Precision measurement of Triple Gauge Couplings at future e + e - PowerPoint PPT Presentation

Precision measurement of Triple Gauge Couplings at future e + e − colliders Linear Collider Workshop 2019 Jakob Beyer 1,2 , Jenny List 1 1 DESY Hamburg 2 Universität Hamburg Sendai, 30.10.2019

Charged Triple Gauge Couplings (TGCs) W + Z/γ → LEP: ∼ 10 − 2 − 10 − 1 precision − W − 4.5 Precision of Higgs boson couplings [%] Model Independent EFT Fit LCC Physics WG 4 Impact of improved TGC precisions ⊕ HL-LHC ILC250 3.5 × 1/3 ⊕ HL-LHC ILC250, TGCs from LEP 3 2.5 Relevance today: × [arXiv:1903.01629] 1/2 2 > Gauge boson BSM? 1.5 > Higgs coupling fit! 1 0.5 0 DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 2/17 τ Γ Γ γ γ µ Z W b g c Z inv h

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 � i f ( dim-6 ) i Λ 2 = ⇒ Effective Field Theory Here: High- M BSM O ( dim-6 ) i = ⇒ To measure: c i = f ( dim-6 ) 10-100 TeV ? i Λ 2 6 = [F. Simon] Page 3/17

TGCs in SM-EFT ⇒ To measure: c i = f ( dim-6 ) f ( dim-6 ) O ( dim-6 ) i � i L dim-6 = = i Λ 2 Λ 2 i � † B µν � � † τ a W a,µν � f B Ψ f W Ψ � � � � L TGC D L D L D L D L dim − 6 = ig 1 µ Ψ ν Ψ + ig 2 µ Ψ ν Ψ Λ 2 Λ 2 f W 6 Λ 2 W a,µ ǫ abc W b,ν ρ W c,ρ + g 2 ν µ m 2 g Z Z W + 1 =1 + f B Ψ Λ 2 κ γ =1 + ( f B Ψ + f W Ψ ) m 2 Z/γ W Λ 2 W − λ γ =3 m 2 W g 2 2 f W Λ 2 ⇒ Deviations: ∆ { g Z 1 , κ γ , λ γ } ∼ { c i · m 2 = W/Z } DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 4/17

Extracting TGCs e + W + e + W − Z/γ ν e W + e − e − W − Key process: WW production s-channel: TGCs { g Z 1 , κ γ , λ γ } � 2 � σ meas − σ pred ( TGCs ) Idea: Minimize χ 2 = � ∆ σ meas bins However: s- and t-channel highly chirality dependent ... DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 5/17

Beam polarisation For m ∼ 0 : = x % particles fixed helicity, (100 − x )% random helicity ˆ > 1 polarised beam − → 2 datasets: L enhanced / R enh. > 2 polarised beam − → 4 datasets: LR / RL / LL / RR enh. σ chirality dependent! ( SM: U (1) × SU (2) L × SU (3) ) q e + q ′ ¯ W R,L [R. Karl] W e − ν L,R l @ e + e − collider: high-precision σ LR/RL WW = ⇒ Beam polarisation measurement from WW pair production! DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 6/17

Combined measurement e + L,R W + > Triple Gauge Couplings > Beam polarisations W − e − L,R e + Other SM parameters? = ⇒ A e , ... Z e − Here generalized : 1 total cross-sec. σ tot process & 1 asymmetry A ij, process per process Extract { g Z 1 , κ γ , λ γ , beam polarisations , σ tot process , A ij, process } in parallel from measurement! DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 7/17

Combined fit setup � 2 � σ meas − σ pred ( parameters ) Minimize χ 2 = � ∆ σ meas processes , bins { g Z 1 , κ γ , λ γ , beam polarisations , σ tot process , A ij, process } Input: > “Collider”: Energy, luminosity, polarisations Output: > “Measurement”: σ meas ∀ processes, bins > Parameter uncertainties / sensitivities > Theory: σ pred ∀ processes, bins Theory: & parameter-dependence DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 8/17

Considered processes Fit parameters: { g Z 1 , κ γ , λ γ , beam polarisations , σ tot process , A ij, process } Collider parameters: energy, luminosity, polarisations Processes: q q q q ′ e + q ¯ e + ¯ e + q ′ ¯ W Z W W Z e ¯ ν e − e − l ∓ e − ν l ± l 2000 3D-Bins × 2( W ± ) 2000 3D-Bins 2000 3D-Bins q e + e + l ± q ¯ ¯ e − e − l ∓ 20 1D-Bins 20 1D-Bins DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 9/17

