Gauge Coupling Research Articles

Coupled vector gauge fields in teleparallel scalar-kinetic branes

Coupled vector gauge fields in teleparallel scalar-kinetic branes

Observable proton decay and gauge coupling unification in the improved missing doublet SU(5) model

Observable proton decay and gauge coupling unification in the improved missing doublet SU(5) model

Dark matter from the centre of SU(N)

A dark sector with non-abelian gauge symmetry provides a sound framework to justify stable dark matter (DM) candidates. We consider scalar fields charged under a SU(N)SU(N) gauge group, and show that the centre of SU(N)SU(N), the discrete subgroup Z_NZN also known as NN-ality, can ensure the stability of scalar DM particles. We analyse in some details two minimal DM models of this class, based on SU(2)SU(2) and SU(3)SU(3), respectively. These models have non-trivial patterns of spontaneous symmetry breaking, leading to distinctive phenomenological implications. For the SU(2)SU(2) model these include a specific interplay of two DM states, with the same interactions but different masses, and several complementary DM annihilation regimes, either within the dark sector or through the Higgs portal. The SU(3)SU(3) model predicts dark radiation made of a pair of dark photons with a unique gauge coupling, as well as regimes where DM semi-annihilations become dominant and testable.

Pauli-term-induced fixed points in d-dimensional QED

We explore the fixed-point structure of QED-like theories upon the inclusion of a Pauli spin-field coupling. We concentrate on the fate of UV-stable fixed points recently discovered in d=4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=4$$\\end{document} spacetime dimensions upon generalizations to lower as well as higher dimensions for an arbitrary number of fermion flavors Nf.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_{\ ext {f}}.$$\\end{document} As an overall trend, we observe that going away from d=4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=4$$\\end{document} dimensions and increasing the flavor number tends to destabilize the non-Gaussian fixed points discovered in four spacetime dimensions. A notable exception is a non-Gaussian fixed point at finite Pauli spin-field coupling but vanishing gauge coupling, which also remains stable down to d=3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=3$$\\end{document} dimensions and for small flavor numbers. This includes also the range of degrees of freedom used in effective theories of layered condensed-matter systems. As an application, we construct renormalization group trajectories that emanate from the non-Gaussian fixed point and approach a long-range regime in the conventional QED3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${}_3$$\\end{document} universality class that is governed by the interacting (quasi) fixed point in the gauge coupling.

The emergence proposal and the emergent string

We explore the Emergence Proposal for the moduli metric and the gauge couplings in a concrete model with 7 saxionic and 7 axionic moduli fields, namely the compactification of the type IIA superstring on a 6-dimensional toroidal orbifold. We show that consistency requires integrating out precisely the 12 towers of light particle species arising from KK and string/brane winding modes and one asymptotically tensionless string up to the species scale. After pointing out an issue with the correct definition of the species scale in the presence of string towers, we carry out the emergence computation and find that the KK and winding modes indeed impose the classical moduli dependence on the one-loop corrections, while the emergent string induces moduli dependent logarithmic suppressions. The interpretation of these results for the Emergence Proposal are discussed revealing a couple of new and still not completely settled aspects.

On the two-loop BSM corrections to h⟶γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h\\longrightarrow \\gamma \\gamma $$\\end{document} in the aligned THDM

We compute the two-loop BSM contributions to the h⟶γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h\\longrightarrow \\gamma \\gamma $$\\end{document} decay width in the aligned THDM. We adopt the simplifying assumptions of vanishing EW gauge couplings and vanishing mass of the SM-like Higgs boson, which allow us to exploit a low-energy theorem connecting the hγγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h\\gamma \\gamma $$\\end{document} amplitude to the derivative of the photon self-energy w.r.t. the Higgs field. We briefly discuss the numerical impact of the newly-computed contributions, showing that they may be required for a precise determination of Γ[h→γγ]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Gamma [h\\rightarrow \\gamma \\gamma ]$$\\end{document} in scenarios where the quartic Higgs couplings are large.

