Theory Higgs: Lineshape and Interference

Transcription

1 Theory Higgs: Lineshape and Interference Nikolas Kauer Royal Holloway, University of London Higgs Hunting 2017 Orsay Paris, France July 24, / 34

2 Outline HXSWG YR4: Off-shell Higgs and Higgs interference RECAP AND RECENT/ONGOING WORK H ZZ, W W (+jets) in ggf & VBF: sizeable off-shell Higgs signal contribution with large signal-backg. interference Higgs width measurement in a nutshell, Γ H bound at the LHC BSM/EFT: exploiting the off-shell H VV region BSM: heavy scalar light Higgs background interference effects Higgs width constraints from gg H γγ Precision predictions for gg ( H) V V interference/backg. Matrix element parton shower matching/merging Implementing NLO in MC tools Summary and future directions N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

3 HXSWG YR4: Off-shell Higgs and Higgs interference (51 p. in arxiv: ) F. Caola, Y. Gao, NK, L. Soffi, J. Wang (eds.), A. Ballestrero, C. Becot, F. Bernlochner, H. Brun, A. Calandri, F. Campanario, F. Cerutti, D. de Florian, R. Di Nardo, L. Fayard, N. Fidanza, N. Greiner, A. V. Gritsan, G. Heinrich, B. Hespel, S. Höche, F. Krauss, Y. Li, S. Liebler, E. Maina, B. Mansoulié, C. O Brien, S. Pozzorini, M. Rauch, J. Roskes, U. Sarica, M. Schulze, F. Siegert, P. Vanlaer, E. Vryonidou, G. Weiglein, M. Xiao, S. Yue I.8.3 H VV modes (V = W,Z) I Input parameters and recommendations for the QCD scale and the order of the gluon PDF I Off-shell and interference benchmark cross sections and distributions: Standard Model I Off-shell and interference benchmark cross sections and distributions: 1-Higgs Singlet Model I Multijet merging effects in gg l ν l l ν l using SHERPA I Study of higher-order QCD corrections in the gg H VV process I Higgs boson off-shell simulation with the MCFM and JHU generator frameworks I Interference contributions to gluon-initiated heavy Higgs production in the 2HDM using GOSAM I.8.4 gg VV at NLO QCD I The status of theoretical predictions I Brief description of the NLO computation for gg 4l I Results and recommendation for the gg ( H) ZZ interference K-factor I.8.5 H γγ mode I Theory overview, I Monte Carlo interference implementations I Studies from ATLAS N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

4 BR [pb] σ τ + τ - VBF H τ + τ gg H ZZ, W W : sizeable off-shell Higgs signal with large signal-background interference ± WW l νqq + - WW l νl ν + - ZZ l l qq + - ZZ l l νν s = 8TeV ZZ l l l l ± WH l νbb γγ l = e, µ tth ttbb ν = ν e,ν - µ,ν τ + ZH l l bb q = udscb M H [GeV] LHC HIGGS XS WG 2012 [ pb] dσ dm V 2 V M 2 V V ZZ HTO powered by complex - pole - scheme MZ 2 Mt 1000 M V V [ GeV] dσ/dmzz [fb/gev] e-05 1e-06 gg ( H) Z(γ )Z(γ ) l ll l, MH=126GeV pp, s = 8TeV ptl > 3GeV, ηl < 2.6 Mll > 4GeV, pt(z) > 2GeV Hoffshell H 2 + cont 2 H+cont 2 1e MZZ [GeV] gg H VV 4l and2l2ν signal-background interference very well studied ato(α 2 sα 4 ): Glover, van der Bij (1989); Kao, Dicus (1991); Binoth, Ciccolini, NK, Krämer (2006) (gg2ww); Campbell, Ellis, Williams (2011) (MCFM); NK (2012) (gg2vv); NK, Passarino (2012); Campanario, Li, Rauch, Spira (2012); Bonvini, Caola, Forte, Melnikov, Ridolfi (2013); Caola, Melnikov (2013); NK (2013) (gg2vv); Campbell, Ellis, Williams (2013) (MCFM); Campbell, Ellis, Williams (2014) (MCFM); Campbell, Ellis, Furlan, Röntsch (2014); related interference effects: Bredenstein, Denner, Dittmaier, Weber (2006) (PROPHECY4f); YR3: Denner, Dittmaier, Mück (2013) and Anderson, Bolognesi, Caola, Gao, Gritsan, Martin, Melnikov, Schulze, Tran, Whitbeck, Zhou (2013); Chen, Cheng, Gainer, Korytov, Matchev, Milenovic, Mitselmakher, Park, Rinkevicius, Snowball (2013); Chen, Vega-Morales (2013) tools for ggf: MCFM-6.8, gg2vv (gg VV parton-calculators and event generators), MadGraph5, Sherpa+OpenLoops (allows for merging of gg V V + {0, 1} jets) loop technology closing in on calculation at O(α 3 s α4 ) (see below) Aachen/FNAL/IPPP, Karlsruhe, Zurich gluon-fusion Higgs production and semileptonic decay: Dobrescu, Lykken (2010); Lykken, Martin, Winter (2012); Kao, Sayre (2012); ATLAS arxiv: ; ATLAS arxiv: ; CMS PAS HIG N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34 gg2vv

