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Research area 02 - PHYSICS AND SPACE SCIENCES, 02-101 - Physics of elementary particles

Keywordsparticle physics beyond the Standard Model, axion, high-energy astrophysics, dark matter, CP violation in strong interactions

Annotation
The project is aimed at refining theoretical models of physics beyond the Standard Model, related to axions and similar new light particles, at constraining their parameters from results of astronomical observations. Such particles were proposed for solving the CP problem of strong interactions and for explaining dark matter, so that the project tasks have the potential to solve key unresolved problems in particle physics, or to exclude a wide class of approaches to them. In recent years (2014-2017), a number of indications of the existence of an axion-like particle with particular values of parameters have been obtained, in particular in the works of the project leader. On the other hand, new ideas and approaches have appeared that make it possible to significantly expand the range of parameters of axion-like particles for which they can solve a strong CP problem and/or be candidates for the role of dark-matter particles. At the same time, the intensive accumulation and public availability of the data from astronomical observations, in particular those of the orbital gamma-ray telescope Fermi LAT, opens the possibility of radically new advances in limiting the properties of new particles from astrophysical observations. Within the framework of the project, we will propose and apply new methods of searching for axions and other light particles based on astrophysical information related to a wide variety of objects (the Sun, stars - including pulsars and magnetars, - active galactic nuclei and intergalactic space at the scale of the Universe as a whole). It is proposed to carry out a series of theoretical studies related to the astrophysical manifestations of such particles, aimed ultimately either to the confident detection of new particles, or to a significant limitation of their parameter space.

Expected results
1. The allowed region of the values of the intensity of extragalactic background radiation as a function of its frequency, limited from the requirement of absence of unphysical distance-dependent breaks in the spectra of the blazars. 2. Detection or limitation of galactic anisotropy in the absorption of gamma radiation from remote sources on the basis of a complete sample of sources. 3. Conclusion on the possibility of matching the increased intensity of extragalactic background radiation, which follows from the direct observations of 2017, with theoretical models. 4. Conclusion on the magnitude of the allowed contribution of an astrophysically motivated axion-like particle to the density of dark matter. 5. The range of parameters of ultralight dark matter allowed by today's data from astronomical observations; suggestions for future observations. 6. Refinement of restrictions on the parameters of an axion-like particle obtained from the absence of irregularities in the spectra of gamma-ray sources, taking into account the estimation of the systematic uncertainty of the method. 7. Constraints on the parameters of an axion-like particle from the study of polarization of pulsar radiation. 8. Proposals on optimization of TASTE and IAXO experiments for searching astrophysically-motivated axion-like particles. Suggestions for future experiments. 9. A model in which an astrophysically motivated axion-like particle would solve the strong CP problem, or exclusion of a wide class of such theories. Expected results will correspond to the world level, and in some cases even determine it. Axion-like particles were proposed for solving the CP problem of strong interactions and for explaining dark matter, so that the project tasks have the potential to solve key unresolved problems in particle physics, or to exclude a wide class of approaches to them. On the other hand, these particles and their interactions have a significant influence on the propagation of photons and are therefore important for interpreting results of many astronomical observations.

