Electroweak Physics: Present and Future Jens Erler (IF-UNAM) XV MWPF - PowerPoint PPT Presentation

Electroweak Physics: Present and Future Jens Erler (IF-UNAM) XV MWPF 2015 Mazatlan, November 5, 2015

Outline Preliminaries / introduction Weak boson masses The weak mixing angle Oblique parameters (STU) Low energy precision tests Parity violation Contact interactions Conclusions 2

Introduction

Recent reviews Krishna Kumar, Sonny Mantry, William Marciano and Paul Souder Annu. Rev. Nucl. Part. Sci. 63 (2013) 237–67 Jens Erler and Shufang Su Prog. Part. Nucl. Phys. 71 (2013) 119–149 Jens Erler and Ayres Freitas Particle Data Group (2014) Jens Erler, Charles Horowitz, Sonny Mantry and Paul Souder Annu. Rev. Nucl. Part. Sci. 64 (2014) 269–298 4

Introduction t t t b b b ν τ τ b ̅ b ̅ b ̅ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ c c c s s s ν μ μ c ̅ c ̅ c ̅ s ̅ s ̅ s ̅ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ e e u u u d d d ν u ̅ u ̅ u ̅ d ̅ d ̅ d ̅ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ s= ½ H H Z W W g g g g g g g g G γ s=0 s=0 s=1 s=1 s=1 s=1 s=1 s=1 s=1 s=1 s=1 s=1 s=1 s=1 s=2 (before electroweak symmetry breaking) 5

Key SM Parameters 4 parameters from bosonic sector: g, g ′ L φ = ( D µ φ ) † D µ φ − µ 2 φ † φ − λ 2 2 ( φ † φ ) 2 � h / m Rb : α ≡ g 2 sin 2 θ W ∕ 4 π (± 6.6 × 10 − 10 ) g e − 2: α ≡ g 2 sin 2 θ W ∕ 4 π (± 8 × 10 − 13 ) [derived] PSI: G F ≡ 1 ∕ ( √ 2 v 2 ) (± 5 × 10 − 7 ) [v = 246.22 GeV] LEP 1: M Z ≡ M W ∕ cos θ W (± 2 × 10 − 5 ) Tevatron: M W ≡ g v ∕ 2 (± 2 × 10 − 4 ) [derived] Z pole: sin 2 θ W ≡ g ′ 2 ∕ (g 2 + g ′ 2 ) (± 7 × 10 − 4 ) [derived] LHC: M H ≡ λ v = √ ( − 2 μ 2 ) (± 3 × 10 − 3 ) LHC / Tevatron: m t (m t ) ≡ λ t v (± 6 × 10 − 3 ) 6

History 1950s: development of fundamental ideas underlying the SM (Yang-Mills theory, parity violation, V − A, intermediate vector bosons) 1960s: construction of the SM (gauge group, Cabbibo-universality, Higgs mechanism, model of leptons) 1970s: discovery of key predictions of the SM (neutral currents, APV, ν -scattering, polarized DIS) 1980s: establishment of basic structure of the SM (discovery of W & Z, mutually 2 θ W = g ′ 2 ∕ (g 2 + g ′ 2 ) from many different processes) consistent values of sin 1990s (LEP , SLC): confirmation of the SM at the loop level ⇒ new physics at most a perturbation 2000s (Tevatron): ultra-high precision in m t (0.5%) and M W (0.02%) ⇒ (most of) new physics seperated by at least a little hierarchy (or else conspiracy or very weak coupling) 2010s (LHC, intensity frontier): EW symmetry breaking sector (Higgs & BSM) 7

Complementary physics High-energy � Collider � Energy precision tests searches EW symmetry � new particles � breaking & states Low-energy � Flavor � precision tests physics symmetries and � new amplitudes conservation � Intensity laws 8

Complementary tools High-energy � Collider � M W precision tests searches sin 2 θ W Z & H properties EW symmetry � top quark properties breaking Low-energy � Flavor � polarized e − scattering precision tests physics ν scattering atomic parity violation new amplitudes lepton properties 9

