Boost 2014

Particle Physics after LHC Run I

Electroweak Precision Measurements: Today

J. Hewett

The Electroweak Sector of the SM

§  EW sector described by 3 parameters @ tree-level »  g,g’ Coupling constants of SU(2)LxU(1)Y »  Vacuum expectation value »  Weak mixing angle

§  In calculations, trade for the most precisely measured parameters »  α: Δα/α = 3x10-10 »  GF: ΔGF/GF = 5x10-7 »  MZ: ΔMZ/MZ = 2x10-5

Importance of Radiative Corrections §  Modify gauge boson propagators and vertices §  Parameterize as form factors

ρf, κf, Δr

§  Effective couplings at Z-pole

§  Mass of the W-boson

Importance of Radiative Corrections §  Modify gauge boson propagators and vertices §  Parameterize as form factors

ρf, κf, Δr

§  Effective couplings at Z-pole

§  Mass of the W-boson Flavor dependent!

Additional Parameters Come Into Play

§  EW form factors ρf, κf, Δr depend on all parameters in the SM

§  EW Sector §  GF, MZ, evolution of α to scale µ

§  Fermion masses §  mc,b,t

§  Strong sector §  αs

§  Higgs sector §  mh

Additional Parameters Come Into Play

§  EW form factors ρf, κf, Δr depend on all parameters in the SM

§  EW Sector §  GF, MZ, evolution of α to scale µ

§  Fermion masses §  mc,b,t

§  Strong sector §  αs

§  Higgs sector §  mh

Logarithmic dependence

Quadratic dependence

Measurements at Z-pole §  Peak hadronic cross section

§  Total and partial widths

§  Decay ratios

§  Asymmetries

Top-quark Mass Determination

mt loop predictions since 1990!

EW fits have been proven to be very accurate

Final Results of Z-pole Measurements

LEPEWWG: Now translated into Haitian Creole and Ukrainian

2005 Physics Reports detailing final results

Global fits now being performed by the Gfitter group

hep-ex/0509008

Final Results of Z-pole Measurements: 2005

0

1

2

3

4

5

6

10030 500mH [GeV]

∆χ

2

Excluded

∆αhad =∆α(5)

0.02758±0.000350.02749±0.00012incl. low Q2 data

Theory uncertainty

Measurement Fit |Omeas−Ofit|/σmeas

0 1 2 3

0 1 2 3

∆αhad(mZ)∆α(5) 0.02758 ± 0.00035 0.02767mZ [GeV]mZ [GeV] 91.1875 ± 0.0021 91.1874ΓZ [GeV]ΓZ [GeV] 2.4952 ± 0.0023 2.4965σhad [nb]σ0 41.540 ± 0.037 41.481RlRl 20.767 ± 0.025 20.739AfbA0,l 0.01714 ± 0.00095 0.01642Al(Pτ)Al(Pτ) 0.1465 ± 0.0032 0.1480RbRb 0.21629 ± 0.00066 0.21562RcRc 0.1721 ± 0.0030 0.1723AfbA0,b 0.0992 ± 0.0016 0.1037AfbA0,c 0.0707 ± 0.0035 0.0742AbAb 0.923 ± 0.020 0.935AcAc 0.670 ± 0.027 0.668Al(SLD)Al(SLD) 0.1513 ± 0.0021 0.1480sin2θeffsin2θlept(Qfb) 0.2324 ± 0.0012 0.2314mW [GeV]mW [GeV] 80.425 ± 0.034 80.389ΓW [GeV]ΓW [GeV] 2.133 ± 0.069 2.093mt [GeV]mt [GeV] 178.0 ± 4.3 178.5

“Blue-band” plot

Final Results of Z-pole Measurements: 2005

10 2

10 3

0.23 0.232 0.234

sin2θlepteff

m H [Ge

V]

χ2/d.o.f.: 11.8 / 5

A0,lfb 0.23099 ± 0.00053

Al(Pτ) 0.23159 ± 0.00041

Al(SLD) 0.23098 ± 0.00026

A0,bfb 0.23221 ± 0.00029

A0,cfb 0.23220 ± 0.00081

Qhadfb 0.2324 ± 0.0012

Average 0.23153 ± 0.00016

∆αhad= 0.02758 ± 0.00035∆α(5)

mt= 178.0 ± 4.3 GeV

Final fit to sin2 ϑeff

This ~3σ discrepancy has haunted us for years

What’s New Since 2005: Theory

R. Kogler

Higgs!! `I Think We Have It’

§  Our shiny new Boson!

