Determination of relative gains BTOW gains based on MIP peak for the purpose of balancing HV for 2009 run

Procedure:

• use fitted 03 MIP peak analysis (TPC tracks, 2008 pp data)
• find average MIP value for 40 eta bins
• West barrel:  preserve absolute average MIP peak position in the , compute gain correction to equalize all towers at given eta to the average for this eta
• East barrel: enforce absolute average MIP peak to agree with the West barrel, correct relative gains in the similar way.

In this stage of calibration process 4430 towers with well visible MIP peak were use. The remaining 370 towers will be called 'blank towers' . There are many reasons MIP peak doe snot show up e.g. dead hardware. ~60 of the 'blank towers' are 02 BTOW swaps ver=1.3- as identified earlier and not corrected in this analysis.  

Fig 1. Left: MIP peak (Z-axis) was found for 4430 towers shown in color. White means no peak was found - those are "blank towers".  Right: eta-phi distribution of blank towers.  On both plots East (West)  barrel is show on etaBins [1-20], (21,40).

The (iEta, iPhi ) coordinates were computed based on softID as follows:

   int jeta= 1+(id-1)%20; // range [1-20]
   int jphi= 1+(id-1)/20; // range [1-240]
   if(jphi<=120) { // West barrel
      keta=jeta+20; kphi=jphi;
   } else { // East barrel
      keta=-jeta+21; kphi=jphi-120;
   }

Fig 2. Average MIP position as function of eta bin. West-barrel gains are higher even of average.

Gain corrections (GC₁) were computed as
     GC₁(iEta,iPhi)= MIP(iEta,iPhi) / avrMip(iEta)

For the East-barrel we used values of avrMip(iEta)from symmetric eta-bins from the West barrel.

If computed correction was between [0.95,1.05] or if towers was "blank"   GC₁=1.00 was used.

Fig 3. Left distribution of gain corrections GC₁(iEta).  Right: value of   GC₁(iEta,iPhi).

Attached spreadsheet contains computed  GC₁(softID) in column 'D'  together with  MIP peak parameters (columns H-P) for all 4800 towers. Below is just first 14 towers.

Used .C macro is attached as well.