Complementary facilities High energy lepton High-energy � Collider � and hadron colliders precision tests searches LEP & SLC Tevatron & LHC EW symmetry � ILC, CEPC (SppC) & FCC breaking Medium energy Low-energy � Flavor � accelerators & table-top precision tests physics CEBAF (Je ff eron Lab) MESA (Mainz) new amplitudes flavor physics facilities 10

Weak boson masses

M H from radiative corrections Consider fundamental SM relations like sin 2 θ W = g ʹ 2 ∕ (g 2 + g ʹ 2 ) = 1 − M W2 ∕ M Z2 ∕ (1 + ∆ρ ) or √ 2 G F (1 − ∆ r) = e 2 ∕ (4 sin 2 θ W M W2 ) Compute radiative correction parameters such as ∆ρ and ∆ r to very high (two-loop EW) accuracy These are functions of m t , M H , M Z , …, as well as M W and sin 2 θ W themselves (needs numerical iterations) Compare with experimental ∆ρ and ∆ r to test SM and look for deviations (new physics) 12

M H from Higgs branching ratios? 13

M H from Higgs branching ratios? 14

Compare with results on coupling strength 15

M H [GeV] source M(H) uncertainty +22 radiative corrections 89 –18 LHC Higgs branching ratios 123.7 ±2.3 ATLAS & CMS 125.09 ±0.24 (combination 2015) JE, Freitas 2013 PDG 2014 16

all precision data (90% CL) direct (1 σ ) indirect (1 σ ) M H = 125.9 GeV 80.4 M W [GeV] 80.3 160 170 180 m t [GeV] 17

all precision data (90% CL) direct (1 σ ) indirect (1 σ ) M H = 125.9 GeV 80.4 M W [GeV] direct (1 σ ) 80.42 indirect (1 σ ) 80.41 all data (90%) 80.40 80.3 160 170 180 80.39 M W [GeV] m t [GeV] 80.38 80.37 80.36 80.35 80.34 171 174 175 177 170 172 173 176 178 179 180 m t [GeV] 18

all precision data (90% CL) direct (1 σ ) 80.42 direct (1 σ ) indirect (1 σ ) indirect (1 σ ) 80.41 all data (90%) M H = 125.9 GeV 80.40 80.4 M W [GeV] 80.39 M W [GeV] 80.38 80.37 1000 Γ Z , σ had , R l , R q (1 σ ) 80.36 Z pole asymmetries (1 σ ) 500 M W (1 σ ) 80.35 direct m t (1 σ ) 300 80.34 direct M H 80.3 200 precision data (90%) 171 174 175 177 170 160 172 173 170 176 178 180 179 180 M H [GeV] m t [GeV] m t [GeV] 100 50 30 20 10 155 175 150 160 165 170 180 185 m t [GeV] 19

80.60 experimental errors 68% CL / collider experiment: LEP2/Tevatron: today ILC M h = 125.6 ± 3.1 GeV 80.50 MSSM M W [GeV] Heinemeyer, Hollik, � Weiglein, Zeune 2013 80.40 SM M H = 125.6 ± 0.7 GeV MSSM 80.30 SM, MSSM Heinemeyer, Hollik, Stockinger, Weiglein, Zeune ’13 168 170 172 174 176 178 m t [GeV] 20

The weak mixing angle W ± = (W 1 ∓ i W 2 ) ∕√ 2 Z 0 = cos θ W W 3 – sin θ W B A = sin θ W W 3 + cos θ W B � � M W = ½ g v = cos θ W M Z sin 2 θ W = g ′ 2 ∕ (g 2 + g ′ 2 ) = 1 – M W2 ∕ M Z2

Renormalization schemes Many different schemes and definitions. Most commonly used: M ̅ S ̅ -scheme: sin 2 θ̅ W ( μ ) ≡ g ʹ ̅ 2 ∕ (g ̅ 2 + g ʹ ̅ 2 ) (theorist’s definition) ideal for gauge coupling unifcation (analogous to α̅ s in QCD) effective weak mixing angle in terms of vector (g V ∝ 1 – 4 Q f sin 2 θ W ) and axial-vector couplings g A (experimentalist’s definition) 2 g f V g f 1 − g ` �  � e ff ≡ 1 = sin 2 ˆ sin 2 θ ` V A f ≡ A θ W ( M Z ) + 0 . 00029 V ) 2 + ( g f ( g f g ` 4 A ) 2 � A numerically close to sin 2 θ̅ W (M Z ) on-shell definition: sin 2 θ W ≡ 1 – M W 2 ∕ M Z 2 2 -dependence (enhances higher order contributions) induces spurious m t 22

