Axion Coupling Research Articles

Determination of αs and the nucleon spin decomposition using recent polarized structure function data

New data on polarized μ− p and e− p scattering permit a first determination of α s using the Bjorken sum rule, as well as higher precision in determining the nucleon spin decomposition. Using perturbative QCD calculations to ▪ for the non-singlet combination of structure functions, we find α s (2.5 GeV 2) = 0.375 −0.081 +0.062, corresponding to α s ( M Z 2) = 0.122 −0.009 +0.005, and using calculations to ▪ for the singlet combination we find Δu = 0.83 ± 0.03, Δd = −0.43 ± 0.03, Δs = −0.10±0.03, ΔΣ  Δu + Δd + Δs = 0.31 ± 0.07, at a renormalization scale Q 2 = 10 GeV 2. Perturbative QCD corrections play an essential role in reconciling the interpretations of data taken using different targets. We discuss systematic uncertainties in the above numbers, which are dominated by higher-twist effects and lead, we estimate, to α s ( M Z 2) = 0.118 −0.014 +0.007. The Δ q determinations are used to update predictions for the couplings of massive Cold Dark Matter particles and axions to nucleons.

Astrophysical consequences of the existence of goldstone bosons

Abstract We suggest routine astronomical methods of searching for light Goldstone bosons (arions) including massless arions. The basic idea is to use the conversion of photons into low-mass bosons in the magnetic fields of compact stars and also of interstellar and intergalactic media. This process depends strongly on the polarization state of a photon and may produce a noticeable amount of linear polarization. Polarimetric observations may give strong constraints on the axion masses and the axion coupling constant. The best candidates for the observations are core-emission pulsars, low-mass X-ray binaries, magnetic white dwarfs including AM Her type objects. For the interstellar medium, this effect can be comparable with the interstellar polarization. X-ray fluxes from quasars and AGNs may oscillate with the cosmological redshift z due to the conversion of X-ray photons into arions.

One-loop threshold correction to the coupling of the antisymmetric tensor field and the Chern-Simons term in string theory.

By using the string background field method, we explicitly calculate the one-loop threshold correction to the coupling between the space-time antisymmetric tensor field and gauge Chern-Simons term. The related correction to the four-dimensional space-time axion coupling is discussed. The effect of gravitational and antisymmetric tensor fields on the gauge coupling constant is also considered.

Axion couplings and effective cut-offs in superstring compactifications

We use the linear supermultiplet formalism of supergravity to study axion couplings and chiral anomalies in the context of field-theoretical lagrangians describing orbifold compactifications beyond the classical approximation. By matching amplitudes computed in the effective low-energy theory with the results of string loop calculations we determine the appropriate counterterm in this effective theory that assures modular invariance to all loop order. We use supersymmetry consistency constraints to identify the correct ultraviolet cut-offs for the effective low-energy theory. Our results have a simple interpretation in terms of two-loop unification of gauge coupling constants at the string scale.

Particle accelerators as axion telescopes

We point out that the magnets and evacuated beampipes present in currently-existing particle accelerators could be used to from the basic components of an axion telescope. Concentrating on LEP it is shown that good terrestrial limits on the axion coupling to photons could be obtained in this way. It is noted that the beampipe at two of the LEP interaction points is oriented in such a way that alignments with the solar core occur relatively frequenyly. Precise predictions for all such alignments from the present until 2002 are given.

Axion decay in a strong magnetic field and radio fluxes from magnetic white dwarfs

Radio emission of isolated magnetic white dwarfs due to invisible axions decay in a strong magnetic field is estimated. It is possible to reach theoretical limits on the abundance and coupling of cosmic axions provided that radiofluxes would be observed at the level ≲ 1 μJy.

Results of a laboratory search for cosmic axions and other weakly coupled light particles.

