Constraints on Nonstandard Top Quark Couplings from Precision - - PowerPoint PPT Presentation

▶
constraints on nonstandard top quark couplings
SMART_READER_LITE
LIVE PREVIEW

Constraints on Nonstandard Top Quark Couplings from Precision - - PowerPoint PPT Presentation

Aug 02, 2023 321 likes •574 views

Nonstandard Couplings Oblique Parameters A Global Fit Summary Constraints on Nonstandard Top Quark Couplings from Precision Electroweak Data Cen Zhang Department of Physics University of Illinois at Urbana-Champaign 10 May / Pheno 2011

slide-1
SLIDE 1

Nonstandard Couplings Oblique Parameters A Global Fit Summary

Constraints on Nonstandard Top Quark Couplings

from Precision Electroweak Data Cen Zhang

Department of Physics University of Illinois at Urbana-Champaign

10 May / Pheno 2011

arXiv:1104.3122, Nicolas Greiner, Scott Willenbrock, Cen Zhang

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-2
SLIDE 2

Nonstandard Couplings Oblique Parameters A Global Fit Summary Effective Theory and Operators Constraint on OtW

Constraints on Nonstandard Top Quark Couplings

Nonstandard top quark couplings can be constrained:

Directly from colliders (cross sections, branching ratios, etc):

Degrande, Gerard, Grojean, Maltoni, Servant, 11 Aguilar-Saavedra, Carvalho, Castro, Onofre, Veloso, 07 Cao, Wudka, Yuan, 07

From B physics (B meson decay, B ¯ B mixing):

Grzadkowski,Misiak, 08 Drobnak, Fajfer, Kamenik, 11

Indirectly from Precision Electroweak Data (Z-pole, W-mass, DIS, LEP2, etc.)

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-3
SLIDE 3

Nonstandard Couplings Oblique Parameters A Global Fit Summary Effective Theory and Operators Constraint on OtW

History of Top Quark Mass

Quigg Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-4
SLIDE 4

Nonstandard Couplings Oblique Parameters A Global Fit Summary Effective Theory and Operators Constraint on OtW

Effective Theory Approach

Effective Field Theory

Leff = LSM + 1 Λ2 CiOi + h.c.

  • The Operators:

O(3)

φq = i(φ†τ IDµφ)(¯

qγµτ Iq), O(1)

φq = i(φ†Dµφ)(¯

qγµq), Oφt = i(φ†Dµφ)(¯ tγµt), Oφb = i(φ†Dµφ)(¯ bγµb), Oφφ = i(˜ φ†Dµφ)(¯ tγµb), OtW = (¯ qσµντ It)˜ φW I

µν,

ObW = (¯ qσµντ Ib)φW I

µν,

OtB = (¯ qσµνt)˜ φBµν, ObB = (¯ qσµνb)φBµν.

Couplings can be computed from Ci:

VL = C(3)

φq

v 2 Λ2 , VR = Cφφ v 2 2Λ2 , · · · , (Aguilar-Saavedra, 08)

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-5
SLIDE 5

Nonstandard Couplings Oblique Parameters A Global Fit Summary Effective Theory and Operators Constraint on OtW

Effective Theory Approach

Effective Field Theory

Leff = LSM + 1 Λ2 CiOi + h.c.

  • The Operators:

O(3)

φq = i(φ†τ IDµφ)(¯

qγµτ Iq), O(1)

φq = i(φ†Dµφ)(¯

qγµq), Oφt = i(φ†Dµφ)(¯ tγµt), Oφb = i(φ†Dµφ)(¯ bγµb), Oφφ = i(˜ φ†Dµφ)(¯ tγµb), OtW = (¯ qσµντ It)˜ φW I

µν ,

ObW = (¯ qσµντ Ib)φW I

µν,

OtB = (¯ qσµνt)˜ φBµν, ObB = (¯ qσµνb)φBµν.

Couplings can be computed from Ci:

VL = C(3)

φq

v 2 Λ2 , VR = Cφφ v 2 2Λ2 , · · · , (Aguilar-Saavedra, 08)

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-6
SLIDE 6

Nonstandard Couplings Oblique Parameters A Global Fit Summary Effective Theory and Operators Constraint on OtW

Constraint from Direct Measurement

Constraint on OtW, from the decay of the top quark to W boson of a given helicity:

CtW Λ2 = 1.1 ± 2.1 TeV−2 (CDF), CtW Λ2 = −0.8 ± 1.2 TeV−2 (D0).

