Cancellation Of Quadratic Divergences Research Articles

Off-Shell Higgs Probe of Naturalness.

Examining the Higgs sector at high energy scales through off-shell Higgs production can potentially shed light on the naturalness problem of the Higgs boson mass. We propose such a study at the LHC by utilizing a representative model with a new scalar field (S) coupled to the standard model Higgs doublet (H) in a form |S|^{2}|H|^{2}. In the process pp→h^{*}→ZZ, the dominant momentum-dependent part of the one-loop scalar singlet corrections, especially above the new threshold at 2m_{S}, leads to a measurable deviation in the differential distribution of the Z-pair invariant mass, in accordance with the quadratic divergence cancellation to the Higgs mass. We find that it is conceivable to probe such new physics at the 5σ level at the high-luminosity LHC, improving further with the upgraded 27TeV LHC, without requiring the precise measurement of the Higgs boson total width. The discovery of such a Higgs portal could also have important implications for thermal dark matter as well as for electroweak baryogenesis.

Implication of quadratic divergences cancellation in the two Higgs doublet model

With the aim of exploring the Higgs sector of the Two Higgs Doublet Model (2HDM), we have chosen the exact and soft Z2 symmetry breaking versions of the 2HDM with non-zero vacuum expectation values for both Higgs doublets (Mixed Model). We consider two SM-like scenarios: with 125 GeV h and 125 GeV H. We have applied the condition for cancellation of quadratic divergences in the type II 2HDM in order to derive masses of the heavy scalars. Solutions of two relevant conditions were found in the considered SM-like scenarios. After applying the current LHC data for the observed 125 GeV Higgs boson, the precision electroweak data test and lower limits on the mass of H+, the allowed region of parameters shrink strongly.

The composite twin Higgs scenario

Based on an explicit model, we propose and discuss the generic features of a possible implementation of the Twin Higgs program in the context of composite Higgs models. We find that the Twin Higgs quadratic divergence cancellation argument can be uplifted to a genuine protection of the Higgs potential, based on symmetries and selection rules, but only under certain conditions which are not fulfilled in some of the existing models. We also find that a viable scenario, not plagued by a massless Twin Photon, can be obtained by not gauging the Twin Hypercharge and taking this as the only source of Twin Symmetry breaking at a very high scale.

Masses of physical scalars in two Higgs doublet models

We find bounds on scalar masses resulting from a criterion of naturalness, in a broad class of two Higgs doublet models (2HDMs). Specifically, we assume the cancellation of quadratic divergences in what are called the type I, type II, lepton-specific and flipped 2HDMs, with an additional U(1) symmetry. This results in a set of relations among masses of the physical scalars and coupling constants, a generalization of the Veltman conditions of the Standard Model. Assuming that the lighter $CP$-even neutral Higgs particle is the observed scalar particle of mass $\sim$125 GeV, and imposing further the constraints from the electroweak T-parameter, stability, and perturbative unitarity, we calculate the range of the mass of each of the remaining physical scalars.

Exotic top partners and Little Higgs

Little Higgs models often give rise to top partners beyond the minimal ones necessary for the cancellation of quadratic divergences. We review how this occurs and discuss the phenomenology of these exotic states. We emphasize the possible importance of new pseudo-Nambu-Goldstone bosons in top partner decays. Indeed, cascade decays of exotic top partners may be the best way to discover these new bosons. We illustrate these points with a new Little Higgs construction based on an SO(10)/SO(5)^2 coset structure, which fills a gap in the model building literature. These observations motivate new search strategies for top partners at the LHC, including for final states with b-jets and a large multiplicity of electroweak bosons.

New Probe of Naturalness

Any new scalar fields that perturbatively solve the hierarchy problem by stabilizing the Higgs boson mass also generate new contributions to the Higgs boson field-strength renormalization, irrespective of their gauge representation. These new contributions are physical, and in explicit models their magnitude can be inferred from the requirement of quadratic divergence cancellation; hence, they are directly related to the resolution of the hierarchy problem. Upon canonically normalizing the Higgs field, these new contributions lead to modifications of Higgs couplings that are typically great enough that the hierarchy problem and the concept of electroweak naturalness can be probed thoroughly within a precision Higgs boson program. Specifically, at a lepton collider this can be achieved through precision measurements of the Higgs boson associated production cross section. This would lead to indirect constraints on perturbative solutions to the hierarchy problem in the broadest sense, even if the relevant new fields are gauge singlets.

Natural Two‐Higgs‐Doublet Model

AbstractWe show that the Two‐Higgs‐Doublet Model (2HDM) constrained by the two‐loop‐order requirement of cancellation of quadratic divergences is consistent with the existing experimental constraints. The model allows to ameliorate the little hierarchy problem by suppressing the quadratic corrections to scalar masses and lifting the mass of the lightest Higgs boson. A strong source of CP violation emerges from the scalar potential. The cutoff originating from the naturality arguments is shifted from ∼ 0.6 TeV in the Standard Model to ≳ 6 TeV in the 2HDM, depending on the mass of the lightest scalar.

