Higgs characterisation - beyond leading order

Transcription

1 Higgs characterisation - beyond leading order Kentarou Mawatari (Vrije Universiteit Brussel and International Solvay Institutes) [arxiv: ] The FeynRules and MadGraph5 framework FeynRules model P. de Aquino, K. Mawatari (Vrije U. Brussel) amc@nlo F. Demartin, F. Maltoni, M. Zaro (UC Louvain) R. Frederix, S. Frixione (CERN) P. Torrielli (Zurich) MadWeight P. Artoisenet (Nikhef) spin2 in amc@nlo M.K. Mandal (Harish-Chandra) P. Mathews, S. Seth (Saha Inst.) V. Ravindran (CIT) Kentarou Mawatari (Vrije U. Brussel) 1 Aug. 26, 2013 SUSY2013@Trieste

2 about 50 years ago... Kentarou Mawatari (Vrije U. Brussel) 2 Aug. 26, 2013 SUSY2013@Trieste

3 July 4th, 2012 [arxiv: ] [arxiv: ] Kentarou Mawatari (Vrije U. Brussel) 3 Aug. 26, 2013 SUSY2013@Trieste

4 July 4th, 2013 Kentarou Mawatari (Vrije U. Brussel) Aug. 26,

5 Is this the Standard Model scalar boson? Kentarou Mawatari (Vrije U. Brussel) 5 Aug. 26, 2013 SUSY2013@Trieste

6 Is this the Standard Model scalar boson? determination of the Higgs Lagrangian Kentarou Mawatari (Vrije U. Brussel) 5 Aug. 26, 2013 SUSY2013@Trieste

7 Is this the Standard Model scalar boson? determination of the Higgs Lagrangian - the structure of the operators, linked to the spin/ parity of the Higgs boson Kentarou Mawatari (Vrije U. Brussel) 5 Aug. 26, 2013 SUSY2013@Trieste

8 Is this the Standard Model scalar boson? determination of the Higgs Lagrangian - the structure of the operators, linked to the spin/ parity of the Higgs boson - the coupling strength Kentarou Mawatari (Vrije U. Brussel) 5 Aug. 26, 2013 SUSY2013@Trieste

9 Is this the Standard Model scalar boson? determination of the Higgs Lagrangian - the structure of the operators, linked to the spin/ parity of the Higgs boson - the coupling strength [arxiv: ] Kentarou Mawatari (Vrije U. Brussel) 5 Aug. 26, 2013 SUSY2013@Trieste

14 Contents Introduction Higgs characterisation framework - Effective Lagrangians -- X(J=0,1,2) beyond-leading-order effects in QCD - inclusive production pp X(J P ) - unitarity-violating behavior for X(J=2) - higher order QCD effects on spin observables Summary Kentarou Mawatari (Vrije U. Brussel) 6 Aug. 26, 2013 SUSY2013@Trieste

15 FeynRules in a nutshell Christensen, Duhr, Fuks, - a Mathematica package that allows to derive Feynman rules from a Lagrangian. - allows to export the Feynman rules to various matrix element generators, e.g. MadGraph. The only requirements on the Lagrangian are: All indices need to be contracted. Locality. Supported filed types: spin-0, 1/2, 1, 3/2, and 2. Kentarou Mawatari (Vrije U. Brussel) 7 Aug. 26, 2013 SUSY2013@Trieste

16 FeynRules in a nutshell Christensen, Duhr, Fuks, - a Mathematica package that allows to derive Feynman rules from a Lagrangian. - allows to export the Feynman rules to various matrix element generators, e.g. MadGraph. The only requirements on the Lagrangian are: All indices need to be contracted. Locality. new! Supported filed types: spin-0, 1/2, 1, 3/2, and 2. [arxiv: ] see B.Oexl talk. Kentarou Mawatari (Vrije U. Brussel) 7 Aug. 26, 2013 SUSY2013@Trieste

17 Higgs Characterisation model We implemented an effective Lagrangian featuring bosons in FeynRules. X(J P =0 +,0,1 +,1,2 + ) Effective field theory approach, valid up to a cutoff scale Λ Only one new bosonic state X(JP ) at the EW scale (No other state below the cutoff Λ) Any new physics is described by the lowest dimensional operators. The parametrization is based on the recent work [Englert, Goncalves-Netto, KM, Plehn (2013)]. Kentarou Mawatari (Vrije U. Brussel) 8 Aug. 26, 2013 SUSY2013@Trieste

