Composite Higgs and LHC phenomenology LianTao Wang University of Chicago Lattice for BSM 2016. Argonne, April 21. 2016
This talk - Composite Higgs models. Many of them. Will focus on generic feature, not details. - Will cover LHC phenomenology. - Beyond LHC (briefly).
Explaining EWSB: naturalness Λ : a cut-off. The energy scale of new physics responsible for EWSB Electroweak scale, 100 GeV. m h , m W …
Explaining EWSB: naturalness Λ : a cut-off. The energy scale of new physics responsible for EWSB What is Λ ? Can it be very high, such as M Planck = 10 19 GeV, …? So different from 100 GeV? Electroweak scale, 100 GeV. m h , m W …
Naturalness of electroweak symmetry breaking Λ : a cut-off. The energy scale of new physics responsible for EWSB What is Λ ? Can it be very high, such as M Planck = 10 19 GeV, …? So different from 100 GeV? TeV new physics. Naturalness motivated Electroweak scale, 100 GeV. m h , m W …
Example of naturalness in nature γ γ π ± π ± e 2 δ m 2 16 π 2 Λ 2 ≃ π ± - Example: low energy QCD resonances: pion .... - m 𝜌 ∼ 100 MeV . - Naturalness requires Λ ≈ GeV . Indeed, at GeV , QCD ⇒ theory of quark and gluon Pion is natural since it is not elementary.
“Learning” from QCD quark and gluon: q g GeV More composite resonaces K, η , ρ , ... π ± ... 100 MeV
“Learning” from QCD quark and gluon: q g ⇒ new strong dynamics, GeV More composite resonaces symmetry breaking K, η , ρ , ... ⇒ SM Higgs π ± ... 100 MeV - New strong dynamics in which the low lying states will be the SM Higgs. - Composite Higgs models, natural. - QCD scale is natural. Nature could just repeat itself for the weak scale.
Composite Higgs LHC New constituents? q � g � TeV More composite resonaces W � , Z � , ... ρ : m ρ ' g ρ f, ... g ρ � 1 W, Z, Higgs 100 GeV Many models in this class. - Similar scenarios: Randall-Sundrum... Agashe, Sundrum; Contino, Nomura, Pomarol
Composite Higgs EFT Georgi and Kaplan Higgs (and W/Z goldstones) are part of the strong sector The external fields are the SM quarks and (transverse) gauge bosons - Higgs boson (and W L Z L ) NGB of symmetry breaking G/H. - Small explicit symmetry breaking (involving external fields) generates Higgs potential. (NGB ➜ pNGB).
Minimal composite Agashe, Contino, Pomarol First prediction: deviation in Higgs coupling
Higgs coupling. s 1 � v 2 f 2 c SM c hV V = hV V - Higgs couplings. f > 500-600 GeV > v. Some fine tuning seems unavoidable.
EW precision. � �� � � � � � # � $ %& ' 1 ' Tree level S-parameter 0.5 & S ∼ 4 π v 2 0.2 m 2 0.1 ρ % � One loop to S and T 0.05 $ v 2 1 0.02 !"# f 2 log( m ρ /m h ) 16 π 2 0.01 0.005 Additional UV contribution parameterized by general CCWZ 0 2 4 6 8 10 m � ! TeV " Contino, Salvarezza, 2015 In addition, constraints from Z decay. Relevant for partially composite u L v 2 δ g u L = 1 f 2 s 2 L,u < 0 . 5 × 10 � 3 R h : 4
Problem of f > v ? - Higgs potential “wants” to have f ≈ v. - A little bit fine tuned. - One can invent something to deal with it (such as little Higgs, etc.). A lot of additional structure for a factor of 10-100? - Or, take the tuning as acceptable. (Will take the view here).
