Electroweak PhysicsJens Erler

IF－UNAM

Summer Institute 2008August 10−17, 2008, Chi-Tou 溪頭, Taiwan 台灣

Thanks!To the organizers to have us discuss our favorite

physics topics in such a beautiful setting. Especially to

Francesca Borzumati

Ting-Wai Chiu

Otto Kong

Chia-chi Liu

Mr. Chen

for their help and support to get me here!

Outline

Introduction.

Electroweak Precision Measurements at Colliders.

Global Analysis.

Tevatron Run IIB, the LHC and the ILC.

Low Energy Measurements.

Conclusions.

Introduction

Not Covered: the Construction of the SM Lagrangian

... because you have probably seen it;

... because I would have to rush through it;

... because there are many excellent textbooks providing any degree of detail;

... because it is 2008, so any electroweak lecture will need to take some time to talk about the LHC;

... and because I would end up giving lectures on Quantum Field Theory.

The Standard Model (SM): History

✓ Lorentz invariance, quantum mechanics, the cluster decomposition principle, and 1⁄r²-forces for helicity ±1 particles ⇒ gauge invariance (Weinberg, 1965).

✓ “A model of leptons” (Weinberg, 1967).

✓ Renormalizability of non-Abelian gauge theories (‘t Hooft, Veltman; Lee, Zinn-Justin, 1972).

✓ Discovery of asymptotic freedom (Gross, Wilczek; Politzer, 1973).

✓ Discovery of the weak neutral current (CERN, 1973).

SM History (contd.)

✓ P in polarized e⁻-d DIS (Prescott et al., 1978).

✓ Discovery of W and Z bosons (UA1 & UA2, 1983).

➡ SM correct at least to first approximation.

Need high precision experiments to establish the SM as a renormalizable QFT at level of quantum effects.

g²⁄4π² ≈ 0.01 ⇒ need better than 1% accuracies.

✓ Z factories LEP 1 and SLC (1989).

➡ SM firmly established and new physics beyond it can only be a small perturbation.

SM Parameters

Spin 1 sector (gauge couplings): g, g′, g₃; or 4π αˢ= g₃² together with P and CP violating θ-angle; 4π α = gg′∕(g²+g′²) and sin²θᵂ = g′²∕(g²+g′²), where Z = cosθᵂ W³ − sinθᵂ B, A = sinθᵂ W³ + cosθᵂ B.

Spin ½ sector (Yukawa couplings): 9 fermion masses, 3 Cabibbo-Kobayashi-Maskawa (CKM) mixing angles, 1 CP violating CKM phase; 3 mixing angles, 1 Dirac phase, 2 Majorana phases in Maki, Nakagawa, Sakata (MNS) matrix (dimension 5 term or right-handed ν).

Spin 0 sector (Higgs potential): μ and λ or Mᴴ = √−2μ², v = Mᴴ∕λ.

Mass Determinations

Z boson mass and width from LEP 1.

W boson mass and width from LEP 2 and Tevatron.

Top quark mass from Tevatron and (before) global fit.

Charm and bottom quark masses from QCD sum rules.

Light quark mass scale from lattice gauge theory.

Light quark mass ratios from χPT.

Higgs boson mass from global fit and (later) LHC.

Electroweak Precision Measurements at Colliders

Master Equations

∆rZ = ∆rW + (1−∆rW )ΠZZ(M2

Z)− ΠW W (M2W )

cos2 θW

M2Z

A =[

πα√2GF

]1/2

sin2 θW (MZ) cos2 θW (MZ) =A2

M2Z(1−∆rZ)

sin2 θW (MZ) ≡ s2 =A2

M2W (1−∆rW )

,

∆rW =α

π∆γ +

ΠWW (M2W )− ΠWW (0)M2

W

+ V + B

∆rW ≡ 1− πα√2GF M2

W sin2 θW

∼ α

4π sin2 θW

lnM2

t

M2W

+ ∆α(MZ)

cos θW ≡ MW

MZ

MZ =√

g2 +g′2

2v

MW =g2

v

MH = λv

v = [√

2GF]−1/2 = 246.2209(5) GeV

Mt = ytv

VH =−M4H

8λ2 +M2H

H2

2+3λMH

H3

3!+3λ2H4

4!

