Taking a closer look at LHC

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LHCf

LHCf (LHC forward) experiment is placed on either side of the ATLAS experimentcan accurately measure the number and energy of neutral pions and other particles forward direction in ATLAS collisions. about 140 meters from the interaction point at a zero degree collision angle. Their two detectors, made of tungsten plates and plastic scintillators, produced in the

The aim of LHCf experiment is the study at the LHC accelerator of the neutral-particle production cross sections in the very forward region of proton-proton and nucleus-nucleus interactions.

Neutral pions, gammas and neutrons production will be investigated during the initial phase of the LHC running, at low luminosity (below 10³⁰cm^-2s^-1).

This study will give important information for understanding the development of atmospheric showers induced by very high energy cosmic rays hitting the Earth atmosphere. Methods which are used to extract information about primary cosmic-ray radiation by means of atmospheric-shower experiments data, depend on the interaction model which is considered in shower development simulations. Using the statistics which can be accumulated in a few hours of data taking, LHCf will be able to check the validity of several interaction models' predictions in proton-proton interaction at an equivalent energy of 10¹⁷eV in the laboratory frame. Kinematical region accessed by the experiment can be improved during non-zero beam crossing angle runs and by moving the LHCf detectors with respect to their initial position by means of a remote control system, in such a way that different forward regions can be covered at different times.

The two electromagnetic calorimeters, placed 140 metres upstream and downstream of IP1 (ATLAS), consist of a scintillator-tungsten sandwich .Total outside dimensions of one calorimeter are 10cm x 30cm x 90cm A schematic is shown.

These measurements, together with the measurement of the total inelastic cross-section (TOTEM), are of paramount importance for our understanding of Ultra High Energy Cosmic Rays atmospheric shower development.

LHCf is the smallest one of the six official LHC experiments, and it has an equally small collaboration of just 22 people from 10 institutes in 4 countries.