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Maluf, R. V., & Olmo, G. J. (2023). Vacuum polarization and induced Maxwell and Kalb-Ramond effective action in very special relativity. Phys. Rev. D, 108(9), 095022–13pp.
Abstract: This work investigates the implications of very special relativity (VSR) on the calculation of vacuum polarization for fermions in the presence of Maxwell and Kalb-Ramond gauge fields in four-dimensional spacetime. We derive the SIM(2)-covariant gauge theory associated with an Abelian antisymmetric twotensor and its corresponding field strength. We demonstrate that the free VSR-Kalb-Ramond electrodynamics is equivalent to a massive scalar field with a single polarization. Furthermore, we determine an explicit expression for the effective action involving Maxwell and Kalb-Ramond fields due to fermionic vacuum polarization at one-loop order. The quantum corrections generate divergences free of nonlocal terms only in the VSR-Maxwell sector. At the same time, we observe UV/IR mixing divergences due to the entanglement of VSR-nonlocal effects with quantum higher-derivative terms for the Kalb-Ramond field. However, in the lower energy limit, the effective action can be renormalized like in the Lorentz invariant case.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Search for dark matter produced in association with a Higgs boson decaying to tau leptons at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 09(9), 189–53pp.
Abstract: A search for dark matter produced in association with a Higgs boson in final states with two hadronically decaying tau-leptons and missing transverse momentum is presented. The analysis uses 139 fb(-1) of proton-proton collision data at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. No evidence of physics beyond the Standard Model is found. The results are interpreted in terms of a 2HDM+a model featuring two scalar Higgs doublets and a pseudoscalar singlet field. Exclusion limits on the parameters of the model in selected benchmark scenarios are derived at 95% confidence level. Model-independent limits are also set on the visible cross-section for processes beyond the Standard Model producing missing transverse momentum in association with a Higgs boson decaying into tau-leptons.
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Clemente, G., Crippa, A., Jansen, K., Ramirez-Uribe, S., Renteria-Olivo, A. E., Rodrigo, G., et al. (2023). Variational quantum eigensolver for causal loop Feynman diagrams and directed acyclic graphs. Phys. Rev. D, 108(9), 096035–19pp.
Abstract: We present a variational quantum eigensolver (VQE) algorithm for the efficient bootstrapping of the causal representation of multiloop Feynman diagrams in the loop-tree duality or, equivalently, the selection of acyclic configurations in directed graphs. A loop Hamiltonian based on the adjacency matrix describing a multiloop topology, and whose different energy levels correspond to the number of cycles, is minimized by VQE to identify the causal or acyclic configurations. The algorithm has been adapted to select multiple degenerated minima and thus achieves higher detection rates. A performance comparison with a Grover's based algorithm is discussed in detail. The VQE approach requires, in general, fewer qubits and shorter circuits for its implementation, albeit with lesser success rates.
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Pich, A., Platschorre, A., & Reig, M. (2023). Electroweak mass difference of mesons. Phys. Rev. D, 108(9), 094044–6pp.
Abstract: We consider electroweak gauge boson corrections to the masses of pseudoscalar mesons to next to leading order in alpha s and 1/NC. The pion mass shift induced by the Z boson is shown to be m pi +/- – m pi 0 = -0.00201(12) MeV. While being small compared to the electromagnetic mass shift, the prediction lies about a factor of similar to 4 above the precision of the current experimental measurement and a factor O(10) below the precision of current lattice calculations. This motivates future implementations of these electroweak gauge boson effects on the lattice. Finally, we consider beyond standard model contributions to the pion mass difference.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2023). Search for a new pseudoscalar decaying into a pair of muons in events with a top-quark pair at √s=13 TeV with the ATLAS detector. Phys. Rev. D, 108(9), 092007–26pp.
Abstract: A search for a new pseudoscalar a-boson produced in events with a top-quark pair, where the a-boson decays into a pair of muons, is performed using root s=13 TeV pp collision data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 fb(-1). The search targets the final state where only one top quark decays to an electron or muon, resulting in a signature with three leptons e μμand μμmu. No significant excess of events above the Standard Model expectation is observed and upper limits are set on two signal models: pp -> tta and pp -> tt with t -> H(perpendicular to)b, H-perpendicular to -> W(perpendicular to)a, where a ->mu mu, in the mass ranges 15 GeV<m(a)<72 GeV and 120 GeV <= m(H +/-)<= 160 GeV.
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