scholarly journals Heavy neutral leptons in effective field theory and the high-luminosity LHC

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Giovanna Cottin ◽  
Juan Carlos Helo ◽  
Martin Hirsch ◽  
Arsenii Titov ◽  
Zeren Simon Wang
Keyword(s):  
Field Theory ◽  
Cross Sections ◽  
Effective Field Theory ◽  
Production Cross ◽  
Effective Field ◽  
Atlas Detector ◽  
Neutrino Masses ◽  
High Luminosity ◽  
Mixing Angle ◽  
Active Neutrino

Abstract Heavy neutral leptons (HNLs) with masses around the electroweak scale are expected to be rather long-lived particles, as a result of the observed smallness of the active neutrino masses. In this work, we study long-lived HNLs in NRSMEFT, a Standard Model (SM) extension with singlet fermions to which we add non-renormalizable operators up to dimension-6. Operators which contain two HNLs can lead to a sizable enhancement of the production cross sections, compared to the minimal case where HNLs are produced only via their mixing with the SM neutrinos. We calculate the expected sensitivities for the ATLAS detector and the future far-detector experiments: AL3X, ANUBIS, CODEX-b, FASER, MATHUSLA, and MoEDAL-MAPP in this setup. The sensitive ranges of the HNL mass and of the active-heavy mixing angle are much larger than those in the minimal case. We study both, Dirac and Majorana, HNLs and discuss how the two cases actually differ phenomenologically, for HNL masses above roughly 100 GeV.

scholarly journals SMEFT analysis of vector boson scattering and diboson data from the LHC Run II

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Jacob J. Ethier ◽  
Raquel Gomez-Ambrosio ◽  
Giacomo Magni ◽  
Juan Rojo
Keyword(s):  
Field Theory ◽  
Cross Sections ◽  
Effective Field Theory ◽  
Particle Physics ◽  
Vector Boson ◽  
Effective Field ◽  
High Luminosity ◽  
Complementary Information ◽  
Electroweak Sector ◽  
Vector Boson Scattering

AbstractWe present a systematic interpretation of vector boson scattering (VBS) and diboson measurements from the LHC in the framework of the dimension-six standard model effective field theory (SMEFT). We consider all available measurements of VBS fiducial cross-sections and differential distributions from ATLAS and CMS, in most cases based on the full Run II luminosity, and use them to constrain 16 independent directions in the dimension-six EFT parameter space. Compared to the diboson measurements, we find that VBS provides complementary information on several of the operators relevant for the description of the electroweak sector. We also quantify the ultimate EFT reach of VBS measurements via dedicated projections for the high luminosity LHC. Our results motivate the integration of VBS processes in future global SMEFT interpretations of particle physics data.

scholarly journals Constraints on anomalous couplings of the Higgs boson from pair production searches

2019 ◽  
Vol 222 ◽  
pp. 04003
Author(s):  
Petr Mandrik
Keyword(s):  
Field Theory ◽  
Beyond Standard Model ◽  
Effective Field Theory ◽  
Production Cross ◽  
Hadron Collider ◽  
Effective Field ◽  
Point Of View ◽  
Atlas Detector ◽  
Anomalous Couplings ◽  
Atlas Experiment

The study of the anomalous non-resonant HH production is presented from the point of view of effective field theory (EFT) parameterization. The searches for pp → HH → γγWW, pp → HH → γγbb and pp → HH → bbbb processes by ATLAS experiment at the Large Hadron Collider (LHC) are reproduced. The selection efficiencies and exclusion limits on the HH production cross for different Beyond Standard Model (BSM) EFT benchmark models are obtained using the fast Monte-Carlo simulation of the ATLAS detector.

scholarly journals Long-lived heavy neutral leptons at the LHC: four-fermion single-NR operators

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Rebeca Beltrán ◽  
Giovanna Cottin ◽  
Juan Carlos Helo ◽  
Martin Hirsch ◽  
Arsenii Titov ◽  
...  
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Effective Field Theory ◽  
New Physics ◽  
Effective Field ◽  
High Luminosity ◽  
The Past ◽  
The Standard Model ◽  
Model Independent

Abstract Interest in searches for heavy neutral leptons (HNLs) at the LHC has increased considerably in the past few years. In the minimal scenario, HNLs are produced and decay via their mixing with active neutrinos in the Standard Model (SM) spectrum. However, many SM extensions with HNLs have been discussed in the literature, which sometimes change expectations for LHC sensitivities drastically. In the NRSMEFT, one extends the SM effective field theory with operators including SM singlet fermions, which allows to study HNL phenomenology in a “model independent” way. In this paper, we study the sensitivity of ATLAS to HNLs in the NRSMEFT for four-fermion operators with a single HNL. These operators might dominate both production and decay of HNLs, and we find that new physics scales in excess of 20 TeV could be probed at the high-luminosity LHC.

scholarly journals Probing the nonunitarity of the leptonic mixing matrix at the CEPC

2016 ◽  
Vol 31 (33) ◽  
pp. 1644006 ◽  
Author(s):  
Stefan Antusch ◽  
Oliver Fischer
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Effective Field Theory ◽  
New Physics ◽  
Effective Field ◽  
Neutrino Masses ◽  
Performance Parameters ◽  
The Standard Model ◽  
Mixing Matrix ◽  
Theory Framework

The nonunitarity of the leptonic mixing matrix is a generic signal of new physics aiming at the generation of the observed neutrino masses. We discuss the Minimal Unitarity Violation (MUV) scheme, an effective field theory framework which represents the class of extensions of the Standard Model (SM) by heavy neutral leptons, and discuss the present bounds on the nonunitarity parameters as well as estimates for the sensitivity of the CEPC, based on the performance parameters from the preCDR.