Composite Higgs LHC New constituents? q � g � TeV More composite resonaces W � , Z � , ... ρ : m ρ ' g ρ f, ... g ρ � 1 W, Z, Higgs 100 GeV
Composite Higgs LHC New constituents? q � g � TeV More composite resonaces W � , Z � , ... ρ : m ρ ' g ρ f, ... g ρ � 1 W, Z, Higgs 100 GeV Phenomenology of the resonances
Spin-1 resonances G/H = SO (5) /SO (4) Spin-1 resonance in 6 of SO(4) m ρ ∼ g ρ f SO (4) × U (1) X = SU (2) L × SU (2) R × U (1) X Y = T 3 R + X Under this, spin-1 res. decompose as 6 → 3 0 + 1 0 + 1 ± , ρ ± ρ L : ρ 0 , ρ ± ρ B C
ρ coupling to h, W L , Z L L ⊃ ig ρ c H ρ a µ ( H † τ a D µ H − ( D µ H ) † τ a H ) . W ± L , Z L , h ρ W ± L , Z L , h ∼ g ρ - h, W L Z L composite, large coupling to ρ .
Partial compositeness composite fermion with the same gauge quantum numbers as SM fermion. L pc = − m Ψ ¯ ΨΨ − y L f (¯ q L Ψ + h.c. ) − y R f (¯ u R Ψ + h.c. ) q L , u R , d R Ψ y f = m Ψ sin φ f L sin φ f R , f ∼ y y L,R sin � L,R ≡ q . ( m Ψ /f ) 2 + y 2 L,R - Mixing angles not completely fixed. - For example, for top quark, the mixing should be large, O(1). Top quark heavy because it is composite.
ρ coupling to SM fermion ⇢ ⇢ ⇢ + = ¯ ¯ ¯ ∼ g 2 /g ρ ∼ g ρ y 2 ρ mixes with W/Z ρ couples to composite mixing angle: g / g ρ fermion first, which mixes with SM fermion.
ρ coupling to SM fermion ⇢ ⇢ ⇢ + = ¯ ¯ ¯ ∼ g 2 /g ρ ∼ g ρ y 2 ¯ ¯ q L � µ q L u R � µ u R d R � µ d R ` L � µ ` L e R � µ e R V V , V h ¯ ¯ ¯ g 2 � g 2 � g 2 L,q ) ⌧ a ⌧ a g 2 s 2 ⇢ 0 , ± ρ g ρ (1 � a L – – – g ρ g ρ g 2 g 0 2 g 0 2 g 0 2 g 0 2 g 0 2 � 1 � 2 1 1 g 0 2 s 2 ⇢ 0 ρ g ρ (1 + 3 a L L,q ) B 6 g ρ 3 g ρ 3 g ρ 2 g ρ g ρ ⇢ ± g ρ – – – – – C
Decay of composite spin-1 res. 0.7 0.7 elementary fermions composite quarks H s L,t = 0.1, s L,q = 0.15 L composite top H s L,t = 0.5 L composite quarks H s L,t = 0.4, s L,q = 0.15 L 0.6 0.6 W + W - , Zh W + W - , Zh branching ratio branching ratio 0.5 0.5 0.4 0.4 jj jj 0.3 0.3 tt 0.2 0.2 tt { + { - { + { - 0.1 0.1 0 0 1 2 3 4 5 6 1 2 3 4 5 6 - BR to diboson is large. Suppressed fermion g r g r coupling. Could have large rate. c.f., usual gauge boson, small BR to diboson. - Suppressed fermion coupling ➜ suppress for example di-lepton mode. BR( ⇢ 0 ! ` + ` − ) g 4 BR( ⇢ 0 ! W + W − ) = 8 , c 2 g 4 H ρ
Excess around 2 TeV? -1 CMS, L = 19.7 fb , s = 8 TeV 4 10 Events / 100 GeV Data ATLAS Observed Background model -1 s = 8 TeV, 20.3 fb 3 1.5 TeV EGM W', c = 1 10 1 Expected (68%) WZ) (pb) 2.0 TeV EGM W', c = 1 2.5 TeV EGM W', c = 1 Expected (95%) Significance (stat) 2 10 Significance (stat + syst) W' WZ → WZ Selection -1 10 10 → B(W' 1 -2 10 − 1 10 × 1.5 2 2.5 3 3.5 σ Significance 3 2 -3 1 10 0 1 − 2 − 1 1.5 2 2.5 3 1.5 2 2.5 3 3.5 m [TeV] Resonance mass (TeV) jj Thamm, Torre, Wulzer Composite spin-1 vector? Bian, Liu, Shu Low, Tesi, LTW … Run 1 data, generated some excitement. Not confirmed by run 2 (so far).
