scholarly journals Effective field theory versus UV-complete model: vector boson scattering as a case study

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Jannis Lang ◽  
Stefan Liebler ◽  
Heiko Schäfer-Siebert ◽  
Dieter Zeppenfeld
Keyword(s):  
Cross Sections ◽  
Vector Boson ◽  
High Energy ◽  
Effective Field ◽  
Threshold Region ◽  
Validity Range ◽  
Theory Versus ◽  
Bsm Physics ◽  
Vector Boson Scattering

AbstractEffective field theories (EFT) are commonly used to parameterize effects of BSM physics in vector boson scattering (VBS). For Wilson coefficients which are large enough to produce presently observable effects, the validity range of the EFT represents only a fraction of the energy range covered by the LHC, however. In order to shed light on possible extrapolations into the high energy region, a class of UV-complete toy models, with extra SU(2) multiplets of scalars or of fermions with vector-like weak couplings, is considered. By calculating the Wilson coefficients up to energy-dimension eight, and full one-loop contributions to VBS due to the heavy multiplets, the EFT approach, with and without unitarization at high energy, is compared to the perturbative prediction. For high multiplicities, e.g. nonets of fermions, the toy models predict sizable effects in transversely polarized VBS, but only outside the validity range of the EFT. At lower energies, dimension-eight operators are needed for an adequate description of the models, providing another example that dimension-eight can be more important than dimension-six operators. A simplified VBFNLO implementation is used to estimate sensitivity of VBS to such BSM effects at the LHC. Unitarization captures qualitative features of the toy models at high energy but significantly underestimates signal cross sections in the threshold region of the new particles.

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 Vector boson fusion at multi-TeV muon colliders

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Antonio Costantini ◽  
Federico De Lillo ◽  
Fabio Maltoni ◽  
Luca Mantani ◽  
Olivier Mattelaer ◽  
...  
Keyword(s):  
Cross Sections ◽  
Vector Boson ◽  
High Energy ◽  
New Physics ◽  
Vector Boson Fusion ◽  
Weak Boson ◽  
Wide Range ◽  
Lepton Colliders ◽  
Muon Colliders ◽  
New Phenomena

Abstract High-energy lepton colliders with a centre-of-mass energy in the multi-TeV range are currently considered among the most challenging and far-reaching future accelerator projects. Studies performed so far have mostly focused on the reach for new phenomena in lepton-antilepton annihilation channels. In this work we observe that starting from collider energies of a few TeV, electroweak (EW) vector boson fusion/scattering (VBF) at lepton colliders becomes the dominant production mode for all Standard Model processes relevant to studying the EW sector. In many cases we find that this also holds for new physics. We quantify the size and the growth of VBF cross sections with collider energy for a number of SM and new physics processes. By considering luminosity scenarios achievable at a muon collider, we conclude that such a machine would effectively be a “high-luminosity weak boson collider,” and subsequently offer a wide range of opportunities to precisely measure EW and Higgs couplings as well as discover new particles.

scholarly journals Observation of ZZ production via Vector Boson Scattering in ATLAS

2021 ◽  
Vol 2105 (1) ◽  
pp. 012013
Author(s):  
Ioannis Maznas
Keyword(s):  
Cross Sections ◽  
Vector Boson ◽  
Statistical Significance ◽  
Signal Strength ◽  
Atlas Detector ◽  
Pp Collisions ◽  
Final State ◽  
Measurement Results ◽  
Vector Boson Scattering

Abstract This document presents measurement results of the ZZ production via Vector Boson Scattering interactions in 139fb −1 of data recorded by the ATLAS detector from pp collisions at s = 13 TeV during LHC Run-II (2015-2018). In this study, 127 candidate events with a fully leptonic final state (ℓℓℓℓjj) have been observed and another 82 events for ℓℓvvjj final state, with a contribution of the purely electroweak ZZjj process estimated to be 20.6 ± 2.5 and 12.3 ± 0.7 events respectively. The measured cross sections were found to be 1.27 ± 0.14fb (1.22 ± 0.35fb) for ℓℓℓℓjj (ℓℓvvjj) in their respective fiducial regions. Using multivariant methods, the EW production of ZZjj events (combining the ℓℓℓℓjj and ℓℓvvjj channels) was measured to have a signal strength of 1.35± 0.34, which leads to a rejection of the no-electroweak hypothesis with a statistical significance of 5.5σ.

