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Beltran, R., Cepedello, R., & Hirsch, M. (2023). Tree-level UV completions for NRSMEFT d=6 and d=7 operators. J. High Energy Phys., 08(8), 31pp.
Abstract: We study ultra-violet completions for operators in standard model effective field theory extended with right-handed neutrinos (NRSMEFT). Using a diagrammatic method, we generate systematically lists of possible tree-level completions involving scalars, fermions or vectors for all operators at d = 6 and d = 7, which contain at least one right-handed neutrino. We compare our lists of possible UV models to the ones found for pure SMEFT. We also discuss how the observation of LNV processes via NRSMEFT operators at the LHC can be related to Majorana neutrino masses of the standard model neutrinos.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cantero, J., et al. (2023). Search for direct pair production of sleptons and charginos decaying to two leptons and neutralinos with mass splittings near the W-boson mass in root s=13 TeV pp collisions with the ATLAS detector. J. High Energy Phys., 06(6), 031–59pp.
Abstract: A search for the electroweak production of pairs of charged sleptons or charginos decaying into two-lepton final states with missing transverse momentum is presented. Two simplified models of R-parity-conserving supersymmetry are considered: direct pairproduction of sleptons ( (l) over tilde (l) over tilde), with each decaying into a charged lepton and a (x) over tilde (+/-)(0)(1) neutralino, and direct pair-production of the lightest charginos ( (x) over tilde (+/-)(1) (x) over tilde (-/+)(1)), with each decaying into a W-boson and a (x) over tilde (0)(1). The lightest neutralino ( (x) over tilde (0)(1)) is assumed to be the lightest supersymmetric particle (LSP). The analyses target the experimentally challenging mass regions where m( (l) over tilde)- m( (x) over tilde (0)(1)) and m( (x) over tilde (+/-)(1))- m((x) over tilde (0)(1)) are close to the W-boson mass ('moderately compressed' regions). The search uses 139 fb(-1) of root s = 13TeV proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider. No significant excesses over the expected background are observed. Exclusion limits on the simplified models under study are reported in the ((l) over tilde , (x) over tilde (0)(1)) and ( (x) over tilde (+/-) (1), (x) over tilde (0)(1)) mass planes at 95% confidence level (CL). Sleptons with masses up to 150 GeV are excluded at 95% CL for the case of a mass-splitting between sleptons and the LSP of 50 GeV. Chargino masses up to 140 GeV are excluded at 95% CL for the case of a mass-splitting between the chargino and the LSP down to about 100 GeV.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Amplitude analysis of the B0 (s)! K0K0 decays and measurement of the branching fraction of the B0! K0K0 decay. J. High Energy Phys., 07(7), 032–31pp.
Abstract: The B0 K0K0 and B0 s K0K0 decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3 fb. An untagged and timeintegrated amplitude analysis of B0 (s) (K+)(K) decays in two-body invariant mass regions of 150MeV/c2 around the K0 mass is performed. A stronger longitudinal polarisation fraction in the B0 K0K0 decay, fL = 0 : 724 0 : 051 (stat) 0 : 016 (syst), is observed as compared to fL = 0 : 240 0 : 031 (stat) 0 : 025 (syst) in the B0 s K0K0 decay. The ratio of branching fractions of the two decays is measured and used to determine B (B0 K0K0) = (8 : 0 0 : 9 (stat) 0 : 4 (syst)) x 10(-7).
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Cirigliano, V., Gisbert, H., Pich, A., & Rodriguez-Sanchez, A. (2020). Isospin-violating contributions to epsilon '/epsilon. J. High Energy Phys., 02(2), 032–44pp.
Abstract: The known isospin-breaking contributions to the K -> pi pi amplitudes are reanalyzed, taking into account our current understanding of the quark masses and the relevant non-perturbative inputs. We present a complete numerical reappraisal of the direct CP-violating ratio is an element of(')/is an element of, where these corrections play a quite significant role. We obtain the Standard Model prediction Re (is an element of(')/is an element of) = (14 +/- 5) <bold> </bold>10(-4), which is in very good agreement with the measured ratio. The uncertainty, which has been estimated conservatively, is dominated by our current ignorance about 1/N-C-suppressed contributions to some relevant chiral-perturbation-theory low-energy constants.
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Miralles, V., Miralles Lopez, M., Moreno Llacer, M., Peñuelas, A., Perello, M., & Vos, M. (2022). The top quark electro-weak couplings after LHC Run 2. J. High Energy Phys., 02(2), 032–24pp.
Abstract: Recent measurements at the Large Hadron Collider allow for a robust and precise characterisation of the electro-weak interactions of the top quark. We present the results of a global analysis at next-to-leading order precision including LHC, LEP/SLD and Tevatron data in the framework of the Standard Model Effective Field Theory. We include a careful analysis of the impact of correlations among measurements, as well as of the uncertainties in the Effective Field Theory setup itself. We find remarkably robust global fit results, with central values in good agreement with the Standard Model prediction, and 95% probability bounds on Wilson coefficients that range from +/- 0.35 to +/- 8 TeV-2. This result represents a considerable improvement over previous studies, thanks to the addition of differential cross-section measurements in associated production processes of top quarks and neutral gauge bosons.
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