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Trilogy of LHC Higgs Cross Section Working Group - toward precision Higgs physics -

Aspen 2013 - Higgs Quo Vadis. Trilogy of LHC Higgs Cross Section Working Group - toward precision Higgs physics -. Reisaburo Tanaka (ATLAS, LAL) o n behalf of LHC Higgs XS WG Higgs Quo Vadis, Aspen, March 14, 2013. Contents. LHC Higgs Cross Section Working Group Higgs C ross S ections

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Trilogy of LHC Higgs Cross Section Working Group - toward precision Higgs physics -

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  1. Aspen 2013 - Higgs Quo Vadis Trilogy of LHC Higgs Cross Section Working Group - toward precision Higgs physics - Reisaburo Tanaka (ATLAS, LAL) on behalf of LHC Higgs XS WG Higgs Quo Vadis, Aspen, March 14, 2013 Trilogy of LHC Higgs XS WG

  2. Contents • LHC Higgs Cross Section Working Group • Higgs Cross Sections • Higgs Decay Branching Ratios • Jet-bin and Higgs pTUncertainties • InterferenceEffects in gg→H→VV • NLO Monte Carlo • Higgs Coupling and Spin/Parity • BSM Higgs Summary Disclaimer: Experimentalist’s overview of LHC Higgs XS WG activity, putting emphasis on current issues (with personal bias). Special thanks to the colleagues in LHC Higgs XS WG. Trilogy of LHC Higgs XS WG

  3. Higgs physics at LHC • Main question today: is Higgs-like signal at MH=125 GeV the SM ? • Precision Higgs Physics • Higgs mass, coupling and JPC. • Hadron collider machine can do precision physics ! • Theory uncertainty is becoming more and more important than ever before ! • Finding the hint of BSM physics is prime important issue ! • What is the implication of 125 GeVHiggs for xMSSMscenario ? • What could be the new benchmark process for BSM Higgs searches ? • EW Singlet, 2HDM, Triplets, Dilaton, Composite, etc… • VLVLscattering and unitalization issue. • LHC Higgs XS WG: currently 11 subgroups • Higgs Productions: ggF, VBF, WH/ZH and ttH • Common Issues: BR, Jets, NLO MC and PDF • Light Mass Higgs (Higgs coupling and JPC) • MSSM • Heavy Higgs / BSM → Need to reinforce Light Mass Higgs and BSM subgroups in particular. After talk yesterday … Trilogy of LHC Higgs XS WG

  4. Challenges for precision Higgs physics • Experimental Challenges • Clear separation of ggF, VBF, WH/ZH and ttH. • Improve Higgs mass measurements (FSR etc.) • Other decay modes than big 5: H→μμ, Zγ, invisible, HH, etc. • How to carry out BSMHiggs search? Interpret SM Higgs as background ? • What could be the target for near future improvements ? • Higher-order calculations (ex. NNNLO in ggF, scale uncertainty < 5%?) • PDF measurements with LHC data (ggparton luminosity < 5%?) • Better prediction on the differential distributions in Higgs and SM bkg. • Reduction of jet-bin uncertainty, ggF in 2-jet bin (VBF) category & fat jets. • Interference effects between Higgs and SM continuum, ex. γγ, WW, ZZ. • Which tools do experimental collaborations need ? • Tools for Higgs property measurements, ex. MELA/JHUGen, MadGraph5 • (N)NLO MC’s for Higgs and SM backgrounds, ex. H+jj. • Support for future LHC Higgs physics program • HL-LHC (14 TeV, 3 ab-1 by ~2030) on Higgs (self-)coupling. • Further study for HE-LHC (33 TeV or above?). Trilogy of LHC Higgs XS WG

