Anapole dark matter via vector boson fusion processes at the LHC

Abstract

Dark matter that is electrically neutral but couples to the electromagnetic current through higherdimensional operators constitutes an interesting class of models. We investigate this class of models at the Large Hadron Collider, focusing on the anapole moment operator in an effective field theory (EFT) framework, and utilizing the vector boson fusion (VBF) topology. Assuming proton-proton collisions at √ s = 13 TeV, we present the VBF anapole dark matter (ADM) cross sections and kinematic distributions as functions of the free parameters of the EFT, the cutoff scale Λ and the ADM mass mχ. We find that the distinctive VBF topology of two forward jets and large dijet pseudorapidity gap is effective at reducing SM backgrounds, leading to a 5σ discovery reach for all kinematically allowed ADM masses with Λ ≤ 1.65 (1.15) TeV, assuming an integrated luminosity of 3000 (100) fb −1 .

Light and darkness: consistently coupling dark matter to photons via effective operators

“…Firstly, for dark matter masses above m W , the W + W − annihilation channel plays an important role in fixing the thermal relic abundance. Secondly, a recent phenomenological study [37] has found the VBF process to be a sensitive probe of 'anapole' dark matter, which corresponds to the photon version of the C A operator in Eq. (2).…”

“…Furthermore, the dark matter mass itself is a free parameter and determines the relevant scale for thermal freeze-out and indirect detection constraints. Electromagnetic form factors for dark matter have been considered in direct and indirect detection as well as at colliders over several decades of dark matter mass, extending into the TeV range [8][9][10][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. However, it is clear that the hypercharge form factors should be the appropriate EFT here, given that relevant energies can far exceed the electroweak scale.…”

“…In recent literature, a discrepancy has emerged in the treatment of the electromagnetic form factors beyond their validity, centered on the relevance of the χχ → W + W − channel. On one hand, this channel has been exploited to yield impressive collider limits [37] in the vector boson fusion (VBF) channel. On the other hand, the weak boson channel has been assumed to be irrelevant for direct and indirect detection and subsequently ignored (see e.g.…”

“…This means that the collider limits in Ref. [37] result from the application of an EFT beyond its validity. • When including the hypercharge form factors, the W + W − channel is tamed at high energies by Z -mediated diagrams, this results in a total annihilation cross-section similar to Ref.…”

Search for long-lived heavy neutrinos at the LHC with a VBF trigger

“…The VBF topology is particularly useful to search for new physics, see for instance [67][68][69][70][71][72][73][74][75]. It involves two high p T jets in the forward direction, located in opposite hemispheres of the detector.…”