Theory perspective on future electroweak measurements A. Freitas - PowerPoint PPT Presentation

Theory perspective on future electroweak measurements A. Freitas University of Pittsburgh Lepton-Photon 2017 1. Electroweak precision observables 2. Electroweak showers 3. X-plosion

Electroweak precision observables: Going after large masses with one weak boson

Weak scale observables 1/19 Indirect sensitivity to top , Higgs , and W b f H new physics through quantum corrections Z t Z b f W W -boson mass M W (from τ µ ) Z -boson width Γ Z LEP EWWG ’05 σ had [ nb ] σ 0 Z -pole cross-section 40 σ 0 [ e + e − → ( Z ) → f ¯ f ] ALEPH DELPHI L3 30 OPAL Effective weak mixing angle sin 2 θ f eff from Z asymmetries ( A LR , A f Γ Z FB ) 20 g eff measurements (error bars 1 � � increased by factor 10) sin 2 θ f R eff = 2 | Q f | Re 10 σ from fit g eff R − g eff QED corrected L M Z 86 88 90 92 94 E cm [ GeV ]

Current uncertainties 2/19 Most important quantities: Exp. error Th. error M W 15 MeV 4 MeV Γ Z 2 . 3 MeV 0 . 5 MeV had = σ [ e + e − → Z → had. ] σ 0 37 pb 6 pb 6 . 6 × 10 − 4 1 . 5 × 10 − 4 R b = Γ[ Z → b ¯ b ] / Γ[ Z → had. ] sin 2 θ ℓ 1 . 6 × 10 − 4 0 . 5 × 10 − 4 eff (from A LR and A FB ) Complete NNLO or fermionic NNLO corrections known Freitas, Hollik, Walter, Weiglein ’00; Awramik, Czakon ’02; Onishchenko, Veretin ’02 Awramik, Czakon, Freitas, Weiglein ’04; Awramik, Czakon, Freitas ’06 Hollik, Meier, Uccirati ’05,07; Freitas ’13,14; Dubovyk, Freitas, Gluza, Riemann, Usovitsch ’16 Partial 3/4-loop corrections Chetyrkin, K¨ uhn, Steinhauser ’95 Faisst, K¨ uhn, Seidensticker, Veretin ’03 Boughezal, Tausk, v. d. Bij ’05; Schr¨ oder, Steinhauser ’05 Chetyrkin et al. ’06; Boughezal, Czakon ’06

Constraints on new physics in effective theory framework 3/19 c i Λ 2 O i + O (Λ − 3 ) L = � (Λ ≫ M Z ) Assuming flavor universality: i O φ 1 = ( D µ Φ) † Φ Φ † ( D µ Φ) O BW = Φ † B µν W µν Φ O (3) e = (¯ L e L σ a γ µ L e L )(¯ L e L σ a γ µ L e L ) LL ↔ O f D µ Φ)( ¯ R = i (Φ † f R γ µ f R ) ↔ O F L = i (Φ † D µ Φ)( ¯ F L γ µ F L ) ↔ O (3) F µ Φ)( ¯ = i (Φ † D a F L σ a γ µ F L ) L Pomaral, Riva ’13 Ellis, Sanz, You ’14

Low-energy electroweak observables 4/19 Polarized ee, ep, ed scattering e e ( Q W ( e ) , Q W ( p ) , eDIS) ν/ ¯ ν ν/ ¯ ν E158 ’05 ; Qweak ’13 ; JLab Hall A ’13 Z νN/ ¯ νN scattering NuTeV ’02 e, p, N e, p, N Atomic parity violation ( Q W ( 133 Cs ) ) Wood et al. ’97 g ef eγ µ γ 5 e ] [ ¯ AV [¯ fγ µ f ] Gu´ ena, Lintz, Bouchiat ’05 g ef eγ µ e ] [ ¯ VA [¯ fγ µ γ 5 f ] g ef 2 − 2 | Q f | sin 2 ¯ AV = 1 θ ( µ ) → Test of running MS weak mixing 2 − 2sin 2 ¯ g ef VA = 1 angle sin 2 ¯ θ ( µ ) θ ( µ )

