84 research outputs found
Overlooked astrophysical signatures of axion(-like) particles
The working principle of axion helioscopes can be behind unexpected solar X-ray emission, being associated with solar magnetic fields, which become the catalyst. Solar axion signals are transient brightenings, or, continuous radiation. We arrive at 2 exotica: a) trapped, radiatively decaying, massive axions and b) outstreaming light axions, explaining unpredictable transient solar phenomena. Then, the energy of a related phenomenon points at the birth place of the axions. The energy range below some 100 eV is a window of opportunity for direct axion searches. Indirect signatures support axions or the like as an explanation of enigmatic behaviour in the Sun and beyond. Axion antennas could take advantage of such a feed back.The working principle of axion helioscopes can be behind unexpected solar X-ray emission, being associated with solar magnetic fields, which become the catalyst. Solar axion signals can be transient brightenings as well as continuous radiation. The energy range below 1 keV is a window of opportunity for direct axion searches. (In)direct signatures support axions or the like as an explanation of striking behaviour of X-rays from the Sun
Solar X-rays from Axions: Rest-Mass Dependent Signatures
The spectral shape of solar X-rays is a power law. The more active the Sun
is, the less steep the distribution. This behaviour can be explained by axion
regeneration to X-rays occurring ~400km deep into the photosphere. Their
down-comptonization reproduces the measured spectral shape, pointing at axions
with rest mass m_a~17 meV/c2, without contradicting astrophysical-laboratory
limits. Directly measured soft X-ray spectra from the extremely quiet Sun
during 2009 (SphinX mission), though hitherto overlooked, fitt the axion
scenario.Comment: To appear in Proceedings of the 5th Patras Axion Workshop, Durham
200
Signatures for Solar Axions/WISPs
Standard solar physics cannot account for the X-ray emission and other
puzzles, the most striking example being the solar corona mystery. The corona
temperature rise above the non-flaring magnetized sunspots, while the
photosphere just underneath becomes cooler, makes this mystery more intriguing.
The paradoxical Sun is suggestive of some sort of exotic solution, axions being
the (only?) choice for the missing ingredient. We present atypical axion
signatures, which depict solar axions with a rest mass max ~17 meV/c2. Then,
the Sun has been for decades the overlooked harbinger of new particle physics.Comment: To appear in the proceedings of the 6th Patras Workshop, Zurich 5-9
July 201
Fast Timing for High-Rate Environments with Micromegas
The current state of the art in fast timing resolution for existing
experiments is of the order of 100 ps on the time of arrival of both charged
particles and electromagnetic showers. Current R&D on charged particle timing
is approaching the level of 10 ps but is not primarily directed at sustained
performance at high rates and under high radiation (as would be needed for
HL-LHC pileup mitigation). We demonstrate a Micromegas based solution to reach
this level of performance. The Micromegas acts as a photomultiplier coupled to
a Cerenkov-radiator front window, which produces sufficient UV photons to
convert the ~100 ps single-photoelectron jitter into a timing response of the
order of 10-20 ps per incident charged particle. A prototype has been built in
order to demonstrate this performance. The first laboratory tests with a
pico-second laser have shown a time resolution of the order of 27 ps for ~50
primary photoelectrons, using a bulk Micromegas readout.Comment: MPGD2015 (4th Conference on Micro-Pattern Gaseous Detectors, Trieste,
Italy, 12 - 15 October, 2015). 5 pages, 8 figure
Micromegas at low pressure for beam tracking
New facilities like FAIR at GSI or SPIRAL2 at GANIL, will provide radioactive ion beams at low energies (less than 10 MeV/n). Such beams have generally a large emittance, which requires the use of beam tracking detectors to reconstruct the exact trajectories of the nuclei. To avoid the angular and energy straggling that classical beam tracking detectors would generate in the beam due to their thickness, we propose the use of SED (Secondary Electron Detectors). It consists of a low pressure gaseous detector placed outside the beam coupled to an emissive foil in the beam. Since 2008, different low pressure gaseous detectors (wire chambers and micromegas) have been constructed and tested. The performances achievable at low pressure are similar to or even better than the ones at atmospheric pressure. The fast charge collection leads to excellent timing properties as well as high counting rate capabilities. Several micromegas at low pressure were tested in the laboratory demonstrating a good time resolution, 13030 ps, which is compatible with the results obtained with wire chambers.Gobierno de España FPA2009-0884
CAST: Recent results & future outlook
Çetin, Serkant Ali (Dogus Author) -- Ezer, Cemile (Dogus Author) -- Yıldız, Süleyman Cenk (Dogus Author) -- Conference full title: 6th Patras Workshop on Axions, WIMPs and WISPs, PATRAS 2010; Zurich; Switzerland; 5 July 2010 through 9 July 2010.The CAST (CERN Axion Solar Telescope) experiment is searching for solar axions by their conversion into photons inside the magnet pipes of an LHC dipole. The analysis of data taken so far has shown no signal above the background, thus implying an upper limit to the axion-photon coupling of ga < 0.85 × 10-10GeV -1 at 95% CL for ma < 0.02 eV/c2. Ongoing measurements, with the magnet bores filled with a buffer gas (3He), are improving the sensitivity of the experiment for higher axion masses towards 1 eV/c2. Recent results, new ideas for Axion-Like Particle (WISPs) searches with CAST in the near future and the prospects of a new generation Helioscope are presented here
CAST constraints on the axion-electron coupling
In non-hadronic axion models, which have a tree-level axion-electron interaction, the Sun produces a strong axion flux by bremsstrahlung, Compton scattering, and axiorecombination, the "BCA processes." Based on a new calculation of this flux, including for the first time axio-recombination, we derive limits on the axion-electron Yukawa coupling gae and axion-photon interaction strength ga using the CAST phase-I data (vacuum phase). For ma <~ 10 meV/c2 we find ga gae < 8.1 × 10−23 GeV−1 at 95% CL. We stress that a next-generation axion helioscope such as the proposed IAXO could push this sensitivity into a range beyond stellar energy-loss limits and test the hypothesis that white-dwarf cooling is dominated by axion emission
A large area 100 channel Picosec Micromegas detector with sub 20 ps time resolution
The PICOSEC Micromegas precise timing detector is based on a Cherenkov
radiator coupled to a semi-transparent photocathode and a Micromegas
amplification structure. The first proof of concept single-channel small area
prototype was able to achieve time resolution below 25 ps. One of the crucial
aspects in the development of the precise timing gaseous detectors applicable
in high-energy physics experiments is a modular design that enables large area
coverage. The first 19-channel multi-pad prototype with an active area of
approximately 10 cm suffered from degraded timing resolution due to the
non-uniformity of the preamplification gap. A new 100 cm detector module
with 100 channels based on a rigid hybrid ceramic/FR4 Micromegas board for
improved drift gap uniformity was developed. Initial measurements with 80 GeV/c
muons showed improvements in timing response over measured pads and a time
resolution below 25 ps. More recent measurements with a new thinner drift gap
detector module and newly developed RF pulse amplifiers show that the
resolution can be enhanced to a level of 17~ps. This work will present the
development of the detector from structural simulations, design, and beam test
commissioning with a focus on the timing performance of a thinner drift gap
detector module in combination with new electronics using an automated timing
scan method
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