Dijet mass

Below is the dijet mass distribution. No cuts on the energy of the Z was done, and the reconstructed Z from muons have mass between 80 GeV and 102 GeV.

The jets were obtaining by reclustering after muon removal from the list of particles and forcing into 2 jets. I just don't understand why such long tails for low mass values. Still investigating. Improving the dijet mass resolution (by improving jet reconstruction) could save some events from the dijet mass cut.

Event selection tuning and Luminosity

The plots I've been showing must be looked at carefully. The selection of events I am doing up to now are "non-standard" and not properly tuned. I still have to check the standard cuts for ZH event selection, together with my cuts, in order maximise the statistics.

One also have to have in mind that the number of events in the samples corresponds to 6.6 the nominal luminosity (L), where L=500fb-1. So, divide the Y axis by 6.6 to get the "correct" number of events. A fine tuning of the selection is very important to get enough statistics of H into c cbar.

Removing further ZZ background

As I showed before the cut on the energy of the Z can eliminate a fraction of the ZZ background (see plot in previous post below). I am trying now other cuts that could improve further the removal of ZZ background.

I am applying the same cuts up to now:

• M_Z between 88 GeV and 94 GeV
• E_Z between 100 GeV and 103 GeV

The plot below shows the dijet mass (jets were reclustered into 2 jets after the muons coming from a Z boson are removed). One can see that the signal and the background are quite distinct.

Applying a cut on the dijet mass, Mjj .gt. 96 GeV, the ZZ background was further reduced. 

Talk at ILD Optimisation Meeting!

Thanks for everyone's help! Here's a link to the talk.

ZZ versus ZH kinematics

I generated+simulated+reconstructed some ZZ samples with centre of mass energy = 230GeV. The files are in DST format. Soon I will  upload them to the grid.

From kinematics the energy of the Z bosons in ZZ process in the centre of mass frame is sqrt(s)/2. But because of the different masses of the Z and the Higgs bosons, the energy of the Z boson should be (s-mZ^2-mH^2)/(2*sqrt(s)). We can see that from the plot of the energy of the Z boson below. The blue line was obtained using ZZ+ZH samples whereas the dashed black is from ZH only. Cuts on the energy of the Z may be worth doing to remove also the ZZ background.

The next plot shows the recoil mass. The different cuts are in the plot (problems using math symbols here).

Z-Higgs analysis

Link to the talk here.

A few question in my head We have four jets: we need to identify two as muons. How do we use the muon ID cuts on the jets, as opposed to on just on RecoParticle? Then how to use the NN cuts to ID the B and C jets?

Some plots

What I've been doing is ID-ing the electrons and then forcing everything else to 2 jets. This means I'd have to do my own jet finding and flavour tagging if using mass reconstruction files in the future.

Variables used in the likelihood cut
The thrust variables don't seem to do much, and the jet energy difference doesn't offer great discrimination. We still need to add the di-jet mass after the 5 constraint fit to this.

Flavour tag likeness for the Higgs sample (using the c-tag)
These plots look fairly good; there is a definite difference between each different plot that should be extractable from the branching ration fit.

Flavour tag likeness for the ZZ sample (both c-tag and bc-tag)
Same here for the ZZ. I've also added the same plot but using the c-with-only-b-background tag, although this doesn't show much (see the next set of plots). There also doesn't seem to be much tagged as c in the c-tag version. I'll have to look into that.

Flavour tag likeness for the Higgs sample (using the bc-tag)
The bc-tag just seems to tag anything that's not a b as a c (not really very surprising since that's what it's trained to do). All the templates (except the b) look pretty much the same, so not very good for fitting to.

Electron ID comparison
The next four plots compare the different electron identification methods. Everything is using a Z Higgs sample with the Z going to two electrons and the Higgs doing whatever it fancies, so there is some neutrino stuff in there as well from e.g. Higgs->WW. There's a total of 43888 events split according to standard model 120GeV Higgs branching ratios.
Note that anything labelled as "Pandora" is using a head version of PandoraPFA from a couple of weeks ago. A new tag has recently been released which claims to have improved electron ID, I'll try and redo the plots with the new version soon.

Di-jet mass of everything not identified as an electron forced to 2 jets
There are no cuts on any of these plots, so some of the high tails should be reduced if I cut out anything where less than 2 electrons are found (see below).

Di-electron mass of everything identified as an electron
I've called this "di-electron" mass but quite often there are more than 2 electrons involved, see the next plot for the numbers. Note that I forgot to put a cut on the number found, so the spikes at zero are when 1 or no electrons are identified.

Numbers of electrons found
The cheated electron code takes the Monte Carlo Z daughters and uses the LCRelation collection to match them to reconstructed particles. If more than one reconstructed particle is related to a particular electron then they are all lumped into one "jet" and the combined four momentum used for the cheated electron. As such I have no idea how it can find more than 2 (let alone 6?). I'll have to look into it when I get time. Addendum 06/Aug/08 - The Higgs sample has Higgs to ZZ, hence the possibility of 4 or 6 electrons from Zs. Doh!

Recoil mass using the electrons found
For this the initial four momentum was assumed to be a consistent (250,0,0,0); so you can clearly see the beam effects screwing up the plot. Have a look at one of my earlier posts to see how I simulated beamstrahlung; basically it's just a rough (over)estimate using 500GeV beam parameters.

Tag plots for B-jets

Tagging plots for true C jets

Sorry about the sideways!
Questions: why is the C-tag bad? Do we use the BC tag for these events?

Tagging plots for the ZHiggs sample

These plots are found using the Durham_4Jets collection. So two of the jets represent the muons.