Asymmetries 2 + a e 2 )] Z-pole: χ ~ M Z / Γ Z ≫ 1 ⟹ [with A f = 2 v e a e / (v e A e A μ (A FB ) LEP A τ (final state A pol ) LEP A e (A LR ) SLD LR ) SLD A μ (A FB PVES / e + e – annihilation: χ ~ Q 2 G F ≪ 1 ⟹ a e v f (A LR in forward direction) SLAC-E122 & E158, Qweak, MOLLER, P2 v e a q (A LR at larger scattering angles) PVDIS, SoLID a e a μ (A FB ) Belle II (independent of sin 2 θ W ) � 23

Z-pole asymmetries 0,l A 0.23099 ± 0.00053 fb A l (P � ) 0.23159 ± 0.00041 A l (SLD) 0.23098 ± 0.00026 0,b A 0.23221 ± 0.00029 fb 0,c A 0.23220 ± 0.00081 fb had Q 0.2324 ± 0.0012 fb LEP/SLC Average: 0.23153 ± 0.00016 χ 2 ∕ d.o.f. = 16.8 ∕ 12 Average 0.23153 ± 0.00016 � � 2 /d.o.f.: 11.8 / 5 10 3 CDF: 0.2315 ± 0.0010 DO: 0.23146 ± 0.00047 m H [ GeV ] ATLAS: 0.2308 ± 0.0012 � Grand Average: 0.23151 ± 0.00015 10 2 � �� (5) �� had = 0.02758 ± 0.00035 m t = 172.7 ± 2.9 GeV Standard Model: 0.23155 ± 0.00005 0.23 0.232 0.234 24 lept sin 2 � eff

0.235 0.235 0.234 0.234 2 θ eff (e) 0.233 0.233 A FB (b) sin 0.232 0.232 0.231 0.231 A LR (had) 0.230 0.230 10 100 1000 10000 M H [GeV] JE 2015 25

M ̅ S ̅ -scheme 0.245 SM published planned NuTeV antiscreening Q W (e) Q W (p) 0.240 SLAC JLab 2 θ W ( µ ) screening Q W (Cs) eDIS 0.235 sin JLab LEP 1 Tevatron SLD Q W (p) 0.230 LHC Mainz Q W (Ra) Q W (e) SoLID KVI JLab JLab 0.225 0.001 0.01 0.1 1 10 100 1000 10000 JE 2014 µ [GeV] 26

M ̅ S ̅ -scheme 0.245 SM published planned NuTeV antiscreening Q W (e) Q W (p) 0.240 s c SLAC i JLab d t s e i t t a a 2 θ W ( µ ) t n s i m screening o Q W (Cs) d eDIS 0.235 sin JLab ILC � fixed target LEP 1 Tevatron SLD Q W (p) 0.230 LHC strongly Mainz systematics Q W (Ra) Q W (e) SoLID dominated KVI JLab JLab 0.225 1 0.001 0.01 0.1 10 100 1000 10000 JE 2013 µ [GeV] 27

Oblique parameters (STU)

Oblique physics beyond the SM STU describe corrections to gauge-boson self-energies T breaks custodial SO(4) a non-degenerate SU(2) L doublet contributes Δ T ≈ Δ m 2 /(264 GeV) 2 Currently: ∑ i C i /3 Δ m i2 ≤ (50 GeV) 2 a multiplet of heavy degenerate chiral fermions contributes Δ S = N C ∕ 3 π ∑ i [t 3Li − t 3Ri ] 2 extra degenerate fermion family yields Δ S = 2 ∕ 3 π ≈ 0.21 S and T (U) correspond to dimension 6 (8) operators 29