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 Measuring Higgs boson self-couplings with 2 → 3 VBS processes

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Junmou Chen ◽  
Chih-Ting Lu ◽  
Yongcheng Wu
Keyword(s):  
Higgs Boson ◽  
Cross Sections ◽  
Effective Field Theory ◽  
Vector Boson ◽  
Effective Field ◽  
Low Energy ◽  
Final States ◽  
Lepton Colliders ◽  
Vector Boson Scattering ◽  
Muon Colliders

Abstract We study the measurement of Higgs boson self-couplings through 2 → 3 vector boson scattering (VBS) processes in the framework of Standard Model effective field theory (SMEFT) at both proton and lepton colliders. The SMEFT contribution to the amplitude of the 2 → 3 VBS processes, taking WLWL → WLWLh and WLWL → hhh as examples, exhibits enhancement with the energy $$ \frac{{\mathcal{A}}^{\mathrm{BSM}}}{{\mathcal{A}}^{\mathrm{SM}}}\sim \frac{E^2}{\Lambda^2} $$ A BSM A SM ~ E 2 Λ 2 , which indicates the sensitivity of these processes to the related dimension-six operators in SMEFT. Simulation of the full processes at both hadron and lepton colliders with a variety of collision energies are performed to estimate the allowed region on c6 and $$ {c}_{\Phi_1} $$ c Φ 1 . Especially we find that, with the help of exclusively choosing longitudinal polarizations in the final states and suitable pT cuts, WWh process is as important as the more widely studied triple Higgs production (hhh) in the measurement of Higgs self-couplings. Our analysis indicates that these processes can play important roles in the measurement of Higgs self-couplings at future 100 TeV pp colliders and muon colliders. However, their cross sections are generally tiny at low energy machines, which makes them much more challenging to explore.

scholarly journals Effective Field Theory and Unitarity in Vector Boson Scattering

2016 ◽  
Author(s):  
Marco Sekulla ◽  
Wolfgang Kilian ◽  
Thorsten Ohl ◽  
Jürgen Reuter
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Vector Boson ◽  
Effective Field ◽  
Vector Boson Scattering

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.

Effective Field Theory in Particle Physics and Cosmology

2020 ◽  
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Particle Physics ◽  
Large Scale ◽  
Effective Field ◽  
Effective Theory ◽  
Soft Collinear Effective Theory ◽  
Multiple Length Scales ◽  
Cosmological Observations ◽  
Standard Models

Effective field theory (EFT) is a general method for describing quantum systems with multiple-length scales in a tractable fashion. It allows us to perform precise calculations in established models (such as the standard models of particle physics and cosmology), as well as to concisely parametrize possible effects from physics beyond the standard models. EFTs have become key tools in the theoretical analysis of particle physics experiments and cosmological observations, despite being absent from many textbooks. This volume aims to provide a comprehensive introduction to many of the EFTs in use today, and covers topics that include large-scale structure, WIMPs, dark matter, heavy quark effective theory, flavour physics, soft-collinear effective theory, and more.

scholarly journals Effective theories with dark matter applications

2021 ◽  
Author(s):  
Subhaditya Bhattacharya ◽  
José Wudka
Keyword(s):  
Field Theory ◽  
Dark Matter ◽  
Effective Field Theory ◽  
Particle Physics ◽  
High Energy ◽  
New Physics ◽  
Effective Field ◽  
The Subject ◽  
Effective Theories ◽  
Detailed Nature

Standard Model (SM) of particle physics has achieved enormous success in describing the interactions among the known fundamental constituents of nature, yet it fails to describe phenomena for which there is very strong experimental evidence, such as the existence of dark matter, and which point to the existence of new physics not included in that model; beyond its existence, experimental data, however, have not provided clear indications as to the nature of that new physics. The effective field theory (EFT) approach, the subject of this review, is designed for this type of situations; it provides a consistent and unbiased framework within which to study new physics effects whose existence is expected but whose detailed nature is known very imperfectly. We will provide a description of this approach together with a discussion of some of its basic theoretical aspects. We then consider applications to high-energy phenomenology and conclude with a discussion of the application of EFT techniques to the study of dark matter physics and its possible interactions with the SM. In several of the applications we also briefly discuss specific models that are ultraviolet complete and may realize the effects described by the EFT.

Quantum field theory: An effective theory

2019 ◽  
pp. 111-136
Author(s):  
Jean Zinn-Justin
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Particle Physics ◽  
Statistical Physics ◽  
Mass Scale ◽  
Effective Field ◽  
Quantum Field Theories ◽  
Quantum Field ◽  
Microscopic Scale ◽  
Linear Sigma Models

Chapter 8 discusses effective field theory. This concept is inspired by the theory of critical phenomena in statistical physics and based on renormalization group ideas. The basic idea behind effective field theory is that one starts from a microscopic model involving an infinite number of fluctuating degrees of freedom whose interactions are characterized by a microscopic scale and in which, as a result of interactions, a length that is much larger than the microscopic scale, or, equivalently, a mass much smaller than the characteristic mass scale of the initial model, is generated. The chapter illustrates this topic with examples. It also stresses that all quantum field theories as applied to particle physics or statistical physics are only effective (i.e. not fundamental) theories. Besides the problem of a phi4 type field theory with a large mass field, two more complicated examples are discussed: the Gross–Neveu and the non–linear sigma models.

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 ON RENORMALIZABILITY OF THE EFFECTIVE FIELD THEORY OF MASSIVE YANG–MILLS FIELDS

2012 ◽  
Vol 27 (23) ◽  
pp. 1250128 ◽  
Author(s):  
J. GEGELIA ◽  
G. JAPARIDZE
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Vector Boson ◽  
Effective Field ◽  
Boson Mass ◽  
Yang Mills

Effective field theory (EFT) of massive Yang–Mills fields interacting with fermions is considered. Perturbative renormalizability in the framework of EFT is shown. It is argued that the limit of vanishing vector boson mass leads to massless gauge EFT. Possible relevance for the solution to the strong CP problem is discussed.

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 Completeness and complementarity for μ → eγ, μ → $$ e\overline{e}e $$ and μA → eA

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
S. Davidson
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
New Physics ◽  
Effective Field ◽  
Complementary Information ◽  
Weak Scale ◽  
Lepton Flavour Violation ◽  
Flavour Violation ◽  
Lepton Flavour

Abstract Lepton Flavour Violation (LFV) is New Physics that must occur, but is stringently constrained by experiments searching for μ ↔ e flavour change, such as μ → eγ, μ →$$ e\overline{e}e $$ e e ¯ e or μ → e conversion. However, in an Effective Field Theory(EFT) parametrisation, there are many more μ ↔ e operators than restrictive constraints, so determining operator coefficients from data is a remote dream. It is nonetheless interesting to learn about New Physics from data, so this manuscript introduces “observable-vectors” in the space of operator coefficients, which identify at any scale the combination of coefficients probed by the observable. These vectors have an overlap ≳ 10−3 with most of the coefficients, and are used to study whether μ → eγ, μ →$$ e\overline{e}e $$ e e ¯ e and μ → e conversion give complementary information about New Physics. The appendix gives updated sensitivities of these processes, (and a subset of τ → ℓ decays), to operator coefficients at the weak scale in the SMEFT and in the EFT below mW.

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