18 Effective Lagrangian -- spin0 allows one to recover the SM case easily. includes all possible interactions that are generated by gaugeinvariant D6 operators above the EW scale includes 0 - state couplings typical of SUSY or of generic 2HDM allows CP-mixing between 0 + and 0 states Kentarou Mawatari (Vrije U. Brussel) 9 Aug. 26, 2013 SUSY2013@Trieste

19 Effective Lagrangian -- spin0 Kentarou Mawatari (Vrije U. Brussel) 10 Aug. 26, 2013

20 Effective Lagrangian -- spin0 Kentarou Mawatari (Vrije U. Brussel) 10 Aug. 26, 2013

21 Mass and angular distributions -- spin0./bin/mg5 >import model HiggsCharac >generate p p > x0, x0 > mu- mu+ e- e+ >output >launch Kentarou Mawatari (Vrije U. Brussel) 11 Aug. 26, 2013 SUSY2013@Trieste

22 Effective Lagrangian -- spin1 The most general interactions at the lowest canonical dimension: Parity conservation implies that for X 1 for X 1+ Kentarou Mawatari (Vrije U. Brussel) 12 Aug. 26, 2013 SUSY2013@Trieste

23 Effective Lagrangian -- spin2 via the energy-momentum tensor of the SM fields, starting from D5: The E-M tensor for QED: Kentarou Mawatari (Vrije U. Brussel) 13 Aug. 26, 2013

24 Kentarou Mawatari (Vrije U. Brussel) Aug. 26,

25 All the relevant channels can be simulated in a consistent, systematic and accurate way. e.g. VBF (pp jjx) di-jet correlations Englert, Goncalves-Netto, KM, Plehn (2013) spin-0 spin-1 spin-2 Kentarou Mawatari (Vrije U. Brussel) 15 Aug. 26, 2013 SUSY2013@Trieste

26 Higher order effects in QCD The LO predictions can be systematically improved by including the effects due to the emission of QCD partons. LO Matrix-Element/Parton-Shower merging [ME+PS] full-nlo matrix element with parton-shower Kentarou Mawatari (Vrije U. Brussel) 16 Aug. 26, 2013

27 Higher order effects in QCD (I) inclusive production in pp X(J P ) spin-1 spin-0,2 Kentarou Mawatari (Vrije U. Brussel) Aug. 26, 2013 SUSY2013@Trieste 17

28 Higher order effects in QCD (I) inclusive production in pp X(J P ) spin-0,2 gg spin-1 qq The matched sample is harder than amc@nlo at large pt due to the extra 2 ME patrons in the matched sample. The different shapes are due to the different initial state. Kentarou Mawatari (Vrije U. Brussel) 17 Aug. 26, 2013 SUSY2013@Trieste

29 Higher order effects in QCD (I) inclusive production in pp X(J P ) spin-0,2 gg spin-1 qq The matched sample is harder than amc@nlo at large pt due to the extra 2 ME patrons in the matched sample. excellent agreement between ME+PS and amc@nlo The different shapes are due to the different initial state. Kentarou Mawatari (Vrije U. Brussel) 17 Aug. 26, 2013 SUSY2013@Trieste

30 Higher order effects in QCD (II) unitarity-violating behavior of models with a spin-2 state page 1/ u~ x2 u~ x2 kq g kg 1 u g 3 1 u g 3 M 2 s/λ 2 for κ q = κ g 2 diagram 1 u~ QCD=1, QED=0, QNP=1 x2 4 2 diagram 2 u~ QCD=1, QED=0, QNP=1 g 3 M 2 s 3 /m 4 Λ 2 for κ q = κ g kq u u kq u g u x diagram 3 QCD=1, QED=0, QNP=1 diagram 4 QCD=1, QED=0, QNP=1 Kentarou Mawatari (Vrije U. Brussel) 18 Aug. 26, 2013 SUSY2013@Trieste Diagrams made by MadGraph5