The [formula omitted] vertex in a left–right model

We consider the one-loop corrections to the Zbb¯ vertex in a CP-conserving left–right model (LRM), viz. a model with gauge group SU(2)L×SU(2)R×U(1). We allow the gauge coupling constants of SU(2)L and SU(2)R to be different. The spontaneous symmetry breaking is accomplished only by doublets and/or singlets of SU(2)L and SU(2)R. The lightest massive neutral gauge boson of our LRM is assumed to have the same Yukawa couplings to bottom-quark pairs as the Z of the Standard Model (SM); this assumption has the advantage that, then, the infrared divergences automatically cancel down in the subtraction of the Zbb¯ vertex in the SM from the same vertex in the LRM. We effect a proper renormalization of the Zbb¯ vertex and check explicitly both its gauge invariance and the cancellation of all the ultraviolet divergences. We find out that a LRM with the above assumptions cannot achieve a better fit to the Zbb¯ vertex than a multi-Higgs extension of the SM, viz. both models can only achieve a decent fit when one admits scalar particles with very low masses ≲50 GeV. This is true even when we allow for markedly different gauge coupling constants of SU(2)L and SU(2)R.

Projected sensitivity to dimension-6 triple gauge couplings at the FCC-hh

In this study, we investigate the process pp→W±γ for the physics potential of the FCC-hh with s=100 TeV to examine the anomalous WWγ couplings defined by three CP-conserving and two CP-violating effective operators of dimension-6. The analysis containing the realistic detector effects is carried out in the mode where W± bosons in the final state decay into the leptonic channel. The best sensitivities obtained from the process pp→W±γ on the anomalous couplings CWWW/Λ2 and CW,B/Λ2 determined by CP-conserving effective Lagrangians are [−0.010;0.010] TeV−2 and [−0.40;0.41] TeV−2, while CW˜WW/Λ2 and CW˜/Λ2 couplings defined by CP-violating effective Lagrangian are obtained as [−0.003;0.003] TeV−2 and [−0.32;0.33] TeV−2 at the FCC-hh with Lint=30 ab−1. However, if the systematic uncertainty is included, we obtain reduced sensitivities on the anomalous WWγ coupling. The results are compared for assumed systematics of 5% and 10%.

Concept of the basic standard model and a relation between the three gauge coupling constants

Among the known elementary particles, 15 are not massless. In the Lagrangian of the standard model, the Higgs particle couples to all 15 of them to give them their respective masses. In this paper, a new model is proposed, where in the Lagrangian, the Higgs particle couples only to the four heaviest known elementary particles [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], all with masses in the vicinity of [Formula: see text], but not to the other 11. In this model, the masses of these 11 elementary particles that do not couple directly to the Higgs particle are generated by radiative corrections. Because of the reduction of the number of terms in the Lagrangian, this model is referred to as the basic standard model. By studying how the bottom quark can acquire a mass, it is found that there must be a relation between the three gauge coupling constants of the gauge group [Formula: see text]. This relation between these coupling constants is the first prediction, on purely theoretical grounds without using any experimental input, of the basic standard model, and is studied in some detail. In particular, this new prediction is found to be in good agreement with experimental measurements.

Search for leptoquarks decaying into the bτ final state in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{\ extrm{s}} $$\\end{document} = 13 TeV with the ATLAS detector

A search for leptoquarks decaying into the bτ final state is performed using Run 2 proton-proton collision data from the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1 at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV recorded by the ATLAS detector. The benchmark models considered in this search are vector leptoquarks with electric charge of 2/3e and scalar leptoquarks with an electric charge of 4/3e. No significant excess above the Standard Model prediction is observed, and 95% confidence level upper limits are set on the cross-section times branching fraction of leptoquarks decaying into bτ. For the vector leptoquark production two models are considered: the Yang-Mills and Minimal coupling models. In the Yang-Mills (Minimal coupling) scenario, vector leptoquarks with a mass below 1.58 (1.35) TeV are excluded for a gauge coupling of 1.0 and below 2.05 (1.99) TeV for a gauge coupling of 2.5. In the case of scalar leptoquarks, masses below 1.28 (1.53) TeV are excluded for a Yukawa coupling of 1.0 (2.5). Finally, an interpretation of the results with minimal model dependence is performed for each of the signal region categories, and limits on the visible cross-section for beyond the Standard Model processes are provided.

