Search for low energy solar axions with CAST

Nuclear and Particle Physics Proceedings, 2016

Although they have not yet been detected, axions and axion-like particles (ALPs) continue to maintain the interest (even increasingly so) of the rare-event searches community as viable candidates for the Dark Matter of the Universe but also as a solution for several other puzzles of astrophysics. Their property of coupling to photons has inspired different experimental methods for their detection, one of which is the helioscope technique. The CERN Axion Solar Telescope (CAST) is the most sensitive helioscope built up to date and has recently published part of the latest data taken with the magnet bores gradually filled with 3 He, probing the mass range up to 1.17 eV. The International AXion Observatory (IAXO) is being proposed as a facility where different axion studies can be performed, with the primary goal to study axions coming from the Sun. Designed to maximize sensitivity, it will improve the levels reached by CAST by almost 5 orders of magnitude in signal detection, that is more than one order of magnitude in terms of g aγ. Here we will summarize the most important aspects of the helioscopes, and focus mainly on IAXO, based on the recent papers [1, 2].

Kalliokoski, 2015

In this work, I present an innovative idea to search for solar axions using a large volume low background Time Projection Chamber (TPC) immersed in a magnetic field. This technique will be sensitive to axion masses above few hundreds of meV in the theoretically favored QCD-axion parameter space. The detector geometry will be such that will allow to monitor the solar axion flux during the whole day. A stationary detector would produce a daily and annual modulation signal pattern given by the angle of the incident axion flux and the TPC magnetic field which is driven by the earth rotation. Recent progress on large volume low background TPC's for rare event searches motivates the development of such helioscope technique. The principle of detection and prospects on the sensitivity of such an experiment will be shown.

Astroparticle, Particle and Space Physics, Detectors and Medical Physics Applications, 2008

The CAST (CERN Axion Solar Telescope) experiment at CERN searches for solar axions with energies in the keV range. It is possible that axions are produced in the core of the sun by the interaction of thermal photons with virtual photons of strong electromagnetic fields. In this experiment, the solar axions. can be reconverted to photons in the transversal field of a 9 Te sla superconducting magnet. At both ends of the lOm-long dipole magnet three different X-ray detectors were installed , which are sensitive in the interesting photon energy range. Preliminary results from the analysis of the 2004 data are presented: g00 < 0.9 x 10-i o Gev-1 at 953 C.L. for axion masses m0 < 0.02 eV. At the end of 2005, data started to be taken with a buffer gas in the magnet pipes in order to extend the sensitivity to axion masses up to 0.8 eV.

Journal of Cosmology and Astroparticle Physics, 2011

We study the feasibility of a new generation axion helioscope, the most ambitious and promising detector of solar axions to date. We show that large improvements in magnetic field volume, x-ray focusing optics and detector backgrounds are possible beyond those achieved in the CERN Axion Solar Telescope (CAST). For hadronic models, a sensitivity to the axion-photon coupling of g aγ few × 10 −12 GeV −1 is conceivable, 1-1.5 orders of magnitude beyond the CAST sensitivity. If axions also couple to electrons, the Sun produces a larger flux for the same value of the Peccei-Quinn scale, allowing one to probe a broader class of models. Except for the axion dark matter searches, this experiment will be the most sensitive axion search ever, reaching or surpassing the stringent bounds from SN1987A and possibly testing the axion interpretation of anomalous white-dwarf cooling that predicts m a of a few meV. Beyond axions, this new instrument will probe entirely unexplored ranges of parameters for a large variety of axion-like particles (ALPs) and other novel excitations at the low-energy frontier of elementary particle physics. 6 Detectors 25 7 Conclusions 28