Annotation of the results obtained in 2020
It was found that both blazars, demonstrating anomalously low absorption of gamma radiation with energies above 100 GeV, and BL Lac type objects, which correlate with ultrahigh-energy cosmic rays in the HiRes experiment data, are distributed across the sky anisotropically and similarly - they are all observed through regions of increased density of galaxies in the Local Filament of large-scale structure of the Universe. The statistical significance of the difference from isotropy is 4.0 standard deviations after taking into account all penalty factors. This observation is in agreement with the scenario of mixing photons with an axion-like particle with a mass of about 1 neV and a coupling constant with photons of about 10^(-11) 1/GeV. The method of constraining parameters of axion-like particles from the analysis of the spectrum of thermal radiation of neutron stars was developed and applied; constraints on parameters from the spectrum of an isolated neutron star RX J1856.5-3754 are obtained. It is shown that the accuracy of measuring the spectra of cosmic gamma-ray bursts at very high energies is still insufficient for reliable tests of the hypothesis of anomalous transparency of the Universe for gamma radiation associated with axion-photon mixing. Moreover, all three gamma-ray bursts recorded in this range, as well as anomalous blazars, are visible in the direction along the Local Filament. In the data of the Carpet-2 experiment at the Baksan Neutrino Observatory of INR RAS, indications of an excess of photon-like events with energies above 100 TeV from the direction of Mrk 421 were found. If confirmed, this observation would give an unambiguous evidence in favor of yet unaccounted for effects in the propagation of high-energy photons in the Universe. It is shown that an axion-like particle with astrophysically motivated parameters can solve the CP-problem of strong interactions if it is a component of a more complex theory in which the "see-saw mechanism" is realized for axion-like particles. A new type of experiment is proposed for laboratory search for axion-like particles, in which the axion field is generated due to nonlinear interaction in a superconducting radio-frequency cavity without a magnetic field, and the reverse conversion occurs in an isolated detector cavity. The use of different pump modes in such an experiment will make it possible to search for axions of different masses without changing the cavity configuration. The sensitivity of such an experiment is estimated in terms of the space of parameters of axion-like particles. Based on the study of modern data on the large-scale structure of the Universe, it is shown that the models of "early dark energy", in which at the stage of approximate equality of the energy densities of matter and radiation in the early Universe, about 10% of the energy density is contained in the field describing axion-like particles, cannot simultaneously satisfy cosmological constraints and resolve the “Hubble crisis”, that is, eliminate the statistically significant difference between the measurements of the Hubble constant based on observational data from the early and late Universe.

Publications

1. A. Korochkin, A. Neronov, D. Semikoz Search for decaying eV-mass axion-like particles using gamma-ray signal from blazars JCAP, 03, 064 (year - 2020) https://doi.org/10.1088/1475-7516/2020/03/064

2. D.D. Dzhappuev,... S.V. Troitsky,... K.V. Zhuravleva Carpet results on astrophysical gamma rays above 100 TeV Proceedings of Science, PoS ICRC2019 (2020) 808 (year - 2020)

3. Dmitry Salnikov, Petr Satunin, D. V. Kirpichnikov, Maxim Fitkevich Examining axion-like particles with superconducting radio-frequency cavity JHEP (submitted), - (year - 2021)

4. Maxim Libanov, Sergey Troitsky On the impact of magnetic-field models in galaxy clusters on constraints on axion-like particles from the lack of irregularities in high-energy spectra of astrophysical sources Physics Letters B, Volume 802, 135252 (year - 2020) https://doi.org/10.1016/j.physletb.2020.135252

5. Mikhail M. Ivanov, Evan McDonough, J. Colin Hill, Marko Simonović, Michael W. Toomey Constraining Early Dark Energy with Large-Scale Structure Physical Review D, 102, 10, 103502 (year - 2020) https://doi.org/10.1103/PhysRevD.102.103502

6. Sergey Troitsky The local-filament pattern in the anomalous transparency of the Universe for energetic gamma rays Eur. Phys. J. C (submitted), - (year - 2021)

Annotation of the results obtained in 2018
Based on the latest observational data, taking into account rigorous criteria for the reliability of redshifts, new models of extragalactic background radiation, using improved analysis methods, we confirmed the effect of anomalous transparency of the Universe for high-energy gamma radiation, indicating the influence of an axion-like particle (significance of 4.5 standard deviations). A model of extragalactic background radiation was constructed, the use of which could lead to a decrease in the significance of the effect of anomalous transparency to 2 standard deviations. It was shown, however, that such a model would imply significant differences in the number of astrophysical parameters affecting the radiation intensity from the values obtained from other observations. A new method of constraining, on the basis of astronomical observations, the parameters of axion-like particles constituting ultra-light dark matter has been proposed and applied. Restrictions on the two-photon coupling constant of ultra-light dark-matter axion-like particles have been obtained obtained at the level of <~10^(-12) inverse GeV for particle masses between ~5*10^(-23) eV and ~1.2*10^(-21) eV. Proposals for further development and application of the method have been formulated. Proposals have been made for the Troitsk Axion Solar Telescope (TASTE) team for refining the scientific program and experiment optimization, which are reflected in the application for funding for this new experimental project. The published results are available at http://arxiv.org/abs/arXiv:1810.03443, https://arxiv.org/abs/1811.10997.