DISCLAIMER So far: > Only 250 GeV > Generator level > “Analysis”: ǫ = 60% , π = 80% ∀ bins, processes (motivated by WW full sim. study) Not considered: > ISR / Beam spectrum 4f: impact on angular distr. small 2f: 50% would be @ Z -pole → Here: all 250 GeV > Detector & full analysis (all channels) > Systematic Unc. ( ∆ ǫ, ∆ L, ... ) Except: Polarisation Theory uncert. (partially) as fit parameters DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 10/17

Lepton collider options Linear Circular Typical: L ∼ 2 ab − 1 , e − (& e + ) polarised Typical: L ∼ 10 ab − 1 , e − & e + unpolarised = ⇒ 6 scenarios : > Luminosity: 2 ab − 1 / 10 ab − 1 e − & e + : 45%( − + ) , 45%( + − ) , 5%( −− ) , 5%( ++ ) e − : > Polarised beams: 80%( − 0 ) , 20%( +0 ) None : 100%( 00 ) DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 11/17

Combined fit results 50 250 GeV e + e − ( P e − , P e + ) Fit EW + non-0 pol., (80%,30%) no syst. unc. 40 (80%,0%) (0%,0%) Uncertainty [10 − 4 ] 2 ab − 1 > g Z 1 , λ γ : 30 10 ab − 1 10 fb − 1 unpol. ≈ 2 fb − 1 pol. > κ γ : 20 10 fb − 1 unpol. ≪ 2 fb − 1 pol. 10 0 ∆ g Z ∆ ∆ λ γ γ 1 DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 12/17

∆ P / P ∼ 10 − 3 − 10 − 4 [Appendix] Combined fit results σ tot � process = σ ij, process A ij, process = ( σ ij − σ ji ) / ( σ ij + σ ji ) LR,RL,... (Definition process-dependent) 35 250 GeV e + e − ( P e − , P e + ) 250 GeV e + e − ( P e − , P e + ) 50 Fit EW + non-0 pol., Fit EW + non-0 pol., 30 (80%,30%) (80%,30%) no syst. unc. no syst. unc. (80%,0%) (80%,0%) (0%,0%) 40 (0%,0%) 25 Uncertainty [10 − 4 ] Uncertainty [10 − 4 ] 2 ab − 1 2 ab − 1 10 ab − 1 10 ab − 1 20 30 15 20 10 10 5 0 0 ∆ σ eνW + ( qq ) ∆ σ eνW − ( qq ) ∆ σ WW ( lνqq ) ∆ σ ZZ ( lνqq ) ∆ σ qq ∆ σ ll ∆ A eνW + ( qq ) ∆ A eνW − ( qq ) ∆ A WW ( lνqq ) ∆ A ZZ ( lνqq ) ∆ A qq ∆ A ll Overall similar sensitivities. However: 0-polarisations fixed! DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 13/17

If 0 � = 0? Reminder: Only fitting non-0 polarisations − → Less fit parameters = ⇒ Physical?? > Circular: Maybe... (Sokolov-Ternov) > Linear: Need to measure! 35 250 GeV e + e − 250 GeV e + e − 50 Fit EW + non-0 pol., Fit EW + non-0 pol., 30 no syst. unc. no syst. unc. 40 25 Uncertainty [10 − 4 ] ( P e − , P e + ) Uncertainty [10 − 4 ] ( P e − , P e + ) (80%,30%) (80%,30%) 20 (80%,0%) (80%,0%) 30 (0%,0%) (0%,0%) 15 P e + free, 2 ab − 1 P e + free, 2 ab − 1 2 ab − 1 20 2 ab − 1 10 ab − 1 10 ab − 1 10 10 5 0 0 ∆ σ eνW + ( qq ) ∆ σ eνW − ( qq ) ∆ σ WW ( lνqq ) ∆ σ ZZ ( lνqq ) ∆ σ qq ∆ σ ll ∆ A eνW + ( qq ) ∆ A eνW − ( qq ) ∆ A WW ( lνqq ) ∆ A ZZ ( lνqq ) ∆ A qq ∆ A ll = ⇒ If 0 = 0 not guaranteed, large uncertainties! DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 14/17

If 0 � = 0? 50 250 GeV e + e − ( P e − , P e + ) Fit EW + non-0 pol., (80%,30%) no syst. unc. 40 (80%,0%) (0%,0%) Uncertainty [10 − 4 ] P e + free, 2 ab − 1 > No significant effect 30 2 ab − 1 on TGCs 10 ab − 1 But: 20 Syst. unc. not considered! 10 0 ∆ g Z ∆ ∆ λ γ γ 1 DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 15/17