Higgs Production with a Jet Veto at NNLL+NNLO

Transcription

1 Higgs Production with a Jet Veto at NNLL+NNLO Wouter Waalewijn UCSD West Coast LHC heory Meeting December, 20 In collaboration with: Carola Berger, Claudio Marcantonini, Iain Stewart and Frank ackmann

2 Higgs at LHC and evatron gg H W W l ν lν Strong discovery otential Large 40 : 1 background from t t W W b b Cannot reconstruct Higgs invariant mass (ν ν)

3 Jet Veto b-veto Higgs at LHC and evatron t LHC use jet veto to obtain 0-jet signal samle gg H W W l ν lν 1 Run jet algorithm to find all jets in the event 2 Veto Strong all events discovery having otential jets with Large > cut and 40 : η 1 background < η cut from t t W W b b Cannot CMS: reconstruct cut Higgs invariant mass (ν ν) = 15 GeV, η cut =2.5 (9 ) UseALAS: jet veto to cut remove = 20t t GeV, background η cut =4.8 (1 ) 1 JetRun vetoareduces jet algorithm t t background by factor Veto all events that have a jet with jet > cut and η jet < η cut Frank ackmann (MI) A New Aroach to Veto Jets at the LHC / 22 CMS: cut = 25 GeV, η cut = 2.5 ALAS: cut = 20 GeV, η cut = 4.8 [ALAS arxiv: ] η =0 η =0.5 η =1 η =2.5 η =4.8 η = (beam)

4 Z+jets Z+jets b-veto 500 Diboson W+jets Diboson W+jets Multijet Multijet 400 tt [ALAS arxiv: ] tt Higgs at LHC and evatron gg H W W l ν lν 1 0 Run jet algorithm to find all jets in the event 0 2 Veto Strong all events discovery having otential jets 0 with Large > cut and 40 : η 1 background < η cut M min (GeV) from t t W W b b Cannot CMS: reconstruct cut FIG. : he M Higgs invariant mass (ν ν) = 15 GeV, η cut =2.5 (9 min channels. ) UseALAS: jet veto to cut fitting. remove = 20t t GeV, background η cut =4.8 (1 ) 1 JetRun vetoareduces jet algorithm t t background 3 by factor 400! 2 Veto all events that have a jet -1 Data with jet > 1.2 cut and η jet a) DØ 5.4 fb < η cut Bkgd. syst. Signal -1 b) DØ 5.4 fb Data 4 Bkgd. syst. Signal Frank ackmann (MI) A CMS: cut 1New Aroach to Veto Jets atz+jets the LHC Z+jets 3 / 22 = 25 GeV, η cut Diboson Diboson = 2.5W+jets 3 W+jets 0.8 ALAS: cut = 20 GeV, η cut Multijet Multijet tt tt 0.6 = evatron excludes m H GeV at 95% CL 0.2 Sensitivity dominated by 0-jet samle cut Jet Veto t LHC use jet veto to obtain 0-jet signal samle Events / 200 = 15 GeV, η cut 0 = Events / η =0 η =0.5 1 η = M min (GeV) η =2.5 at final selection in linear (a) and logarithmic (b) scale for the combination of e + e, µ + µ, and e ± µ he signal is shown for mh=165 GeV and is scaled to the SM rediction for the combination of Higgs boson roduction from gluon fusion, vector boson fusion, and associated roduction. he systematic uncertainty is shown after Number of jets η =4.8 η = (beam) Number of jets [DØ (arxiv: )]

5 Jet Vetos and ISR Beam hrust and Beam Functions NNLL Results for Drell-Yan 0-Jet Higgs Production gg H WW W Wwith 00Jets Jets MC@NLO Jet b W + Jet a η cut =2.5 [Anastasiou, Dissertori, Stöckli (arxiv: )] η cut =2.5 [Anastasiou, Dissertori, Stöckli, Webber] Higgs roduction with 0 jets very different from inclusive Higgs roduction Jet veto imoses strong restriction on hase sace Causes large double logarithms α n s lnm 2n ( cut /m H) Must be resummed Signal cross section sensitive to details of jet algorithm Frank ackmann (MI) A New Aroach to Veto Jets at the LHC / 22 W Jet veto restricts initial-state radiation

