Good News for LHC Analyses

Transcription

1 Good News for LHC Analyses Not a proper unbiased theory overview Universität Heidelberg Higgs Workshop, Seattle, /29

2 Outline SFitter at LHC Weak boson fusion and supersymmetry

3 A new channel to detect H bb [Butterworth, Davison, Rubin, Salam] desperately needed after deceased tth channel one of my personal favorites in 28 q q V l H b save in boosted regime [p T 3 GeV, few % of total rate] single fat bottom jet R bb 2m h /p T.8 underlying event challenge: re-define filtered subjets difficult as hell, but very serious progress jet definition σ S /fb σ B /fb S/ B 3 C/A k SISCone

4 A new channel to detect H bb [Butterworth, Davison, Rubin, Salam] desperately needed after deceased tth channel one of my personal favorites in 28 q q V l H b save in boosted regime [p T 3 GeV, few % of total rate] single fat bottom jet R bb 2m h /p T.8 underlying event challenge: re-define filtered subjets difficult as hell, but very serious progress Parton-level/fast simulation results channels combined V ll, νν, lν NLO corrections for signal and backgrounds [bbv notorious] H vs Z mass peaks as sanity check do-do list: jet algorithm comparison? realistic b tagging? detector simulation? towards fb? keep fingers crossed! Significance (a) 2GeV R =.2 Eff = 7% 7 3GeV R =.7 Eff = 7% 2GeV R =.2 Eff = 6% 6 3GeV R =.7 Eff = 6% b Mistag Probability Significance (b) 2GeV R =.2 Eff = 7% (%) 7 3GeV R =.7 Eff = 7% (%) 2GeV R =.2 Eff = 6% (2%) 6 3GeV R =.7 Eff = 6% (2%) Higgs Mass (GeV)

5 Understanding of gg H rate [Ahrens, Becher, Neubert, Yang] old problem: corrections large [Dawson; Spira et al; Harlander, Kilgore; Anastasiou, Melnikov,...] QCD effects in low-energy Lagrangian C t (mt 2, µ2 ) G µν,ag a µν H/v Wilson coefficient of QCD part of operator C(µ 2 ) = + X αs(µ 2 «n «) c n c = N c log 2 q2 4π µ n 2 + π2 6 strong-coupling series of hard function in σ gg H C(m 2 H, m2 H ) 2 = +5.5α s+7.2α 2 s C( m 2 H, m2 H ) 2 = +.4α s+.5α 2 s π 2 terms resummable as part of funny logarithm [not all π 2 terms] time-like scale logs general problem of 2 processes [similar for Drell-Yan] beneficial effect mostly on error analysis [from scale dependence] ask Sally or Michael later fixed order π 2 resummed + threshold resummed LO NLO NNLO

6 Coupling extraction at the LHC [Zeppenfeld, Kinnunen, Nikitenko, Richter-Was; Dührssen et al.] optimistic LHC scenario: everything working and good data motivation: scalar little Higgs axions or radion or Higgs? light Higgs around 2 GeV: main channels (σ BR) [bb channel new] measurements: GF : H ZZ, WW, γγ WBF : H ZZ, WW, γγ, ττ VH : H b b t th : H γγ, WW, (b b)... [Butterworth, Davison, Rubin, Salam] parameters: couplings W, Z, t, b, τ, g, γ [plus masses] hope: cancel uncertainties (WBF : H WW)/(WBF : H ττ) (WBF : H WW)/(GF : H WW)... goals: Higgs vs. scalars? SM vs MSSM? doublet vs. general Higgs?