(FAST, μLan)

∆ρ ≡ cos2 θW

cos2 θW

− 1 ∼ 3α

16π sin2 θW

M2t

M2W

∆κ! ≡ sin2 θeff.!

sin2 θW

− 1 ∼ 0.00125

Heavy Weights

Electroweak Loop Corrections

✓ 1-loop: Veltman (1977); Marciano, Sirlin (1980).

✓ 2-loop : Barbieri et al. (1993), analytical: Fleischer, Tarasov, Jegerlehner (1993).

✓ : Degrassi, Gambino, Vicini (1996).

✓ complete 2-loop contribution: Freitas, Hollik, Walter, Weiglein; Awramik, Czakon; Onishchenko, Veretin; Meier, Uccirati (2000-2007).

✓ : van der Bij et al. (‘01), Faisst et al. (‘03)

✓ : Boughezal, Tausk, van der Bij (2005).

O(M2t /M2

Z)

O(M4t /M4

Z)

O(α3M6t )

O(α3M4H)

Mixed QCD-Electroweak Loops

✓ : Djouadi, Verzegnassi (1987).

✓ : Chetyrkin, Kühn, Steinhauser (1995); Avdeev, Fleischer, Mikhailov, Tarasov (1994-1995).

✓ : Kniehl, Kühn, Stuart (1988); Halzen, Kniehl, Sirlin (1991/92); Djouadi, Gambino (1994).

✓ : Chetyrkin, Kühn, Steinhauser (1995);singlet: Anselm, Dombey, Leader (1993).

✓ : Chetyrkin et al.; Boughezal, Czakon (2006); singlet: Schröder, Steinhauser (2005).

✓ : van der Bij, et al. (2001).

O(ααsM2t )

O(αα2sM

2t )

O(ααs)

O(αα2s)

O(α2αsM4t )

O(αα3s)

Z⁰ Pole Physics

Z⁰ lineshape at LEP (3)

Leptonic BRs and FB asymmetries at LEP (6)

Leptonic LR and LR-FB asymmetries at SLC (4)

Tau polarization at LEP (2)

Charge asymmetries (2)

Strange quarks (3)

Heavy flavor BR and asymmetries (6)

Z⁰ lineshape

Z⁰ Pole and W Width Formulæ

A0FB(f) ≡ σF − σB

σF + σB=

34AeAf

Af ≡ 2vfaf

v2f + a2

f

vf = t3Lf − 2Qf sin2 θW

af = t3Lf

sin2 θW ≈ 0.23 ∼ 1/4

Γ(Z → ψfψf ) =CGF M3

Z

6√

2π(v2

f + a2f )

Γ(W+ → e+νe) =GF M3

W

6√

2π

Γ(W+ → uidj) =CGF M3

W

6√

2π|Vij |2

A0LR,FB(f) ≡ σf

LF − σfLB − σf

RF + σfRB

σfLF + σf

LB + σfRF + σf

RB

=34Af

A0LR ≡

σL − σR

σL + σR= Ae

Invisible Z-Width

LEP 1 indirectly: Γ(inv.) = Γ(Z) − Γ(had.) − Γ(l⁺l⁻) = 499.0 ± 1.5 MeV.

LEP 1 directly: Γ(inv.) = 503 ± 16 MeV (Eᵀ+ single γ).

Tevatron directly: Γ(inv.) = 466 ± 42 MeV (Eᵀ+ 1 jet).

SM: Γ(inv.) = 501.59 ± 0.08 MeV ⇒

Nᵥ = 2.985 ± 0.009 and Nᵥ = 3.01 ± 0.10 (LEP), Nᵥ = 2.79 ± 0.25 (Tevatron). (Update below!)