6 Jet Vetos and ISR Beam hrust and Beam Functions NNLL Results for Drell-Yan 0-Jet Higgs Production gg H WW W Wwith 00Jets Jets MC@NLO Jet b W + Jet a η cut =2.5 η cut =2.5 Jet veto restricts initial-state radiation [Anastasiou, Dissertori, Stöckli (arxiv: )] [Anastasiou, Dissertori, Stöckli, Webber] Jet Higgs veto roduction leads to with large0 double jets verylogarithms different from (if inclusive cut Higgs roduction m H ) Jet veto imoses strong restriction on hase sace σ( cut Causes large double logarithms α n s lnm 2n ( /m H) ) 1 2α sc A ln 2 cut + 2α2 s C2 A ln 4 cut +... Must be resummed π m H π 2 m H [Extracted from Catani, de Florian, Grazzini (he-h/ )] Signal cross section sensitive to details of jet algorithm Need to be summed for reliable redictions and uncertainties Frank ackmann (MI) A New Aroach to Veto Jets at the LHC / 22 Parton-shower Monte Carlo only sums leading logs W

7 Definition of Beam hrust We want to sum jet veto logs to higher order W + Phase sace is comlicated for jet algorithm Use beam thrust: Jet b Jet a cm = k k e ηk = k (E k z k ) W

8 Definition of Beam hrust We want to sum jet veto logs to higher order W + Phase sace is comlicated for jet algorithm Use beam thrust: Jet b Jet a cm = k k e ηk = k (E k z k ) W ye of radiation Momentum scaling Contribution to cm E k, z k m H m H

9 Definition of Beam hrust We want to sum jet veto logs to higher order W + Phase sace is comlicated for jet algorithm Use beam thrust: Jet b Jet a cm = k k e ηk = k (E k z k ) W ye of radiation Momentum scaling Contribution to cm E k, z k m H m H Forward energetic E k z k m H m H

10 Definition of Beam hrust We want to sum jet veto logs to higher order W + Phase sace is comlicated for jet algorithm Use beam thrust: Jet b Jet a cm = k k e ηk = k (E k z k ) W ye of radiation Momentum scaling Contribution to cm E k, z k m H m H Forward energetic E k z k m H m H Central energetic E k m H, z k m H m H

11 Definition of Beam hrust We want to sum jet veto logs to higher order W + Phase sace is comlicated for jet algorithm Use beam thrust: Jet b Jet a cm = k k e ηk = k (E k z k ) W ye of radiation Momentum scaling Contribution to cm E k, z k m H m H Forward energetic E k z k m H m H Central energetic E k m H, z k m H m H Require cm cut cm m H: Allows soft and forward energetic but not central energetic radiation Central jet veto

12 Beam hrust vs Jet Algorithm σ( cm cut )/σ(cut ) cut cm cut = cut cm cut = mh(cut cm cut = /mh) 2 mh(cut /mh)2 [GeV] E cm = 1.96 ev Comare to jet algorithm veto cut From LL results cut cm m H σ( cm cut )/σ(cut ) ( cut ) 2 m H E cm = 7 ev cut cm cut = cut cm cut = mh(cut cm cut = /mh) 2 mh(cut /mh)2 [GeV] [Using FEHiP, thanks to F. Petriello] Corresondence at NNLO within 3% for evatron and 7% for LHC

13 Beam hrust vs Jet Algorithm σ( cm cut )/σ(cut ) cut cm cut = cut cm cut = mh(cut cm cut = /mh) 2 mh(cut /mh)2 [GeV] E cm = 1.96 ev Comare to jet algorithm veto cut From LL results cut cm m H σ( cm cut )/σ(cut ) ( cut ) 2 m H E cm = 7 ev cut cm cut = cut cm cut = mh(cut cm cut = /mh) 2 mh(cut /mh)2 [GeV] [Using FEHiP, thanks to F. Petriello] Corresondence at NNLO within 3% for evatron and 7% for LHC Comare Higgs to t t background (using Pythia) cut 20 GeV and cm cut 20 GeV with similar number of signal events Surrisingly, this doesn t obey the LL corresondence

