(1) Motivation:

      We did the cosmic ray test for the FHC modules to get the attenuation lengthes of the scintillating fibres.

      Because we want to figure out

      (i) whether there're construction damages of the scintillating fibers,

      (ii) whether we can use these triggers as gain monitor during collisions.

      We use a 5*10 modules of the forward hadron calorimeter (FHC) to do cosmic ray test with a 32 channel DAQ system. Four CTB boxes divided into two groups are taken as outside triggers. One group is near the PMT of the hadron calorimeter, the other is far from the PMT of the hadron calorimeter. With a 16 channel PMT power supply, we checked 5*3 cells group by group. The signals and discriminater outputs of the 4 CTB boxes are put in the first 8 channels of the DAQ system. And the cells of the hadron calorimeter are marked from channel 8. The map of one group is like the following,

   (2) Setup of the FHC cosmic ray test.

    Fig1, front view of the hadron calorimeter.

    Fig2, side view of the hadron calorimeter.

   (3) Earyly data.

   We put the CTB trigger and their discriminator output in the first 8 channels of the DAQ system.

   Fig1, the CTB trigger pulse and discriminator output (from escope). Here Ch1 shows the pulse of one CTB trigger, Ch2 shows the discriminator output of the same CTB trigger and Ch3 shows pulse of one cell of the hadron calorimeter.

   Fig2, the CTB trigger distribution.

   For one group, we checked the signal with no trigger cut. Column is marked from left to right and row is marked from bottom to top. 

   Fig3, signal of column 4 to column 6.

    Fig4, the first column of the group with no trigger cut.

    We fit the pedestal of each cell with a Gaussian function and get the mean from the fit. Then we minus the pedestal mean value for each cell.

    Fig5, ADC values (subtracted pedestal) of the first column.

    We set thresholds above pedestal on the top and bottom of the first column to constrain the cosmic muons only pass through the first column of the group.

    Then we use the CTB outside triggers to constrain the cosmic muons pass near or far from the PMT of the hadron calorimeter.

    After these two conditions, we fit the ADC value with Landau distribution and get the most probable value.

    Fig6, the muon signals of the first column under CTB trigger far from the PMT of the hadron calorimeter.

   Fig7, the muon signals of the first column under CTB trigger near the PMT of the hadron calorimeter.

    From Fig6 and Fig7 we get the most probable value after fitting with the Landau distribution. I fit the ADC value minus pedestal at different distances from the PMT of the hadron calorimeter for each cell with the exponential function, Aexp(-1/L₀ X). Here L₀ is the attenuation length.

    Fig8, the attenuation lengthes of each cell of the first column.

    With similar strategy, we can get the attenuation length of the whole group, and the list is as follows,

   The attenuation length values show good consistency with 190 cm (the attenuation length mentioned in the E864 experiment paper) with errors.

   The work to look through all 5*10 cells to get the attenuation length and gain factors are ongoing.

  (4) Conclusion

   (1) The status of the 5*10 modules of the FHC is good.

   (2) We can use the trigger system as gain monitor during collisions.