LEP

17 million Z⁰ decays including Z⁰ pole energy scan

⇒

vᵉ ∝ 1−4 sin²θᵂ ≈ 0.075 ≪ 1 ⇒ sensitivity increase

MZ = 91.1876±0.0021 GeVΓZ = 2.4952 ± 0.0023 GeVσhad = 41.541 ± 0.037 nb

αs(MZ) = 0.1213±0.0030

Nν = 2.985±0.007

sin2 θW

ve

∂ve

∂ sin2 θW≈ 12.3

Γinv = ΓZ − Γhad − Γl ⇒ΓZ ,σhad, R!(" = e, µ, τ)⇒

SLC

600,000 Z⁰ bosons with a 75% polarized e⁻ beam.

Polarimetry: O(1%) → correlation of syst. errors.

Aᴸᴿ linear in vᵉ → Aᴸᴿ larger → better statistics.

No need to tag quark flavor or distinguish quark from antiquark (only counting of hadrons/leptons) → clean.

LEP and SLC: sin²θᵂ = 023124 ± 0.00017.

Quark and lepton couplings to Z⁰ boson verified to better than 1% accuracy.

But non-standard amplitudes would hide under Z⁰.

LEP and SLC Heavy Flavor Results

value error SM pullRb 0.21629 0.00066 0.21580 +0.7Rc 0.1721 0.0030 0.1722 0Ab

FB 0.0992 0.0016 0.1033 −2.6Ac

FB 0.0707 0.0035 0.0738 −0.9Ab 0.923 0.020 0.9347 −0.6Ac 0.670 0.027 0.6679 +0.1

LEP 2: Rb : 2.1σ low,AbFB : 1.6σ high

The Weak Isospin of the Bottom Quark

⇒ top quark exists

155 160 165 170 175 180 185

mt [GeV]

80.30

80.35

80.40

80.45

MW

[G

eV

]

M H =

117 G

eV

M H =

200 G

eV

M H =

300 G

eV

M H =

500 G

eV

direct (1!!

indirect (1!!

all data (90%)

W charge asymmetry, Z rapidity distribution → PDFs.

W and Z production cross-sections + PDFs → luminosity meters and detector calibrators.

l⁺l⁻ invariant mass peak → Z’ boson (5-6 TeV; 1 ab⁻¹).Leptonic FB-asymmetries → Z’ diagnostics.

High νl transverse mass peak → W’ discovery.

➡ Need high precision predictions for single gauge boson production.

Electroweak Physics at Hadron Colliders

W and Z Boson Production: Milestones

✓ NNLO QCD fully differential cross-sections.

✓ Leading log soft gluon re-summation for pᵀ(W).

✓ O(α) EW corrections ⇒ ΔΓ(W) ≈ 7 MeV; to resonant production: ΔM(W) ≈ 10 MeV.

✓ O(α) final state γ radiation ⇒ ΔM(W) ≈ −65 ± 20 (−168 ± 20) MeV for e (μ).

✓ Multiple final state QED ⇒ ΔM(W) ≈ 2 (10) MeV.

✓ ∃ a number of MC event generators.

W and Z Boson Production: Open Issues

- O(ααˢ) mixed EW and QCD corrections.

- Higher-order EW Sudakov-like logarithms.

- Non-perturbative QCD contributions.

- Small x effects.

- Heavy quark mass effects.

- Grand Unification of MC programs.

➡ Top-electroweak group at the TeV4LHC workshop; Doreen Wackeroth, hep-ph/0610058 (HCP 2006).

Global Analysis

General Considerations

Should one average deviating data, or make choices what to keep (→ central limit bias)?

Should errors be estimated realistically or conservatively (→ overweight aggressive errors)?

Add errors linearly as a means to be conservative?

Replace theory input by experimental data whenever possible? Distinction always clear?

Central limit theorem for theoretical and syst. errors.