A microwave cavity experiment designed to search for the signal from cosmic axions converting in an external magnetic field covered the mass range (4.5-16.3)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$ eV, corresponding to the frequency range from 1.09 to 3.93 GHz. Upper limits on the coupling and abundance of nonrelativistic galactic axions have been measured; these limits yield a coupling which is 1-2 orders of magnitude higher than that predicted by the Dine-Fischler-Srednicki model. Also presented are limits on axions with a continuum spectrum, limits on the presence of a wide axion line at the frequency of the 21-cm hydrogen emission line, and limits on the production of pseudoscalar particles by photons in the cavity interacting with the magnetic field.

Low-energy interactions of scalar and pseudoscalar Higgs bosons with baryons

It is pointed out that a fit to the baryon-octet mass spectrum to the first order of SU (3) breaking indicates unambiguously substantial sea-quark content in the baryon at rest. Owing to the presence of sizeable strange quark-antiquark pairs in the nucleon as implied by the pion-nucleon sigma term, the effective low-energy scalar Higgs-nucleon coupling gφNN ≈ 2.2. × 10−3 is dominated by strange quarks rather than by heavy quarks. The couplings gφσσ and gφξξ are estimated to be 3.2 × 10−3 and 3.7 × 10−3, respectively. Supplemented by the 1/Nc expansion (Nc being the number of colors) and by recent EMC measurement on the proton polarized structure functions, the coupling of the pseudoscalar Higgs boson to nucleons is fixed. A discussion of axion couplings is given.

Search for light bosons via the Mössbauer effect

We consider the possible existence of neutral bosons feebly coupled to nuclear matter, and of mass smaller than a few tens of keV. To search for them, we discuss the possibility of shielding a relatively large Mössbauer source against its conventional activity, and are looking for new types of penetrating monochromatic radiation that would resonantly excite the same Mössbauer transition in an outside detector. This type of experiment could improve the upper limits on the coupling of axions to hadrons well beyond their present laboratory values; to compete with all astrophysical constraints on axion is harder. In the search for other hypothetical particles, such as gauge bosons coupled to the baryon current, and in a mass range eight orders of magnitude upwards of m≈2 × 10 −4eV, our proposed technique has no known terrestrial or celestial competitor.

Enlarged Peccei-Quinn symmetry and limits from the supernova

We construct a model generalizing the invisible axion model of Dine, Fischler and Srednicki to three scalar doublets and two scalar singlets. By imposing two U(1) symmetries rather than the single Peccei-Quinn symmetry of the DFS model, we arrive at a physical particle spectrum containing both a light axion and a massless Goldstone boson. The axion couplings are as usual suppressed by a large VEV, which is bounded below by SN1987a emission limits and above by cosmological arguments. The VEV in the Goldstone boson couplings is bounded below by SN1987a emission and subsequent conversion into gamma rays via the galactic magnetic field, but the cosmological upper bound cannot be applied to this massless boson.

A cosmologically acceptable hadronic axion in a superstring-inspired model

A cosmologically acceptable harmless hadronic axion is generated in a superstring-inspired model with an intermediate mass scale, through the heavy-quark mechanism. The heavy quarks required to implement this scheme are naturally identified with the exoticD fields contained in the fundamental representations of the gauge groupE6. The axion couplings with ordinary matter are discussed.

A new detector scheme for axions

The coupling of axion to electron in atomic and molecular M1 or O − transitions is proposed to be used for the axion production by using a powerful maser/laser device. For their detection a resonance cavity tuned on the same frequency might well improve drastically the overall sensitivity.

Astrophysical constraints on axion and Majoron couplings.

We discuss in detail photon propagation within a medium. The results are then used to calculate the cross section of the photoproduction of pseudoscalars within the stellar medium in the most general case when the pseudoscalar has an appreciable mass and the photon is also massive due to matter effects. We discuss the Compton-type and the Primakoff-type processes, including the interference of them. Finally, we use the cross section to estimate the solar energy leakage due to axions. This produces bounds on the axion parameters which are discussed.