Run 2 projection 1.0 Flavor 2 c H = 0.5 5 fb - 1 0.9 20 fb - 1 0 f b - 1 0.8 8 TeV preferred 13 TeV diboson 0.7 13 TeV dilepton 0.6 5 f b - 1 sin f Lt 0.5 0.4 0.3 0.2 0.1 Higgs 0 1 2 3 4 5 6 can give the excess g r - Can confirm or rule out with modest luminosity.
Reach of Run 2, di-boson and di-lepton 10 2 s = 13 TeV s = 13 TeV 10 2 10 1 c H = 0.5, s L,t = 0.4 c H = 0.5, s L,t = 0.4 s ¥ BR H W ± Z L H fb L s ¥ BR H { + { - L H fb L 1 20 fb - 1 20 fb - 1 10 1 10 - 1 100 fb - 1 100 fb - 1 10 - 2 1 10 - 3 g r = 2 g r = 2 10 - 4 10 - 1 g r = 4 g r = 4 10 - 5 g r = 6 g r = 6 10 - 2 10 - 6 2.0 2.5 3.0 3.5 4.0 2.0 2.5 3.0 3.5 4.0 m r H TeV L m r H TeV L - At most 4 TeV .
Additional channels 0.7 0.7 elementary fermions composite quarks H s L,t = 0.1, s L,q = 0.15 L composite top H s L,t = 0.5 L composite quarks H s L,t = 0.4, s L,q = 0.15 L 0.6 0.6 W + W - , Zh W + W - , Zh branching ratio branching ratio 0.5 0.5 0.4 0.4 jj jj 0.3 0.3 tt 0.2 0.2 tt { + { - { + { - 0.1 0.1 0 0 1 2 3 4 5 6 1 2 3 4 5 6 g r g r - If it is there, should be able to see it in Wh, Zh tt, tb
Top partner Integrating out top partner ➜ Higgs potential F a,b : function of h f m Ψ : mass of top partner Light Higgs ➜ light top partner Top partner colored. Can be produced efficiently at the LHC. Good prospect, and strong constraint. .
Compositeness and top partner 2.5 1 2/3 2.0 2 1/6 2 7/6 [ TeV ] 1.5 3 2/3 + 1 5/3 + 1 -1/3 mKK 1.0 0.5 prefers a light T’ 120 125 130 135 140 145 150 155 160 [ GeV ] Contino, Da Rold, Pomarol, 2006 mHiggs For a comprehensive discussion, see De Simone, Matsedonskyi, Rattazzi, Wulzer, 1211.5663 - Light top partner ( ψ which mixes with top ) could be less than TeV . - Plays a crucial role in EWSB.
LHC 14 should cover (most of) it.
ρ decaying into top partners top partners WW + Zh ` + ` − - BR( ρ ➜ ψψ ) O(1). Would dominate if allowed. - Diboson would not be the leading channel. - Can assume ψ heavy, more fine-tuning.
May show up somewhere else? 4 10 Events / 40 GeV ATLAS Preliminary Data 3 10 Background-only fit 2 -1 10 s = 13 TeV, 3.2 fb techni-quark, g’… 10 1 1 − 10 Data - fitted background 200 400 600 800 1000 1200 1400 1600 15 10 5 0 TeVs comp. resonances − 5 10 − 15 − 200 400 600 800 1000 1200 1400 1600 m [GeV] γ γ CMS -1 Preliminary 2.6 fb (13 TeV) Events / ( 20 GeV ) EBEB category η (750)? 2 10 10 h(125) Data 1 Fit model ± 1 σ -1 10 ± 2 σ stat 4 σ 2 (data-fit)/ 0 -2 -4 Mass 750 is fully natural here. 2 2 2 3 3 3 × 10 4 × 10 5 × 10 10 2 × 10 m (GeV) γ γ Model complicated, however.
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