Take investor’s approach: diversification!

Global Fit

all data indirect onlyMH[GeV ] 92 +29 −24 117 (fixed)Mt[GeV ] 172.6 ± 1.5 175.4 ± 3.0αs(MZ) 0.1185 ± 0.0016 0.1185 ± 0.0016χ2/d.o.f. 48.8 / 43 (25%) 48.9 / 43 (25%)

SM Parameters: Fit Results

parameter central value uncertainty1/α(MZ) 127.920 ± 0.018

sin2 θW(MZ) 0.23119 ± 0.00013αs(MZ) 0.1185 ± 0.0017MW 80.379 GeV ± 15 MeVMZ 91.1874 GeV ± 2.1 MeVMH 92 GeV +29 −24 GeV

mc(mc) 1.264 GeV +35 −44 MeVmb(mb) 4.197 GeV ± 25 MeV

Mt 172.6 GeV ± 1.5 GeVtop quark mass: pre-ICHEP

σ(e⁺e⁻ → hadrons)

RGE running of EM coupling

RGE running of weak mixing angle

g-2

QCD sum rules for heavy quark masses

compare with HPQCD and UKQCD: 0.1170 ± 0.0012 from ϒ spectroscopy on the lattice (unquenched).

Strong Coupling: PDG 2008 + Update

αs(MZ)[ττ ] = 0.1225+0.0025−0.0022

αs(MZ)[all] = 0.1217± 0.0017

αs(MZ)[all other] = 0.1205± 0.0027

update 07/2008: αs(MZ)[ττ ] = 0.1176+0.0019−0.0017

αs(MZ)[new preliminary average] = 0.1185+0.0017−0.0015

Why Does αˢ from τ Decays Stand out?

Incredibly shrinking error.

OPE can be applied.

Fully inclusive.

Double zero near branch cut.

Non-perturbative effects constrained from data.

4-loop perturbative QCD available (non-singlet).

⇒ NNNLO accuracy.

Strong Coupling from τ Decays: 2008 Developments

Baikov, Chetyrkin, Kühn, hep-ph:0801.1821: non-singlet NNNLO-QCD corrections to τ and Z-decays; 0.1202 ± 0.0019 (FOPT + CIPT; d₄ = 0 ± 275).

Davier et al., hep-ph:0803.0979: 0.1212 ± 0.0011 (CIPT, new D = 4,6,8 condensates; d₄ = 378 ± 378).

Beneke, Jamin, hep-ph:0806.3156: 0.1180 ± 0.0008 (Borel model; favors FOPT; VSA for condensates).

Maltman, hep-ph:0807.0650: 0.1187 ± 0.0016 (CIPT, improved D = 4,6,8 condensates; d₄ = 275 ± 275).

this analysis: 0.1176 ± 0.0018 (FOPT, d₄ = 0).

Strong Coupling from τ Decays: Shifts

old new αs(mτ) αs(MZ)PDG 2008 0.360 0.1225

Vᵘᵈ 0.97451(37) 0.97408(26) 0.362 0.1227B(ΔS=−1) 0.0295(7) 0.0285(7) 0.365 0.1230

δ₂ −0.00044 0 0.364 0.1229δ₂+δ₄+δ₆ −0.0048 +0.0092 0.343 0.1208

d₄ 0 49.08 0.332 0.1195FOPT 0.316 0.1176

simple Padé 0.304 0.1161

Strong Coupling from τ Decays: Schemes

FOPT: a + 5.202 a² + 26.366 a³ + 127.079 a⁴simple Padé: a∕(1 − 5.202 a²) − 0.695 a³ − 13.691 a⁴ CIPT: A₁ + 1.640 A₂ + 6.371 A₃ + 49.076 A₄a = αˢ∕π = 0.100 ± 0.005 ⇒

A₁ = (1.35 ± 0.08) × 10⁻¹, A₂ = (1.56 ± 0.15) × 10⁻², A₃ = (1.58 ± 0.20) × 10⁻³, A₄ = (1.42 ± 0.20) × 10⁻⁴.

