Guidelines for axion identification in astrophysical observations

The origin of various celestial phenomena have remained mysterious for conventional astrophysics. Therefore, alternative solutions should be considered, taking into account the involvement of unstable dark-matter particle candidates, such as the celebrated axions or other as yet unforeseen axion-like particles. Their spontaneous and induced decay by the ubiquitous solar magnetic fields can be at the origin of persisting enigmatic X-ray emission, giving rise to a steady and a transient/local solar activity, respectively. The (coherent) conversion of photons into axion(-like) particles in intrinsic magnetic fields may modify the solar axion spectrum. The reversed process can be behind transient (solar) luminosity deficits in the visible. Then, the Sun might be also a strong source of ~eV-axions. Thus, enigmatic observations might be the as yet missing direct signature for axion(-like) particles in earth-bound detectors.Comment: 6 pages, to be submitted to JCA

Quiet Sun X-rays as Signature for New Particles

We have studied published data from the Yohkoh solar X-ray mission, with the purpose of searching for signals from radiative decays of new, as yet undiscovered massive neutral particles. This search is based on the prediction that solar axions of the Kaluza-Klein type should result in the emission of X-rays from the Sun direction beyond the limb with a characteristic radial distribution. These X-rays should be observed more easily during periods of quiet Sun. An additional signature is the observed emission of hard X-rays by SMM, NEAR and RHESSI. The recent observation made by RHESSI of a continuous emission from the non-flaring Sun of X-rays in the 3 to ~15 keV range fits the generic axion scenario. This work also suggests new analyses of existing data, in order to exclude instrumental effects; it provides the rationale for targeted observations with present and upcoming (solar) X-ray telescopes, which can provide the final answer on the nature of the signals considered here. Such measurements become more promising during the forthcoming solar cycle minimum with an increased number of quiet Sun periods.Comment: 14 pages, 3 figures; to be published in ApJ. May 20 200

Precise charged particle timing with the PICOSEC detector

The experimental requirements in near future accelerators (e.g. High Luminosity-LHC) has stimulated intense interestin development of detectors with high precision timing capabilities. With this as a goal, a new detection concept called PICOSEC,which is based to a “two-stage” MicroMegas detector coupled to a Cherenkov radiator equipped with a photocathode has beendeveloped. Results obtained with this new detector yield a time resolution of 24 ps for 150 GeV muons and 76 ps for single pho-toelectrons. In this paper we will report on the performance of the PICOSEC in test beams, as well as simulation studies andmodelling of its timing characteristicsPeer reviewe

Charged particle timing at sub-25 picosecond precision : The PICOSEC detection concept

The PICOSEC detection concept consists in a “two-stage” Micromegas detector coupled to a Cherenkov radiator and equipped with a photocathode. A proof of concept has already been tested: a single-photoelectron response of 76 ps has been measured with a femtosecond UV laser at CEA/IRAMIS, while a time resolution of 24 ps with a mean yield of 10.4 photoelectrons has been measured for 150 GeV muons at the CERN SPS H4 secondary line. This work will present the main results of this prototype and the performance of the different detector configurations tested in 2016-18 beam campaigns: readouts (bulk, resistive, multipad) and photocathodes (metallic+CsI, pure metallic, diamond). Finally, the prospects for building a demonstrator based on PICOSEC detection concept for future experiments will be discussed. In particular, the scaling strategies for a large area coverage with a multichannel readout plane, the R&D on solid converters for building a robust photocathode and the different resistive configurations for a robust readout.Peer reviewe

FALSTAFF : a New Tool for Fission Fragment Characterization

Neutron for Science/SPIRAL2International audienceThe future Neutron For Science (NFS) facility to be installed at SPIRAL2 (Caen, France) will produce high intensity neutron beams from hundreds of keV up to 40 MeV. Taking advantage of this facility, data of particular interest to the nuclear community, in view of the development of fast reactor technology, will be measured. The development of an experimental setup called FALSTAFF for a full characterization of actinide fission fragments has been undertaken. Fission fragment isotopic yields and associated neutron multiplicities will be measured as a function of the neutron energy. Based on time-of-flight and residual energy technique, the setup will allow for the simultaneous measurement of the velocity and energy of the complementary fragments. The performance of the time-of-flight detectors of FALSTAFF will be presented and expected resolutions for fragment masses and neutron multiplicities, based on realistic simulations, will be shown