Weak Interactions and Neutrinos in the LHC Era

Transcription

1 Weak Interactions and Neutrinos in the LHC Era The standard model Testing the standard model Problems Beyond the standard model Where are we going?

2 The New Standard Model Standard model, Majorana): supplemented with neutrino mass (Dirac or SU(3) SU(2) U(1) classical relativity Mathematically consistent field theory of strong, weak, electromagnetic interactions Gauge interactions correct to first approximation 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 )

4 Quantum Chromodynamics (QCD) Quantum Chromodynamics (QCD) Modern theory of the strong interactions Modern theory of the strong interactions Quark model/ color/ confinement Low energy symmetries (+ realization, breaking) (SU(3) L SU(3) R ) Hadronic models: Yukawa, Regge, dual resonance ( strings) x f(x) Asymptotic freedom (weak coupling at high energy) x Yoichiro WIN 05 Nambu (June Symposium 11, 2005) (April 21, 2005) Paul Langacker (Penn)

5 Relation of running α s at different scales Average Hadronic Jets e + e - rates Photo-production 0.3 ep event shapes Polarized DIS Fragmentation Z width! s (µ) 0.2 Deep Inelastic Scattering (DIS) Spectroscopy (Lattice)! decays 0.1 " decay # s (M Z ) µ GeV

6 Quantum Electrodynamics Experiment Value of α 1 Difference from α 1 (ae) Deviation from gyromagnetic (52) [ ] ratio, ae = (g 2)/2 for e ac Josephson effect (51) [ ] (0.116 ± 0.051) 10 4 h/mn (mn is the neutron mass) (51) [ ] ( ± 0.051) 10 4 from n beam Hyperfine structure in (83) [ ] (0.064 ± 0.083) 10 4 muonium, µ + e Cesium D 1 line (41) [ ] (0.072 ± 0.041) 10 4

7 The Electroweak Theory QED and weak charged current unified Weak neutral current predicted Stringent tests of wnc, Z-pole and beyond Fermion gauge and gauge self interactions

8 LEP combined: e + e! " hadrons(#) 10 LEP1 $s % / % s % > 0.10 LEP2 $s % / % s % > 0.10 LEP2 $s % / % s % > 0.85 & hadron [nb] $s % [GeV]

9 Measurement Fit O meas O fit /σ meas Δα (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] ±

10 6 5 Theory uncertainty Δα had = Δα (5) ± SM correct and unique to zeroth approx. (gauge principle, group, representations) Δχ ± incl. low Q 2 data SM correct at loop level (renorm gauge theory; m t, α s, M H ) TeV physics severely constrained (unification vs compositeness) 1 0 Excluded m H [GeV] Preliminary Consistent with light elementary Higgs Precise gauge couplings (gauge unification)

11 Heavy B decays and CP violation 1.5 excluded area has CL < 0.05 CKM (quark mixing) CP breaking 1 sin 2β Δm d Unitarity triangle Search for new physics Anomalies in electroweak penguins? η ε K V ub /V cb γ α β B ρρ Δm s & Δm d Baryogenesis? -0.5 ε K -1 C K M f i t t e r Winter 2004 B ρρ ρ Yoichiro Nambu Symposium (April 21, 2005)

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

13 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? Probe of Planck/GUT scale? CP violation inadequate to explain baryon asymmetry Possible solutions: strings; brane worlds; family symmetries; compositeness; radiative hierarchies. New sources of CP violation.

14 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; anthropically motivated finetuning (split supersymmetry) (landscape) 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

15 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? Anthropically motivated fine-tuning (landscape)?

16 Necessary new ingredients Mechanism for small neutrino masses Planck/GUT scale? Mechanism for baryon asymmetry? Electroweak transition (Z or extended Higgs?) Heavy Majorana neutrino decay (seesaw)? Decay of coherent field? CPT violation?

17 What is the dark energy? Cosmological Constant? Quintessence? Related to inflation? Time variation of couplings? What is the dark matter? Lightest supersymmetric particle? Axion? Suppression of flavor changing neutral currents? Proton decay? Electric dipole moments? Automatic in standard model, but not in extensions

18 Beyond the Standard Model The Whimper: A new layer at the TeV scale The Hybrid: low fundamental scale/large extra dimensions The Bang: unification at the Planck scale, M P = G 1/2 N GeV

19 Typical Model scale (GeV) Motivation New W s, Zs, fermions, Higgs Remnant of something else Family symmetry Fermion (No compelling models) Composite fermions Fermion (No compelling models) Composite Higgs Higgs (No compelling models) Composite W, Z (G, γ?) Higgs (No compelling models) Little Higgs Higgs Large extra dimensions (d > 4) Higgs, graviton New global symmetry Strong CP Kaluza Klein Graviton Higgs (0) gauge (1) Graviton (2) (d > 4) Grand unification Gauge Strong electroweak Supersymmetry/supergravity Higgs, graviton Fermion boson

20 Compositeness Onion-like layers Composite fermions, scalars (dynamical sym. breaking) Not like to atom nucleus +e p + n quark Other new TeV layer: Little Higgs At most one more layer accessible (Tevatron, LHC, ILC) Rare decays (e.g., K µe) Typically, few % effects at LEP/SLC, WNC (challenge for models) anomalous V V V, new particles, future W W W W, FCNC, EDM

21 Large extra dimensions (deconstruction, brane worlds) Can be motivated by strings, but new dimensions much larger than cm M 1 P Fundamental scale M F TeV M P l = 1/ 8πG N GeV Assume δ extra dimensions with volume V δ M δ F M 2 P l = M 2+δ F V δ M 2 F (Introduces new hierarchy problem)

22 Black holes, graviton emission at colliders! Macroscopic gravity effects Astrophysics

23 Unification Unification of interactions Grand desert to unification (GUT) or Planck scale Elementary Higgs, supersymmetry (SUSY), GUTs, strings Possibility of probing to M P and very early universe

24 Supersymmetry Fermion boson symmetry Motivations stabilize weak scale M SUSY < O(1 TeV) (but recent high scale ideas) supergravity (gauged supersymmetry): unification of gravity (non-renormalizable) coupling constants in supersymmetric grand unification decoupling of heavy particles (precision)

25 Consequences 1000 additional charged and neutral Higgs particles 500 Γ Z, σ had, R l, R q asymmetries ν scattering M W m t M 2 H 0 < cos 2 2βM 2 Z + H.O.T. (O(m 4 t )) < (150 GeV)2, consistent with LEP cf., standard model: M H 0 < 1000 GeV M H [GeV] excluded all data 90% CL m t [GeV]

26 800 m [GeV] 700 Superpartners H 0, A 0 H ± ll ν l lr h 0 τ 2 τ 1 χ 0 χ χ 0 2 χ 0 1 χ ± 2 χ ± 1 g ũ L, d R ũ R, d L t 2 b2 b1 t 1 q q, scalar quark l l, scalar lepton W w, wino typical scale: several hundred GeV LSP: cold dark matter candidate SUSY breaking large m t May be large FCNC, EDM, (g µ 2)

27 Grand Unification Unify strong SU(3) and electroweak SU(2) U(1) in simple group, broken at GeV! i -1(µ) ! 1! 2 SM World Average! 3! S (M Z )=0.117±0.005 Gauge unification (only in supersymmetric version)! i -1(µ) sin 2 " =0.2317± MS µ (GeV) 68% CL! 1! 2 MSSM World Average 20! U.A. W.d.B H.F µ (GeV)

28 Seesaw model for small m ν why are mixings large?) (but Quark-lepton (q l) unification ( charge quantization) q l mass relations (work only for third family in simplest versions) Proton decay? excluded) Doublet-triplet problem? (simplest versions String embedding? (breaking, families may be entangled in extra dimensions) p " e + # 0 e + $ e + ' e + & 0 e + K 0 µ + # 0 µ + $ µ + ' µ + & 0 µ + K 0 + % # % & + + % K n " e + # - e + & - µ + # - µ + & - # 0 % % % % % $ ' & 0 K 0 KAM IMB3 SK Soudan lifetime limit (years)

29 Superstrings Finite, parameter-free theory of everything (TOE), including quantum gravity 1-d string-like object Appears pointlike for resolution > M 1 P cm Vibrational modes particles Consistent in 10 spacetime dimensions 6 must compactify to scale M 1 P 4-dim supersymmetric gauge theory below M P May also be solitons (branes), terminating open strings

30 Problems Which compactification manifold? Supersymmetry breaking? Cosmological constant? Many moduli (vacua). Landscape ideas - is there any predictability left? Relation to supersymmetric standard model, GUT? Need theoretical progress and hints from experiment TeV scale remnants, such as Z, extended Higgs, exotics SUSY breaking patterns Need very precise masses and couplings International Linear Collider

31 Future/present Experiments High energy colliders: the primary tool The TEVATRON; Fermilab, 1.96 TeV pp, exploration The Large Hadron Collider (LHC); CERN, 14 TeV pp, high luminosity, discovery (Discovery machine for supersymmetry, R p violation, string remnants (e.g., Z, exotics); or compositeness, dynamical symmetry breaking, Higgless theories, Little Higgs, large extra dimensions, ) The International Linear Collider (ILC), in planning; 500 GeV-1 TeV e + e, cold technology, high precision studies (Precision parameters to map back to string scale) Also, CP violation (B decays, electric dipole moments), flavor changing neutral currents (e.g., µ eγ, µn en, B φk s ), neutrino physics

32 Neutrinos as a Unique Probe: cm Particle Physics νn, µn, en scattering: existence/ properties of quarks, QCD Weak decays (n pe ν e, µ e ν µ ν e ): Fermi theory, parity violation, mixing Neutral current, Z-pole, atomic parity: electroweak unification, field theory, m t ; severe constraint on physics to TeV scale Neutrino mass: constraint on TeV physics, grand unification, superstrings, extra dimensions; seesaw: m ν m 2 q /M GUT

33 Solar/atmospheric neutrino experiments Neutrinos have tiny masses (but large mixings) Standard Solar model confirmed First oscillation dips observed! (QM on large scale) Data/Prediction (null osc.) L/E (km/gev)

34 3 ν Patterns Solar: LMA (SNO, KamLAND) m ev 2, nonmaximal Atmospheric: m 2 Atm ev 2, near-maximal mixing Reactor: U e3 small

35 Neutrino Implications/questions Key constituent of the Universe Why are the masses so small? Planck/GUT scale? e.g., seesaw or generalization, m ν m 2 D /M N (may not be generic in strings) ν L h N R Dirac v = φ m D = hv ν L ν c R ν L ν L Majorana Are the neutrinos Dirac or Majorana? No SM gauge symmetry forbids Majorana (but string, extended?) Neutrinoless double beta decay (ββ 0ν ) (inverted or degenerate spectra)

36 What is the spectrum: number, mass scale/pattern, mixings Scale: β decay (KATRIN), ββ 0ν, large scale structure (SDSS) Mixings and CP: reactor, long baseline oscillation experiments, Solar Pattern: long baseline, ββ 0ν, supernova Number: LSND? MiniBooNE normal inverted degenerate Leptogenesis? Relic neutrinos? Indirect: Nucleosynthesis, large scale structure. Direct? (Zburst?)

37 The Universe The concordance 5% matter (including dark baryons): CMB, BBN, Lyman α 25% dark matter (galaxies, clusters, CMB, lensing) 70% dark energy (Acceleration (Supernovae), CMB (WMAP))

38 What is the dark energy? Vacuum energy (cosmological constant); time varying field (quintessence)? High precision supernova survey (SNAP); CMB (Planck) Expansion History of the Universe 1.5 Perlmutter, Physics Today (2003) relative brightness expands forever collapses Scale of the Universe Relative to Today's Scale After inflation, the expansion either first decelerated, then accelerated past...or always decelerated today future 10 redshift Billions Years from Today

39 What is the dark matter? Cross section [cm 2 ] (normalised to nucleon) WIMP Mass [GeV] Lightest neutralino in supersymmetry (if R parity conserved)? Axion? Direct searches: LHC, ILC; cold dark matter searches; high energy annihilation ν s Axion searches (resonant cavities) Gravitation lensing (SNAP), CMB (Planck)

40 Why is there matter and not antimatter? n B /n γ 10 10, n B 0 Electroweak baryogenesis (extensions of MSSM)? Leptogenesis? Decay of heavy fields? violation? CP T v Wall q q broken phase φ = 0 becomes our world unbroken phase q q CP Sph Γ B + L _~ 0 CP _ q _ q _ q _ q Sph Γ B + L >> H

41 fields? CP T violation? The very beginning (inflation) The New Standard Model Relation to particle physics, strings, Λ? CMB (Planck); gravity waves (LISA) Standard model, supplemented with neutrino mass (Dirac or Majorana): SU (3) SU (2) U (1) classical relativity Mathematically consistent NYS APS (October 15, 2004) electromagnetic interactions field theory of strong, weak, Gauge interactions correct to first approximation to cm Complicated, free parameters, fine tunings must be new physics

42 Far-Out Stuff LIV, VEP (e.g., maximum speeds, decays, (oscillations) of HE γ, e, gravity waves (ν s)) LED, TeV black holes Time varying couplings (Murphy et al, astro-ph/ )

43 Conclusions The standard model is the correct description of fermions/gauge bosons down to cm 1 1 TeV EWSB: consistent with light elementary Higgs but not proved Standard model is complicated must be new physics Precision tests severely constrain new TeV-scale physics Promising theoretical ideas at Planck scale Promising experimental program at colliders, accelerators, low energy, cosmology Challenge to make contact between theory and experiment