Search

Vafeiadis, T. "Status of CAST and Solar Chameleon searches" in Proceedings, 10th Patras Workshop on Axions, WIMPs and WISPs (AXION-WIMP 2014) / Tsesmelis, Emmanuel, Maroudas, Marios (eds.), Verlag Deutsches Elektronen-Synchrotron : 2014 ; AXION-WIMP 2014 : 10th Patras Workshop on Axions, WIMPs and WISPs, 2014-06-29 - 2014-07-04, Geneva 10th Patras Workshop on Axions, WIMPs and WISPs, AXION-WIMP 2014, Geneva, Switzerland, 29 Jun 2014 - 4 Jul 2014 ; DESY-PROC 156-161(2014). doi:10.3204/DESY-PROC-2014-03/vafeiadis_theodoros, CERN Axion Solar Telescope (CAST) is the most powerful axion helioscope searching for axions and axion-like particles produced in the Sun. CAST completed its search for solar axions with $^{3}$He buffer gas in the magnet bores, covering axion masses up to 1.2 eV. In the absence of excess X-rays it has set the best experimental limit on the axion-photon coupling constant over a broad range of axion masses. In 2013 CAST has improved its sensitivity to solar axions with rest mass below 0.02 eV by using Micromegas detectors and it will continue in 2014 with the implementation of a second X-ray optic and a new type detector (InGrid). In 2013 CAST has extended its sensitivity into the sub-keV energy range using a silicon detector (SDD), to search for solar chameleons, extending its searches to the dark energy sector. This search will be continued in 2014 and 2015 as well with the InGrid detector. Future axion searches can improve the current axion sensitivity by 1 to 1.5 orders of magnitude with a new generation axion telescope (IAXO)., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

The CERN Axion Solar Telescope has finished its search for solar axions with 3He buffer gas, covering the search range 0.64 eV < m_a < 1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess X-rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g_aγ < 3.3×10^(−10) GeV^(−1) at 95% C.L., with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of g_aγ, for example by the currently discussed next generation helioscope International AXion Observatory.

Lakic, B. "Status and Perspectives of the CAST Experiment" in Proceedings, 9th Patras Workshop on Axions, WIMPs and WISPs (AXION-WIMP 2013) / Oberlack, Uwe, Sissol, Pierre (eds.), 2013 ; AXION-WIMP 2013 : 9th Patras Workshop on Axions, WIMPs and WISPs , 2013-06-23 - 2013-06-28, Mainz 9th Patras Workshop on Axions, WIMPs and WISPs, AXION-WIMP 2013, Mainz, Germany, 24 Jun 2013 - 28 Jun 2013; Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-PROC 119-122 (2013). doi:10.3204/DESY-PROC-2013-04/lakic_biljana_CAST, CERN Axion Solar Telescope (CAST) is currently the most sensitive axion helioscope designed to search for axions and axion-like particles produced in the Sun. CAST is using a Large Hadron Collider prototype magnet where axions could be converted into X-rays. So far, no evidence of signal has been found and CAST set the best experimental limit on the axion-photon coupling constant over a broad range of axion masses up to ∼ 1 eV., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

Axions are hypothetical particles arising in models which may solve the CP problem of strong interactions. They are practically stable neutral pseudoscalar particles and also viable candidates for the dark matter of the Universe. Most of the axion experimental searches are based on the axion coupling to two photons. As a consequence of this coupling, axion could transform into photon and vice versa in external electric and magnetic fields. Axions could be produced in the solar core by conversion of thermal photons in the Coulomb fields of nuclei and electrons – the Primakoff process, and back-converted into photons in a laboratory magnetic field. The CERN Axion Solar Telescope (CAST) is designed to search for these axions by using a Large Hadron Collider prototype dipole magnet which follows the Sun during sunrise and sunset throughout the year. To explore as wide as possible range of axion masses, the operation of CAST is divided in two phases. During the phase I the experiment operated with vacuum inside the magnet bores and scanned axion masses up to 0.02 eV. In order to extend the sensitivity to higher axion masses, the magnet bores are filled with a buffer gas at various densities. In the first part of the CAST phase II, 4He was used as a buffer gas. In the ongoing second part of the phase II, CAST has been using 3He to cover axion masses up to 1 eV. So far, no evidence of axion signal has been found and CAST set the most stringent experimental limit on the axion-photon coupling constant over a broad range of axion masses.

The CERN Axion Solar Telescope (CAST) is searching for axions produced in the Sun´s core by the Primakoff process. CAST is using a decommissioned Large Hadron Collider (LHC) test magnet where axions could be converted back into X-rays with energies up to 10 keV. Analysis of the 2003 data showed no signal above background implying an upper limit for the axion-photon coupling constant g_(a gamma) < 1.16 × 10^(-10) GeV^(-1) at 95% C.L. for m_a < = 0.02 eV [1]. The higher quality 2004 data is presently under analysis. CAST Phase II is scheduled to start in late 2005. This will be the first step in extending CAST´s sensitivity to axion rest masses up to 1 eV.

Axions are expected to be produced in the sun via the Primakoff process. They may be detected through the inverse process in the laboratory, under the influence of a strong magnetic field, giving rise to X-rays of energies in the range of a few keV. Such an Axion detector is the CERN Axion Solar Telescope (CAST), collecting data since 2003. Results have been published, pushing the axion-photon coupling g$_{a\gamma}$ below the 10$^{-10}$ GeV$^{-1}$ limit at 95% CL, for axion masses less than 0.02 eV. This limit is nearly an order of magnitude lower than previous experimental limits and surpassed for the first time limits set from astrophysical arguments based on the energy-loss concept. The experiment is currently exploring axion masses in the range of 0.02 eV $< m_a, Comment: 13 pages, 5 figures, presented in the conference "Les Rencontres de Physique de la Vallee d'Aoste, La Thuile, 4 - 10 March 2007, Italy"

The CAST Experiment commenced its first phase of solar axion-searching in 2003, and ran successfully for two years. In the transverse field of a decommissioned Large Hadron Collider (LHC) test magnet (9.26m, 9T), the CERN Axion Solar Telescope intends to transform axions -that would be produced in the sun- into X-rays with energies of a few keV. The first results from the analysis of the data taken in 2003 show no signature of axions, implying an upper limit to the axion-photon coupling g(a gamma) < 1.16 × 10-10 GeV-1 at 95% C.L. for ma < 0.02 eV, already a factor 100 better than previous searches. In Phase I the twin bores of the magnet were kept in vacuum. In Phase II (due to start in November 2005) the bores of the magnet will be filled with a buffer gas, which will allow CAST to explore the region of higher axion masses.

The CAST (CERN Axion Solar Telescope) experiment is searching for solar axions by their conversion into photons inside the magnet pipe of a LHC prototype dipole. In the phase II, CAST is operating with a buffer gas inside the magnet bore apertures in order to extent the sensitivity of the experiment to larger axion masses. Preliminary results from the analysis of this second phase with He inside the magnet pipes excludes axions down to $g_{aγ}$ < 2.2 · $10^{−10}GeV^{−1}$ at 95% C.L. for 0.02 eV < $m_{\alpha}$ < 0.39 eV. The data analysis has resulted in the most restrictive experimental limit on the coupling constant of axions to photons and for the first time experimental result has entered the theory motivated axion parameter space. At the beginning of 2008, data started to be taken with He in the magnet pipes in order to extend the sensitivity to axion masses up to 1.2 eV.