$\eta$ and $\eta'$ masses and decay constants from lattice QCD with $N_f=2+1+1$ quark flavours

Michael, Chris; Ottnad, Konstantin; Urbach, Carsten

doi:10.22323/1.187.0253

Cited by 3 publications

(3 citation statements)

References 41 publications

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“…The large mass of the η meson should come from the effects of the U A (1) axial anomaly and its related gauge field topology, both present in QCD. Despite the difficulty of computing the contribution of disconnected diagrams to the η correlator in lattice simulations, these obstacles have been overcome and lattice calculations [8][9][10] give a mass for the η meson compatible with its experimental value, and this can be seen as an indirect confirmation that the effects of the anomaly are present in the low temperature phase of QCD.…”

Section: Theoretical Biases Versus Numerical Resultsmentioning

confidence: 99%

Axial UA(1) Anomaly: A New Mechanism to Generate Massless Bosons

Azcoiti

2021

Symmetry

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Prior to the establishment of QCD as the correct theory describing hadronic physics, it was realized that the essential ingredients of the hadronic world at low energies are chiral symmetry and its spontaneous breaking. Spontaneous symmetry breaking is a non-perturbative phenomenon, and, thanks to massive QCD simulations on the lattice, we have at present a good understanding of the vacuum realization of the non-abelian chiral symmetry as a function of the physical temperature. As far as the UA(1) anomaly is concerned, and especially in the high temperature phase, the current situation is however far from satisfactory. The first part of this article is devoted to reviewing the present status of lattice calculations, in the high temperature phase of QCD, of quantities directly related to the UA(1) axial anomaly. In the second part, some recently suggested interesting physical implications of the UA(1) anomaly in systems where the non-abelian axial symmetry is fulfilled in the vacuum are analyzed. More precisely it is argued that, if the UA(1) symmetry remains effectively broken, the topological properties of the theory can be the basis of a mechanism, other than Goldstone’s theorem, to generate a rich spectrum of massless bosons at the chiral limit.

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Section: Theoretical Biases Versus Numerical Resultsmentioning

confidence: 99%

Axial UA(1) Anomaly: A New Mechanism to Generate Massless Bosons

Azcoiti

2021

Symmetry

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“…The large mass of the η ′ meson should come from the effects of the U A (1) axial anomaly and its related gauge field topology, both present in QCD. Despite the difficulty of computing the contribution of disconnected diagrams to the η ′ correlator in lattice simulations, these obstacles have been overcome and lattice calculations [8], [9], [10] give a mass for the η ′ meson compatible with its experimental value, and this can be seen as an indirect confirmation that the effects of the anomaly are present in the low temperature phase of QCD.…”

Section: Theoretical Biases Versus Numerical Resultsmentioning

confidence: 99%

Axial $U_A(1)$ Anomaly: a New Mechanism to Generate Massless Bosons

Azcoiti¹

2021

Preprint

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Prior to the establishment of QCD as the correct theory describing hadronic physics, it was realized that the essential ingredients of the hadronic world at low energies are chiral symmetry and its spontaneous breaking. Spontaneous symmetry breaking is a nonperturbative phenomenon and thanks to massive QCD simulations on the lattice we have at present a good understanding on the vacuum realization of the non-abelian chiral symmetry as a function of the physical temperature. As far as the U A (1) anomaly is concerned, and especially in the high temperature phase, the current situation is however far from satisfactory. The first part of this article is devoted to review the present status of lattice calculations, in the high temperature phase of QCD, of quantities directly related to the U A (1) axial anomaly. In the second part I will analyze some interesting physical implications of the U A (1) anomaly, recently suggested, in systems where the non-abelian axial symmetry is fulfilled in the vacuum. More precisely I will argue that, if the U A (1) symmetry remains effectively broken, the topological properties of the theory can be the basis of a mechanism, other than Goldstone's theorem, to generate a rich spectrum of massless bosons at the chiral limit.

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“…The η ′ meson is a special case; it is much heavier than the other pseudoscalar mesons due to the influence of the U(1) A anomaly. An example lattice QCD calculation of this state is [84]; they find weak dependence on the light-quark masses, similar to the η meson. The relation…”

Section: B Other Mesons and Baryonsmentioning

confidence: 97%

Repurposing lattice QCD results for composite phenomenology

DeGrand

Neil

2020

Phys. Rev. D

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A number of proposed extensions of the Standard Model include new strongly interacting dynamics, in the form of SU (N ) gauge fields coupled to various numbers of fermions. Often, these extensions allow N = 3 as a plausible choice, or even require N = 3, such as in twin Higgs models, where the new dynamics is a "copy" of QCD. However, the fermion masses in such a sector are typically different from (often heavier than) the ones of real-world QCD, relative to the confinement scale. Many of the strong interaction masses and matrix elements for SU (3) at heavy fermion masses have already been computed on the lattice, typically as a byproduct of the approach to the physical point of real QCD. We provide a summary of these relevant results for the phenomenological community.

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$\eta$ and $\eta'$ masses and decay constants from lattice QCD with $N_f=2+1+1$ quark flavours

Cited by 3 publications

References 41 publications

Axial UA(1) Anomaly: A New Mechanism to Generate Massless Bosons

Axial UA(1) Anomaly: A New Mechanism to Generate Massless Bosons

Axial $U_A(1)$ Anomaly: a New Mechanism to Generate Massless Bosons

Repurposing lattice QCD results for composite phenomenology

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