  5. Higgs Physics Theoretical Issues ggF, VBF, WH/ZH, ttH, BSM Higgs Jet bin uncertainty H+0,1,2-jets Higgs Cross Sections (inclusive/exclusive) Differential K-factors (effect of jet-veto etc.) QCD correction NkLO + NmLL EW correction, Mixed QCD-EW Heavy Higgs Line Shape SM Backgrounds & Interferences Higgs Mass, Coupling and JPC gluon W/Z top/bottom Higgs decay Branching ratios (QCD/EW corr.) Higgs New particles W/Z Higgs pT (soft gluon resummation) PDF+αs uncertainties Renormalization/Factorization scale dependence Trilogy of LHC Higgs XS WG

  6. Tools for Higgs Physics ggF, VBF, WH/ZH, ttH, BSM Higgs Cross Section ggF HIGLU(NNLO QCD+NLO EW) iHixs(NNLO QCD+NLO EW) FeHiPro(NNLO QCD+NLO EW) HNNLO, HRes(NNLO+NNLL QCD) ggh@NNLO(NNLO QCD) VBF VV2H (NLO QCD) VBFNLO(NLO QCD) HAWK (NLO QCD+EW) VBF@NNLO (NNLO) WH/ZH V2HV (NLO QCD) VH@NNLO (NNLO) ttH HQQ(LO QCD) bbH bbH@NNLO(NNLO QCD) + private codes. MSSM FeynHiggs, SusHi 2HDMC, CPSuperH Jet-veto JetVHeto gluon W/Z top/bottom Higgs Decay HDECAY (NLO) Prophecy4f(NLO) Higgs W/Z Higgs pT HqT(NLO+NNLL) ResBos(NLO+NNLL) Higgs Properties MELA/JHU, MEKD MadGraph5 NLO MC aMC@NLO, POWHEG, SHERPA, HERWIG++ MCFM PDF: MSTW2008, CT10, NNPDF2.1, etc. Trilogy of LHC Higgs XS WG

  7. SM XS TF MC Group Statistics Forum LHC Higgs Cross Section Working Group ATLAS ⊕ CMS ⊗ Theory Creation announced in January 2010. Kickoff meeting on February 3, 2010. Workshops in Torino (Nov. 2009), Freiburg (April 2010), CERN (July 2010), Bari (Nov. 2010), BNL (May 2011), Paris (Nov. 2011), CERN (May, Dec. 2012) Task: SM and MSSM Higgs Cross Section and BRs • Uncertainty estimation (scale, αs, PDF, etc.) • Monte Carlo at NLO for signal and bkg. • Higgs Property Measurements • BSM Higgs Scenarios 11 Working Subgroups: ggF, VBF, WH/ZH, ttH, MSSM Light Mass Higgs, Heavy Higgs/BSM BR, Jets, NLO MC, PDF LHC Higgs Combination WG PDF4LHC WG Trilogy of LHC Higgs XS WG

  8. 1. LHC Higgs Cross Section Working Group All info from https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CrossSections Mailing lists lhc-higgs@cern.ch (main), lhc-higgs-lm@cern.ch (Higgs properties) Trilogy of LHC Higgs XS WG

  9. Trilogy of LHC Higgs XS WG’s CERN Report CERN Report 1 went out before the 1st Higgs results of LHC ! (facilitated the comparison and combination, appreciated by the collaborations) 64 authors 151 pages 370 references 120 authors 275 pages 456 references Trilogy of LHC Higgs XS WG

  10. Trilogy of LHC Higgs XS WG’s CERN Report CERN Report 3 to be completed by late spring 2013 ! Trilogy of LHC Higgs XS WG

  11. 2. Higgs Cross Sections • Official numbers for Higgs cross sections at 7 and 8 TeV and spread sheet at • https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageAt7TeV • https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageAt8TeV • Now ggF and VBF cross sections with complex-pole-scheme (CPS) for entire mass range both at 7 and 8 TeV. WH/ZH and ttH in ZWA. • Always compared with two independent calculations, ex. dFGvs ABPS for ggF. • Assume factorization between QCD and EW radiative corrections. • QCD scale uncertainties, ex. ggF 1/2MH < μR,μF < 2MH (1//2 < μR/μF< 2) 7&8 TeV scan points in CERN Report 3 Trilogy of LHC Higgs XS WG

