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

1DESY Hamburg 2Universität Hamburg

Sendai, 30.10.2019

Charged Triple Gauge Couplings (TGCs)

Z/γ W + W −

− → LEP: ∼ 10−2 − 10−1 precision Relevance today: > Gauge boson BSM? > Higgs coupling fit!

0.5 1 1.5 2 2.5 3 3.5 4 4.5

Precision of Higgs boson couplings [%]

Z W b τ g c

inv

Γ

h

Γ γ γ Z

1/3 ×

µ

1/2 ×

Impact of improved TGC precisions ILC250 ⊕ HL-LHC ILC250, TGCs from LEP ⊕ HL-LHC

Model Independent EFT Fit LCC Physics WG

[arXiv:1903.01629]

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Effective Field Theory (EFT)

ard Model Precision Tests

• 1)

?

10-100 TeV

6=

For many generic models & new interactions: 


[F. Simon]

Here: High-M BSM = ⇒ Effective Field Theory Ldim-6 =

• i

f(dim-6)

i

Λ2 O(dim-6)

i

= ⇒ To measure: ci = f (dim-6)

i

Λ2

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 3/17

TGCs in SM-EFT

Ldim-6 =

• i

f(dim-6)

i

Λ2 O(dim-6)

i

= ⇒ To measure: ci = f (dim-6)

i

Λ2 LTGC

dim−6 = ig1

fBΨ Λ2

• DL

µΨ

† Bµν

DL

ν Ψ

• + ig2

fW Ψ Λ2

• DL

µΨ

† τ aW a,µν

DL

ν Ψ

• + g2

fW 6Λ2 W a,µ

ν

ǫabcW b,ν

ρ W c,ρ µ

Z/γ W + W −

gZ

1 =1 + fBΨ

m2

Z

Λ2 κγ =1 + (fBΨ + fW Ψ) m2

W

Λ2 λγ =3m2

W g2 2

Λ2 fW = ⇒ Deviations: ∆{gZ

1 , κγ, λγ} ∼ {ci · m2 W/Z}

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Extracting TGCs

e− e+ W + W − Z/γ e− e+ W − W + νe Key process: WW production s-channel: TGCs {gZ

1 , κγ, λγ}

Idea: Minimize χ2 =

• bins

σmeas − σpred(TGCs)

∆σmeas

2

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:

ˆ = x% particles fixed helicity, (100 − x)% random helicity > 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) )

e−

L,R

e+

R,L

q ¯ q′ l ν W W [R. Karl]

@ e+e− collider: high-precision σLR/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

e+

L,R

W + W −

> Triple Gauge Couplings > Beam polarisations Other SM parameters? e− e+ Z = ⇒ Ae, ... Here generalized: 1 total cross-sec. σtot

process & 1 asymmetry Aij,process per process

Extract {gZ

1 , κγ, λγ, beam polarisations, σtot process, Aij,process}

in parallel from measurement!

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 7/17

Combined fit setup

Minimize χ2 =

• processes,bins

σmeas − σpred(parameters)

∆σmeas

2

{gZ

1 , κγ, λγ, beam polarisations, σtot process, Aij,process}

Input: > “Collider”: Energy, luminosity, polarisations > “Measurement”: σmeas ∀processes, bins > Theory: σpred ∀processes, bins Theory: & parameter-dependence Output: > Parameter uncertainties / sensitivities

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Considered processes

Fit parameters: {gZ

1 , κγ, λγ, beam polarisations, σtot process, Aij,process}

Collider parameters: energy, luminosity, polarisations Processes:

e− e+ e ν q ¯ q′ W

2000 3D-Bins ×2(W ±)

e− e+ q ¯ q′ l ν W W

2000 3D-Bins

e− e+ q ¯ q l± ¯ l∓ Z Z

2000 3D-Bins

e− e+ q ¯ q

20 1D-Bins

e− e+ l± ¯ l∓

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 Typical: L ∼ 2 ab−1, e− (& e+) polarised Circular Typical: L ∼ 10 ab−1, e− & e+ unpolarised = ⇒ 6 scenarios: > Luminosity: 2 ab−1 / 10 ab−1 > Polarised beams: e−&e+ : 45%(−+), 45%(+−), 5%(−−), 5%(++) e− : 80%(−0), 20%(+0) None : 100%(00)

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Combined fit results

∆gZ

1

∆

γ

∆λγ 10 20 30 40 50 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. (Pe−, Pe+)

(80%,30%) (80%,0%) (0%,0%) 2ab−1 10ab−1

> gZ

1 , λγ:

10 fb−1 unpol. ≈ 2 fb−1 pol. > κγ: 10 fb−1 unpol. ≪ 2 fb−1 pol.

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 12/17

Combined fit results

∆P/P ∼ 10−3 − 10−4 [Appendix] σtot

process =

• LR,RL,...

σij,process Aij,process = (σij − σji) / (σij + σji) (Definition process-dependent)

∆σeνW + (qq) ∆σeνW − (qq) ∆σWW(lνqq) ∆σZZ(lνqq) ∆σqq ∆σll 5 10 15 20 25 30 35 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. (Pe−, Pe+)

(80%,30%) (80%,0%) (0%,0%) 2ab−1 10ab−1

∆AeνW + (qq) ∆AeνW − (qq) ∆AWW(lνqq) ∆AZZ(lνqq) ∆Aqq ∆All 10 20 30 40 50 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. (Pe−, Pe+)

(80%,30%) (80%,0%) (0%,0%) 2ab−1 10ab−1

Overall similar sensitivities. However: 0-polarisations fixed!

