WW scattering in ATLAS.

Our goal is measure WW scattering vs CM energy from threshold up to as high as possible.

Organisational Stuff

Make accounts at Manchester for code sharing ACTION Brian and Jon

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

Sarah has pretty much finished this except:

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.

Comments from Sarah:

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.

The smearing will be done on cells, though I don't know what value to use for the constant term, since we want it to be comparable to smearing on jets.

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.

We were using: ?

Rome used: the parameters given on this page

ACTION Sarah and Simon

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).