  12. Higgs cross section theory uncertainties • Renormalization and factorization scale uncertainty study by M. Cacciari et al. work in progress. • Higher-order calculations, ex. ggFQCD scale: ±8%@NNLO → ±5%@NNNLO in few years ? • PDF+αs (PDF4LHC prescription): ±8% → <5% with improvements with LHC data ? • jets, top, prompt photons and Z pT distributions contribute gluon PDF determination. (but paradoxically, ggFis the best measure to determine ggparton luminosity around MH=125GeV!) MH=125 GeV K-factor, QCD scale and PDF uncertainties Trilogy of LHC Higgs XS WG

  13. QCD scale uncertainty • LHC Higgs combination WG’s prescription (ATL-PHYS-PUB-2011-011, CMS Note-2011/005) • Subdivide nuisance parameters until they become uncorrelated. • Take Gaissian/Log-normal for pdf. Practically Gaussian as κ≃1.0 for scale. • New method by M. Cacciari and N. Houdeau. JHEP 09 (2011) 039 • Preserves both characteristics of log-normal (tail) and flat-top. • Treats renormalization scale only, factorization scale is work in progress. • Questions are flat-top width and tail length. log-Cacciari-Houdeau Gaussian/log-normal log-double-Fermi-Dirac to smoothen the edges (used in ATLAS-CONF-2013-034 ) Trilogy of LHC Higgs XS WG

  14. PDF+αs uncertainty • Currently assume separate gg-initiated ±8% and qq-initiated ±4%. • Assumes NO PDF+αs correlation between (ggF, ttH, tt, …) and (VBF, VH, VV, …). • Full correlation study in CERN Report 2 (https://cds.cern.ch/record/1416519) • ggF – VBFρ=-0.6 … due to sum rule of Σ(gg+qq+qqbar)=1. • ggF– WH ρ=-0.2… due to small correlation between ggvsqqbar. • ggF– ttHρ=-0.2… it's the different Bijorken-x. • All these issues should be discussed in LHC Higgs Combination WG. Table 10 Trilogy of LHC Higgs XS WG

  15. Proposal for theory uncertainty statistical treatment • Long debate on QCD scale + PDF+αsuncertainty handling. • We suggest to separate either 1) theory uncertainty (THU) or 2) parametric uncertainty (PU). • Statistical nature of THU behavior is unknown while PU is believed to behave as Gaussian (or log-normal) due to central limit theorem after many measurements. Such example is PDF+αs uncertainty. Trilogy of LHC Higgs XS WG

  16. HL-LHC & HE-LHC • Higgs cross sections for HE-LHC (33TeV) for ggF, VBF, WH/ZH and ttH. • QCD scale uncertaintydoes not change compared to 7/8 TeV. • PDF+αs uncertainty also does not change much compared to 7/8 TeV. • Cross section is predictable via parton luminosity ratio. • Ex. ggF is at the same MX in gg ratio, VBF MX+few hundred GeV in qq ratio. • Cross sections for Higgs self-coupling … core of future Higgs physics at LHC ! • gg → HH (HHH), qq→ qqHH, WHH/ZHH https://twiki.cern.ch/twiki/bin/view/LHCPhysics/HiggsEuropeanStrategy2012 Trilogy of LHC Higgs XS WG

  17. 3. Higgs Decay Branching Ratios A. Denner et al., Eur. Phys. J. C (2011) 71 • Use HDECAY and Prophecy4f for best estimate. • What are the theory (THU) + parametric (PU) uncertainties ? • Relatively large uncertainties for H→ττ, μμ, γγ, Zγ/WW/ZZ at low MH. • Smaller uncertainties relative to scale and PDF+αsuncertainties in Higgs production. Separation of BR THU and PU are in progress. Stick to THU+PU ±5-10% conservative uncertainty. Updated numbers in CERN Report 2. https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageBR2 Major change was BR(H→ss) due to quark mass definition. Trilogy of LHC Higgs XS WG

