236 research outputs found

    Renormalization Group Constraints on New Top Interactions from Electroweak Precision Data

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    Anomalous interactions involving the top quark contribute to some of the most difficult observables to directly access experimentally. They can give however a sizeable correction to very precisely measured observables at the loop level. Using a model-independent effective Lagrangian approach, we present the leading indirect constraints on dimension-six effective operators involving the top quark from electroweak precision data. They represent the most stringent constraints on these interactions, some of which may be directly testable in future colliders.Comment: 14 pages, 1 Table, 1 Figure. Minor changes, references added. Matches published versio

    Constraints on anomalous dimensions from the positivity of the S matrix

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    I am thankful to Guilherme Guedes, Mario Herrero-Valea, Maria Ramos, and Jose Santiago for useful discussions. This work is supported by SRA under Grants No. PID2019–106087GB-C21 and No. PID2021-128396NB-I00, by the Junta de Andalucía grants No. FQM 101, No. A-FQM-211-UGR18, No. P21-00199, and No. P18-FR-4314 (FEDER), as well as by the Spanish MINECO under the Ramón y Cajal programme MCIN/AEI /10.13039/501100011033 with Grant No. RYC2019-027155-I and by Grant CNS2022-136024 funded by MCIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR.We show that the analyticity and crossing symmetry of the S matrix, together with the optical theorem, impose restrictions on the renormalization group evolution of dimension-8 operators in the Standard Model effective field theory. Moreover, in the appropriate basis of operators, the latter manifest as zeros in the anomalous dimension matrix that, to the best of our knowledge, have not been anticipated anywhere else in the literature. Our results can be trivially extended to other effective field theories.European Union NextGenerationEU/PRTRSRA PID2019–106087GB-C21, PID2021-128396NB-I00FEDERMinisterio de Economía y Competitividad CNS2022-136024, MCIN/AEI/10.13039/501100011033, RYC2019-027155-I MINECOJunta de Andalucía A-FQM-211-UGR18, FQM 101, P18-FR-4314, P21-0019

    Positivity restrictions on the mixing of dimension-eight SMEFT operators

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    We discuss the structure of the mixing among dimension-eight operators in the SMEFT relying on the positivity of two-to-two forward scattering amplitudes. We uncover tens of new non-trivial zeros as well as hundreds of terms with definite sign in (a particular basis of) the corresponding anomalous dimension matrix. We highlight that our results are not immediately apparent from the Feynman diagrammatic perspective, nor from on-shell amplitude methods. As a byproduct of this work, we provide positivity bounds not previously derived in the literature, as well as explicit values of certain elements of the anomalous dimension matrix that serve for cross-check of our results.Comment: 11 pages + appendices, 4 figures, 4 table

    The Landscape of Composite Higgs Models

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    We classify all different composite Higgs models (CHMs) characterised by the coset space G/H\mathcal{G}/\cal{H} of compact semi-simple Lie groups G\mathcal{G} and H\mathcal{H} involving up to 13 Nambu-Goldstone bosons (NGBs), together with mild phenomenological constraints. As a byproduct of this work, we prove several simple yet, to the best of our knowledge, mostly unknown results: (1) Under certain conditions, a given set of massless scalars can be UV completed into a CHM in which they arise as NGBs; (2) The set of all CHMs with a fixed number of NGBs is finite, and in particular there are 642 of them with up to 13 massless scalars (factoring out models that differ by extra U(1)U(1)'s); (3) Any scalar representation of the Standard Model group can be realised within a CHM; (4) Certain symmetries of the scalar sector allowed from the IR perspective are never realised within CHMs. On top of this, we make a simple statistical analysis of the landscape of CHMs, determining the frequency of models with scalar singlets, doublets, triplets and other multiplets of the custodial group as well as their multiplicity. We also count the number of models with a symmetric coset.Comment: List of models in the ancillary file, 19 pages, 2 figures, 2 table

    Confronting SUSY models with LHC data via electroweakino production

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    We investigate multi-lepton signals produced by ElectroWeakino (EWino) decays in the MSSM and the TMSSM scenarios with sfermions, gluinos and non Standard Model Higgses at the TeV scale, being the Bino electroweak-scale dark matter. We recast the present LHC constraints on EWinos for these models and we find that wide MSSM and TMSSM parameter regions prove to be allowed. We forecast the number of events expected in the signal regions of the experimental multi-lepton analyses in the next LHC runs. The correlations among these numbers will help to determine whether future deviations in multi-lepton data are ascribable to the EWinos, as well as the supersymmetric model they originate from.Comment: 33 pages, 10 figures, 3 table
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