5 Interference for pp H ZZ + jet off-shell Higgs cross sections for ZZ and ZZ+jet comparable (p Tj > 30 GeV) Campbell, R.K. Ellis, Furlan, Röntsch figures taken from arxiv: Z bosons treated in zero-width approximation (validated for ZZ final state: excellent for m 4l > 300 GeV) N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

6 Higgs width measurement in a nutshell Total Higgs width Γ H is not a fundamental parameter of the theory, but of great phenomenological interest (Higgs mechanism overall coupling strength) Direct Higgs width measurement via resonance shape is limited at LHC by experimental mass resolution of O(1) GeV (CMS: Γ H < 1.1 GeV, but note that Γ H,SM 4 MeV) All resonant Higgs cross sections depend onγ H, thereforeγ H and couplings cannot be determined at the LHC (on-peak) without theoretical assumptions M. Duhrssen et al. (2004), LHC Higgs Cross Section WG (2012) For broad class of models, assuming upper limit for HWW or HZZ coupling (e.g. SM) upper bound for Γ H (Γ H = O(Γ H,SM)) M. Peskin (2012); B. Dobrescu, J. Lykken (2013) Assuming no BSM Higgs decays, and Higgs coupling parameterisations, can fit Higgs width to data and agreement with SM Higgs width is found V. Barger, M. Ishida, W. Keung (2012); K. Cheung, J. Lee, P. Tseng (2013); J. Ellis, T. You (2013); A. Djouadi, G. Moreau (2013); P. Bechtle, S. Heinemeyer, O. Stal, T. Stefaniak, G. Weiglein (2014) e + e Z(H all): construct recoil mass and measurehzz coupling Γ H can be determined indirectly, ILC: 6% 11% accuracy M. Peskin (2013), T. Han et al. (2013) Direct threshold scan at muon collider: Γ H accuracy 4% 9% T. Han, Z. Liu (2013) Higgs width determination could provide first evidence for BSM Higgs interactions N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

7 Off-shell Higgs signal and Higgs width determination indirect Higgs width determination via on- and off-peak Higgs cross section F. Caola, K. Melnikov (2013) arxiv: M i H f 2 M i 2 M f 2 = p 2 H M2 H +im HΓ H 2 resonance contribution to signal cross section ( on-peak ): σ i H f NWA g2 i g2 f Γ H NWA scaling degeneracy: σ unchanged if g i ξg i, g f ξg f, Γ H ξ 4 Γ H see L. Dixon, Y. Li arxiv: (or below, p. 18) p 2H M H O(Γ H ) p 2 H M2 H M HΓ H M i H f 2 M i 2 M f 2 p 2 H M2 H 2 ) off-resonance contribution ( off-peak ): σ i H f ( p 2 H M H O(Γ H ) gi 2 g2 f sizeable off-resonance contribution to signal cross section is independent of Higgs width, and therefore breaks NWA scaling degeneracy: σ off-peak /σ on-peak Γ H competitive constraints on Higgs width without assumptions(?) feasible with LHC data large interference with cont. background (necessary to prevent unitarity violation) weakens bounds N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