  18. Frequently asked question: which MH for μ ? Large MH dependence in σ×BR in H→WW, ZZ as BR is changing rapidly. ATLAS-CONF-2013-014 Update → Aaron’s talk μ=(σ×BR)obs /(σ×BR)SM ΔMH=2GeV Trilogy of LHC Higgs XS WG

  19. 4. Jet-bin Uncertainty • Huge cancellation in fixed-order calculation between K-factor (σtot) and large Sudakov log (σ≥1jet). • So far we have been following the Stewart&Tackmann prescription. • Conservative approach by assuming the n-jet inclusive cross section σ≥n-jetuncertainties are uncorrelated in perturbation theory. • Recent proposal by G. Salam et al. • Use jet-veto efficiency (indep. from σtot) • K-factor cancels in ε=σ0-jet/σtot • NNLO+NNLL for 0-jet bin uncertainty is ±15%→±9% ! (code JetVHeto) • Work in progress for 1-jet bin. • Works by R. Boughezalet al. arXiv:1302.6216 A. Banfi et al., PRL 109 (2012) 202001 Focal points: 1. reduction in jet-bin uncertainty for 1-jet exclusive in particular, 2. ggF+2-jets contamination in VBF category, how to reduce contamination and asso. uncert., 3. developments for other categorization methods rather than jet-binning, how to avoid soft-gluon. Trilogy of LHC Higgs XS WG

  20. Higgs pT Uncertainty • Higgs pT in ggF is an important discriminant variable against VBF and SM backgrounds. • Theory uncertainty in Higgs pT • Acceptance uncertainties (Higgs pT), event migration between different categories. • Non-perturbative effects (Hadroniztion, UE). • POWHEG ggFhas finite quark-mass effect plus Higgs pT tuned to HqT2 (hfact=MH/1.2). Thus NO MC reweighting has been necessary. • Recent discussions on HiggpTuncertainty due to finite quark-mass effect with t/b. • Assign ±10% uncertainty on Higgs pT in ggF due to finite quark-mass effect ? • We should consider Higgs Higgs pT uncertainty in other channels as well in VBF, WH/ZH and ttH, due to missing HO corrections (ex. NLO EW), QCD scale, PDF+αs, etc. Trilogy of LHC Higgs XS WG

  21. 5. InterferenceEffects in gg→H→VV • Interference between gg→H→γγ, WW, ZZ and SM background continuum • gg→H→γγ: few % effect for light Higgs after experimental cuts (L. Dixon) • gg→H→WW: -10% negative interference for light Higgs and large positive for heavy Higgs. (MCFM by K. Ellis et al., gg2WW by N. Kauer). • For light Higgs, the interference can be suppressed via transverse mass cut MT<MH. • gg→H→ZZ: similar situation as H→WW but smaller interference. • Now prescription exists for heavy Higgs analysis ! • Higgs mass shift +150MeV in H→γγ? S. Martin, PRD 86 (2012) 073016 • Now under investigation by L. Dixon, D. de Florian for H→γγ and N. Kauer for H→ZZ*. • cf. (ATLAS-CONF-2013-014) N. Kauer, G. Passarino, JHEP 1208 (2012) 116 G. Passarino Higgs discovery by theorist ! Trilogy of LHC Higgs XS WG

  22. InterferenceEffects in HiggsDecay • Interference in Higgs decay (→ use Prophecy4f !) • H→ZZ→e+e-e+e- or μ+μ-μ+μ- (+11%@MH=120GeV) … corrected in the analysis. • H→WW/ZZ→e+νe-ν, μ+νμ-ν (-5.4%@MH=120GeV) … not corrected as no H→4f MC! • Interferencein SM bkg. qq/gg→ZZ→e+e-e+e- or μ+μ-μ+μ-alsoexists. Ratio between approximation with PDG Br(V→ff) and Prophecy4f (with interference) Trilogy of LHC Higgs XS WG