Limits to gauge coupling in the dark sector of super-heavy dark matter particles from the Pierre Auger Observatory data

Assuming that the energy density of super-heavy particles matches that of dark matter observed today, tight constraints on the couplings governing the decay process are presented as a function of the particle mass. These constraints are obtained from the lack of signatures that would be suggestive of decaying super-heavy XX particles in the data of the Pierre Auger Observatory. In particular, instanton-induced decay processes allow us to derive a bound on the reduced coupling constant of gauge interactions in the dark sector: \alpha_X \lesssim 0.09αX≲0.09, for 10^{9} \lesssim M_X/\mathrm{GeV} < 10^{19}109≲MX/GeV<1019. Cosmological aspects for super-heavy dark matter production during the reheating epoch are discussed.

Probing general U(1)′ models with non-universal lepton charges at FASER/FASER2, COHERENT and long-baseline oscillation experiments

The general anomaly-free U(1)′ models allow non-universal lepton charges. We explore the sensitivities of FASER/FASER2, COHERENT and DUNE/T2HK precision experiments to the new gauge boson Z′ and the new CP-even scalar ϕ. With non-universal lepton charges, distinctive reaches at FASER/FASER2 emerge in the regime of low mZ′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {m}_{Z^{\\prime }} $$\\end{document} and small gauge coupling gBL for different U(1)′ charge setups. The COHERENT experiment and the future long-baseline experiments DUNE/T2HK also provide complementary probes to the available parameter space. For mϕ< 2mZ′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {m}_{Z^{\\prime }} $$\\end{document}, the search for the scalar ϕ at FASER/FASER2 is sensitive to the mixing angle between the scalar singlet and the SM Higgs. In the case of mϕ> 2mZ′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {m}_{Z^{\\prime }} $$\\end{document}, the kinematically allowed decay ϕ → Z′Z′ changes the lifetime and decay rates of the scalar ϕ. The sensitivity reach highly depends on the Z′ mass and the gauge coupling gBL.

UV completion of extradimensional Yang-Mills theory for Gauge-Higgs unification

The SU(N)SU(N) Yang-Mills theory in \mathbb R^4\times S^1ℝ4×S1 spacetime is studied as a simple toy model of Gauge-Higgs unification. The theory is perturbatively nonrenormalizable but could be formulated as an asymptotically safe theory, namely a nonperturbatively renormalizable theory. We study the fixed point structure of the Yang-Mills theory in \mathbb R^4\times S^1ℝ4×S1 by using the functional renormalization group in the background field approximation. We derive the functional flow equations for the gauge coupling and the background gauge-field potential. There exists a nontrivial fixed point for both couplings at finite compactification radii. At the fixed point, gauge coupling and vacuum energy are both relevant. The renormalization group flow of the gauge coupling describes the smooth transition between the ultraviolet asymptotically safe regime and the strong interacting infrared limit.

Many-body non-Hermitian skin effect under dynamic gauge coupling

Many-body non-Hermitian skin effect under dynamic gauge coupling

Exact large charge in mathcal{N} = 4 SYM and semiclassical string theory

In four-dimensional mathcal{N} = 4 super Yang-Mills theory with gauge group SU(N), we present a closed-form solution for a family of integrated four-point functions involving stress tensor multiplet composites of arbitrary R-charge. These integrated correlators are shown to be equivalent to a one-dimensional semi-infinite lattice of harmonic oscillators with nearest-neighbor interactions, evolving over the fundamental domain of SL(2, ℤ). The solution, exceptionally simple in an SL(2, ℤ)-invariant eigenbasis, is exact in the R-charge p, rank N, and complexified gauge coupling τ. This permits a systematic and non-perturbative large charge expansion for any N and τ. Especially novel is a double-scaled “gravity regime” in which p ~ N2 ≫ 1, holographically dual to a large charge regime of semiclassical type IIB string theory in AdS5 × S5. Our results in this limit provide a holographic computation of integrated semiclassical string amplitudes at arbitrary string coupling, including an emergent string scale with a large charge dressing factor. We compare to extremal correlators in superconformal QCD, for which we predict new genus expansions at large charge scaling with N.

Anomalous triple gauge couplings in electroweak dilepton tails at the LHC and interference resurrection

We study the electroweak dilepton production with two forward jets at the LHC, aiming to measure the anomalous triple gauge couplings in the Effective Field Theory (EFT) approach. This process exhibits a distinctive feature, namely, the interference between Standard Model (SM) and beyond the SM is resurrected in the inclusive cross section of the full amplitude, including two forward jets. As a concrete illustration, we perform the detailed analytic and numerical study of the interference using a simpler toy process, and discuss the subtlety of the effective W approximation. We propose a new kinematic variable, VBFhardness, that controls the amount of energy flowing into the dilepton subprocess. We show that an appropriate cut on VBFhardness makes the interference resurrection manifest. Finally, we use the invariant mass of the dilepton system as well as the transverse momentum, as done in the literature, to derive the sensitivity to anomalous triple gauge couplings at the LHC and the high luminosity LHC. Our result is compared with the existing limits from the experiments.