Low-energy electroweak observables 5/19 Erler ’14 Polarized ee, ep, ed scattering 0.245 ( Q W ( e ) , Q W ( p ) , eDIS) SM published planned E158 ’05 ; Qweak ’13 ; JLab Hall A ’13 NuTeV antiscreening Q W (e) Q W (p) 0.240 SLAC JLab 2 θ W ( µ ) νN/ ¯ νN scattering s NuTeV ’02 c Q W (Cs) r e eDIS e 0.235 sin n i JLab n g Atomic parity violation LEP 1 Tevatron SLD Q W (p) 0.230 ( Q W ( 133 Cs ) ) LHC Wood et al. ’97 Mainz Q W (Ra) Q W (e) SoLID Gu´ ena, Lintz, Bouchiat ’05 KVI JLab JLab 0.225 0.001 0.01 0.1 1 10 100 1000 10000 µ [GeV] JE 201 14 → Test of running MS weak mixing angle sin 2 ¯ θ ( µ )

Low-energy electroweak observables 5/19 Erler ’14 Polarized ee, ep, ed scattering 0.245 ( Q W ( e ) , Q W ( p ) , eDIS) SM published planned E158 ’05 ; Qweak ’13 ; JLab Hall A ’13 NuTeV antiscreening Q W (e) Q W (p) 0.240 SLAC JLab 2 θ W ( µ ) νN/ ¯ νN scattering s NuTeV ’02 c Q W (Cs) r e eDIS e 0.235 sin n i JLab n g Atomic parity violation LEP 1 Tevatron SLD Q W (p) 0.230 ( Q W ( 133 Cs ) ) LHC Wood et al. ’97 Mainz Q W (Ra) Q W (e) SoLID Gu´ ena, Lintz, Bouchiat ’05 KVI JLab JLab 0.225 0.001 0.01 0.1 1 10 100 1000 10000 µ [GeV] JE 201 14 Future experiments: MOLLER ( ee ), P2, SoLID ( ep ), Atomic PV in radium

Future high-energy e + e − colliders 6/19 International Linear Collider (ILC) Int. lumi at √ s ∼ M Z : 50–100 fb − 1 Circular Electron-Positron Collider (CEPC) Int. lumi at √ s ∼ M Z : 2 × 150 fb − 1 Future Circular Collider (FCC-ee) Int. lumi at √ s ∼ M Z : > 2 × 30 ab − 1

Future projections 7/19 Measurement error Intrinsic theory Future † Current ILC CEPC FCC-ee Current M W [MeV] 15 3–4 3 1 4 1 Γ Z [MeV] 2.3 0.8 0.5 0.1 0.5 0.2 R b [ 10 − 5 ] 66 14 17 6 15 7 sin 2 θ ℓ eff [ 10 − 5 ] 16 1 2.3 0.6 4.5 1.5 → Existing theoretical calculations adequate for LEP/SLC/LHC, but not ILC/CEPC/FCC-ee! † Theory scenario: O ( αα 2 s ) , O ( N f α 2 α s ) , O ( N 2 f α 2 α s ) ( N n f = at least n closed fermion loops)

Future projections 8/19 Measurement Intrinsic theory Parametric ILC FCC-ee Current Future ILC FCC-ee M W [MeV] 3–4 1 4 1 2.6 0.6–1 Γ Z [MeV] 0.8 0.1 0.5 0.2 0.5 0.1 R b [ 10 − 5 ] < 1 < 1 14 6 15 7 sin 2 θ ℓ eff [ 10 − 5 ] 1 2.3 4.5 1.5 2 1–2 Projected parameter measurements: δ (∆ α ) δm t δα s δM Z 5 × 10 − 5 ILC: 50 MeV 0.001 2 . 1 MeV 3– 5 × 10 − 5 FCC-ee: 50 MeV 0.0002 0 . 1 MeV

Sensitivity to new physics 9/19 Heavy new physics: Light new physics: sterile neutrinos Antusch, Gazzato, Fischer ’16 (one op. at a time) de Blas et al. ’16 Drewes, Garbrecht, Gueter, Klaric ’16

Probes of EWPO with high-mass DY @ 100 TeV 10/19 Farina et al. ’16 J. Ruderman, FCC physics wshop ’17 M. Mangano, FCC week ’17

