Higgs Production with a Jet Veto at NNLL + NNLO

Transcription

1 Higgs Production with a Veto at NNLL + NNLO discussion with CMS arxiv:1.80 I. Stewart, with C.Berger, C.Marcantonini, F. ackmann, W.Waalewijn 1

2 Focus on H WW ν ν early discovery channel at LHC dominant channel in evatron limits for 130 GeV evatron Run II Preliminary, <L> = 5.9 fb -1 CDF+DO " [fb] 5 3 qq! qqh bb! h qb! qth qq! Wh evlhc Higgs working grou gg! h qq! Zh SM Higgs roduction gg,qq! tth LHC m h [GeV] 95% CL Limit/SM Factorization and SCE 1 LEP Exclusion Exected Observed ±1! Exected ±! Exected evatron Exclusion Higgs Production Channe SM=1 evatron Exclusion July 19, 0 Dominant channels at LHC are 1 Gluon fusion: gg H Vector-boson fusion: msm H (GeV/c Higgs roduction ) " [fb] 5 1 Gluon fusion: 3 qq! qqh Higgs Dominant channels at LHC are gg H qq! Wh gg! h " [fb] 5

3 95% CL Limit/SM 3 LEP Excl. CDF Run II Preliminary, <L> = fb -1 WH+ZH+VBF!jjbb.0 fb -1 Obs WH+ZH+VBF!jjbb.0 fb -1 Ex H!"".3 fb -1 Obs H!"".3 fb -1 Ex ZH!llbb 5.7 fb -1 Obs ZH!llbb 5.7 fb -1 Ex WH+ZH!MEbb 5.7 fb -1 Obs WH+ZH!MEbb 5.7 fb -1 Ex WH!l#bbj 5.7 fb -1 Obs WH!l#bbj 5.7 fb -1 Ex H!$$ 5. fb -1 Obs H!$$ 5. fb -1 Ex WH!l#bb3j 5.6 fb -1 Obs WH!l#bb3j 5.6 fb -1 Ex H!WW 5.9 fb -1 Obs H!WW 5.9 fb -1 Ex Combined Obs Combined Ex 3 3 b) b) -1 DØ 5. -1fb DØ 5. fb Data Bkgd. syst. Signal Z+jets Diboson W+jets Multijet tt Data Bkgd. syst. Signal Z+jets Diboson W+jets Multijet tt 1!"#$%&'($)*+$'#,&"-).)/01%3&)56 SM=1 July 19, (GeV/c ) [CDF] Number of jets 6 Number of jets [DØ (arxiv:01.81)] [DØ (arxiv:01.81 evatron excludes 158 GeV 175 GeV at 95% CL Analyses divide data into 0-jet, 1-jet, and -jet samles Dominant sensitivity comes from 0-jet (1-jet) samle Setting limits requires reliable redictions and theory uncertainties (C.Paus, LNS colloq.) A Frank ackmann (MI) Higgs Production with a Central Veto :;;<&(=1>(.?@./%.?/ 789 B(&@$?C$C(C1=.$@.;?&(;=1(.?@11&@.?/(D$&&($?/1 3

4 H WW vs. t t WWb b 1 1 : to 0 0 t t t t t t Large Background from o Decays H H W W W W W W W W b b b b ν ν ν ν ν ν jets Veto Veto events events with with central central jets, jets, measure measure H( H( WW) WW) + 0+ jets 0 jets ν ν Frank Frank ackmann ackmann (MI) (MI) Higgs Higgs Production Production with awith Central a Central Veto Veto / 6 (Sensitivity dominated by 0-jet samle)

5 How to Veto Central s Conventional: Algorithm Conventional: algorithm Search for jets and require jet evatron: 0 GeV LHC: 5 GeV Alternative: Event Shae Vetoes Search for jets and require < < Comlicated hase-sace restrictions Alternative: Event shae Alternative: Event shae Measure beam thrust of each event Measure beam thrust for of each event = = k e ηk k e ηk = = Ek Ek z k k k z k k k Ek z k = k e ηk = k k and require < and require < Better suited to analytic calculations Better suited to analytic calculations Nice for higher order calculations jet jets Frank ackmann (MI) Higgs Production with a Central Veto / 6 Frank ackmann (MI) Higgs Production with a Central Veto / 6 5

6 veto restricts ISR, gives double logs L =ln or L =ln σ( ) 1 σ( ) 1 3αs Aroriate corresondence: π 3αs π t ln +... ln +... σ( )/σ( ) GeV corresonds to NNLO sectra close, agree to 7% E = 7 ev = 165 GeV = = ( = m /) H( /) [GeV] 0 GeV in conventional jet veto 0 GeV in conventional jet veto 6