31 Higher order effects in QCD (II) unitarity-violating behavior of models with a spin-2 state page 1/ u~ x2 u~ x2 kq g kg κ q κ g u g u g diagram 1 QCD=1, QED=0, QNP=1 diagram 2 QCD=1, QED=0, QNP=1 2 u~ x2 4 2 u~ g 3 kq u u kq κ q =κ g u g u x diagram 3 QCD=1, QED=0, QNP=1 diagram 4 QCD=1, QED=0, QNP=1 A model with non-universal couplings dramatically changes the pt(x) spectrum. Kentarou Mawatari (Vrije U. Brussel) 19 Aug. 26, 2013 SUSY2013@Trieste Diagrams made by MadGraph5

32 Higher order effects in QCD (III) on spin observables for a spin-2 state amc@nlo σ gg /σ tot 96% scattering angle in pp X γγ Kentarou Mawatari (Vrije U. Brussel) 20 Aug. 26, 2013 SUSY2013@Trieste

33 Summary After the discovery of a Higgs-like resonance at the LHC, the main focus of the analyses now is the determination of the Higgs Lagrangian. This includes - - the structure of the operators, linked to the spin/parity of the Higgs boson. an independent measurement of the coupling strength. Our FR/MG5 Higgs Characterisation model is publicly available, which can provide a framework to perform SMS characterisation studies in a consistent, systematic and accurate way contact to [email protected] Kentarou Mawatari (Vrije U. Brussel) 21 Aug. 26, 2013 SUSY2013@Trieste

34 back-up Kentarou Mawatari (Vrije U. Brussel) 22 Aug. 26, 2013

35 Effective Lagrangian Feynman rules L = 1 2 c ακ SM g HZZ Z µ Z µ X Λ c ακ HZZ Z µν Z µν 1 Λ s ακ AZZ Z µν Z µν 1 Λ c ακ H Z Z ν µ Z µν ic α κ SM g HZZ g µν ic α κ HZZ Λ (g µνq 1.q 2 q 2µ q 1ν ) is α κ AZZ Λ µνρσq ρ 2 qσ 1 ic α κ H Z Λ [g µν(q 1.q 1 + q 2.q 2 ) q 1µ q 1ν q 2µ q 2ν ] hyp. SM : SM-like coupling to the Z bosons κ SM =1 κ HZZ =0=κ AZZ hyp. HD: coupling involving a superposition of HD operators κ SM =0 κ HZZ =1=κ AZZ c α =1 Z µν Z µν c α free and Z µν Zµν Kentarou Mawatari (Vrije U. Brussel) 23 Aug. 26, 2013 SUSY2013@Trieste

36 Mass and angular distributions -- spin1 Kentarou Mawatari (Vrije U. Brussel) 24 Aug. 26, 2013

37 Mass and angular distributions -- spin2 Kentarou Mawatari (Vrije U. Brussel) 25 Aug. 26, 2013

38 Accuracy with merging Kentarou Mawatari (Vrije U. Brussel) 26 Aug. 26, 2013

41 How can we get the spin/parity information? 1. X γγ 2. X VV* 4l 3. pp jjx 4. pp VX 5. X ττ Kentarou Mawatari (Vrije U. Brussel) 29 Aug. 26, 2013 SUSY2013@Trieste

42 Spin/parity determination 1. X γγ Kentarou Mawatari (Vrije U. Brussel) 30 Aug. 26, 2013 SUSY2013@Trieste

43 Spin/parity determination [Dell Aquilla, Nelson, PRD(1986)] 2. X VV* 4l L 0 + SM L 0 + D5 L 0 D5 = g 0 + SMV µ V µ X 0 = g 0 + D5V µν V µν X 0 = g 0 D5V µν V µν X 0 Kentarou Mawatari (Vrije U. Brussel) 31 Aug. 26, 2013 SUSY2013@Trieste

44 Spin/parity determination X 4l vs. VBF Kentarou Mawatari (Vrije U. Brussel) 32 Aug. 26, 2013 SUSY2013@Trieste

45 Spin/parity determination 3. pp jjx X/jet distributions Englert, Goncalves-Netto, KM, Plehn (2013) s = 14 TeV p Tj > 20 GeV R jj > 0.6 η j < 5 m jj > 600 GeV spin-0 spin-1 spin-2 Kentarou Mawatari (Vrije U. Brussel) 33 Aug. 26, 2013 SUSY2013@Trieste

