lvl1 rates & h hh4b
Post on 24-Jan-2016
35 Views
Preview:
DESCRIPTION
TRANSCRIPT
LVL1 rates & Hhh4b
Erik Brubaker
U of Chicago
September 7, 2006 FTK Meeting 2
Outline• Almost-final word on LVL1 jet rates.
• Understanding cross-section for Hhh4b process.
• Talk descoped due to UC Tier2 going down last night…
September 7, 2006 FTK Meeting 3
Jet rates from Sherpa• Check different ME
combinations, kT,cut values to balance stats/resources, and to estimate systematics.
• LVL1 rates scatter in 40-80 Hz.
• “LVL2” rates require 4 tags, have units of mHz! Not too interesting as is.
SampleLVL1 4jet(40)
rate@1033 [Hz]
LVL2 4tag rate@1033 [10-3 Hz]
2->2+3 @ 10 38.5 ± 4.4 0.2 ± 0.2
2->2+3 @ 25 47.5 ± 1.0 3.0 ± 2.9
2->2+3 @ 50 50.7 ± 0.3 0.8 ± 0.4
2->2+3+4 @ 10
42.0 ± 22.7 0.0 ± 0.0
2->2+3+4 @ 25
65.9 ± 3.8 0.0 ± 0.0
2->2+3+4 @ 50
56.2 ± 0.6 0.4 ± 0.2
2->3 @ 10 58.4 ± 2.3 0.1 ± 0.1
2->3 @ 25 58.7 ± 0.4 0.3 ± 0.0
2->3 @ 50 66.7 ± 0.2 0.8 ± 0.1
2->3+4 @ 10 75.2 ± 32.5 0.0 ± 0.0
2->3+4 @ 25 82.8 ± 4.0 18.7 ± 18.6
2->3+4 @ 50 73.7 ± 0.6 2.3 ± 1.3
September 7, 2006 FTK Meeting 4
Cross-check: jet rates from Alpgen• Samples from
Ambreesh/SUSY group.• ALPGEN light jet
samples only.– LVL1 rates slightly
underestimated• Total rate lower than, but
on the order of, Sherpa results.
• Caveat: 4- and 5-jet samples ntupled with 0.7-cone jets—inconsistent with parametrizations…
SampleLVL1 4jet(40) rate@1033 [Hz]
3 jet 8.79 ± 0.03
4 jet 15.71 ± 0.01
5 jet (incl) 9.64 ± 0.02
Total 34.14 ± 0.04
September 7, 2006 FTK Meeting 5
Cross-check: jet rates from Pythia• Check against Pythia dijets
• Generic QCD incl heavy flavor
SampleLVL1 4jet(40) rate@1033 [Hz]
pT > 50 GeV 95.0 ± 11.9
So…
1. Consistency among models?
2. All are consistently lower than TDR rate:200 Hz for 4j@90 GeV, where 90~=60 inour calibration…
Caveat: DefaultPythia settings forUE etc. have beenunstable…
September 7, 2006 FTK Meeting 6
Systematics on LVL1 jet rates• Variations in ycut, ME configurations in
Sherpa– RMS of the 12 sample results, weighted by
reported stat unc.: 12%
• Differences among generators– Alpgen lower, Pythia higher with caveats:
30% for now
• Additional possible factors—need to check explicitly?– PDFs
– UE/MPI
– Parametrizations
RMS=13.1
RMS=7.5
September 7, 2006 FTK Meeting 7
LVL1 rates conclusion• Need to finish checking effect of UE/MPI in Sherpa,
also different pythia settings (MWT2 died on me last night).
• Run this by ATLAS trigger gurus.– Any similar recent studies?– Difference w.r.t. TDR understood?
Recommendation for FTK studies:
Use Sherpa sample with best combination of statistics,ME configuration, and kT,cut for your proposed thresholds.(Best to try more than one.)
Use my machinery to calculate rates for a range of thresholds.
Assign 35% uncertainty on absolute rate.http://hep.uchicago.edu/~brubaker/ftk
September 7, 2006 FTK Meeting 8
Example LVL1 rate scan
Require 4 jets:1st & 2nd at cuton x-axis;3rd & 4th at cutin legend.
4th jet cutdrives rate—not surprising
September 7, 2006 FTK Meeting 9
Hhhbbbb sigma*BR• I had a problem with low *BR (2 fb) reported by pythia
for Hhhbbbb w/ mh=130, mH=300.– What MSSM model was pythia assuming?
• Turns out Hhh is large only for lowish tan, and for 2mh<mH<2mt.
• To find operating points:– Use mh
max scenario to stay away from LEP direct search limits.– For a given tan, scan mA to maximize (ggH) x BR(Hhh) x
BR(hbb) x BR(hbb).
tan 2.5 2.75 3.0 3.25 3.5 4.0 4.5 5.0
mA 360 260 230 240 240 250 260 260
*BR [fb] 233 1019 1060 818 637 398 250 168
Additional slides
September 7, 2006 FTK Meeting 11
Physics Case (Details)Statement #1
FTK vs TDR menus,i.e. no tracking atLVL2—ignore timing.
Statement #2
FTK vs nominal LVL2,incl. tracking. Need:
• FTK allows b-jet ()ID w/ b, c, q, .
• Correlation w/ offline?• Depends on environment
• LVL1 trigger rate, drivenby multijet evts, estimatedusing modern generator +parametrization of fullATLAS LVL1 simulation.
Fix LVL2 outputrate.
Limit LVL1 outputrate to sth reasonable.
Optimize LVL1 cuts& LVL2 tagging reqs, maximizing signal acceptance/significance.
Same as stmt #1,but add triggertiming into the eqs.
Hard to estimate,large uncertainties.
But more realistic,stronger case.
September 7, 2006 FTK Meeting 12
CKKW vs MLM• CKKW: 2 parts
– Reweight ME to reproduce PS behavior for soft emissions.
– Reject showers that overlap higher-order ME.
• Boundary is kT,cut
or ycut kT,cut2/s.
• MLM: matching prescription– Cluster partons after shower,
compare to ME partons.
– Require each ME parton to match a unique “jet”, else reject event. ALPGEN
SHERPA
4p ME 3p ME
CKKW
MLM
top related