The Measurement of Forward Particle Production in LHC Yasushi Muraki Solar-Terrestrial Environment Laboratory Nagoya　University, Nagoya, Japan at 17th Rencontre de Blois, 5/16/2005

Measurement of Photons and Neutral Pions in the Very Forward Region of LHC 1. Scientific Purpose The main purpose of this experiment is to establish the production cross-section of pions at the very forward region in proton-proton interactions at the highest energy region, using the highest energy accelerator in the world. It has been dream of cosmic ray physicists for a long time.

2. Experimental Details To realize above purpose, we propose to install a compact calorimeter in front of the beam intersection at 140m away. It would be the smallest experiment using the largest accelerator in the world. We require a rather low luminosity operation, say 1028 -1029 and rather small bunches in a ring, say ~23 in a circle.

3. Scientific goals By this experiment, we will be able to establish a very important data point, which will be very useful to understand for not only the highest energy cosmic ray problems, but also for establishing the forward code of the GEANT 4 programme.

The LHC very forward region

The TAN assembly for the luminosity monitor

Where we are going to install a or two small calorimeter(s)

We would like to install three shower counters with a dimension 2x2, 3x3, 4x4 cm2 and 43 radiation length respectively.

We can measure the region of photons with XF>0 We can measure the region of photons with XF>0.05 by this experiment.

The energy resolution is estimated by the Monte Carlo calculations The energy resolution is estimated by the Monte Carlo calculations. The maximum number of shower particles is expected as 15,000 e-.

The energy resolution has been estimated by Monte Carlo method by Kasahara san and it will be estimated as to be around 2% @ 5 TeV.

Two production cross-sections were assumed for Monte Carlo : A and B.

We will be able to check different models

Why information on very forward region is important for cosmic rays?

Absolute energy calibration can be made by neutral pion peaks

Neutron detection and K0 background *Red: K0 *Black : Neutron

We will be also able to get neutrons !

Present status of the TAN at the IP4 CERN 2005/4/25

We have made a similar detector what we had proposed and made a test experiment using NA beam line of CERN. The detector was bombarded to the electron, muon and proton beams with energies 50-250 GeV. The position of the beam incidence was measured by the silicon detector.

The sum up result of shower particles for 200 GeV electron beam

Left : Experimental results, Right : MC

Conclusions resolve the puzzle of highest energy cosmic rays. (1) It is sure that the experiment LHCf can resolve the puzzle of highest energy cosmic rays. (2) Furthermore the data will resolve the composition of cosmic rays around 1019 eV. (3) The test experiment shows that the proposal works as expected by M.C. (4) We are waiting an official approval by the LHCC.It will be around October. (5) Then we will get the answer in X-days of 2007. Just a dew our data-taking. (6) A joint data-taking with ATLAS is now under discussions.

The background and Photon signals Red Photons Black beam collision (background)