WW scattering in ATLAS.
Our goal is measure WW scattering vs CM energy from threshold up to as high as possible.
Organisational Stuff
- Planned/suggested phone meetings.
- Make accounts at Manchester for code sharing ACTION Brian
- Archive code from note and paper. ACTION Sarah, Jon
- We want a shared code repository which allows us to to co-develop in reasonable privacy but also allows the checked out version to build/link against the ATLAS code. Action: Pete
Mailing list now available: atlas-ww@hep.ucl.ac.uk You can
browse the archived mails (but at the moment only from UCL machines).
ATLAS note
atlas_ww.ps: Latest draft.
Outstanding issues
- The AtlFast data was lost in a disk crash, but can be regenerated. Simon Head will be asked regenerate it. This should be without pileup, since the pileup is unofficial/undocumented, and not a big effect anyway. We can just make a comment in the text.
- The pileup we used is not a big effect as long as a cell threshold of 1GeV for low luminosity and 2 GeV for high luminosity is applied. Without these it is a big effect. This is now stated in the text. I guess though we should apply the threshold at 2 GeV for all the data.
- The smearing will be done on cells (twoers, surely?). What value should we to use for the constant term, since we want it to be comparable to smearing on jets? Reply from Jon: I don't think one can completely correctly reproduce smearing on jets by smearing towers whatever one does. And in fact, smearing cells is a better approximation to reality. If we take the radius-proportional term (by the the way, this proportionality seems to be based on a straight line drawn through two points, see page 272 of the TDR) and apply it to the tower radius, that should get the noise etc ok in that twoer, but it will neglect the noise in other towers with no true energy which may have contributed to the jet. I think the noise suppression threshold saves us - it should remove this as wellas the constant term. And Sarah has also tried increasing the constant term and shown we are insensitive to it. So I think this argument and holds and is the best that can be done at present, until there is an approved cell smearing in ATLFast.
- Underlying event model: should we use the same parameters as in the Rome samples? Or our own? Reply from Jon (second attempt, 22 Oct) I think we should use the same as the Rome sample; this is a reasonable set of parameters which was derived from Tevatron data. Other sensible options would be to use whatever is approved for the new production (is this decided yet?), or to use PYTHIA Tune A from Rick Field (as described in the
HERALHC TeV4LHC workshops. The reason I say go with the Rome parameters is that is will facilitate conmparison between ATLFast and full simulation results, and yet we don't have to wait for the new DC3 parameters. If the new DC3 parameters are already known, I would suggest using them, for the same reason.
- The efficiencies as purities need to be discussed/clarified.
- Text to be checked and finalised ACTION Jon, Brian and Sarah
Theory
We need to check that we are generating W+W-, W+W+. We would also
like to generate WZ and ZZ.
We would also like to cross check with the Montreal code.
ACTION Brian and Jeff.
Trigger
(FLT, HLT, offline selection)
Document which trigger chains the signal should get through etc here.
ACTION Stathes
Selection cuts
Action: Sarah to document what she actually does in the full sim analysis
The code is in ... . It started from the
AnalysisExamples package.
electron
The standard preselections available in atlas are
here. For electrons, I currently use:
- ET>10GeV,
- isolation cut of 5GeV in dR=0.3
- isEM() & 0x07FF == 0
muon
To be selected, a muon must be highPt and have
- chisquared < 20.0,
- Muon Isolation cut of 5GeV.
- pT > 5GeV
- eta < 2.7
missing ET
The missing ET used is MET_Final, which is calib+muons+cryostat correction.
Hadronic W mass resolution
In full simulation I just use the highest pT jet.
pile up, jet finder dependence.
subjet cuts
cal granularity?
How to run it practically - produce an ATHENA algorithm
which takes a jet (AOD?) and produces a y cut array.
Action: Pete
top mass resolution
pileup and jet finder dependence
This works in
AtlFast & at hadron level. Not yet working in full simulation.
tag jets
how well are they modelled?
how well is the rate known?
How can it be checked?
hard pt
how well is it modelled?
can it be checked?
minijet veto
is it really useful?
how well is it understood?
use new underlying event models/tunes.
background generation
what samples do we need? which generators?
we need W+jet and ttbar samples with a ptmin of about 250
GeV. However,
to get decent luminosity will require a lot of CPU so we should put this in
as a standing request to the SM and exotics groups, but not sweat about generating it
ourselves just yet - there is a lot of work to do on the signal.
detector simulation
how much with
AtlFast, how much needs full simulation?
Signal Generation
Sarah and Stathes can both generate signal with the modified pythia routine.
Continuum is the best default but we can look at other scenrios too.
PYTHIA Signal Production:
- Stathis has produced 60K events of the 1 TeV Scalar and Continuum Signal channels.
- The evens were generated using PYTHIA and the modified FORTRAN routine.
- There are 15 files of 4K events each in pool format. There can be in simple ntuples. If someone needs it let Stathis know.
- The files are located at UCL under: /unix/atlas1/sstef/wwScattering/Gene/ We must decide a common place to store them together with the Manchester samples.
- In the same directory you can find the jobOptions file (sampleJobOptions_pythia.py) for generating these events.
We'd also like some high PT hadronic Ws Foundation samples
Action: Sarah to ask SM and Exo convenors
Stathis is looking at it. Will report on that as soon as there is an action.
Maybe we should we aim for someone to give a talk at next UK SM meeting (November 30).
Code Repository
CVS directory: WWscattering
recipe:
setup.sh your home requirements file.
alias gpcmt="export CMTCVSOFFSET=groups/WWscattering;cmt"
alias offcmt="export CMTCVSOFFSET=offline;cmt"
to check-out a tagged version:
to check-out the head version
gpcmt co WWscattering
to check-out from the offline packages:
offcmt co
*********Guidelines for handling the CVS repository of the package
1. sourse setup.sh in your working area
2. alias gpcmt="export CMTCVSOFFSET=groups;cmt"
3. gpcmt co WWscattering (if you want to check out the head version) or
gpcmt co -r WWscattering-XX-XX-XX WWscattering (if you wanna check out the XX-XX-XX tag)
4. Make the changes/fixes. Say for example that you have fix something at src/wwFrameAnalysis.cxx and add a new file src/aNewFile.cxx
At one level up of the cmt directory:
5. Update the Log File of the changes you've made.
6. cvs add src/aNewFile.cxx (do that for all your addings!)
7. cvs update -A (to update the fixes...)
8. cvs commit -m 'A message to describe the main change'
If you want furthermore to give a tag, go one level up of the tag that is being used (WWscattering-XX-XX-XX) and do:
9. cvs tag WWscattering-YY-ZZ-XX
Useful Links and Papers
-- JonButterworth - 29 Sep 2005
-- SarahAllwood - 13 Oct 2005
-- StathisStefanidis - 18 Oct 2005
-- StathisStefanidis - 04 Nov 2005