Dine–Fischler–Srednicki–Zhitnitsky model

Dine–Fischler–Srednicki–Zhitnitsky model
Name	Dine–Fischler–Srednicki–Zhitnitsky model
Other names	DFSZ model
Field	Particle physics
Introduced	1981
Creators	Howard Dine; Michael Fischler; Aaron Srednicki; Mikhail Zhitnitsky

Dine–Fischler–Srednicki–Zhitnitsky model is a theoretical construction in particle physics proposing an invisible axion arising from a spontaneously broken global Peccei–Quinn symmetry to solve the strong CP problem. The model embeds axion couplings within an extended Standard Model framework by introducing additional scalar fields and altered fermion charge assignments, yielding phenomenology distinct from the Kim–Shifman–Vainshtein–Zakharov model and informing searches by collaborations such as ADMX and CAST. The DFSZ construction has influenced constraints from observatories including Super-Kamiokande, Planck, and IceCube, and has motivated variants studied at institutions like CERN and SLAC National Accelerator Laboratory.

Introduction

The DFSZ proposal was published by Dine, Fischler, Srednicki, and Zhitnitsky in 1981 to realize an "invisible" axion within a two-Higgs-doublet extension of the Standard Model. It connects the Peccei–Quinn symmetry to Higgs-sector dynamics, modifying Yukawa interactions for fermions such as the electron, up quark, and down quark, while preserving anomaly cancellation conditions related to Quantum Chromodynamics. The model stands alongside the KSVZ model as a principal laboratory for axion phenomenology, informing experimental programs by collaborations including ADMX, CAST, and IAXO.

Model formulation

The DFSZ construction augments the Standard Model with a gauge-singlet complex scalar field S and two Higgs doublets H_u and H_d, assigning global Peccei–Quinn symmetry charges so that S carries the spontaneous-breaking vacuum expectation value f_a. Fermion Yukawa couplings involve H_u and H_d with charge assignments arranged for quark masses of the top quark, bottom quark, and strange quark while preserving electroweak symmetry breaking via the Higgs mechanism associated with the Higgs boson. The resulting pseudo-Nambu–Goldstone boson, the axion, couples to gluons through the QCD anomaly linked to instanton effects studied in analyses by Gerard 't Hooft and to photons via triangle diagrams analogous to those analyzed by Adler, Bell, and Jackiw. Model parameters include the Peccei–Quinn scale f_a, the ratio of Higgs vacuum expectation values tanβ familiar from supersymmetry literature, and mixing angles constrained by precision measurements from LEP and LHC experiments.

Axion phenomenology and properties

Axions in the DFSZ scenario acquire a mass m_a inversely proportional to f_a through nonperturbative Quantum Chromodynamics dynamics calculated using techniques related to the chiral perturbation theory approaches of Gasser–Leutwyler and lattice results from collaborations like the RBC and UKQCD groups. DFSZ axions couple to charged leptons such as the electron at tree level, leading to enhanced interactions relative to KSVZ-type axions and affecting processes measured in experiments like Borexino and XENONnT. Photon couplings in DFSZ are determined by model-dependent electromagnetic anomaly coefficients influencing conversion rates in magnetic fields probed by CAST and microwave-cavity searches by ADMX. Flavor physics constraints arise from rare decays studied by BaBar, Belle II, and LHCb through processes involving kaon and pion transitions sensitive to axion-mediated channels.

Cosmological and astrophysical implications

In cosmology, DFSZ axions contribute to cold dark matter production via the misalignment mechanism originally considered in contexts involving Andrei Linde and Paczynski-style analyses, with density estimates constrained by measurements from Planck and large-scale structure surveys like SDSS. If the Peccei–Quinn symmetry breaks after inflation, the model predicts axionic string and domain-wall networks examined in simulations by groups associated with Max Planck Institute for Physics and Kavli Institute for Cosmology, affecting relic densities and isocurvature perturbations constrained by WMAP and Planck. Stellar cooling bounds from Raffelt-style analyses using observations of SN 1987A, white dwarf pulsations studied by Kepler, and red-giant branch evolution in globular clusters observed by the Hubble Space Telescope place stringent limits on DFSZ axion couplings to electrons and photons. High-energy astrophysical observations from Fermi Gamma-ray Space Telescope and neutrino telescopes like IceCube probe indirect signatures through axion-photon conversion in magnetic fields of galaxies and clusters cataloged by surveys such as Sloan Digital Sky Survey.

Experimental constraints and searches

Laboratory constraints on DFSZ axions arise from helioscope experiments such as CAST and proposed missions like IAXO, haloscope campaigns including ADMX and HAYSTAC, and light-shining-through-wall experiments led by collaborations involving GRAAL and ALPS. Collider bounds stem from rare decay searches at LHCb, heavy-flavor factories like Belle II, and precision electroweak measurements at LEP and LHC detectors such as ATLAS and CMS. Stellar evolution constraints derive from analyses by Raffelt and observations of SN 1987A neutrino data collected by Kamiokande-II and IMB, while cosmological limits on relic abundance and isocurvature are informed by datasets from Planck and BOSS. Ongoing direct-detection efforts by collaborations like ADMX pursue parameter space motivated by DFSZ couplings, with complementary searches at low-energy facilities such as PSI and dedicated axion interferometry initiatives connected to research at MIT and University of Washington.

Variants and related models

Variants of the DFSZ framework include supersymmetric embeddings explored within Minimal Supersymmetric Standard Model-inspired setups and string-theoretic realizations considered by groups at Princeton University, Caltech, and Harvard University. Alternative invisible-axion constructions such as the KSVZ model and heavy-axion scenarios relate to DFSZ through differing fermion charge assignments and anomaly coefficients examined by theorists including Steven Weinberg and Frank Wilczek. Composite-axion models and clockwork/axion alignment mechanisms developed in recent years reference the DFSZ charge structures when mapping global-symmetry breaking patterns studied at Perimeter Institute and Institute for Advanced Study. Experimental proposals like IAXO and new haloscopes build upon DFSZ-motivated sensitivity targets set by collaborations at CERN and national laboratories including Fermilab.

Category:Beyond the Standard Model