140 150 160 170 180 190

mt [GeV]

1000

500

200

100

50

20

10

MH [G

eV

]

excluded

all data (90% CL)

!"!"#

had, R

l, R

q

asymmetries

MW

low-energym

t

LEP 2 Higgs Searches

Contribution to likelihood

Tevatron Higgs Searches

Contribution to likelihood

value error SM pull comment109× g−2− α

π2 4511.07 0.74 4509.04 2.7 incl. τ data

AbFB (LEP) 0.0992 0.0016 0.1033 2.6 best s² at LEP

B(W → τν) 0.1125 0.0020 0.1081 2.2 not used in fitsg2L (NuTeV) 0.3010 0.0015 0.3039 2.0 QED, PDFs

ALR(SLD) 0.1514 0.0022 0.1474 1.9 best s²B(W → µν) 0.1057 0.0015 0.1082 1.7 not used in fitsRν(CHARM) 0.3021 0.0041 0.3091 1.7 sign of NuTeVσ0

had[nb] 41.541 0.037 41.483 1.6 # of ν’s: 2.991(7)Aτ

FB (LEP) 0.0188 0.0017 0.0163 1.5 final result

Small Deviations

Extra Fermion Generation (1)

If degenerate (T = U = 0) ⇒ ΔS = 2∕3π = 0.21; excluded at the 6σ level (Nᴳ = 2.71 ± 0.22).

Complementary to Nᴳ = 2.991 ± 0.007 from before.

Allowing T to float ⇒ T = 0.232 ± 0.045, but Δχ² = 6.8 relative to SM fit with Mᴴ = 117 GeV fixed (also excluded at 99% CL).

Designer splitting of extra doublets: He, Polonsky, Su, hep-ph/0102144, Novikov, Okun, Rozanov, Vysotsky, hep-ph/0203132, Bulanov et al., hep-ph/0301268, Kribs et al., hep-ph/0706.3718.

Extra Fermion Generation (2)

EW fit improves with 4th ν-mass ~50 GeV, but LEP 2 ⇒ it must be stable (dark matter).

To soften S constraint use ΔS ≈ N(1−4Y ln mᵘ/mᵈ)∕6π.

m(ν₄) = 100 GeV, m(l₄) = 155 GeV ⇒ (S,T) ≈ (0,0.05).

m(u₄) = 400 GeV, m(d₄) = 350 GeV ⇒ (S,T) ≈

(0.15,0.14) or a total of (0.15,0.19) (Mᴴ = 115 GeV).

Kribs et al., hep-ph/0706.3718: this is “within the 68% CL contour defined by LEP EWWG”.

ST comparison with LEP EWWG

LEP EWWG (adjusted by Kribs et al.): (S,T) = (0.055, 0.114); my fit: (S,T) = (0.060, 0.114) for same inputs.

αˢ and Δα(had) (incl. τ data) free ⇒ (S,T) = (0.027, 0.088).

Include low energy data but not ν-DIS ⇒(S,T) = (−0.020, 0.041).

Include also ν-DIS (with new NuTeV strange quark asymmetry) ⇒ (S,T) = (−0.054, 0.003).

PDG 2008 update: (S,T) = (−0.042, 0.018).

SI 2008 update: (S,T) = (−0.012±0.087, 0.030±0.083)

Future Perspective

Energy @ startup: 5+5 TeV (before going to 7+7 TeV).

Jet energy scale: 10% initially, 1% with Z calibration.

Lepton energy scale: 1% initially, 0.02% using Zs.

Luminosity determination: 2%

b-tagging efficiency: 60%

A few (expected) LHC facts

150,000,000 W15,000,000 Z11,000,000 t⎬per year in low lumi phase.

1st phase: 200 GeV→ 500 GeV, P(e⁻) > 80%.

