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LHC Higgs Cross Section: Charged Higgs meeting
22/02/2010, 14:00
Present: Elias Coniavitis, Patrick Czodrowski, Martin Flechl, Michael Krämer, Sami Lehti, Allison McCam, Michael Spira, Reisaburo Tanaka
Chair: Martin Flechl
Minutes: Martin Flechl
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Please have a look at the slides. The following only summarizes additional discussions.
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1. Intro (Martin)
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2. Theory Overview (Michael)
Reisaburo/Martin: Group is not supposed to discuss analysis strategies; first task are inclusive distributions, then differential incl. k factors
Martin: ATLAS uses Matchig and Pythia for the H+ signal
Reisaburo: slide 5 - differences 4FS vs 5FS look larger.
->Michael & Michael: indeed... 5FS includes Delta b corrections, 4FS does not
Michael K: plot has been corrected in current version of slides.
Reisaburo: different low-mu behavior for 4FS and 5FS... why?
->Michael: Yes... 4FS as expected, but 5FS unusual. Should try to get Tilman's opinion on this.
Martin: Investigating differences 4FS vs 5FS important in the context of this group.
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3. CMS Status (Sami)
Martin: Slide 4 - for 7 TeV?
-> Sami: Yes
Michael K: All work-in-progress or already done?
-> Sami: in progress
Martin: Which tools used for xsec, BR?
-> Sami: Numbers from Tilman; CMS top xsec; BR(H+ -> taunu)=1 assumed for low mass
Sami: Signal generation - Pythia6+Tauola, Bkg: Madgraph, Alpgen
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4. ATLAS Status (Martin)
Michael S: Systematic uncertainties for BR seem large
-> Martin: Yes, they are very conservative limits; and not result of a rigorous investigation. Should ask Sven for an updated opinion.
Michael K: slide 8: due to large uncertainties for gluons at large x
Michael K: slide 9: used MRST2004 as no newer 4FS-pdfs available. Have now a private version of MSTW2008 4FS PDFs, will redo exercise. b PDFs etc might not have been optimally described in the old version.
Michael S: slide 11 - same xsec for both H+ masses??
-> Martin: This is normalized to the 14-TeV cross section, to get scale factors
Michael K: Any idea how appropriate adding incoherently H+ from ttbar and heavy H+ cross sections?
-> Martin: Yes, from recent gb->tH+ MC@NLO paper. Typically smaller than our uncertainties.
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5. Discussion
Martin: procedure could be 1) agree on tools, 2) obtain numerical results, 3) investigate these: comparisons between tools, uncertainties, differential distributions, ...
Michael S, Reisaburo: Higgs BR, also for MSSM, done by BR group. But not t->bH+
-> Martin: Need to make sure Higgs and top BR and Higgs xsec are treated consistently (delta b corrections etc)
Michael S: SUSY corrections factorize... can do that later
-> Michael K: Yes, let's start with the QCD part
-> Martin: Ok, but eventually need to also provide numbers for specific benchmark scenarios like mh-max
Michael S: HDecay implements NNLO Delta b, only 1-2% scale uncertainties (compared to 10% at NLO). Important esp. for BR.
Martin: Will 4FS ever become public code?
-> Michael & Michael: not secret - but should only be run in close contact to experts, thus prefer to only share it upon request.
Michael K: Need to check if MSTW private 4FS PDFs will be public on time so that we can show results.
Reisaburo / Martin: 7 TeV highest priority; and setting up machinery to look at other sqrt(s)
Michael K., Michael S., Martin: For Freiburg, would be nice to have 4FS and 5FS grids. Need to start thinking about t->bH+ and delta b corrections as well, in close touch with MSSM neutral and BR groups.
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Action List:
1. Produce 4FS grid (Michael K)
2. Produce 5FS grid (Tilman)
3. Start thinking about t->bH+ and discuss with MSSM neutral and BR groups
4. Contact MSTW to have PDFs public (Michael K)
5. Set up an email list for our subgroup (Martin). Please send a mail to Martin if you would like to be included in H+ email discussions.
Next meeting: probably in about 4 weeks, but will fix ad-hoc when we have something to discuss
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