Neutrinos, axions and conformal symmetry

Meissner, Krzysztof A.; Nicolai, Hermann

doi:10.1140/epjc/s10052-008-0760-x

Cited by 39 publications

(37 citation statements)

References 33 publications

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“…In this paper we consider the inclusion of right-chiral neutrinos into the SM and demonstrate that for non-trivial mixing between left-and right-chiral neutrinos the relevant triangle graphs with two external electroweak vector bosons no longer sum up to zero, as they would if only the (vanishing) (B − L) anomaly were taken into account. This result provides additional support for our previous proposal to identify the Majoron with the axion [3], and clarifies some issues that might be raised in connection with this proposal.…”

Section: Introductionsupporting

confidence: 84%

“…This is the simplest example for which one can establish the existence of anomaly-like terms in the expansion (3); these are entirely due to the mixing between left-chiral and right-chiral neutrinos. The computation thus complements our previous work [3] where we calculated various higher loop diagrams contributing to X using the Yukawa interaction rather than the matrix element of the (B − L) current. In particular we derived the anomaly-like coupling of the Majoron/axion to gluons at order 3 .…”

Section: Introductionsupporting

confidence: 66%

“…(13) below) the interaction is represented by a derivative coupling of the Goldstone field to the (B − L) current. The first 'picture' was extensively used in [3], whereas the calculation based on the second 'picture' adopted here closely resembles the usual anomaly computation. With both pictures, we obtain a finite deviation from the vanishing result expected on the basis of the vanishing (B −L) anomaly.…”

Section: Introductionmentioning

confidence: 99%

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(B–L) symmetry vs. neutrino seesaw

2013

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We compute the effective coupling of the Majoron to W bosons at O( ) by evaluating the matrix element of the (B − L) current between the vacuum and a W + W − state. The (B − L) anomaly vanishes, but the amplitude does not vanish as a result of a UV finite and non-local contribution which is entirely due to the mixing between left-chiral and right-chiral neutrinos. The result shows how anomaly-like couplings may arise in spite of the fact that the (B −L) current remains exactly conserved to all orders in , lending additional support to our previous proposal to identify the Majoron with the axion.

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Section: Introductionsupporting

confidence: 84%

Section: Introductionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

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(B–L) symmetry vs. neutrino seesaw

2013

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“…However, although there do exist perturbatively stable minima of the potential of this model giving rise to a Higgs mass equal to 125 GeV (as we have checked by carefully investigating the 2-loop effective potential of the model), the mixing with the second heavier spin-zero particle in all cases turned out too large to be in agreement with the LHC data. For this reason, and because of another serious drawback of this implementation (related to quadratic divergences, see below) we here propose a different way in which SBCS can be at work to solve the hierarchy problem, and show how this mechanism can be realized in the model [2,4] with explicit small mass parameters. We also note some similarities with the scheme proposed in [5] in the framework of the asymptotic safety program.…”