7 Coupling extraction at the LHC [Zeppenfeld, Kinnunen, Nikitenko, Richter-Was; Dührssen et al.] optimistic LHC scenario: everything working and good data motivation: scalar little Higgs axions or radion or Higgs? light Higgs around 2 GeV: main channels (σ BR) [bb channel new] measurements: GF : H ZZ, WW, γγ WBF : H ZZ, WW, γγ, ττ VH : H b b t th : H γγ, WW, (b b)... [Butterworth, Davison, Rubin, Salam] parameters: couplings W, Z, t, b, τ, g, γ [plus masses] Total width degeneracy: σ BR (g 2 p / Γ H ) (g 2 d / Γ H ) additional constraint: P Γ i (g 2 ) < Γ H Γ H min WW WW unitarity: g WWH g SM WWH Γ H max width extraction hard this analysis: Γ H = P obs Γ j g 2 (H,X) g 2 (H,X) g 2 (H,Z) g 2 (H,W) g 2 (H,τ) g 2 (H,b) g 2 (H,t) Γ H without Syst. uncertainty 2 Experiments - L dt=2*3 fb m H [GeV]

8 Before talking measurements......remember minijet veto backgrounds for WBF Higgs production t t with b tagging jet V/VV radiation off QCD 2-jet production V/VV radiation off ew 2-jet production [Barger, Cheung, Han, Zeppenfeld; Rainwater, Szalapski, Zeppenfeld] signal: color/interference structure [disconnected 2-sided DIS; Han, Valencia, Willenbrock] veto central jets above 2 3 GeV [survival probabilities between 25% and 9%] will work, don t know how well [or QCD is wrong] WBF rate measurement backbone of Higgs coupling analysis [many channels, clean structure] jet veto not used by experiments, lacking error estimate? straight-forward comparison between Monte Carlos not useful QCD simulation problem: recent progress great news large survival probabilities: fixed order [Hjjj@NLO: Zeppenfeld and friends] small survival probabilities: non-perturbative W, Z, t t backgrounds: measurement [Cranmer et al] gluon-fusion understood? [Andersen, Del Ducca, White] meaningful error estimate on horizon [jet merging: CKKW, MLM (Madgraph)]

9 Preliminary (!!!) first study [TP, Schumann, Sherpas] first test with (measurable) Z +jets channels compute jet multiplicities as function of p T,veto () parton level: exponentiation approach [checked with truncated shower approximation] P n = nn n! e n n = σ 2 Z p T,veto dp Tj3 dσ 3 dp Tj3 P veto = e n exp. model jet emission prob. (ZEW) P exp. model jet emission prob. (ZQCD) P.8.6 P P 2 P veto.8.6 P P 2 P veto P n-jet.4 P n-jet p T,veto [GeV] p T,veto [GeV] probably consistent for electroweak Z, devil is in the QCD details shown here because comments welcome

10 P P Good News Preliminary (!!!) first study [TP, Schumann, Sherpas] first test with (measurable) Z +jets channels compute jet multiplicities as function of p T,veto () parton level: exponentiation approach [checked with truncated shower approximation] P n = nn n! e n n = σ 2 Z p T,veto dp Tj3 dσ 3 dp Tj3 P veto = e n exp. model jet emission prob. (ZEW) exp. model jet emission prob. (ZQCD).8.6 P n-jet.4 P P 2 P veto.8.6 P n-jet.4 P P 2 P veto p T,veto [GeV] p T,veto [GeV] (2) CKKW merging of hard jets and parton shower only jet cuts, same renormalization scales,... ME+PS jet emission prob. (ZEW) ME+PS jet emission prob. (ZQCD) P P P n-jet P P 2 P veto P n-jet P P 2 P 3 P veto p T,veto [GeV] p T,veto [GeV]

11 P P P P Good News Preliminary (!!!) first study [TP, Schumann, Sherpas] first test with (measurable) Z +jets channels compute jet multiplicities as function of p T,veto () parton level: exponentiation approach [checked with truncated shower approximation] P n = nn n! e n n = σ 2 Z p T,veto dp Tj3 dσ 3 dp Tj3 P veto = e n exp. model jet emission prob. (ZEW) exp. model jet emission prob. (ZQCD).8.6 P n-jet.4 P P 2 P veto.8.6 P n-jet.4 P P 2 P veto p T,veto [GeV] p T,veto [GeV] (2) CKKW merging of hard jets and parton shower only jet cuts, same renormalization scales,... ME+PS jet emission prob. (ZEW) ME+PS jet emission prob. (ZQCD).8.6 P n-jet.4 P P 2 P veto.8.6 P n-jet.4 P P 2 P veto p T,veto [GeV] p T,veto [GeV] probably consistent for electroweak Z, devil is in the QCD details shown here because comments welcome give us some time, we ll beat the startup, promised

