Light scalars from a compact fifth dimension

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Besides the Higgs particle discovered in 2012, with mass 125 GeV, recent LHC data show tentative signals for new resonances in diboson as well as diphoton searches at high center-of-mass energies (2 TeV and 750 GeV, respectively). If these signals are confirmed (or other new resonances are discovered at the TeV scale), the large hierarchies between masses of new bosons require a dynamical explanation. Motivated by these tentative signals of new physics, we investigate the theoretical possibility that large hierarchies in the masses of glueballs could arise dynamically in new strongly-coupled gauge theories extending the standard model of particle physics. We study lattice data on non-Abelian gauge theories in the (near-)conformal regime as well as a simple toy model in the context of gauge/gravity dualities. We focus our attention on the ratio R between the mass of the lightest spin-2 and spin-0 resonances, that for technical reasons is a particularly convenient and clean observable to study. For models in which (non-perturbative) large anomalous dimensions arise dynamically, we show indications that this mass ratio can be large, with R > 5. Moreover, our results suggest that R might be related to universal properties of the IR fixed point. Our findings provide an interesting step towards understanding large mass ratios in the non-perturbative regime of quantum field theories with (near) IR conformal behaviour.

Section: Jhep06(2016)114mentioning

confidence: 99%

Section: A String-inspired Toy Model and The Dual Mass Spectrummentioning

confidence: 99%

Section: Jhep06(2016)114mentioning

confidence: 99%

“…The physical results do not depend on the spurious regulators r i . The boundary conditions are [65] …”

Section: Jhep06(2016)114mentioning

confidence: 99%

See 2 more Smart Citations

Large mass hierarchies from strongly-coupled dynamics

Athenodorou

Bennett

Bergner

et al. 2016

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“…3) 5) where the denotes derivative with respect to the radial direction r, V a = G ab ∂V /∂Φ b , and G a bc is the σ-model connection (we follow the conventions of [106]). …”

Section: Five-dimensional σ-Modelmentioning

confidence: 99%

Multiscale confining dynamics from holographic RG flows

Elander

Faedo

Hoyos

et al. 2014

Self Cite

108

We consider renormalization group flows between conformal field theories in five (six) dimensions with a string (M-theory) dual. By compactifying on a circle (torus) with appropriate boundary conditions, we obtain continuous families of confining fourdimensional theories parametrized by the ratio Λ flow /Λ QCD , with Λ flow the scale at which the flow between fixed points takes place and Λ QCD the confinement scale. We construct the dual geometries explicitly and compute the spectrum of scalar bound states (glueballs). We find a 'universal' subset of states common to all the models. We comment on the modifications of these models, and the corresponding fine-tuning, required for a parametrically light 'dilaton' state to be present. We also comment on some aspects of these theories as probed by extended objects such as strings and branes.

Pseudoscalar glueballs in the Klebanov-Strassler theory

Melnikov

Filho

2021

In this paper we describe a pseudoscalar subsector of the Klebanov-Strassler model. This subsector completes the holographic reconstruction of the spectrum of the lowest-lying glueball states, which are singlet under the global symmetry group SU(2) × SU(2). We derive the linearized supergravity equations for the pseudoscalar fluctuations and analyze their spectrum. The system of equations is shown to be compatible with six eigenmodes, as expected from supersymmetry. Our numerical analysis allows to reliably extract four of the corresponding towers. Their values match well the eigenvalues of the 0++ scalar states known from an earlier work. Assuming the masses of 0++ as a reference, we compare the lightest states of the holographic spectrum with lattice calculations in the quenched QCD at Nc = 3 and Nc = ∞.