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-7
SLIDE 7

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

Loop Corrections to W, Z, γ

ΠWW(q2) ΠZZ,γγ,γZ(q2)

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-8
SLIDE 8

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

The S Parameter

In d dimension,

αS = Nc CtW 2π2 √ 2mW mt Λ2 5 3 s2

W

   1 ǫ − γ + ln 4π − ln m2

t

µ2 − 2

  • 4m2

t − m2 Z

mZ arctan mZ

  • 4m2

t − m2 Z

+ 2    . Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-9
SLIDE 9

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

The S Parameter

In d dimension,

αS = Nc CtW 2π2 √ 2mW mt Λ2 5 3 s2

W

   1 ǫ − γ + ln 4π − ln m2

t

µ2 − 2

  • 4m2

t − m2 Z

mZ arctan mZ

  • 4m2

t − m2 Z

+ 2    .

At tree level, need to include OWB = (φ†τ Iφ)W I

µνBµν,

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-10
SLIDE 10

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

The S Parameter

In d dimension,

αS = Nc CtW 2π2 √ 2mW mt Λ2 5 3 s2

W

   1 ǫ − γ + ln 4π − ln m2

t

µ2 − 2

  • 4m2

t − m2 Z

mZ arctan mZ

  • 4m2

t − m2 Z

+ 2    .

At tree level, need to include OWB = (φ†τ Iφ)W I

µνBµν,

In the MS scheme,

αS = 4 CWB(µ)v2 Λ2 sW cW + Nc CtW 2π2 √ 2mW mt Λ2 5 3 s2

W

  − ln m2

t

µ2 − 2

  • 4m2

t − m2 Z

mZ arctan mZ

  • 4m2

t − m2 Z

+ 2   

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-11
SLIDE 11

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

The T Parameter

T = 0

At tree level, need O(3)

φ

= (φ†Dµφ)[(Dµφ)†φ]. T = −C(3)

φ

v2 Λ2

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-12
SLIDE 12

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

The U Parameter

U is finite, because there is no available counterterm at dimension-six.

U = Nc CtW π2 √ 2mW mt Λ2 s2

W

   m2

t

m2

W

+

  • m2

t

m2

W

− 1 2 ln

  • 1 −

m2

W

m2

t

  • − 2
  • 4m2

t − m2 Z

mZ arctan mZ

  • 4m2

t − m2 Z

   .

From PDG, U = 0.06 ± 0.10, for mt = 173 GeV and mh = 117 GeV, so

CtW Λ2 = −0.7 ± 1.1 TeV−2.

CtW Λ2 =

  • 1.10 ± 2.06 TeV−2

(from CDF), −0.79 ± 1.19 TeV−2 (from D0).

  • Note that we have negleted other dim-6 operators that

contribute at tree level, except for OWB and O(3)

φ .

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-13
SLIDE 13

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

The U Parameter

U is finite, because there is no available counterterm at dimension-six.

U = Nc CtW π2 √ 2mW mt Λ2 s2

W

   m2

t

m2

W

+

  • m2

t

m2

W

− 1 2 ln

  • 1 −

m2

W

m2

t

  • − 2
  • 4m2

t − m2 Z

mZ arctan mZ

  • 4m2

t − m2 Z

   .

From PDG, U = 0.06 ± 0.10, for mt = 173 GeV and mh = 117 GeV, so

CtW Λ2 = −0.7 ± 1.1 TeV−2.

CtW Λ2 =

  • 1.10 ± 2.06 TeV−2

(from CDF), −0.79 ± 1.19 TeV−2 (from D0).

  • Note that we have negleted other dim-6 operators that

contribute at tree level, except for OWB and O(3)

φ .

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-14
SLIDE 14

Nonstandard Couplings Oblique Parameters A Global Fit Summary S T U

The U Parameter

U is finite, because there is no available counterterm at dimension-six.

U = Nc CtW π2 √ 2mW mt Λ2 s2

W

   m2

t

m2

W

+

  • m2

t

m2

W

− 1 2 ln

  • 1 −

m2

W

m2

t

  • − 2
  • 4m2

t − m2 Z

mZ arctan mZ

  • 4m2

t − m2 Z

   .

From PDG, U = 0.06 ± 0.10, for mt = 173 GeV and mh = 117 GeV, so

CtW Λ2 = −0.7 ± 1.1 TeV−2.

CtW Λ2 =

  • 1.10 ± 2.06 TeV−2

(from CDF), −0.79 ± 1.19 TeV−2 (from D0).

  • Note that we have negleted other dim-6 operators that

contribute at tree level, except for OWB and O(3)

φ .

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-15
SLIDE 15

Nonstandard Couplings Oblique Parameters A Global Fit Summary Operators and Measurements Results

More operators and data...

