Constraining BSM physics in effective Higgs interactions

Transcription

1 Constraining BSM physics in effective Higgs interactions Theory Seminar Liverpool Alexander K Knochel RWTH Aachen In collaboration with the Fittino Group (Bonn) M.Krämer, B. Heller, A. Biekötter (Aachen) F.Riva (Lausanne)

2 Outline Introduction An effective Theory for BSM Higgs Physics Limitations of EFTs Kinematic distributions and Higgs searches Triple Gauge Couplings

3 Introduction

4 Higgs-like, all too Higgs-like... ATLAS-CONF Alternatives? ATLAS (arxiv: ) 97.8%CL against J P = 0, 1 +, 1, 2 + Spin 2: No reason for coupling strengths to be at all SM-Higgs-like... Spin 1: Landau-Yang

5 New Physics BSM Why do we expect new physics beyond the SM? Dark Matter Hierarchy problems of Higgs and Dark Energy Quantum Gravity A theory of flavor/neutrino masses, baryo/leptogenesis Unification? What is the scale of new physics? (*) (*) with sizable couplings to the SM

6 M NP TeV? The measured values of m t, m h are in a rather special range! Degrassi et al. This plot is mostly meaningless if there is Terascale BSM physics. Desert after all?

7 High scale Hints < See-Saw f DM a > λ = 0 g 1 = g 2 Is this a coincidence? There exists a class of stringy compactifications with intermediate scale SUSY and shift/exchange symmetries in the Higgs sector which fits this picture nicely. K H u + H d 2 λ(m s ) = 0 [A. Hebecker, AK, T. Weigand 12][A. Hebecker, AK, T. Weigand 13][Ibañez et al. 12] [Hall, Nomura 14] Higgs hierarchy problem is present, yet 20 o.o.m. milder than the worst case δv 2 6M 2 Pl /16π2.

8 M NP TeV? Substantial modifications to the SM near the EW scale nonstandard EWSB weak scale SUSY other models with new fields and particles in LHC range How to look for it: Dedicated searches for SUSY, ED, compositeness... or for simplified models Model independent searches (e.g. MuSiC) So far no luck... Use a complementary approach!

9 M NP TeV? Separation of scales M NP > M W, v: L = L SM + ci 5 Λ Oi 5 + ci 6 Λ 2Oi Hope: all possible new physics at M NP > M W reduces to a simple effective description with few parameters. Aim to interpret the existing Higgs searches in terms of a simple, useful + theoretically meaningful framework...

10 The Effective Theory description

11 Effective Theory Only one Dim-5 structure: HL α HL α Neutrino masses Dim-6: 100s s! Including all of them is hopeless, and fortunately not necessary! General flavor violating terms Λ TeV, thus not important for Higgs [D ambrogio et al, 02]: Adopt U(3) 5 MFV: ( L, E, Q, U, D) Also assume B, L conserved at this level [Arzt]: Can use EOM in effective theory to eliminate operators! e.g. ν B µν = ig Y H H D µ H + g f Y f f γ µ f + O( 1 Λ 2 ) 59 Operators remain! [Buchmüller, Wyler 86][Grzadkowski, Iskrzynski, Misiak, Rosiek 10] [Elias-Miro, Espinosa, Masso, Pomarol 13] Only a subset affect Higgs physics@lhc

12 The minimal set of 17 CP + operators for Higgs physics [Riva, Pomarol] 8 Operators affecting Higgs Physics and EW Precision Physics O W = ig 2 (H σ a D µ H)D ν W a µν O B = ig 2 Operators affecting Higgs Physics and TGCs 2 (H σ a D µ H) ν B µν O T = 1 2 (H D µh) 2 O f = (ih D µh)(f γ µ f ), f = Q, u, d, e O 3 ql = (ih σ a D µh)(q L σ a γ µ Q L ) O HW = ig(d µ H) σ a (D ν H)W a µν O HB = ig (D µ H) (D ν H)B µν 8 Operators affecting Higgs Physics only (assuming 3d gen.) O 6 = λ H 6 O H = 1 2 ( µ H 2 ) 2 O BB = g 2 H 2 B µνb µν O GG = g 2 s H 2 G A µν G Aµν O yu = y u H 2 Q L HuR O yd = y d H 2 Q L Hd R Q ye = y e H 2 L L He R