46 Spin/parity determination 3. pp jjx di-jet correlations Englert, Goncalves-Netto, KM, Plehn (2013) spin-0 spin-1 spin-2 Δη as well as ΔΦ are the powerful observables. Kentarou Mawatari (Vrije U. Brussel) 34 Aug. 26, 2013

47 Obs-by-obs based strategy in VBF Englert, Goncalves-Netto, KM, Plehn (2013) The di-jet correlations are the most decisive, in particular to separate the different scalar coupling structures. Kentarou Mawatari (Vrije U. Brussel) 35 Aug. 26, 2013

48 Spin/parity determination 4. pp ZX Englert, Goncalves-Netto, KM, Plehn (2013) Kentarou Mawatari (Vrije U. Brussel) 36 Aug. 26, 2013

49 Spin/parity determination 5. X ττ Kentarou Mawatari (Vrije U. Brussel) 37 Aug. 26, 2013 SUSY2013@Trieste

50 TauDecay a library to simulate polarized tau decays via FeynRules/MadGraph5 Kentarou Mawatari (Vrije U. Brussel) 38 Aug. 26, 2013 SUSY2013@Trieste

51 stributions of pseudo-experiments with respect to q =lnl MEM for the case cted p-value at which hypothesis HD cα is rejected if hypothesis SM is realized, d for different choices of the likelihood function. Specific channel: X0 into 4 charged leptons nd HD(c α ) distributions of pseudo-experiments generation of X 0 µ + µ e + e with respect to q = n in Figure 13 (left) in the specific case of c α =0.5. The significance ulating the median q SM,1/2 of the SM distribution and by counting the xperiments in the HD(c α ) distribution with q<q SM,1/2. Such a fraction s with an estimate 1M pseudo-experiments of the p-value associated with N=10 with events the statistical under each test for HD(c α ) if the assumptions SM hypothesis (SM of ishd) realized. The p-value as a function of re 13 (right). e MEM can be illustrated by comparing the significance that is achieved M-based likelihood function L MEM with the significance resulting from n built upon the cross section differential in the observable O: events: ME+matching approach (validated with amc@nlo + parton shower), basic cuts on the leptons (pt > 7 GeV, y <2.4) Discriminating variable for the statistical test SM versus HD is set to the likelihood ratio, built upon 1-dimension distribution or upon the matrix elements L O = N i σ 1 HD(c α ) σ 1 SM dσ HD(c α) do (O i) dσ SM do (O i). L MEM = M HD(cα )(i) 2 (4.9) M SM (i) 2 ple, the observable likelihood O is chosen ratio based in the set of variables {m 2 likelihood, Φ, cosratio θ 1, cos based θ 2 } on 1-dim. distribution The discriminant power of each of these four variables taken on matrix separately elements using the same Monte Carlo procedure as39before, with L MEM replaced N i

