Bhabha calibration is not used
for the inner three endcap rings (theta_index = 1,2,3). Instead,
Bhabha-like constants are derived from muon energy deposition in single
crystals. This calibration is done infrequently (e.g., once per year).
The method is documented here.
Muon-based Calibration of Endcap Crystals
This page under construction. Direct questions to J. Ritchie
Quick Link to Muon
Calibraion Results Page ( Table of Constants, Histgrams, etc.)
| Purpose of Muon
calibration is developed for the inner three endcap
ring as an alternative method to bhabha calibration.
- Muons are a source
of constant energy deposition (about 200 MeV).
As a result, they are a check on detector stability.
- Muons deposit energy
uniformly along their paths, so they maybe affected
differently by radiation damage than photons and
electrons if the damage is localized (e.g., near the
- The precision of
this method is limited to the few percent level by the
uncertainty in muon peaks for individual crystals,
but for rings 1-3, this is a substantial
to calibrate inner three rings of endcap
calibration for the endcap is based on the muon
peaks found in the each crystal. Muons
"transfer" the calibration from good EMC regions into
the inner three ring. (Go to Calorimeter
Description and Drawings to check the geometry of EMC.)
- Use muons which hit
only one crystals (Crystals = 1) selected from
rawEnergy(). With this constraint, the muon
peaks become narrower and cleaner.
- Determine the
central value for ring 4 using muon peaks. Ring 4 is used as
the normalization for the calibration since the
radiation damage is similar and the momentum
difference is negligible.
- Calculate factors
for each crystal in ring 1-3 to shift the peak for
that crystal to the central value for ring 4.
Peaks are normalized and scaled to the Bhabha
energy using source and bhabha constants.
- Approximately 100
million events are needed to get enough
Bookkeeping User Tools to select desired datasets.
AllEvents are used for this analysis. It is recommended to
run smaller number of events (~2.5 million) and merge the
- For Run4 data,
BetaMiniApp is used to select events. Modify MyMiniAnalysis.tcl
to turn on
BGFMuMu. (Refer to the linked file for the
example.) Compile and link EmcMuonPeaks.cc
and EmcMuonPeaks.hh. This
will give you a hbook with ntuple containing energy peaks
along with theta and phi angles.
>addpkg EmcCond V00-03-27
- Run muendc3p2.kumac on the ntuple.
The kumac file will plot energy peaks of theta 1
through 5 with gaussian fits. At the end, the kumac
will generates two files; one post
script file (gzip) containing the plots of energy and vfactor,
and a data file which
contains columns of theta, phi, and vfactors.
- In order to calibrate
the vfactors, source and bhabha calibration
constants are needed. They can be found using EmcCond.
Under the Analysis-21 directory, type
- Once the compiling is done, the executable called
"FetchEmcCalChan" will be available. By specifying the type and
the date of calibration desired, this will return the columns of
theta, phi and the constants. This columns contains
constants for all the angles but we are only interested in
theta 1 through 3. We can reformat the data
file using calchan.kumac.
- Three files containing columns of angles and
constants are generated so far; vfactors, source and bhabha constants. formatbhbh.kumac combines those 3
files to be used by mubhbh.kumac.
mubhbh.kumac rescales the vfactors and calculate the new
bhabha-like constants and generates a plot and a data.
- muanl.kumac is also
helpful when comparing the difference between old and new
sets of calibration constants
on Muon Calibration
|The progress of the muon calibration has been
presented at EMC
calibration meetings as "Muon Studies" by Jack Ritchie.
Links to Muon Studies
July 17th, 2002,
August 28th, 2002, September
October 23rd, 2002,
March 12th, 2003,
April 23rd, 2003,
June 18th, 2003.
This page is:
Page author: Natsumi Matsuda