12 SFitter at LHC Parameter extraction [Lafaye, TP, Rauch, Zerwas] know-how from TeV-scale MSSM analysis [parameters from edges etc] parameters: weak-scale Higgs Lagrangian measurements: signal+background rates errors: statistics & systematics & theory questions: global structure of parameter space, secondary minima local structure of best points, error bars distributions for fewer parameters, correlations Probability maps [Baltz,...; Roszkowski,...; Allanach,...; Fittino; SFitter] fully exclusive likelihood map p(d m) over model space m local and global structure for different hypotheses Bayesian: p(m d) p(d m) p(m) with theorists bias p(m) [cosmo, BSM] frequentist: best fitting point max m p(d m) [flavor, here: cooling Markov chains] LHC aim: compute high-dimensional map p(d m) find and rank local maxima in p(d m) Bayesian frequentist dance to reduce dimensions

13 SFitter at LHC Alternative best-fit points and error bars all couplings varied around SM values g HXX = g SM HXX ( + δ HXX) δ HXX 2 means sign flip [g HWW > fixed, only broken by loops] alternative solutions for unsmeared data point observable δ HWW δ HZZ δ Hττ δ Hbb δ Htt δ Hγγ δ Hgg χ 2 /dof error bars for Standard Model hypothesis [smeared data point, no effective couplings] brand new results, only to show it can be done observable central error δ HWW δ HZZ δ Htt δ Hbb δ Hττ m H χ 2 /dof 9.9/

14 SFitter at LHC One-dimensional distributions limitations of the analysis with all errors included [true data set, no effective couplings] 3 vs 3 fb : similar cooled profile likelihoods /χ HWW /χ Htt /χ Hbb /χ /χ /χ HWW Htt Hbb pure statistics not the problem

15 SFitter at LHC One-dimensional distributions limitations of the analysis with all errors included [true data set, no effective couplings] 3 vs 3 fb : similar cooled profile likelihoods similar Bayesian probabilities /χ HWW /χ Htt /χ e Hbb /χ /χ 2.5 /χ 2. 8e e-5. 5e-5 5e-5 4e-5 2e HWW Htt Hbb pure statistics not the problem

16 SFitter at LHC One-dimensional distributions limitations of the analysis with all errors included [true data set, no effective couplings] 3 vs 3 fb : similar cooled profile likelihoods similar Bayesian probabilities pure statistics not the problem Simulating theory errors for example: scale-dependence on production rate () likelihood flat in central region [any K factor possible] (2) likelihood zero far out [QCD is perturbative!] (3) convolution with gaussian errors still flat RFit scheme [CKMfitter] log L = 2 χ2 = 2 χt d C χ d 8 >< d i d i < σ (theo) i χ d,i = d i >: d i σ (theo) i σ (exp) d i d i > σ (theo) i i error bar still the problem, e.g. gg H a la Neubert numerically hard, but possible

17 SFitter at LHC Two-dimensional correlations and effective coupings () profile likelihoods, including effective g Hgg sign of g Htt fixed, correlated to g HWW on other branch correlation of g Hbb and g HWW [loops and width] effective coupling g Hgg accessible Htt Hbb Hbb HWW HWW Htt /χ 2.5 /χ 2.5 /χ 2.5 /χ HWW Htt Htautau Hgg