8 MCFM analysis J. Campbell, K. Ellis, C. Williams (2013) Higgs width bounds from matrix element method (H ZZ) Matrix element method: optimize discrimination using fully differential information 0.07 σ C P q q: q q induced continuum background P gg: gg induced contributions (incl. Higgs signal, cont. bkg. & interf.) P H: gg induced Higgs amplitude squared Discriminant: ( ) P H D S = log P gg +P q q d σ / d D S σ H+C (ξ =10) 4 σ H (ξ =10) Γ H < ( ) +3.9 Γ SM H (95% CL), (D S > 1) bound 1.6 better than for m 4l > 300 GeV D S N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

9 CMS analysis arxiv: (May 2014) improvements: include 2l2ν final states include VBF channel (contributes 7% on peak, and O(10%) above 2M Z) include known QCD and EW corrections F. Caola, T. Kasprzik, G. Passarino, M. Zaro et al. slightly different kinematic discriminant (P H P gg), backgrounds fully considered Γ H < 5.4 Γ SM H (95% CL) N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

10 ATLAS analysis arxiv: (July 2014, March 2015) improvements: similar to CMS, thorough consideration of systematic uncertainties provide results as function of the unknown gg ZZ background K-factor, variation: [0.5, 2] signal K-factor off-shell signal strength 95%-CL upper limit [5.1,8.6] ([6.7,11] expected) Events / ATLAS H ZZ 4l -1 s = 8 TeV: Ldt = 20.3 fb Data SM (stat syst) Total (µ =10) off-shell gg+vbf (H* ) ZZ Background qq ZZ Background Z+jets, tt -2lnΛ 14 ATLAS H ZZ+WW off-shell+on-shell κ g/v,on-shell = κ g/v,off-shell -1 s = 8 TeV: Ldt = 20.3 fb observed with syst. observed no syst. expected with syst. expected no syst ME Discriminant SM Γ H /ΓH Γ H < [4.5,7.5] Γ SM H (95% CL) N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

11 Higgs (width) constraints from vector boson fusion off-shell effect also in VBF H VV: O(10%) of Higgs signal is off-shell note: no exp. sensitivity to off-shellh VV tail invh andt th channels (seeσ prod (M H )) J.M. Campbell, R.K. Ellis, arxiv: (see also C. Englert, M. Spannowksy arxiv: , C. Englert, M. McCullough, M. Spannowksy arxiv: ) most sensitive off-sh. channel: W ± W ± due to lower bkg. (t-channel Higgs!) Γ H < 61 Γ SM H (LHC Run 1), Γ H < 4.4 Γ SM H Γ H < 3.2 Γ SM H (LHC 300 fb 1 data) (LHC 100 fb 1 data), N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

12 BSM studies Off-&on-shellΓ H bound not strictly model independent (E-dependent Higgs couplings?) C. Englert, M. Spannowski arxiv: Constraining higher dimensional operators with the off-shell Higgs (below) Disentangling New Physics with the off-shell Higgs boson EFT studies including the off-shell Higgs boson (next slides) fb/gev e-05 1e-06 1e-07 1e-08 Cross Section for 2e2! Final State without Cuts SM / bg Four-Lepton Invariant Mass (GeV) O 1 = M2 Z v HZµZµ (SM), O 2 = 1 2v HZµνZµν, O 3 = 1 2v HZµν Z µν, O 4 = M 2 Z M H 2 v ZµZµ 2 H, O 5 = 2 v HZµ 2 Z µ J. Gainer, J. Lykken, K. Matchev, S. Mrenna, M. Park arxiv: Also: modification of lepton angular distributions good control with 300 fb 1 I. Anderson et al. arxiv: and: ggww dimension-8 contact operators J. Bellm, S. Gieseke, N. Greiner, G. Heinrich, S. Plätzer, C. Reuschle, J. Felix von Soden-Fraunhofen arxiv: N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

