Calorimeter calibration

Hajrah and Alex, from Edinburgh, found in their analyses a mass distribution of the Higgs quite high and wide when the mass is reconstructed from the b jets. That led us to think if there is a problem with the calibration. As an exercise I ran the PandoraPFACalibrator processor and comparing the processors SimpleCaloDigi and MokkaCaloDigi, using the detector model LDC01_05Sc I found that for the ECAL calibration the energy distribution of 10 GeV photons is fine for both processors. But for the 10 GeV KL using SimpleCaloDigi the energy distribution is wide and peaks at an energy higher than 10 GeV.

Here are the plots for the energy distribution of the

• photons 
  
• kaons
  

The solid black line comes from MokkaCaloDigi; dashed red line comes from SimpleCaloDigi.

We are using SimpleCaloDigi in our reconstruction. That might be the reason of the wrong mass distribution of the Higgs candidates. The next step is to check the calibration constants for LDC01Sc, as this is the model used for our samples, change to MokkaCaloDigi and see if the results improve.

Minutes of Meeting 15/1/08

Our first regular meeting was held at 4pm on Monday. The main points were:

• Mark's Plots (see previous entry): number of jets and mass of the Z as as function of K_T cut. Things look sensible in the limits, but he has discovered a bug that can double count if more than one MC particle is in the same jet (this gives the peaks at m_Z=180 GeV etc.)
• Energy: it was agreed to make future samples with c.of.m energy 250 GeV as specified in the benchmarks
• Effort: Mark is working full time, with support from Clare. Victoria and Robervaal are working on other things at the moment but should start ramping up soon. Hajrah is coming up to speed, and will start looking at muon ID. There is also an undergraduate at Bristol who will look at electron ID, and an undergraduate at Edinburgh who will be asked to make a short presentation soon.
• Next Steps: Mark's priority will be to assemble all of the machinery for a crude analysis, so we can see where the work needs to be done in tuning etc.
• Future Meetings: We will switch to 1pm on Mondays in future. Next meeting is next week.

Plots for the meeting.

Here are some plots I'm going to talk about in today's meeting. I'll write something about them in the blog later, but the meeting starts in 5 minutes so I don't have time now.
Things as a function of kT up to 0.01 and up to 1.5. Note that the second set of plots has a double counting error if the positron and the electron are in the same jet (so the Z mass plot is double what it should be), I'm running up a corrected plot but it's not finished yet.

Addendum 15/Jan/08
Here's the corrected plot for the kT values up to 1.5, and also one for kT values up to 5*10^-4.
The reconstructed Z mass peak is still very low; I guess it will peak when every particle is in its own jet since the extra reconstructed neutrals are double counting energy (the charged particle gets its energy from the track momentum, so any counting of its clusters is double counting). You can sort of see this because the plot seems to spread higher more so than lower, although you can only see it for the first kT bin; I'm having "issues" getting Paida to rotate the plots appropriately.
I'll reverse the plots, i.e plot the kT as a function of the other stuff which should give me a decent kT cut to work with. I'll try and get some rudimentary electron selection done by the end of the week and then move on to the rest of the analysis framework, leaving someone else to worry about the details.

PandoraPFA Calibration

I had a go at the Pandora calibration, it's well documented and seems straight forward enough. I've put a script for a Grid job in the subversion repository to create all the samples necessary so it can be repeated if the detector changes (https://svn.phy.bris.ac.uk/svn/ilc_z_higgs/MarksStuff/PandoraCalibrationEventGeneration).
The files I generated for LDC00SC are in "/grid/ilc/users/phmag/LCIOOutput/PandoraCalibration".

I've not done any fitting with Root before, so for a first pass just centred the histograms by eye.
The constants I came up with are:

MokkaCaloDigi:
CalibrECAL=27, 81
CalibrHCAL=27.3

PandoraPFA:
ECALMIPcalibration=230
HCALMIPcalibration=31.5
ECALEMMIPToGeV=0.0045
ECALHadMIPToGeV=0.0045
HCALEMMIPToGeV=0.0353
HCALHadMIPToGeV=0.0353

I'll re-run the reconstruction of all the Z Higgs samples with these constants tomorrow.