13 The minimal set of 17 CP + operators for Higgs physics [Riva, Pomarol] 8 Operators affecting Higgs Physics and EW Precision Physics O W = ig 2 (H σ a D µ H)D ν W a µν O B = ig 2 Operators affecting Higgs Physics and TGCs 2 (H σ a D µ H) ν B µν O T = 1 2 (H D µh) 2 O f = (ih D µh)(f γ µ f ), f = Q, u, d, e O 3 ql = (ih σ a D µh)(q L σ a γ µ Q L ) O HW = ig(d µ H) σ a (D ν H)W a µν O HB = ig (D µ H) (D ν H)B µν 8 Operators affecting Higgs Physics only (assuming 3d gen.) O 6 = λ H 6 O H = 1 2 ( µ H 2 ) 2 O BB = g 2 H 2 B µνb µν O GG = g 2 s H 2 G A µν G Aµν O yu = y u H 2 Q L HuR O yd = y d H 2 Q L Hd R Q ye = y e H 2 L L He R

14 The minimal set of 17 CP + operators for Higgs physics [Riva, Pomarol] 8 Operators affecting Higgs Physics and EW Precision Physics O W = ig 2 (H σ a D µ H)D ν W a µν O B = ig 2 Operators affecting Higgs Physics and TGCs 2 (H σ a D µ H) ν B µν O T = 1 2 (H D µh) 2 O f = (ih D µh)(f γ µ f ), f = Q, u, d, e O 3 ql = (ih σ a D µh)(q L σ a γ µ Q L ) O HW = ig(d µ H) σ a (D ν H)W a µν O HB = ig (D µ H) (D ν H)B µν 8 Operators affecting Higgs Physics only (assuming 3d gen.) O 6 = λ H 6 O H = 1 2 ( µ H 2 ) 2 O BB = g 2 H 2 B µνb µν O GG = g 2 s H 2 G A µν G Aµν O yu = y u H 2 Q L HuR O yd = y d H 2 Q L Hd R Q ye = y e H 2 L L He R

15 The minimal set of 17 CP + operators for Higgs physics [Riva, Pomarol] 7 Operators affecting Higgs Physics and EW Precision Physics O W + O B O T = 1 2 (H D µh) 2 O f = (ih D µh)(f γ µ f ), f = Q, u, d, e O 3 ql = (ih σ a D µh)(q L σ a γ µ Q L ) 3 Operators affecting Higgs Physics and TGCs O HW = ig(d µ H) σ a (D ν H)W a µν O HB = ig (D µ H) (D ν H)B µν O W O B? 8 Operators affecting Higgs Physics only (assuming 3d gen.) O 6 = λ H 6 O H = 1 2 ( µ H 2 ) 2 O BB = g 2 H 2 B µνb µν O GG = g 2 s H 2 G A µν G Aµν O yu = y u H 2 Q L Hu R O yd = y d H 2 Q L Hd R Q ye = y e H 2 L L He R

16 The minimal set of 17 CP + operators for Higgs physics [Riva, Pomarol] 7 Operators affecting Higgs Physics and EW Precision Physics O W + O B O T = 1 2 (H D µh) 2 O f = (ih D µh)(f γ µ f ), f = Q, u, d, e O 3 ql = (ih σ a D µh)(q L σ a γ µ Q L ) 2 Operators affecting Higgs Physics and TGCs O HW = ig(d µ H) σ a (D ν H)W a µν O HB = ig (D µ H) (D ν H)B µν 9 Operators affecting Higgs Physics only (assuming 3d gen.) O 6 = λ H 6 O H = 1 2 ( µ H 2 ) 2 O BB = g 2 H 2 B µνb µν O GG = g 2 s H 2 G A µν G Aµν O WW = O BB + 4O W 4O B 4O HW + 4O HB = g 2 H 2 W a µν W aµµ O yu = y u H 2 Q L Hu R O yd = y d H 2 Q L Hd R Q ye = y e H 2 L L He R

