by The new IAXO pathfinder system, installed in CAST in 2014, has been taking data during all 2015 with outstanding performance. The signal to noise ratio (SNR) of the system has been the best ever in the history of the experiment. The effective background of the detectors (that is, the expected background counts in the energy region of interest and the signal spot) is of about 5 x10-3 counts per second. This means that the system records only one count of background on average every four months of data taking in CAST.
The data obtained with this system during 2015 is now under analysis. It should improve previous sensitivity of CAST.
A paper (see also the preprint) describing the system has recently been published in JCAP:
