Status and Phenomenology of the Standard Model

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1 Status and Phenomenology of the Standard Model The new standard model Experimental tests, unique features, anomalies, hints of new physics Precision tests Higgs Heavy quarks Neutrinos FCNC and EDMs Astrophysics and cosmology Theoretical problems Perspective

2 The New Standard Model Standard model, Majorana): supplemented with neutrino mass (Dirac or SU(3) SU(2) U(1) classical relativity }{{} focus of talk Mathematically consistent field theory of strong, weak, electromagnetic interactions Correct to first approximation down to cm Complicated, free parameters, fine tunings must be new physics

3 Many special features usually not maintained in BSM m ν = 0 in old standard model (need to add singlet fermion and/or triplet Higgs and/or higher dimensional operator (HDO)) Yukawa coupling h gm/m W flavor conserving and small for light fermions (partially maintained in MSSM and simple 2HDM) No FCNC at tree level (Z or h); suppressed at loop level (SUSY loops; Z from strings, DSB) Suppressed off-diagonal CP ; highly suppressed diagonal (EDMs) (SUSY loops, soft parameters, exotics) B, L conserved perturbatively (B L non-perturbatively) (GUT (string) interactions, R p ) New TeV scale interactions suggested by top-down (Z, exotics, extended Higgs)

4 The Weak Charged Current Fermi Theory incorporated in SM and made renormalizable CKM matrix for F = 3 involves 3 angles and 1 CP -violating phase (after removing unobservable q L phases) (new interations involving q R could make observable) V = V ud V us V ub V cd V cs V cb V td V td V td Extensive studies, especially in B decays, to test unitarity of V as probe of new physics and test origin of CP violation Need additional source of CP breaking for baryogenesis

5 Overconstrain unitarity triangle as test of SM η Babar, Belle: sin 2β = ± from Bd 0(t) J/ψK S (little theory error) R u (ρ,η) α R t α, γ harder Anomalies in electroweak penguins? γ (0,0) (1,0) β

6 1.5 excluded area has CL < sin 2β m d η ε K γ α β B ρρ m s & m d V ub /V cb -0.5 ε K -1 C K M f i t t e r Winter 2004 B ρρ ρ

7 The Weak Neutral Current Prediction of SU(2) U(1) WNC discovered 1973: Gargamelle at CERN, HPW at FNAL Tested in many processes: νe νe, νn νn, νn νx; e D ex; atomic parity violation; e + e, Z-pole reactions WNC, W, and Z are primary test/prediction of electroweak model

8 The LEP/SLC Era Z Pole: e + e Z l + l, q q, ν ν LEP (CERN), Z s, unpolarized (ALEPH, DELPHI, L3, OPAL); SLC (SLAC), , P e 75 % (SLD) Z pole observables lineshape: M Z, Γ Z, σ branching ratios e + e, µ + µ, τ + τ q q, c c, b b, s s ν ν N ν = ± if m ν < M Z /2 asymmetries: FB, polarization, P τ, mixed lepton family universality

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10 LEP averages of leptonic widths Γ e ± 0.12 MeV Γ µ ± 0.18 MeV Γ τ ± 0.22 MeV Γ l ± 0.09 MeV m H [GeV] m Z = ± 2 MeV m t = ± 5.1 GeV [MeV] Γ l

11 Winter 2004 Measurement Fit O meas O fit /σ meas α (5) had (m Z ) ± m Z [GeV] ± Γ Z [GeV] ± σ 0 had [nb] ± R l ± A 0,l fb ± A l (P τ ) ± R b ± R c ± A 0,b fb ± A 0,c fb ± A b ± A c ± A l (SLD) ± sin 2 θ lept eff (Q fb ) ± m W [GeV] ± Γ W [GeV] ± m t [GeV] ±

12 Gauge Self-Interactions Three and four-point interactions predicted by gauge invariance Indirectly verified by radiative corrections, α s running in QCD, etc. Strong cancellations in high energy amplitudes would be upset by anomalous couplings Tree-level diagrams contributing to e + e W + W

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14 The Precision Program WNC, Z, Z-pole, W, m t Implications SM correct and unique to zeroth approx. (gauge principle, group, representations) SM correct at loop level (renorm gauge theory; m t, α s, M H ) TeV physics severely constrained (unification vs compositeness) Precise gauge couplings (gauge unification)

15 Problems with the Standard Model Lagrangian after symmetry breaking: ( ψ i i m i m ih ν L = L gauge + L Higgs + i g ( ) 2 J µ W 2 W µ + J µ W W + µ ej µ Q A µ ) ψ i g 2 cos θ W J µ Z Z µ Standard model: SU(2) U(1) (extended to include ν masses) + QCD + general relativity Mathematically consistent, renormalizable theory Correct to cm

16 However, too much arbitrariness and fine-tuning: O(27) parameters (+ 2 for Majorana ν), and electric charges Gauge Problem complicated gauge group with 3 couplings charge quantization ( q e = q p ) unexplained Possible solutions: strings; grand unification; magnetic monopoles (partial); anomaly constraints (partial) Fermion problem Fermion masses, mixings, families unexplained Neutrino masses, nature? CP violation inadequate to explain baryon asymmetry Possible solutions: strings; brane worlds; family symmetries; compositeness; radiative hierarchies. New sources of CP violation.