7 veto restricts ISR, gives double logs L =ln or L =ln σ 0-jet = 1 + α s L + αsl + αsl α s L + αsl 3 + αsl α s + αsl + αsl αsl + αsl αs + αsl αsl αs

8 veto restricts ISR, gives double logs L =ln or L =ln Fixed Order to NNLO FEHiP, HNNLO: Numerical fully differential NNLO cross section for gg H [Anastasiou, Melnikov, Petriello; Grazzini] LO NLO NNLO σ 0-jet = 1 + α s L + αsl + αsl α s L + α sl 3 + α 3 sl α s n 1 ( ) + α sl + α 3 sl α sl + α 3 sl α sn ( ) + α 3 sl α 3 sl α 3 s

9 veto restricts ISR, gives double logs L =ln or L =ln Fixed order NNLO studies rization and SCE Higgs Veto Calculation Results [Anastasio et al. arxiv: ]: t Veto in Current heory Predictions Factorization and SCE Higgs Veto Calculation Results Factorization and SCE Higgs Veto Calculation Results Fixed-order studies at NNLO heory Uncertainties Used at evatron [Catani, de Florian, Grazzini; Anastasiou et al.] FEHiP, HNNLO: Numerical fully differential NNLO cross section for gg H η =.5 heory Uncertainties Used at evatron [Anastasiou, Dissertori, Stöckli (arxiv: )] MC@NLO Higgs has b large K [Anastasiou Relative uncertainties for W + W ± Higgs [CDF numbers [CDFfrom numbers arxiv:07.587] from arxiv:07.587] veto roduction leads to with large0 double jets verylogarithms different from (if inclusive H m Veto veto imoses strong restriction on hase sace WW WWgg Calculation gg H + 0H jets + 0ggjets H Results gg+ 1 jets H + 1 jets Causes large double logarithms α n s lnm n ( σ( cu Must be resummed ) 1 α sc A ln Scale 7.0% (HNNLO) 3.5% (HNNLO) Scale 7.0% (HNNLO) 3.5% (HNNLO) 7% scale uncertainty +... π m PDF Model 7.6% 17.3% H PDF Model 7.6% Signal cross 17.3% section [Extracted sensitive does from Catani, to details not account Florian, of jet Grazzini algorith (he otal 6.0% (MCFM) otal 6.0% (MCFM) Need Frank ackmann to be (MI) summed for A New reliable for large Aroach toredictions logs Veto s at the LHC and un Relative uncertainties for W + W ± s Used at evatron [Anastasiou, Melnikov, Petriello; Grazzini] rrently + need to rely on arton shower MCs W ± [CDF numbers from arxiv:07.587] sum leading heory uncertainties double are logarithms taken from fixed-order calculations factor [Anastasiou et al.] Sof W Je initia 9

10 veto restricts ISR, gives double logs L =ln or L =ln LO Parton Shower NLO eg. MC@NLO is NLO+LL σ 0-jet = 1 + α s L + α sl + α 3 sl eg. Pythia is LL (+ tuning) + α s L + α sl 3 + α 3 sl α s n 1 ( ) + α sl + α 3 sl α sl + α 3 sl α sn ( ) + α 3 sl α 3 sl α 3 s +... LL

11 veto restricts ISR, gives double logs L =ln or L =ln LO Our calculation: NLO NNLL + NNLO NNLO σ 0-jet = 1 + α s L + α sl + α 3 sl α s L + α sl 3 + α 3 sl α s n 1 ( ) + α sl + α 3 sl α sl + α 3 sl α sn ( ) + α 3 sl α 3 sl α 3 s +... LL NLL NNLL two orders of summation beyond LL shower rograms 11

12 Our calculation: NNLL + NNLO [Stewart, F, Waalewijn] dσ s = H gg (µ) d dt a dt b B g (t a,µ) B g (t b,µ) S gg Function describes at the scale Hard H gg hard virtual radiation µ H B t a + t b Beam B g virtual & real energetic ISR µ B S gg B virtual & real soft radiation µ S B i (t, x) =,µ dξ ξ I ij(t, x/ξ) f j (ξ) logs give sensitivity to smaller scales Perturbation theory at each scale contributes to uncertainties 1