18 SFitter at LHC Two-dimensional correlations and effective coupings () profile likelihoods, including effective g Hgg sign of g Htt fixed, correlated to g HWW on other branch correlation of g Hbb and g HWW [loops and width] effective coupling g Hgg accessible (2) profile likelihoods, including effective g Hγγ correlation of g Htt and g HWW on both branches still correlation of g Hbb and g HWW [width] effective coupling g Hγγ more noisy Htt Hbb Hbb HWW HWW Htt /χ 2.5 /χ 2.5 /χ 2.5 /χ HWW Htt Htautau Hgamgam two-dimensional correlations useful

19 Weak boson fusion and supersymmetry Higgs analysis beyond the Standard Model extension of Higgs analysis to BSM scenarios comparison SM-MSSM [WBF: TP, Rainwater, Zeppenfeld] help with MSSM parameters [SFitter+Higgs] hypothesis determining theory error known particles: corrections included new particles: theory error general: heavy additional states at one loop example: MSSM sectors Higgs weak strong study for BSM-Higgs analysis tanβ LHC(4fb - ): VV H ττ LEP2: e + e Zh VV h ττ M A [GeV] Technical questions [Hollik, TP, Rauch, Rzehak] vertex corrections dominant? [Djouadi & Spira] which one larger: QCD vs EW? [similar for Standard Model: Ciccolini, Denner, Dittmaier] corrections from Higgs sector? [renormalization scheme/higher orders] general phase space generator? Germans: show we can do 5254 diagrams [Hadcalc: automized IR-finite one-loop 2 3] input for MSSM-Higgs analysis

20 Weak boson fusion and supersymmetry Higgs sector corrections close to decoupling: λ 2 WWh λ hhh finite momentum, different masses Feynman diagrams [FeynHiggs] consistent self couplings effective potential [SubH] check identical limit: effective angle α eff σ/σ(ud udh) (σαeff σ full )/σ effective theory α eff.389 %.22 % full.266 % Feynman diagrams α eff.393 %.76 % full.37 % Feynman diagrams, loop-improved Z FH α eff.343 %.5 % full.228 % small corrections, even smaller uncertainty

21 Weak boson fusion and supersymmetry Higgs sector corrections close to decoupling: λ 2 WWh λ hhh finite momentum, different masses Feynman diagrams [FeynHiggs] consistent self couplings effective potential [SubH] check identical limit: effective angle α eff small corrections, even smaller uncertainty SUSY corrections QCD correstions suppressed: color flow and forward jets [no interference, like SM] mass suppression of one-loop q L q L W vertex [mg/m g ] up-down concellation in one-loop duwh vertex [T 3 Qs w 2 = /3, +5/6] electroweak corrections as expected electroweak corrections dominant diagram σ/σ [%] diagram σ/σ [%] σ O(α) σ O(α s) self energies.99 qqw + qqz qqw + qqz -.48 qqh -.26 qqh.545 WWh + ZZh box.785 box -.58 pentagon.522 pentagon -.38

22 Weak boson fusion and supersymmetry Higgs sector corrections close to decoupling: λ 2 WWh λ hhh finite momentum, different masses Feynman diagrams [FeynHiggs] consistent self couplings effective potential [SubH] check identical limit: effective angle α eff small corrections, even smaller uncertainty SUSY corrections SPSb with variable mass scale m /2 squark/gluino masses from LHC not helpful perfect decoupling at one loop typical corrections around % maximum corrections below 4% - σ/σ [%]. LEP χ ± SPSb total (µ var) total (µ fixed). Ο(α s ) (µ fixed) m /2 [GeV]

23 Outlook Some ideas trying to understand relevance of parameter analysis undisputed measurement of bottom Yukawa possible? large gg H corrections understood? QCD study of minijet veto overdue Bayesian/likelihood parameter extraction promising skipping parton densities: ask Wu-Ki skipping higher orders: ask Sally skipping non-minimal Higgs sectors: ask Tim or Graham skipping light-mssm-higgs-mass-at-two-loops-with-feynhiggs: ask Sven many promising studies in progress It s great to be back in the U.S. writing talks to the Prairie Home Companion!

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