Nagoya University Global COE Program　Quest for Fundamental Principles in the Universe

The earth is constantly bombared with high energy particles called cosmic-rays. A cosmic-ray particle repeats interaction with the molecules in the atmosphere and produces a shower of particles arriving at the ground level. High energy cosmic-rays, hence the high energy phenomena in the universe are studied by observing these air showers. However, the interaction in the atmosphere is not sufficiently understood because the energy range exceeds the energy of the man-made accelerators so far. The LHCf experiment is carried out to improve the situation.

LHCf measures particles emitted in the very forward direction, those are important to understand the air shower development but are not measured by the huge experiments, in the collisions at the LHC accelerator. Using the highest enery man-made accelerator, we can understand the interaction at 3 orders of magnitude higher energy than the previous study. Combining with the results of the huge cosmic-ray observation experiments, we can progress to understand the high energy phenomena in the universe.

LHCf is an international collaboration of Japan, 4 European coutries and USA. In the small group of 30 members, graduate students of the Nagoya university play the most important role. Each member stays at CERN for a few months every year not only to prepare the experiment but also to discuss and negotiate with the foreign collaborators, members of other experiments and the staff of CERN. Each member can (must) experience whole process of the experiment such like detector construction and simulation.

On 10 September, 2008, the LHC succeeded to circulate the first proton beam in its 27km beam pipe ring. Even before acceleration and collisions, backgroud between the beam particles and the residual gas was an important tool for the detector calibration. LHCf has prepared to take this first data and succeeded to detect the background particles when the LHC beam has stabilized on 12 September. This event confirmed the reliability of the data acquisition system that must synchronize with the actual beam timing.

Unfortunately, LHC has met a serious trouble soon after and closed for an year. LHCf is improving data acquisition system and simulation studies more precisely. In January 2009, the LHCf members met together at the Nagoya university and discussed for the operation in the coming years. LHCf can collect sufficient data in the early phase of the LHC operation. We are now preparing more robust data acquisition and analysis system for the operation expected in the end of 2009.