Publications

1. Alexander Korochkin, Grigory Rubtsov, Sergey Troitsky Search for anomalous features in gamma-ray blazar spectra corrected for the absorption on the extragalactic background light Journal of Cosmology and Astroparticle Physics, JCAP 1912 (2019) 002 (DOI: 10.1088/1475-7516/2019/12/002) (year - 2019) https://doi.org/10.1088/1475-7516/2019/12/002

2. M.M. Ivanov, Y.Y. Kovalev, M.L. Lister, A.G. Panin, A.B. Pushkarev, T. Savolainen, S.V. Troitsky Constraining the photon coupling of ultra-light dark-matter axion-like particles by polarization variations of parsec-scale jets in active galaxies Journal of Cosmology and Astroparticle Physics, JCAP 1902 (2019) 059 (DOI: 10.1088/1475-7516/2019/02/059) (year - 2019) https://doi.org/10.1088/1475-7516/2019/02/059

3. - В джетах активных галактик не нашли темной материи Индикатор, - (year - )

Annotation of the results obtained in 2019
Based on the sample of blazars with known redshifts, observed in gamma rays at energies for which the optical depth with respect to the pair production on extragalactic background light exceeds unity, an indication to anisotropy of this gamma-ray absorption is found. It is demonstrated that previously used expressions, relating parameters of ultralight dark-matter axion-like particle and polarization properties of radiation passing through the condensate of these particles, are exact to all orders of perturbation theory. As a consequence, the absence of light bending on axion dark-matter clumps is demonstrated. It is shown that measurements of extragalactic background radiation in the micrometer band by CIBER (2017) disagree with a theoretical model, which sums up the radiation from known astrophysical sources. This indicates to the existence of a new, not accounted for in the model, component of the background radiation. Constraints on localized in frequency additional components of the background radiation are obtained from the analysis of gamma-ray blazar spectra. It is shown that such additional component, explaining the CIBER measurement, does not contradict to these constraints. Constraints on the mass and photon coupling of dark-matter axion-like particles are obtained and the range of these parameters, explaining the CIBER observation, is found. This region of the parameter space corresponds to the experimentally allowed axion-like dark-matter particle which may serve as the quantum-chromodynamics axion. It is demonstrated that the contribution to the dark-matter density of the axion-like particle with parameters motivated by explanations of anomalies in the transparency of the Universe for gamma radiation, energy losses of horizontal-branch stars, white-dwarf and neutron-star cooling is negligible in most models. It is demonstrated that systematic uncertainties of the method to constrain parameters of axion-like particles from irregularities in spectra of astrophysical sources, related to modeling of the magnetic field, reach two orders of magnitude, which makes constraints obtained previously by this method irrelevant. Future studies of this kind will have to use sources with well-known magnetic fields around them.

Publications

1. Blas D., Caputo A., Ivanov M.M., Sberna L. No chiral light bending by clumps of axion-like particles Physics of the Dark Universe, Physics of the Dark Universe 27С (2020) 100428 (year - 2020) https://doi.org/10.1016/j.dark.2019.100428

2. Korochkin A.A., Neronov A., Semikoz D. Search for spectral features in extragalactic background light with gamma-ray telescopes Astronomy and Astrophyscs, - (year - 2019) https://doi.org/10.1051/0004-6361/201936262