fields, χ 1,2 , carry nonzero flavor charges. Phenomenologically very interesting is the situation where flavor dynamics generates a single dominant off-diagonal coupling in the c ij , c ij matrices, while all the others are suppressed.…”

Section: A Preliminariesmentioning

confidence: 99%

Dark sectors and enhanced h → τ μ transitions

Galon

Zupan

2017

LHC searches with τ leptons in the final state are always inclusive in missingenergy sources. A signal in the flavor-violating Higgs decay search, h → τ µ, could therefore equally well be due to a flavor conserving decay, but with an extended decay topology with additional invisible particles. We demonstrate this with the three-body decay h → τ µϕ, where ϕ is a flavorful mediator decaying to a dark-sector. This scenario can give thermal relic dark matter that carries lepton flavor charges, a realistic structure of the charged lepton masses, and explain the anomalous magnetic moment of the muon, (g − 2)µ, while simultaneously obey all indirect constraints from flavor-changing neutral currents. Another potentially observable consequence is the broadening of the collinear mass distributions in the h → τ µ searches.

“…Table 2 shows diagrammatically the mono-b topology as well as the relevant direct searches considered in this work. In the case of mono-t searches the only simplified models producing sizable signals at tree level are divided in two categories depending on whether mono-t is resonantly produced, as in R-parity violating (RPV) SUSY, or non-resonantly produced via a t-channel top quark [59][60][61][62][63]. Strictly speaking, the RPV SUSY scenario does not have a dark matter candidate, as the lightest neutralino is not stable on cosmological time scales.…”

Section: Jhep06(2017)082mentioning

confidence: 99%

Mono-X versus direct searches: simplified models for dark matter at the LHC

Liew

Papucci

Vichi

et al. 2017

Abstract:We consider simplified models for dark matter (DM) at the LHC, focused on mono-Higgs, -Z or -b produced in the final state. Our primary purpose is to study the LHC reach of a relatively complete set of simplified models for these final states, while comparing the reach of the mono-X DM search against direct searches for the mediating particle. We find that direct searches for the mediating particle, whether in di-jets, jets+ / E T , multib+ / E T , or di-boson+ / E T , are usually stronger. We draw attention to the cases that the mono-X search is strongest, which include regions of parameter space in inelastic DM, two Higgs doublet, and squark mediated production models with a compressed spectrum.