17 Higgs/hierarchy problem Expect M 2 H = O(M 2 W ) higher order corrections: δm 2 H /M 2 W 1034 Possible solutions: supersymmetry; dynamical symmetry breaking; large extra dimensions; Little Higgs Strong CP problem Can add θ 32π 2 g 2 s F F to QCD (breaks, P, T, CP) d N θ < 10 9 but δθ weak 10 3 Possible solutions: spontaneously broken global U(1) (Peccei- Quinn) axion; unbroken global U(1) (massless u quark); spontaneously broken CP + other symmetries

18 Graviton problem gravity not unified quantum gravity not renormalizable cosmological constant: Λ SSB = 8πG N V > Λ obs ( for GUTs, strings) Possible solutions: supergravity and Kaluza Klein unify strings yield finite gravity. Λ?

19 (Nearly) Unique Features of the old Standard Model m ν = 0 in old standard model (need to add singlet fermion and/or triplet Higgs and/or higher dimensional operator (HDO)) Oscillation experiments confirm non-zero masses, LMA, SSM (also helioseismology) Excluded sterile, RSPF, new interactions as dominant Oscillation dip observed (further constrains/excludes alternatives)

20 3 ν Patterns Solar: LMA (SNO, Kamland) m ev 2 for LMA Atmospheric: m 2 Atm ev 2, nearmaximal mixing Reactor: U e3 small

21 2 ) (ev 2 m ) 2 (ev 2 m Solar 95% C.L. 99% C.L % C.L. solar best fit tan 2 θ KamLAND 95% C.L. 99% C.L % C.L. KamLAND best fit tan 2 θ KamLAND+Solar fluxes 95% C.L. 99% C.L % C.L. global best fit

22 Data/Prediction (null osc.) L/E (km/gev)

23 Mixings: let ν ± 1 2 (ν µ ± ν τ ): ν 3 ν + ν 2 cos θ ν sin θ ν e ν 1 sin θ ν + cos θ ν e Hierarchical pattern Analogous to quarks, charged leptons ββ 0ν rate very small Inverted quasi-degenerate pattern ββ 0ν if Majorana May be radiative unstable

24 Outstanding issues Dirac or Majorana Distinguish by ββ 0ν, at least for inverted, degenerate. Observation? Dirac Mass Connects distinct Weyl spinors (usually active to sterile): (m D ν L N R + h.c.) 4 components, L = 0 I = 1 Higgs doublet 2 Why small? LED? HDO? ν L h N R v = φ m D = hv

25 Majorana Mass Connects Weyl spinor with itself: 1 2 (m T ν L νr c + h.c.) (active); 1 2 (m S N L cn R + h.c.) (sterile) 2 components, L = ±2 Active: I = 1 triplet or seesaw Sterile: I = 0 singlet or bare mass ν L ν c R ν L ν L

26 Scale of neutrino masses: 0.05 ev < m ν < O(0.3 ev). Probe by β decay (KATRIN), cosmology, ββ 0ν Type of hierarchy: ββ 0ν U e3, leptonic CP LSND? Additional (sterile) neutrino(s) which mix with ordinary. MiniBooNE. Leptogenesis?

27 Flavor Changing Neutral Currents In SM: Yukawa coupling h gm/m W flavor conserving and small for light fermions (partially maintained in MSSM and simple 2HDM) In SM: no FCNC at tree level (Z or h); suppressed at loop level Violated in almost all extensions, including SUSY loops; Z from strings, DSB Hard to give precise expectations, but critical to search Third family transitions (rare B, τ ) often largest, but small induced effects in first two families (µ, K decays) may be more sensitive (MEG at PSI, MECO at BNL, PRIME at JHF)

28 History of Lepton Flavor Violation Searches " - N # e - N " + # e + $ " + # e + e + e K 0% #" + e - K +% #& + " + e - SINDRUMII MECO Goal! P. Souder, Syracuse From Zero to... 5/13/04 8

29 What might we expect? Supersymmetry Predictions at ~ ~ l µ - j l j e - q ~ χ 0 i q µ - q e - q Compositeness!! 3000 TeV C Heavy Neutrinos ( 2 % 13 " N en! # U U 8 10 N µ - W e - q q e - µ - e - H t t t q q Second Higgs g =10 g -4 H" e # H"" M L Leptoquarks! 3000 ) ) TeV/c " d ed 2 µ - d L d e - µ - e - γ,z,z q q After W. Marciano Heavy Z, Anomalous Z coupling M Z$! 3000 TeV/c B(Z & " e) ' 10 % 17 2 P. Souder, Syracuse From Zero to... 5/13/04 10

30 CP Violation SM: suppressed off-diagonal CP ; highly suppressed diagonal (EDMs) Larger in SUSY (loops, soft parameters) unless tuning or cancellations Larger in other extensions, e.g., singlet scalars in Z models (but may be hidden) B decays, leptonic CP, EDMs Need additional CP for baryogenesis

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32 Baryon and Lepton Number Violation SM: B, L conserved perturbatively (B L non-perturbatively) Violated in BSM, e.g., by GUT (string) interactions or R p Proton decay expected at some level in many extensions, especially Planck scale L needed for Majorana neutrino masses ββ 0ν New B and/or L invoked in some baryogenesis schemes

33 mode exposure εb m observed B.G. (ktï yr) (%) event p e + + π p µ + + π p e + + η p µ + + η n ν + η p e + + ρ p e + + ω p e + + γ p µ + + γ p ν + K K + νµ + (spectrum) prompt γ + µ K + π + π n ν + K K 0 π 0 π K 0 π + π p e + K K 0 π 0 π K 0 π + π - 2-ring ring p µ + K K 0 π 0 π K 0 π + π - 2-ring ring p e + π 0 e + η e + ω e + ρ 0 e + K 0 µ + π 0 µ + η µ + ω µ + ρ 0 µ + K 0 + ν π ν ρ + + ν K n e + π - e + ρ - µ + π - µ + ρ - ν π 0 ν η ν ω ν ρ 0 0 ν K SK IMB3 KAM Soudan lifetime limit (years)

34 TeV Physics New TeV scale interactions suggested by top-down Z or other new interactions Implications for highly non-standard Higgs, FCNC, CDM, baryogenesis Exotics Extra Higgs doublets and singlets Exotic quarks and leptons Fractional charges Quasi-hidden sectors

35 Hints and Anomalies Gauge unification in supersymmetric extension If not accident or compensation, severely limits new TeV scale physics Precision data suggests light Higgs

36 Precision data suggests light Higgs M H = GeV (< 246 GeV at 95% including indirect) Consistent with SUSY (but does not prove) χ Theory uncertainty α (5) α had = ± ± incl. low Q 2 data Has increased due to new D0 m t value and lower M W A b F B pulls up, A l down 1 0 Excluded m H [GeV] Preliminary

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38 Atomic parity violation? Now in agreement after complete radiative corrections. NuTeV? Unresolved. Likely QCD or structure function issue. Electroweak penguins in B φk S, Kπ? b V qb W + V qd d Experimental situation uncertain SUSY loops for large tan β or tree effects, e.g. FCNC Z d q = u c t u u d

39 Anomalous magnetic moment of muon Hadronic vacuum polarization (e + e vs τ decay); light by light If real, then SUSY with large tan β and low masses is possibility

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41 Cross section [cm 2 ] (normalised to nucleon) WIMP Mass [GeV] Dark Matter 30% matter, mainly dark No SM candidates; SUSY LSP if R P conserved (MSSM tightly constrained); axions 70% dark energy Higgs VeV, QCD vacuum energy in SM, but too large by ; new fields? quintessence? JDEM (SNAP)

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43 Baryogenesis Baryon asymmetry n B /n γ Possible mechanisms GUT baryogenesis (wiped out by sphalerons for B L=0) Leptogenesis (for heavy right-handed Majorana neutrino in seesaw) Electroweak baryogenesis

44 EB requires strong first order transition, v(t c )/T c > and adequate CP violation in expanding bubble wall q broken phase φ = 0 v Wall unbroken phase q Absent in SM q CP becomes our world Sph Γ B + L _~ 0 CP q Narrow parameter range in MSSM _ q _ q Sph Γ B + L >> H _ q _ q Possible in Z (W. Bernreuther, hep-ph/ )

45 Conclusions Standard Model is spectacularly successful, but has many parameters, tunings, and unexplained features Must be new physics Theoretical ideas Strings Grand Unification (canonical or modified) Supersymmetry Top-down remnants (Z, exotics) Large extra dimensions, deconstruction Dynamical symmetry breaking, compositeness, Little Higgs

46 Experimental probes Hadron colliders: Tevatron, LHC Linear collider/clic FCNC, EDM, heavy quark, precision, neutrino, p decay Cosmology/astrophysics Tremendous opportunities in particle physics, to develop standard theory valid to the Planck scale