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Explore key theoretical predictions for collider searches including hierarchy problems, supersymmetry, little Higgs, and extra dimensions. Discover insights on hierarchy between particles, running from extra dimensions, and unification without desert. Learn about different scenarios, new ingredients from extra dimensions, and collider signals.
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THEORETICALPREDICTIONSFORCOLLIDERSEARCHES G.F. Giudice CERN • “Big” and “little” hierarchy problems • Supersymmetry • Little Higgs • Extra dimensions
HIERARCHY PROBLEM nofine-tuning a LSM < TeV “Big” hierarchy between LSM and MPl Cosmological constant a Cut off of quartic divergences at L<10-3 eV
- + LEP1 Bounds on LLH LLH> 5-10TeV LEP2 MFV LITTLE HIERARCHY
LSM<1 TeV, LLH>5-10 TeV “Little” hierarchy between LSM and LLH a • New physics at LSM is weakly interacting • No (sizable) tree-level contributions from new physics at LSM • Strongly-interacting physics can only occur at scales larger than LLH • Successful new physics at LSM has to pass non-trivial tests
t ~ t dmH2 = + H H SUPERSYMMETRY • can be extended to MPl • Link with quantum gravity • Successful scenario for GUT exp exp Ghilencea-Ross
UNIFICATION WITHOUT DESERT Dienes-Dudas-Gherghetta • Accelerated running from extra dimensions • or from gauge group replication • Different tree-level expression for sin2qW GUT: trace over GUT irrep Little running needed Arkani Hamed-Cohen-Georgi Dimopoulos-Kaplan
SUPERSYMMETRY • Gauge-coupling unification • Radiative EW breaking • Light Higgs • Satisfies “little” hierarchy LLH~4pLSM • Dark matter • Sparticles have not been observed • Susy-breaking sector unspecified
Mc+ > 103.5 GeV Degrassi-Heinemeyer-Hollik-Slavich-Weiglein
Supersymmetry-breaking sector unspecified • Susy flavour violations gauge, gaugino mediation • Connection with gravity _ supergravity, anomaly mediation • problem _ supergravity Predictivity _ gauge, gaugino, anomaly med. Scenarios with different spectra and different experimental signals
NEW INGREDIENTS FROM EXTRA DIMENSIONS y Scherk-Schwarz breaking R Supersymmetryisbroken Non-local susy breaking _ involves global structure At short distances (<R), susy-breaking effects are suppressed
y y R Z2 NEW INGREDIENTS FROM EXTRA DIMENSIONS Orbifold projection Z2 : y g-y cos(ny/R) sin(ny/R) +- n=0 n=1 Chiral theories n=1 n=2 n=2 0 0 pR pR
AN INTERESTING EXAMPLE Barbieri-Hall-Nomura • 5D SUSY SM compactified on S1/(Z2×Z2) • Different susy breaking at each boundary • effective theory non-susy (susy recovered at d<R) • Higgs boson mass (rather) insensitive to UV • mH = 127 ± 10 GeV • Large corrections to Dr ? • UV completion at L ~ 5 TeV ? Barbieri-Hall-Marandella-Nomura-Okui-Oliver-Papucci
Mass spectrum is non-supersymmetric • one Higgs and two sparticles for each SM particle • LSP stable stop with mass 210 GeV
USING WARPED DIMENSIONS Gherghetta-Pomarol • Susy-breaking in Higgs sector is non-local _ finite effects • AdS/CFT _ SM non-susy • Higgs sector: susy bound states of spontaneously broken CFT • Light Higgs & higgsino • New CFT states at L-1 ~ TeV • Considerable fine tuning SM Susy breaking Higgs sector
SUPERSYMMETRY: CONCLUSIONS • Susy at EW scale can be realized in very different ways: • ETmiss • ETmiss + g • ETmiss + ℓ • Stable charged particle • Nearly-degenerate • Stable stop • Partial susy spectrum
HIGGS AS PSEUDOGOLDSTONE BOSON Gauge, Yukawa and self-interaction are large non-derivative couplings _ Violate global symmetry and introduce quadratic div.
ℒ1 ℒ1 ℒ2 H ℒ2 Arkani Hamed-Cohen-Georgi LITTLE HIGGS A less ambitious programme: Explain only little hierarchy At LSM new physics cancels one-loop power divergences “Collective breaking”: many (approximate) global symmetries preserve massless Goldstone boson
It can be achieved with gauge-group replication • Goldstone bosons in • gauged subgroups, each preserving a non-linear global symmetry • which breaks all symmetries • Field replication Ex. SU2 gauge with F1,2doublets such that V(F1+F1,F2+F2) and F1,2 spontaneously break SU2 • Turning off gauge coupling to F1_ • Local SU2(F2) × global SU2(F1) both spont. broken Kaplan-Schmaltz
Realistic models are rather elaborate Effectively, new particles at the scale f ~ LSM canceling (same-spin) SM one-loop divergences with couplings related by symmetry Typical spectrum: Vectorlike charge 2/3 quark Arkani Hamed-Cohen-Georgi-Katz-Nelson-Gregoire-Wacker-Low-Skiba-Smith-Kaplan-Schmaltz-Terning… Gauge bosons EW triplet + singlet Scalars (triplets ?)
Bounds from: Tevatron limits on new gauge bosons EW data (Dr from new gauge and top) Csaki-Hubisz-Kribs-Meade-Terning In minimal model: Variations significantly reduce the fine tuning
Higgs/gauge unification as graviton/photon unification in Kaluza-Klein gauge Higgs HIGGS AS EXTRA-DIM COMPONENT OF GAUGE FIELD AM = (Am,A5), A5g A5 +∂5L forbids m2A52 • Correct Higgs quantum numbers by projecting out unwanted states with orbifold • Yukawa couplings • Quartic couplings • Do not reintroduce quadratic divergences Csaki-Grojean-Murayama Burdman-Nomura Scrucca-Serone-Silvestrini
EXTRA DIMENSIONS Forget about symmetries, about little hierarchy _ cut off at LSM Any short-distance scale < LSM-1 explained by geometry FLAT Arkani Hamed-Dimopoulos-Dvali WARPED Randall-Sundrum
QUANTUM GRAVITY AT LHC Missing energy (flat) Resonances (warped) Graviton emission H Contact interactions (loop dominates over tree if gravity is strong) Higgs-radion mixing
Graviton emission Tree-level graviton exchange Graviton loops Gauge/graviton loop G.G.-Strumia
As s approaches MD, linearized gravity breaks down _ underlying quantum gravity (strings?) TRANSPLANCKIAN REGIME S>>MD_ RS>>lPl and (semi)classicaleffects dominate over quantum-gravity effects √ b > RS b < RS √ Gravitational scattering G.G.-Rattazzi-Wells Black-hole production Giddings-Thomas, Dimopoulos-Landsberg
SM PARTICLES IN EXTRA DIMENSIONS Gauge bosons in 5D: Direct + indirect limits Mc > 6.8 TeV Cheung-Landsberg At LHC up to 13-15 TeV Weaker bounds in universal extra dimensions After compactification, momentum conservation in 5th dim _ KK number conserved KK particles pair produced; no tree-level exchange Mc > 0.3 TeV Appelquist-Cheng-Dobrescu
SUSY GUT EW E CONCLUSIONS • Many open theoretical options for new physics at EW scale • Direct searches + precision measurements _ no existing theory is completely free of fine-tuning Connection with MPl Gauge coupling unification • ~ LLH or LSM _ Need for UV completion at L