C. Eleftheriadis

The x-ray telescope of CAST

The CERN Axion Solar Telescope (CAST) has been in operation and taking data since 2003. The main objective of the CAST experiment is to search for a hypothetical pseudoscalar boson, the axion, which might be produced in the core of the sun. The basic physics process CAST is based on is the time inverted Primakoff effect, by which an axion can be converted into a detectable photon in an external electromagnetic field. The resulting x-ray photons are expected to be thermally distributed between 1 and 7 keV. The most sensitive detector system of CAST is a pn-CCD detector combined with a Wolter I type x-ray mirror system. With the x-ray telescope of CAST a background reduction of more than 2 orders of magnitude is achieved, such that for the first time the axion photon coupling constant gaγγ can be probed beyond the best astrophysical constraints gaγγ < 1 × 10−10 GeV−1.

Point defects in neutron-transmutation-doped Czochralski-grown Si studied by positron annihilation

Abstract Positron lifetime and Doppler broadening of the annihilation line measurements in neutron-transmutation-doped Czochralski-grown silicon have been performed. Three annealing stages are observed due to the different annealing behaviour of V2, V4 and V-P complexes.

The cern axion solar telescope (CAST)

A decommissioned LHC test magnet is being prepared as the CERN Axion Solar Telescope (CAST) experiment. The magnet has a field of 9.6 Tesla and length of 10 meters. It is being mounted on a platform to track the sun over ±8° vertically and ±45°, horizontally. A sensitivity in axion-photon coupling gαγγ < 5 × 10−11GeV−1 can be reached for mα ≤ 10−2eV, and with a gas filled tube-can reach gαγγ ≤ 10−10GeV−1 for axion masses mα < 2eV.

Axion searches at CERN with the CAST telescope

The CERN Axion Solar Telescope (CAST) searches for axions coming from photon to axion conversion in the suns core, as stated by the Primakoff effect. Axions arise in particle physics as a consequence of the breaking of Peccei-Quinn symmetry which has been introduced as a solution to the strong CP problem. As cosmological axions they are candidates for at least some part of cold Dark Matter.They are also expected to be produced copiously in stellar interiors with energies as high as the thermal photons undergoing photon to axion conversion. In our sun the axion energy spectrum peaks at about 4.4 keV, extending up to 10 keV. CAST collected preliminary data in 2002 and data taking with its full capability will start in the beginning of 2003.The CERN Axion Solar Telescope (CAST) searches for axions coming from photon to axion conversion in the suns core, as stated by the Primakoff effect. Axions arise in particle physics as a consequence of the breaking of Peccei-Quinn symmetry which has been introduced as a solution to the strong CP problem. As cosmological axions they are candidates for at least some part of cold Dark Matter.They are also expected to be produced copiously in stellar interiors with energies as high as the thermal photons undergoing photon to axion conversion. In our sun the axion energy spectrum peaks at about 4.4 keV, extending up to 10 keV. CAST collected preliminary data in 2002 and data taking with its full capability will start in the beginning of 2003.

Results of CPLEAR

The CPLEAR experiment uses tagged K 0 and K 0 produced in pp annihilation at rest to measure CP-, T- and CPT-violation parameters in the neutral kaon system. The results of these measurements and some implications are reported.

Search for solar axions: the CAST experiment

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 X‐rays 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 showed 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 allowed us to lower down this parameter to a preliminary value of gaγ < 0.9 × 10−10 GeV−1.

Contribution of CPLEAR to the physics of the neutral-kaon system

Abstract We report the results of the CPLEAR experiment on CP-, T-, and CPT-symmetries in the neutral kaon system. CP-violation parameters are given for the K 0 , K 0 → 2π, 3π decay channels. For the first time, T-violation is measured by a direct method using semileptonic decays. The CPT symmetry is tested through the parameters Im(δ) with a precision of 10 −5 and Re(δ) with a precision of a few 10 −4 . With these two measurements, the difference in mass and width of K 0 and K 0 are bound to within 10 −18 GeV. In the limit of CPT invariance in the neutral kaon decays, the K 0 and K 0 masses are equal within 10 −19 GeV.

The CPLEAR-Experiment at CERN

The CPLEAR experiment uses tagged K0 and K0 produced in pp annihilation at rest to measure CP-, T- and CPT-violation parameters in the neutral kaon system. The results of these measurements and some implications are reported.

Measurement of the o-Ps decay rate using an energy and time spectrometer

A spectrometer for direct positronium annihilation measurements (lifetime as well as energy distribution of annihilation photons) has been built, based on an existing energy spectrometer1 presented by our group. A time branch has been added which allowed us to measure the o-Ps lifetime. We found the decay rate to be 7.0458±0.0279 μs−1.

Parameters affecting three-photon positron annihilation spectrometers

Abstract The background and other problems associated with three-photon annihilation spectrometers were studied. A detailed description of a CAMAC-controlled three-photon annihilation spectrometer, developed in our laboratory, is given. Experimental data collected at various geometrical arrangements are presented and discussed. The spectra are compared with those obtained by a Monte Carlo simulation program.