[GeV]4lm100 150 200 250

Even

ts/5

GeV

0

5

10

15

20

25

30

35

40

-1Ldt = 4.6 fb∫ = 7 TeV s-1Ldt = 20.7 fb∫ = 8 TeV s

4l→ZZ*→HData 2011+ 2012SM Higgs Boson

=124.3 GeV (fit)H mBackground Z, ZZ*

tBackground Z+jets, tSyst.Unc.

ATLAS

Higgs Boson Mass Determination

1407.3792

Higgs mass predictions since top discovery

Weaker predictions due to log dependence

EW fits have been proven to be very accurate

Global Fit: 2014

1407.3792

•  For the first time all observables can be uniquely predicted

•  All data agree well with the fit

•  Inclusion of mh has modest effects

•  Χ2/dof = 18.1/14

The 2014 Electroweak Fit

Fits have been performed with and without the measured Higgs mass

Measured and fitted Higgs mass agree well!

Measured Higgs mass dominates fit

1407.3792

Fit to W-Boson Mass

1407.3792

Oblique Precision EW Parameters

STU parameters designed to “automate” BSM fits to EW data Peskin, Takeuchi ’91

Before Higgs discovery, new physics could hide in mh uncertainties

Oblique Precision EW Parameters: 2014

STU fit is now very precise

1407.3792

The Future: Use Higgs as a Tool for Discovery §  Higgs offers unique portal for discovery §  Key properties we need to understand »  Total width »  Couplings to SM particles »  Shape of Higgs potential: self-interactions »  Is there a CP-odd component? »  Do Higgs couplings violate flavor? »  How does Higgs interact with neutrinos? »  Does the Higgs generate mass for Dark Matter? »  How many Higgs Bosons are there? »  Is Higgs elementary or composite? »  Is the universe in a false vacuum?

Study the Higgs in as much detail as possible!

Higgs Coupling Measurements §  Higgs is looking more-or-less SM-like, but

measurements have large errors at present

•  tth is 2σ from SM value

•  Something to watch!

Fermion/Boson Couplings

•  Assume all fermions couple with common strength κF •  Assume all bosons couple with common strength κV •  No BSM contributions to κγ,g loops

•  κF,V ≠ 0 @ > 5σ!

Precision Measurements of Higgs Couplings §  Indirect effects of Supersymmetry affects Higgs couplings

§  pMSSM Study: Higgs coupling measurements sensitive to models not accessible to HL-LHC

Cahill-Rowley, JLH, Ismail, Rizzo, 1407.7021

Study Ratio: ΓpMSSM/ΓSM

ττ bb

The Future: Higgs Coupling Fits

Collider Sensitivity to Higgs Self-Coupling

Full ILD detector simulation @ILC with hh to bbbb, bbWW* final states

1310.0763, 1307.5288

bbγγ final state sensitivity/detector More studies needed!

1310.8361 Hadron Colliders

e+e- Colliders

VERY important measurement to determine shape of Higgs potential

Higgs Couplings: Model Independent Approach

§  In a complete analysis all 34 + 25 4-fermion operators need to be considered.

§  Demonstrates the art of choosing a basis

Grzadkowski etal 1008.4884

Summary

§  SM agrees well (too well!) with data §  The newly discovered scalar particle agrees with SM

Higgs predictions to the accuracy obtainable so far §  No new physics has yet to reveal itself

§  Future prospects »  High accuracy Δ(g-2)µ soon underway @FNAL »  13 TeV LHC operations commence next Spring!

•  Study Higgs properties to better precision •  Improved measurements of MW •  Search for new physics

»  ILC is on the horizon and will achieve unprecedented precision

•  Will write the book on Higgs measurements