17 Our basis for LHC-Fits in Fittino etc. O 6 = λ H 6 Multi-Higgs only O H = 1 2 ( µ H 2 ) 2 global rescaling h h/z O GG = i H 2 GµνG a aµν O WW = ig H 2 WµνW a aµν O BB = ig H 2 B µν B µν O HW = ig(d µ H) σ a (D ν H)Wµν a O HB = ig (D µ H) (D ν H)B µν O yt = y t H 2 Q L HtR O yb = y b H 2 Q L Hb R O yτ = y τ H 2 L L Hτ R Also implemented in FeynRules(/MadGraph/Pythia/Delphes)

18 SM Higgs production at LHC [Baglio et al. 11]

19 SM Higgs decays m H = 125 GeV is a sweet spot for detection in many channels

20 Production channels and contributing operators + O GG, O yt + O WW, O HW, O BB,O HB + O WW, O HW, O BB,O HB + O yt

21 Decay channels and contributing operators + O GG, O yt + + O WW, O BB,O HW O }{{ HB, O } yt h γz only! + O yb + O WW, O HW, O BB,O HB

22 Results of [Eboli et al.] (f WW = f BB ) f g f HB f WW f H f BB f yb f HW f yτ Blue dashes: including 1-loop EWPT

23 Results of [Eboli et al.] (f WW = f BB ) f g f HB + f WW f H f BB f yb f HW f yτ Blue dashes: including 1-loop EWPT

24 Results of [Riva, Pomarol] c V mw 2 = f WW 2 κ + HV m 2 W = f HW 4 + f HB 4 κ HV m 2 W = f HW 8 f HB 8 + f WW 2 (Blue: set others to zero, green: theoretical priors)

25 Limitations of the Effective approach

26 The trouble with EFTs for LHC Effective theories come with an expiration scale... L = 1 Λ 2O What is the maximum range of validity of this Lagrangian? partial wave unitarity In the case of 2 2 scattering, T T J. 1 = S S = (1 + it J )(1 it J ) = 1 + i(t J T J ) + T J T J M J M J = i 32π MJ M J ReM J > 32π signals breakdown of perturbation theory Since for LHC physics we integrate up to ŝ = s, invalid regions can be reached in Higgs production.

27 The trouble with EFTs for LHC

28 The trouble with EFTs for LHC

29 What is M NP? The mass of new particles: Strongly interacting NP: MNP 4πΛ Weakly interacting NP: MNP Λ Loop induced: MNP Λ/4π... Λ Breakdown of perturbativity of EFT: O HW : M J=0 (WW ZZ) α2 π 2 6m 4 W s4 W v 2 C H W 2 s 2 Perturbative unitarity breakdown: ŝ < 1.3 TeV for C W prior How to cope with this in global fits?

30 Dealing with unitarity violation+breakdown of the EFT K-Matrix: TK J T J (1 + it J ) 1 TK J T J K = it K JT J K Exactly unitary 2 2 processes from LO results Gives you the maximum theoretically possible effect (apart from resonances) un-conservative exclusion. Difficult to implement for general processes, not necessarily correct

31 Dealing with unitarity violation+breakdown of the EFT Simpler [Dreiner, Duff, Zeppenfeld 92 How well do we know the ggg vertex ]: Introduce form factor to unitarize M f O O f O (s)o = f O (1 + s/b) n O FF mimics onset of new physics smallest n, largest b such that M tree remains below unitarity bound yields conservative allowed region for f O n : cutoff at unitarity bound, more conservative exclusion We study dependence of global fit on choices for b, n fully implemented into Fittino/HiggsSignals framework. Either unitarization scheme problematic (process dependent) combinations?