  23. 6. NLO Monte Carlo Many progresses in (N)NLO Monte Carlos • Higgs signal • POWHEG MINLO Proposal: • Replace current POWHEG H+PYTHIA with new MINLO HJ to achieve NLO in both H inclusive and H+J distributions. NNLO accuracy can be achieved via weighting. • Use new MINLO HJJ when 2-jets are strictly required (i.e. VBF analysis). • Note: neither finite-quark mass nor HqT tune is done in MINLO HJ currently. • Higgs decay with Prophecy4f (can be embedded in Higgs NLO MC with NWA) • Important step towards precision Higgs physics with NLO QCD+EW corrections, FSR effect, interference effect, off-shell gauge boson effect, etc. H→4f physics at LHC ! • SM backgrounds • γγ: 2γNNLO • V+jets: ALPGEN, BlackHat for V+4-jets (V+5+jets in progress) SHERPA, POWHEG(MINLO) for V+0,1,2-jets • VV+jets: POWHEG-BOX WWjj(EW), how about ZZjj? • Vbb: POWHEG-BOX Wbb, how about Zbb? • BSM Higgs • Aim MadGraph5 as platform for BSM Higgs MC (aside Higgs JPC study) • Higgs pT in MSSM Higgs (finite quark mass effect, t/b+interference) K. Hamilton et al., JHEP 10 (2012) 155 (arXiv:1206.3572), arXiv:1212.4504 Trilogy of LHC Higgs XS WG

  24. 7. Higgs Coupling and Spin/Parity • Higgs coupling measurement → talk by G. Weiglein • How to go beyond LO coupling definition with EFT ? (post interim, arXiv:1209.0040) • Higgs tensor structure JPC → talk by M. Grazzini • Consistent framework in JHU, HAWK/VBFNLO and MadGraph5 on 0±, 1±, 2±. • MadGraph5 as versatile tool for Higgs (NLO MC, ggF/VBF/WH/ZH/ttH, spin corr.). • Current LHC data already disfavor 0-, 1±, 2±. • The next step would be CP-mixture and CP-violation in 0±. • For CP mixture with interference, which benchmark model with which coupling ? • Which MC tools are available, JHU@CMS, MadGraph5, MEKD@CMS, etc. ? • What mixing observables we should measure as sensible variables, ex ΔΦZZ ? MadGraph5 Trilogy of LHC Higgs XS WG

  25. 8. BSM Higgs • ATLAS and CMS need the good benchmark scenario for BSM Higgs searches on top of SM-like Higgs signal at Mh=125 GeV. • Currently discussed are MSSM, 2HDM, EW singlet models. • MSSM • New proposed scenarios: mhmod+, mhmod-, light stop. • 2HDM • New ATLAS results in H→WW in Type-I,II. (ATLAS-CONF-2013-027) • Used SusHi by reweighting SM Higgs XS with (α,β,MH) parametrization. • Needs to come to agreement on baseline models in Type-I,II,III,IV … M. Carena et al. arXiv:1302.7033 Trilogy of LHC Higgs XS WG

  26. Summary • Two prominent pillars for Higgs physics at LHC for Higgs Quo Vadis. • Precision measurements on Higgs properties of couplings and spin/parity. • Direct searches for the signature of BSM Higgs on top of 125 GeV signal. • Theory uncertainties are already becoming non-negligible ! • Experimental accuracy Δμ(σ/σSM)=±15% (roughly ±10% for both stat.&syst.). • Theory uncertainty is O(±10-15%) dominated by QCD scale and PDF+αsin ggF. • Future improvements in NNNLO prediction in ggF, PDF, Higgs pT, etc. • Important jet issues: reduction of uncertainty in 1-jet bin, ggF+2-jets vs VBF. • Clean separation of ggF, VBF, WH/ZH and ttH is the essential. Many challenging issues for both EXP and TH for Higgs physics at LHC ! Trilogy of LHC Higgs XS WG

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