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confidence: 99%

Softly broken conformal symmetry and the stability of the electroweak scale

et al. 2015

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We point out a novel possible mechanism by which the electroweak hierarchy problem can be avoided in the (effective) quantum field theory. Assuming the existence of a UV complete underlying fundamental theory and treating the cutoff scale Λ of the effective field theory as a real physical scale we argue that the hierarchy problem would be solved if the coefficient in front of quadratic divergences vanished for some choice of Λ, and if the effective theory mass parameters fixed at Λ by the fundamental theory were hierarchically smaller than Λ itself. While this mechanism most probably cannot work in the Standard Model if the scale Λ is to be close to the Planck scale, we show that it can work in a minimal extension (Conformal Standard Model) proposed recently for a different implementation of soft conformal symmetry breaking.PACS numbers: 12.60. Fr,1480.Ec,14.80Va The problem of stability of the electroweak scale with respect to the Planck scale (the so-called hierarchy problem) has for almost 40 years been one of the main driving forces of theoretical research in high energy physics. Over the years various mechanisms for solving it at the effective quantum field theory level have been proposed and investigated in detail, of which the most notable are technicolor and low energy supersymmetry. With the discovery of a spin-zero particle at the LHC, and after establishing its basic characteristics, it has become clear that a solution which departs little from the simplest mechanism of the electroweak symmetry breaking realized in the Standard Model (SM) may be preferred. In particular, extensions of the SM which predict only elementary scalars and no new higher spin particles other than right-chiral neutrinos seem distinguished at present. It is therefore of interest that there exists an alternative way (which does not require new spin s ≥ 1 2 degrees of freedom) by which the problem of stability of the electroweak scale could be avoided in the low energy effective theory. It is based on a novel implementation of 'near conformal symmetry' in the effective low energy theory.As is well known, the classical conformal symmetry of the SM is spoiled only by the scalar field mass term necessary to induce phenomenologically viable electroweak symmetry breaking. Moreover, as in any generic quantum field theory, conformal symmetry of the SM is broken by quantum effects. Yet, the idea that 'softly broken conformal symmetry' (SBCS) might be relevant for the solution of the hierarchy problem was expressed already long ago [1]. As one possible concrete implementation of this idea a minimal extension of the SM, the Conformal Standard Model (CSM), has been proposed in [2]. Besides the known particles this model only involves the right-chiral neutrinos and one extra (complex) scalar field. Originally it was assumed that its conformal symmetry is broken only by the anomaly, inducing electroweak symmetry breaking via the Coleman-Weinberg mechanism [3]. However, although there do exist perturbatively stable minima of the potential o...

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“…The idea to utilize the CW mechanism to solve the hierarchy problem was first modelled by Meissner and Nicolai [7] (see also [9]). In addition to the SM particles, they introduced right-handed neutrinos and a SM singlet scalar Φ.…”

Section: B-l Extension Of the Sm With Flat Potential At Planckmentioning

confidence: 99%

What Can We Learn from the 126 GeV Higgs Boson for the Planck Scale Physics? - Hierarchy Problem and the Stability of the Vacuum -

Iso¹

2014

Strong Coupling Gauge Theories in the LHC Perspective (SCGT12)

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The discovery of the Higgs particle at around 126 GeV has given us a big hint towards the origin of the Higgs potential. The running quartic self-coupling decreases and crosses zero somewhere in the very high energy scale. It is usually considered as a signal of the instability of the standard model (SM) vacuum, but it can also indicate a link between the physics in the electroweak scale and the Planck scale. Furthermore, the LHC experiments as well as the flavor physics experiments give strong constraints on the physics beyond the SM. It urges us to reconsider the widely taken approach to the physics beyond the SM (BSM), namely the approach based on the gauge unification below the Planck scale and the resulting hierarchy problem. Motivated by the recent experiments, we first revisit the hierarchy problem and consider an alternative appoach based on a classical conformality of the SM without the Higgs mass term.In this talk, I review our recent proposal of a B-L extension of the SM with a flat Higgs potential at the Planck scale [1,2]. This model can be an alternative solution to the hierarchy problem as well as being phenomenologically viable to explain the neutrino oscillations and the baryon asymmetry of the universe. With an assumption that the Higgs has a flat potential at the Planck scale, we show that the B-L symmetry is radiatively broken at the TeV scale via the Coleman-Weinberg mechanism, and it triggers the electroweak symmetry breaking through a radiatively generated scalar mixing. The ratio of these two breaking scales is dynamically determined by the B-L gauge coupling. I. CENTRAL DOGMA OF PARTICLE PHYSICSIn the LHC era, we acquired various hints towards the physics beyond the SM. The first hint is of course the mass of the recently discovered Higgs-like particle. The value of 126 GeV is quite interesting because it is close to the boarder of the stability bound. Given the vev of the Higgs at 246 GeV, its mass gives an information of the curvature of the potential at the minimum. As the mass 126 GeV is smaller than 246 GeV, the Higgs potential is rather shallow and unstable against the radiative corrections. The (in)stability of the SM vacuum can be investigated explicitly by looking at the running bahaviour of the quartic coupling. The beta function of the quartic Higgs coupling λ H is given by

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Neutrinos, axions and conformal symmetry

Cited by 39 publications

References 33 publications

(B–L) symmetry vs. neutrino seesaw

(B–L) symmetry vs. neutrino seesaw

Softly broken conformal symmetry and the stability of the electroweak scale

What Can We Learn from the 126 GeV Higgs Boson for the Planck Scale Physics? - Hierarchy Problem and the Stability of the Vacuum -

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