Analysis Meeting 4 (5/04/05)

1) Preliminary Cross-Sections for Carbon (click here)
and LD2 (click here).

2) HMS Calorimeter Efficiency calculated for all runs (click here )

3) Monte Carlo Comparisons for Carbon w/ Radiative
Corrections (click here)

4) Beam Position Offsets

Beam Position Offsets

After calculating the MC Comparisons we examine the Y target histograms from the Data and MC and compute
the Mean for each (attach. 1).  We now define variable Delta_Y as the difference btw these two mean values as:

Delta_Y = Y_Data - Y_MC



By analyzing the geometry of the target (see attach. 2) we find this can also be written as:

Delta_Y = Delta_X * Cos (Theta) + Delta_Z * Sin (Theta)



where Delta_X is the offset of the beam, Delta_Z is the offset of the HMS, and Theta is
the HMS angle.

This can be rewritten as:

Delta_Y / Cos (Theta) = Delta_X  + Delta_Z * Tan (Theta)

By applying a linear fit we should be able to find the X and Z offsets as
the y-intercept and slope respectively.

However, we also need to factor in the "mispointing" of the HMS.  From recent surveys and
studies we've found that there is a slight uneveness on the HMS rail tracks that result in the
HMS Optical axis not quite pointing back to the pivot.  This causes an offset that
can range from 0-2mm and varies with angle.     

After we compute the linear fit with the mispointing (attach. 3), we find:



Delta_X = -1.11 (mm)
Delta_Z = 1.56 (mm)

Factoring these offsets into our MC, and refitting our data (attach. 4) we obtain:

Delta_X = .34 (mm)
Delta_Z = -.49 (mm)

 

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 Maintained by Jim Steinman