13 EFT analysis of on- and off-shell H ZZ 4l data A. Azatov, C. Grojean, A. Paul, E. Salvioni (2014, update 2016) (see also G. Cacciapaglia, A. Deandrea, G. Drieu La Rochelle, J. Flament (PRL 2014)) g Z g Z g Z g c c g t Z Z g g m t L = c t v tth+ g2 s h 48π 2 cg v GµνGµν M gg ZZ = M h +M bkg = c tm ct +c g M cg +M bkg Z σ c t +c g 2 : on-shell degeneracy c t +c g = const is broken by far-off-shell data Constraints in (c t,c g) plane (68%, 95% and 99% probability contours): (not MELA improved!) LHC 8 TeV CMS data LHC 14 TeV 3 ab 1 data N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

14 Effective ggh coupling: boosted v. off-shell Higgs sensitivity Exclusion plot based on n, p jets T,H 1 σ 2 σ expected 95% CL Exclusion plot based on cosθ e and m 4l 1 σ 2 σ expected 95% CL CL s 95% exclusion CL s 95% exclusion H WW k tg =(0.7,0.3) gg ZZ k tg =(0.7,0.3) L [fb ] L [fb ] left: boosted analysis, right: off-shell analysis (not MELA improved) M. Buschmann, D. Goncalves, S. Kuttimalai, M. Schoenherr, F. Krauss, T. Plehn (2014) ( ) N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

15 P Heavy scalar (Φ) interference studies (2016) Heavy Higgs background light Higgs: non-trivial interference patterns Signal-background interference in gg ( Φ) γγ ( 750 GeV state ) and gg ( Φ) t t A. Djouadi, J. Ellis, J. Quevillon arxiv: (left fig.) Signal-background interference in gg ( Φ) t t with higher order QCD effects (simplified model and 2HDM) B. Hespel, F. Maltoni, E. Vryonidou arxiv: (center fig.) Higgs-Singlet Model interference effects with EFT operators (Φ-SM gauge bosons) S. Dawson, I.M. Lewis arxiv: Signal-background interference for a singlet spin-zero digluon resonance S.P. Martin arxiv: (right fig.) 2t s r TeV LHC Γ gg = 0.01M, Γ = 0.06M M = 750 GeV dσ/dm (fb/gev) Digluon mass m (GeV) t t N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

16 Heavy scalar interference studies (2015/16) Heavy Higgs background light Higgs: non-trivial interference patterns Higgs Singlet Extension (ggf) NK, C. O Brien arxiv: and YR4 (left fig.) Higgs Portal Scenario (ggf) C. Englert, I. Low, M. Spannowski arxiv: Higgs Singlet Extension (VBF) A. Ballestrero, E. Maina arxiv: and YR4 Higgs Singlet Extension (VBF) F. Campanario, M. Rauch YR4 Generic couplings (tensor structure of HV V ) Gritsan, Sarica, Schulze, Xiao YR4 (center fig.) 2HDM: gg( {H, h}) ZZ, W W interference effects N. Greiner, S. Liebler, G. Weiglein arxiv: (right fig.) 2HDM: pp ( Φ) t NLO QCD W. Bernreuther, P. Galler, C. Mellein, Z.G. Si, P. Uwer arxiv: , arxiv: Multiple heavy Higgs and BSM virtual contributions in gg ( Φ) t t M. Carena, Z. Liu arxiv: MCFM+JHUGen+HNNLO X(450) Γ= 46.8 GeV LHC, s= 13 TeV H(125) Γ= GeV 1 bkg gg 2O2O' gg 2O2O' s ts dσ/dm 4O [fb/gev] X(450)+H(125)+I X(450)+bkg+I X(450)+X(125)+bkg+I L H C H IG G S X S W G m 4O [GeV] N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