Electroweak showers: Large scales obscured by many weak bosons

Electroweak showers: massless 11/19 EW physics at future pp collider: W/Z bosons can be copiously produced at multi-TeV pp collider Enhancement ∼ log 2 ( E/M W ) for near-collinear emission Approximate description through parton shower Ciafaloni, Ciafaloni, Comelli ’00 Ciafaloni, Comelli ’05; Bell, K¨ uhn, Rittinger ’10 Christensen, Sj¨ ostrand ’14; Krauss, Petrov, Schoenherr, Spannowsky ’14 Bauer, Ferland ’16; Chen, Han, Tweedie ’16 Presence of scalar fields (Higgs/longitudinal gauge bosons): Chen, Han, Tweedie ’16

Electroweak showers: massive 12/19 Effect of masses / EWSB: k 2 T → k 2 zm 2 B + zm 2 zm 2 • Kinematics: • T + ¯ C − z ¯ A • Helicity-flipping (“ultra-collinear”) • splitting functions • Complication from gauge artifacts ∝ E/M W • → Remove with convenient gauge choice L gf = − 1 � n µ W µ ( k ) �� n ν W ν ( − k ) � ( ξ → ∞ ) 2 ξ n µ = (1 , − ˆ k ) → Smoothly interpolates to Goldstone equivalence of unbroken gauge at high energies Chen, Han, Tweedie ’16

Electroweak showers: massive 12/19 Effect of masses / EWSB: k 2 T → k 2 zm 2 B + zm 2 zm 2 • Kinematics: • T + ¯ C − z ¯ A ± → • Helicity-flipping (“ultra-collinear”) • dP(f W f ’) L L vs k (z=0.2) T dz dk splitting functions T 0.002 per GeV • Complication from gauge artifacts ∝ E/M W • 0.0015 W (massless) → Remove with convenient gauge choice T L gf = − 1 � n µ W µ ( k ) �� n ν W ν ( − k ) � ( ξ → ∞ ) W T 0.001 2 ξ n µ = (1 , − ˆ k ) 0.0005 → Smoothly interpolates to Goldstone equivalence W L of unbroken gauge at high energies 0 0 100 200 300 400 500 k (GeV) T

Electroweak showers: mixing and PDFs 13/19 Electroweak PDFs: γ/Z T and h/Z L mixing: � dz ′ dP q → V q ( ′ ) Sudakov evolution with density matrix � dk 2 f q ( z/z ′ ) f V ( z ) ≈ T dz ′ dk 2 z ′ T fraction of events (per 50 GeV) Kane, Repko, Rolnick ’84; Dawson ’85 - γ → µ µ - + + /Z e e + R L L R -3 10 s (TeV) 2 4 6 8 10 12 7 10 100 TeV q q 5 10 coherent 3 10 W τ ± ± γ dL/d γ q qW -4 T 10 10 T ± - + W W qW B 0 /W 0 incoherent − 1 T T 10 L − γ /Z incoherent 3 10 - + W W − L L 5 200 400 600 800 1000 1200 1400 10 0.05 0.1 M(f f ) (GeV) τ = s/S Chen, Han, Tweedie ’16

Electroweak showers: phenomenology 14/19 Decay of W ′ with m W ′ = 20 TeV into heavy quarks: with EW shower: with EW+QCD shower: fraction of events (per 200 GeV) fraction of events (per 200 GeV) 1 1 → → 20 TeV W’ t b , with EW FSR 20 TeV W’ t b , with EW+QCD FSR -1 -1 10 10 t b +X t b +X -2 -2 10 10 b b +X b b +X -3 -3 10 10 t t +X t t +X b t +X -4 -4 10 10 b t +X 0 2 4 6 8 10 12 14 16 18 20 22 0 2 4 6 8 10 12 14 16 18 20 22 M(Q Q ) (TeV) M(Q Q ) (TeV) Chen, Han, Tweedie ’16

X-plosion: Strength in numbers

Weak amplitudes at high energies 15/19 Higgs-plosion: φ ∗ → nφ in φ 4 theory: number of diagrams grows factorially √ � ( n − 1) / 2 � λ 3 λ � � A n = n ! 1 + n ( n − 1) Result at threshold: 2 m 2 8 π Voloshin ’92; Argyres, Kleiss, Papadopoulos ’92; Brown ’92; Smith ’92 n ! eventually overcomes λ n/ 2 yielding large cross-section Libanov, Rubakov, Son, Troitsky ’94; Son ’95 Khoze ’15