K. Zioutas
A5054376927- Dark Matter and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Cosmology and Gravitation Theories
- Atomic and Subatomic Physics Research
- Astrophysics and Cosmic Phenomena
- Particle Detector Development and Performance
- Solar and Space Plasma Dynamics
- Nuclear physics research studies
- Quantum Chromodynamics and Particle Interactions
- Atomic and Molecular Physics
- Nuclear Physics and Applications
- Radiation Detection and Scintillator Technologies
- Space Science and Extraterrestrial Life
- Scientific Research and Discoveries
- Quantum, superfluid, helium dynamics
- X-ray Spectroscopy and Fluorescence Analysis
- Particle Accelerators and Free-Electron Lasers
- Stellar, planetary, and galactic studies
- Computational Physics and Python Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Radioactive Decay and Measurement Techniques
- Advanced Chemical Physics Studies
- Geophysics and Sensor Technology
- Distributed and Parallel Computing Systems
- Mass Spectrometry Techniques and Applications
University of Patras
2016-2025
European Organization for Nuclear Research
2013-2024
University of Freiburg
2018
University of Bonn
1970-2015
National Centre of Scientific Research "Demokritos"
2015
Technical University of Darmstadt
2003-2013
Occidental College
2005
Aristotle University of Thessaloniki
1989-2005
University of South Carolina
2000-2002
National and Kapodistrian University of Athens
2001
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...
A new experiment is described to detect a permanent electric dipole moment of the proton with sensitivity $10^{-29}e\cdot$cm by using polarized "magic" momentum $0.7$~GeV/c protons in an all-electric storage ring. Systematic errors relevant are discussed and techniques address them presented. The measurement sensitive physics beyond Standard Model at scale 3000~TeV.
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...
A bstract We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part CERN Solar Telescope (CAST), searching for axion dark matter in 34.67 μ eV mass range. radio frequency cavity consisting 5 sub-cavities coupled by inductive irises took physics data inside CAST dipole magnet first time using this filter-like haloscope geometry. An exclusion limit with 95% credibility level on axion-photon coupling constant g aγ ≳ 4 × 10 − 13 GeV 1 over range 34 ....
The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole magnet, has searched for axions in 19.74 $\mu$eV to 22.47 mass range. detection concept follows Sikivie haloscope principle, where Dark Matter convert into photons within a resonator immersed magnetic field. is an array of four individual rectangular cavities inserted strong phase-matched maximize sensitivity. Here we report on data acquired 4124 h from 2019 2021. Each cavity equipped with fast frequency tuning mechanism...
▪ Abstract The axion, a favored dark matter candidate, is expected to have very small mass and extraordinarily weak couplings. Although it has eluded discovery or exclusion for three decades, remains the most compelling solution strong-CP problem. Axions may be detected by their resonant conversion RF photons in microwave cavity permeated magnetic field. Experiments already set significant limits on axion's photon coupling; progress detection schemes at below standard quantum limit will soon...
Abstract We describe the experimental method and report results of electron emission from PLZT-2/95/5 ceramics subjected to rectangular HV pulses. The influence amplitude, gas pressure, temperature on beam current-density charge was investigated. kinetic energy estimated by applying a decelerating field. Emitted pulses several A/cm2 charges 1 μC/cm2 are measured. A tentative interpretation is given.
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...
In some axion dark matter models a dominant fraction of axions resides in dense small-scale substructures, miniclusters. A these substructures is disrupted and forms tidal streams where the density may still be an order magnitude larger than average. We discuss implications for direct searches. estimate miniclusters parameters resulting streams, find that stream-crossing events would occur at rate about $1/(20 {\rm yr})$ 2-3 days, during which signal detectors amplified by factor $\sim 10$....
Results are reported of an experimental search for the unique, rapidly varying temporal pattern solar axions coherently converting into photons via Primakoff effect in a single crystal germanium detector when incident at Bragg angle with crystalline plane. The analysis 1.94 kg yr data from 1 DEMOS Sierra Grande, Argentina, yields new laboratory bound by axion-photon coupling...
A new type of low-pressure gas switch is described. The triggered by an electron beam that emitted from the surface a ferroelectric sample. generated within hollow cathode and ejected through hole arbitrary shape into main gap switch. current energy can be chosen such breakdown achieved with small jitter. its trigger requires neither heating nor auxiliary discharge. fast spontaneous polarization change ΔPs, which cause emission, induced high-voltage pulse electronic switching circuit.
Standard Model extensions often predict low‐mass and very weakly interacting particles, such as the axion. A number of small‐scale experiments at intensity/precision frontier are actively searching for these elusive complementing searches physics beyond colliders. Whilst a next generation will give access to huge unexplored parameter space, discovery would have tremendous impact on our understanding fundamental physics.
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...
Gravitational lensing of invisible streaming matter towards the Sun with speeds around 10−4 to 10−3c could be explanation puzzling solar flares and unexplained emission in EUV. Assuming that this massive has some form interaction normal preferred directions exist its flow, then one would expect a more pronounced activity at certain planetary heliocentric longitudes. This is best demonstrated case Earth two inner planets, considering their relatively short revolution time (365, 225 88 days)...