13 Results: 0. dσ/d [b/gev] dσ/d [b/gev] NNLL+NNLO NLL +NLO ENLL = 7 ev = 165 GeV [GeV] [GeV] E =7eV =165GeV NNLL+NNLO NLL +NLO NLL gs roduction for =165GeVattheevatron e bands show the erturbative scale uncertainties as σ( )[b] 8 6 NNLL+NNLO NLL +NLO NLL H WW t t E =7eV =165GeV [GeV] large K factors (~-3) in fixed order results are reduced by log + resummation π theory error bands overla, come from varying µ H,µ B,µ S E =7eV =165GeV [GeV] 13

14 Large 8 E = 7 ev = 165 GeV without jet veto, reroduce NNLO uncertainties σ( ) [b] 6 σ( ) [b] NNLL(no π )+NNLO NNLO(µ = ) [GeV] E = 7 ev = 165 GeV [GeV] NNLL+NNLO NNLO NNLL + NNLO with π summation (default) vs. NNLO (µ = /) With π summation central values agree at large Increases cross section Almost exactlyreroduces fixed NNLO at conventional µ = / summation reduces total cross section scale uncertainty (to % at LHC) Smaller uncertainty Frank ackmann (MI) Higgs Production with a Central Veto π 1

15 δσ [%] σ( )[b] 0 Small E =7eV =165GeV [GeV] [GeV] =165GeV NNLL+NNLO NNLO result for the Higgs roduction cross section as a NNLL+NNLO evatron. he bands show the erturbative scale NNLO oss section. 0 he right lot shows the same informa- NLO central 0 value. NNLO not reliable for small logs are large, NNLL central value lower than NNLO (artly accounted for PS) δσ [%] [GeV] E =7eV =165GeV NNLL+NNLO NNLO 0 50 σ( )[b] scale uncertainty at 8 6 NNLL+NNLO is -0% (evatron uncertainty slightly E =7eV larger, and greater =165GeV than 7% that is currently used) NNLL+NNLO NNLO 15

16 Small individual scale variations all revious lots show enveloe of the three searate scale variations σ( ) [b] 8 6 E = 7 ev = 165 GeV µ H µ B µ S µ [GeV] µ B and µ S dominate for small µ H µ B µ S 0 60 [GeV] 80 0 δσ [%] [GeV] 0 30 E = 7 ev = 165 GeV µ H µ B µ S [GeV] 16

17 Discussion: How should the results be used? Reweigh the artonic beam thrust sectrum in Monte Carlo to NNLL+NNLO. hen use it to analyze jets with a standard method. (add hadronization, underlying event,... ) Use MC to translate the NNLL+NNLO error band into an error for the 0-jet samle. When samle is divided into jet bins, theory errors are a matrix eg. 0, 1 eg. 0, 1, jets jets σ 0 σ 0, 1 σ 0, 1 σ 1 σ 0 σ 0 σ 0 σ 0 σ 01 σ 0, σ 01 σ 1 σ 1, σ 0 + σ incl smaller incl. uncertainty constrains sum of all entries σ 0, σ 1, σ 17

18 Validation? Other otions? Drell-Yan airs from validation. l + γ,z with a jet veto should be used for l + l + Directly P b measure P a beam thrust (imortant on its own). P b P a b a P b X l l ell-yan roduction. dσ/dq(τ δ(dσ/dq) B ) [b/gev] [%] E = 7 ev Q = m Z (b) Drell-Yan near threshold. 0 no g scale unc. x 1 PDF+α sing. NLO s 1 E NNLL 80 =1.96 ev τ NLL B =0.1 P a 0 LL sing. NLO QτQ B [GeV] [GeV] δ(dσ/dq) [%] (d) Dijet roduction near threshold. 0 P b P a b (c) Isolated Drell-Yan. scale unc. PDF+α 1 s no g 0 50 E =7eV x 1 τb sing. NLO Q [GeV] (e) Isolated NNLL dijet roduction. a P b 18

19 heory Plans: A calculation of the Higgs + 0-jet cross section at one higher order (N3LL) is feasible. Only a missing loo calculation. his will hel reduce the erturbative uncertainty. Similar calculations can be carried out for Higgs + 1 jet. his work is already in rogress. What do you need? Wish list? ables with results for a large number of mh values? Stand alone code that can be run on demand? 19

20 Backu 0

21 Signal and Background Exected WW eνµν events in 1 fb 1 [ALAS arxiv: ] Cut H WW t t WWb b WW Z ττ W + jets Leton selection miss > 30 GeV Z ττ rejection Central jet veto b-jet veto M < 600 GeV φ < π/ 50.6 ±.5.3 ± ±.7 < ± 38 Central jet veto essential to eliminate huge t t W W b b background Main irreducible background from W W 1