Electron cut efficiency

The change due to new detector model is seen in the ratio of Ecal energy and the total energy, due to which we have changed our electron cuts. Now it is
1) Ecal/ETot = 0.9
2) ETot/p = 0.7

So with the new detector model, above cuts and more statistics, the efficiency for momentum and cos theta is here

Useful LCIO commands

Some time ago, Mark had problems with a large lcio file. Now I have the same problem. I found on the web the command

lcio split -i file.slcio -n 1000

that splits the file in chunks of 1000 events.

For more LCIO comands, see here. 

z-hisggs preliminary results (2)

Efficiencies:

• Ecm = 230 GeV: 17958 Z boson candidates reconstructed out of 20000 generated. (90%)
• Ecm = 250 GeV: 18191 Z boson candidates reconstructed out of 20000 generated. (91%)

z-higgs preliminary results

Here are some plots produced using the muon selection from Hajrah to tag the muons in the PandoraPFOs collection.
Additional cuts: momentum of the lepton from Z greater than 20 GeV; mass of the Z boson between 70 and 110 GeV.
Recoil mass reconstructed using the nominal centre of mass energy.

The black and the red lines on the plots correspond to Ecm = 230 GeV and Ecm = 250 GeV, respectively. The samples used are described here.

Efficiency Plots with more statistics

After applying the Muon cuts, the efficiency plots for Momentum and Costheta are shown below.
Please follow the link here:
https://www.wiki.ed.ac.uk/display/ILC/Hajrah+Tabassam

Edinburgh z-higgs samples

Edinburgh Z-higgs samples, e+e- -> Z h
Z -> mu+ mu-
h -> anything

The samples are located on the GRID at
/grid/ilc/users/edinburgh/data/z-higgs

Up to now there are 2 samples,
- Ecm = 230 GeV,
- Ecm = 250 GeV,
with 20000 events each. Both reconstructed (still being uploaded) and DST files are available.

More details can be found here.

Sample grid locations

I've copied most of my samples to the grid, and started a script running to copy the rest. Everything is under the directory:

/grid/ilc/users/phmag/LCIOOutput/ZHiggsAnalysis

With currently three directories:

WW-anything
ZH-eeXX
ZZ-eeJetJet

The files should be self descriptive from the filename. I was going to write how many events etcetera there are here but I've rather stupidly left my log book at home, and I'm away from tonight. There are only 10000 WW events (in 2 files), other than that everything should be whatever the numbers are for 500 fb^-1. Higgs to bbbar is split over 4 files, and the ZZ stuff is split over 100 files.

The detector is LDC01_05Sc at 250GeV, but with SEcal03 instead of SEcal02 (there was a problem with SEcal02, I can't remember the details). Beam effects were simulated by forcing the centre of mass energy in Pythia to match the energy spectrum from PandoraPythia (with the 500GeV beam parameters). That's about all I can remember for now, I'll check my log book when I get back.

Installing OpenScientist

OpenScientist is a full C++ implementation of AIDA. I was having big problems using Java on 64 bit machines reliably so switched to this instead of AIDAJNI.
To install, first download from openscientist.lal.in2p3.fr. I went for the "batch" version, which is basically the simple version without any GUI stuff for batch processing.
The installation instructions weren't particularly to the point so I'll recap what I did briefly (obviously change the version number if appropriate):

unzip osc_batch_source_v16r4.zip
cd OpenScientist/v16r4/osc_batch/v16r4/obuild
source setup.sh
./sh/build
./sh/build_release

I think that builds everything (there is more to OpenScientist than just an AIDA implementation), but it's easier than figuring out which bits you actually need.

To use it with the lcio software you need a CMake module. I wrote one with all the library and include directories hard coded into it; it would be nice if I wrote a proper self-detecting one but I haven't had the time. You can find out the compiler flags for AIDA with the utility "<location>/OpenScientist/v16r4/osc_batch/v16r4/bin_obuild/osc_batch/v16r4/bin/aida-config".

My module is here, obviously you'll need to change the directories to match your system. I called the module FindBatchLab.cmake, so then all you have to do is put that module in with the other CMake modules and change the dependencies in your projects CMakeLists.txt file from "AIDAJNI" to "BatchLab".

IMPORTANT NOTE FOR JAS USERS - BatchLab puts empty histograms/clouds etcetera into the AIDA file, which JAS doesn't like (e.g. if you create a histogram and didn't fill it with anything). I modified the file "OpenScientist/v16r4/BatchLab/v1r2p1/source/XML/XML_DataWriter.cxx" to this. Copy my file over the original before building if you want to use JAS to analyse your AIDA files. The xml schema says there should be at least one entry for clouds/histograms/etc, so I think the JAS way is the correct way.

Minutes of Meeting 30/6/08

Present: Hajrah, Roberval, Victoria, Mark, Joel (Clare is still in a muddy field)

• Mark's samples for 500 fb^-1 of ZH at 250 GeV (m_h = 120 GeV, Z->ee) have finished running through simulation and he is checking them. He used LDC01_05sc. The samples will be made accessible on the Grid and a post made to this blog. Z->µµ samples can also be made.
• Clare has been working on getting a working suite of software on the Bristol 64-bit machine (Roberval has successfully compiled the new version of MARLIN on the Edinburgh machine in 32-bit mode)
• Roberval has been writing a processor to use the muon ID cuts to tag RPOs
• Hajrah is looking at electron and muon cut ID efficiency as a function of θ and momentum, but needs bigger samples
• Victoria only has a few more weeks before her leave commences
• Mark has been encountering problems reading in large (~10 GByte) LCIO files. No-one knows of any physical limit, but he will split the files up in future.

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