17 Higgs width via interferometry in gg H γγ S.P. Martin arxiv: (LO analysis of Higgs mass peak shift) Higgs signal continuum background interference induces sizeable peak shift in gg H γγ (but negligible in gg H ZZ ) dσ/dm γγ [fb/gev] dσ int /dm γγ [fb/gev] σ MR = 1.3 GeV 1.5 GeV 1.7 GeV 2.0 GeV 2.4 GeV dσ/dm γγ [fb/gev] M γγ [GeV] M γγ [GeV] M γγ [GeV] left fig.: interference contribution (real term) before detector resolution effects center fig.: interference contribution (real term) for different mass resolutions (Gaussian, σ MR ) right fig.: peak shift of invariant mass distribution (σ MR = 1.7 GeV): M γγ = 120 MeV at LO (H γγ)+jet at LO: negligible mass peak shift (< 20 MeV for p Tj > 25 GeV) Daniel de Florian, et al. arxiv: ; S.P. Martin arxiv: N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

18 Precision predictions for gg ( H) γγ signal-background interference L. Dixon, Y. Li arxiv: (NLO analysis and Higgs width constraint) dσ int dmγγ fb GeV Interference LO gg Interference LO qg Interference NLO gg LO (gg): H LO (qg): NLO (gg): MΓΓ GeV M H MeV Destructive Interf. SM Constructive Interf. M H MeV H g O Α S 3 H g q O Α S 3 O Α S H g q O Α S H H SM SM mass shift: M γγ = 70 MeV at NLO p T,H GeV Vary Higgs width and couplings (maintaining on-peak SM signal strenghts): Γ H < 15 Γ SM H (14 TeV, 3 ab 1, 95% CL) N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

19 Higgs width via interferometry in gg H γγ with VBF H γγ mass peak as reference Calculation of pp H ( γγ)+2 jets signal (VBF and GF) and interference with background (LO) F. Coradeschi, D. de Florian, L. Dixon, N. Fidanza, S. Höche, H. Ita, Y. Li, J. Mazzitelli arxiv: m H MeV VBF GF Sum M jj 400 GeV Signal fb m H ΓΓ MeV m γγ H δmγγ H+X,NLO,incl SM δm γγ H+2j,LO,VBF cuts Η jj min also: ATLAS realistic peak shift study with Sherpa 2.0& CSS PS ATL-PHYS-PUB Becot, Bernlochner, Fayard, Yuen M H = 35±9 MeV with variation 1 < K bgk < K sig at NNLO (from known NLO) Bern, Dixon, Schmidt N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

20 Precision predictions for gg ( H) γγ signal-background interference NLO+NLL q T resummation for gg( H) γγ interference L. Cieri, F. Coradeschi, D. de Florian, N. Fidanza arxiv: NLO+NLL q T resummation formalism, based on Bozzi, Catani, de Florian, Grazzini arxiv:hep-ph/ Catani, Cieri, de Florian, Ferrera, Grazzini arxiv: Uncertainty bands from varying µ R/F and resummation scale as µ R = 2m H, µ F = m H /2 and µ R = m H /2, µ F = 2m H with µ res [m H /4,m H ] Setup: s = 8TeV, MSTW 2008 MSTW arxiv: , cuts: qt,γ1 > 40GeV, q T,γ2 > 30GeV, smooth cone Frixione arxiv:hep-ph/ n = 1, E max = 3GeV, R = /dqt (pb/gev) d s = 8TeV q T (GeV) Resummation distributes events fromq T = 0 to finiteq T negative interference contribution shifted towards larger q T (uncertainty more realistic due to same effect). N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

