Anticipating New the LHC Why the Terascale? Scenarios for Electroweak Symmetry Breaking and the Gauge Hierarchy –LHC Signatures –Connection to Dark Matter Summary: Discoveries are only months away! APS April Meeting, 2007J. Hewett, Stanford Linear Accelerator Center

Why the Terascale? Electroweak Symmetry breaks at energies ~ 1 TeV (Higgs or ???) Gauge Hierarchy: Nature is fine-tuned or Higgs mass must be stabilized by New Physics ~ 1 TeV Dark Matter: Weakly Interacting Massive Particle must have mass ~ 1 TeV to reproduce observed DM density

The LHC is turning on! The anticipation has fueled many ideas!

A Cellar of New Ideas ’67 The Standard Model ’77 Vin de Technicolor ’70’s Supersymmetry: MSSM ’90’s-now SUSY Beyond MSSM ’90’s CP Violating Higgs ’98 Extra Dimensions ’02 Little Higgs ’03 Fat Higgs ’03 Higgsless ’04 Split Supersymmetry ’05 Twin Higgs a classic! aged to perfection better drink now mature, balanced, well developed - the Wino’s choice complex structure sleeper of the vintage what a surprise! svinters blend all upfront, no finish lacks symmetry young, still tannic needs to develop bold, peppery, spicy uncertain terrior J. Hewett finely-tuned double the taste

Discoveries at the LHC will find the vintage nature has bottled.

The Standard Model of Particle Physics Symmetry: SU(3) C x SU(2) L x U(1) Y Building Blocks of Matter: QCDElectroweak Spontaneously Broken to QED This structure is experimentally confirmed!

The Standard Model Higgs Boson Economy: 1 scalar doublet Higgs Potential: V(  ) =  2  2 /2 +  4 /4 Spontaneous Symmetry Breaking Chooses a vacuum v =  0|  |0  and shifts the field  =  - v V(  ) = m  2  2 /2 + v  3 +  4 /4 gives 1 physical Higgs scalar with m  =  2 v Masses of electroweak gauge bosons proportional to v We need to discover the Higgs and experimentally test this potential and the Higgs properties!

Higgs Mass Upper Bound: Gauge Boson Scattering Higgs Bad violation of unitarity  ~ E 2 Restores unitarity Expand cross section into partial waves Unitarity bound (Optical theorem!)  |Re a 0 | < ½ Gives m H < 1 TeV LHC is designed to explore this entire region!

Present Limits: Direct Searches at LEP: m H > GeV Indirect Searches at LEP/SLC: m H < % CL ZZ Higgs Z

the LHC: Production mechanisms & rates Signal determined by final state versus background

Higgs Search Strategies Low: M H < 140 GeVMedium: 130<M H <500 GeVHigh: M H > ~500 GeV

The Hierarchy Problem Energy (GeV) Solar System Gravity Weak GUT Planck desert Future Collider Energies All of known physics  m H 2 ~~ M Pl 2 Quantum Corrections: Virtual Effects drag Weak Scale to M Pl

The Hierarchy Problem: Supersymmetry Energy (GeV) Solar System Gravity Weak GUT Planck desert Future Collider Energies All of known physics  m H 2 ~~ M Pl 2 Quantum Corrections: Virtual Effects drag Weak Scale to M Pl  m H 2 ~ ~ - M Pl 2 boson fermion Large virtual effects cancel order by order in perturbation theory

Supersymmetry : Symmetry between fermions and bosons Predicts that every particle has a superpartner of equal mass (  SUSY is broken: many competing models!) Suppresses quantum effects Can make quantum mechanics consistent with gravity (with other ingredients)

Supersymmetry at the LHC SUSY discovery generally ‘easy’ at LHC Cut: E T miss > 300 GeV

LHC Supersymmetry Discovery Reach Model where gravity mediates SUSY breaking – 5 free parameters at high energies Squark and Gluino mass reach is fb -1

