1,721,003 research outputs found
Higgs physics beyond the SM: The non-linear EFT approach
Full text linkDepending on whether electroweak physics beyond the Standard
Model is based on a linear or on a non-linear implementation of the electroweak symmetry breaking, a linear or a chiral Effective Lagrangian is more appropriate.
In this talk, the main low-energy signals that allow to recognize whether the observed Higgs scalar is a dynamical (composite) particle or rather an elementary one are presented, in a model-independent way. The patterns of effective couplings produced upon the assumption of specific composite Higgs models are also discussed
SMEFTsim
No full textThe SMEFTsim package contains a set of models written in FeynRules and pre-exported to the UFO format, that allow automated calculations in the Standard Model Effective Field Theory (SMEFT).
The FeynRules source files can be loaded in Mathematica and used for analytic operations on the SMEFT Lagrangian and for the extraction of the Feynman rules. The UFO models can be imported in Monte Carlo generators, for the simulation of LHC events
Les Houches 2015: Physics at TeV colliders - new physics working group report
No full textWe present the activities of the 'New Physics' working group for the 'Physics at TeV Colliders' workshop (Les Houches, France, 1-19 June, 2015). Our report includes new physics studies connected with the Higgs boson and its properties, direct search strategies, reinterpretation of the LHC results in the building of viable models and new computational tool developments. Important signatures for searches for natural new physics at the LHC and new assessments of the interplay between direct dark matter searches and the LHC are also considered
Beyond the Standard Model in Vector Boson Scattering Signatures
No full textThe high-energy scattering of massive electroweak bosons, known as vector boson scattering (VBS), is a sensitive probe of new physics. VBS signatures will be thoroughly and systematically investigated at the LHC with the large data samples available and those that will be collected in the near future. Searches for deviations from Standard Model (SM) expectations in VBS facilitate tests of the Electroweak Symmetry Breaking (EWSB) mechanism. Current state-of-the-art tools and theory developments, together with the latest experimental results, and the studies foreseen for the near future are summarized. A review of the existing Beyond the SM (BSM) models that could be tested with such studies as well as data analysis strategies to understand the interplay between models and the effective field theory paradigm for interpreting experimental results are discussed. This document is a summary of the EU COST network "VBScan" workshop on the sensitivity of VBS processes for BSM frameworks that took place December 4-5, 2019 at the LIP facilities in Lisbon, Portugal. In this manuscript we outline the scope of the workshop, summarize the different contributions from theory and experiment, and discuss the relevant findings
Scheming in the SMEFT
Full text linkWe discuss the constraints on the Standard Model Effective Field Theory inferred from global fits to electroweak data. Special attention is paid to two unconstrained combinations of Wilson coefficients that are present when the analysis is restricted to measurements of ψψ ̄ → ψψ ̄ scatterings. We illustrate how these unconstrained directions arise due to a reparameterization invariance that characterizes ψψ ̄ → ψψ ̄ processes but is not respected in ψψ ̄ → ψψ ̄ ψψ ̄ scatterings. This invariance is independent of the operator basis adopted and of the choice of the input parameters. This is verified comparing the results obtained in the {αem,m Z,ĜF} input scheme with those of a {mW,m Z,ĜF} scheme
Probing the Charm Quark Yukawa Coupling in Higgs+Charm Production
No full textWe propose a new method for determining the coupling of the Higgs boson to charm quarks, via Higgs production in association with a charm-tagged jet: pp→hc. As a first estimate, we find that at the LHC with 3000 fb-1, it should be possible to derive a constraint of order one, relative to the standard model (SM) value of the charm Yukawa coupling. As a by-product of this analysis, we present an estimate of the exclusive pp→HD(∗) electroweak cross section. Within the SM, the latter turns out to be not accessible at the LHC even in the high-luminosity phase
Interpreting top-quark LHC measurements in the standard-model effective field theory
No full textThis note proposes common standards and prescriptions for the effective-field-theory interpretation of top-quark measurements at the LHC
The SMEFTsim package, theory and tools
No full textWe report codes for the Standard Model Effective Field Theory (SMEFT) in FeynRules — the SMEFTsim package. The codes enable theoretical predictions for dimension six operator corrections to the Standard Model using numerical tools, where predictions can be made based on either the electroweak input parameter set {α^ew m^Z G^ F} or {m^W m^Z G^F}. All of the baryon and lepton number conserving operators present in the SMEFT dimension six Lagrangian, defined in the Warsaw basis, are included. A flavour symmetric U(3)5 version with possible non-SM CP violating phases, a (linear) minimal flavour violating version neglecting such phases, and the fully general flavour case are each implemented. The SMEFTsim package allows global constraints to be determined on the full Wilson coefficient space of the SMEFT. As the number of parameters present is large, it is important to develop global analyses on reduced sets of parameters minimizing any UV assumptions and relying on IR kinematics of scattering events and symmetries. We simultaneously develop the theoretical framework of a “W-Higgs-Z pole parameter” physics program that can be pursued at the LHC using this approach and the SMEFTsim package. We illustrate this methodology with several numerical examples interfacing SMEFTsim with MadGraph5. The SMEFTsim package can be downloaded at https://feynrules.irmp.ucl.ac.be/wiki/SMEFT
The Standard Model as an Effective Field Theory
Full text linkProjecting measurements of the interactions of the known Standard Model (SM) states into an effective field theory (EFT) framework is an important goal of the LHC physics program. The interpretation of measurements of the properties of the Higgs-like boson in an EFT allows one to consistently study the properties of this state, while the SM is allowed to eventually break down at higher energies. In this review, basic concepts relevant to the construction of such EFTs are reviewed pedagogically. Electroweak precision data is discussed as a historical example of some importance to illustrate critical consistency issues in interpreting experimental data in EFTs. A future precision Higgs phenomenology program can benefit from the projection of raw experimental results into consistent field theories such as the SM, the SM supplemented with higher dimensional operators (the SMEFT) or an Electroweak chiral Lagrangian with a dominantly JP=0+ scalar (the HEFT). We discuss the developing SMEFT and HEFT approaches, that are consistent versions of such EFTs, systematically improvable with higher order corrections, and comment on the pseudo-observable approach. We review the challenges that have been overcome in developing EFT methods for LHC studies, and the challenges that remain
Addendum to: Scheming in the SMEFT. . . and a reparameterization invariance!
Full text linkAbstract We allow two independent flavor contractions for the operator Qll in the U(3)5 flavor symmetric limit and report modified fit results in this limit
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