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Anticipating New Physics @ the LHC

Anticipating New Physics @ 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, 2007. J. Hewett, Stanford Linear Accelerator Center.

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Anticipating New Physics @ the LHC

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  1. Anticipating New Physics @ 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, 2007 J. Hewett, Stanford Linear Accelerator Center

  2. 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

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

  4. A Cellar of New Ideas a classic! aged to perfection better drink now mature, balanced, well developed - the Wino’s choice ’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 svinters blend all upfront, no finish lacks symmetry bold, peppery, spicy uncertain terrior complex structure young, still tannic needs to develop sleeper of the vintage what a surprise! finely-tuned double the taste J. Hewett

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

  6. TheStandardModelofParticlePhysics Building Blocks of Matter: Symmetry: SU(3)C x SU(2)L x U(1)Y QCD Electroweak Spontaneously Broken to QED This structure is experimentally confirmed!

  7. 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!

  8. Higgs Mass Upper Bound: Gauge Boson Scattering Higgs Higgs Bad violation of unitarity  ~ E2 Restores unitarity Expand cross section into partial waves Unitarity bound (Optical theorem!)  |Re a0| < ½ Gives mH < 1 TeV LHC is designed to explore this entire region!

  9. Present Limits: Direct Searches at LEP: mH > 114.4 GeV Indirect Searches at LEP/SLC: mH < 150-200 GeV @ 95% CL Higgs Z Z Z

  10. Higgs @ the LHC: Production mechanisms & rates Signal determined by final state versus background

  11. Higgs Search Strategies Low: MH < 140 GeV Medium: 130<MH<500 GeV High: MH > ~500 GeV

  12. The Hierarchy Problem Energy (GeV) 1019 Planck Quantum Corrections: Virtual Effects drag Weak Scale to MPl 1016 GUT desert Future Collider Energies mH2 ~ ~ MPl2 103 Weak All of known physics Solar System Gravity 10-18

  13. The Hierarchy Problem: Supersymmetry Energy (GeV) 1019 Planck Quantum Corrections: Virtual Effects drag Weak Scale to MPl 1016 GUT desert boson Future Collider Energies mH2 ~ ~ MPl2 103 Weak fermion ~ - MPl2 mH2 ~ All of known physics Large virtual effects cancel order by order in perturbation theory Solar System Gravity 10-18

  14. 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)

  15. Supersymmetry at the LHC SUSY discovery generally ‘easy’ at LHC Cut: ETmiss > 300 GeV

  16. LHC Supersymmetry Discovery Reach Model where gravity mediates SUSY breaking – 5 free parameters at high energies Squark and Gluino mass reach is 2.5-3.0 TeV @ 300 fb-1

  17. MSSM only viable for mh < 135 GeV Carena, Haber hep-ph/0208209

  18. MSSM: tension with fine-tuning Competing factors: • Mass of lightest higgs mh < MZ 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

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

  20. Dark Matter in Supersymmetry • 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 Mass of Dark Matter Particle from Supersymmetry (TeV) m2 ΩCDM h2 ~ (1 TeV)2 Fraction of total Dark Matter density

  21. Determination of Dark Matter Density @ LHC • Measure SUSY properties @ LHC • Benchmark point SPS1a • Dependence on Stau mass determination Baltz, Battaglia, Peskin, Wizansky hep-ph/0602187

  22. The Hierarchy Problem: Extra Dimensions Energy (GeV) 1019 Planck Simplest Model: Large Extra Dimensions 1016 GUT desert Future Collider Energies 103 Weak – Quantum Gravity = Fundamental scale in 4 +  dimensions MPl2 = (Volume) MD2+ Gravity propagates in D = 3+1 +  dimensions All of known physics Solar System Gravity 10-18 Arkani-Hamed, Dimopoulis, Dvali

  23. LHC 102 10 1 10-1 10-2 Events / 50 GeV / 100 fb-1 Mee [GeV] Kaluza-Klein Modes in a Detector Indirect Signature Missing Energy Signature pp  g + Gn JLH Vacavant, Hinchliffe

  24. Graviton Exchange Modified with Running Gravitational Coupling Insert Form Factor in coupling to parameterize running M*D-2 [1+q2/t2M*2 ]-1 Could reduce signal! t= 1 SM 0.5 D=3+4 M* = 4 TeV JLH, Rizzo, to appear