Energy scans: ZH and top thresholds.

Integrated luminosity: 500 fb⁻¹ in first 4 years.

2nd phase: upgrade to 1 TeV.

Integrated luminosity: 1000 fb⁻¹ in 3-4 years.

Jet energy scale: 0.3/√E(GeV)

50-60% b-tagging efficiency (30-40% c-tagging)

options: γγ, γe⁻, e⁻e⁻, GigaZ, MegaW, P(e⁺), fixed target polarized (Møller) scattering.

A few (expected) ILC facts

e⁺e⁻ → 4 Fermions (ILC)

✓ O(α) EW corrections: Denner, Dittmaier, Roth, Wieders, hep-ph/0502063, hep-ph/0505042.

✓ W-width effects while maintaining gauge invariance.

➡ W-mass from ILC threshold scan (MegaW) with ± 7 MeV error demands 2-loop precision.

✓ Algebraic reduction of loops to master integrals.

✓ New techniques for calculation of master integrals.

can also be mimicked by

can also be mimicked by

MH = 117 GeV→ 127 GeV

⇔ ∆MW = −5 MeV

⇔ ∆ sin2 θeff.! = +0.00004

Benchmark

∆mpolet = −0.8 GeV or ∆α(MZ) = +0.00028

∆mpolet = −1.3 GeV or ∆α(MZ) = +0.00012

fb⁻¹ ⁄ exp. value [GeV] error / goal ∜L-scalingTevatron Run I 0.11 80.452 59

LEP 2 0.7 80.376 33 37currently 1 80.398 25 34

Tevatron Run IIA 2 21 (e+μ) 29Tevatron Run IIB 7 14 (e+μ) 20

LHC low lumi 10 23 19LHC high lumi 400 7 (e), 6 (μ) 8

ILC 300 10 8MegaW 70 7 4*

*√L-scaling from LEP 2 threshold scan

W Boson Mass: Projections

W Boson Mass: Tevatron Projections

fb⁻¹ ⁄ exp. value error / goal √L-scalingCDF Run IIA 0.072 0.2238 0.0050

SLC 0.05 0.23098 0.00026

LEP 1 0.20 0.23187 0.00021

DØ Run IIA 1.1 0.2327 0.0019 (April) 0.0013currently 0.23153 0.00016

Tevatron Run IIB 8 0.0003 0.0005JLab ee,ep 0.0003

LHC high lumi 400 0.00028 0.00008ILC Møller 0.00007 0.00004

GigaZ 70 0.000013 0.000016

Effective Weak Mixing Angle: Projections

Zbb-Vertex

Ab(GigaZ) =±0.001(factor 15 improvement)

b-Quark Asymmetry: Energy Dependence

0.04

0.06

0.08

0.1

0.12

89 90 91 92 93 94!s [GeV]

AFBb (!

s)LEP

Rb : 2.1σ low,AbFB : 1.6σ highLEP 2:

Weak Mixing Angle: LHC Projections

currently (LEP + SLC): 0.23153 ± 0.00016.

Tevatron Run II expected: ± 0.0003 (10 fb⁻¹).LHC: depends on jet rejection. With 100 fb⁻¹: ± 0.00066 for |η| < 2.5 (compare with Qweak)

± 0.00014 for |η| < 2.5 (for e, μ, τ, b, γ) and |η| < 4.9 (for jets and Eᵀ).

fb⁻¹ ⁄ exp. value [GeV] error / goal ∜L-scalingTevatron Run I 0.11 178.0 4.3

summer 2005 0.43 172.7 2.9 3.1currently 2.8 172.4 1.2 (ICHEP) 1.9

Tevatron Run IIB 7 1.2 1.5LHC low lumi 10 0.7 1.4LHC high lumi 400 0.6 0.6

ILC 300 0.05

± 0.6 GeV theory error to be added except for ILC threshold scan

Top Quark Mass: Projections

Top Quark Mass: Tevatron Projections

Integrated Luminosity (fb-1)

Proj

ecte

d !

mt (

GeV

)

Statistical uncertaintyJES systematic uncertainty (from MW only)Remaining systematic uncertantiesTotal uncertainty

0.5

0.60.70.80.9

1

2

3

4

5

67

10 -1 1 10

Top Quark Mass: LHC Projections

currently: 172.4 ± 1.2 ± 0.6 GeV.