scholarly journals A complete effective field theory for dark matter

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Juan Carlos Criado ◽  
Abdelhak Djouadi ◽  
Manuel Pérez-Victoria ◽  
José Santiago
Keyword(s):  
Field Theory ◽  
Dark Matter ◽  
Cross Sections ◽  
Effective Field Theory ◽  
Direct Detection ◽  
Mass Splitting ◽  
Effective Field ◽  
Set Constraints ◽  
The Impact ◽  
Analytical Expressions

Abstract We present an effective field theory describing the relevant interactions of the Standard Model with an electrically neutral particle that can account for the dark matter in the Universe. The possible mediators of these interactions are assumed to be heavy. The dark matter candidates that we consider have spin 0, 1/2 or 1, belong to an electroweak multiplet with arbitrary isospin and hypercharge and their stability at cosmological scales is guaranteed by imposing a ℤ2 symmetry. We present the most general framework for describing the interaction of the dark matter with standard particles, and construct a general non-redundant basis of the gauge-invariant operators up to dimension six. The basis includes multiplets with non-vanishing hypercharge, which can also be viable DM candidates. We give two examples illustrating the phenomenological use of such a general effective framework. First, we consider the case of a scalar singlet, provide convenient semi-analytical expressions for the relevant dark matter observables, use present experimental data to set constraints on the Wilson coefficients of the operators, and show how the interplay of different operators can open new allowed windows in the parameter space of the model. Then we study the case of a lepton isodoublet, which involves coannihilation processes, and we discuss the impact of the operators on the particle mass splitting and direct detection cross sections. These examples highlight the importance of the contribution of the various non-renormalizable operators, which can even dominate over the gauge interactions in certain cases.

scholarly journals Extending low energy effective field theory with a complete set of dimension-7 operators

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Yi Liao ◽  
Xiao-Dong Ma ◽  
Quan-Yu Wang
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Cross Sections ◽  
Effective Field Theory ◽  
Degrees Of Freedom ◽  
Independent Set ◽  
Effective Field ◽  
Low Energy ◽  
Tree Level ◽  
The Standard Model

Abstract We present a complete and independent set of dimension-7 operators in the low energy effective field theory (LEFT) where the dynamical degrees of freedom are the standard model five quarks and all of the neutral and charged leptons. All operators are non-Hermitian and are classified according to their baryon (∆B) and lepton (∆L) numbers violated. Including Hermitian-conjugated operators, there are in total 3168, 750, 588, 712 operators with (∆B, ∆L) = (0, 0), (0, ±2), (±1, ∓1), (±1, ±1) respectively. We perform the tree-level matching with the standard model effective field theory (SMEFT) up to dimension-7 (dim-7) operators in both LEFT and SMEFT. As a phenomenological application we study the effective neutrino-photon interactions due to dim-7 lepton number violating operators that are induced and much enhanced at one loop from dim-6 operators that in turn are matched from dim-7 SMEFT operators. We compare various neutrino-photon scattering cross sections with their counterparts in the standard model and highlight the new features. Finally, we illustrate how these effective interactions could arise from ultraviolet completion.

scholarly journals DsixTools 2.0: the effective field theory toolkit

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Javier Fuentes-Martín ◽  
Pedro Ruiz-Femenía ◽  
Avelino Vicente ◽  
Javier Virto
Keyword(s):  
Field Theory ◽  
Renormalization Group ◽  
Cross Sections ◽  
Effective Field Theory ◽  
Degrees Of Freedom ◽  
Effective Field ◽  
Low Energy ◽  
Weak Basis ◽  
The Standard Model ◽  
Group Evolution

Abstract is a package for the handling of the standard model effective field theory (SMEFT) and the low-energy effective field theory (LEFT) with operators up to dimension six, both at the algebraic and numerical level. contains a visually accessible and operationally convenient repository of all operators and parameters of the SMEFT and the LEFT. This repository also provides information concerning symmetry categories and number of degrees of freedom, and routines that allow to implement this information on global expressions (such as decay amplitudes and cross-sections). also performs weak basis transformations, and implements the full one-loop Renormalization Group Evolution in both EFTs (with SM beta functions up to five loops in QCD), and the full one-loop SMEFT-LEFT matching at the electroweak scale.

Probing dark matter via effective field theory approach

2020 ◽  
Vol 17 (02) ◽  
pp. 2050028
Author(s):  
Ayşe Elçi̇boğa Kuday ◽  
Ferhat Özok ◽  
Erdinç Ulaş Saka
Keyword(s):  
Field Theory ◽  
Dark Matter ◽  
Cross Sections ◽  
Effective Field Theory ◽  
High Energy ◽  
New Physics ◽  
Theory Model ◽  
Effective Field ◽  
Tree Level ◽  
Theory Approach

We analyze dark matter in most general form of effective field theory approach. To examine the interactions between the weakly interacting massive particles (WIMPs) and the Standard Model (SM) particles, we use the six-dimensional EFT mediated by new physics scale [Formula: see text] at tree level. After implementing a new effective field theory model in FeynRules [FeynRules 2.0 A complete toolbox for tree-level phenomenology, Comput. Phys. Comm. 185(8) (2014) 2250–2300] We investigate the theory and constrain the theory by using relic density generated by MadDM [MadDM v.3.0: A Comprehensive tool for dark matter studies, Phys. Dark Univ. 24 (2019) 100249] tool of MadGraph5_aMC@NLO [The automated computation of tree-level and next-to-leading order differential cross-sections, and their matching to parton shower simulations, J. High Energy Phys. 79 (2014) 2014].

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