32 Acceptance Issues

33 Acceptance and Efficiency in the Effective Theory A ɛ: Which fraction of events passes identification criteria and kinematic cuts of the experimental searches? Published 95CL limits/intervals for signal strength µ σ/σ SM e.g. µ(pp HV, H bb) < ATLAS Simplest approach: calculate σ LO (f Oi )/σ LO ( 0) and start scanning... Assumptions: K factors remain the same: σlo (f Oi )/σ LO ( 0) σ SOA (f Oi )/σ SOA ( 0) Scale dependence of foi is negligible [ongoing project] A ɛ of searches remains the same In particular the last assumption is very wrong in some cases!

34 Acceptance in the Effective Theory Most extreme example: HZ, H bb, Z νν Change in acceptance is the dominant effect! How come?

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36 f HW f HB 0 f HW , f HB

37 2500 f 2000 HW f HB 0 Implementation intof HW Fittino/HiggsSignals 5, f HB MadGraph/Pythia/Delphes+Root analyses of relevant processes 5D Acceptance Grid with Neural Network interpolation

38 Triple Gauge Couplings

39 In the EFT, three operators can contribute to sizable deviations from SM-like TGCs: Compare O HW (D µ H) W µν (D ν H) v 2 V µ W µν V ν O HB (D µ H) B µν (D ν H) v 2 V µ B µν V ν O 3W ɛ abc Tr W a W b W c O WW H HW a µνw a µν v 2 W a µνw a µν Aim constrain anomalous TGCs via impact of O HW,O HB on Higgs production

40 TGC approach 1: Custodial symmetry in h decays Exploit energy difference in h WW and h ZZ decays Slide stolen from F. Riva Discrepancy with [Corbett et al ]

41 TGC approach 2: Angular distributions in h ffv [Isidori, Manohar, Trott 13][Riva, Pomarol 13] Slide stolen from F. Riva Unfortunately, remaining changes in distributions are rather small

42 TGC approach 3: p T distributions in pp VH [Biekötter, Krämer, AK, Riva, in preparation] TGC operators O HW,O HB exhibit more divergent UV behavior than O WW, O BB Fractionwith p T 300for pp W Hat 8TeV f HW 10 6 GeV f WW 10 6 GeV 2

43 TGC approach 3: p T distributions in pp VH Naive exclusion (no acceptance), f WW = f BB = f H = ATLAS CMS 2 Κv 10² c V V 10² Including acceptance changes should improve this picture!

44 TGC approach 3: p T distributions in pp VH Exclusion (with acceptance), f WW = f BB = f H = ATLAS CMS 2 Κv 10² c V V 10² Can we do even better? Clearly, high-p T bins are very sensitive

45 TGC approach 3: p T distributions in pp VH Using p T > 200 GeV data only, f WW = f BB = f H = 0, no BG error 6 4 ATLAS CMS 2 Κv 10² c V V 10² Might yield strongest indirect constraints on TGCs!

46 Conclusions If new physics M W, effective theories are a useful tool to study Higgs interactions Fittino, originally a SUSY parameter fitting package, has been adapted for Higgs physics EFT with Dim-6 operators is implemented, global Higgs fits are underway Higgs production@lhc can see the limitations of the EFT approach Form factors and acceptance corrections Constraints on anomalous TGCs from kinematic distributions Thank you for your attention!

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48 Do we need new to solve the hierarchy problem? SM+new high scale particle fine tuning problem! M 2 X ( 1 ɛ log µ2 /M 2 X +... ) In their absence: DREG or Cutoff? d d p m 2 t ( 1 ɛ log µ2 /m 2 t +... ) Λ Λ 2 [Bardeen 95]: if we don t violate scaling symmetry explicitly beyond β, may subtract Λ 2 to restore symmetry, or use DREG [Schmaltz et al. 13]: Embedding SM into truly scale invariant theory even w/o heavy particles generically reintroduces HP if Λ conformal TeV! We don t seem to get around NP@TeV to get rid of the HP