MSSM only viable for m h < 135 GeV Carena, Haber hep-ph/

MSSM: tension with fine-tuning Competing factors: –Mass of lightest higgs m h < M Z at tree-level large quantum corrections from top sector If stop mass ~ 1 TeV –Stability of Higgs mass stops cut-off top contribution to quadratic divergence  stops can’t be too heavy –Z mass relationship < (130 GeV) 2

Resolve Fine-Tuning: Extend the MSSM NMSSM (Next-to Minimal SSM) –Add a Higgs Singlet - Evade LEP bounds – minimize fine-tuning! - Regions where Higgs discovery is LHC MNMSSM (Minimally Non-minimal MSSM) –Lightest higgs < 145 GeV LHC Gauge Extensions of MSSM –M h < 250 (350) GeV Split Supersymmetry Dermisek, Gunion, … Batra, Delgado, Kaplan, Tait Panagiotakopoulos, Pilaftis

A component of Dark Matter could be the Lightest Neutralino of Supersymmetry - stable and neutral with mass ~ 0.1 – 1 TeV In this case, electroweak strength annihilation gives relic density of m 2 Ω CDM h 2 ~ (1 TeV) 2 Dark Matter in Supersymmetry Mass of Dark Matter Particle from Supersymmetry (TeV) Fraction of total Dark Matter density

Determination of Dark Matter LHC Measure SUSY LHC Benchmark point SPS1a Dependence on Stau mass determination Baltz, Battaglia, Peskin, Wizansky hep-ph/

The Hierarchy Problem: Extra Dimensions Energy (GeV) Solar System Gravity Weak – Quantum Gravity GUT Planck desert Future Collider Energies All of known physics Simplest Model: Large Extra Dimensions = Fundamental scale in 4 +  dimensions M Pl 2 = (Volume)  M D 2+  Gravity propagates in D =  dimensions Arkani-Hamed, Dimopoulis, Dvali

Kaluza-Klein Modes in a Detector M ee [GeV] Events / 50 GeV / 100 fb LHC Indirect SignatureMissing Energy Signature pp  g + G n JLHVacavant, Hinchliffe

Graviton Exchange Modified with Running Gravitational Coupling Insert Form Factor in coupling to parameterize running M * D-2 [1+q 2 /t 2 M * 2 ] -1 Could reduce signal! D=3+4 M * = 4 TeV SM t=  JLH, Rizzo, to appear

Black Hole LHC: Black Holes produced when  s > M * Classical Approximation: [space curvature << E] E/2 b b < R s (E)  BH forms Geometric Considerations:  Naïve =  R s 2 (E), details show this holds up to a factor of a few Dimopoulos, Landsberg Giddings, Thomas

Production rate is enormous! 1 per sec at LHC! JLH, Lillie, Rizzo hep-ph/ Determination of Number of Large Extra Dimensions

Black Hole event LHC

The Hierarchy Problem: Extra Dimensions Energy (GeV) Solar System Gravity Weak GUT Planck desert Future Collider Energies All of known physics Model II: Warped Extra Dimensions  wk = M Pl e -kr  strong curvature Randall, Sundrum

Number of Events in Drell-Yan For this same model embedded in a string theory: AdS 5 x S  Kaluza-Klein Modes in a Detector: SM on the brane Davoudiasl, JLH, Rizzo

Kaluza-Klein Modes in a Detector: SM off the brane Fermion wavefunctions in the bulk: decreased couplings to light fermions for gauge & graviton KK states gg  G n  ZZ gg  g n  tt Agashe, Davoudiasl, Perez, Soni hep-ph/ Lillie, Randall, Wang, hep-ph/

Issue: Top Collimation Lillie, Randall, Wang, hep-ph/ gg  g n  tt - g 1 = 2 TeV g 1 = 4 TeV

The Hierarchy Problem: Little Higgs Energy (GeV) Solar System Gravity Weak GUT Planck desert Future Collider Energies All of known physics Little Hierarchies! 10 4 New Physics! Simplest Model: The Littlest Higgs with  ~ 10 TeV No UV completion Arkani-Hamed, Cohen, Katz, Nelson

The Hierarchy Problem: Little Higgs Energy (GeV) Solar System Gravity Weak GUT Planck Future Collider Energies All of known physics Stacks of Little Hierarchies 10 4 New Physics! Simplest Model: The Littlest Higgs with  1 ~ 10 TeV  2 ~ 100 TeV  3 ~ 1000 TeV … New Physics!

