T. Geralis
A5016655117- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Particle Detector Development and Performance
- Dark Matter and Cosmic Phenomena
- Computational Physics and Python Applications
- Cosmology and Gravitation Theories
- Neutrino Physics Research
- Astrophysics and Cosmic Phenomena
- Atomic and Subatomic Physics Research
- Medical Imaging Techniques and Applications
- Radiation Detection and Scintillator Technologies
- Black Holes and Theoretical Physics
- Distributed and Parallel Computing Systems
- Particle Accelerators and Free-Electron Lasers
- Astronomy and Astrophysical Research
- Advanced Data Storage Technologies
- Solar and Space Plasma Dynamics
- Gamma-ray bursts and supernovae
- Nuclear physics research studies
- Big Data Technologies and Applications
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Superconducting Materials and Applications
- Muon and positron interactions and applications
National Centre of Scientific Research "Demokritos"
2016-2025
Rutherford Appleton Laboratory
1994-2024
New York University
2024
A. Alikhanyan National Laboratory
2014-2024
SR Research (Canada)
2024
Federación Española de Enfermedades Raras
2024
Atlas Scientific (United States)
2024
Institute of Nuclear and Particle Physics
2014-2023
Institute of High Energy Physics
2013-2023
The University of Adelaide
2019-2023
Hypothetical low-mass particles, such as axions, provide a compelling explanation for the dark matter in universe. Such particles are expected to emerge abundantly from hot interior of stars. To test this prediction, CERN Axion Solar Telescope (CAST) uses 9 T refurbished Large Hadron Collider magnet directed towards Sun. In strong magnetic field, solar axions can be converted X-ray photons which recorded by detectors. 2013–2015 run, thanks low-background detectors and new telescope,...
We have searched for solar axions or similar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup with improved conditions in all detectors. From absence of excess X-rays when magnet was pointing Sun, we set an upper limit on axion-photon coupling 8.8 x 10^{-11} GeV^{-1} at 95% CL m_a <~ 0.02 eV. This result is best experimental over a broad range axion masses and eV also supersedes previous derived from energy-loss arguments globular-cluster stars.
The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO look for axions or axion-like particles (ALPs) originating in the Sun via Primakoff conversion of solar plasma photons. In terms signal-to-noise ratio, about 4–5 orders magnitude more sensitive than CAST, currently most powerful helioscope, reaching sensitivity to axion-photon couplings down few × 10−12 GeV−1 and thus probing large fraction unexplored ALP parameter space....
Hypothetical axionlike particles with a two-photon interaction would be produced in the sun by Primakoff process. In laboratory magnetic field ("axion helioscope"), they transformed into x-rays energies of few keV. Using decommissioned Large Hadron Collider test magnet, CERN Axion Solar Telescope ran for about 6 months during 2003. The first results from analysis these data are presented here. No signal above background was observed, implying an upper limit to axion-photon coupling...
We have searched for solar axions or other pseudoscalar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup. Whereas we previously reported results from CAST with evacuated magnet bores (Phase I), setting limits on lower mass axions, here report where were filled 4He gas II) of variable pressure. The introduction generates a refractive photon mγ, thereby achieving maximum possible conversion rate those axion masses ma match mγ. With 160 different...
The CERN Axion Solar Telescope (CAST) has extended its search for solar axions by using 3He as a buffer gas. At T=1.8 K this allows larger pressure settings and hence sensitivity to higher axion masses than our previous measurements with 4He. With about 1 h of data taking at each 252 different we have scanned the mass range 0.39 eV < m_a 0.64 eV. From absence excess X-rays when magnet was pointing Sun set typical upper limit on axion-photon coupling g_ag 2.3 x 10^{-10} GeV^{-1} 95% CL, exact...
We study the feasibility of a new generation axion helioscope, most ambitious and promising detector solar axions to date. show that large improvements in magnetic field volume, x-ray focusing optics backgrounds are possible beyond those achieved CERN Axion Solar Telescope (CAST). For hadronic models, sensitivity axion-photon coupling gaγ ≳ few × 10−12 GeV−1 is conceivable, 1–1.5 orders magnitude CAST sensitivity. If also couple electrons, Sun produces larger flux for same value Peccei-Quinn...
The CERN Axion Solar Telescope has finished its search for solar axions with (3)He buffer gas, covering the range 0.64 eV ≲ ma 1.17 eV. This closes gap to cosmological hot dark matter limit and actually overlaps it. From absence of excess x rays when magnet was pointing Sun we set a typical upper on axion-photon coupling gaγ 3.3 × 10(-10) GeV(-1) at 95% C.L., exact value depending pressure setting. Future direct axion searches will focus increasing sensitivity smaller values gaγ, example by...
In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces strong flux by bremsstrahlung, Compton scattering, and axio-recombination, ``BCA processes.'' Based on new calculation of this flux, including for first time we derive limits Yukawa coupling gae axion-photon interaction strength gaγ using CAST phase-I data (vacuum phase). For ma≲10 meV/c2 find < 8.1 × 10−23 GeV−1 at 95% CL. We stress that next-generation helioscope such as proposed IAXO could...
The CERN Axion Solar Telescope (CAST) searches for $a\ensuremath{\rightarrow}\ensuremath{\gamma}$ conversion in the 9 T magnetic field of a refurbished LHC test magnet that can be directed toward Sun. Two parallel bores filled with helium adjustable pressure to match x-ray refractive mass ${m}_{\ensuremath{\gamma}}$ axion search ${m}_{a}$. After vacuum phase (2003--2004), which is optimal ${m}_{a}\ensuremath{\lesssim}0.02\text{ }\text{ }\mathrm{eV}$, we used $^{4}\mathrm{He}$ 2005--2007...
A low-background Micromegas detector has been operating in the CAST experiment at CERN for search solar axions during first phase of (2002–2004). The detector, made out low radioactivity materials, operated efficiently and achieved a very high level background rejection (5 × 10−5 counts keV−1 cm−2 s−1) without shielding.
We have searched for 14.4 keV solar axions or more general axion-like particles (ALPs), that may be emitted in the M1 nuclear transition of 57Fe, by using axion-to-photon conversion CERN Axion Solar Telescope (CAST) with evacuated magnet bores (Phase I). From absence excess monoenergetic X-rays when was pointing to Sun, we set model-independent constraints on coupling constants pseudoscalar couple two photons and a nucleon gaγ|−1.19gaN0+gaN3| < 1.36 × 10−16 GeV−1 ma 0.03 eV at 95% confidence level.
In this work we present a search for (solar) chameleons with the CERN Axion Solar Telescope (CAST). This novel experimental technique, in field of dark energy research, exploits both chameleon coupling to matter (βm) and photons (βγ) via Primakoff effect. By reducing X-ray detection threshold used axions from 1 keV 400 eV CAST became sensitive converted solar spectrum which peaks around 600 eV. Even though have not observed any excess above background, can provide 95% C.L. limit strength...
Using radiative Z0→ τ+τ−γevents collected with the OPAL detector at LEP s=MZ during 1990–95, a direct study of electromagnetic current τγ vertex has been performed in terms anomalous magnetic form factor F2 τ lepton. The analysis is based on data sample 1429 e+e−→τ+τ−γevents which are examined for deviation from expectation F2=0. From non-observation τ+τ−γproduction limit of−0.068<F2<0.065is obtained. This can also be interpreted as electric dipole F3 as|eF3|<3.7×10−16ecm.The above ranges...
The International Axion Observatory (IAXO) is a next generation axion helioscope aiming at sensitivity to the axion-photon coupling of few 10^{-12} GeV^{-1}, i.e. 1-1.5 orders magnitude beyond sensitivities achieved by currently most sensitive helioscope, CERN Solar Telescope (CAST). Crucial factors in improving for IAXO are increase magnetic field volume together with extensive use x-ray focusing optics and low background detectors, innovations already successfully tested CAST....
Axion helioscopes aim at the detection of solar axions through their conversion into x-rays in laboratory magnetic fields. The use low background x-ray detectors is an essential component contributing to sensitivity these searches. Here we review recent advances on Micromegas used CERN Solar Telescope (CAST) and proposed for future International Observatory (IAXO). most setups CAST have achieved levels 1.5 × 10−6 keV−1 cm−2 s−1, a factor more than 100 lower ones obtained by first generation...