scholarly journals VECTOR BOSON SCATTERING AND BOUNDARY CONDITIONS IN KALUZA–KLEIN TOY MODEL

2012 ◽  
Vol 27 (17) ◽  
pp. 1250098 ◽  
Author(s):  
PETR MORÁVEK ◽  
JIŘÍ HOŘEJŠÍ
Keyword(s):  
Scattering Amplitudes ◽  
Boundary Conditions ◽  
Vector Boson ◽  
High Energy ◽  
Electroweak Symmetry ◽  
Least Action ◽  
Higher Dimensional ◽  
Principle Of Least Action ◽  
Vector Bosons ◽  
Vector Boson Scattering

We study a simple higher-dimensional toy model of electroweak symmetry breaking, in particular a pure gauge 5D theory on flat background with one extra finite space dimension. The principle of least action and the requirement of gauge independence of scattering amplitudes are used to determine the possible choices of boundary conditions. We demonstrate that for any of these choices the scattering amplitudes of vector bosons do not exhibit power-like growth in the high energy limit. Our analysis is an extension and generalization of the results obtained previously by other authors.

scholarly journals Observation and measurements of vector-boson scattering with the ATLAS detector

2020 ◽  
Vol 35 (34n35) ◽  
pp. 2044002
Author(s):  
Ondřej Penc
Keyword(s):  
Cross Sections ◽  
Vector Boson ◽  
Center Of Mass ◽  
New Physics ◽  
Proton Proton ◽  
Center Of Mass Energy ◽  
Number Of Generators ◽  
Text Production ◽  
Vector Boson Scattering ◽  
Electroweak Boson

The scattering of electroweak bosons tests the gauge structure of the Standard Model and is sensitive to anomalous quartic gauge couplings. In this paper, we present recent results on vector-boson scattering from the ATLAS experiment using proton–proton collisions with a center-of-mass energy of 13 TeV at the LHC. This includes the observation of [Formula: see text], [Formula: see text], and same-sign [Formula: see text] production via vector-boson scattering along with a measurement of [Formula: see text] production ([Formula: see text] denotes [Formula: see text] or [Formula: see text] boson) in semileptonic final states. The results can be used to constrain new physics that manifests as anomalous electroweak-boson self-interactions. Finally, predicted cross-sections for the electroweak scattering of two same-sign [Formula: see text] bosons in association with two jets are compared for a number of generators.

scholarly journals Neutrino non-standard interactions: A status report

2019 ◽  
Author(s):  
Bhupal Dev ◽  
K. S. Babu ◽  
Peter Denton ◽  
Pedro Machado ◽  
Carlos A. Argüelles ◽  
...  
Keyword(s):  
Neutrino Oscillation ◽  
Cross Sections ◽  
Model Building ◽  
High Energy ◽  
Effective Field ◽  
Scattering Data ◽  
Status Report ◽  
Long Baseline ◽  
Open Questions ◽  
Neutrino Mass Models

This report summarizes the present status of neutrino non-standard interactions (NSI). After a brief overview, several aspects of NSIs are discussed, including connection to neutrino mass models, model-building and phenomenology of large NSI with both light and heavy mediators, NSI phenomenology in both short- and long-baseline neutrino oscillation experiments, neutrino cross-sections, complementarity of NSI with other low- and high-energy experiments, fits with neutrino oscillation and scattering data, DUNE sensitivity to NSI, effective field theory of NSI, as well as the relevance of NSI to dark matter and cosmology. We also discuss the open questions and interesting future directions that can be pursued by the community at large. This report is based on talks and discussions during the Neutrino Theory Network NSI workshop held at Washington University in St.~Louis from May 29-31, 2019

scholarly journals Precision SMEFT bounds from the VBF Higgs at high transverse momentum

