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name="JonButterworth" |
WW scattering in ATLAS. |
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- 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
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< | Mailing list now available: atlas-ww@hep.ucl.ac.uk You can browse the archived mails (but at the moment only from UCL machines). |
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> | Mailing list: atlas-ww@hep.ucl.ac.uk You can browse the archived mails (but at the moment only from UCL machines). |
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ATLAS note |
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< | atlas_ww.ps: Latest draft. |
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> | atlas_ww.ps: Latest draft 5/11/05 |
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Outstanding issues |
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- 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.
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- The AtlFast data was lost in a disk crash, but can be regenerated. 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.
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- 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.
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- 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.
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- The smearing will be done on towers. We can't completely correctly reproduce smearing on jets by smearing towers whatever we do. 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.
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- 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. |
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- 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 comparison 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. (Rome used: the parameters given on this page)
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- The efficiencies as purities need to be discussed/clarified.
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- Efficiencies and purities were discussed in the meeting on Thursday by Jon, Sarah, Stathes & Simon. Propose a two stage "measurement". First define a cross section which is (a) physically well defined and (b) in a kinematic region where ATLAS has reasonable acceptance. Then, once this is measured, correct it back to the inclusive WW rescattering cross section. The reasoning is described in the 5/11 version of the note (above) section 4. The physical cross section should be defined by the pT and eta of the W's, the fact that one is leptonic and the other hadronic, and by the kinematics of the tag jets. Note this is different from what we proposed on Thursday. I think we can use the W kinematics rather than the leptonic ones because the W decay is very well understood. And I think we need the tag jets in the cross section definition because otherwise the cross section would also include Drell-Yan type events. (We can't define the physical cross section in terms of an incoming W!).
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- Text to be checked and finalised ACTION Jon, Brian and Sarah
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| | Theory
We need to check that we are generating W+W-, W+W+. We would also |
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< | like to generate WZ and ZZ. |
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> | like to generate WZ and ZZ. (Sarah did this check. We are.) |
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We would also like to cross check with the Montreal code. |
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< | ACTION Brian and Jeff. |
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Trigger |
| | -- StathisStefanidis - 18 Oct 2005
-- StathisStefanidis - 04 Nov 2005 |
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| META FILEATTACHMENT |
attr="" comment="" date="1130232290" name="atlas_ww.ps" path="atlas_ww.ps" size="1261410" user="JonButterworth" version="1.2" |
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| META FILEATTACHMENT |
attr="" comment="" date="1131221590" name="atlas_ww.ps" path="atlas_ww.ps" size="1256345" user="JonButterworth" version="1.3" |
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