  25. Black Hole Production @ LHC: Dimopoulos, Landsberg Giddings, Thomas Black Holes produced when s > M* Classical Approximation: [space curvature << E] E/2 b < Rs(E)  BH forms b E/2 Geometric Considerations: Naïve = Rs2(E), details show this holds up to a factor of a few

  26. Production rate is enormous! Determination of Number of Large Extra Dimensions 1 per sec at LHC! JLH, Lillie, Rizzo hep-ph/0503178

  27. Black Hole event simulation @ LHC

  28. The Hierarchy Problem: Extra Dimensions Energy (GeV) 1019 Planck Model II: Warped Extra Dimensions 1016 GUT strong curvature desert Future Collider Energies 103 Weak wk = MPl e-kr All of known physics Solar System Gravity 10-18 Randall, Sundrum

  29. Kaluza-Klein Modes in a Detector: SM on the brane Number of Events in Drell-Yan For this same model embedded in a string theory: AdS5 x S Davoudiasl, JLH, Rizzo

  30. 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  gn  tt gg  Gn  ZZ Lillie, Randall, Wang, hep-ph/0701164 Agashe, Davoudiasl, Perez, Soni hep-ph/0701186

  31. Issue: Top Collimation - gg  gn  tt g1 = 4 TeV g1 = 2 TeV Lillie, Randall, Wang, hep-ph/0701164

  32. The Hierarchy Problem: Little Higgs Energy (GeV) 1019 Planck Little Hierarchies! 1016 GUT desert New Physics! 104 Future Collider Energies Simplest Model: The Littlest Higgs with  ~ 10 TeV No UV completion 103 Weak All of known physics Solar System Gravity 10-18 Arkani-Hamed, Cohen, Katz, Nelson

  33. The Hierarchy Problem: Little Higgs Energy (GeV) 1019 Planck Stacks of Little Hierarchies 1016 GUT . . . 106 New Physics! 105 New Physics! New Physics! 104 Future Collider Energies Simplest Model: The Littlest Higgs with 1 ~ 10 TeV 2 ~ 100 TeV 3 ~ 1000 TeV ….. 103 Weak All of known physics Solar System Gravity 10-18

  34. 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  mh2 ~ ,  > 10 TeV, @ 2-loops! (162)2

  35. 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

  36. Little Higgs Gauge Production WZ  WH  WZ  2j + 3l +  Azuelos etal, hep-ph/0402037 Birkedal, Matchev, Perelstein, hep-ph/0412278

  37. The Hierarchy Problem: Higgsless Energy (GeV) 1019 Planck Warped Extra Dimensions 1016 GUT strong curvature desert Future Collider Energies 103 Weak wk = MPl e-kr With NO Higgs boson! All of known physics Solar System Gravity 10-18 Csaki, Grojean,Murayama, Pilo, Terning

  38. 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 BC’s restricted by variation of the action at boundary TeV-brane SU(2)L x SU(2)R SU(2) Custodial Symmetry is preserved! SU(2)D SU(2)R x U(1)B-L W, Z get TeV scale masses  left massless! U(1)Y WR, ZR get Planck scale masses

  39. Unitarity in Gauge Boson Scattering: What do we do without a Higgs? Exchange gauge KK towers: Conditions on KK masses & couplings: (g1111)2 = k (g11k)2 4(g1111)2 M12 = k (g11k)2 Mk2 Csaki etal, hep-ph/0305237 Necessary, but not sufficient, to guarantee perturbative unitarity!

  40. Production of Gauge KK States @ LHC - gg, qq  g1  dijets Davoudiasl, JLH, Lilllie, Rizzo Balyaev, Christensen

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

  42. Split Supersymmetry: Arkani-Hamed, Dimopoulis hep-ph/0405159 Giudice, Romanino hep-ph/0406088 Energy (GeV) MGUT ~ 1016 GeV MS : SUSY broken at high scale ~ 109-13 GeV Scalars receive mass @ high scale Mweak 1 light Higgs + Fermions protected by chiral symmetry

  43. Collider Phenomenology: Gluinos • Pair produced via strong interactions as usual • Gluinos are long-lived • No MET signature • Form R-hadrons q Gluino pair + jet cross section 10 ~ q ~ g q 100 fb-1 Rate ~ 0, due to heavy squark masses! JLH, Lillie, Masip, Rizzo hep-ph/0408248

  44. Density of Stopped Gluinos in ATLAS Arvanitaki, etal hep-ph/0506242 See also ATLAS study, Kraan etal hep-ph/0511014

  45. 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!

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

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

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