M. Kuster, S. Gerhard, G. Hoffmeister, D. Weber, TU Darmstadt, Darmstadt, Germany D. H. H. Hoffmann, GSI, TU Darmstadt, Darmstadt, Germany K. Zioutas, University of Patras, Patras, Greece
The sun provides a deep insight into the physics of fusion, the physics of hot plasmas and is an excellent laboratory for astroparticle physics. As such the sun can be used to probe the existence of novel particles and dark matter candidates like the axion. The axion is a direct consequence (2; 3) of the theoretical solution of the CP problem in strong interactions proposed by (1). Inside the core of the sun axions could be produced by coherent conversion of thermal photons interacting with the electromagnetic field of charged particles of the solar plasma (Primakoff effect).
With the CAST experiment at CERN, we aim to detect such solar axions on earth by “converting” them back to Xray photons inside a strong transversal magnetic field (inverse Primakoff effect, see Fig. 1). The conversion probability of axions to photons is proportional to the square of the strength of the magnetic field and its length. Thus, a strong magnetic field is essential to achieve a high sensitivity of the experiment.
The heart of CAST is a prototype LHC superconducting magnet providing a dipole magnetic field of 9 T in the interior of two parallel pipes over a distance of 9:26m. On both ends of the magnet X-ray detectors are looking for a potential axion signal as an excess signal over detector background. A TPC detector covers two magnet bores on one end looking for axions during sunset. On the opposite side of the magnet, a micro mesh gas detector and an X-ray telescope with a pn-CCD detector are looking for axions at sunrise. The magnet can be pointed towards the sun for about 1:5 h during sunrise and sunset, resulting in 3 h observation time per day. The remaining time is used for systematic background studies. The most sensitive detector system of CAST is theWolter I type X-ray telescope which enhances the signal-to-background ratio by a factor of 100 by concentrating the potential signal flux on a small spot on the pn-CCD detector.
During the last two years CAST was taking data for about twelve months, six months during 2003 and during 2004. The analysis of the data reveals no significant excess signal over background and allows us to set a new upper limit on the axion to photon coupling. Fig. 2 shows the preliminary corresponding upper limit for the axion to photon coupling constant ga derived from the data aquired
with the X-ray telescopes during 2004. The analysis of the 2004 data is still in progress and we expect to further improve the upper limit in the CAST axion sensitive mass range ma < 0:02 eV, although the present preliminary result is already comparable to the best astrophysical constraints (see Fig. 2). Due to coherence effects, the CAST helioscope in its configuration during 2004 was sensitive for axions with masses ma < 0:02 eV, only. To extend the sensitivity of CAST to ma < 0:8 eV, the refractive index of the conversion volume has to be changed using a buffer gas, either 4He or 3He. Then, the photon acquires an effective mass (m= ma) and the momentum exchange during the Primakoff process becomes negligible (phase II of CAST). During 2005 the CAST magnet has been transformed into its phase II configuration, allowing to be operated with a buffer gas (4He) inside the conversion volume. First data has successfully been taken with the new experimental setup at the end of 2005 and data taking will be continued at the beginning of this year.
du bist echt ein held. einen für deine zählweise erreichten zwischenpunkt ergattert und dann wieder für die nächsten 50 posts nix. man mußdir langweilig sein.
M. Kuster, S. Gerhard, G. Hoffmeister, D. Weber, TU Darmstadt, Darmstadt, Germany
D. H. H. Hoffmann, GSI, TU Darmstadt, Darmstadt, Germany
K. Zioutas, University of Patras, Patras, Greece
the physics of hot plasmas and is an excellent laboratory
for astroparticle physics. As such the sun can be
used to probe the existence of novel particles and dark matter
candidates like the axion. The axion is a direct consequence
(2; 3) of the theoretical solution of the CP problem
in strong interactions proposed by (1). Inside the core of
the sun axions could be produced by coherent conversion of
thermal photons interacting with the electromagnetic field
of charged particles of the solar plasma (Primakoff effect).
such solar axions on earth by “converting” them back to Xray
photons inside a strong transversal magnetic field (inverse
Primakoff effect, see Fig. 1). The conversion probability
of axions to photons is proportional to the square of
the strength of the magnetic field and its length. Thus, a
strong magnetic field is essential to achieve a high sensitivity
of the experiment.
magnet providing a dipole magnetic field of 9 T in
the interior of two parallel pipes over a distance of 9:26m.
On both ends of the magnet X-ray detectors are looking
for a potential axion signal as an excess signal over detector
background. A TPC detector covers two magnet bores
on one end looking for axions during sunset. On the opposite
side of the magnet, a micro mesh gas detector and
an X-ray telescope with a pn-CCD detector are looking for
axions at sunrise. The magnet can be pointed towards the
sun for about 1:5 h during sunrise and sunset, resulting in
3 h observation time per day. The remaining time is used
for systematic background studies. The most sensitive detector
system of CAST is theWolter I type X-ray telescope
which enhances the signal-to-background ratio by a factor
of 100 by concentrating the potential signal flux on a
small spot on the pn-CCD detector.
about twelve months, six months during 2003 and during
2004. The analysis of the data reveals no significant excess
signal over background and allows us to set a new upper
limit on the axion to photon coupling. Fig. 2 shows
the preliminary corresponding upper limit for the axion to
photon coupling constant ga
derived from the data aquired
2004 data is still in progress and we expect to further improve
the upper limit in the CAST axion sensitive mass
range ma < 0:02 eV, although the present preliminary result
is already comparable to the best astrophysical constraints
(see Fig. 2). Due to coherence effects, the CAST
helioscope in its configuration during 2004 was sensitive
for axions with masses ma < 0:02 eV, only. To extend
the sensitivity of CAST to ma < 0:8 eV, the refractive index
of the conversion volume has to be changed using a
buffer gas, either 4He or 3He. Then, the photon acquires
an effective mass (m= ma) and the momentum exchange
during the Primakoff process becomes negligible (phase II
of CAST). During 2005 the CAST magnet has been transformed
into its phase II configuration, allowing to be operated
with a buffer gas (4He) inside the conversion volume.
First data has successfully been taken with the new experimental
setup at the end of 2005 and data taking will be
continued at the beginning of this year.
[1] Peccei, R. D., & Quinn, H. R., 1977, Phys. Rev. Lett.,
38, 1440
[2] Weinberg, S., 1978, Phys. Rev. Lett., 40, 223
[3] Wilczek, F., 1978, Phys. Rev. Lett., 40, 279
[4] Zioutas, K., et al., 2005, Phys. Rev. Lett.,
Hast Du sonst niemanden, der mit Dir spricht ?
Jaaa, immer schön rein in die Wunde