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If 0 = 0?

Reminder: Only fitting non-0 polarisations − → Less fit parameters = ⇒ Physical?? > Circular: Maybe... (Sokolov-Ternov) > Linear: Need to measure!

∆σeνW + (qq) ∆σeνW − (qq) ∆σWW(lνqq) ∆σZZ(lνqq) ∆σqq ∆σll 5 10 15 20 25 30 35 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. (Pe−, Pe+)

(80%,30%) (80%,0%) (0%,0%) Pe+ free, 2ab−1 2ab−1 10ab−1

∆AeνW + (qq) ∆AeνW − (qq) ∆AWW(lνqq) ∆AZZ(lνqq) ∆Aqq ∆All 10 20 30 40 50 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. (Pe−, Pe+)

(80%,30%) (80%,0%) (0%,0%) Pe+ free, 2ab−1 2ab−1 10ab−1

= ⇒ If 0 = 0 not guaranteed, large uncertainties!

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 14/17

If 0 = 0?

∆gZ

1

∆

γ

∆λγ 10 20 30 40 50 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. (Pe−, Pe+)

(80%,30%) (80%,0%) (0%,0%) Pe+ free, 2ab−1 2ab−1 10ab−1

> No significant effect

• n TGCs

But:

• Syst. unc. not considered!

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 15/17

Adding systematics...

Ongoing study

(schematic)

> No polarisation: Deviations ambiguous > 2 (4) correlated polarisation settings: ǫ effect in all, TGC effect enhanced in 1 (2)

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 16/17

TGCs & the future of HEP

∆gZ

1

∆

γ

∆λγ 10 20 30 40 50 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. (Pe−, Pe+)

(80%,30%) (80%,0%) (0%,0%) Pe+ free, 2ab−1 2ab−1 10ab−1

> Studied here: TGCs + EW cross sections / theory unc. + polarisations > Significant improvement with beam polarisation (w/o detector effects, ...!)

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page 17/17

BACKUP

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page I/VIII

Combined fit: polarisation

P−

e−

P+

e−

P−

e+

P+

e+

P0

e+

2 4 6 8 10 12 Uncertainty [10−4] 250GeV e+e− Fit EW + non-0 pol., no syst. unc. x1/10 (Pe−, Pe+)

(80%,30%) (80%,0%) Pe+ free, 2ab−1 2ab−1 10ab−1

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page II/VIII

W W → µνqq gZ

1 -dependence [R. Karl]

)

• W

θ cos( 0.5 − 0.5

LR

σ /

LR

σ δ

2 −

10

1 −

10 SM 0.1 + g 0.1 − g )

• W

θ cos( 0.5 − 0.5

RL

σ /

RL

σ δ

2 −

10

1 −

10 SM 0.1 + g 0.1 − g

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page III/VIII

W W → µνqq check cross section vs. full MC check [R. Karl]

Comparing matrix element differential distributions with MC distributions (incl. ISR & Beamstrahlung):

)

W-

θ cos( 0.5 − 0.5

LR

σ /

LR

σ δ

2 −

10

1 −

10 )

W-

θ cos( 0.5 − 0.5

RL

σ /

RL

σ δ 0.04 0.05 0.06

DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page IV/VIII

Polarimeter effect on polarisation [R. Karl]

within the scope of this study. Without Constraint With Constraint E[GeV] 500 350 250 500 250 500 350 250 500 250 L[1/fb] 500 200 500 3500 1500 500 200 500 3500 1500 ∆P −

e−/P

2.1 3.3 1.7 0.8 0.95 1.2 1.3 1.1 0.69 0.79 ∆P +

e−/P

0.45 0.83 0.45 0.17 0.26 0.44 0.78 0.44 0.17 0.26 ∆P −

e+/P

2 3.2 1.5 0.75 0.87 1.5 2 1.3 0.71 0.81 ∆P +

e+/P

3.6 5.4 2.6 1.3 1.5 1.9 2 1.7 1.1 1.2

Table 8.4: The final precision of the polarization

• 10−3

after each run of the H-20 scenario as shown in fig. 8.11. The red colored values exceed the 0.25% polarimeter precision, while the blue colored values can improve the precision to be better than the polarimeter precision due to the soft constraint.

For a more detailed comparison, the final precisions for each run of the H-20 scenario

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Polarimeter induced bias [R. Karl]

What if polarimeter measures P off by 1σ?

qq ν e →

+

W σ pull 4 − 2 − 2 4 50 100 150 200

= 30%

e

P Mean: -0.41 Sigma: 0.98 = 0%

e

P Mean: -0.91 Sigma: 0.96

qq ν e →

• W

σ pull 4 − 2 − 2 4 50 100 150 200

= 30%

e

P Mean: -0.39 Sigma: 1 = 0%

e

P Mean: -0.91 Sigma: 0.99 DESYª | Precision TGCs | Jakob Beyer | Sendai, 30.10.2019 Page VI/VIII

Single parameter fit sensitivity comparison [arXiv:1903.01629]

TGC Limits @ 68% CL 0.05 − 0.05 0.1

γ

λ ∆

γ

κ ∆

1 Z

g ∆ LEP2 ATLAS CMS HL-LHC ILC 250

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Contact

DESYª Deutsches

Jakob Beyer Elektronen-Synchrotron FLC Physics Group jakob.beyer@desy.de www.desy.de +49–40–8998–1638

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