Constraints on axions from SN 1987A

We argue that the detection of neutrinos from SN 1987A implies that axion emission from the collapsing star must not have been significant. The best axion supernova limits come from nucleon bremsstrahlung processes which involve axion-quark couplings rather than the electron or photon couplings used in obtaining axion limits from red giants. The axion-quark couplings are less sensitive to specific axion model parameters and therefore are capable of yielding a model independent lower bound on ƒ rma . Quantitatively this yields an axion coupling limit of ƒ a ⪷ 8 × 10 11 GeV (or equivalently m a ⪷ 9 × 10 −5 eV ). This approaches the upper bound on ƒ a ⪷ 4 × 10 12 GeV from cosmological density arguments. While the bounds do not exclude the axion, if the axion exists, it must dominate the cosmological mass density. This same argument can also be applied to analogous couplings for any particle with m⪷50 MeV .

Limits on the abundance and coupling of cosmic axions at 4.5

We report preliminary results from a search for galactic axions in the frequency range 1.09${f}_{a}$1.22 GHz. For an axion linewidth ${\ensuremath{\Gamma}}_{a}$\ensuremath{\le}200 Hz we obtain the experimental limit (${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$/${m}_{a}$${)}^{2}$${\ensuremath{\rho}}_{a}$1.4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}41}$. The theoretical prediction is (${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$/${m}_{a}$${)}^{2}$${\ensuremath{\rho}}_{a}$=3.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}44}$ with ${\ensuremath{\rho}}_{a}$=300 MeV/${\mathrm{cm}}^{3}$. We have also searched for the presence of a continuous spectrum of light pseudoscalar particles; if we assume that the above ${\ensuremath{\rho}}_{a}$ is contained between the upper and lower frequencies of our search, then we find that ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}30}$ ${\mathrm{MeV}}^{1/2}$ ${\mathrm{cm}}^{3/2}$\ensuremath{\simeq}${10}^{\mathrm{\ensuremath{-}}11}$ ${\mathrm{GeV}}^{\mathrm{\ensuremath{-}}1}$.

Some quantum corrections to Calabi-Yau compactification.

The counterterms constructed by Green and Schwarz in the field-theory limit of superstrings are put into a form of Calabi-Yau compactification. Dimension-six operators are explicitly extracted. The modifications of the gauge kinetic terms and of the K\"ahler potential are obtained. Axion couplings and some $\mathrm{CP}$-nonconserving interactions are given.

Low-energy remnants of superstring anomaly cancellation terms

The local one-loop terms which cancel anomalies in superstring theories are known to lead to axion- FF̃ couplings after truncation to four dimensions. The supersymmetrization of these four-dimensional axion couplings seems to imply the existence of further (both bosonic and fermionic) D = 10 local terms, supersymmetric counterparts of the “Wess-Zumino” terms. The truncation to four dimensions of these extra terms leads to modifications of the tree-level truncated N = 1 supergravity lagrangian. The form of the modified Kähler potential is extracted as well as gauge functions of the low-energy theory. Phenomenological conclusions extracted from the tree-level truncation get modified. In particular gaugino masses M≅(2π) −5m 3 2 do appear.

Astrophysical constraints on the couplings of axions, majorons, and familons.

The spontaneous breaking of a global symmetry leads to the existence of Nambu-Goldstone bosons which, through their coupling to electrons and/or photons, can transport energy from the cores of stars and affect significantly the course of stellar evolution. We find by following in detail the evolution of stars that if the couplings to electrons and/or photons is too strong, helium never ignites---in contradiction with the observational evidence. Our limits restrict the axion mass to less than 0.01 eV, the familon breaking scale to >7\ifmmode\times\else\texttimes\fi{}${10}^{9}$ Gev, and the triplet majoron vacuum expectation value to <9 keV.

Axion couplings to matter: (I). CP-conserving parts

The CP-conserving couplings of axions to photons, electrons, and nucleons are derived for an arbitrary axion model. The relevance of the results to proposed axion search experiments is briefly discussed.

Search for axions in specific nuclear gamma-transitions at a power reactor

A search for axions was performed at a 2.8 GWth light-water power reactor by investigating in particular their production in specific nuclear transitions. Limits for the product (axion coupling) · (decay width) are derived, ruling out axions as described in the standard model.