Composite Higgs Overview

Transcription

1 Composite Higgs Overview Tony Gherghetta Fundamental Composite Dynamics, IBS CTPU, Daejeon, Korea, December 6, IBS Daejeon - 6 December 2017

2 Composite Higgs New strong force with coupling, g s g s s = M P e 8 2 g 2 s b s M P TeV s M P Higgs boson = bound state of new strong dynamics µ 2 h 2 s M 2 P (where V (h) = µ 2 h H 2 + h H 4 ) BUT why is Higgs boson much lighter than other bound states? 2 IBS Daejeon - 6 December 2017

3 Possible New Dynamics Higgs as dilaton topcolor Technicolor Randall- Sundrum Experiment Little Higgs Higgs as pngb Composite Twin Higgs 3 IBS Daejeon - 6 December 2017

4 Higgs = pseudo Nambu-Goldstone boson [Georgi, Kaplan `84] Global symmetry, G spontaneously broken to subgroup, H at scale, f (n) & TeV Resonance mass: m g f 1. g. 4 coset G/H h + W L,Z L Higgs doublet } e.g. SO(5)/SO(4) h Higgs mass protected by shift symmetry -- like pions in QCD! h! h + const. Strong dynamics does NOT break electroweak symmetry! BUT global symmetry must be explicitly broken to generate V (h) 6= 0 4 IBS Daejeon - 6 December 2017

5 Global symmetry broken by mixing with elementary sector [Contino, Nomura, Pomarol `03; Agashe, Contino, Pomarol `04] SM matter and gauge fields i,a µ L mix = L,R L,RO + g V A µ J µ strongly-coupled Higgs sector O i Higgs potential: V (h) = µ 2 h H 2 + h H 4 h h h h t L,R where µ 2 h g2 SM 16 2 g 2 f 2 h g2 SM 16 2 g 2 [g SM = SM gauge or Yukawa coupling] EWSB: v 2 = µ2 h hhi = v p2 f v h Higgs mass: m 2 h =2 h v 2 ' N c 2 m2 t g 2 T g T 1.3 i.e. light top partners (= fermionic resonances) m T g T f 5 IBS Daejeon - 6 December 2017

6 Bonus feature: Partial compositeness L = L L O R + R R O L Explains the fermion mass hierarchy [Kaplan 91; TG, Pomarol 00] where m f L R v L,R UV dim OL,R 5 2 L R Lx R x R L H Light fermions are mostly elementary dim O L.R > 5 2 Top quark is mostly composite! dim O L,R IBS Daejeon - 6 December 2017

7 A Natural Composite Higgs spectrum : 750 GeV. f. 1 TeV 10 TeV (n) (spin 2 resonances) (vector resonances) 1. g. 4 1 TeV (n) (top partners) g T GeV h (pseudo NG boson) Dark matter = pngb (enlarged coset) 7 IBS Daejeon - 6 December 2017

8 LHC Limits: Massive spin-1, spin-2 resonances (n) & 3 TeV h 8 IBS Daejeon - 6 December 2017

9 Deviations in gauge, Yukawa couplings g hw W g SM hw W g hff g SM hff s 1 v 2 f 2 v2 f IBS Daejeon - 6 December 2017

10 Top partners e.g. 5 2/3! 2 7/ / /3 T ATLAS-CONF m T & 1050 GeV 10 IBS Daejeon - 6 December 2017

11 } [Barnard, White ] ' g T f m T & 1050 GeV tuning v2 f 2. 5% 11 IBS Daejeon - 6 December 2017

12 Natural models provide complete picture BUT : UV completion? --- What are UV d.o.f that lead to global symmetry breaking pattern? --- Can partial compositeness be realised without elementary scalars? What about the tuning? --- Tuning worse if include flavor constraints --- How to eliminate electroweak and flavor constraints? 12 IBS Daejeon - 6 December 2017

13 1. UV completion Candidate: SO(6)/SO(5) SU(4)/Sp(4) [Other possibilities classified by Ferretti, Karateev ] Symmetry breaking-pattern f SU(4)! Sp(4) What is the dynamics that realizes this? SU(4) gauged NJL model [Barnard, TG, Sankar Ray ] Spontaneous breaking of global symmetry driven mainly by 4-fermion interaction! 13 IBS Daejeon - 6 December 2017

14 Partial compositeness: L = L t L O R + R t R O L UV description: O L,R $ } = tightly bound by 4-fermion interaction, bound to by Sp(2Nc) gauge interaction ( p ) dim O L,R =dim dim & 5 2 Marginally irrelevant! p } 3 m Allows for order-one top Yukawa coupling Top partners are naturally lighter than uncolored partners! Interesting UV completion for lattice studies 14 IBS Daejeon - 6 December 2017