21 Precision predictions for gg ( H) γγ signal-background interference NLO+NLL q T resummation for gg( H) γγ interference L. Cieri, F. Coradeschi, D. de Florian, N. Fidanza arxiv: ΔmH (MeV) H q Tmax (GeV) Resummed prediction (dark blue) of q T -vetoed cross section yields smaller mass peak shift than fixed-order result (red), compatible with zero at low end, as the ratio of real interference R/S becomes small for small qt,max H ΔmH (MeV) H q Tmin (GeV) Resummed prediction of q T -region above veto stable at small q T again brought about by redistribution of events from q T = 0 to finite q T. N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

22 Precision predictions for gg ( H) γγ signal-background interference gg ( H) γγ full NLO (α 3 s ) J. Campbell, M. Carena, R. Harnik, Z. Liu arxiv: (building on L. Dixon, M.S. Siu arxiv:hep-ph/ and L. Dixon, Y. Li arxiv: ) rate: 2%, O(40%) scale uncertainty, kinematic dependence studied 6 gg h 125 GeV ΓΓ BW 0.2 dσ dmγγ pb GeV Rh int Full.Int I h int Interference m h m h m ΓΓ GeV Higgs width bounds from total rate change may be feasible N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

23 Precision predictions for gg ( H) V V signal-background interference Signal: (latest talk of Massimiliano) gg H cross section at NLO QCD with finite t and b mass effects (important for off-shell Higgs with M V V 2M t: 5 10% correction) (scale uncertainty: 10 15%) Djouadi, Spira, Zerwas, Graudenz ( ); N 3 LO in soft expansion with M t (scale uncertainty 3%) C. Anastasiou, C. Duhr, F. Dulat, F. Herzog, B. Mistlberger arxiv: ; NLO EW corrections important for off-shell Higgs (8% at M V V 500 GeV) A. Bredenstein, A. Denner, S. Dittmaier, M. Weber arxiv:hep-ph/ (also arxiv: ) Background: pp ZZ and pp WW at NNLO QCD with massless quarks (scale uncertainty 3%), F. Cascioli, T. Gehrmann, M. Grazzini, S. Kallweit, P. Maierhofer, A. von Manteuffel, S. Pozzorini, D. Rathlev, L. Tancredi, E. Weihs arxiv: and T. Gehrmann, M. Grazzini, S. Kallweit, P. Maierhofer, A. von Manteuffel, S. Pozzorini, D. Rathlev, L. Tancredi arxiv: gg VV enters pp VV at O(α 2 sα 2 ) (NNLO QCD correction to pp VV) with 20 25% (LO!) scale uncertainty; O(α 3 s α2 ): unknown gg VV NLO QCD K-factor, but expected to be similar to signal ( 1.6); confirmed by gg ZZ NLO QCD calculation in massless quark approximation (see next page) 11 17% (9 12%) NNLO QCD correction to pp ZZ (WW) for s = 7 14 TeV gg VV contributes to full NNLO correction to pp ZZ (WW) with 60% (35%) NLO QCD correction to gg VV is of similar size or larger than residual scale uncertainty of pp VV at NNLO QCD calculation is important and by a similar argument the calculation of the NLO QCD correction to signal-background interference N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