52 1-dimension distributions sm HD, ca=0 HD, ca=0.5 HD, ca=0.7 HD, ca= m Z2 (GeV) sm HD, ca=0 HD, ca=0.5 HD, ca=0.7 HD, ca= sm 0.7 Figure 1: Illustration of the production andhd, decay ca=0 of a particle Xab X Z 1 Z 2 4 wit the two production angles θ and Φ 1 shown HD, in ca=0.5 the X rest frame and three decay angles θ 1, θ 0.65 and Φ shown in the Z i and X rest frames, HD, respectively ca=0.7 [39]. 0.6 HD, ca= MADGRAPH [67] implemented within the MEKD framework [88]. Different matrix element 0.5 were found to provide nearly identical performance for the processes implemented in com mon. The machine trained techniques such as boosted decision trees or Bayesian neural ne 0.45 works were also investigated. They give similar results as the matrix element approaches. Th 0.4 kinematic discriminants for the baseline analysis is built out of matrix element for the signa hypotheses taken from JHUGEN and matrix elements for the qq ZZ background taken from 0.35 MCFM Background control and systematics cos 1 We rely on MC simulation to evaluate the local density ( N/ m 4 ) of events expected as 0.7 function of the mass m 4 from the ZZ background. Following the prescription used in the pre sm 0.65 vious analysis, the cross section for ZZ production at NLO is calculated with MCFM [85 87 HD, ca=0 This includes the dominant process of qq annihilation, as well as gluon induced production 0.6 HD, ca=0.5 The theoretical uncertainties are computed HD, asca=0.7a function of m 4, varying both the QCD renor 0.55 malisation and factorization scales andhd, the PDF ca=1.0 set, following the PDF4LHC recommenda tions [89 93]. The uncertainties for the QCD and PDF scales for each final state are on averag 0.5 8%. The number of predicted ZZ 4 events and their uncertainties after the signal selectio 0.45 are given in Table To estimate the reducible (Zbb, tt) and instrumental (Z + light jets, WZ + jets) backgrounds, 0.35 Z 1 +X background control region, well separated from the signal region, is defined. In addition a sample Z 1 + reco, with at least one reconstructed lepton object, is defined for the measure 0.3 ment of the lepton misidentification probability the probability for a reconstructed object t 0.25 pass the isolation and identification requirements. The contamination from WZ in these event is suppressed by requiring the imbalance of the measured energy deposition in the transvers 0.2 plane to be below 25 GeV. The lepton misidentification probability is compared, and foun compatible, with the one derived from MC simulation. cos 2 40

53 MEM discriminator D(i) = M HD(cα )(i) 2 M HD(cα )(i) 2 + M SM (i) 2 normalized fraction of events D D HD(c =0) D SM normalized fraction of events D D HD(c =0.3) D SM normalized fraction of events D D HD(c =0.7) D SM normalized fraction of events D D HD(c =1) D SM Distribution of SM and HD events with respect to the MEM-based discriminator D Figure 12. Normalized distributions for event with respect to the MEM-based discriminant D, for specific values of the mixing parameter of c α : 0, 0.3, 0.7 and

54 Significance Fraction of pseudo-experiments q SM,1/2 HD(c =0.5) SM q =lnl q p-value q SM,1/2 Significance estimated by calculating the median of the SM distribution and by counting the fraction of pseudo-experiments in the HD distribution with Figure 13. Left: distributions of pseudo-experiments with q<q c α =0.5. Right: expected p-value at which hypothesis SM,1/2 HD cα as a function of c α and for different choices of the likelihood This fraction = expected p-value associated with the test of rejecting hypothesis HD if the SM hypothesis is realized. 42

55 Significance p-value c L MEM L m2 xl xl cos 1 xl cos 2 L m2 L cos 1 L cos 2 L The optimal significance is reached with the MEM-based likelihood approach pseudo-experiments with respect to q =lnl MEM for the case t which hypothesis HD cα is rejected if hypothesis SM is realized, t choices of the likelihood function. 43

56 Phenomenology group at the Vrije Universiteit Brussel Since October 2010, to make a chain between the theoretical and experimental groups at the VUB. Englert, Frere, Hambye, Tinyakov, Tytgat, Argurio,... pheno Maltoni,... CMS Contact to CMS, IceCube, H1, OPERA,... [email protected], [email protected] Kentarou Mawatari (Vrije U. Brussel) 44 Aug. 26, 2013 SUSY2013@Trieste

57 High Energy Physics Research VUB The 5-year pheno project was rearranged into a larger framework in January 2013 Theory: Ben Craps, Alexander Sevrin (string/cosmology) Collider physics: Jorgen D Hondt, Freya Blekman, Steven Lowette (CMS) Astor-particle physics: Catherine De Clercq, Nick Van Eindhoven (IceCube) Phenomenology: Kentarou Mawatari Pheno members Kentarou Mawatari - Project leader since 2010 Laura Lopez Honorez - PD since 2012 Priscila de Aquino - PD since 2012 Bettina Oexl - PhD since 2010 Karen De Causmaecker - PhD since 2011 Pantelis Tziveloglou (from Ecole Polytechnique, CPHT) - PD since 2013 Jonathan Lindgren (from Chalmers U. of Tech) - PhD since 2013 Kentarou Mawatari (Vrije U. Brussel) 45 Aug. 26, 2013 SUSY2013@Trieste