Exploring Associated ttH Channel and Higgs Combinations in Particle Physics
Discussion on the associated ttH channel and Higgs combination in particle physics, focusing on observations, results, and implications from experimental data at CERN. Highlights the production and decay channels of the Higgs boson, observations in various experiments, and considerations for future analyses.
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Associated ttH Channel and Higgs Combination iscussion Albert De Roeck CERN, Geneva, Switzerland
ttH/combination: Run-1 arXiv:1606.02266 / JHEP 1608 (2016) 045 5153 authors!! ~700 citations ttH came out high both in CMS and ATLAS 1
ttH Results ttH production: Combination of all Higgs decay channels and combination with the 7/8 TeV data of Run-1 arXiv:1804.0261 arXiv:1806.0425 7+8+13 TeV data Observation of ttH! Significance = 5.9 (exp 4.2 ) Results in agreement with the Standard Model
Observations ttH!! ttH: We have an observation in both experiments. Signal strength > 1 but within uncertainties ok with SM Some channels dominated by systematic uncertainties. ttbb remains an important part. New input from data/TH to expect? Strongly MVA/BDT driven. Deep learning? Note: No real top quark reconstruction in these analysis. Start to see it in H->gamgam tH channel next? A milestone measurement! 3
Higgs Combinations @ 13 TeV Combination of all Higgs production/decay channels at 13 TeV Check overall consistency of the couplings HIG-17-031 Results in agreement with the Standard Model 4
Observations: Combination Many Higgs channels seem systematically a little high, hence the overall signal strength comes out >1 (within 1.5 signal so) for both CMS and ATLAS. A tendency? Uncertainty budget? Precision on the result no longer just statistics dominated. CMS based on 2016 & ATLAS on 2017+ partially on 2018 data. Do we plan overall combination? Or a Mass/width combination to start with? -> Not planned until after run-II? We follow the Higgs YR framework of signal strength and and coupling modifiers, which is based on SM assumptions eg SM BRs for decays, for combinations. Should we rethink the framework eg if we get O(10%) deviations?
Backup 6
2012: The Higgs The party in 2012! Not everybody at the party eg higgsless models A. Pomarol ICHEP2012 But careful about resurrections, Higgs imposters
2012: A Milestone in Particle Physics Observation of a Higgs Particle at the LHC, after about 40 years of experimental searches to find it 2014: Higgs Boson well established. Most accessible channels studied Observation in WW, ZZ and channels tau tau at the limit bb and ttH not observed in Run-1 ggF 2018 8
Brief Higgs Summary from Run1 We know already a lot on this Brand New Higgs Particle!! Width < 24 MeV (95%CL) Mass = CMS+ATLAS 125.09 0.21(stat) 0.11(syst) GeV Couplings are within ~20% of the SM values Spin = 0+(+)preferred over 0-,1,2 SM-like behaviour for most properties, but continue to look for anomalies, i.e. unexpected decay modes or couplings, multi-Higgs production
Higgs: ATLAS+CMS Combination The Run-1 Higgs Legacy! arXiv:1606.02266 / JHEP 1608 (2016) 045 5153 authors!! The newly found boson has properties as expected for a Standard Model Higgs Signal strength/SM:
Summary New Higgs measurements at 13 TeV. So far the Higgs is very consistent with Standard Model expectations. No sign of new physics in the 13 TeV data so far This starts to cut into the preferred regions for a large number of models, like SUSY. Naturalness? There are a number of 3-sigma effects, as always, but Dark Matter and Long Lived Particle searches are being explored in a systematic way. White paper on LLPs to appear. First results from the 2017 data being released. New physics in the flavour sector? New TH paradigms? The LHC is continuing to explore the Terascale. We have much data to look forward to: it takes on significant deviation to show the way!! Collected >80 fb-1@ 13 TeV so far. And hopefully one day soon: 11