Operators O(3)

φq = i(φ†τIDµφ)(¯

qγµτIq), O(1)

φq = i(φ†Dµφ)(¯

qγµq), Oφt = i(φ†Dµφ)(¯ tγµt), Oφb = i(φ†Dµφ)(¯ bγµb), OtW = (¯ qσµντIt) ˜ φW I

µν,

ObW = (¯ qσµντIb)φW I

µν,

OtB = (¯ qσµνt) ˜ φBµν, ObB = (¯ qσµνb)φBµν. Data Notation Measurement Z-pole ΓZ Total Z width σhad Hadronic cross section Rf (f = e, µ, τ, b, c) Ratios of decay rates A0,f

FB (f = e, µ, τ, b, c, s)

Forward-backward asymmetries ¯ s2

l

Hadronic charge asymmetry Af (f = e, µ, τ, b, c, s) Polarized asymmetries Fermion pair σf (f = q, µ, τ) Total cross sections for e+e− → f¯ f production at LEP2 Af

FB(f = µ, τ)

Forward-backward asymmetries for e+e− → f¯ f DIS QW (Cs) Weak charge in Cs and QW (Tl) Weak charge in Tl atomic parity violation QW (e) Weak charge of the electron g2

L, g2 R

νµ-nucleon scattering from NuTeV gνe

V , gνe A

ν-e scattering from CHARM II W mass mW W mass from LEP and Tevatron Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-16
SLIDE 16

Nonstandard Couplings Oblique Parameters A Global Fit Summary Operators and Measurements Results

More operators and data...

Operators O(3)

φq = i(φ†τIDµφ)(¯

qγµτIq), O(1)

φq = i(φ†Dµφ)(¯

qγµq), Oφt = i(φ†Dµφ)(¯ tγµt), Oφb = i(φ†Dµφ)(¯ bγµb), OtW = (¯ qσµντIt) ˜ φW I

µν,

ObW = (¯ qσµντIb)φW I

µν,

OtB = (¯ qσµνt) ˜ φBµν, ObB = (¯ qσµνb)φBµν. Data Notation Measurement Z-pole ΓZ Total Z width σhad Hadronic cross section Rf (f = e, µ, τ, b, c) Ratios of decay rates A0,f

FB (f = e, µ, τ, b, c, s)

Forward-backward asymmetries ¯ s2

l

Hadronic charge asymmetry Af (f = e, µ, τ, b, c, s) Polarized asymmetries Fermion pair σf (f = q, µ, τ) Total cross sections for e+e− → f¯ f production at LEP2 Af

FB(f = µ, τ)

Forward-backward asymmetries for e+e− → f¯ f DIS QW (Cs) Weak charge in Cs and QW (Tl) Weak charge in Tl atomic parity violation QW (e) Weak charge of the electron g2

L, g2 R

νµ-nucleon scattering from NuTeV gνe

V , gνe A

ν-e scattering from CHARM II W mass mW W mass from LEP and Tevatron Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-17
SLIDE 17

Nonstandard Couplings Oblique Parameters A Global Fit Summary Operators and Measurements Results

Global Fit

One sigma bounds on 8 operators:            −0.702 −0.701 −0.000 +0.128 −0.004 +0.000 −0.000 −0.000 −0.093 −0.087 −0.002 −0.992 −0.018 +0.001 −0.000 −0.000 −0.250 +0.258 −0.238 +0.017 −0.895 +0.071 −0.082 −0.041 −0.402 +0.400 −0.672 −0.004 +0.422 −0.051 −0.216 +0.005 −0.129 +0.129 −0.123 +0.001 −0.007 −0.210 +0.905 +0.297 +0.046 −0.045 +0.046 +0.001 −0.097 −0.916 −0.280 +0.259 −0.006 +0.006 +0.056 +0.000 −0.007 +0.329 −0.219 +0.917 +0.506 −0.506 −0.686 −0.000 −0.108 +0.028 +0.042 +0.048            × (TeV)2 Λ2              C(3)

φq

C(1)

φq

Cφt Cφb CtW CbW CtB CbB              =            −0.0131 ±0.0142 +0.595 ±0.268 +0.359 ±1.21 −3.13 ±2.12 −8.48 ±10.8 −58.1 ±27.8 −32.5 ±118 −3200 ±1290           

  • from tree level Zb¯

b couplings                from loop level effects Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-18
SLIDE 18

Nonstandard Couplings Oblique Parameters A Global Fit Summary

Summary

We obtain bound on OtW from a loop level calculation of U parameter. We perform a global analysis using all major precision electroweak measurements, and put constraints on 8

  • perators that involve nonstandard top quark interaction.