Tuned Two-Higgs-Doublet Model

We consider a Two-Higgs-Doublet Model (2HDM) constrained by the condition that assures cancellation of quadratic divergences up to the leading two-loop order. Regions in the parameter space consistent with existing experimental constraints and with the cancellation condition are determined. The possibility for CP violation in the scalar potential is discussed and regions of tan β − MH± with substantial amount of CP violation are found. The model allows to ameliorate the little hierarchy problem by lifting the minimal scalar Higgs boson mass and by suppressing the quadratic corrections to scalar masses. The cutoff originating from the naturality arguments is therefore lifted from ∼ 0.6 TeV in the Standard Model to ≳ 2.5 TeV in the 2HDM, depending on the mass of the lightest scalar.

Minimal Lee–Wick extension of the Standard Model

We consider a minimal Lee–Wick (LW) extension to the Standard Model in which the fields providing the most important contributions to the cancellation of quadratic divergences are the lightest. Partners to the SU(2) gauge bosons, Higgs, top quark, and left-handed bottom quark are retained in the low-energy effective theory, which is valid up to approximately 10 TeV; the remaining LW partners appear above this cutoff and complete the theory in the ultraviolet. We determine the constraints on the low-energy spectrum from the electroweak parameters S and T, and find LW states within the kinematic reach of the LHC at the 95% confidence level.

Double Higgs production and quadratic divergence cancellation in little Higgs models with T-parity

We analyze double Higgs boson production at the Large Hadron Collider in the context of Little Higgs models. In double Higgs production, the diagrams involved are directly related to those that cause the cancellation of the quadratic divergence of the Higgs self-energy, providing a robust prediction for this class of models. We find that in extensions of this model with the inclusion of a so-called T-parity, there is a significant enhancement in the cross sections as compared to the Standard Model.

CANCELING QUADRATIC DIVERGENCES IN A CLASS OF TWO-HIGGS-DOUBLET MODELS

The Newton–Wu conditions for the cancellation of quadratic divergences in a class of two-Higgs-doublet models are analyzed as to how they may be satisfied with a typical extension of the Standard Model of particle interactions.

Naturalness of scales and quadratic divergences in N=1 supergravity

Some conditions for the hierarchy m3/2 ≪ MP to naturally occur in a generic effective supergravity theory are discussed. In particular cancellation of quadratic divergences in the one-loop effective potential are studied in supergravity theories derived from four-dimensional superstring models with supersymmetry broken either at the tree level via compactification or by non-perturbative effects such as gaugino condensation.

Exact cancellation of quadratic divergences in top condensation models

We discuss the hierarchy problem and the corresponding quadratic divergences in the top mode Standard Model. Quadratic divergences appear at each order 1/ N c since fermionic and bosonic contributions are of different order 1/ N c . It is shown that the full dynamical system to all orders in 1/ N c admits a solution, where the sum of all quadratic divergent contributions disappears.

Quadratic divergence cancellation in the top condensation model

Quadratic divergence cancellation in the top condensation model

LEP data, cancellation of quadratic divergences and new physics

Combined data from the LEP experiments are used to analyze the minimal standard model of electroweak interactions augmented by the request of cancellation of the quadratic divergences at the one loop level. Possible bounds on the Higgs boson mass are discussed. It is pointed out however and shown with few examples that new physics could affect the cancellation already at the one loop level, substantially altering these bounds without largely modifying the prediction form t .

Does the cancellation of quadratic divergences imply supersymmetry?

We consider a large class of renormalizable field theories containing scalar particles and look for relations among the various coupling constants such that the one-loop contributions to the quadratic divergence for each scalar cancel. With the severe restriction that any such relation be invariant under the renormalization group, we show in all cases considered that whenever such relations exist, they are those of a supersymmetric theory. Non-Abelian and Abelian gauge theories as well as Yukawa theories are treated.

On the uniqueness of supersymmetry for the cancellation of quadratic divergences

We show in a large class of renormalizable quantum field theories that if there occurs a cancellation of quadratic divergences for each independent scalar-boson mass, then the only interaction structure allowed is that of supersymmetry.

Massive superspace — A superspace with massive scalars and gauginos

We introduce a superspace whose global metric is modified in the fermionic sector and hence does not have the canonical supersymmetry. This introduces masses for physical scalar particles and gauginos with their superpartners remaining massless. Cancellation of quadratic divergences among fermion and boson loops is exhibited at one-loop level.

Cancellation of quadratic divergences and uniqueness of softly broken supersymmetry

Supersymmetric theories are known to be free from quadratic divergences. We investigate the inverse question whether the absence of quadratic divergences implies supersymmetry uniquely in theories of one Majorana field and a set of scalars and/or pseudoscalar fields. Relations among coupling constants derived from the requirement of no quadratic divergences up to two-loop order in the loop expansion lead uniquely to the softly broken supersymmetric theories in cases of two or less spin-0 fields.