Tevatron Run II expected: ± 1.2 GeV (8 fb⁻¹).Limited by jet energy scale.

LHC: ± 1 (1.7) [3] GeV in lepton + jet (dilepton) [all hadronic] channels (10 fb⁻¹).Close to renormalon uncertainty of ± 0.6 GeV.

Limited by b jet energy scale.

- Perturbative series between pole mass (M) and MS mass (m ) poorly convergent (renormalons).

- Which top mass definition is measured in kinematic reconstruction (pp, pp, e⁺e⁻)?

✓ Fleming, Hoang, Mantry, Stewart, hep-ph/0703207: factorization theorem expressing d²σ∕dMᵗdMᵗ (jet invariant masses) in terms of short-distance mass (m) appearing in HQET Lagrangian.

✓ Hoang, Stuart, hep-ph/0808.0222: m ≡“MSR-mass” satisfying m(m) = m(m ); M[FNAL] = m(3⁺⁶₋₂ GeV) .

Top Quark Mass at Hadron Colliders

Running Electromagnetic Coupling

Improved recently, but still largest theory uncertainty.

Would need more than a factor of 3 improvement to match GigaZ precision of weak mixing angle.

May be possible with combined effort from theory and experiments in e⁺e⁻-annihilation (statistics), radiative returns (systematics), and τ-decays (theory; isospin!).

Pion form factor & charm continuum threshold region!

Expect continued incremental progress.

∆α(5)had.(MZ)≈ 0.02786±0.00012

error (accumulated)currently 29%

Tevatron Run II 23%LHC low lumi (incl. JLab) 20%

LHC high lumi 15%ILC 11%

GigaZ/MegaW 10%GigaZ/MegaW + Δα(had) 7%

GigaZ/MegaW + Δα(had) + αˢ 4%

direct (ZH threshold scan): ± 40 MeV

Higgs Boson Mass from Loops: Projections

Higgs Boson Physics: Projections

LHC: Higgs primarily from gluon fusion, gg → H, vector boson fusion, qq’ → Hqq’, and associated production, pp → ttH ⇒ Htt-Yukawa (20-30%).

Hbb, Hττ, WWH, ZZH couplings (10-30%).

λ to 20 (70)% for 150-200 (<140) GeV Higgs (3 ab⁻¹).ILC: e⁺e⁻→ZH→l⁺l⁻H (Higgs-strahlung); e⁺e⁻→ ttH.

Hbb, Hττ, Htt, WWH, ZZH very precise, Hcc less.

λ to 20% for a 120 GeV Higgs (e.g. in e⁺e⁻ → ZHH).

Top Quark Physics

Single top production: measure Vᵗᵇ, Tevatron Run II expected: ± 9% (10 fb⁻¹), LHC: ± 5% (30 fb⁻¹).Anomalous FCNC couplings: HERA, Tevatron (LHC) sensitive at 10⁻¹ to 10⁻² (10⁻⁴ to 10⁻⁵) level, SM 10⁻¹⁴: t → Vq (V = Z, γ, g; q ≠ b) (also constrains W′).tt spin correlations (± 10%): establish spin ½, test non-standard production (resonances), decay to H⁺b.

Mᵗᵗ invariant mass distribution: resonances (e.g. M(Z′) > 760 GeV from D0) or interference with new physics.

Top mass distribution ⇒ m(t′) > 311 GeV (CDF).

Low Energy Measurements

Complemenarity.

Diagnostics.

Discovery potential.

Why are low energy measurement needed if we have the LHC and perhaps an ILC?