24 Precision predictions for gg ( H) V V signal-background interference Work towards gg ( H) V V signal-background interference and gg V V continuum background beyond leading order, i.e. beyond O(α 2 s): NLO and NNLO calculation for gg ( H) WW lνlν interference with M H = 600 GeV in soft-gluon approximation (very good accuracy for inclusive signal cross section) M. Bonvini, F. Caola, S. Forte, K. Melnikov, G. Ridolfi arxiv: interference K-factors are generally very similar to signal K-factors (also for kinematic distributions) Soft gluon resummation to all orders for gg ( H) ZZ lll l interference, 100 GeV < M ZZ < 1000 GeV, effects signal like C. Li, H. Li, D. Shao, J. Wang arxiv: Technical bottleneck for unapproximated gg VV calc. at NLO: two-loop virtual corrections Two-loop gg VV 4 leptons amplitudes with massless quarks calculated by two groups: F. Caola, J. Henn, K. Melnikov, A. Smirnov, V. Smirnov arxiv: A. v. Manteuffel, L. Tancredi arxiv: Calculation of NLO gg ZZ cross section in model where Z bosons only couple to t quarks in s/m 2 t expansion (LO) yields K-factor of for 180 GeV < M ZZ < 340 GeV (LO QCD comparison with exact M t: M t poor for M ZZ 300 GeV) K. Melnikov, M. Dowling arxiv: Calculation of NLO gg ZZ (W W ) cross section in massless quark approximation yields K-factor of ( , jet veto!) F. Caola, K. Melnikov, R. Röntsch, L. Tancredi arxiv: (arxiv: ), gg W W : no t b loop graphs O(10%) missing N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

25 Precision predictions for gg ( H) V V signal-background interference 2-loop calculation with full top mass dependence beyond current capabilities for continuum background amplitude Approximate using method of expansion by regions V.A. Smirnov et al.: Large Mass Expansion (LME): expand in s/m 2 t, formally valid for s < m 2 t, but extrapolation to s m 2 t feasible with reasonable accuracy ( : 10% 20%) gg ZZ: first-order expansion by Dowling, Melnikov ( ), suppressed Vec. t tz coupling is missing gg ZZ: recent, complementary extensions to high orders ( 6) in s/m 2 t : J. Campbell, K. Ellis, M. Czakon, S. Kirchner arxiv: on-shell Z s: M ZZ > 2M Z, extrapolation to s m 2 t F. Caola, M. Dowling, K. Melnikov, R. Röntsch, L. Tancredi arxiv: off-shell Z s including leptonic decays for s (2m t) 2 N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

26 Precision predictions for gg ( H) V V signal-background interference F. Caola, M. Dowling, K. Melnikov, R. Röntsch, L. Tancredi LO 4-lepton invariant mass distribution (massive: LME vs. exact), left: background only, right: interference dσ LO massive /dm4l [fb/10 GeV] e 05 6e 05 4e 05 2e /m 4 t 1/m 6 t 1/m 8 t Exact LHC13, µ = m4l/ m4l [GeV] dσ LO/dm4l intf [fb/10 GeV] LHC13, µ = m4l/2 Massive+massless Massless Massive m4l [GeV] N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

27 Precision predictions for gg ( H) V V signal-background interference F. Caola, M. Dowling, K. Melnikov, R. Röntsch, L. Tancredi 4-lepton invariant mass distributions, interference, left: with factor-2 scale variation (lower panel & right: K-factor) dσ/dm4l [fb/10 GeV] LO intf, 13 TeV NLO m4l [GeV] Kintf 3 Massless+massive 2.5 Massive LHC13, µ = m4l/ m4l [GeV] m 4l 2m t: K signal K bkg K intf m 4l 2M Z: K intf different from K signal and K bkg K intf K signal K bkg for full considered m 4l range N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

28 Precision predictions for gg ( H) V V signal-background interference J. Campbell, K. Ellis, M. Czakon, S. Kirchner Improving naive LME with 1. Conformal Mapping, Padé approximants (superior, selected) 2. Rescaling with exact LO result Test with H signal: Comparison (improved) LME vs. exact for virtual NLO corrections: left: 1., right: 2. similar behaviour found when comparing for LO gg ZZ continuum N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

29 Precision predictions for gg ( H) V V signal-background interference J. Campbell, K. Ellis, M. Czakon, S. Kirchner Uncertainty on NLO interference due to improved LME ( 20% on approximated part): N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