Little Higgs: The Basics The Higgs becomes a component of a larger multiplet of scalars,   transforms non-linearly under a new global symmetry New global symmetry undergoes SSB  leaves Higgs as goldstone Part of global symmetry is gauged  Higgs is pseudo-goldstone Careful gauging removes Higgs 1-loop divergences  2  m h 2 ~,  > 10 2-loops! (16  2 ) 2

3-Scale Model  > 10 TeV: New Strong Dynamics Global Symmetry f ~  /4  ~ TeV: Symmetires Broken Pseudo-Goldstone Scalars New Gauge Fields New Fermions v ~ f/4  ~ 100 GeV: Light Higgs SM vector bosons & fermions Sample Spectrum

Little Higgs Gauge Production Azuelos etal, hep-ph/ Birkedal, Matchev, Perelstein, hep-ph/ WZ  W H  WZ  2j + 3l +

The Hierarchy Problem: Higgsless Energy (GeV) Solar System Gravity Weak GUT Planck desert Future Collider Energies All of known physics Warped Extra Dimensions  wk = M Pl e -kr  With NO Higgs boson! strong curvature Csaki, Grojean,Murayama, Pilo, Terning

Framework: EW Symmetry Broken by Boundary Conditions SU(2) L x SU(2) R x U(1) B-L in 5-d Warped bulk Planck brane TeV-brane SU(2) R x U(1) B-L U(1) Y SU(2) L x SU(2) R SU(2) D SU(2) Custodial Symmetry is preserved! W R , Z R get Planck scale masses W , Z get TeV scale masses  left massless! BC’s restricted by variation of the action at boundary

Exchange gauge KK towers: Conditions on KK masses & couplings: (g 1111 ) 2 =  k (g 11k ) 2 4(g 1111 ) 2 M 1 2 =  k (g 11k ) 2 M k 2 Necessary, but not sufficient, to guarantee perturbative unitarity! Csaki etal, hep-ph/ Unitarity in Gauge Boson Scattering: What do we do without a Higgs?

Production of Gauge KK LHC gg, qq  g 1  dijets - Davoudiasl, JLH, Lilllie, RizzoBalyaev, Christensen

Gauge Hierarchy Problem Cosmological Constant Problem Planck Scale Weak Scale Cosmological Scale The Hierarchy Problem: Who Cares!! We have much bigger Problems!

Split Supersymmetry : Energy (GeV) M GUT ~ GeV M S : SUSY broken at high scale ~ GeV M weak 1 light Higgs + Fermions protected by chiral symmetry Scalars receive high scale Arkani-Hamed, Dimopoulis hep-ph/ Giudice, Romanino hep-ph/

Collider Phenomenology: Gluinos Pair produced via strong interactions as usual Gluinos are long-lived No MET signature Form R-hadrons g ~ q ~ q q 1010 Rate ~ 0, due to heavy squark masses! Gluino pair + jet cross section JLH, Lillie, Masip, Rizzo hep-ph/ fb -1

Density of Stopped Gluinos in ATLAS See also ATLAS study, Kraan etal hep-ph/ Arvanitaki, etal hep-ph/

This is a Special Time in Particle Physics Urgent Questions Provocative discoveries lead to urgent questions Connections Questions seem to be related in fundamental, yet mysterious, ways Tools We have the experimental tools, technologies, and strategies to tackle these questions We are witnessing a Scientific Revolution in the Making!

The LHC is Turning On!!!!!!!! And we are ready!

Higgs Coupling LHC Observed Channels: –gg  H  ZZ, WW,  –qqH  qqZZ, qqWW, qq , qq  –WH  WWW, W  ; ZH  Z  –ttH, with H  WW, , bb Duhrssen, Heinemeyer, Logan, Rainwater, Weiglein, Zeppenfeld Employ Narrow Width Approx:  (H) SM  p  x  (H) B(H  xx) =  p SM  tot Theoretical Assumption:  V   V SM, V=W,Z