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-19
SLIDE 19

Nonstandard Couplings Oblique Parameters A Global Fit Summary

Thank you..

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-20
SLIDE 20

Nonstandard Couplings Oblique Parameters A Global Fit Summary

Dim-6 Operators We Have Neglected

Os

ll

= 1 2 (¯ lγµl)(¯ lγµl), Ot

ll =

1 2 (¯ lγµσal)(¯ lγµσal), Os

lq

= (¯ lγµl)(¯ qγµq), Ot

lq = (¯

lγµσal)(¯ qγµσaq), Ole = (¯ lγµl)(¯ eγµe), Oqe = (¯ qγµq)(¯ eγµe), Olu = (¯ lγµl)(¯ uγµu), Old = (¯ lγµl)(¯ dγµd), Oee = 1 2 (¯ eγµe)(¯ eγµe), Oeu = (¯ eγµe)(¯ uγµu), Oed = (¯ eγµe)(¯ dγµd), Os

hl

= i(h+Dµh)(¯ lγµl) + h.c., Ot

hl = i(h+σaDµh)(¯

lγµσal) + h.c., Os

hq

= i(h+Dµh)(¯ qγµq) + h.c., Ot

hq = i(h+σaDµh)(¯

qγµσaq) + h.c., Ohu = i(h+Dµh)(¯ uγµu) + h.c., Ohd = i(h+σaDµh)(¯ dγµσad) + h.c., Ohe = i(h+Dµh)(¯ eγµe) + h.c., OW = ǫabcW aν

µ W bλ ν

W cµ

λ

  • Z. Han and W. Skiba, Phys. Rev. D 71, 075009 (2005)

Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-21
SLIDE 21

Nonstandard Couplings Oblique Parameters A Global Fit Summary

A Weaker Assumption..

Assume an oblique new physics in general. Include:

OWB = (φ†τIφ)W I

µνBµν ,

O(3)

φ

= (φ†Dµφ)[(Dµφ)†φ] , ODB = 1

2 (∂ρBµν)(∂ρBµν) ,

ODW = 1 2 (DρW I

µν)(DρW Iµν) .

Tree level:

ˆ S = CWB cW sW v2 Λ2 , ˆ T = −C(3)

φ

v2 2Λ2 , W = −2CDW m2

W

Λ2 , Y = −2CDB m2

W

Λ2 .

Loop level:

ˆ U = Nc gCtW 4π2 √ 2vmt 4Λ2 , V = −Nc gCtW 4π2 √ 2vmt Λ2 m2

W

12m2

t

, X = Nc gCtW 4π2 √ 2vmt Λ2 5m2

Z

72m2

t

sW cW . ⇒ CtW Λ2 = −3.6 ± 1.6 TeV−2. Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-22
SLIDE 22

Nonstandard Couplings Oblique Parameters A Global Fit Summary

Parametrization

Vertex function

LWtb = − g √ 2 ¯ bγµ[(1 + VL)PL + VRPR]tW −

µ

− g √ 2 ¯ b iσµνqν mW (gLPL + gRPR)tW −

µ + h.c.

LZtt = − g 2cW ¯ tγµ[(1 + XL)PL + XRPR − 4 3s2

W]tZµ

− g 2cW ¯ t iσµνqν mZ (dZ

V + idZ A γ5)tZ − µ

Lγtt = −2 3e¯ tγµtAµ − e¯ t iσµνqν mt (dγ

V + idγ A γ5)tAµ Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings

slide-23
SLIDE 23

Nonstandard Couplings Oblique Parameters A Global Fit Summary

Comparison with Constraints from Direct Measurement and B Physics

Bounds on individual operator (only one operator is turned on at a time), assuming Λ = 1 TeV.

Operators EW direct b → sγ B¯ B mixing O(3)

φq + O(1) φq

+0.009 ± 0.010 O(3)

φq − O(1) φq

+1.5 ± 1.7 −2.0 ± 1.2 −0.8 ± 1.3 −0.0 ± 1.3 Oφt +3.1 ± 2.7 Oφb −0.17 ± 0.10 Oφφ +0.03 ± 0.05 OtW −0.7 ± 1.1 −0.1 ± 1.2 +2.4 ± 4.2 −0.1 ± 1.6 ObW +22 ± 13 −0.006 ± 0.011 OtB +4.1 ± 6.7 ObB −23 ± 22 Nicolas Greiner, Scott Willenbrock, Cen Zhang Constraints on Nonstandard Top Quark Couplings