Advertisement

Workshop:

Low Energy Precision Electroweak Physics in the LHC Era

Institute for Nuclear Theory University of Washington, Seattle, WA

September 22 - December 5, 2008

http://www.int.washington.edu/PROGRAMS/08-3.html

Please apply! (application form under above link)

Low Energy Measurements: Examples (1)

Muon anomalous magnetic moment (BNL).

ν-DIS (NuTeV, CCFR, CHARM, CDHS).

Lepton scattering (E-158, CHARM II).

Elastic polarized ep-scattering (Qweak).

Quasi-elastic polarized eN-scattering.

Atomic P: Cs (Boulder, Paris), Tl (Oxford, Seattle).

b → s γ (BaBar, Belle, CLEO).

Michel parameters (TWIST).

Low Energy Measurements: Examples (2)

Electric Dipole Moments.

Lepton Flavor Violation.

CKM-unitarity (1st row).

p-decay and n-oscillations.

ν-oscillations.

0νββ-decay.

Variation of fundamental constants.

Flavor changing neutral currents.

Polarized Electron Scattering

LR cross-section asymmetry: Interference between P conserving γ amplitude and P Z⁰ mediated amplitude.

eD-DIS (1978): Q²⁄M² ~ 10⁻⁴ ⇒ 10⁻⁵ uncertainty ↔10% determination of Z⁰ amplitude (SLAC)

e⁻e⁻ (Møller)-scattering (2005): Q² = 0.026 GeV²; Aᵖᵛ = (-1.31 ± 0.17)×10⁻⁷ (SLAC) ⇒sin²θᵂ(Q²) = 0.2397 ± 0.0013 ; improve at JLab?

e⁻p-scattering (Qweak, 2011): same Q² ⇒ weak charge of the proton (∝ 1−4 sin²θᵂ) to ±4% (JLab).

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Atomic Parity Violation (APV)

APV → mixing between opposite parity states.

Effect extremely small; use small modulation of level mixing by external electric field (Stark-mixing).

Effect ∝ Z³ ⇒ use heavy atoms.

Comparison of hyperfine levels ⇒ weak charges and anapole moment.

Complication: atomic structure calculations.

Most precise: ⁷s→⁶s transition in Cs (Boulder) ⇒ Qᵂ(Cs) = 72.62 ± 0.46 ⇒ sin²θᵂ = 0.2291 ± 0.0019.

NuTeV (νN and νN-scattering)

2.0 σ deviation from SM ⇒ new physics?

Was 2.7 σ before inclusion of ∫ dx x (S − S) = 0.0020 ± 0.0014 (NuTeV now agrees with CTEQ).

New QED radiative corrections (Diener, Dittmaier, Hollik) but not yet included by NuTeV collaboration.

Valence parton Charge Symmetry Violation (CSV) due to “quark model” and “QED splitting effects” each predict removal of 1 σ; phenomenological parton CSV PDFs can remove or double the effect (MRST).

Nuclear effects: different for NC and CC; 20% of effect, both signs possible (Brodsky, Schmidt, Yang).

Muon g−2: Issues

2.7 σ deviation from SM ⇒ supersymmetry?

For 2-loop vacuum polarization contribution need optical theorem and same data as for running α and running weak mixing angle.

Inconsistencies between τ decay and e⁺e⁻ data.

Inconsistencies between e⁺e⁻ annihilation data.

Extra trouble: 3-loop light-by-light contribution.

Quark level estimate (JE, G. Toledo, hep-ph/0605052) aᴸᴮᴸ(μ, had) < 1.59 × 10⁻⁹.

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4.5 σ discrepancy between B(τ→νππ) from electro-production and direct

Conclusions

SM still standing (only relatively small number of statistically insignificant deviations).

Searches at the Tevatron Run II and the LHC likely to yield discovery of new physics.

Electroweak precision measurements both at colliders and low-energy will give guidance and discriminatory power as to what was discovered.