The Latest from ALICE

After intensive installation operations from October 2008 until July 2009 (see Bulletin 31/7/2009), ALICE started a full-detector cosmics run in August, which is scheduled to last until the end of October.

In addition to the Silicon Pixel and ACORDE detectors, the latter specially built for triggering on cosmic muons, ALICE is now making extensive use of the trigger provided by the Time Of Flight array. The high granularity and the low noise (0.1 Hz/cm2) of the TOF MRPCs, combined with the large coverage (~150 m²), offers a wide range of trigger combinations.

This extended cosmic run serves many purposes: to test the performance of each individual detector; to ensure their integration in the central Data Acquisition; to perform alignment and calibration; to check the reconstruction software; to fine-tune the tracking algorithms; and last but not least, to train the personnel for the long shifts ahead.

More than 100 million events have been accumulated in the central detectors, both with and without magnetic field, and they are now being reconstructed and analyzed. Even the forward muon system, which is oriented parallel to the LHC beam, has collected several 10,000 of the very rare quasi-horizontal cosmic rays which traverse the full length of the spectrometer at a rate of one particle every couple of minutes.

Over the last weeks, data taking with the ‘cosmic accelerator’ has become an almost routine operation, reaching high efficiency and stable conditions, and demonstrating that the ALICE detector and its operating crew are in good shape for first collisions later this year.

ALICE Collaboration