Search for high-mass exclusive γγ → WW and γγ → ZZ production in proton-proton collisions at sqrt{s} = 13 TeV

A search is performed for exclusive high-mass γγ → WW and γγ → ZZ production in proton-proton collisions using intact forward protons reconstructed in near-beam detectors, with both weak bosons decaying into boosted and merged jets. The analysis is based on a sample of proton-proton collisions collected by the CMS and TOTEM experiments at sqrt{s} = 13 TeV, corresponding to an integrated luminosity of 100 fb−1. No excess above the standard model background prediction is observed, and upper limits are set on the pp → pWWp and pp → pZZp cross sections in a fiducial region defined by the diboson invariant mass m(VV) > 1 TeV (with V = W, Z) and proton fractional momentum loss 0.04 < ξ < 0.20. The results are interpreted as new limits on dimension-6 and dimension-8 anomalous quartic gauge couplings.

Investigation of anomalous triple gauge couplings in μγ collision at multi-TeV muon colliders

The pursuit of discovery in particle physics has always required study at the highest possible energies. Multi-TeV muon colliders, which have important advantages, offer unprecedented potential for investigating new physics beyond the Standard Model. We extensively assume a range of center-of-mass energies from 3 to 30 TeV and a range of integrated luminosities from 1 to 90 ab−1 for future multi-TeV muon colliders. We perform a phenomenological study of the anomalous WWγ couplings via the process [Formula: see text] using a model-independent analysis in the effective field theory framework at multi-TeV muon colliders. The sensitivity estimates obtained for the anomalous WWγ couplings at systematic uncertainties of δsys = 0%, 3%, 5% are compared with the experimental results. Our best sensitivity limits at 95% confidence level for cWWW/Λ2, [Formula: see text], c B /Λ2, c W /Λ2, and [Formula: see text] couplings are [−0.030; 0.025], [−0.014; 0.014], [−0.185; 0.187], [−0.187; 0.189], and [−1.177; 1.097] TeV−2 at the multi-TeV muon collider with center-of-mass energy of 30 TeV and integrated luminosity of 90 ab−1, respectively.

A condition for the reduction of couplings in the [formula omitted] supersymmetric theories

We demonstrate that in the P=13Q supersymmetric theories the renormalization group invariance of the ratio λijk/e (of the Yukawa couplings to the gauge coupling) is equivalent to a simple relation between the anomalous dimensions of the quantum gauge superfield, of the Faddeev–Popov ghosts, and of the matter superfields, which should be valid in each order of the perturbation theory. In the one- and two-loop approximations it is verified explicitly. Presumably, in higher orders this relation can be satisfied for the planar supergraphs under a certain renormalization prescription. Assuming that it is valid we rewrite the exact equation for the (corresponding contribution to the) anomalous dimension of the matter superfields in the theories under consideration in a different (but equivalent) form.

How robust are particle physics predictions in asymptotic safety?

The framework of trans-Planckian asymptotic safety has been shown to generate phenomenological predictions in the Standard Model and in some of its simple new physics extensions. A heuristic approach is often adopted, which bypasses the functional renormalization group by relying on a parametric description of quantum gravity with universal coefficients that are eventually obtained from low-energy observations. Within this approach a few simplifying approximations are typically introduced, including the computation of matter renormalization group equations at 1 loop, an arbitrary definition of the position of the Planck scale at 10^{19},textrm{GeV}, and an instantaneous decoupling of gravitational interactions below the Planck scale. In this work we systematically investigate, both analytically and numerically, the impact of dropping each of those approximations on the predictions for certain particle physics scenarios. In particular we study two extensions of the Standard Model, the gauged B-L model and the leptoquark S_3 model, for which we determine a set of irrelevant gauge and Yukawa couplings. In each model, we present numerical and analytical estimates of the uncertainties associated with the predictions from asymptotic safety.