15 2. Indirect Constraints EWPT: s 16 2 v 2 H a HB µ W aµ S = s 2 m2 W m 2 f & 2.5 TeV g t 16 2 v 2 ((Dµ H) H)(H D µ H) T = t 8 e 2 v2 f 2 f & 5.5 TeV e.g. FCNC i q j q k q l q g 2 m 2 q i q j q k q l i q g i g f & 10 TeV [Bellazzini, Csaki, Serra ] [Panico, Wulzer ] f v Little hierarchy Tension partly alleviated by complicating minimal models e.g. custodial symmetry, flavor, symmetry, twin parity. 15 IBS Daejeon - 6 December 2017

16 Embrace Unnaturalness! Assume f & 10 TeV -- no need for custodial or flavor symmetries! Tuned Higgs potential: V c 2 f 2 H 2 + c 4 H 4 tuning v2 f Compares to in SM! Is there a motivated upper bound for f? Yes! 16 IBS Daejeon - 6 December 2017

17 Gauge coupling unification Assume composite t R and coset (t R, c ) = complete H multiplet } G/H [Agashe, Contino, Sundrum 05] Decoupled with top companions Dirac mass: m f New contribution to the running of SM gauge couplings top companions contribution } composite Higgs, top GAUGE COUPLING UNIFICATION B strong 9b strong C 3 b strong b strong =1, 5 Requires: f. 500 TeV 17 IBS Daejeon - 6 December 2017

18 Minimal Coset: SU(7)/SU(6)xU(1) [James Barnard, TG, Tirtha Sankar Ray, Andrew Spray: ] contains SU(5) --universal corrections to running scalar singlet dark matter [Frigerio, Pomarol, Riva, Urbano ] 12 Nambu-Goldstone bosons = 5 of SU(5) + 1 singlet } = S } H = Higgs doublet, D + SU(3) triplet, T 18 IBS Daejeon - 6 December 2017

19 Dark matter stability Enlarge global group: NG bosons Nonzero baryon triality leads to stability! SM fermions top companions 19 IBS Daejeon - 6 December 2017

20 The Unnatural or Split Composite Higgs model [James Barnard, TG, Tirtha Sankar Ray, Andrew Spray: ] color triplet top companions DM Low-energy spectrum: Standard Model + S + T + } What are experimental signals? 20 IBS Daejeon - 6 December 2017

21 Dark matter: singlet Higgs partner S -- Higgs portal coupling V apple D 2 S 2 [New limit from ] where 840 GeV. m S. 10 TeV 21 IBS Daejeon - 6 December 2017

22 Collider searches: top companions f = 10 TeV future 100 TeV collider color-triplet Higgs partner T (like RH sbottom in SUSY) f = 10 TeV dimension-6 term f > 10 TeV = long-lived decay T! tbss } can produce a displaced vertex! 22 IBS Daejeon - 6 December 2017

23 Color triplet decay [James Barnard, TG, Tirtha Sankar Ray, Andrew Spray: ] natural composite Higgs: f. 1 TeV Unnatural or split composite Higgs: 10 TeV. f. 500 TeV 23 IBS Daejeon - 6 December 2017

24 LHC: [Barnard, Cox, TG, Spray: ] 24 IBS Daejeon - 6 December 2017

25 MATHUSLA: (MAssive Timing Hodoscope for Ultra Stable neutral particles) [see for example Curtin, Peskin: ] Projected Sensitivity [Cox, TG, Spray: in preparation] Complements LHC searches 25 IBS Daejeon - 6 December 2017

26 Summary --- Higgs = pseudo Nambu-Goldstone boson --- Explains electroweak and fermion mass hierarchy Natural composite Higgs --- Natural models tuned. 5% --- Expect light top partners, vector resonances, Higgs coupling deviations Unnatural or split composite Higgs --- f & 10 TeV eliminates electroweak and flavour constraints --- Higgs potential, meso-tuned at 10 4 level --- Long-lived color-triplet decay = sign of unnaturalness! More natural More unnatural 1 TeV 10 TeV f 26 IBS Daejeon - 6 December 2017

27 Future Directions Other signs of unnaturalness? long-lived neutral top companions or neutral pngbs? Other unnatural possibilities? larger cosets UV completion? reason for tuning? composite twin Higgs e.g. SU(6) SU(6)/SU(6) [contains neutral color octet] Alternate ways to deal with tuning? [e.g ] relaxation of composite little hierarchy [e.g ] 27 IBS Daejeon - 6 December 2017