Journal of Cosmology and Astroparticle Physics, 2015

We explore the possibility to develop a new axion helioscope type, sensitive to the higher axion mass region favored by axion models. We propose to use a low background large volume TPC immersed in an intense magnetic field. Contrary to traditional tracking helioscopes, this detection technique takes advantage of the capability to directly detect the photons converted on the buffer gas which defines the axion mass sensitivity region, and does not require pointing the magnet to the Sun. The operation flexibility of a TPC to be used with different gas mixtures (He, Ne, Xe, etc) and pressures (from 10 mbar to 10 bar) will allow to enhance sensitivity for axion masses from few meV to several eV. We present different helioscope data taking scenarios, considering detection efficiency and axion absorption probability, and show the sensitivities reachable with this technique to be few × 10 −11 GeV −1 for a 5 T, m 3 scale TPC. We show that a few years program taking data with such setup would allow to probe the KSVZ axion model for axion masses above 100 meV.

2006

Hypothetical axion-like particles with a two-photon interaction would be produced in the sun by the Primakoff process. In a laboratory magnetic field they would be transformed into Xrays with energies of a few keV. The CAST experiment at CERN is using a decommissioned LHC magnet as an axion helioscope in order to search for these axion-like particles. The analysis of the 2003 data 1 has shown no signal above the background, thus implying an upper limit to the axion-photon coupling of gaγ < 1.16 × 10 −10 GeV −1 at 95% CL for ma 0.02 eV. The stable operation of the experiment during 2004 data taking allow us to anticipate that this value will be improved. At the end of 2005 we expect to start with the so-called second phase of CAST, when the magnet pipes will be filled with a buffer gas so that the axion-photon coherence will be extended. In this way we will be able to search for axions with masses up to 1 eV.

Arxiv preprint hep-ex/0304024, 2003

The new axion helioscope at CERN started acquiring data during September of 2002: CAST (Cern Axion Solar Telescope) employs a decommissioned LHC dipole magnet to convert putative solar axions or axion-like particles into detectable photons. The unprecedented dipole magnet intensity and length (9.5 T, 10 m) results in a projected sensitivity that surpasses astrophysical constraints on these particles for the first time, increasing the chance of discovery. The use of X-ray focusing optics and state-of-the-art detector technology has led to an extremely low background for an experiment above ground. A brief status report is given, with emphasis on the tracking and control system and possible future extensions.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2010

It has been shown that a detector system, sensitive to single photons in the eV range can be coupled to the CAST experiment [1]. However the detectors used had high background rates compared with the expected signal, thus a search for a detector suitable for integrating in the present setup and with a low background rates was initiated. A suitable detector candidate was found and results from first tests are presented.

2006

a Deceased Hypothetical axion-like particles with a two-photon interaction would be produced in the sun by the Primakoff process. In a laboratory magnetic field they would be transformed into Xrays with energies of a few keV. The CAST experiment at CERN is using a decommissioned LHC magnet as an axion helioscope in order to search for these axion-like particles. The analysis of the 2003 data 1 has shown no signal above the background, thus implying an upper limit to the axion-photon coupling of gaγ < 1.16 × 10 −10 GeV −1 at 95% CL for ma 0.02 eV. The stable operation of the experiment during 2004 data taking allow us to anticipate that this value will be improved. At the end of 2005 we expect to start with the so-called second phase of CAST, when the magnet pipes will be filled with a buffer gas so that the axion-photon coherence will be extended. In this way we will be able to search for axions with masses up to 1 eV.

Proceedings of 38th International Conference on High Energy Physics — PoS(ICHEP2016), 2017

The International Axion Observatory (IAXO) is a forth generation axion helioscope designed to detect solar axions and axion-like particles (ALPs) with a coupling to the photon g aγ down to a few 10 −12 GeV −1 , 1.5 orders of magnitude beyond the current best astrophysical and experimental upper bounds. This range includes parameter values invoked in the context of the observed anomalies in light propagation over astronomical distances and to explain the excessive cooling observed in a number of stellar objects. Here we review the status of the IAXO project and of its potential to probe the most physically motivated regions of the axion/ALPs parameter space.