14 Beam hrust Factorization heorem Sum large α n s lnm ( cm /m H ) using: Jet b W + Jet a Factorization theorem for cm m H [Stewart, ackmann, WW (arxiv: )] Derived using -Collinear Effective heory W dσ = H gg (m t, m H, µ) dy dt a B i (t a, x a, µ) dt b B j (t b, x b, µ) d cm ( S B cm e Y t a + e Y t ) [ ( b ΛQCD, µ 1 + O m H Q, )] cm m H H hard function virtual hard corrections µ H m H B beam function virtual & real energetic ISR µ B cm m H S soft function virtual & real soft radiation µ S cm Each function deends on only one scale use RGE to sum large logs

15 Higgs Production for Small Beam hrust evatron: dσ/dcm [b/gev] cm [GeV] E cm = 1.96 ev NNLL+NNLO NLL +NLO NLL σ( cm cut ) [b] NNLL+NNLO NLL +NLO NLL cut cm [GeV] E cm = 1.96 ev Letonic decay not included (multily by branching ratio) Resummed erturbation series converges Radiation eaked at small cm 5 GeV Uncertainty bands are enveloe of varying µ H, µ B and µ S searately

16 Higgs Production for Small Beam hrust LHC at 7 ev: dσ/dcm [b/gev] E cm = 7 ev cm [GeV] NNLL+NNLO NLL +NLO NLL σ( cm cut ) [b] NNLL+NNLO NLL +NLO NLL E cm = 7 ev cm cut [GeV] Letonic decay not included (multily by branching ratio) Resummed erturbation series converges Radiation eaked at small cm 5 GeV Uncertainty bands are enveloe of varying µ H, µ B and µ S searately

17 Comarison to Fixed Order σ( cm cut ) [b] E cm = 7 ev NNLL+NNLO NNLO cm cut [GeV] LHC at 7 ev: δσ [%] NNLO evaluated at conventional µ = m H / cm cut [GeV] Central values differ by 20% at cm cut = 20 GeV 60% at cm cut = GeV NNLO scale variation underestimates uncertainty for small cm cut E cm = 7 ev NNLL+NNLO NNLO 40 50

18 Comarison to Fixed Order evatron: E cm = 1.96 ev E cm = 1.96 ev σ( cm cut ) [b] cut cm [GeV] NNLL+NNLO NNLO δσ [%] cm cut [GeV] NNLL+NNLO NNLO 40 50

19 Comarison to Fixed Order [CDF+DØ (arxiv: )] evatron: Imlications for evatron Higgs exclusion δσ [%] cm cut [GeV] E cm = 1.96 ev NNLL+NNLO NNLO evatron uses ±7% scale uncertainty at cut 20 GeV from NNLO [Anastasiou, Dissertori, Grazzini, Stöckli, Webber (arxiv: )] comared to ±12% at cm cut 20 GeV uncertainty from our NNLL+NNLO Reweighting arton shower (LL) with NNLO might imrove central value but cannot yield better uncertainties than NNLL+NNLO

20 Conclusions Jet veto needed to remove t t background in H W W lνl ν. Strong jet veto leads to large logs in the cross section logs must be summed for reliable redictions and uncertainties Beam thrust cm easier hase sace restrictions than jet algorithm can sum beyond leading log corresondence with cut within 7% at NNLO Larger uncertainties should be taken into account in evatron Higgs bound hank you!

21 Conclusions Jet veto needed to remove t t background in H W W lνl ν. Strong jet veto leads to large logs in the cross section logs must be summed for reliable redictions and uncertainties Beam thrust cm easier hase sace restrictions than jet algorithm can sum beyond leading log corresondence with cut within 7% at NNLO Larger uncertainties should be taken into account in evatron Higgs bound hank you!