Search

At the LHC, top quarks can be produced singly with a sizeable rate via electroweak interactions. This process probes a limited set of top-quark electroweak couplings, i.e. , the same entering the top-quark decay, yet at higher scales and with a different sensitivity. Requiring the production of a $Z$ or $H$ boson in association with single-top significantly extends the sensitivity of this process to new physics, opening up the unique possibility of testing top-Higgs, top-gauge, triple gauge, gauge-Higgs interactions without being dominated by QCD interactions. We consider $tZj$ and $tHj$ production at the LHC, providing predictions at next-to-leading accuracy in QCD in the framework of the standard model effective field theory, including all relevant operators up to dimension six. We perform the first complete study of the sensitivity to new interactions of these processes, highlighting the interplay and complementarity among $tj$, $tZj$ and $tHj$ in simultaneously constraining top-quark, triple gauge, and gauge-Higgs interactions in the current and future runs at the LHC., Comment: 29 pages, 6 figures

C. Degrande, J.-M. Gerard, C. Grojean, F. Maltoni and G. Servant Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, IL 61801, U.S.A. Centre for Cosmology, Particle Physics and Phenomenology (CP3), Chemin du Cyclotron 2, Universite catholique de Louvain, Belgium CERN Physics Department, Theory Division, CH-1211 Geneva 23, Switzerland Institut de Physique Theorique, CEA/Saclay, F-91191 Gif-sur-Yvette Cedex, France

In this work, we study indirect photon signatures of leptophilic dark matter (DM) coming from Centaurus A, where a DM density spike is believed to have survived to date contrary to the case of our galaxy. We consider a model where DM is a Majorana fermion which interacts with right-handed electrons via a scalar mediator. Assuming that the photons measured from the core of Cen A are coming from SM processes, we derive constraints on the average annihilation cross section which are 7 orders of magnitude stronger than the ones from measurements of the Galactic Center. Focusing on the allowed parameter space range, we calculate the flux of photons coming from the radiative DM-electron scattering in the AGN jets and the circular polarisation asymmetry of these photons. We find that this flux is two orders of magnitude lower than the background but its circular polarisation asymmetry can reach values close to $100\%$, indicating the need to experimentally exploit the high fraction of circular polarisation in order to detect these interactions. Since the origin of the photons in the GeV-TeV range from Cen A is not completely clear and an exotic origin is compatible with the measurements as well, we also consider the scenario in which synchrotron radiation can only partially explain the photon flux and we fit the excess with signals coming from DM annihilation, finding a best fit for a DM candidate with a mass $m_{\tilde{\chi}}= 123$ GeV and a coupling $a_R = 0.018$., Comment: 14 pages, 5 figures. Final version, published in PRD