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Jack Y. Araz ◽  
Shankha Banerjee ◽  
Rick S. Gupta ◽  
Michael Spannowsky
Keyword(s):  
Standard Model ◽  
Vector Boson ◽  
High Energy ◽  
Effective Field ◽  
Higgs Bosons ◽  
Quadratic Growth ◽  
Final States ◽  
High Transverse Momentum ◽  
The Standard Model ◽  
Independent Operator

Abstract We study the production of Higgs bosons at high transverse momenta via vector-boson fusion (VBF) in the Standard Model Effective Field Theory (SMEFT). We find that contributions from four independent operator combinations dominate in this limit. These are the same ‘high energy primaries’ that control high energy diboson processes, including Higgs-strahlung. We perform detailed collider simulations for the diphoton decay mode of the Higgs boson as well as the three final states arising from the ditau channel. Using the quadratic growth of the SMEFT contributions relative to the Standard Model (SM) contribution, we project very stringent bounds on these operators that far surpass the corresponding bounds from the LEP experiment.

UNITARITY BOUNDS ON WW SCATTERING AND ELECTROWEAK TESTS AT LEP

1993 ◽  
Vol 08 (07) ◽  
pp. 647-660
Author(s):  
G. GOUNARIS ◽  
F.M. RENARD ◽  
D. SCHILDKNECHT
Keyword(s):  
Integral Representation ◽  
Partial Wave ◽  
Upper Bound ◽  
Top Quark ◽  
Wave Amplitude ◽  
Vector Boson ◽  
High Energy ◽  
Partial Wave Amplitude ◽  
Vector Boson Scattering ◽  
Higgs Scalar

Replacing elementary Higgs exchange in vector-boson scattering by an angular-momentum-zero unitarity-saturating partial wave amplitude described by a dispersion relation which incorporates low-energy gauge theory and high-energy partial-wave unitarity constraints, we find an upper bound of Λ≲Λmax≅0.8 TeV for the scale, Λ, at which saturation of partial wave unitarity is to occur. Upon inserting the partial wave amplitude into a novel integral representation for the bosonic vacuum polarization contribution to the electroweak ρ parameter, Δρb, we establish an upper bound on −Δρb(≲0.033), while for the case of the elementary Higgs scalar, the integral representation reproduces the well known ln mH/mW formula for Δρb. The upper bound on −Δρb implies that the value of the mass of the top quark extracted from LEP1 measurements becomes justified even in the case when the Higgs scalar is replaced by a strong-interaction-like J=0 partial wave.

PHOTOPRODUCTION OF WEAK VECTOR BOSONS IN A SPINOR THEORY

1993 ◽  
Vol 08 (22) ◽  
pp. 3883-3908 ◽  
Author(s):  
E.H. LEMKE
Keyword(s):  
Cross Sections ◽  
W Boson ◽  
High Energy ◽  
Intermediate Energy ◽  
Threshold Region ◽  
Mass Relation ◽  
Spinor Theory ◽  
Weak Boson ◽  
Energy Behavior ◽  
Abelian Case

We put forward the hypothesis that the weak W boson be a compound of two 2-component Lorentz spinors. The resulting novel γWW vertex is no gauge field structure. Nevertheless, the Born amplitude of γγ→WLWL respects partial-wave unitarity. As in the Yang-Mills case, the amplitude consists of a direct term, a crossed term, and a sea-gull term, and no unobserved particles are to be involved to get the “good” high-energy behavior. This is due to an imaginary pseudoscalar γWW interaction term. Significant differences between angular distributions and total cross sections of the non-Abelian case and the case of the composite bosons are displayed. The unitarity constraint applied to the reaction γγ→WTWT leads to the prediction of the existence of a composite charged weak scalar Φ±. It constitutes the spin 0 state of the constituents forming W±. Furthermore, the existence of a second and heavy scalar-vector pair ω-X is predicted. These weak boson states are found to exclude the presence of a seagull graph. In the threshold region, the total cross section of γγ→WW in the compositeness case is smaller than in the non-Abelian case. In a broad intermediate energy region it can be larger. Upper unitarity mass-bounds are estimated. They suggest mΦ≈mw so that Φ± might be discovered by forthcoming experiments. The structure of the γΦW, γXW and γωW transition vertices can be inferred without making recourse to unitarity. However, unitarity requires that the mass relation mΦ/mW=mω/mX be valid.

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