30 Precision predictions for gg ( H) V V signal-background interference J. Campbell, K. Ellis, M. Czakon, S. Kirchner Full prediction and ratio of K-factors for interference and signal: N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

31 Matrix element parton shower matching/merging [LO(+partons)]+PS versus LO+PS SHERPA+OPENLOOPS: gg ( H) Y vs. in addition gg Yg and qg Yq (Y l ν l l ν l, quark-loop amplitudes) merged with PS; harder p T spectrum, overall: 10% effect from multi-jet merging Höche, Krauss, Pozzorini, Siegert arxiv: and YR4 (left fig.) NLO+PS versus NLO gg ZZ 2l2l (without Higgs), PS effects for trans. mom. obs. (p T,4l, p T,j1 ), but not for incl. obs. (M 4l, φ ll ) S. Alioli, F. Caola, G. Luisoni, R. Röntsch arxiv: (right fig.) gg ( H) γγ including interference available in SHERPA: fixed order and matched to PS (MC@NLO) S. Höche et al., ATLAS studies C. Becot, L. Fayard, et al. ATL-PHYS-PUB t t r s P P P P P P t dσ/dp T [pb/gev] 4l ratio LHC 13 TeV µ = m 4l /2 PWHG LHE PWHG+PY8 SCALUP< 50 GeV NLO p T [GeV] 4l N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

32 Implementing NLO in MC tools Automated LO MG5 AMC (OLP MADLOOP): Hirschi, Mattelaer arxiv: similar capability in SHERPA+OPENLOOPS (e.g. arxiv: ) and GOSAM (e.g. arxiv: , arxiv: )... Implementing NLO in MC tools POWHEG: Alioli, Caola, Luisoni, Röntsch arxiv: MG5 AMC: in progress Hirschi, Mattelaer, Vryonidou, NK, Shivaji, Mandal,... Method 1: reweighting (arxiv: ) Method 2: direct integration in MADFKS Feasibility study for gg (γ e + e )(γ µ + µ ) completed SHERPA: in progress Kuttimalai,... (Catani-Seymour) HERWIG7+GOSAM: in progress... N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

33 Summary H ZZ,WW in ggf & LHC: O(10%) off-shell high-mass Higgs signal contribution with large Higgs(-Higgs)-continuum interference: now taken into account (rather than cut away), provides complementary physics information (similar at high-energy linear collider) gg H ZZ, W W 4 leptons: signal-background interference studied in detail, mature MC tools available at LO; complete NLO calculations available (2-loop multi-scale!, still some approx.), PS matching demonstrated First analysis of interference (& Higgs width bounds) for pp H ZZ + jet Studies of heavy Higgs-light Higgs-background interference effects in gg H VV, complementary studies for VBF and linear collider Direct Higgs width measurement at LHC limited by mass resolution: Γ H < 600 Γ SM H high-mass Higgs tail not Higgs width dependent provides complementary constraints on Higgs couplings and Higgs width Γ H (when combined with on-peak data) Assuming no E-dependence of relevant Higgs couplings, a bound on Γ H can be obtained; optimise bound with fully differential discriminant (Matrix Element Method) LHC Run 1: CMS: Γ H < 5.4 Γ SM H, ATLAS: Γ H < [4.5,7.5] Γ SM H (95% CL) H γγ: interference-facilitated bound Γ H < 15 Γ SM H (14 TeV, 3 ab 1, 95% CL) LHC Run 2: improved bounds (ggf & VBF), high-mass H VV EFT and BSM benchmark studies N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34

34 Future directions Tools: high-mass NLO gg V V (exact?) matched/merged with PS public event generators for experimental studies (HERWIG7, MG5 AMC, POWHEG, SHERPA,...) Comparing NLO+PS with (merged) LO+PS predictions qg effects at NLO (overlap with pp N 3 LO) finite top mass corrections EW corrections BSM/EFT constraints N. Kauer Theory Higgs: Lineshape and Interference Higgs Hunting 2017 Orsay Paris 24 July / 34