Showing papers by "K. van Bibber published in 2008"

Probing eV-scale axions with CAST

Abstract: 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 have reported results from CAST with evacuated magnet bores (Phase I), setting limits on lower mass axions, here we report results from CAST where the magnet bores were filled with \hefour gas (Phase II) of variable pressure. The introduction of gas generated a refractive photon mass $m_\gamma$, thereby achieving the maximum possible conversion rate for those axion masses \ma that match $m_\gamma$. With 160 different pressure settings we have scanned \ma up to about 0.4 eV, taking approximately 2 h of data for each setting. 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 $\gag\lesssim 2.17\times 10^{-10} {\rm GeV}^{-1}$ at 95% CL for $\ma \lesssim 0.4$ eV, the exact result depending on the pressure setting. The excluded parameter range covers realistic axion models with a Peccei-Quinn scale in the neighborhood of $f_{\rm a}\sim10^{7}$ GeV. Currently in the second part of CAST Phase II, we are searching for axions with masses up to about 1.2 eV using \hethree as a buffer gas.

Search for Low Energy Solar Axions with CAST

Abstract: 1. European Organization for Nuclear Research (CERN), Gen`eve, Switzerland2. DAPNIA, Centre d’´Etudes Nucl´eaires de Saclay (CEA-Saclay), Gif-sur-Yvett e, France3. Technische Universita¨t Darmstadt, IKP, Darmstadt, Germany4. Max-Planck-Institut fu¨r extraterrestrische Physik, Garching, Germany5. Instituto de F´isica Nuclear y Altas Energ´ias, Universidad de Zaragoza, Zaragoza, Spain6. Enrico Fermi Institute and KICP, University of Chicago, Chicago, IL, USA7. Aristotle University of Thessaloniki, Thessaloniki, Greece8. National Center for Scientific Research “Demokritos”, Athens, Greece9. Albert-Ludwigs-Universita¨t Freiburg, Freiburg, Germany10. Institute for Nuclear Research (INR), Russian Academy of Sciences, Moscow, Russia11. Department of Physics and Astronomy, University of British Columbia, Department of Physics, Vancouver,Canada12. Johann Wolfgang Goethe-Universita¨t, Institut fu¨r Angewandte Physik, Frankfurt am Main, Germany13. Max-Planck-Institut fu¨r Physik (Werner-Heisenberg-Institut), Munich, Germany14. Rudjer Boˇskovi´c Institute, Zagreb, Croatia15. Physics Department, University of Patras, Patras, Greece16. Lawrence Livermore National Laboratory, Livermore, CA, USA17. Dogus University, Istanbul, Turkey18. Instituto Nazionale di Fisica Nucleare (INFN), Sezione di Trieste and Universita` di Trieste, Trieste, Italy19. Max-Planck-Institut fu¨r Aeronomie, Katlenburg-Lindau, Germany20. National Technical University of Athens, Athens, Greece

The search for axions

Abstract: The axion is a light pseudoscalar particle predicted to exist as a consequence of the Peccei–Quinn solution to the strong-CP problem. Its abundant production in the early Universe along with its stability and insignificant interaction cross-section make it a prime dark matter candidate. This report summarises the search for dark matter axions using resonant microwave cavities as well as searches for axions produced in the Sun and in the laboratory. All of these current experiments focus on the axion–photon interaction, as coherent axion–photon mixing in strong magnetic fields of large spatial extent can make up for the extraordinary weakness of the the coupling of axions to photons.

Solar axion search with the CAST experiment

Abstract: The CAST (CERN Axion Solar Telescope) experiment is searching for solar axions by their conversion into photons inside the magnet pipe of an LHC dipole. The analysis of the data recorded during the first phase of the experiment with vacuum in the magnet pipes has resulted in the most restrictive experimental limit on the coupling constant of axions to photons. In the second phase, CAST is operating with a buffer gas inside the magnet pipes in order to extent the sensitivity of the experiment to higher axion masses. We will present the first results on the $^{4}{\rm He}$ data taking as well as the system upgrades that have been operated in the last year in order to adapt the experiment for the $^{3}{\rm He}$ data taking. Expected sensitivities on the coupling constant of axions to photons will be given for the recent $^{3}{\rm He}$ run just started in March 2008.

Solar axion search with the CAST experiment

Abstract: Boydag, Fatma Senel (Dogus Author), Cetin, Serkant Ali (Dogus Author), Hikmet, Iskender (Dogus Author) -- Proceedings of the 34th International Conference in High Energy Physics : (ICHEP08) Philadelphia, Pennsylvania, July 29 - August 5, 2008.

Search for low Energy solar Axions with CAST

Abstract: We have started the development of a detector system, sensitive to single photons in the eV energy range, to be suitably coupled to one of the CAST magnet ports. This system should open to CAST a window on possible detection of low energy Axion Like Particles emitted by the sun. Preliminary tests have involved a cooled photomultiplier tube coupled to the CAST magnet via a Galileian telescope and a switched 40 m long optical fiber. This system has reached the limit background level of the detector alone in ideal conditions, and two solar tracking runs have been performed with it at CAST. Such a measurement has never been done before with an axion helioscope. We will present results from these runs and briefly discuss future detector developments.