resolution

H missing mass plots 04/24/06

Better agreement was seen in the hydrogen missing mass plots after changing the beam energy offset. The beam energy 4.021 GeV was changed to 4.020 GeV and the beam energy 5.012 GeV was changed to 5.0137 GeV. The missing peaks now all have zero shift between simc (blue) and data (red). (NB ignore the green lines and plots)

Wire chamber resolution 04/19/06 (rev. 04/21/06)

As reported earlier, the resolution of SIMC seems to not have great agreement with the data (the data offsets are also a little off too, but I will work on that later).

I used the corrected singles plots of elastics data to match the wire chamber resolution to the data. The corrected singles is the track momentum minus what can be calculated from the track angle. Therefore, the HMS and SOS resolutions can be separated.

Plots using the default resolutions

Plots with SOS*1.05 and HMS*1.7

The factors were applied to resmult in mc_sos_hut.f and mc_hms_hut.f, respectively.

However, after running SIMC with the production runs, iterating the elementary pion cross section, etc. The resolutions still do not match (although the height of the simc peaks have been reduced slightly). Furthermore, the resolution at the highest Q2 looks pretty close, where the WC rates are less than at the larger Q2. So, it seems that two-track effects in the resolution is significant.

After increasing the resolutions a lot more, including the scalers of the hodoscope planes neares the wire chambers to estimate the 2 track rate, and adjusting the HMS momentum offsets, the following missing mass plots were obtained. Details of the work follows.

The final resolutions were

HMS

    tmpran = grnd()
*    tmplim = 0.15 !original setting, fraction of events with >6 hits.
    tmplim = benhsrtrack*4.0e-6    !Added for pionct 4/19/06
    if (tmpran.lt.tmplim) then
    resmult=3.2            !resolution is 3.2x worse (both DCs)
    else
    resmult=1.0
    endif
    resmult = resmult*2.0! Added for pionct 4/19/06

SOS

    tmpran = grnd()
*    tmplim = 0.15 !original setting, fraction of events with >6 hits.
    tmplim = benssrtrack*4.0e-6    !Added for pionct 4/19/06
    if (tmpran.lt.tmplim) then
    resmult=3.0            !resolution is 3.0x worse (both DCs)
    else
    resmult=1.0
    endif
    resmult = resmult*1.15 ! Added for pionct 4/19/06

The new variables starting with "ben" are the normalized (counts/s) scalers of the hodoscope planes nearest the WC's.

So, the resolutions have been increased by A LOT!!!! For example, the scalers were around 100,000 counts/s. For this case, the HMS wc resolution was multiplied by a factor of 3.3 (on average), and the SOS wc resolution was multiplied by 1.8 (on average).

The HMS momentum offsets were fit using the production data points. The vertical axis is the required change in the HMS momentum (units of 0.1%), and the horizontal axis is the central HMS momentum (GeV). Using the HEEP data, the original offsets were -1.5 for the first three points and -1.8 for the last two points. The fitted line represent the offset

hpcentral = hpcentral* ( 1. + (-4.85+0.872*hpcentral)/ 1000. )